6.1.2: Anatomy of the Lymphatic and Immune Systems
Learning Objectives
- Describe the structure and function of the lymphatic tissue (lymph fluid, vessels, ducts, and organs)
- Describe the structure and function of the primary and secondary lymphatic organs
- Discuss the cells of the immune system, how they function, and their relationship with the lymphatic system
The immune system is the complex collection of cells and organs that destroys or neutralizes pathogens that would otherwise cause disease or death. The lymphatic system, for most people, is associated with the immune system to such a degree that the two systems are virtually indistinguishable. The lymphatic system is the system of vessels, cells, and organs that carries excess fluids to the bloodstream and filters pathogens from the blood. The swelling of lymph nodes during an infection and the transport of lymphocytes via the lymphatic vessels are but two examples of the many connections between these critical organ systems.
Functions of the Lymphatic System
A major function of the lymphatic system is to drain body fluids and return them to the bloodstream. Blood pressure causes leakage of fluid from the capillaries, resulting in the accumulation of fluid in the interstitial space—that is, spaces between individual cells in the tissues. In humans, 20 liters of plasma is released into the interstitial space of the tissues each day due to capillary filtration. Once this filtrate is out of the bloodstream and in the tissue spaces, it is referred to as interstitial fluid. Of this, 17 liters is reabsorbed directly by the blood vessels. But what happens to the remaining three liters? This is where the lymphatic system comes into play. It drains the excess fluid and empties it back into the bloodstream via a series of vessels, trunks, and ducts. Lymph is the term used to describe interstitial fluid once it has entered the lymphatic system. When the lymphatic system is damaged in some way, such as by being blocked by cancer cells or destroyed by injury, protein-rich interstitial fluid accumulates (sometimes “backs up” from the lymph vessels) in the tissue spaces. This inappropriate accumulation of fluid referred to as lymphedema may lead to serious medical consequences.
As the vertebrate immune system evolved, the network of lymphatic vessels became convenient avenues for transporting the cells of the immune system. Additionally, the transport of dietary lipids and fat-soluble vitamins absorbed in the gut uses this system.
Cells of the immune system not only use lymphatic vessels to make their way from interstitial spaces back into the circulation, but they also use lymph nodes as major staging areas for the development of critical immune responses. A lymph node is one of the small, bean-shaped organs located throughout the lymphatic system.
Visit this website for an overview of the lymphatic system. What are the three main components of the lymphatic system?
Structure of the Lymphatic System
The lymphatic vessels begin as open-ended capillaries, which feed into larger and larger lymphatic vessels, and eventually empty into the bloodstream by a series of ducts. Along the way, the lymph travels through the lymph nodes, which are commonly found near the groin, armpits, neck, chest, and abdomen. Humans have about 500–600 lymph nodes throughout the body (Figure \(\PageIndex{1}\)).
Figure \(\PageIndex{1}\): Anatomy of the Lymphatic System. Lymphatic vessels in the arms and legs convey lymph to the larger lymphatic vessels in the torso.A major distinction between the lymphatic and cardiovascular systems in humans is that lymph is not actively pumped by the heart, but is forced through the vessels by the movements of the body, the contraction of skeletal muscles during body movements, and breathing. One-way valves (semi-lunar valves) in lymphatic vessels keep the lymph moving toward the heart. Lymph flows from the lymphatic capillaries, through lymphatic vessels, and then is dumped into the circulatory system via the lymphatic ducts located at the junction of the jugular and subclavian veins in the neck.
Lymphatic Capillaries
Lymphatic capillaries , also called the terminal lymphatics, are vessels where interstitial fluid enters the lymphatic system to become lymph fluid. Located in almost every tissue in the body, these vessels are interlaced among the arterioles and venules of the circulatory system in the soft connective tissues of the body (Figure \(\PageIndex{2}\)). Exceptions are the central nervous system, bone marrow, bones, teeth, and the cornea of the eye, which do not contain lymph vessels.
Figure \(\PageIndex{2}\): Lymphatic Capillaries. Lymphatic capillaries are interlaced with the arterioles and venules of the cardiovascular system. Collagen fibers anchor a lymphatic capillary in the tissue (inset). Interstitial fluid slips through spaces between the overlapping endothelial cells that compose the lymphatic capillary.Lymphatic capillaries are formed by a one cell-thick layer of endothelial cells and represent the open end of the system, allowing interstitial fluid to flow into them via overlapping cells (see Figure \(\PageIndex{2}\)). When interstitial pressure is low, the endothelial flaps close to prevent “backflow.” As interstitial pressure increases, the spaces between the cells open up, allowing the fluid to enter. Entry of fluid into lymphatic capillaries is also enabled by the collagen filaments that anchor the capillaries to surrounding structures. As interstitial pressure increases, the filaments pull on the endothelial cell flaps, opening up them even further to allow easy entry of fluid.
In the small intestine, lymphatic capillaries called lacteals are critical for the transport of dietary lipids and lipid-soluble vitamins to the bloodstream. In the small intestine, dietary triglycerides combine with other lipids and proteins, and enter the lacteals to form a milky fluid called chyle . The chyle then travels through the lymphatic system, eventually entering the liver and then the bloodstream.
Larger Lymphatic Vessels, Trunks, and Ducts
The lymphatic capillaries empty into larger lymphatic vessels, which are similar to veins in terms of their three-tunic structure and the presence of valves. These one-way valves are located fairly close to one another, and each one causes a bulge in the lymphatic vessel, giving the vessels a beaded appearance (see Figure \(\PageIndex{2}\)).
The superficial and deep lymphatics eventually merge to form larger lymphatic vessels known as lymphatic trunks . On the right side of the body, the right sides of the head, thorax, and right upper limb drain lymph fluid into the right subclavian vein via the right lymphatic duct (Figure \(\PageIndex{3}\)). On the left side of the body, the remaining portions of the body drain into the larger thoracic duct, which drains into the left subclavian vein. The thoracic duct itself begins just beneath the diaphragm in the cisterna chyli , a sac-like chamber that receives lymph from the lower abdomen, pelvis, and lower limbs by way of the left and right lumbar trunks and the intestinal trunk.
Figure \(\PageIndex{3}\): Major Trunks and Ducts of the Lymphatic System. The thoracic duct drains a much larger portion of the body than does the right lymphatic duct.The overall drainage system of the body is asymmetrical (see Figure \(\PageIndex{3}\)). The right lymphatic duct receives lymph from only the upper right side of the body. The lymph from the rest of the body enters the bloodstream through the thoracic duct via all the remaining lymphatic trunks. In general, lymphatic vessels of the subcutaneous tissues of the skin, that is, the superficial lymphatics, follow the same routes as veins, whereas the deep lymphatic vessels of the viscera generally follow the paths of arteries.
The Organization of Immune Function
The immune system is a collection of barriers, cells, and soluble proteins that interact and communicate with each other in extraordinarily complex ways. The modern model of immune function is organized into three phases based on the timing of their effects. The three temporal phases consist of the following:
- Barrier defenses such as the skin and mucous membranes, which act instantaneously to prevent pathogenic invasion into the body tissues
- The rapid but nonspecific innate immune response , which consists of a variety of specialized cells and soluble factors
- The slower but more specific and effective adaptive immune response , which involves many cell types and soluble factors, but is primarily controlled by white blood cells (leukocytes) known as lymphocytes , which help control immune responses
The cells of the blood, including all those involved in the immune response, arise in the bone marrow via various differentiation pathways from hematopoietic stem cells (Figure \(\PageIndex{4}\)). In contrast with embryonic stem cells, hematopoietic stem cells are present throughout adulthood and allow for the continuous differentiation of blood cells to replace those lost to age or function. These cells can be divided into three classes based on function:
- Phagocytic cells, which ingest pathogens to destroy them
- Lymphocytes, which specifically coordinate the activities of adaptive immunity
- Cells containing cytoplasmic granules, which help mediate immune responses against parasites and intracellular pathogens such as viruses
Lymphocytes: B Cells, T Cells, Plasma Cells, and Natural Killer Cells
As stated above, lymphocytes are the primary cells of adaptive immune responses (Table). The two basic types of lymphocytes, B cells and T cells, are identical morphologically with a large central nucleus surrounded by a thin layer of cytoplasm. They are distinguished from each other by their surface protein markers as well as by the molecules they secrete. While B cells mature in red bone marrow and T cells mature in the thymus, they both initially develop from bone marrow. T cells migrate from bone marrow to the thymus gland where they further mature. B cells and T cells are found in many parts of the body, circulating in the bloodstream and lymph, and residing in secondary lymphoid organs, including the spleen and lymph nodes, which will be described later in this section. The human body contains approximately 10 12 lymphocytes.
B Cells
B cells are immune cells that function primarily by producing antibodies. An antibody is any of the group of proteins that binds specifically to pathogen-associated molecules known as antigens. An antigen is a chemical structure on the surface of a pathogen that binds to T or B lymphocyte antigen receptors. Once activated by binding to antigen, B cells differentiate into cells that secrete a soluble form of their surface antibodies. These activated B cells are known as plasma cells.
T Cells
The T cell , on the other hand, does not secrete antibody but performs a variety of functions in the adaptive immune response. Different T cell types have the ability to either secrete soluble factors that communicate with other cells of the adaptive immune response or destroy cells infected with intracellular pathogens. The roles of T and B lymphocytes in the adaptive immune response will be discussed further in this chapter.
Plasma Cells
Another type of lymphocyte of importance is the plasma cell. A plasma cell is a B cell that has differentiated in response to antigen binding, and has thereby gained the ability to secrete soluble antibodies. These cells differ in morphology from standard B and T cells in that they contain a large amount of cytoplasm packed with the protein-synthesizing machinery known as rough endoplasmic reticulum.
Natural Killer Cells
A fourth important lymphocyte is the natural killer cell, a participant in the innate immune response. A natural killer cell (NK) is a circulating blood cell that contains cytotoxic (cell-killing) granules in its extensive cytoplasm. It shares this mechanism with the cytotoxic T cells of the adaptive immune response. NK cells are among the body’s first lines of defense against viruses and certain types of cancer.
| Lymphocytes | |
|---|---|
| Type of lymphocyte | Primary function |
| B lymphocyte | Generates diverse antibodies |
| T lymphocyte | Secretes chemical messengers |
| Plasma cell | Secretes antibodies |
| NK cell | Destroys virally infected cells |
Visit this website to learn about the many different cell types in the immune system and their very specialized jobs. What is the role of the dendritic cell in an HIV infection?
Primary Lymphoid Organs and Lymphocyte Development
Understanding the differentiation and development of B and T cells is critical to the understanding of the adaptive immune response. It is through this process that the body (ideally) learns to destroy only pathogens and leaves the body’s own cells relatively intact. The primary lymphoid organs are the bone marrow, spleen, and thymus gland. The lymphoid organs are where lymphocytes mature, proliferate, and are selected, which enables them to attack pathogens without harming the cells of the body.
Bone Marrow
In the embryo, blood cells are made in the yolk sac. As development proceeds, this function is taken over by the spleen, lymph nodes, and liver. Later, the bone marrow takes over most hematopoietic functions, although the final stages of the differentiation of some cells may take place in other organs.  The B cell undergoes nearly all of its development in the red bone marrow, whereas the immature T cell, called a thymocyte , leaves the bone marrow and matures largely in the thymus gland.
Figure \(\PageIndex{5}\): Bone Marrow. Red bone marrow fills the head of the femur, and a spot of yellow bone marrow is visible in the center. The white reference bar is 1 cm.Thymus
The thymus gland is a bilobed organ found in the space between the sternum and the aorta of the heart (Figure \(\PageIndex{6}\)). Connective tissue holds the lobes closely together but also separates them and forms a capsule.
Figure \(\PageIndex{6}\): Location, Structure, and Histology of the Thymus. The thymus lies above the heart. The trabeculae and lobules, including the darkly staining cortex and the lighter staining medulla of each lobule, are clearly visible in the light micrograph of the thymus of a newborn. LM × 100. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)The connective tissue capsule further divides the thymus into lobules via extensions called trabeculae. The outer region of the organ is known as the cortex and contains large numbers of thymocytes with some epithelial cells, macrophages, and dendritic cells (two types of phagocytic cells that are derived from monocytes). The cortex is densely packed so it stains more intensely than the rest of the thymus (see Figure \(\PageIndex{6}\)). The medulla, where thymocytes migrate before leaving the thymus, contains a less dense collection of thymocytes, epithelial cells, and dendritic cells.
AGING AND THE...
Immune System
By the year 2050, 25 percent of the population of the United States will be 60 years of age or older. The CDC estimates that 80 percent of those 60 years and older have one or more chronic disease associated with deficiencies of the immune systems. This loss of immune function with age is called immunosenescence. To treat this growing population, medical professionals must better understand the aging process. One major cause of age-related immune deficiencies is thymic involution, the shrinking of the thymus gland that begins at birth, at a rate of about three percent tissue loss per year, and continues until 35–45 years of age, when the rate declines to about one percent loss per year for the rest of one’s life. At that pace, the total loss of thymic epithelial tissue and thymocytes would occur at about 120 years of age. Thus, this age is a theoretical limit to a healthy human lifespan.
Thymic involution has been observed in all vertebrate species that have a thymus gland. Animal studies have shown that transplanted thymic grafts between inbred strains of mice involuted according to the age of the donor and not of the recipient, implying the process is genetically programmed. There is evidence that the thymic microenvironment, so vital to the development of naïve T cells, loses thymic epithelial cells according to the decreasing expression of the FOXN1 gene with age.
It is also known that thymic involution can be altered by hormone levels. Sex hormones such as estrogen and testosterone enhance involution, and the hormonal changes in pregnant women cause a temporary thymic involution that reverses itself, when the size of the thymus and its hormone levels return to normal, usually after lactation ceases. What does all this tell us? Can we reverse immunosenescence, or at least slow it down? The potential is there for using thymic transplants from younger donors to keep thymic output of naïve T cells high. Gene therapies that target gene expression are also seen as future possibilities. The more we learn through immunosenescence research, the more opportunities there will be to develop therapies, even though these therapies will likely take decades to develop. The ultimate goal is for everyone to live and be healthy longer, but there may be limits to immortality imposed by our genes and hormones.
Secondary Lymphoid Organs and their Roles in Active Immune Responses
Lymphocytes develop and mature in the primary lymphoid organs, but they mount immune responses from the secondary lymphoid organs . A naïve lymphocyte is one that has left the primary organ and entered a secondary lymphoid organ. Naïve lymphocytes are fully functional immunologically, but have yet to encounter an antigen to respond to. In addition to circulating in the blood and lymph, lymphocytes concentrate in secondary lymphoid organs, which include the lymph nodes, spleen, and lymphoid nodules. All of these tissues have many features in common, including the following:
- The presence of lymphoid follicles, the sites of the formation of lymphocytes, with specific B cell-rich and T cell-rich areas
- An internal structure of reticular fibers with associated fixed macrophages
- Germinal centers , which are the sites of rapidly dividing B lymphocytes and plasma cells, with the exception of the spleen
- Specialized post-capillary vessels known as high endothelial venules ; the cells lining these venules are thicker and more columnar than normal endothelial cells, which allow cells from the blood to directly enter these tissues
Lymph Nodes
Lymph nodes function to remove debris and pathogens from the lymph, and are thus sometimes referred to as the “filters of the lymph” (Figure \(\PageIndex{7}\)). Any bacteria that infect the interstitial fluid are taken up by the lymphatic capillaries and transported to a regional lymph node. Dendritic cells and macrophages within this organ internalize and kill many of the pathogens that pass through, thereby removing them from the body. The lymph node is also the site of adaptive immune responses mediated by T cells, B cells, and accessory cells of the adaptive immune system. Like the thymus, the bean-shaped lymph nodes are surrounded by a tough capsule of connective tissue and are separated into compartments by trabeculae, the extensions of the capsule. In addition to the structure provided by the capsule and trabeculae, the structural support of the lymph node is provided by a series of reticular fibers laid down by fibroblasts.
Figure \(\PageIndex{7}\): Structure and Histology of a Lymph Node. Lymph nodes are masses of lymphatic tissue located along the larger lymph vessels. The micrograph of the lymph nodes shows a germinal center, which consists of rapidly dividing B cells surrounded by a layer of T cells and other accessory cells. LM × 128. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)
View the University of Michigan WebScope to explore the tissue sample in greater detail.
The major routes into the lymph node are via afferent lymphatic vessels (see Figure \(\PageIndex{7}\)). Cells and lymph fluid that leave the lymph node may do so by another set of vessels known as the efferent lymphatic vessels . Lymph enters the lymph node via the subcapsular sinus, which is occupied by dendritic cells, macrophages, and reticular fibers. Within the cortex of the lymph node are lymphoid follicles, which consist of germinal centers of rapidly dividing B cells surrounded by a layer of T cells and other accessory cells. As the lymph continues to flow through the node, it enters the medulla, which consists of medullary cords of B cells and plasma cells, and the medullary sinuses where the lymph collects before leaving the node via the efferent lymphatic vessels.
Spleen
In addition to the lymph nodes, the spleen is a major secondary lymphoid organ (Figure \(\PageIndex{8}\)). It is about 12 cm (5 in) long and is attached to the lateral border of the stomach via the gastrosplenic ligament. The spleen is a fragile organ without a strong capsule, and is dark red due to its extensive vascularization. The spleen is sometimes called the “filter of the blood” because of its extensive vascularization and the presence of macrophages and dendritic cells that remove microbes and other materials from the blood, including dying red blood cells. The spleen also functions as the location of immune responses to blood-borne pathogens.
Figure \(\PageIndex{8}\): Spleen. (a) The spleen is attached to the stomach. (b) A micrograph of spleen tissue shows the germinal center. The marginal zone is the region between the red pulp and white pulp, which sequesters particulate antigens from the circulation and presents these antigens to lymphocytes in the white pulp. EM × 660. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)The spleen is also divided by trabeculae of connective tissue, and within each splenic nodule is an area of red pulp, consisting of mostly red blood cells, and white pulp, which resembles the lymphoid follicles of the lymph nodes. Upon entering the spleen, the splenic artery splits into several arterioles (surrounded by white pulp) and eventually into sinusoids. Blood from the capillaries subsequently collects in the venous sinuses and leaves via the splenic vein. The red pulp consists of reticular fibers with fixed macrophages attached, free macrophages, and all of the other cells typical of the blood, including some lymphocytes. The white pulp surrounds a central arteriole and consists of germinal centers of dividing B cells surrounded by T cells and accessory cells, including macrophages and dendritic cells. Thus, the red pulp primarily functions as a filtration system of the blood, using cells of the relatively nonspecific immune response, and white pulp is where adaptive T and B cell responses are mounted.
Lymphoid Nodules
The other lymphoid tissues, the lymphoid nodules , have a simpler architecture than the spleen and lymph nodes in that they consist of a dense cluster of lymphocytes without a surrounding fibrous capsule. These nodules are located in the respiratory and digestive tracts, areas routinely exposed to environmental pathogens.
Tonsils are lymphoid nodules located along the inner surface of the pharynx and are important in developing immunity to oral pathogens (Figure \(\PageIndex{9}\)). The tonsil located at the back of the throat, the pharyngeal tonsil, is sometimes referred to as the adenoid when swollen. Such swelling is an indication of an active immune response to infection. Histologically, tonsils do not contain a complete capsule, and the epithelial layer invaginates deeply into the interior of the tonsil to form tonsillar crypts. These structures, which accumulate all sorts of materials taken into the body through eating and breathing, actually “encourage” pathogens to penetrate deep into the tonsillar tissues where they are acted upon by numerous lymphoid follicles and eliminated. This seems to be the major function of tonsils—to help children’s bodies recognize, destroy, and develop immunity to common environmental pathogens so that they will be protected in their later lives. Tonsils are often removed in those children who have recurring throat infections, especially those involving the palatine tonsils on either side of the throat, whose swelling may interfere with their breathing and/or swallowing.
Figure \(\PageIndex{9}\): Locations and Histology of the Tonsils. (a) The pharyngeal tonsil is located on the roof of the posterior superior wall of the nasopharynx. The palatine tonsils lay on each side of the pharynx. (b) A micrograph shows the palatine tonsil tissue. LM × 40. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)Mucosa-associated lymphoid tissue (MALT) consists of an aggregate of lymphoid follicles directly associated with the mucous membrane epithelia. MALT makes up dome-shaped structures found underlying the mucosa of the gastrointestinal tract, breast tissue, lungs, and eyes. Peyer’s patches, a type of MALT in the small intestine, are especially important for immune responses against ingested substances (Figure \(\PageIndex{10}\)). Peyer’s patches contain specialized endothelial cells called M (or microfold) cells that sample material from the intestinal lumen and transport it to nearby follicles so that adaptive immune responses to potential pathogens can be mounted.
Figure \(\PageIndex{10}\): Mucosa-associated Lymphoid Tissue (MALT) Nodule. LM × 40. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)Bronchus-associated lymphoid tissue (BALT) consists of lymphoid follicular structures with an overlying epithelial layer found along the bifurcations of the bronchi, and between bronchi and arteries. They also have the typically less-organized structure of other lymphoid nodules. These tissues, in addition to the tonsils, are effective against inhaled pathogens.
Chapter Review
The lymphatic system is a series of vessels, ducts, and trunks that remove interstitial fluid from the tissues and return it the blood. The lymphatics are also used to transport dietary lipids and cells of the immune system. Cells of the immune system all come from the hematopoietic system of the bone marrow. Primary lymphoid organs, the bone marrow and thymus gland, are the locations where lymphocytes of the adaptive immune system proliferate and mature. Secondary lymphoid organs are site in which mature lymphocytes congregate to mount immune responses. Many immune system cells use the lymphatic and circulatory systems for transport throughout the body to search for and then protect against pathogens.
Interactive Link Questions
Visit this website for an overview of the lymphatic system. What are the three main components of the lymphatic system?
Answer: The three main components are the lymph vessels, the lymph nodes, and the lymph.
Visit this website to learn about the many different cell types in the immune system and their very specialized jobs. What is the role of the dendritic cell in infection by HIV?
Answer: The dendritic cell transports the virus to a lymph node.
Review Questions
Q. Which of the following cells is phagocytic?
A. plasma cell
B. macrophage
C. B cell
D. NK cell
Answer: B
Q. Which structure allows lymph from the lower right limb to enter the bloodstream?
A. thoracic duct
B. right lymphatic duct
C. right lymphatic trunk
D. left lymphatic trunk
Answer: A
Q. Which of the following cells is important in the innate immune response?
A. B cells
B. T cells
C. macrophages
D. plasma cells
Answer: C
Q. Which of the following cells would be most active in early, antiviral immune responses the first time one is exposed to pathogen?
A. macrophage
B. T cell
E. neutrophil
D. natural killer cell
Answer: D
Q. Which of the lymphoid nodules is most likely to see food antigens first?
A. tonsils
B. Peyer’s patches
C. bronchus-associated lymphoid tissue
D. mucosa-associated lymphoid tissue
Answer: A
Critical Thinking Questions
Q. Describe the flow of lymph from its origins in interstitial fluid to its emptying into the venous bloodstream.
A. The lymph enters through lymphatic capillaries, and then into larger lymphatic vessels. The lymph can only go in one direction due to valves in the vessels. The larger lymphatics merge to form trunks that enter into the blood via lymphatic ducts.
Glossary
- adaptive immune response
- relatively slow but very specific and effective immune response controlled by lymphocytes
- afferent lymphatic vessels
- lead into a lymph node
- antibody
- antigen-specific protein secreted by plasma cells; immunoglobulin
- antigen
- molecule recognized by the receptors of B and T lymphocytes
- barrier defenses
- antipathogen defenses deriving from a barrier that physically prevents pathogens from entering the body to establish an infection
- B cells
- lymphocytes that act by differentiating into an antibody-secreting plasma cell
- bone marrow
- tissue found inside bones; the site of all blood cell differentiation and maturation of B lymphocytes
- bronchus-associated lymphoid tissue (BALT)
- lymphoid nodule associated with the respiratory tract
- chyle
- lipid-rich lymph inside the lymphatic capillaries of the small intestine
- cisterna chyli
- bag-like vessel that forms the beginning of the thoracic duct
- efferent lymphatic vessels
- lead out of a lymph node
- germinal centers
- clusters of rapidly proliferating B cells found in secondary lymphoid tissues
- high endothelial venules
- vessels containing unique endothelial cells specialized to allow migration of lymphocytes from the blood to the lymph node
- immune system
- series of barriers, cells, and soluble mediators that combine to response to infections of the body with pathogenic organisms
- innate immune response
- rapid but relatively nonspecific immune response
- lymph
- fluid contained within the lymphatic system
- lymph node
- one of the bean-shaped organs found associated with the lymphatic vessels
- lymphatic capillaries
- smallest of the lymphatic vessels and the origin of lymph flow
- lymphatic system
- network of lymphatic vessels, lymph nodes, and ducts that carries lymph from the tissues and back to the bloodstream.
- lymphatic trunks
- large lymphatics that collect lymph from smaller lymphatic vessels and empties into the blood via lymphatic ducts
- lymphocytes
- white blood cells characterized by a large nucleus and small rim of cytoplasm
- lymphoid nodules
- unencapsulated patches of lymphoid tissue found throughout the body
- mucosa-associated lymphoid tissue (MALT)
- lymphoid nodule associated with the mucosa
- naïve lymphocyte
- mature B or T cell that has not yet encountered antigen for the first time
- natural killer cell (NK)
- cytotoxic lymphocyte of innate immune response
- plasma cell
- differentiated B cell that is actively secreting antibody
- primary lymphoid organ
- site where lymphocytes mature and proliferate; red bone marrow and thymus gland
- right lymphatic duct
- drains lymph fluid from the upper right side of body into the right subclavian vein
- secondary lymphoid organs
- sites where lymphocytes mount adaptive immune responses; examples include lymph nodes and spleen
- spleen
- secondary lymphoid organ that filters pathogens from the blood (white pulp) and removes degenerating or damaged blood cells (red pulp)
- T cell
- lymphocyte that acts by secreting molecules that regulate the immune system or by causing the destruction of foreign cells, viruses, and cancer cells
- thoracic duct
- large duct that drains lymph from the lower limbs, left thorax, left upper limb, and the left side of the head
- thymocyte
- immature T cell found in the thymus
- thymus
- primary lymphoid organ; where T lymphocytes proliferate and mature
- tonsils
- lymphoid nodules associated with the nasopharynx


4.7: Reporting Current Assets
Learning Objectives
- Demonstrate how current assets are reported on the balance sheet
We have already identified assets as a resource with economic value that a company owns or controls with the expectation that it will provide a future benefit. Assets are reported on a company’s balance sheet and are bought or created to increase a firm’s value or benefit the firm’s operations. One of the characteristics of assets is that they can be classified as long-term (held for over one year) or current (held for less than one year).
Current assets include cash and cash equivalents, accounts receivable, and inventory. Cash includes bank account balances, petty cash, and cash equivalents. Cash equivalents are very safe assets that can be readily converted into cash, such as U.S. Treasury Notes and marketable securities such as stocks and bonds. As you learned in the previous section, another major category of current assets is inventory.
Another class of current assets is Accounts Receivable. Companies often sell products or services to customers on credit; these obligations, result in an amount owed to the company or a receivable which are also classified as current assets.
Current assets are the most liquid assets and are listed first on the balance sheet. This is because they will or may turn into cash within a short period of time. For instance, accounts receivable are usually collected within 30 days. In any case, in order for an asset to be classified as current, it must have a life span of less than one year.
It should be noted that not all current assets convert to cash. For instance, prepaid expenses that will expire within the one-year window are listed as current assets. This type of current asset includes things like the annual premium paid for insurance and rent paid in advance. The excerpt from a balance sheet shown below illustrates how current assets are presented:
| Company A | |
|---|---|
| Balance Sheet | |
| Assets | |
| Current Assets | |
| Cash and Cash Equivalents | $65,000 |
| Short Term Investments | $55,000 |
| Accounts Receivable | $45,000 |
| Inventory | $125,000 |
| Prepaid Expenses | $75,000 |
| Other Current Assets | $25,000 |
Practice questions


6.8: Managerial Skills
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7. What set of managerial skills is necessary for managerial success?
In order to be successful in planning, organizing, leading, and controlling, managers must use a wide variety of skills. A skill is the ability to do something proficiently. Managerial skills fall into three basic categories: technical, human relations, and conceptual skills. The degree to which each type of skill is used depends upon the level of the manager’s position as seen in Exhibit 6.8 . Additionally, in an increasingly global marketplace, it pays for managers to develop a special set of skills to deal with global management issues.
Exhibit 6.8 The Importance of Managerial Skills at Different Management Levels (Attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license.)
Technical Skills
Specialized areas of knowledge and expertise and the ability to apply that knowledge make up a manager’s technical skills . Preparing a financial statement, programming a computer, designing an office building, and analyzing market research are all examples of technical skills. These types of skills are especially important for supervisory managers because they work closely with employees who are producing the goods and/or services of the firm.
Human Relations Skills
Human relations skills are the interpersonal skills managers use to accomplish goals through the use of human resources. This set of skills includes the ability to understand human behavior, to communicate effectively with others, and to motivate individuals to accomplish their objectives. Giving positive feedback to employees, being sensitive to their individual needs, and showing a willingness to empower subordinates are all examples of good human relations skills. Identifying and promoting managers with human relations skills are important for companies. A manager with little or no people skills can end up using an authoritarian leadership style and alienating employees.
Conceptual Skills
Conceptual skills include the ability to view the organization as a whole, understand how the various parts are interdependent, and assess how the organization relates to its external environment. These skills allow managers to evaluate situations and develop alternative courses of action. Good conceptual skills are especially necessary for managers at the top of the management pyramid, where strategic planning takes place.
CONCEPT CHECK
- Define the basic managerial skills.
- How important is each of these skill sets at the different levels of the management pyramid?


5.10: The Student t Distribution
In this section we will study a distribution that has special importance in statistics. In particular, this distribution will arise in the study of a standardized version of the sample mean when the underlying distribution is normal.
Basic Theory
Definition
Suppose that \(Z\) has the standard normal distribution, \(V\) has the chi-squared distribution with \(n \in (0, \infty)\) degrees of freedom, and that \(Z\) and \(V\) are independent. Random variable \[ T = \frac{Z}{\sqrt{V / n}} \] has the student \(t\) distribution with \(n\) degrees of freedom .
The student \( t \) distribution is well defined for any \(n \gt 0\), but in practice, only positive integer values of \(n\) are of interest. This distribution was first studied by William Gosset, who published under the pseudonym Student .
Distribution Functions
Suppose that \(T\) has the \( t \) distribution with \( n \in (0, \infty) \) degrees of freedom. Then \( T \) has a continuous distribution on \( \R \) with probability density function \(f\) given by \[ f(t) = \frac{\Gamma[(n + 1) / 2]}{\sqrt{n \pi} \, \Gamma(n / 2)} \left( 1 + \frac{t^2}{n} \right)^{-(n + 1) / 2}, \quad t \in \R \]
Proof
For \( v \gt 0 \), the conditional distribution of \( T \) given \( V = v \) is normal with mean 0 and variance \( n / v \). By definition, \( V \) has the chi-square distribution with \( n \) degrees of freedom. Hence, the joint PDF of \( (T, V) \) is \[ g(t, v) = \sqrt{\frac{v}{2 \pi n}} e^{-v z^2 / 2 n} \frac{1}{2^{n/2} \Gamma(n/2)} v^{n/2-1} e^{-v/2} = \frac{1}{2^{(n+1)/2} \sqrt{n \pi} \, \Gamma(n/2)} v^{(n+1)/2 - 1} e^{-v(1 + t^2/n)/2}, \quad t \in \R, \, v \in (0, \infty) \] The PDF of \( T \) is \[ f(t) = \int_0^\infty g(t, v) \, dv = \frac{1}{2^{(n+1)/2} \sqrt{n \pi} \, \Gamma(n/2)} \int_0^\infty v^{(n+1)/2 - 1} e^{-v(1 + t^2/n)/2} \, dv, \quad t \in \R \] Except for the missing normalizing constant, the integrand is the gamma PDF with shape parameter \( (n + 1)/2 \) and scale parameter \( 2 \big/ (1 + t^2/n) \). Hence \[ f(t) = \frac{1}{2^{(n+1)/2} \sqrt{n \pi} \, \Gamma(n/2)} \Gamma\left[(n + 1)/2\right] \left(\frac{2}{1 + t^2/n}\right)^{(n+1)/2}, \quad t \in \R\] Simplifying gives the result.
The proof of this theorem provides a good way of thinking of the \(t\) distribution: the distribution arises when the variance of a mean 0 normal distribution is randomized in a certain way.
In the special distribution simulator, select the student \(t\) distribution. Vary \(n\) and note the shape of the probability density function. For selected values of \(n\), run the simulation 1000 times and compare the empirical density function to the true probability density function.
The Student probability density function \( f \) with \( n \in (0, \infty) \) degrees of freedom has the following properties:
- \(f\) is symmetric about \(t = 0\).
- \(f\) is increasing and then decreasing with mode \(t = 0\).
- \(f\) is concave upward, then downward, then upward again with inflection points at \( \pm \sqrt{n / (n + 1)}\).
- \(f(t) \to 0\) as \(t \to \infty\) and as \(t \to -\infty\).
In particular, the distribution is unimodal with mode and median at \(t = 0\). Note also that the inflection points converge to \( \pm 1 \) as \( n \to \infty \).
The distribution function and the quantile function of the general \(t\) distribution do not have simple, closed-form representations. Approximate values of these functions can be obtained from the special distribution calculator, and from most mathematical and statistical software packages.
In the special distribution calculator, select the student distribution. Vary the parameter and note the shape of the probability density, distribution, and quantile functions. In each of the following cases, find the first and third quartiles:
- \(n = 2\)
- \(n = 5\)
- \(n = 10\)
- \(n = 20\)
Moments
Suppose that \(T\) has a \(t\) distribution. The representation in the definition can be used to find the mean, variance and other moments of \(T\). The main point to remember in the proofs that follow is that since \( V \) has the chi-square distribution with \( n \) degrees of freedom, \( E\left(V^k\right) = \infty \) if \( k \le -\frac{n}{2} \), while if \( k \gt -\frac{n}{2} \), \[ \E\left(V^k\right) = 2^k \frac{\Gamma(k + n / 2)}{\Gamma(n/2)} \]
Suppose that \(T\) has the \(t\) distribution with \(n \in (0, \infty)\) degrees of freedom. Then
- \(\E(T)\) is undefined if \(0 \lt n \le 1\)
- \(\E(T) = 0\) if \(1 \lt n \lt \infty\)
Proof
By independence, \( \E(T) = \sqrt{n} \E\left(V^{-1/2}\right) \E(Z) \). Of course \( \E(Z) = 0\). On the other hand, \( \E\left(V^{-1/2}\right) = \infty \) if \( n \le 1 \) and \( \E\left(V^{-1/2}\right) \lt \infty \) if \( n \gt 1 \).
Suppose again that \(T\) has the \(t\) distribution with \(n \in (0, \infty)\) degrees of freedom then
- \(\var(T)\) is undefined if \(0 \lt n \le 1\)
- \(\var(T) = \infty\) if \(1 \lt n \le 2\)
- \(\var(T) = \frac{n}{n - 2}\) if \(2 \lt n \lt \infty\)
Proof
By independence, \( \E\left(T^2\right) = n \E\left(Z^2\right) \E\left(V^{-1}\right) \). Of course \( \E\left(Z^2\right) = 1 \). On the other hand, \( \E\left(V^{-1}\right) = \infty \) if \( n \le 2 \) and \( \E\left(V^{-1}\right) = 1 \big/ (n - 2) \) if \( n \gt 2 \). The results now follow from the previous result on the mean .
Note that \(\var(T) \to 1\) as \(n \to \infty\).
In the simulation of the special distribution simulator, select the student \(t\) distribution. Vary \(n\) and note the location and shape of the mean \( \pm \) standard deviation bar. For selected values of \(n\), run the simulation 1000 times and compare the empirical mean and standard deviation to the distribution mean and standard deviation.
Next we give the general moments of the \( t \) distribution.
Suppose again that \(T\) has the \(t\) distribution with \(n \in (0, \infty)\) degrees of freedom and \( k \in \N \). Then
- \(\E\left(T^k\right)\) is undefined if \(k\) is odd and \(k \ge n\)
- \(\E\left(T^k\right) = \infty\) if \(k\) is even and \(k \ge n\)
- \(\E\left(T^k\right) = 0\) if \(k\) is odd and \(k \lt n\)
- If \(k\) is even and \(k \lt n\) then \[ \E\left(T^k\right) = \frac{n^{k/2} 1 \cdot 3 \cdots (k - 1) \Gamma\left((n - k) \big/ 2\right)}{2^{k/2} \Gamma(n/2)} = \frac{n^{k/2} k! \Gamma\left((n - k)\big/2\right)}{2^k (k/2)! \Gamma(n/2)} \]
Proof
By independence, \( \E\left(T^k\right) = n^{k/2} \E\left(Z^k\right) \E\left(V^{-k/2}\right) \). Recall that \( \E\left(Z^k\right) = 0 \) if \( k \) is odd, while \[ \E\left(Z^k\right) = 1 \cdot 3 \cdots (k - 1) = \frac{k!}{(k/2)! 2^{k/2}} \] if \( k \) is even. Also, \( \E\left(V^{-k/2}\right) = \infty \) if \( k \ge n \), while \[ \E\left(V^{-k/2}\right) = \frac{2^{-k/2} \Gamma\left((n - k) \big/ 2\right)}{\Gamma(n/2)} \] if \( k \lt n \). The results now follow by considering the various cases.
From the general moments, we can compute the skewness and kurtosis of \( T \).
Suppose again that \( T \) has the \( t \) distribution with \( n \in (0, \infty) \) degrees of freedom. Then
- \( \skw(T) = 0 \) if \( n \gt 3 \)
- \( \kur(T) = 3 + \frac{6}{n - 4} \) if \( n \gt 4 \)
Proof
- This follows from the symmetry of the distribution of \( T \), although \( \skw(T) \) only exists if \( \E\left(T^3\right) \) exists.
- For \( n \gt 4 \), \[ \kur(T) = \frac{\E(T^4)}{\left[\E\left(T^2\right)\right]^2} = \frac{3 n^2 \Gamma\left[(n - 4) / 2\right] \big/ 4 \Gamma(n/2)}{\left(n \big/ (n - 2) \right)^2} = \frac{3 (n - 2)^2 \Gamma\left[(n - 4) / 2\right]}{4 \Gamma(n/2)}\] But \( \Gamma(n/2) = (n/2 - 1) (n/2 - 2) \Gamma(n/2 - 2) \). Simplifying gives the result.
Note that \( \kur(T) \to 3 \) as \( n \to \infty \) and hence the excess kurtosis \( \kur(T) - 3 \to 0 \) as \( n \to \infty \).
In the special distribution simulator, select the student \(t\) distribution. Vary \(n\) and note the shape of the probability density function in light of the previous results on skewness and kurtosis. For selected values of \(n\), run the simulation 1000 times and compare the empirical density function to the true probability density function.
Since \( T \) does not have moments of all orders, there is no interval about 0 on which the moment generating function of \( T \) is finite. The characteristic function exists, of course, but has no simple representation, except in terms of special functions.
Relations
The \(t\) distribution with 1 degree of freedom is known as the Cauchy distribution . The probability density function is \[ f(t) = \frac{1}{\pi (1 + t^2)}, \quad t \in \R \]
The Cauchy distribution is named after Augustin Cauchy and is studied in more detail in a separate section.
You probably noticed that, qualitatively at least, the \(t\) probability density function is very similar to the standard normal probability density function. The similarity is quantitative as well:
Let \( f_n \) denote the \( t \) probability density function with \( n \in (0, \infty) \) degrees of freedom. Then for fixed \(t \in \R\), \[ f_n(t) \to \frac{1}{\sqrt{2 \pi}} e^{-\frac{1}{2} t^2} \text{ as } n \to \infty \]
Proof
From a basic limit theorem in calculus, \[ \left( 1 + \frac{t^2}{n} \right)^{-(n + 1) / 2} \to e^{-t^2/2} \text{ as } n \to \infty \] An application of Stirling's approximation shows that \[ \frac{\Gamma[(n + 1) / 2]}{\sqrt{n \pi} \, \Gamma(n / 2)} \to \frac{1}{\sqrt{2 \pi}} \text{ as } n \to \infty \]
Note that the function on the right is the probability density function of the standard normal distribution. We can also get convergence of the \( t \) distribution to the standard normal distribution from the basic random variable representation in the definition .
Suppose that \( T_n \) has the \( t \) distribution with \( n \in \N_+ \) degrees of freedom, so that we can represent \( T_n \) as \[ T_n = \frac{Z}{\sqrt{V_n / n}} \] where \( Z \) has the standard normal distribution, \( V_n \) has the chi-square distribution with \( n \) degrees of freedom, and \( Z \) and \( V_n \) are independent. Then \( T_n \to Z \) as \( n \to \infty \) with probability 1.
Proof
We can represent \( V_n \) as \( V_n = Z_1^2 + Z_2^2 + \cdots Z_n^2 \) where \( (Z_1, Z_2, \ldots, Z_n) \) are independent, standard normal variables, independent of \( Z \). Note that \(V_n / n \to 1\) as \(n \to \infty\) with probability 1 by the strong law of large numbers.
The \(t\) distribution has more probability in the tails, and consequently less probability near 0, compared to the standard normal distribution.
The Non-Central \( t \) Distribution
One natural way to generalize the student \( t \) distribution is to replace the standard normal variable \( Z \) in the definition above with a normal variable having an arbitrary mean (but still unit variance). The reason this particular generalization is important is because it arises in hypothesis tests about the mean based on a random sample from the normal distribution, when the null hypothesis is false. For details see the sections on tests in the normal model and tests in the bivariate normal model in the chapter on Hypothesis Testing.
Suppose that \(Z\) has the standard normal distribution, \( \mu \in \R \), \(V\) has the chi-squared distribution with \(n \in (0, \infty)\) degrees of freedom, and that \(Z\) and \(V\) are independent. Random variable \[ T = \frac{Z + \mu}{\sqrt{V / n}} \] has the non-central student \(t\) distribution with \(n\) degrees of freedom and non-centrality parameter \( \mu \).
The standard functions that characterize a distribution—the probability density function, distribution function, and quantile function—do not have simple representations for the non-central \( t \) distribution, but can only be expressed in terms of other special functions. Similarly, the moments do not have simple, closed form expressions either. For the beginning student of statistics, the most important fact is that the probability density function of the non-central \( t \) distribution is similar (but not exactly the same) as that of the standard \( t \) distribution (with the same degrees of freedom), but shifted and scaled. The density function is shifted to the right or left, depending on whether \( \mu \gt 0 \) or \( \mu \lt 0 \).
Computational Exercises
Suppose that \(T\) has the \(t\) distribution with \(n = 10\) degrees of freedom. For each of the following, compute the true value using the special distribution calculator and then compute the normal approximation. Compare the results.
- \(\P(-0.8 \lt T \lt 1.2)\)
- The 90th percentile of \(T\).
Answer
- \(\P(-0.8 \lt T \lt 1.2) = 0.650\), \(\P(-0.8 \lt T \lt 1.2) \approx 0.673\)
- \(x_{0.90} = 1.372\), \(x_{0.90} \approx 1.281\)


13.7: Sample problems and solutions
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Exercise \(\PageIndex{1}\)
Ty ( \(m=30\text{kg}\) ) is trying out a new piece of equipment at his local playground. The equipment consists of a platform that is connected to two springs. The top spring ( \(k_1=2400\text{N/m}\) ) connects the platform to the playground structure and the bottom spring ( \(k_2=3480\text{N/m}\) ) (Figure \(\PageIndex{1}\)) connects it to the ground. When no one is standing on the platform the platform is \(50\text{cm}\) off the ground. When Ty is standing on the platform, he oscillates up and down, and the lowest point that the platform reaches is \(35\text{cm}\) off the ground. Show that this is simple harmonic motion and determine what Ty’s maximum speed will be.
- Answer
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First, we need to solve for the new equilibrium position of the platform, \(x_0\) , when Ty is standing on the platform. We define the \(x\) axis so that the origin is \(50\text{cm}\) above the ground (the equilibrium position when no one is standing on the platform) and choose the positive direction to be downwards (Figure \(\PageIndex{2}\)).
Even though we do not know the mass of the platform, or the actual resting lengths of the spring, we do not need to know these, since we can model the platform with nobody on it as a single spring with spring constant \(k=k_1+k_2\) and rest position \(x=0\) .
When Ty is standing on the platform, the sum of the forces is given by his weight and the force from the “effective spring”:
\[\begin{aligned} \sum F=mg-(k_1+k_2)x\end{aligned}\]
where we noted that, when the platform moves down, both the top and bottom spring will exert a force upwards (Figure \(\PageIndex{3}\)).
At equilibrium, the sum of the forces is equal to zero. We can use this to solve for the displacement at \(x_0\) :
\[\begin{aligned} 0&=mg-(k_1+k_2)x_0\\[4pt] \therefore x_0&=\frac{mg}{k_1+k_2}=\frac{(30\text{kg})(9.8\text{m/s}^{2})}{(2400\text{Nm})+(3480\text{Nm})}=0.05\text{m}\end{aligned}\]
We will confirm that this is a simple harmonic oscillator by showing that the system’s motion can be described by the equation:
\[\begin{aligned} \frac{d^2x}{dt^2}&=-\omega^2x\end{aligned}\]
For some position \(x\) below equilibrium, we can rewrite Newton’s second law as:
\[\begin{aligned} ma&=mg-(k_1+k_2)x\\[4pt] m\frac{d^2x}{dt^2}&=mg-(k_1+k_2)x\end{aligned}\]
In order to show that this is simple harmonic motion, we need to combine the right hand side of the equation into one term. We found earlier that \(mg=(k_1+k_2)x_0\) , which we can use here:
\[\begin{aligned} m\frac{d^2x}{dt^2}&=(k_1+k_2)x_0-(k_1+k_2)x\\[4pt] \frac{d^2x}{dt^2}&=\frac{(k_1+k_2)}{m}(x_0-x)\\[4pt] \frac{d^2x}{dt^2}&=-\frac{(k_1+k_2)}{m}(x-x_0)\\[4pt]\end{aligned}\]
We now define an \(x'\) axis such that \(x'=x-x_0\) . This means that the origin of the \(x'\) axis is at the new equilibrium position:
We can now rewrite our expression using the \(x'\) axis:
\[\begin{aligned} \frac{d^2x}{dt^2}&=-\frac{(k_1+k_2)}{m}x'\end{aligned}\]
This equation tells us that this is simple harmonic motion about the new equilibrium position, where \(\omega=\sqrt{(k_1+k_2)/m}\) . We know that the lowest point that the platform reaches is 35 cm above the ground, which, on our \(x'\) axis, corresponds to \(x'=10\text{cm}\) (Figure \(\PageIndex{3}\)). Thus, the amplitude of the oscillation is \(A=0.1\text{m}\) . Because this is simple harmonic motion, we know that the position of the platform can be described by the following function:
\[\begin{aligned} x'(t)&= A \cos(\omega t + \phi)\end{aligned}\]
We set \(t=0\) to be when the platform is at its lowest point ( \(x'=A\) ). The value of \(\phi\) is thus:
\[\begin{aligned} x'(0)&= A \cos(\omega (0) + \phi)\\[4pt] A&= A \cos(\phi)\\[4pt] 1&=\cos(\phi)\\[4pt] \therefore \phi&=0\end{aligned}\]
The velocity is given by:
\[\begin{aligned} v(t)=\frac{d}{dt}x(t) &= -A\omega\sin(\omega t + \phi)\\[4pt] &=-A\omega\sin(\omega t)\end{aligned}\]
The speed will be maximized when \(\sin(\omega t)=1\quad \textrm{or} -1\) . So, the maximum speed will be:
\[\begin{aligned} |v|&=A\omega\\[4pt] |v|&=A\sqrt{\frac{(k_1+k_2)}{m}}\\[4pt] |v|&=(0.1\text{m})\sqrt{\frac{(2400\text{Nm}+3480\text{Nm})}{30\text{kg}}}\\[4pt] |v|&=1.4\text{m/s}\end{aligned}\]
Exercise \(\PageIndex{2}\)
A torsional pendulum consists of a horizontal rod suspended from a vertical wire. When the rod is rotated so that it is displaced an angle \(\theta\) from equilibrium, the wire (which is now twisted) provides a restoring torque about the axis of the wire given by:
\[\begin{aligned} \tau=-\kappa\theta\end{aligned}\]
where \(\kappa\) is the torsion coefficient, which depends on the stiffness of the wire. You may notice that this formula closely resembles Hooke’s law.
a. You construct a torsional pendulum by attaching two small spherical masses (you can assume they are point masses, each of mass \(m\) ) to the ends of a thin (mass-less) rod of length \(L\) and attaching a wire to the center of the rod (Figure \(\PageIndex{4}\)). When you displace one of the masses by an angle \(\theta\) and release it, you find that it oscillates with a period \(T\) . Find an expression for the torsion coefficient, \(\kappa\) , in term of \(T\) , \(m\) , and \(L\) .
b. You place two very large spheres, each of mass \(M\) , near each of the small spheres (as shown in Figure \(\PageIndex{5}\)). Each of the small spheres will be acted on by a force of gravity from the nearest large sphere. The pendulum is at equilibrium when it is deflected an angle \(\beta\) from its original equilibrium position. At the new equilibrium, the displacement vectors connecting the centers of large and small spheres have a magnitude \(d\) and are essentially perpendicular to the rod. Find an expression for the universal gravitational constant \(G\) , in terms of the masses, the length of the rod, and the period measured in part a).
Fun fact! This set-up resembles an experiment performed by Henry Cavendish that was first used to determine the value for \(G\) and to test Newton’s Universal Theory of Gravity.
- Answer
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The only force that creates a torque on the masses is the restoring force from the twisting of the wire. The rotational dynamics version of Newton’s Second Law relates this torque to the angular acceleration, \(\alpha\) of the rod:
\[\begin{aligned} I\alpha=-\kappa\theta\end{aligned}\]
where \(I\) is the moment of inertia of the rod. Rewriting \(\alpha\) more explicitly as the second time derivative of the angle, we get:
\[\begin{aligned} I\frac{d^2\theta}{dt^2}&=-\kappa\theta\\[4pt] \frac{d^2\theta}{dt^2}&=-\frac{\kappa}{I}\theta\\[4pt]\end{aligned}\]
By inspection, we can see that the torsional pendulum is a simple harmonic oscillator, where \(\omega=\sqrt{\kappa/I}\) . The period of the motion is therefore:
\[\begin{aligned} T&=\frac{2\pi}{\omega}\\[4pt] T&=2\pi\sqrt{\frac{I}{\kappa}}\end{aligned}\]
We can rearrange this expression to get \(\kappa\) :
\[\begin{aligned} T^2&=\frac{4\pi^2I}{\kappa}\\[4pt] \kappa&=\frac{4\pi^2I}{T^2}\end{aligned}\]
The moment of inertia for one of the masses is \(m(L/2)^2\) , where \(L/2\) is the distance from the mass to the axis of rotation. The moment of inertia for the two masses attached to the mass-less rod is:
\[\begin{aligned} I&=2m\left(\frac{L}{2}\right)^2=\frac{mL^2}{2}\\[4pt]\end{aligned}\]
Putting this into our expression for \(\kappa\) :
\[\begin{aligned} \kappa=\frac{2\pi^2mL^2}{T^2}\end{aligned}\]
The two forces that provide torques for the small spheres are gravity and the force exerted by the twisting wire. Each of the small spheres will experience a force due to gravity from the nearest large sphere. At equilibrium, the force due to gravity on one of the small spheres is therefore:
\[\begin{aligned} F_g=\frac{GMm}{d^2}\end{aligned}\]
Assuming that, at equilibrium, the force vector is perpendicular to the rod, the torque from one of the large spheres is just the force multiplied by the distance to the axis of rotation. Since there are two large spheres, each of which creates a torque on the pendulum, the total torque due to gravity is:
\[\begin{aligned} \tau_g&=2F_g\frac{L}{2}\\[4pt] &=F_gL\\[4pt] &=\frac{GMm}{d^2}L\end{aligned}\]
(Note that \(\tau g\) is the torque due to gravity at equilibrium only ). We can use Newton’s second law for the pendulum to find an expression for \(G\) . At equilibrium, the net torque is equal to zero, and the angle of deflection is \(\beta\) :
\[\begin{aligned} \tau_{net}&=\tau_{wire}-\tau_g\\[4pt] 0&=\tau_{wire}-\tau_g\\[4pt] \tau_g&=\tau_{wire}\\[4pt] \frac{GMm}{d^2}L&=\kappa\beta\\[4pt] \therefore G&=\frac{\kappa\beta d^2}{LMm}\end{aligned}\]
Using our expression for \(\kappa\) found in part a), this becomes:
\[\begin{aligned} G=\frac{2\pi^2L\beta d^2}{MT^2}\end{aligned}\]


18: Cardiovascular System - Blood Vessels and Circulation
The blood vessels form the distribution network of the cardiovascular system. Each specific type of vessel has specialized anatomy that is critical to keep blood circulating through both circuits of blood flow to collect and distribute nutrients, collect and deliver waste products for removal, deliver hormonal signals to adjust body functions, and help the body maintain homeostasis. (Thumbnail image credit: Human Heart and Circulatory System by Bryan Brandenburg is licensed under CC BY 3.0 )
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- 18.1: Introduction to Blood Vessels and Circulation
- In this chapter, you will learn about the vascular part of the cardiovascular system, that is, the vessels that transport blood throughout the body and provide the physical site where gases, nutrients, and other substances are exchanged with body cells. When vessel functioning is reduced, blood-borne substances do not circulate effectively throughout the body. As a result, tissue injury occurs, metabolism is impaired, and the functions of every bodily system are threatened.
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- 18.2: Structure and Function of Blood Vessels
- 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.
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- 18.3: Circulatory Pathways
- Virtually every cell, tissue, organ, and system in the body is impacted by the circulatory system. This includes the generalized and more specialized functions of transport of materials, capillary exchange, maintaining health by transporting white blood cells and various immunoglobulins (antibodies), hemostasis, regulation of body temperature, and helping to maintain acid-base balance. In addition to these shared functions, many systems enjoy a unique relationship with the circulatory system.
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- 18.4: Development of Blood Vessels and Fetal Circulation
- In a developing embryo,the heart has developed enough by day 21 post-fertilization to begin beating. Circulation patterns are clearly established by the fourth week of embryonic life. It is critical to the survival of the developing human that the circulatory system forms early to supply the growing tissue with nutrients and gases, and to remove waste products. Development of these circulatory elements within the embryo itself begins approximately 2 days later.


18.1A: Blood Vessel Structure
Blood vessels are flexible tubes that carry blood, associated oxygen, nutrients, water, and hormones throughout the body.
- Differentiate among the structure of arteries, veins, and capillaries
Key Points
- Blood vessels consist of arteries, arterioles, capillaries, venules, and veins. Vessel networks deliver blood to all tissues in a directed and regulated manner.
- Arteries and veins are composed of three tissue layers.
- The thick outermost layer of a vessel (tunica adventitia or tunica externa ) is made of connective tissue.
- The middle layer ( tunica media ) is thicker and contains more contractile tissue in arteries than in veins. It consists of circularly arranged elastic fibers, connective tissue, and smooth muscle cells.
- The inner layer ( tunica intima ) is the thinnest layer, comprised of a single layer of endothelium supported by a subendothelial layer.
- Capillaries consist of a single layer of endothelium and associated connective tissue.
Key Terms
- tunica intima : The innermost layer of a blood vessel.
- tunica externa : The outermost layer of a blood vessel.
- capillary : Any of the small blood vessels that connect arteries to veins.
- tunica media : The middle layer of a blood vessel.
- anastomosis : The junction between blood vessels.
Blood vessels are key components of the systemic and pulmonary circulatory systems that distribute blood throughout the body. There are three major types of blood vessels: arteries that carry blood away from the heart, branching into smaller arterioles throughout the body and eventually forming the capillary network. The latter facilitates efficient chemical exchange between tissue and blood. Capillaries in turn merge into venules, then into larger veins responsible for returning the blood to the heart. The junctions between vessels are called anastomoses.
Arteries and veins are comprised of three distinct layers while the much smaller capillaries are composed of a single layer.
Tunica Intima
The inner layer (tunica intima) is the thinnest layer, formed from a single continuous layer of endothelial cells and supported by a subendothelial layer of connective tissue and supportive cells. In smaller arterioles or venules, this subendothelial layer consists of a single layer of cells, but can be much thicker in larger vessels such as the aorta. The tunica intima is surrounded by a thin membrane comprised of elastic fibers running parallel to the vessel. Capillaries consist only of the thin endothelial layer of cells with an associated thin layer of connective tissue.
Tunica Media
Surrounding the tunica intima is the tunica media, comprised of smooth muscle cells and elastic and connective tissues arranged circularly around the vessel. This layer is much thicker in arteries than in veins. Fiber composition also differs; veins contain fewer elastic fibers and function to control caliber of the arteries, a key step in maintaining blood pressure.
Tunica Externa
The outermost layer is the tunica externa or tunica adventitia, composed entirely of connective fibers and surrounded by an external elastic lamina which functions to anchor vessels with surrounding tissues. The tunica externa is often thicker in veins to prevent collapse of the blood vessel and provide protection from damage since veins may be superficially located.
Structure of the Artery Wall : This diagram of the artery wall indicates the smooth muscle, external elastic membrane, endothelium, internal elastic membrane, tunica externa, tunica media, and tunica intima.
Valve Function
A major structural difference between arteries and veins is the presence of valves. In arteries, the blood is pumped under pressure from the heart, so backflow cannot occur. However, passing through the capillary network results in a decrease in blood pressure, meaning that backflow of blood is possible in veins. To counteract this, veins contain numerous one-direction valves that prevent backflow.


11.7: Putting It Together- Teamwork and Communication
Synthesis
What did it take for these eight people to jump out of a perfectly good airplane and join hands to form a figure eight? Yes, nerves of steel and a measure of pure insanity. But it also took something else—the very thing you learned about in this module: teamwork and communication. As for these skydivers, the consequences of poor teamwork and faulty communication can be serious and even deadly. Defective parts can wind up in automobiles and airplanes, the wrong medications can be given to patients in a hospital, food can be contaminated . . . all as a result of poor teamwork and communication. Understanding the ways in which people communicate and overcome potential barriers can help you be a more effective communicator and a better team member. Moreover, the skills you’ve learned in this module are not only important in business—they’re useful in skydiving and life.
Summary
In this module you learned about the importance of teamwork and communication in business. Below is a summary of the key points that were covered.
Teams
Teams are groups of individuals with complementary skills who come together to achieve a specific goal. Teams can be manager-led, self-directed, cross-functional, or even virtual. Companies use teams because they are an effective means of achieving objectives, and they bring increased efficiency to operations.
Team Development and Success
When teams are formed they evolve from individuals into a cohesive unit. The stages of team development are forming, storming, norming, performing, and adjourning.
What differentiates a successful team from an unsuccessful one? Some of the hallmarks of successful teams are the following: the members trust one another, common goals, defined team roles and responsibilities, good communication, and group cohesion.
Effective Communication and Barriers
Effective communications are thoughtful, clear, specific, brief, and timely. “Getting one’s message across” can be tricky and challenging due to barriers that impede communication. Among the barriers to effective communication are filtering, bias, jargon, language and cultural differences, the chain of command, physical disabilities, and lack of trust.
Communication Channels, Flows, and Networks
Communication involves a sender, a message, and a receiver. The form a message takes is called a channel. Communication can occur between different kinds of senders and receivers within (and outside of) an organization. Communication can flow upward, downward, horizontally, diagonally, and externally. It can also flow through different networks, both informal and informal.
Electronic Communication
The rise of information technology that makes business communication faster and more efficient brings unique ethical challenges and risks. Businesses must take steps to keep employee and customer data safe; they must also establish security measures to protect against cyber threats such as malware, hacking, and theft.


Chapter 15
(a)
(b)
(c)
(d)
(e)
There is no change. A solid has an activity of 1 whether there is a little or a lot.
The solubility of silver bromide at the new temperature must be known. Normally the solubility increases and some of the solid silver bromide will dissolve.
CaF 2 , MnCO 3 , and ZnS
(a)
(b)
(c)
(d)
(a)1.77 10 –7 ; (b) 1.6 10 –6 ; (c) 2.2 10 –9 ; (d) 7.91 10 –22
(a) 2 10 –2 M ; (b) 1.5 10 –3 M ; (c) 2.27 10 –9 M ; (d) 2.2 10 –10 M
(a) 6.4 10
−9
M
= [Ag
+
], [Cl
−
] = 0.025
M
. Check: an insignificant change;
(b) 2.2 10
−5
M
= [Ca
2
+
], [F
−
] = 0.0013
M
. Check: This value is less than 5% and can be ignored.
(c) 0.2238
M
= [Ag
+
] = 7.4 10
–3
M
. Check: the condition is satisfied.
(d) [OH
–
] = 2.8 10
–3
M
; 5.7 10
−12
M
= [Zn
2+
]. Check:
x
is less than 5% of [OH
–
] and is, therefore, negligible.
(a) [Cl
–
] = 7.6 10
−3
M
Check:
This value is too large to drop
x
. Therefore solve by using the quadratic equation:
[Ti
+
] = 3.1 10
–2
M
[Cl
–
] = 6.1 10
–3
(b) [Ba
2
+
] = 7.7 10
–4
M
Check:
Therefore, the condition is satisfied.
[Ba
2
+
] = 7.7 10
–4
M
[F
–
] = 0.0321
M
;
(c) Mg(NO
3
)
2
= 0.02444
M
Check:
The condition is satisfied; the above value is less than 5%.
[Mg
2
+
] = 0.0244
M
(d) [OH
–
] = 0.0501
M
[Ca
2
+
] = 3.15 10
–3
Check:
This value is greater than 5%, so a more exact method, such as successive approximations, must be used.
[Ca
2+
] = 2.8 10
–3
M
[OH
–
] = 0.053 10
–2
M
The changes in concentration are greater than 5% and thus exceed the maximum value for disregarding the change.
CaSO 4 ∙2H 2 O is the most soluble Ca salt in mol/L, and it is also the most soluble Ca salt in g/L.
4.8 10 –3 M = = [Ca 2+ ]; Since this concentration is higher than 2.60 10 –3 M , “gyp” water does not meet the standards.
Mass (CaSO 4 ·2H 2 O) = 0.72 g/L
(a) [Ag + ] = [I – ] = 1.3 10 –5 M ; (b) [Ag + ] = 2.88 10 –2 M , = 1.44 10 –2 M ; (c) [Mn 2+ ] = 3.7 10 –5 M , [OH – ] = 7.4 10 –5 M ; (d) [Sr 2+ ] = 4.3 10 –2 M , [OH – ] = 8.6 10 –2 M ; (e) [Mg 2+ ] = 1.3 10 –4 M , [OH – ] = 2.6 10 –4 M .
(a) 1.45 10 –4 ; (b) 8.2 10 –55 ; (c) 1.35 10 –4 ; (d) 1.18 10 –5 ; (e) 1.08 10 –10
(a) CaCO 3 does precipitate. (b) The compound does not precipitate. (c) The compound does not precipitate. (d) The compound precipitates.
3.03 10 −7 M
9.2 10 −13 M
[Ag + ] = 1.8 10 –3 M
6.3 10 –4
(a) 2.25 L; (b) 7.2 10 –7 g
100% of it is dissolved
(a) and Cu 2+ : Add (b) and Cl – : Add Ba 2+ . (c) Hg 2+ and Co 2+ : Add S 2– . (d) Zn 2+ and Sr 2+ : Add OH – until [OH – ] = 0.050 M . (e) Ba 2+ and Mg 2+ : Add (f) and OH – : Add Ba 2+ .
AgI will precipitate first.
1.5 10 −12 M
3.99 kg
(a) 3.1 10 –11 ; (b) [Cu 2+ ] = 2.6 10 –3 ; = 5.3 10 –3
1.8 10 –5 g Pb(OH) 2
1.23 10 −3 g Mg(OH) 2
MnCO 3 will form first since it has the smallest K sp value among these homologous compounds and is therefore the least soluble. MgCO 3 •3H 2 O will be the last to precipitate since it has the largest K_sp value and is the most soluble. K sp value.
when the amount of solid is so small that a saturated solution is not produced
1.8 10 –5 M
5 10 23
[Cd 2+ ] = 9.5 10 –5 M ; [CN – ] = 3.8 10 –4 M
[Co 3+ ] = 3.0 10 –6 M ; [NH 3 ] = 1.8 10 –5 M
1.3 g
0.79 g
(a)
(b)
(c)
(d)
(e)
(a)
(b)
(c)
(d)
0.0281 g
(a) (b) The electronic and molecular shapes are the same—both tetrahedral. (c) The tetrahedral structure is consistent with sp 3 hybridization.
0.014 M
7.2 10 –15 M
4.4 10 −22 M
[OH − ] = 4.5 10 −6 ; [Al 3+ ] = 2 10 –16 (molar solubility)
; [Ba 2+ ] = 4.7 10 –7 (molar solubility)
[OH – ] = 7.6 10 −3 M ; [Pb 2+ ] = 2.1 10 –11 (molar solubility)
7.66
(a)
K
sp
= [Mg
2+
][F
–
]
2
= (1.21 10
–3
)(2 1.21 10
–3
)
2
= 7.09 10
–9
(b) 7.09 10
–7
M
(c) Determine the concentration of Mg
2+
and F
–
that will be present in the final volume. Compare the value of the ion product [Mg
2+
][F
–
]
2
with
K
sp
. If this value is larger than
K
sp
, precipitation will occur.
0.1000 L 3.00 10
–3
M
Mg(NO
3
)
2
= 0.3000 L
M
Mg(NO
3
)
2
M
Mg(NO
3
)
2
= 1.00 10
–3
M
0.2000 L 2.00 10
–3
M
NaF = 0.3000 L
M
NaF
M
NaF = 1.33 10
–3
M
ion product = (1.00 10
–3
)(1.33 10
–3
)
2
= 1.77 10
–9
This value is smaller than
K
sp
, so no precipitation will occur.
(d) MgF
2
is less soluble at 27 °C than at 18 °C. Because added heat acts like an added reagent, when it appears on the product side, the Le Chatelier’s principle states that the equilibrium will shift to the reactants’ side to counter the stress. Consequently, less reagent will dissolve. This situation is found in our case. Therefore, the reaction is exothermic.
BaF 2 , Ca 3 (PO 4 ) 2 , ZnS; each is a salt of a weak acid, and the from perchloric acid reduces the equilibrium concentration of the anion, thereby increasing the concentration of the cations
Effect on amount of solid CaHPO 4 , [Ca 2+ ], [OH – ]: (a) increase, increase, decrease; (b) decrease, increase, decrease; (c) no effect, no effect, no effect; (d) decrease, increase, decrease; (e) increase, no effect, no effect


8.7.2: Crime and Violence
People who witness or who are victims of crime and violence - particularly where they live - are at risk for a host of health issues. Certainly there is a risk of injury or death from violence itself, but also for stress and post-traumatic stress disorder (PTSD). Other health issues related to stress are also higher risk, like hypertension, stroke, asthma, and mental health disorders. Crime can include property crimes such as break-ins, robberies, and vandalism. Violence encompasses physical assault, child or intimate partner abuse, elder abuse, and gun violence - including homicides and suicides. The long-term impact of violence on children was also discussed earlier with ACE’s, but anyone of any age can have adverse health effects from witnessing or even hearing about violence ( Crime and Violence - Healthy People 2030 , n.d.).
Firearm injuries and deaths are a significant public health problem in the United States, and disproportionately impact certain populations. Over 85% of gun death or injury victims are men. Gun homicide rates are highest among teens and young adults, and especially Black, Hispanic or AI/AN young people ( Fast Facts: Firearm Violence and Injury Prevention , 2023). In recent years, firearm deaths (including accidents, homicides, and suicides) became the leading cause of death for children between 1-17 years old - even outpacing car accidents and childhood cancers. Accounting for 20% of the deaths of children in America in 2021, this far outpaced other wealthy nations like Canada, several countries in Europe, and Japan ( Child and Teen Firearm Mortality in the U.S. and Peer Countries , 2023).
There are structural conditions that place minoritized and impoverished communities at higher risk for crime and violence, and others that offer protective benefits to more affluent neighborhoods. For example, higher income inequality and lower economic opportunities are associated with a higher risk of violence when comparing different neighborhoods. Families who have to move often because of housing instability have less time to create social ties with the neighborhood, thus decreasing social capital and social cohesion (see this topic below). Although there may be more crime in many minoritized neighborhoods, there is also less trust in the criminal justice system: these neighborhoods are often overpoliced and experience more police misconduct, including police brutality. Police violence is a leading cause of death for young Black men (P. A. Braveman et al., 2022). The lifetime risk of being killed by police is highest for Black men, followed by American Indian/Alaskan Native men, and Latinos (Edwards et al., 2019). Distrust in the police is commonly precipitated by police misconduct and over-policing in minoritized communities, which may also contribute to increased violence (Armstead et al., 2019).


6.3: Business Ethics
Learning Objectives
- Explain how ethics relates to the business and the individual
- Explain the role of managers in setting standards for ethical behavior
Building Business Ethics
Governments use laws and regulations to point business behavior in what they perceive to be beneficial directions. Business ethics implicitly regulates behavior that lies beyond governmental control. Business ethics refers to contemporary standards or sets of values that govern the actions and behavior of individuals in the business organization and the actions of the business itself. It applies to all aspects of business conduct and is relevant to the conduct of individuals and entire organizations. [1] Corporations and professional organizations, particularly licensing boards, will usually have a written “Code of Ethics” that governs standards of professional conduct expected of all in the field.
Individual and Corporate Ethics
As the definition of business ethics above suggests, business ethics is a broad term that applies to the behavior of the individuals who work at a business as well as the actions of the business itself. There is a narrower term, “corporate ethics,” that is used for this second area of the actions of a business. Corporate ethics express the values of an organization to its internal and external stakeholders. Corporate ethics has become such an important concern that companies such as Covalence EthicalQuote have cropped up to monitor the ethical behavior of businesses. These private firms track the world’s largest companies in areas such as corporate social responsibility, ethics, and sustainability, and then provide ratings, news, and data to investors and the general public. Web sites such as Ethical Consumer promote “ethical consumerism” to help consumers act in the marketplace in ways that are consistent with their ethics. Year after year, companies such as Nestle, Bayer, and Monsanto grace the top of the “worst of the worst” lists.
But it’s not all grim news or tattling when it comes to business ethics. For example, the Scottsdale, Arizona-based Ethisphere Institute—an organization focused on gauging ethical business practices—publishes a list of the “World’s Most Ethical Companies” on an annual basis. The overall goal of Ethisphere’s rankings is to reward organizations with good practices and offer a model—and actionable advice—on how corporate entities should conduct themselves, says chief marketing and strategy officer, Tia Smallwood. “The papers are filled with scandals and companies that made judgment errors, that made policy errors or that don’t have good practices in place to handle things like non-retaliation or transparency or open reporting, or have had a crisis and handled it poorly,” she said. “But there a lot of companies that are really trying to do things the right way.” Notable call-outs this year are firms that have been honored every year of the list’s existence. Those include Aflac, Fluor Corporation, GE, Kao Corporation (Japan), Milliken & Company, Starbucks and UPS. [2]
Encouraging Ethical Behavior
How, then, do businesses encourage and support ethical behavior? Often the ethical tone of a business is set by organizational leadership.
Consider the following observation by the Ethics and Compliance Initiative (ECI) on the results of the National Business Ethics survey:
"Managers – those expected to act as role models or enforce discipline–are responsible for a large share of workplace misconduct (60 percent) and senior managers are more likely than lower-level managers to break rules. Surveyed employees said that members of management are responsible for six of every ten instances of misconduct and they pointed the finger at senior managers in 24 percent of observed rule breaking. Middle managers were identified as the culprit 19 percent of the time and first-line supervisors were identified as bad actors 17 percent of the time. [3] "
If a company is looking for ways to boost or ensuring ethical behavior in an organization, this is an interesting and alarming finding. In a supplemental report on Ethical Leadership, ECI reports that employees at all sizes of companies draw conclusions about their leaders’ character primarily on the basis of the following:
- The overall character of their leaders as experienced through personal interactions;
- How senior managers handle crises; and
- The policies and procedures adopted by senior leaders to manage the company.
Employees want to know, for example, whether leaders treat lower level employees with dignity and respect, share credit when good things happen, and uphold standards even when it reduces revenues and profits. They watch to see whether leaders are steady in crisis, hold themselves accountable or, alternatively, shift blame to others. Workers also look at day-to-day management decisions to gauge whether ethical behavior is recognized and rewarded, or whether praise and promotions go to workers who bend the rules. [4]
These findings suggest the important role that executives play in building ethical organizations—ethics and integrity tend to start (or fail) at the top and trickle down.
The Role of Executives and Managers in Setting Ethical Standards
When executives establish specific, measurable objectives for the company, those objectives determine where people will focus their time and effort. When the objectives cannot be met and there are dire personal consequences for failure, such conditions can lead to the compromise of ethics and standards. In the National Business Ethics Survey, 70 percent of employees identified pressure to meet unrealistic business objectives as most likely to cause them to compromise their ethical standards, and 75 percent identified either their senior or middle management as the primary source of pressure they feel to compromise the standards of their organizations.
Former Volkswagon CEO, Martin Winterkorn is on the right
In the Volkswagen case, internal investigations have questioned how both the company culture and the behavior of former CEO Martin Winterkorn contributed to a systemic ethical breach. Like many chief executives, Martin Winterkorn was a demanding boss who didn’t like failure, but critics say the pressure on managers at Volkswagen was unusual, which may go some way toward explaining the carmaker’s crisis. When he became CEO in 2007, Winterkorn set an objective to make VW the world’s biggest carmaker, which would require tremendous growth in the highly competitive U.S. car market. In the years since, VW has nearly doubled it global annual sales to 10 million cars and its revenue to $225 billion. In early 2015, VW finally approached its goal, selling marginally more vehicles than the world’s number-one automaker, Toyota of Japan. One former sales executive said that the pressure soared under the target. “If you didn’t like it, you moved of your own accord or you were performance-managed out of the business,” he said. [5]
In describing a Winterkorn’s leadership style, a former VW executive confidentially told Reuters New Agency, “There was always a distance, a fear and a respect . . .  If you presented bad news, those were the moments that it could become quite unpleasant and loud and quite demeaning.”
A week after U.S. regulators revealed the company’s cheating, Bernd Osterloh, the employee representative on VW’s supervisory board, sent a letter to VW staff suggesting the change that was needed: “We need in the future a climate in which problems aren’t hidden but can be openly communicated to superiors,” said Osterloh. “We need a culture in which it’s possible and permissible to argue with your superior about the best way to go.” [6]
In Fortune magazine, Dr. Paul Argenti suggested, “Rather than playing the blame game, executives should ask if pressures to grow at all costs might have created dishonest employees.” [7]
It seems likely that aggressive corporate objectives (and more specifically marketing objectives related to market share) played a contributing role in the Volkswagen ethics scandal. Moreover, when executives set aggressive goals, it becomes more important to cultivate communication channels to openly address issues. This was obviously not the case at Volkswagon.
Executives play an important role in creating company policies on ethics—and by visibly following and upholding them. As the survey data cited above suggest, employees look to executives to decide whether standards-of-business-conduct policies should be observed and respected. When executives bend the rules or turn a blind eye to bad behavior, the policies lose value and executives lose the respect of employees. This opens the door to a range of unanticipated issues, as employees look to ethical norms outside stated policy and beyond the executives’ control.
Internal promotions send very strong signals about what is important to a company. When the company hires an employee from a different company, she is likely not well known by most employees. If the company promotes an employee who is already working at the company, others know him and understand what he has done to deserve the promotion. If the company promotes individuals to management positions when they have displayed questionable ethics in the workplace, it creates two issues. First, it creates a level of managers who are more likely to encourage their employees to achieve business results at any cost, even when ethics are compromised. Second, it sends a message to all employees that business results are more important than ethics.
Company Codes of Ethics and Codes of Practice
An increasing number of companies requires employees to attend trainings regarding business conduct. These typically include discussions of the company’s policies, specific case studies, and legal requirements. Some companies even require their employees to sign agreements stating that they will abide by the company’s rules of conduct.
As part of more comprehensive compliance and ethics programs, many companies have formulated internal policies pertaining to the ethical conduct of employees. They are generally documented in one of two ways:
- Corporate Code of Ethics . A code of ethics begins by setting out the values that underpin the code and describes a company’s obligation to its stakeholders. The code is publicly available and addressed to anyone with an interest in the company’s activities and the way it does business. It includes details of how the company plans to implement its values and vision, as well as guidance to staff on ethical standards and how to achieve them. It is hoped that having such a policy will lead to greater ethical awareness, consistency in application, and the avoidance of ethical disasters.
- Code of Practice. A code of practice is adopted by a profession or by a governmental or nongovernmental organization to regulate that profession. A code of practice may be styled as a code of professional responsibility, and it will discuss difficult issues, difficult decisions that will often need to be made, and provide a clear account of what behavior is considered “ethical” or “correct” or “right” in the circumstances. In a membership context, failure to comply with a code of practice can result in expulsion from the professional organization.
Richard DeGeorge, author of Business Ethics , has this to say about the importance of maintaining a corporate code:
"Corporate codes have a certain usefulness and there are several advantages to developing them. First, the very exercise of doing so in itself is worthwhile, especially if it forces a large number of people in the firm to think through, in a fresh way, their mission and the important obligations they as a group and as individuals have to the firm, to each other, to their clients and customers, and to society as a whole. Second, once adopted, a code can be used to generate continuing discussion and possible modification to the code. Third, it could help to inculcate in new employees at all levels the perspective of responsibility, the need to think in moral terms about their actions, and the importance of developing the virtues appropriate to their position. [8] "
Beyond establishing policies or codes that guide the ethical behavior of the company or employees, many companies are assessing the environmental factors that can lead employees to engage in unethical conduct. A competitive business environment may call for unethical behavior. For example, lying has become the norm in fields such as stock and security trading. Sometimes there is disconnection between the company’s code of ethics and the company’s actual practices. Thus, whether or not such conduct is explicitly sanctioned by management, at worst, this makes the policy duplicitous, and, at best, it is merely a marketing tool.
Not everyone supports corporate policies that govern ethical conduct. Some claim that ethical problems are better dealt with by relying upon employees to use their own judgment. Others believe that corporate ethics policies are primarily rooted in utilitarian concerns, and that they are mainly to limit the company’s legal liability, or to curry public favor by giving the appearance of being a good corporate citizen. Ideally, the company will avoid a lawsuit because its employees will follow the rules. Should a lawsuit occur, the company can claim that the problem wouldn’t have arisen if the employee had followed the code properly.
- "Business Ethics (Stanford Encyclopedia of Philosophy)" . Plato.stanford.edu. 2008-04-16. Retrieved 2013-06-04. ↵
- http://www.forbes.com/sites/karstenstrauss/2016/03/09/the-worlds-most-ethical-companies-2016/#1a81a32673dcontent here. ↵
- www.ethics.org/newsite/resear...orts/nbes-2013 ↵
- www.ethics.org/newsite/resear...cal-leadership ↵
- http://www.reuters.com/article/us-volkswagen-emissions-culture-idUSKCN0S40MT20151010 ↵
- http://www.reuters.com/article/us-volkswagen-emissions-culture-idUSKCN0S40MT20151010 ↵
- http://fortune.com/2015/10/13/biggest-culprit-in-volkswagen-emissions-scandal/ ↵
- DeGeorge, Richard. Business Ethics. Prentice Hall. pp. 207–208 ↵