20.2: Structure and Function of Blood Vessels
By the end of this section, you will be able to:
- Compare and contrast the three tunics that make up the walls of most blood vessels
- Distinguish between elastic arteries, muscular arteries, and arterioles on the basis of structure, location, and function
- Describe the basic structure of a capillary bed, from the supplying metarteriole to the venule into which it drains
- Explain the structure and function of venous valves in the large veins of the extremities
Blood is carried through the body via blood vessels. An artery is a blood vessel that carries blood away from the heart, where it branches into ever-smaller vessels. Eventually, the smallest arteries, vessels called arterioles, further branch into tiny capillaries, where nutrients and wastes are exchanged, and then combine with other vessels that exit capillaries to form venules, small blood vessels that carry blood to a vein, a larger blood vessel that returns blood to the heart.
Arteries and veins transport blood in two distinct circuits: the systemic circuit and the pulmonary circuit (Figure Figure \(\PageIndex{1}\)). Systemic arteries provide blood rich in oxygen to the body’s tissues. The blood returned to the heart through systemic veins has less oxygen, since much of the oxygen carried by the arteries has been delivered to the cells. In contrast, in the pulmonary circuit, arteries carry blood low in oxygen exclusively to the lungs for gas exchange. Pulmonary veins then return freshly oxygenated blood from the lungs to the heart to be pumped back out into systemic circulation. Although arteries and veins differ structurally and functionally, they share certain features.
Shared Structures
Different types of blood vessels vary slightly in their structures, but they share the same general features. Arteries and arterioles have thicker walls than veins and venules because they are closer to the heart and receive blood that is surging at a far greater pressure (Figure \(\PageIndex{2}\)). Each type of vessel has a lumen —a hollow passageway through which blood flows. Arteries have smaller lumens than veins, a characteristic that helps to maintain the pressure of blood moving through the system. Together, their thicker walls and smaller diameters give arterial lumens a more rounded appearance in cross section than the lumens of veins.
By the time blood has passed through capillaries and entered venules, the pressure initially exerted upon it by heart contractions has diminished. In other words, in comparison to arteries, venules and veins withstand a much lower pressure from the blood that flows through them. Their walls are considerably thinner and their lumens are correspondingly larger in diameter, allowing more blood to flow with less vessel resistance. In addition, many veins of the body, particularly those of the limbs, contain valves that assist the unidirectional flow of blood toward the heart. This is critical because blood flow becomes sluggish in the extremities, as a result of the lower pressure and the effects of gravity.
The walls of arteries and veins are largely composed of living cells and their products (including collagenous and elastic fibers); the cells require nourishment and produce waste. Since blood passes through the larger vessels relatively quickly, there is limited opportunity for blood in the lumen of the vessel to provide nourishment to or remove waste from the vessel’s cells. Further, the walls of the larger vessels are too thick for nutrients to diffuse through to all of the cells. Larger arteries and veins contain small blood vessels within their walls known as the vasa vasorum —literally “vessels of the vessel”—to provide them with this critical exchange. Since the pressure within arteries is relatively high, the vasa vasorum must function in the outer layers of the vessel (see Figure 20.3) or the pressure exerted by the blood passing through the vessel would collapse it, preventing any exchange from occurring. The lower pressure within veins allows the vasa vasorum to be located closer to the lumen. The restriction of the vasa vasorum to the outer layers of arteries is thought to be one reason that arterial diseases are more common than venous diseases, since its location makes it more difficult to nourish the cells of the arteries and remove waste products. There are also minute nerves within the walls of both types of vessels that control the contraction and dilation of smooth muscle. These minute nerves are known as the nervi vasorum.
Both arteries and veins have the same three distinct tissue layers, called tunics (from the Latin term tunica), for the garments first worn by ancient Romans; the term tunic is also used for some modern garments. From the most interior layer to the outer, these tunics are the tunica intima, the tunica media, and the tunica externa (see Figure \(\PageIndex{2}\)). Table \(\PageIndex{1}\) compares and contrasts the tunics of the arteries and veins.
| Arteries | Veins | |
|---|---|---|
| General appearance |
Thick walls with small lumens
Generally appear rounded |
Thin walls with large lumens
Generally appear flattened |
| Tunica intima |
Endothelium usually appears wavy due to constriction of smooth muscle
Internal elastic membrane present in larger vessels |
Endothelium appears smooth
Internal elastic membrane absent |
| Tunica media |
Normally the thickest layer in arteries
Smooth muscle cells and elastic fibers predominate (the proportions of these vary with distance from the heart) External elastic membrane present in larger vessels |
Normally thinner than the tunica externa
Smooth muscle cells and collagenous fibers predominate Nervi vasorum and vasa vasorum present External elastic membrane absent |
| Tunica externa |
Normally thinner than the tunica media in all but the largest arteries
Collagenous and elastic fibers Nervi vasorum and vasa vasorum present |
Normally the thickest layer in veins
Collagenous and smooth fibers predominate Some smooth muscle fibers Nervi vasorum and vasa vasorum present |
Tunica Intima
The tunica intima (also called the tunica interna) is composed of epithelial and connective tissue layers. Lining the tunica intima is the specialized simple squamous epithelium called the endothelium, which is continuous throughout the entire vascular system, including the lining of the chambers of the heart. Damage to this endothelial lining and exposure of blood to the collagenous fibers beneath is one of the primary causes of clot formation. Until recently, the endothelium was viewed simply as the boundary between the blood in the lumen and the walls of the vessels. Recent studies, however, have shown that it is physiologically critical to such activities as helping to regulate capillary exchange and altering blood flow. The endothelium releases local chemicals called endothelins that can constrict the smooth muscle within the walls of the vessel to increase blood pressure. Uncompensated overproduction of endothelins may contribute to hypertension (high blood pressure) and cardiovascular disease.
Next to the endothelium is the basement membrane, or basal lamina, that effectively binds the endothelium to the connective tissue. The basement membrane provides strength while maintaining flexibility, and it is permeable, allowing materials to pass through it. The thin outer layer of the tunica intima contains a small amount of areolar connective tissue that consists primarily of elastic fibers to provide the vessel with additional flexibility; it also contains some collagenous fibers to provide additional strength.
In larger arteries, there is also a thick, distinct layer of elastic fibers known as the internal elastic membrane (also called the internal elastic lamina) at the boundary with the tunica media. Like the other components of the tunica intima, the internal elastic membrane provides structure while allowing the vessel to stretch. It is permeated with small openings that allow exchange of materials between the tunics. The internal elastic membrane is not apparent in veins. In addition, many veins, particularly in the lower limbs, contain valves formed by sections of thickened endothelium that are reinforced with connective tissue, extending into the lumen.
Under the microscope, the lumen and the entire tunica intima of a vein will appear smooth, whereas those of an artery will normally appear wavy because of the partial constriction of the smooth muscle in the tunica media, the next layer of blood vessel walls.
Tunica Media
The tunica media is the substantial middle layer of the vessel wall (see Figure \(\PageIndex{2}\)). It is generally the thickest layer in arteries, and it is much thicker in arteries than it is in veins. The tunica media consists of layers of smooth muscle supported by connective tissue that is primarily made up of elastic fibers, most of which are arranged in circular sheets. Toward the outer portion of the tunic, there are also layers of longitudinal muscle. Contraction and relaxation of the circular muscles decrease and increase the diameter of the vessel lumen, respectively. Specifically in arteries, vasoconstriction decreases blood flow as the smooth muscle in the walls of the tunica media contracts, making the lumen narrower and increasing blood pressure. Similarly, vasodilation increases blood flow as the smooth muscle relaxes, allowing the lumen to widen and blood pressure to drop. Both vasoconstriction and vasodilation are regulated in part by small vascular nerves, known as nervi vasorum , or “nerves of the vessel,” that run within the walls of blood vessels. These are generally all sympathetic fibers, although some trigger vasodilation and others induce vasoconstriction, depending upon the nature of the neurotransmitter and receptors located on the target cell. Parasympathetic stimulation does trigger vasodilation as well as erection during sexual arousal in the external genitalia of both sexes. Nervous control over vessels tends to be more generalized than the specific targeting of individual blood vessels. Local controls, discussed later, account for this phenomenon. (Seek additional content for more information on these dynamic aspects of the autonomic nervous system.) Hormones and local chemicals also control blood vessels. Together, these neural and chemical mechanisms reduce or increase blood flow in response to changing body conditions, from exercise to hydration. Regulation of both blood flow and blood pressure is discussed in detail later in this chapter.
The smooth muscle layers of the tunica media are supported by a framework of collagenous fibers that also binds the tunica media to the inner and outer tunics. Along with the collagenous fibers are large numbers of elastic fibers that appear as wavy lines in prepared slides. Separating the tunica media from the outer tunica externa in larger arteries is the external elastic membrane (also called the external elastic lamina), which also appears wavy in slides. This structure is not usually seen in smaller arteries, nor is it seen in veins.
Tunica Externa
The outer tunic, the tunica externa (also called the tunica adventitia), is a substantial sheath of connective tissue composed primarily of collagenous fibers. Some bands of elastic fibers are found here as well. The tunica externa in veins also contains groups of smooth muscle fibers. This is normally the thickest tunic in veins and may be thicker than the tunica media in some larger arteries. The outer layers of the tunica externa are not distinct but rather blend with the surrounding connective tissue outside the vessel, helping to hold the vessel in relative position. If you are able to palpate some of the superficial veins on your upper limbs and try to move them, you will find that the tunica externa prevents this. If the tunica externa did not hold the vessel in place, any movement would likely result in disruption of blood flow.
Arteries
An artery is a blood vessel that conducts blood away from the heart. All arteries have relatively thick walls that can withstand the high pressure of blood ejected from the heart. However, those close to the heart have the thickest walls, containing a high percentage of elastic fibers in all three of their tunics. This type of artery is known as an elastic artery (Figure \(\PageIndex{3}\)). Vessels larger than 10 mm in diameter are typically elastic. Their abundant elastic fibers allow them to expand, as blood pumped from the ventricles passes through them, and then to recoil after the surge has passed. If artery walls were rigid and unable to expand and recoil, their resistance to blood flow would greatly increase and blood pressure would rise to even higher levels, which would in turn require the heart to pump harder to increase the volume of blood expelled by each pump (the stroke volume) and maintain adequate pressure and flow. Artery walls would have to become even thicker in response to this increased pressure. The elastic recoil of the vascular wall helps to maintain the pressure gradient that drives the blood through the arterial system. An elastic artery is also known as a conducting artery, because the large diameter of the lumen enables it to accept a large volume of blood from the heart and conduct it to smaller branches.
Farther from the heart, where the surge of blood has dampened, the percentage of elastic fibers in an artery’s tunica intima decreases and the amount of smooth muscle in its tunica media increases. The artery at this point is described as a muscular artery . The diameter of muscular arteries typically ranges from 0.1 mm to 10 mm. Their thick tunica media allows muscular arteries to play a leading role in vasoconstriction. In contrast, their decreased quantity of elastic fibers limits their ability to expand. Fortunately, because the blood pressure has eased by the time it reaches these more distant vessels, elasticity has become less important.
Notice that although the distinctions between elastic and muscular arteries are important, there is no “line of demarcation” where an elastic artery suddenly becomes muscular. Rather, there is a gradual transition as the vascular tree repeatedly branches. In turn, muscular arteries branch to distribute blood to the vast network of arterioles. For this reason, a muscular artery is also known as a distributing artery.
Arterioles
An arteriole is a very small artery that leads to a capillary. Arterioles have the same three tunics as the larger vessels, but the thickness of each is greatly diminished. The critical endothelial lining of the tunica intima is intact. The tunica media is restricted to one or two smooth muscle cell layers in thickness. The tunica externa remains but is very thin (see Figure \(\PageIndex{3}\)).
With a lumen averaging 30 micrometers or less in diameter, arterioles are critical in slowing down—or resisting—blood flow and, thus, causing a substantial drop in blood pressure. Because of this, you may see them referred to as resistance vessels. The muscle fibers in arterioles are normally slightly contracted, causing arterioles to maintain a consistent muscle tone—in this case referred to as vascular tone—in a similar manner to the muscular tone of skeletal muscle. In reality, all blood vessels exhibit vascular tone due to the partial contraction of smooth muscle. The importance of the arterioles is that they will be the primary site of both resistance and regulation of blood pressure. The precise diameter of the lumen of an arteriole at any given moment is determined by neural and chemical controls, and vasoconstriction and vasodilation in the arterioles are the primary mechanisms for distribution of blood flow.
Capillaries
A capillary is a microscopic channel that supplies blood to the tissues, a process called perfusion . Exchange of gases and other substances occurs between the blood in capillaries and the surrounding cells and their tissue fluid (interstitial fluid). The diameter of a capillary lumen ranges from 5–10 micrometers; the smallest are just barely wide enough for an erythrocyte to squeeze through. Flow through capillaries is often described as microcirculation .
The wall of a capillary consists of the endothelial layer surrounded by a basement membrane with occasional smooth muscle fibers. There is some variation in wall structure: In a large capillary, several endothelial cells bordering each other may line the lumen; in a small capillary, there may be only a single cell layer that wraps around to contact itself.
For capillaries to function, their walls must be leaky, allowing substances to pass through. There are three major types of capillaries, which differ according to their degree of “leakiness:” continuous, fenestrated, and sinusoid capillaries (Figure \(\PageIndex{4}\)).
Continuous Capillaries
The most common type of capillary, the continuous capillary , is found in almost all vascularized tissues. Continuous capillaries are characterized by a complete endothelial lining with tight junctions between endothelial cells. Although a tight junction is usually impermeable and only allows for the passage of water and ions, they are often incomplete in capillaries, leaving intercellular clefts that allow for exchange of water and other very small molecules between the blood plasma and the interstitial fluid. Substances that can pass between cells include metabolic products, such as glucose, water, and small hydrophobic molecules like gases and hormones, as well as various leukocytes. Continuous capillaries not associated with the brain are rich in transport vesicles, contributing to either endocytosis or exocytosis. Those in the brain are part of the blood-brain barrier. Here, there are tight junctions and no intercellular clefts, plus a thick basement membrane and astrocyte extensions called end feet; these structures combine to prevent the movement of nearly all substances.
Fenestrated Capillaries
A fenestrated capillary is one that has pores (or fenestrations) in addition to tight junctions in the endothelial lining. These make the capillary permeable to larger molecules. The number of fenestrations and their degree of permeability vary, however, according to their location. Fenestrated capillaries are common in the small intestine, which is the primary site of nutrient absorption, as well as in the kidneys, which filter the blood. They are also found in the choroid plexus of the brain and many endocrine structures, including the hypothalamus, pituitary, pineal, and thyroid glands.
Sinusoid Capillaries
A sinusoid capillary (or sinusoid) is the least common type of capillary. Sinusoid capillaries are flattened, and they have extensive intercellular gaps and incomplete basement membranes, in addition to intercellular clefts and fenestrations. This gives them an appearance not unlike Swiss cheese. These very large openings allow for the passage of the largest molecules, including plasma proteins and even cells. Blood flow through sinusoids is very slow, allowing more time for exchange of gases, nutrients, and wastes. Sinusoids are found in the liver and spleen, bone marrow, lymph nodes (where they carry lymph, not blood), and many endocrine glands including the pituitary and adrenal glands. Without these specialized capillaries, these organs would not be able to provide their myriad of functions. For example, when bone marrow forms new blood cells, the cells must enter the blood supply and can only do so through the large openings of a sinusoid capillary; they cannot pass through the small openings of continuous or fenestrated capillaries. The liver also requires extensive specialized sinusoid capillaries in order to process the materials brought to it by the hepatic portal vein from both the digestive tract and spleen, and to release plasma proteins into circulation.
Metarterioles and Capillary Beds
A metarteriole is a type of vessel that has structural characteristics of both an arteriole and a capillary. Slightly larger than the typical capillary, the smooth muscle of the tunica media of the metarteriole is not continuous but forms rings of smooth muscle (sphincters) prior to the entrance to the capillaries. Each metarteriole arises from a terminal arteriole and branches to supply blood to a capillary bed that may consist of 10–100 capillaries.
The precapillary sphincters , circular smooth muscle cells that surround the capillary at its origin with the metarteriole, tightly regulate the flow of blood from a metarteriole to the capillaries it supplies. Their function is critical: If all of the capillary beds in the body were to open simultaneously, they would collectively hold every drop of blood in the body and there would be none in the arteries, arterioles, venules, veins, or the heart itself. Normally, the precapillary sphincters are closed. When the surrounding tissues need oxygen and have excess waste products, the precapillary sphincters open, allowing blood to flow through and exchange to occur before closing once more (Figure \(\PageIndex{5}\)). If all of the precapillary sphincters in a capillary bed are closed, blood will flow from the metarteriole directly into a thoroughfare channel and then into the venous circulation, bypassing the capillary bed entirely. This creates what is known as a vascular shunt . In addition, an arteriovenous anastomosis may bypass the capillary bed and lead directly to the venous system.
Although you might expect blood flow through a capillary bed to be smooth, in reality, it moves with an irregular, pulsating flow. This pattern is called vasomotion and is regulated by chemical signals that are triggered in response to changes in internal conditions, such as oxygen, carbon dioxide, hydrogen ion, and lactic acid levels. For example, during strenuous exercise when oxygen levels decrease and carbon dioxide, hydrogen ion, and lactic acid levels all increase, the capillary beds in skeletal muscle are open, as they would be in the digestive system when nutrients are present in the digestive tract. During sleep or rest periods, vessels in both areas are largely closed; they open only occasionally to allow oxygen and nutrient supplies to travel to the tissues to maintain basic life processes.
Venules
A venule is an extremely small vein, generally 8–100 micrometers in diameter. Postcapillary venules join multiple capillaries exiting from a capillary bed. Multiple venules join to form veins. The walls of venules consist of endothelium, a thin middle layer with a few muscle cells and elastic fibers, plus an outer layer of connective tissue fibers that constitute a very thin tunica externa (Figure 20.7). Venules as well as capillaries are the primary sites of emigration or diapedesis, in which the white blood cells adhere to the endothelial lining of the vessels and then squeeze through adjacent cells to enter the tissue fluid.
Veins
A vein is a blood vessel that conducts blood toward the heart. Compared to arteries, veins are thin-walled vessels with large and irregular lumens (see Figure \(\PageIndex{6}\)). Because they are low-pressure vessels, larger veins are commonly equipped with valves that promote the unidirectional flow of blood toward the heart and prevent backflow toward the capillaries caused by the inherent low blood pressure in veins as well as the pull of gravity. Table \(\PageIndex{2}\) compares the features of arteries and veins.
| Arteries | Veins | |
|---|---|---|
| Direction of blood flow | Conducts blood away from the heart | Conducts blood toward the heart |
| General appearance | Rounded | Irregular, often collapsed |
| Pressure | High | Low |
| Wall thickness | Thick | Thin |
| Relative oxygen concentration |
Higher in systemic arteries
Lower in pulmonary arteries |
Lower in systemic veins
Higher in pulmonary veins |
| Valves | Not present | Present most commonly in limbs and in veins inferior to the heart |
Disorders of the...
Cardiovascular System: Edema and Varicose Veins
Despite the presence of valves and the contributions of other anatomical and physiological adaptations we will cover shortly, over the course of a day, some blood will inevitably pool, especially in the lower limbs, due to the pull of gravity. Any blood that accumulates in a vein will increase the pressure within it, which can then be reflected back into the smaller veins, venules, and eventually even the capillaries. Increased pressure will promote the flow of fluids out of the capillaries and into the interstitial fluid. The presence of excess tissue fluid around the cells leads to a condition called edema.
Most people experience a daily accumulation of tissue fluid, especially if they spend much of their work life on their feet (like most health professionals). However, clinical edema goes beyond normal swelling and requires medical treatment. Edema has many potential causes, including hypertension and heart failure, severe protein deficiency, renal failure, and many others. In order to treat edema, which is a sign rather than a discrete disorder, the underlying cause must be diagnosed and alleviated.
Edema may be accompanied by varicose veins, especially in the superficial veins of the legs (Figure \(\PageIndex{7}\)). This disorder arises when defective valves allow blood to accumulate within the veins, causing them to distend, twist, and become visible on the surface of the integument. Varicose veins may occur in all people, but are more common in females and are often related to pregnancy. More than simple cosmetic blemishes, varicose veins are often painful and sometimes itchy or throbbing. Without treatment, they tend to grow worse over time. The use of support hose, as well as elevating the feet and legs whenever possible, may be helpful in alleviating this condition. Laser surgery and interventional radiologic procedures can reduce the size and severity of varicose veins. Severe cases may require conventional surgery to remove the damaged vessels. As there are typically redundant circulation patterns, that is, anastomoses, for the smaller and more superficial veins, removal does not typically impair the circulation. There is evidence that patients with varicose veins suffer a greater risk of developing a thrombus or clot.
Veins as Blood Reservoirs
In addition to their primary function of returning blood to the heart, veins may be considered blood reservoirs, since systemic veins contain approximately 64 percent of the blood volume at any given time (Figure \(\PageIndex{8}\)). Their ability to hold this much blood is due to their high capacitance , that is, their capacity to distend (expand) readily to store a high volume of blood, even at a low pressure. The large lumens and relatively thin walls of veins make them far more distensible than arteries; thus, they are said to be capacitance vessels .
When blood flow needs to be redistributed to other portions of the body, the vasomotor center located in the medulla oblongata sends sympathetic stimulation to the smooth muscles in the walls of the veins, causing constriction—or in this case, venoconstriction. Less dramatic than the vasoconstriction seen in smaller arteries and arterioles, venoconstriction may be likened to a “stiffening” of the vessel wall. This increases pressure on the blood within the veins, speeding its return to the heart. As you will note in Figure \(\PageIndex{8}\), approximately 21 percent of the venous blood is located in venous networks within the liver, bone marrow, and integument. This volume of blood is referred to as venous reserve . Through venoconstriction, this “reserve” volume of blood can get back to the heart more quickly for redistribution to other parts of the circulation.
Career Connection
Vascular Surgeons and Technicians
Vascular surgery is a specialty in which the physician deals primarily with diseases of the vascular portion of the cardiovascular system. This includes repair and replacement of diseased or damaged vessels, removal of plaque from vessels, minimally invasive procedures including the insertion of venous catheters, and traditional surgery. Following completion of medical school, the physician generally completes a 5-year surgical residency followed by an additional 1 to 2 years of vascular specialty training. In the United States, most vascular surgeons are members of the Society of Vascular Surgery.
Vascular technicians are specialists in imaging technologies that provide information on the health of the vascular system. They may also assist physicians in treating disorders involving the arteries and veins. This profession often overlaps with cardiovascular technology, which would also include treatments involving the heart. Although recognized by the American Medical Association, there are currently no licensing requirements for vascular technicians, and licensing is voluntary. Vascular technicians typically have an Associate’s degree or certificate, involving 18 months to 2 years of training. The United States Bureau of Labor projects this profession to grow by 29 percent from 2010 to 2020.
Interactive Link
Visit this site to learn more about vascular surgery.
Interactive Link
Visit this site to learn more about vascular technicians.


13.0: Introduction
Where do we find math around us? Math can be found in areas that are expected and sometimes in areas that are surprising. There are many ways that mathematical concepts, such as those in this text, are infused in the world around us. In this chapter, we will explore a sampling of five distinct areas from everyday life where math’s impact plays a meaningful role.
Math's impact on art can be found in numerical relationships that are known to create or enhance beauty. The Fibonacci numbers are one mathematical example that can be found in nature such as in petal count of a rose. On a different note, a mathematical exploration can aid in making a convincing argument on how we can positively impact our environment. Whether looking at the choices of a single individual or the larger impact offered from a collaborative effort, there are measurable responses to positively address climate change. Turning to medicine, which has been a topic of global importance in recent years, we will explore how math is used to determine drug dosage rates and test the validity of a vaccine. Switching back to items of aesthetic nature, we will examine some foundational components of music which, like art, brings beauty and joy to our lives. Finally, we will explore some ways that math is used in sports to predict future performance and analyze tournaments styles.


10.7: QSEN- Advocating for Patient Safety and Quality Care in Nursing Education
The Quality and Safety Education for Nurses (QSEN) project began advocating for safe, quality patient care in 2005 by defining six competencies for nursing graduates. This initiative was created after a decade of review and investigation into the high number and high cost of medical errors in the United States. The goal of the QSEN initiative was to prepare future nurses with the knowledge, skills, and attitudes needed to improve the quality and safety of the health care system. Historically, nursing education focused on knowledge and skill acquisition, but did not address the attitudes and values of the nurse. The QSEN competencies are designed to train nursing students in prelicensure nursing programs. The six QSEN competencies, as shown in Figure 10.6, [1] are Patient-Centered Care, Teamwork and Collaboration, Evidence-Based Practice, Quality Improvement, Safety, and Informatics. [2]
Read the QSEN Prelicensure Table of Competencies .
Patient-Centered Care
The Patient-Centered Care QSEN competency advocates for the client as “the source of control and full partner in providing compassionate and coordinated care based on respect for patient’s preferences, values, and needs.” [3] This competency encourages nurses to consider clients’ cultural traditions and personal beliefs while providing compassionate care. Patient-centered care also includes the family in the care team. The goal of patient-centered care is to improve the individual’s health outcomes. Integration of this competency has led to improved patient satisfaction scores, reduced expenses, and a positive care environment. [4]
Teamwork and Collaboration
The Teamwork and Collaboration QSEN competency focuses on functioning effectively within nursing and interprofessional teams and fostering open communication, mutual respect, and shared decision-making to achieve quality patient care. [5] Effective communication has been proven to reduce errors and improve client safety. [6] The Joint Commission also includes improved communication as one of the National Patient Safety Goals, aligning with this QSEN competency. Collaboration requires information sharing across disciplines with respect for the knowledge, skills, and experience of each team member. Two examples of tools used to promote effective teamwork and collaboration are ISBARR and TeamSTEPPS®. Additionally, “principles of collaboration” have been established by the ANA.
ISBARR
Several communication tools have been developed to improve communication in various health care settings. ISBARR is an example of a well-established communication tool. As previously discussed in the “ Collaboration Within the Interprofessional Team ” chapter, ISBARR is a mnemonic for the components to include when communicating with other health care team members: I ntroduction, S ituation, B ackground, A ssessment, R equest/ R ecommendations, and R epeat back. [7]
TeamSTEPPS®
As previously discussed in the “ Collaboration Within the Interprofessional Team ” chapter, TeamSTEPPS® (Team Strategies and Tools to Enhance Performance and Patient Safety) is a well-established framework to improve client safety through effective communication in health care environments. It consists of four core competencies: communication, leadership, situation monitoring, and mutual support.
Principles of Collaboration
The American Nurses Association (ANA) and the American Organization of Nurse Executives (AONE) jointly created the “Principles of Collaboration” to guide nurses in creating, enhancing, and sustaining collaborative relationships. These principles include effective communication, authentic relationships, and a learning environment and culture. The principle of authentic relationships includes the following guidelines [8] :
- Be true to yourself – be sure your actions match your words and those around you are confident that what they see is what they get.
- Empower others to have ideas, to share those ideas, and to participate in projects that leverage or enact those ideas.
- Recognize and leverage each other’s strengths.
- Be honest 100% of the time – with yourself and with others.
- Respect others’ personalities, needs, and wants.
- Ask for what you want, but stay open to negotiating the difference.
- Assume good intent from others’ words and actions, and assume they are doing their best.
Read more about the “ Principles of Collaboration ” by the ANA and AONE.
Evidence-Based Practice
The Evidence-Based Practice QSEN competency focuses on integrating scientific evidence with clinical expertise and client/family preferences and values for delivery of optimal health care. [9] See Figure 10.7 [10] for an illustration of Evidence-Based Practices (EBP). Read more about EPB in the “ Quality and Evidence-Based Practice ” chapter. Read examples of evidence-based improvements in the following box.
Read these examples of evidence-based practice improvements:
Quality Improvement
The Quality Improvement QSEN competency focuses on using data to monitor the outcomes of care processes and using improvement methods to design and test changes to continuously improve the quality and safety of health care systems. [11] The goal of this competency is to improve processes, policies, and clinical decisions to improve client outcomes and system performance. As the pool of nursing literature grows and nursing practices have been updated to reflect current evidence, health care organizations have seen improvements in quality, safety, and experienced cost savings. [12]
Read more about the quality improvement processes in the “ Quality and Evidence-Based Practice ” chapter.
Safety
The Safety QSEN competency focuses on minimizing “risk of harm to patients and providers through both system effectiveness and individual performance.” [13] Although safety is embedded in all of the QSEN competencies, this competency specifically advocates for preventing client harm. Despite the health care industry’s continued focus on process improvement and improving client outcomes, errors continue to occur, and nurses are often involved in these events as frontline caregivers. Safe nursing practice starts with an awareness of the potential risks for client harm in every situation.
Several initiatives have been adopted to reduce risk for client harm, such as double-checking high-risk medications and verifying a patient’s name and date of birth prior to every intervention. However, client safety is compromised when there are gaps in quality measures such as inadequate staff training, broken equipment, or an organizational culture that doesn’t support best practices.
The “Safety” competency is best addressed by organizations establishing a safety culture where every worker commits to keeping client safety at the center of decision-making. An organization that has a culture of safety encourages reporting of unusual incidents, process failures, or other issues that could cause client harm, allowing the organization to investigate the event and take action to prevent the event from occurring in the future. Improvements are made as a result of a culture that questions attitudes, actions, and decisions in client care and recognizes threats to safety. Read more about safety culture in the “ Legal Implications ” chapter.
Informatics
The Informatics QSEN competency focuses on using information and technology to communicate, manage knowledge, mitigate error, and support decision-making. [14] Health care is filled with various technologies used to promote a safe care environment, such as electronic medical records (EMRs), bedside medication administration devices, smart IV pumps, and medication distribution systems. These technologies provide safeguards and reminders to help prevent client harm, but the nurse must be knowledgeable in using technology, as well as understand how information obtained from technologies is used to improve client patient outcomes. As information related to technology continues to evolve, it is the responsibility of every nurse to participate in continued professional development related to informatics.
- “QSEN Competencies.png" by Chippewa Valley Technical College is licensed under CC BY 4.0 ↵
- QSEN. (n.d.). About. https://qsen.org/about-qsen/ ↵
- QSEN. (n.d.). About. https://qsen.org/about-qsen/ ↵
- Roseman, D., Osborne-Stafsnes, J., Amy, C. H., Boslaugh, S., & Slate-Miller, K. (2013). Early lessons from four 'aligning forces for quality' communities bolster the case for patient-centered care. Health Aff (Millwood), 32 (2), 232-241. https://doi.org/10.1377/hlthaff.2012.1085 ↵
- QSEN. (n.d.). About. https://qsen.org/about-qsen/ ↵
- Burgener, A. M. (2020). Enhancing communication to improve patient safety and to increase patient satisfaction. The Health Care Manager, 39 (3), 128-132. https://doi.org/10.1097/hcm.0000000000000298 ↵
- Enlow, M., Shanks, L., Guhde, J., & Perkins, M. (2010). Incorporating interprofessional communication skills (ISBARR) into an undergraduate nursing curriculum. Nurse Educator, 35 (4), 176-180. https://doi.org/10.1097/nne.0b013e3181e339ac ↵
- American Nurses Association & American Organization of Nurses Executives. (n.d.). ANA/AONE principles for collaborative relationships between clinical nurses and nurse managers. https://www.nursingworld.org/~4af4f2/globalassets/docs/ana/ethics/principles-of-collaborative-relationships.pdf ↵
- QSEN. (n.d.). About. https://qsen.org/about-qsen/ ↵
- "Evidence-Based Practice.jpg" by Kim Ernstmeyer for Chippewa Valley Technical College is licensed under CC BY 4.0 ↵
- QSEN. (n.d.). About. https://qsen.org/about-qsen/ ↵
- Cullen, L., Titler, M. G., & Rempel, G. (2011). An advanced educational program promoting evidence-based practice. Western Journal of Nursing Research, 33 (3), 345-364. https://doi.org/10.1177/0193945910379218 ↵
- QSEN. (n.d.). About. https://qsen.org/about-qsen/ ↵
- QSEN. (n.d.). About. https://qsen.org/about-qsen/ ↵


9.3B: The Upper Class
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The American upper class is the highest socioeconomic bracket in the social hierarchy and is defined by its members’ great wealth and power.
Learning Objectives
- Discuss the most important characteristics of the upper class in the U.S.
Key Points
- Members of the upper class accumulate wealth through investments and capital gains, rather than through annual salaries.
- Households with net worths of $1 million or more may be identified as members of the upper-most socioeconomic demographic, depending on the class model used.
- Sociologist Leonard Beeghley asserts that all households with a net worth of $1 million or more are considered “rich. ” He divides the rich into two sub- groups: the rich and the super-rich.
Key Terms
- investment : The expenditure of capital in expectation of deriving income or profit from its use.
- capital gain : An increase in the value of a capital asset, such as stock or real estate.
The American upper class refers to the “top layer,” or highest socioeconomic bracket, of society in the United States. This social class is most commonly described as those with great wealth and power, and may also be referred to as the capitalist class, or simply as “the rich. ” People in this class commonly have immense influence in the nation’s political and economic institutions as well as in the media.
Many politicians, heirs to fortunes, top business executives such as CEOs, successful venture capitalists, and celebrities are considered members of the upper class. Some prominent and high-rung professionals may also be included if they attain great influence and wealth. The main distinguishing feature of this class is their source of income. While the vast majority of people and households derive their income from salaries, those in the upper class derive their income primarily from investments and capital gains.
Households with a net worth of $1 million or more may be identified as members of the upper-most socioeconomic demographic, depending on the class model used. While most contemporary sociologists estimate that only 1% of households are members of the upper class, sociologist Leonard Beeghley asserts that all households with a net worth of $1 million or more are considered “rich. ” He divides the rich into two sub-groups: the rich and the super-rich. The rich constitute roughly 5% of U.S. households and their wealth is largely in the form of home equity. Other contemporary sociologists, such as Dennis Gilbert, argue that this group is not part of the upper class but rather part of the upper middle class, as its standard of living is largely derived from occupation-generated income and its affluence falls far short of that attained by the top percentile. The super-rich, according to Beeghley, are those able to live off their wealth without depending on occupation-derived income. This demographic constitutes roughly 0.9% of American households. Beeghley’s definition of the super-rich is congruent with the definition of upper class employed by most other sociologists. The top.01% of the population, with an annual income of $9.5 million or more, received 5% of the income of the United States in 2007. These 15,000 families have been characterized as the “richest of the rich. ”


1.11: Real Gases and Critical Phenomena
Skills to Develop
Make sure you thoroughly understand the following essential concepts that have been presented above.
- Real gases are subject to the effects of molecular volume (intermolecular repulsive force) and intermolecular attractive forces.
- The behavior of a real gas approximates that of an ideal gas as the pressure approaches zero.
- The effects of non-ideal behavior are best seen when the PV product is plotted as a function of P . You should be able to identify the regions of such a plot in which attractive and repulsive forces dominate.
- Each real gas has its own unique equation of state. Various general equations of state have been devised in which adjustable constants are used to approximate the behavior of a particular gas.
- The most well-known equation of state is that of van der Waals. Although you need not memorize this equation, you should be able to explain the significance of its terms.
The "ideal gas laws" as we know them do a remarkably good job of describing the behavior of a huge number chemically diverse substances as they exist in the gaseous state under ordinary environmental conditions, roughly around 1 atm pressure and a temperature of 300 K. But when the temperature is reduced, or the pressure is raised, the relation PV = constant that defines the ideal gas begins to break down, and its properties become unpredictable; eventually the gas condenses into a liquid. Why is this important? It is of obvious interest to a chemical engineer who needs to predict the properties of the gases involved in a chemical reaction carried out at several hundred atmospheres pressure. This is especially so when we consider that some of the basic tenets of the ideal gas model have to be abandoned in order to explain such properties as
- the average distance between collisions (the molecules really do take up space!)
- at sufficiently high pressures and low temperatures, intermolecular attractions assume control and the gas condenses to a liquid;
- the viscosity of a gas flowing through a pipe (the molecules do get temporarily "stuck" on the pipe surface, and are therefore affected by intermolecular attractive forces.)
Even so, many of the common laws such as Boyle's and Charles' continue to describe these gases quite well even under conditions where these phenomena are evident. Under ordinary environmental conditions (moderate pressures and above 0°C), the isotherms of substances we normally think of as gases don't appear to differ very greatly from the hyperbolic form
\[\dfrac{PV}{RT} = \text{constant} \label{6.6.1}\]
However, over a wider range of conditions, things begin to get more complicated. Thus isopentane (Figure \(\PageIndex{1}\)) behaves in a reasonably ideal manner above 210 K, but below this temperature the isotherms become somewhat distorted, and at 185 K and below they cease to be continuous, showing peculiar horizontal segments in which reducing the volume does not change the pressure.
Figure \(\PageIndex{1}\): PV curves for the real gas Isopentane
Within this region, any attempt to compress the gas simply "squeezes" some of it into the liquid state whose greater density exactly compensates for the smaller volume, thus maintaining the pressure at a constant value. It turns out that real gases eventually begin to follow their own unique equations of state, and ultimately even cease to be gases. In this unit we will see why this occurs, what the consequences are, and how we might modify the ideal gas equation of state to extend its usefulness over a greater range of temperatures and pressures.
Effects of Intermolecular Forces
According to Boyle's law , the product PV is a constant at any given temperature, so a plot of PV as a function of the pressure of an ideal gas yields a horizontal straight line. This implies that any increase in the pressure of the gas is exactly counteracted by a decrease in the volume as the molecules are crowded closer together. But we know that the molecules themselves are finite objects having volumes of their own, and this must place a lower limit on the volume into which they can be squeezed. So we must reformulate the ideal gas equation of state as a relation that is true only in the limiting case of zero pressure:
\[\lim_{P \rightarrow 0} PV=nRT \label{6.6.2}\]
So what happens when a real gas is subjected to a very high pressure? The outcome varies with both the molar mass of the gas and its temperature, but in general we can see the the effects of both repulsive and attractive intermolecular forces:
- Repulsive forces: As a gas is compressed, the individual molecules begin to get in each other's way, giving rise to a very strong repulsive force acts to oppose any further volume decrease. We would therefore expect the PV vs P line to curve upward at high pressures, and this is in fact what is observed for all gases at sufficiently high pressures.
- Attractive forces: At very close distances, all molecules repel each other as their electron clouds come into contact. At greater distances, however, brief statistical fluctuations in the distribution these electron clouds give rise to a universal attractive force between all molecules. The more electrons in the molecule (and thus the greater the molecular weight), the greater is this attractive force. As long as the energy of thermal motion dominates this attractive force, the substance remains in the gaseous state, but at sufficiently low temperatures the attractions dominate and the substance condenses to a liquid or solid.
The universal attractive force described above is known as the dispersion , or London force. There may also be additional (and usually stronger) attractive forces related to charge imbalance in the molecule or to hydrogen bonding. These various attractive forces are often referred to collectively as van der Waals forces . A plot of PV/RT as a function of pressure is a very sensitive indicator of deviations from ideal behavior, since such a plot is just a horizontal line for an ideal gas. Figures \(\PageIndex{2}\) and \(\PageIndex{3}\) demonstrate how these plots vary with the nature of the gas and with temperature, respectively.
Figure \(\PageIndex{2}\)
Intermolecular attractions , which generally increase with molecular weight, cause the PV product to decrease as higher pressures bring the molecules closer together and thus within the range of these attractive forces; the effect is to cause the volume to decrease more rapidly than it otherwise would. The repulsive forces always eventually win out. However, as the molecules begin to intrude on each others' territory, the stronger repulsive forces cause the curve to bend upward.
Figure \(\PageIndex{3}\)
The temperature makes a big difference! At higher temperatures, increased thermal motions overcome the effects of intermolecular attractions which normally dominate at lower pressures. So all gases behave more ideally at higher temperatures. For any gas, there is a special temperature (the Boyle temperature ) at which attractive and repulsive forces exactly balance each other at zero pressure. As you can see in this plot for methane, some of this balance does remain as the pressure is increased.
The van der Waals Equation of State
How might we modify the ideal gas equation of state to take into account the effects of intermolecular interactions? The first and most well known answer to this question was offered by the Dutch scientist J.D. van der Waals (1837-1923) in 1873. The ideal gas model assumes that the gas molecules are merely points that occupy no volume; the " V " term in the equation is the volume of the container and is independent of the nature of the gas.
Figure \(\PageIndex{4}\)
van der Waals recognized that the molecules themselves take up space that subtracts from the volume of the container, so that the “volume of the gas” V in the ideal gas equation should be replaced by the term ( V–b ), in which b relates to the excluded volume , typically of the order of 20-100 cm 3 mol –1 . The excluded volume surrounding any molecule defines the closest possible approach of any two molecules during collision. Note that the excluded volume is greater then the volume of the molecule, its radius being half again as great as that of a spherical molecule.
The other effect that van der Waals needed to correct for are the intermolecular attractive forces. These are ignored in the ideal gas model, but in real gases they exert a small cohesive force between the molecules, thus helping to hold the gas together and reducing the pressure it exerts on the walls of the container.
Because this pressure depends on both the frequency and the intensity of collisions with the walls, the reduction in pressure is proportional to the square of the number of molecules per volume of space, and thus for a fixed number of molecules such as one mole, the reduction in pressure is inversely proportional to the square of the volume of the gas. The smaller the volume, the closer are the molecules and the greater will be the effect. The van der Walls equation replaces the \(P\) term in the ideal gas equation with \(P + (a / V^2)\) in which the magnitude of the constant a increases with the strength of the intermolecular attractive forces.
The complete van der Waals equation of state can be written as
Figure \(\PageIndex{5}\): van der Waal's equation of state for a real gas
Although most students are not required to memorize this equation, you are expected to understand it and to explain the significance of the terms it contains. You should also understand that the van der Waals constants a and b must be determined empirically for every gas. This can be done by plotting the P-V behavior of the gas and adjusting the values of a and b until the van der Waals equation results in an identical plot. The constant a is related in a simple way to the molecular radius; thus the determination of a constitutes an indirect measurement of an important microscopic quantity.
|
Substance
|
molar mass (g) |
a (L
2
-atm mole
–2
)
|
b (L mol
–1
)
|
|---|---|---|---|
| hydrogen H 2 | 2 | 0.244 | 0.0266 |
| helium He | 4 | 0.034 | 0.0237 |
| methane CH 4 | 16 | 2.25 | 0.0428 |
| water H 2 O | 18 | 5.46 | 0.0305 |
| nitrogen N 2 | 28 | 1.39 | 0.0391 |
| carbon dioxide CO 2 | 44 | 3.59 | 0.0427 |
| carbon tetrachloride CCl 4 | 154 | 20.4 | 0.1383 |
The van der Waals equation is only one of many equations of state for real gases.  These generally take account of higher-order nonlinear attractive forces, and require the use of more empirical constants. Although we will make no use of them in this course, they are widely employed in chemical engineering work in which the behavior of gases at high pressures must be accurately predicted.
Condensation and the Critical Point
The most striking feature of real gases is that they cease to remain gases as the temperature is lowered and the pressure is increased. Figure \(\PageIndex{6}\) illustrates this behavior; as the volume is decreased, the lower-temperature isotherms suddenly change into straight lines. Under these conditions, the pressure remains constant as the volume is reduced. This can only mean that the gas is “disappearing" as we squeeze the system down to a smaller volume. In its place, we obtain a new state of matter, the liquid. In the green-shaded region, two phases, liquid, and gas, are simultaneously present. Finally, at very small volume all the gas has disappeared and only the liquid phase remains. At this point the isotherms bend strongly upward, reflecting our common experience that a liquid is practically incompressible.
Figure \(\PageIndex{6}\)
To better understand this plot, look at the isotherm labeled . As the gas is compressed from to , the pressure rises in much the same way as Boyle's law predicts. Compression beyond , however, does not cause any rise in the pressure. What happens instead is that some of the gas condenses to a liquid. At , the substance is entirely in its liquid state. The very steep rise to corresponds to our ordinary experience that liquids have very low compressibilities. The range of volumes possible for the liquid diminishes as the critical temperature is approached.
The Critical Point
Liquid and gas can coexist only within the regions indicated by the green-shaded area in the diagram above. As the temperature and pressure rise, this region becomes more narrow, finally reaching zero width at the critical point . The values of P, T , and V at this juncture are known as the critical constants P c , T c , and V c . The isotherm that passes through the critical point is called the critical isotherm . Beyond this isotherm, the gas and liquids become indistinguishable; there is only a single fluid phase, sometimes referred to as a supercritical liquid (Figure \(\PageIndex{7}\)).
Figure \(\PageIndex{7}\)
At temperatures below 31°C (the critical temperature ), CO 2 acts somewhat like an ideal gas even at a rather high pressure ( ). Below 31°, an attempt to compress the gas to a smaller volume eventually causes condensation to begin. Thus at 21°C, at a pressure of about 62 atm ( ), the volume can be reduced from 200 cm 3 to about 55 cm 3 without any further rise in the pressure. Instead of the gas being compressed, it is replaced with the far more compact liquid as the gas is essentially being "squeezed" into its liquid phase. After all of the gas has disappeared ( ), the pressure rises very rapidly because now all that remains is an almost incompressible liquid. Above this isotherm ( ), CO 2 exists only as a supercritical fluid .
What happens if you have some liquid carbon dioxide in a transparent cylinder at just under its P c of 62 atm, and you then compress it slightly? Nothing very dramatic until you notice that the meniscus has disappeared. By successively reducing and increasing the pressure, you can "turn the meniscus on and off".
One intriguing consequence of the very limited bounds of the liquid state is that you could start with a gas at large volume and low temperature, raise the temperature, reduce the volume, and then reduce the temperature so as to arrive at the liquid region at the lower left, without ever passing through the two-phase region, and thus without undergoing condensation!
Supercritical fluids
The supercritical state of matter, as the fluid above the critical point is often called, possesses the flow properties of a gas and the solvent properties of a liquid. The density of a supercritical fluid can be changed over a wide range by adjusting the pressure; this, in turn, changes its solubility, which can thus be optimized for a particular application. The picture at the right shows a commercial laboratory device used for carrying out chemical reactions under supercritical conditions.
Supercritical carbon dioxide is widely used to dissolve the caffeine out of coffee beans and as a dry-cleaning solvent. Supercritical water has recently attracted interest as a medium for chemically decomposing dangerous environmental pollutants such as PCBs. Supercritical fluids are being increasingly employed as as substitutes for organic solvents (so-called "green chemistry") in a range of industrial and laboratory processes. Applications that involve supercritical fluids include extractions, nano particle and nano structured film formation, supercritical drying, carbon capture and storage, as well as enhanced oil recovery studies.


12.5: Why It Matters- Building Positive Employee Relations
Why learn to build and maintain positive employees relations?
Michael was hired by a large accounting firm four years ago, after becoming a licensed CPA. There were very few companies hiring when Michael began his job search, so when he received a job offer from ABC Accounting Firm, he quickly accepted it. ABC Accounting provides cubicles for everyone and requires employees to work a minimum of 50 hours a week with a 30-minute paid lunch each day. Meetings are not a common occurrence, as job assignments and changes are usually communicated via email. Michael is paid well for his work but does not look forward to spending all day, every day, in his cubicle. The lack of interaction with his coworkers and supervisors quickly puts him in a bad mood, and he is anxious to leave the office at the end of each work day. Recently, Michael went to after-work drinks with some co-workers and found that a majority of them shared his dissatisfaction with their working environment. Individual morale is low, and the firm as a whole is struggling to increase productivity and reduce turnover.
While each individual will react to different work environments in different way (some people thrive working alone, after all), it seems that ABC Accounting Firm does not have the buy-in of their employees and are doing very little, if anything, to improve employee engagement. If the accounting firm does not act and make improvements, they will see a number of negative consequences including higher turnover, decreased productivity, and overall poor employee attitudes and work ethic.
Employee engagement is essential to running a highly functioning team and should be a key component in every company’s business plan. Companies can help improve engagement and morale in a number of ways, which will have a direct impact on their employees’ attitudes and work ethic.
Contributors and Attributions
- Why It Matters: Building Positive Employee Relations. Authored by : Freedom Learning Group. Provided by : Lumen Learning. License : CC BY: Attribution
- Untitled. Authored by : Sebastian Soska. Provided by : Pixabay. Located at : pixabay.com/photos/smile-meeting-discussion-office-4468555/. License : CC0: No Rights Reserved . License Terms : Pixabay License


8.1: Spore Stain
- Execute the spore staining procedure accurately, distinguishing between spores and vegetative cells under the microscope.
- Understand the significance of spore formation in bacterial survival.
- Identify/give examples of environmental conditions that can stimulate spore formation.
- Interpret staining results accurately to determine the presence or absence of spores in bacterial cultures.
- Differentiate between endo and exospores.
- Identify when endospores are terminal, subterminal, and central in microscopic images, diagrams, and descriptions.
- Apply critical thinking skills to analyze the significance of spore formation in bacterial survival and pathogenicity.
- Discuss the clinical relevance of spore-forming bacteria in healthcare settings.
Spores
Bacterial spores are highly resistant, dormant structures formed by certain genera of bacteria in response to adverse environmental conditions. They can be formed within bacteria (i.e., endospores ) or on the bacterial surface (i.e., exospores ).These conditions may include nutrient limitation, high temperatures, desiccation, or exposure to toxic chemicals. Spores serve as a survival mechanism for the bacteria, allowing them to endure harsh conditions until more favorable conditions arise.
Spores are formed through a process called sporulation , during which a vegetative bacterial cell (i.e., active cell) undergoes a series of morphological changes to produce the spore (Fig. 1A). The spore is encased in a keratin-rich coat that protects against environmental stressors.
Spores can remain viable for extended periods, sometimes even thousands of years until conditions become suitable for germination. When conditions improve, the spore can undergo germination, leading to the emergence of a new vegetative bacterial cell capable of resuming normal metabolic activities and growth.
Not all bacteria have the ability to form spores, but those that do belong primarily to the genera Bacillus and Clostridium. These bacteria are commonly found in soil, water, and various other environments, including the human body, where they can be both beneficial and pathogenic. Bacillus and Clostridium species cause many dangerous and lethal diseases such as botulism, gangrene, tetanus, c-diff, and anthrax.
The location where an endospore is within a vegetative cell is also useful for distinguishing bacterial species. Endospores may be located in a terminal (end of the cell), subterminal (near the end of the cell), or central (middle of the cell) position.
Spore Stain
The spore stain is a differential staining technique used to visualize bacterial spores within a population of bacteria. This staining method utilizes heat to drive the primary stain, usually malachite green, into the spore structures, followed by a counterstain to color the vegetative cells.
First, the smear is flooded with malachite green, the primary stain for spores. Next, heat is applied to the slide using a steam bath. The heat helps drive the malachite green into the spore structures, where it binds to the keratin protein present in the spore coat. After the primary stain has been applied and heated, the smear is decolorized with water. Decolorization is crucial to remove the malachite green from the vegetative cells, leaving only the spores stained. Once decolorization is complete, a counterstain, commonly safranin, is applied to the smear. The counterstain stains the decolorized vegetative cells, differentiating them from the green-stained spores (Fig.2).
The keratin forming the outer portion of the spore wall resists stain. Heating the cells will make the spore wall more permeable to the malachite green so it can then attach. Once in, the malachite green will not come out because the overlying spore wall becomes less permeable when the smear cools.
Clostridium difficile
Clostridium difficile ( C. difficile ), is a spore-forming bacterium responsible for severe gastrointestinal infections, particularly in healthcare settings (e.g., hospitals, nursing homes, etc.). The use of broad-spectrum antibiotics among patients disrupts the normal gut flora, allowing C. difficile , a bacterium commonly found in the large intestine, to grow. This disruption increases the risk of developing a C. difficile infection (i.e., antibiotic-associated colitis), which is often difficult to treat and can lead to recurrent episodes. Symptoms include severe diarrhea, abdominal cramps, fever, nausea, and loss of appetite. Consequently, managing C. difficile infections is a critical concern among infection control programs in hospitals and long-term care facilities.
In healthcare settings, C. difficile is particularly concerning because its spores can persist on surfaces for long periods, resisting common disinfectants and spreading easily between patients and staff. The ability of the endospore stain to identify C. difficile endospores is critical for implementing proper infection control measures. Once detected, specialized cleaning protocols that target spore-forming bacteria, such as bleach or spore-specific disinfectants, are necessary to prevent further spread within healthcare facilities.
Most patients respond well to antibiotic therapy (e.g. Metronidazole or Vancomycin). However, due to damage to the normal gut flora, recurrent infections are common. Fecal microbiota transplantation (FMT) is an innovative treatment option for recurrent C . difficile infections. This procedure involves transferring fecal matter from a healthy donor into the gastrointestinal tract of the infected patient, effectively restoring a balanced gut microbiome. By reintroducing beneficial bacteria, FMT helps to outcompete C. difficile and reduces the likelihood of recurrence.
Laboratory Instructions
Prepare a Bacterial Smear
You may find it helpful to draw a circle (wax pencil is best) on the opposite side of the slide where you will spread your smear. This will help you later in locating the smear. The wax pencil is better than a marker because it will not wash off easily from the glass.
If you are using a liquid culture, gently mix the culture until you get an even, cloudy mixture (it should look somewhat like skim milk). If you mix too aggressively, you will lose the bacterial morphology.
-
Prepare a bacterial smear on the slide:
- If you are taking bacteria from a solid culture (slant or Petri plate), place a loopful of saline, deionized (DI) water, or distilled water onto a microscope slide and use a loop to aseptically add bacteria to the water (avoid taking a large chunk of bacteria since the cells will be too dense to view individual cells). Use the loop to spread the bacteria in the water and spread the water out to make it thinner (it will dry faster).
- If you are taking bacteria from a liquid culture (broth), place 1 or 2 loopful(s) of bacteria directly onto a microscope slide (no saline or water added).
-
Allow the slide(s) to air dry on the slide warmer (or air dry if a slide warmer is not available).
Heat Fix the Bacterial Smear
Once the liquid has completely evaporated on the surface of the slide, heat fix the slide:
Attach a wooden clip to the microscope slide to hold it.
- Pass the underside of the microscope slide through a flame three times. If using a hotplate, place the slide in the center of the hotplate for 30 seconds.
- Allow the slide to cool and then continue with your staining protocol.
If you heat fix too little, the bacteria will wash off the slide. If you heat fix too much, you will cook the bacteria and denature them.
Spore Stain
- Under the fume hood, put a beaker of water on the hot plate and boil until steam is coming up from the water.
- Turn the hot plate heat down so that the water is barely boiling.
- Place a wire staining rack over the beaker. Steam should be coming up through the wire rack.
- Cut a small piece of bibulous paper (or paper towel) and place it on top of the smear on the slide. This will keep the dye from evaporating too quickly, thereby giving more contact time between the dye and the bacteria.
- Flood the smear with the primary dye, malachite green, and leave for 5 minutes. Keep the paper moist with the malachite green. DO NOT let the dye dry on the towel. Add additional drops of malachite green as needed.
- Remove and discard the paper piece in the trash bin.
- Take the slide back to your lab table.
- Wash the slide with water.
- Sit the slide on your staining rack.
- Apply safranin to the smear and leave for 1 minute.
- Wash the slide with water.
- Blot the slide dry (do not wipe) with bibulous paper.
- Place the stained slide under a microscope for examination. Be sure to begin at the lowest power (look for the pink and green colors of the stains). Focus at the lowest power and then increase one objective magnification at a time until you reach oil immersion.
Attributions
- Bacillus subtilis Spore.jpg by Y tambe is licensed under CC BY-SA 3.0
- Chapter Image: OSC Microbio 02 04 Endospores.jpg by CNX OpenStax is licensed under CC BY 4.0
- Endospore Bazillus.jpg by Geoman3 is licensed under CC BY-SA 3.0
- Endospore Formation.png by Farah, Sophia, Alex is licensed under CC BY-SA 4.0
- Microbiology Labs I by Delmar Larsen and Jackie Reynolds is licensed under an undeclared license .
Citations
- Johns Hopkins Medicine. (n.d.). Fecal transplant . Retrieved November 7, 2024, from https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/fecal-transplant
- Centers for Disease Control and Prevention. (2023, September 19). Clostridioides difficile infection . U.S. Department of Health & Human Services. Retrieved November 7, 2024, from https://www.cdc.gov/c-diff/index.html


2.4: Using Topographic Slope to Determine Tree Height
For most natural resources management purposes, land areas and distances are measured in English units. (Research data are collected in metric units.) Therefore, we measure area in acres, tree height in feet, and commonly, horizontal distance in chains (1 chain = 66 ft.). For this reason, many instruments for measuring slope have two scales: %slope and topographic slope. Topographic slope (or Tslope) is essentially the same as %slope, except that instead of expressing the ratio of rise over run as a proportion of 1:100, Tslope is expressed in a proportion of 1:66 as follows:
\[\left(\frac{rise}{run}\right)(66)=\text { Tslope }\]
The different multiplier (66) is the only difference between Tslope and %slope. To solve the Tslope equation for “rise” we do the following:
- Multiply both sides of the equation by “run” to cancel out run on the left side of the equation \[\frac{(r u n)(r i s e)(66)}{r u n}=(run)(\text { Tslope })\]
- Divide both sides by “66” to cancel out 66 on the left side of the equation \[\frac{(\text {rise})(66)}{66}=\frac{(r u n)}{66}(\text { Tslope })\]
That leaves us with the following equation:
\[rise=\frac{(run)}{66}(\text { Tslope })\]
where \(rise =height\)
So, just as with %slope, the Tslope multiplier (66) becomes the denominator.
Topographic slope is most commonly used when measuring merchantable height, but is also fine for measuring total height on shorter trees. Here is an example (Figure 2.7):
Example \(\PageIndex{1}\)
If Jake walks out a horizontal distance of 66 feet (one chain) from the tree, his run will equal the \(Tslope\) multiplier. The “66” will cancel out, and he can simply add his top and stump slope readings together.
Solution
\[rise=\frac{(run)}{66}\left(T_{\text {slape }}\right)\]
\[rise=\frac{(66)}{66}(41+9)\]
\[\text { rise (height) }=50 \text { feet. }\]


Atomic Structure
Skills to Develop
- Define the sub-atomic particles making up an atom
- Distinguish isotopes from typical atoms of an element
- Identify the atomic mass and mass number of an element
- Understand how to utilize units such as coulombs, atomic mass units, and angstroms
Atoms of an element are not all identical and indivisible as Dalton said. They are made of three mains types of particles.
| Particle | Mass (amu) | Charge |
|---|---|---|
| Electrons | 5.5 x 10 –4 | Negative (1–) |
| Protons | 1.0073 | Positive (1+) |
| Neutrons | 1.0087 | Neutral |
The protons and neutrons together form a very small dense center of the atom, called a nucleus . The nucleus contains all the mass of the atom except the small mass of electrons. The electrons move around the nucleus, and occupy a much bigger space than the nucleus, so that most of the atom is empty space.
An element is defined by the number of protons, or atomic number, which is equal to the number of electrons in the neutral element. Atoms of an element can have different numbers of neutrons, resulting in different masses. Isotopes are atoms that have the same number of protons, but different numbers of neutrons. Chemical properties depend mostly on the atomic number, so isotopes are nearly the same chemically. The atomic mass is the average mass of the atom, including all the different isotopes that are likely to be present. If you want to show what isotope of an element you can use special notation, like this: 12 C. This is read as carbon-12. The 12 is the mass number , or the number of protons + neutrons. Since carbon always has 6 protons, 12 C must have 6 neutrons also.
We use some very small units to describe atoms. For instance, the charge of a proton or electron (which we will use as the unit of charge) is 1.602 x 10 –19 coulombs (C). The atomic mass unit, or amu, is 1.661 x 10 –24 g. Sizes of atoms are usually measured in angstroms or Å, which is 1 x 10 –10 m. The diameter of most atoms is 1-5 Å. The diameter of nuclei is roughly 10 –4 Å. Electrons are smaller than nuclei, so most of the atom is empty.
Outside Links
- Khan Academy "Elements and Atoms" (13 min)
- CrashCourse Chemistry 1: The Nucleus (10 min)


20.3: Lab Report
Scientific Method
Part 1: The Strange Case of BeriBeri:
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State the problem.
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What was the hypothesis?
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How was the hypothesis tested?
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Do the results indicate that the hypothesis should be rejected?
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What should be the new hypothesis and how would you test it?
Part 2: How Penicillin Was Discovered:
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Identify the problem.
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What was Fleming's hypothesis?
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How was the hypothesis tested?
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Do the results indicate that the hypothesis should be rejected?
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This experiment led to the development of what major medical advancement…?
Part 3: Identify the Controls and Variables
- Identify the:
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Control Group:
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Independent Variable:
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Dependent Variable:
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What should Smithers' conclusion be?
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How could this experiment be improved?
____________________________________________________________________________________________________________________________________________
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What was the initial observation?
- Identify the:
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Control Group:
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Independent Variable:
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Dependent Variable:
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What should Homer's conclusion be?
______________________________________________________________________________________________________________________________________________
- Identify the:
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Control Group:
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Independent Variable:
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Dependent Variable:
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What should Bart's conclusion be?
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How could Bart's experiment be improved?
___________________________________________________________________________________________________________________________________________
- Identify the:
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Control Group:
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Independent Variable:
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Dependent Variable:
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Explain whether the data supports the advertisement's claims about its product.
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How could this experiment be improved?
______________________________________________________________________________________________________________________________________________
13. Design Lisa's experiment.
Using the Scientific Method to Investigate Termite Behavior
Experiment 1:
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Write a hypothesis and prediction for this experiment: How do you think the termite will react to each circle? Why?
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Place your termite into each circle and record the results. What happens when the termite encounters each circle? Does it follow each of the trails?
Experiment 2:
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Write a hypothesis and a prediction.
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Design your experiment: what is your independent variable? What is your dependent variable? What are your control and experimental groups?
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Write a brief conclusion. What did you find? Did your results support your hypothesis?
Taxonomy
Part 1: A Simple Dichotomous Key
| Creature | Description |
|---|---|
| Jackelope | Mean-spirited horned jack rabbit |
| Chupacabra | Reptilian creature covered in scales with spines along the dorsal ridge; likes to eat goats |
| Altamaha-ha | Water monster with an alligator-like head and long neck; lives in the marshes of Coastal Georgia |
| Sasquatch | Stinky giant humanoid covered in brown fur; found in the forests of North America |
| Yeti | Giant mountain humanoid covered in white fur; prefers the snow |
| Kraken | Giant octopus-like creature; takes down ships in the open ocean |
| Nessie | Water monster with a snake-like head and long neck; lives in Loch Ness, in the Scottish highlands |
Below, you will find the dichotomous key used to identify a folkloric creature you may come across. On the left is the list of questions and on the right, the same list is represented as a flowchart. Both are useful representations of the same dichotomous key.
1. Does the creature live on land?
- a. Yes: go to question 2
- b. No: go to question 5
2. Does the creature resemble a human?
- a. Yes: go to question 3
- b. No: go to question 4
3. Does the creature have brown fur?
- a. Yes: Sasquatch!
- b. No: Yeti!
4. Does the creature have scales?
- a. Yes: Chupacabra!
- b. No: Jackelope!
5. Does the creature have tentacles?
- a. Yes: Kraken!
- b. No: go to question 6
6. Does the creature have a large head, resembling an alligator?
- a. Yes: Altamaha-ha!
- b. No: Nessie!
Using the dichotomous key, identify the creature on the right.
Part 2: Building a Dichotomous Key
| Emoji | Description | Name |
|---|---|---|
Dichotomous Key Questions:
Part 3: Using a Dichotomous Key to Identify Trees
In this section, a dichotomous key will be used to identify tree species based on samples provided by your instructor. Refer to the guide provided should any terms about the characteristics used to distinguish among trees be unfamiliar.
| Plant Number | Scientific/Common Name |
|---|---|
| Plant 1 | |
| Plant 2 | |
| Plant 3 | |
| Plant 4 | |
| Plant 5 | |
| Plant 6 | |
| Plant 7 |


12: Appendix 1: A Very Brief Introduction to EEG and ERPs
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This appendix provides a very brief introduction to the EEG and ERPs (and necessarily oversimplifies some complex issues). It is meant to provide enough background for you to understand the big picture of the analysis procedures described in this book, but it is just a start.
The EEG
The neurons in your brain produce two main kinds of electrical potentials (voltages), called postsynaptic potentials and action potentials . We can’t ordinarily pick up action potentials from the scalp, but the postsynaptic potentials produced by individual neurons can propagate through the brain, skull, and scalp. If we put electrodes on the scalp, as shown in Figure A1.1, we can pick up the propagated postsynaptic potentials. These propagated voltages are what we call the electroencephalogram or EEG . This is a simplification; if you want to know the full story, I recommend Jackson and Bolger (2014) or Buzsáki et al. (2012).
The postsynaptic potentials produced by individual neurons sum together and spread widely before reaching the scalp, so any given electrode is picking up voltages generated by thousands or millions of neurons in a broad set of brain regions. As a result, a voltage picked up at a given electrode site may not represent activity coming from the cortex directly under the electrode.
The EEG may be recorded from just a few electrodes or from as many as 256 electrodes, but most studies include between 16 and 64 electrodes. As shown in Figure A1.2, there is a widely used electrode naming system (the International 10/20 System) in which each electrode is given a 1-2 letters to indicate the general region of the head and a number to indicate the left-right position (or a “z” for the midline). For example, electrode P1 is over parietal cortex, just slightly to the right of the midline, and electrode FCz is on the midline, between the frontal and central regions.
The Reference Electrode
A voltage is the potential for electrical charges to move from one place to another (e.g., from one terminal of a car battery to the other). As a result, the EEG is always a voltage between two electrodes, which we call the active electrode and the reference electrode . Typically, most or all of the active electrodes share the same reference electrode. Consider, for example, the EEG waveforms in Figure A1.1.C. Each waveform has a label, which indicates the active electrode for that waveform, and all of these channels except the bottom two used the same reference electrode, which was located on the mastoid process (the bony protrusion behind the ear, shown in Figure A1.2.B). This means that the waveform labeled F7 shows the electrical potential between the F7 electrode site and the mastoid. In theory, we would like a reference that is electrically neutral and does not impact the observed waveform. In practice, however, there is no neutral site, and the waveform for a given channel is equally impacted by activity arising from the active and reference electrodes.
The horizontal and vertical electrooculogram signals at the bottom of Figure A1.1.C (labeled HEOG and VEOG) use different reference electrodes. The HEOG signal uses HEOG-right as the active electrode (see Figure A1.2.B) and the mirror-image HEOG-left electrode as the reference. The VEOG signal uses the VEOG-lower electrode as the active and the FP2 electrode as the reference. These bipolar configurations make it easier to detect eye movements and blinks, which are large artifacts that propagate across the scalp.
Choosing the best reference electrode can be challenging. Fortunately, you can re-reference your data offline to any electrode (or combination of electrodes) that was in the original recording.
Artifact Rejection and Correction
Some portions of the EEG are contaminated by very large artifacts arising from sources such as eye blinks, eye movements, and muscle activity. In some studies, these epochs are excluded from all analyses, which is called artifact rejection . In other studies, a mathematical procedure is used to estimate the contribution of the artifacts and remove them from the epochs, which is called artifact correction . Many studies use correction for some artifacts and rejection for others.
Signal Averaging and Event-Related Potentials
The EEG is an incredibly complex signal that includes activity generated throughout the cortex from hundreds or even thousands of processes, all of which are summed together in our scalp electrodes. As a result, you can’t get a lot of information about specific neurocognitive processes from looking at the raw EEG. The raw EEG signal can tell you if someone is asleep, awake but zoned out, or highly alert and attentive, and you can sometimes see evidence of pathology (e.g., epileptic spikes). Signal processing methods must be applied to the EEG data to isolate specific processes. Perhaps the simplest of these methods is signal averaging , which we use to extract ERPs from the EEG.
Signal averaging is illustrated in Figure A1.3. The goal of signal averaging is to isolate the electrical potentials (voltages) that are related to specific events (i.e., the event-related potentials ). Signal averaging accomplishes this by assuming that an event such as a stimulus produces a similar waveform on each trial, and random noise is added to this waveform to produce the EEG that we record. If we average together the recorded EEG following many events, then the noise will “average out” and the signal will remain in the average. Figure A1.3.A illustrates the EEG from a single electrode. Whenever an event such as a stimulus or response occurs, an event code is inserted into the EEG data file to mark the time of the event. In this example, the events are stimuli (e.g., shapes flashed on a computer monitor).
For each event, we extract an epoch of EEG data surrounding that event. In this example, the epochs begin 100 ms before stimulus onset (giving us a 100-ms prestimulus baseline period) and extend until 600 ms after stimulus onset. As shown in Figure A1.3.B, all of the epochs for a given type of stimulus are then lined up with respect to time zero. The voltage at a given time for a given stimulus is assumed to be the consistent ERP at that time plus random noise. If we simply average all the epochs together, the noise will largely cancel out, and the averaged ERP waveform will mainly consist of the consistent ERP response (plus some residual noise because we always have a finite number of trials). The number of trials required to produce an acceptable average varies widely across experiments and depends on factors such as how large the ERP is and how much noise is in the EEG. Note that artifact rejection and/or correction are applied prior to averaging.
In ERP research, we use the term noise to refer to any uncontrolled variability in the EEG or in the averaged ERP waveform. We are assuming that the EEG consists of a consistent ERP signal on each trial plus random variability. Anything that causes the EEG to deviate from the consistent ERP signal is considered noise. If we repeated an experiment multiple times for a given participant (assuming no fatigue, no learning, etc.), any differences in the averaged ERP waveforms across repetitions would be a result of this noise. Some of this noise comes from electrical devices in the recording environment that is unintentionally picked up by the recording electrodes. Some of it comes from nonneural biological sources, such as blinks and muscle contractions. Some of it comes from brain activity that is unrelated to the stimuli. All else being equal, an averaged ERP waveform will have less residual noise if more trials are averaged together.
What Do We Mean by “Noise”?
In ERP research, we use the term noise to refer to any uncontrolled variability in the EEG or in the averaged ERP waveform. We are assuming that the EEG consists of a consistent ERP signal on each trial plus random variability. Anything that causes the EEG to deviate from the consistent ERP signal is considered noise. If we repeated an experiment multiple times for a given participant (assuming no fatigue, no learning, etc.), any differences in the averaged ERP waveforms across repetitions would be a result of this noise. Some of this noise comes from electrical devices in the recording environment that is unintentionally picked up by the recording electrodes. Some of it comes from nonneural biological sources, such as blinks and muscle contractions. Some of it comes from brain activity that is unrelated to the stimuli. All else being equal, an averaged ERP waveform will have less residual noise if more trials are averaged together.
ERP Peaks and Components
Figure A1.3.C shows a hypothetical averaged ERP waveform for a visual stimulus recorded at an occipital electrode site (with no noise). The X axis is time, with stimulus onset at time zero. The Y axis is amplitude. The prestimulus period is flat because there should be no consistent stimulus-related activity prior to the stimulus. The waveform begins to deviate from zero at approximately 50-60 ms, which is when visual information typically reaches visual cortex. There is no delay between the postsynaptic potentials generated in the brain and the voltage deflections that we see in an ERP waveform. As a result, the sequence of voltages over time in the ERP waveform corresponds to the sequence of sensory, cognitive, affective, and motor processes that follow the onset of a stimulus.
The ERP waveform consists of a set of positive-going and negative-going waves or peaks , which are related in a complicated way to a set of underlying components in the brain that reflect specific neurocognitive processes. We can’t directly see these components, but we try to draw inferences about them from the observed scalp ERP waveforms (see Chapter 2 in Luck, 2014, for a detailed discussion).
Most ERP components are named with a P or an N to indicate whether they are positive-going or negative-going, followed by a number to indicate the timing. For example, N1 is the first major negative wave and P3 is the third major positive wave. If the number is large (>10), it instead indicates the approximately latency of the peak in milliseconds (e.g., N170 for a negative-going wave that peaks at 170 ms). Sometimes, a component is given a name that reflects the conditions under which it is observed (e.g., the error-related negativity for a negative voltage that is present when the participant makes an incorrect response). Note that the relationship between an underlying component and the observed peaks and waves is complex, and the component names can sometimes be misleading. For example, the P1 elicited by a visual stimulus is completely unrelated to the P1 elicited by an auditory stimulus, but the P3 is the same for auditory and visual stimuli. A detailed discussion is provided in Chapters 2 and 3 of Luck (2014) and by Kappenman and Luck (2012).
To statistically analyze ERP data, researchers typically start by obtaining an amplitude or latency score from each individual participant’s averaged ERP waveform in each group or condition. Then these scores are entered into a statistical analysis that is much like the analysis of a behavioral variable such as response time. For example, you might find the peak latency (the time point when the voltage reaches its maximum value) for the P3 wave in each participant’s ERP waveform and then determine whether the latencies are significantly later in a patient group than in a control group using a t test.
References
Buzsáki, G., Anastassiou, C. A., & Koch, C. (2012). The origin of extracellular fields and currents—EEG, ECoG, LFP and spikes. Nature Reviews Neuroscience , 13 , 407–420. https://doi.org/10.1038/nrn3241
Jackson, A. F., & Bolger, D. J. (2014). The neurophysiological bases of EEG and EEG measurement: A review for the rest of us. Psychophysiology , 51 (11), 1061–1071. https://doi.org/10.1111/psyp.12283
Kappenman, E. S., & Luck, S. J. (2012). ERP components: The ups and downs of brainwave recordings. In S. J. Luck & E. S. Kappenman (Eds.), The Oxford Handbook of ERP Components (pp. 3–30). Oxford University Press.


1.9: Finding background information in Wikipedia
You probably use Wikipedia often. It is a top result in many Google searches, and you may have learned a lot using Wikipedia, despite being told not to use it for research. It can actually serve as a helpful source of background information on a variety of topics. Here are a few ways you can use Wikipedia to help your research.
As a starting point
Wikipedia itself suggests it be used as a starting point and not an end. You can use it to learn vocabulary or technical terms for an unfamiliar topic. Wikipedia is handy for finding dates and timelines for historical events, or for outlining aspects of a topic you had not yet considered.
For related information
Wikipedia can also help you understand how your research question fits into a broader topic. One of Wikipedia’s strengths is that articles include links to other, related articles. These can help you explore the context of your topic. You may come across disambiguation pages as well, which can help you find different entries for a term that has multiple meanings (e.g. Hologram ). These practices can be particularly useful when developing your research question.
To find more sources
Finally, Wikipedia can be useful for finding references to reliable sources such as scholarly books and articles. Most articles have a list of linked references and notes that you can use to verify Wikipedia’s content. Once you’ve found adequate background information on your topic from Wikipedia, you can explore other scholarly and direct sources to get a more complete picture of your topic.
Don’t stop at Wikipedia
Although Wikipedia can be a great resource for background information, not all topics have the same amount of depth or coverage. Entries on popular topics, such as social networking, TV shows, and extreme sports, tend to have more detail. In addition, Wikipedia contains entries on various academic topics, with generally the same level of detail as traditional encyclopedias. These academic entries tend to be summaries and broad overviews because original research is deliberately not included in Wikipedia. When you need more detailed subject knowledge, such as new theories, analyses, and interpretations to back up your projects, you would be better served by investigating scholarly materials such as journal articles and books rather than an encyclopedia.
Wikipedia is a crowdsourced encyclopedia, which means anyone can create and edit content. This is both a strength and a weakness. One of the most fundamental ways the scholarly community determines the reliability and authority of information is by knowing the scholarly or professional credentials of authors. Wikipedia articles are usually signed only with a username or pseudonym. You can’t tell who the authors or editors are or what qualifies them to write on the topic, if they are qualified at all. A survey of Wikipedia contributors found that for 45% of them, the highest degree earned was high school or less. [1]
It’s also important to know who is contributing to Wikipedia because that informs what content is available. This is true of all research, but particularly for a community-managed resource like Wikipedia.  [2] , [3] How might this affect the articles available and the biases found within? What voices are contributing or being excluded, particularly as they relate to race, sex, gender, and other social issues? Keep this in mind as you’re browsing Wikipedia. Just because there is no article about a specific topic yet, that doesn’t mean it isn’t important or deserving of focus.
Both its strengths and weaknesses are linked to the fact that Wikipedia is open to anyone, has a large contributor base, and contains articles written by consensus. This allows authors more freedom over the sharing of information, but also provides a platform for those with negative or exclusionary views, or even false information that may not be vetted by the scholarly community. Unless you yourself are already an expert on the topic you’re reading about, there’s no way to quickly verify the accuracy of a Wikipedia article without consulting other sources on the subject.
- Glott, R., Schmidt, P., & Ghosh, R. (2010). Wikipedia survey: Overview of results . Retrieved from https://web.archive.org/web/20110728182835/http://www.Wikipediastudy.org/docs/Wikipedia_Overview_15March2010-FINAL.pdf ↵
- Wikimedia users. (2019, July 1). User preferences: gender. Retrieved August 16, 2021 from https://en.Wikipedia.org/wiki/Wikipedia:Database_reports/User_preferences#Gender ↵
- Glott, R., Schmidt, P., & Ghosh, R. (2010). Wikipedia survey: Overview of results . Retrieved from https://web.archive.org/web/20110728182835/http://www.Wikipediastudy.org/docs/Wikipedia_Overview_15March2010-FINAL.pdf ↵