19.2: Heart Anatomy
By the end of this section, you will be able to:
- Describe the location and position of the heart within the body cavity
- Describe the internal and external anatomy of the heart
- Identify the tissue layers of the heart
- Relate the structure of the heart to its function as a pump
- Compare systemic circulation to pulmonary circulation
- Identify the veins and arteries of the coronary circulation system
- Trace the pathway of oxygenated and deoxygenated blood thorough the chambers of the heart
The vital importance of the heart is obvious. If one assumes an average rate of contraction of 75 contractions per minute, a human heart would contract approximately 108,000 times in one day, more than 39 million times in one year, and nearly 3 billion times during a 75-year lifespan. Each of the major pumping chambers of the heart ejects approximately 70 mL blood per contraction in a resting adult. This would be equal to 5.25 liters of fluid per minute and approximately 14,000 liters per day. Over one year, that would equal 10,000,000 liters or 2.6 million gallons of blood sent through roughly 60,000 miles of vessels. In order to understand how that happens, it is necessary to understand the anatomy and physiology of the heart.
Location of the Heart
The human heart is located within the thoracic cavity, medially between the lungs in the space known as the mediastinum. Figure \(\PageIndex{1}\) shows the position of the heart within the thoracic cavity. Within the mediastinum, the heart is separated from the other mediastinal structures by a tough membrane known as the pericardium, or pericardial sac, and sits in its own space called the pericardial cavity . The dorsal surface of the heart lies near the bodies of the vertebrae, and its anterior surface sits deep to the sternum and costal cartilages. The great veins, the superior and inferior venae cavae, and the great arteries, the aorta and pulmonary trunk, are attached to the superior surface of the heart, called the base. The base of the heart is located at the level of the third costal cartilage, as seen in Figure \(\PageIndex{1}\). The inferior tip of the heart, the apex, lies just to the left of the sternum between the junction of the fourth and fifth ribs near their articulation with the costal cartilages. The right side of the heart is deflected anteriorly, and the left side is deflected posteriorly. It is important to remember the position and orientation of the heart when placing a stethoscope on the chest of a patient and listening for heart sounds, and also when looking at images taken from a midsagittal perspective. The slight deviation of the apex to the left is reflected in a depression in the medial surface of the inferior lobe of the left lung, called the cardiac notch .
Everyday Connection
CPR
The position of the heart in the torso between the vertebrae and sternum (see Figure \(\PageIndex{1}\) for the position of the heart within the thorax) allows for individuals to apply an emergency technique known as cardiopulmonary resuscitation (CPR) if the heart of a patient should stop. By applying pressure with the flat portion of one hand on the sternum in the area between the line at T4 and T9 (Figure \(\PageIndex{2}\)), it is possible to manually compress the blood within the heart enough to push some of the blood within it into the pulmonary and systemic circuits. This is particularly critical for the brain, as irreversible damage and death of neurons occur within minutes of loss of blood flow. Current standards call for compression of the chest at least 5 cm deep and at a rate of 100 compressions per minute, a rate equal to the beat in “Staying Alive,” recorded in 1977 by the Bee Gees. If you are unfamiliar with this song, a version is available on www.youtube.com. At this stage, the emphasis is on performing high-quality chest compressions, rather than providing artificial respiration. CPR is generally performed until the patient regains spontaneous contraction or is declared dead by an experienced healthcare professional.
When performed by untrained or overzealous individuals, CPR can result in broken ribs or a broken sternum, and can inflict additional severe damage on the patient. It is also possible, if the hands are placed too low on the sternum, to manually drive the xiphoid process into the liver, a consequence that may prove fatal for the patient. Proper training is essential. This proven life-sustaining technique is so valuable that virtually all medical personnel as well as concerned members of the public should be certified and routinely recertified in its application. CPR courses are offered at a variety of locations, including colleges, hospitals, the American Red Cross, and some commercial companies. They normally include practice of the compression technique on a mannequin.
Interactive Link
Visit the American Heart Association website to help locate a course near your home in the United States. There are also many other national and regional heart associations that offer the same service, depending upon the location.
Shape and Size of the Heart
The shape of the heart is similar to a pinecone, rather broad at the superior surface and tapering to the apex (see Figure \(\PageIndex{1}\)). A typical heart is approximately the size of your fist: 12 cm (5 in) in length, 8 cm (3.5 in) wide, and 6 cm (2.5 in) in thickness. Given the size difference between most members of the sexes, the weight of a female heart is approximately 250–300 grams (9 to 11 ounces), and the weight of a male heart is approximately 300–350 grams (11 to 12 ounces). The heart of a well-trained athlete, especially one specializing in aerobic sports, can be considerably larger than this. Cardiac muscle responds to exercise in a manner similar to that of skeletal muscle. That is, exercise results in the addition of protein myofilaments that increase the size of the individual cells without increasing their numbers, a concept called hypertrophy. Hearts of athletes can pump blood more effectively at lower rates than those of nonathletes. Enlarged hearts are not always a result of exercise; they can result from pathologies, such as hypertrophic cardiomyopathy . The cause of an abnormally enlarged heart muscle is unknown, but the condition is often undiagnosed and can cause sudden death in apparently otherwise healthy young people.
Chambers and Circulation through the Heart
The human heart consists of four chambers: The left side and the right side each have one atrium and one ventricle . Each of the upper chambers, the right atrium (plural = atria) and the left atrium, acts as a receiving chamber and contracts to push blood into the lower chambers, the right ventricle and the left ventricle. The ventricles serve as the primary pumping chambers of the heart, propelling blood to the lungs or to the rest of the body.
There are two distinct but linked circuits in the human circulation called the pulmonary and systemic circuits. Although both circuits transport blood and everything it carries, we can initially view the circuits from the point of view of gases. The pulmonary circuit transports blood to and from the lungs, where it picks up oxygen and delivers carbon dioxide for exhalation. The systemic circuit transports oxygenated blood to virtually all of the tissues of the body and returns relatively deoxygenated blood and carbon dioxide to the heart to be sent back to the pulmonary circulation.
The right ventricle pumps deoxygenated blood into the pulmonary trunk , which leads toward the lungs and bifurcates into the left and right pulmonary arteries . These vessels in turn branch many times before reaching the pulmonary capillaries , where gas exchange occurs: Carbon dioxide exits the blood and oxygen enters. The pulmonary trunk arteries and their branches are the only arteries in the post-natal body that carry relatively deoxygenated blood. Highly oxygenated blood returning from the pulmonary capillaries in the lungs passes through a series of vessels that join together to form the pulmonary veins —the only post-natal veins in the body that carry highly oxygenated blood. The pulmonary veins conduct blood into the left atrium, which pumps the blood into the left ventricle, which in turn pumps oxygenated blood into the aorta and on to the many branches of the systemic circuit. Eventually, these vessels will lead to the systemic capillaries, where exchange with the tissue fluid and cells of the body occurs. In this case, oxygen and nutrients exit the systemic capillaries to be used by the cells in their metabolic processes, and carbon dioxide and waste products will enter the blood.
The blood exiting the systemic capillaries is lower in oxygen concentration than when it entered. The capillaries will ultimately unite to form venules, joining to form ever-larger veins, eventually flowing into the two major systemic veins, the superior vena cava and the inferior vena cava , which return blood to the right atrium. The blood in the superior and inferior venae cavae flows into the right atrium, which pumps blood into the right ventricle. This process of blood circulation continues as long as the individual remains alive. Understanding the flow of blood through the pulmonary and systemic circuits is critical to all health professions (Figure \(\PageIndex{3}\)).
Membranes, Surface Features, and Layers
Our exploration of more in-depth heart structures begins by examining the membrane that surrounds the heart, the prominent surface features of the heart, and the layers that form the wall of the heart. Each of these components plays its own unique role in terms of function.
Membranes
The membrane that directly surrounds the heart and defines the pericardial cavity is called the pericardium or pericardial sac . It also surrounds the “roots” of the major vessels, or the areas of closest proximity to the heart. The pericardium, which literally translates as “around the heart,” consists of two distinct sublayers: the sturdy outer fibrous pericardium and the inner serous pericardium. The fibrous pericardium is made of tough, dense connective tissue that protects the heart and maintains its position in the thorax. The more delicate serous pericardium consists of two layers: the parietal pericardium, which is fused to the fibrous pericardium, and an inner visceral pericardium, or epicardium , which is fused to the heart and is part of the heart wall. The pericardial cavity, filled with lubricating serous fluid, lies between the epicardium and the pericardium.
In most organs within the body, visceral serous membranes such as the epicardium are microscopic. However, in the case of the heart, it is not a microscopic layer but rather a macroscopic layer, consisting of a simple squamous epithelium called a mesothelium , reinforced with loose, irregular, or areolar connective tissue that attaches to the pericardium. This mesothelium secretes the lubricating serous fluid that fills the pericardial cavity and reduces friction as the heart contracts. Figure \(\PageIndex{4}\) illustrates the pericardial membrane and the layers of the heart.
Disorders of the...
Heart: Cardiac Tamponade
If excess fluid builds within the pericardial space, it can lead to a condition called cardiac tamponade, or pericardial tamponade. With each contraction of the heart, more fluid—in most instances, blood—accumulates within the pericardial cavity. In order to fill with blood for the next contraction, the heart must relax. However, the excess fluid in the pericardial cavity puts pressure on the heart and prevents full relaxation, so the chambers within the heart contain slightly less blood as they begin each heart cycle. Over time, less and less blood is ejected from the heart. If the fluid builds up slowly, as in hypothyroidism, the pericardial cavity may be able to expand gradually to accommodate this extra volume. Some cases of fluid in excess of one liter within the pericardial cavity have been reported. Rapid accumulation of as little as 100 mL of fluid following trauma may trigger cardiac tamponade. Other common causes include myocardial rupture, pericarditis, cancer, or even cardiac surgery. Removal of this excess fluid requires insertion of drainage tubes into the pericardial cavity. Premature removal of these drainage tubes, for example, following cardiac surgery, or clot formation within these tubes are causes of this condition. Untreated, cardiac tamponade can lead to death.
Surface Features of the Heart
Inside the pericardium, the surface features of the heart are visible, including the four chambers. There is a superficial leaf-like extension of the atria near the superior surface of the heart, one on each side, called an auricle —a name that means “ear like”—because its shape resembles the external ear of a human (Figure \(\PageIndex{5}\)). Auricles are relatively thin-walled structures that can fill with blood and empty into the atria or upper chambers of the heart. You may also hear them referred to as atrial appendages. Also prominent is a series of fat-filled grooves, each of which is known as a sulcus (plural = sulci), along the superior surfaces of the heart. Major coronary blood vessels are located in these sulci. The deep coronary sulcus is located between the atria and ventricles. Located between the left and right ventricles are two additional sulci that are not as deep as the coronary sulcus. The anterior interventricular sulcus is visible on the anterior surface of the heart, whereas the posterior interventricular sulcus is visible on the posterior surface of the heart. Figure \(\PageIndex{5}\) illustrates anterior and posterior views of the surface of the heart.
Layers
The wall of the heart is composed of three layers of unequal thickness. From superficial to deep, these are the epicardium, the myocardium, and the endocardium (see Figure \(\PageIndex{4}\)). The outermost layer of the wall of the heart is also the innermost layer of the pericardium, the epicardium, or the visceral pericardium discussed earlier.
The middle and thickest layer is the myocardium , made largely of cardiac muscle cells. It is built upon a framework of collagenous fibers, plus the blood vessels that supply the myocardium and the nerve fibers that help regulate the heart. It is the contraction of the myocardium that pumps blood through the heart and into the major arteries. The muscle pattern is elegant and complex, as the muscle cells swirl and spiral around the chambers of the heart. They form a figure 8 pattern around the atria and around the bases of the great vessels. Deeper ventricular muscles also form a figure 8 around the two ventricles and proceed toward the apex. More superficial layers of ventricular muscle wrap around both ventricles. This complex swirling pattern allows the heart to pump blood more effectively than a simple linear pattern would. Figure \(\PageIndex{6}\) illustrates the arrangement of muscle cells.
Although the ventricles on the right and left sides pump the same amount of blood per contraction, the muscle of the left ventricle is much thicker and better developed than that of the right ventricle. In order to overcome the high resistance required to pump blood into the long systemic circuit, the left ventricle must generate a great amount of pressure. The right ventricle does not need to generate as much pressure, since the pulmonary circuit is shorter and provides less resistance. Figure \(\PageIndex{7}\) illustrates the differences in muscular thickness needed for each of the ventricles.
The innermost layer of the heart wall, the endocardium , is joined to the myocardium with a thin layer of connective tissue. The endocardium lines the chambers where the blood circulates and covers the heart valves. It is made of simple squamous epithelium called endothelium , which is continuous with the endothelial lining of the blood vessels (see Figure \(\PageIndex{4}\)).
Once regarded as a simple lining layer, recent evidence indicates that the endothelium of the endocardium and the coronary capillaries may play active roles in regulating the contraction of the muscle within the myocardium. The endothelium may also regulate the growth patterns of the cardiac muscle cells throughout life, and the endothelins it secretes create an environment in the surrounding tissue fluids that regulates ionic concentrations and states of contractility. Endothelins are potent vasoconstrictors and, in a normal individual, establish a homeostatic balance with other vasoconstrictors and vasodilators.
Internal Structure of the Heart
Recall that the heart’s contraction cycle follows a dual pattern of circulation—the pulmonary and systemic circuits—because of the pairs of chambers that pump blood into the circulation. In order to develop a more precise understanding of cardiac function, it is first necessary to explore the internal anatomical structures in more detail.
Septa of the Heart
The word septum is derived from the Latin for “something that encloses;” in this case, a septum (plural = septa) refers to a wall or partition that divides the heart into chambers. The septa are physical extensions of the myocardium lined with endocardium. Located between the two atria is the interatrial septum . Normally in an adult heart, the interatrial septum bears an oval-shaped depression known as the fossa ovalis , a remnant of an opening in the fetal heart known as the foramen ovale . The foramen ovale allowed blood in the fetal heart to pass directly from the right atrium to the left atrium, allowing some blood to bypass the pulmonary circuit. Within seconds after birth, a flap of tissue known as the septum primum that previously acted as a valve closes the foramen ovale and establishes the typical cardiac circulation pattern.
Between the two ventricles is a second septum known as the interventricular septum . Unlike the interatrial septum, the interventricular septum is normally intact after its formation during fetal development. It is substantially thicker than the interatrial septum, since the ventricles generate far greater pressure when they contract.
The septum between the atria and ventricles is known as the atrioventricular septum . It is marked by the presence of four openings that allow blood to move from the atria into the ventricles and from the ventricles into the pulmonary trunk and aorta. Located in each of these openings between the atria and ventricles is a valve , a specialized structure that ensures one-way flow of blood. The valves between the atria and ventricles are known generically as atrioventricular valves . The valves at the openings that lead to the pulmonary trunk and aorta are known generically as semilunar valves . The interventricular septum is visible in Figure \(\PageIndex{8}\). In this figure, the atrioventricular septum has been removed to better show the bicuspid and tricuspid valves; the interatrial septum is not visible, since its location is covered by the aorta and pulmonary trunk. Since these openings and valves structurally weaken the atrioventricular septum, the remaining tissue is heavily reinforced with dense connective tissue called the cardiac skeleton , or skeleton of the heart. It includes four rings that surround the openings between the atria and ventricles, and the openings to the pulmonary trunk and aorta, and serve as the point of attachment for the heart valves. The cardiac skeleton also provides an important boundary in the heart electrical conduction system.
Disorders of the...
Heart: Heart Defects
One very common form of interatrial septum pathology is patent foramen ovale, which occurs when the septum primum does not close at birth, and the fossa ovalis is unable to fuse. The word patent is from the Latin root patens for “open.” It may be benign or asymptomatic, perhaps never being diagnosed, or in extreme cases, it may require surgical repair to close the opening permanently. As much as 20–25 percent of the general population may have a patent foramen ovale, but fortunately, most have the benign, asymptomatic version. Patent foramen ovale is normally detected by auscultation of a heart murmur (an abnormal heart sound) and confirmed by imaging with an echocardiogram. Despite its prevalence in the general population, the causes of patent ovale are unknown, and there are no known risk factors. In nonlife-threatening cases, it is better to monitor the condition than to risk heart surgery to repair and seal the opening.
Coarctation of the aorta is a congenital abnormal narrowing of the aorta that is normally located at the insertion of the ligamentum arteriosum, the remnant of the fetal shunt called the ductus arteriosus. If severe, this condition drastically restricts blood flow through the primary systemic artery, which is life threatening. In some individuals, the condition may be fairly benign and not detected until later in life. Detectable symptoms in an infant include difficulty breathing, poor appetite, trouble feeding, or failure to thrive. In older individuals, symptoms include dizziness, fainting, shortness of breath, chest pain, fatigue, headache, and nosebleeds. Treatment involves surgery to resect (remove) the affected region or angioplasty to open the abnormally narrow passageway. Studies have shown that the earlier the surgery is performed, the better the chance of survival.
A patent ductus arteriosus is a congenital condition in which the ductus arteriosus fails to close. The condition may range from severe to benign. Failure of the ductus arteriosus to close results in blood flowing from the higher pressure aorta into the lower pressure pulmonary trunk. This additional fluid moving toward the lungs increases pulmonary pressure and makes respiration difficult. Symptoms include shortness of breath (dyspnea), tachycardia, enlarged heart, a widened pulse pressure, and poor weight gain in infants. Treatments include surgical closure (ligation), manual closure using platinum coils or specialized mesh inserted via the femoral artery or vein, or nonsteroidal anti-inflammatory drugs to block the synthesis of prostaglandin E2, which maintains the vessel in an open position. If untreated, the condition can result in congestive heart failure.
Septal defects are not uncommon in individuals and may be congenital or caused by various disease processes. Tetralogy of Fallot is a congenital condition that may also occur from exposure to unknown environmental factors; it occurs when there is an opening in the interventricular septum caused by blockage of the pulmonary trunk, normally at the pulmonary semilunar valve. This allows blood that is relatively low in oxygen from the right ventricle to flow into the left ventricle and mix with the blood that is relatively high in oxygen. Symptoms include a distinct heart murmur, low blood oxygen percent saturation, dyspnea or difficulty in breathing, polycythemia, broadening (clubbing) of the fingers and toes, and in children, difficulty in feeding or failure to grow and develop. It is the most common cause of cyanosis following birth. The term “tetralogy” is derived from the four components of the condition, although only three may be present in an individual patient: pulmonary infundibular stenosis (rigidity of the pulmonary valve), overriding aorta (the aorta is shifted above both ventricles), ventricular septal defect (opening), and right ventricular hypertrophy (enlargement of the right ventricle). Other heart defects may also accompany this condition, which is typically confirmed by echocardiography imaging. Tetralogy of Fallot occurs in approximately 400 out of one million live births. Normal treatment involves extensive surgical repair, including the use of stents to redirect blood flow and replacement of valves and patches to repair the septal defect, but the condition has a relatively high mortality. Survival rates are currently 75 percent during the first year of life; 60 percent by 4 years of age; 30 percent by 10 years; and 5 percent by 40 years.
In the case of severe septal defects, including both tetralogy of Fallot and patent foramen ovale, failure of the heart to develop properly can lead to a condition commonly known as a “blue baby.” Regardless of normal skin pigmentation, individuals with this condition have an insufficient supply of oxygenated blood, which leads to cyanosis, a blue or purple coloration of the skin, especially when active.
Septal defects are commonly first detected through auscultation, listening to the chest using a stethoscope. In this case, instead of hearing normal heart sounds attributed to the flow of blood and closing of heart valves, unusual heart sounds may be detected. This is often followed by medical imaging to confirm or rule out a diagnosis. In many cases, treatment may not be needed. Some common congenital heart defects are illustrated in Figure \(\PageIndex{9}\).
Right Atrium
The right atrium serves as the receiving chamber for blood returning to the heart from the systemic circulation. The two major systemic veins, the superior and inferior venae cavae, and the large coronary vein called the coronary sinus that drains the heart myocardium empty into the right atrium. The superior vena cava drains blood from regions superior to the diaphragm: the head, neck, upper limbs, and the thoracic region. It empties into the superior and posterior portions of the right atrium. The inferior vena cava drains blood from areas inferior to the diaphragm: the lower limbs and abdominopelvic region of the body. It, too, empties into the posterior portion of the atria, but inferior to the opening of the superior vena cava. Immediately superior and slightly medial to the opening of the inferior vena cava on the posterior surface of the atrium is the opening of the coronary sinus. This thin-walled vessel drains most of the coronary veins that return systemic blood from the heart. The majority of the internal heart structures discussed in this and subsequent sections are illustrated in Figure \(\PageIndex{8}\).
While the bulk of the internal surface of the right atrium is smooth, the depression of the fossa ovalis is medial, and the anterior surface demonstrates prominent ridges of muscle called the pectinate muscles . The right auricle also has pectinate muscles. The left atrium does not have pectinate muscles except in the auricle.
The atria receive venous blood on a nearly continuous basis, preventing venous flow from stopping while the ventricles are contracting. While most ventricular filling occurs while the atria are relaxed, they do demonstrate a contractile phase and actively pump blood into the ventricles just prior to ventricular contraction. The opening between the atrium and ventricle is guarded by the tricuspid valve.
Right Ventricle
The right ventricle receives blood from the right atrium through the tricuspid valve. Each flap of the valve is attached to strong strands of connective tissue, the chordae tendineae , literally “tendinous cords,” or sometimes more poetically referred to as “heart strings.” There are several chordae tendineae associated with each of the flaps. They are composed of approximately 80 percent collagenous fibers with the remainder consisting of elastic fibers and endothelium. They connect each of the flaps to a papillary muscle that extends from the inferior ventricular surface. There are three papillary muscles in the right ventricle, called the anterior, posterior, and septal muscles, which correspond to the three sections of the valves.
When the myocardium of the ventricle contracts, pressure within the ventricular chamber rises. Blood, like any fluid, flows from higher pressure to lower pressure areas, in this case, toward the pulmonary trunk and the atrium. To prevent any potential backflow, the papillary muscles also contract, generating tension on the chordae tendineae. This prevents the flaps of the valves from being forced into the atria and regurgitation of the blood back into the atria during ventricular contraction. Figure \(\PageIndex{10}\) shows papillary muscles and chordae tendineae attached to the tricuspid valve.
The walls of the ventricle are lined with trabeculae carneae , ridges of cardiac muscle covered by endocardium. In addition to these muscular ridges, a band of cardiac muscle, also covered by endocardium, known as the moderator band (see Figure 19.9) reinforces the thin walls of the right ventricle and plays a crucial role in cardiac conduction. It arises from the inferior portion of the interventricular septum and crosses the interior space of the right ventricle to connect with the inferior papillary muscle.
When the right ventricle contracts, it ejects blood into the pulmonary trunk, which branches into the left and right pulmonary arteries that carry it to each lung. The superior surface of the right ventricle begins to taper as it approaches the pulmonary trunk. At the base of the pulmonary trunk is the pulmonary semilunar valve that prevents backflow from the pulmonary trunk.
Left Atrium
After exchange of gases in the pulmonary capillaries, blood returns to the left atrium high in oxygen via one of the four pulmonary veins. While the left atrium does not contain pectinate muscles, it does have an auricle that includes these pectinate ridges. Blood flows nearly continuously from the pulmonary veins back into the atrium, which acts as the receiving chamber, and from here through an opening into the left ventricle. Most blood flows passively into the heart while both the atria and ventricles are relaxed, but toward the end of the ventricular relaxation period, the left atrium will contract, pumping blood into the ventricle. This atrial contraction accounts for approximately 20 percent of ventricular filling. The opening between the left atrium and ventricle is guarded by the mitral valve.
Left Ventricle
Recall that, although both sides of the heart will pump the same amount of blood, the muscular layer is much thicker in the left ventricle compared to the right (see Figure \(\PageIndex{7}\)). Like the right ventricle, the left also has trabeculae carneae, but there is no moderator band. The mitral valve is connected to papillary muscles via chordae tendineae. There are two papillary muscles on the left—the anterior and posterior—as opposed to three on the right.
The left ventricle is the major pumping chamber for the systemic circuit; it ejects blood into the aorta through the aortic semilunar valve.
Heart Valve Structure and Function
A transverse section through the heart slightly above the level of the atrioventricular septum reveals all four heart valves along the same plane (Figure \(\PageIndex{11}\)). The valves ensure unidirectional blood flow through the heart. Between the right atrium and the right ventricle is the right atrioventricular valve , or tricuspid valve . It typically consists of three flaps, or leaflets, made of endocardium reinforced with additional connective tissue. The flaps are connected by chordae tendineae to the papillary muscles, which control the opening and closing of the valves.
Emerging from the right ventricle at the base of the pulmonary trunk is the pulmonary semilunar valve, or the pulmonary valve ; it is also known as the pulmonic valve or the right semilunar valve. The pulmonary valve is comprised of three small flaps of endothelium reinforced with connective tissue. When the ventricle relaxes, the pressure differential causes blood to flow back into the ventricle from the pulmonary trunk. This flow of blood fills the pocket-like flaps of the pulmonary valve, causing the valve to close and producing an audible sound. Unlike the atrioventricular valves, there are no papillary muscles or chordae tendineae associated with the pulmonary valve.
Located at the opening between the left atrium and left ventricle is the mitral valve , also called the bicuspid valve or the left atrioventricular valve . Structurally, this valve consists of two cusps, compared to the three cusps of the tricuspid valve. In a clinical setting, the valve is referred to as the mitral valve, rather than the bicuspid valve. The two cusps of the mitral valve are attached by chordae tendineae to two papillary muscles that project from the wall of the ventricle.
At the base of the aorta is the aortic semilunar valve, or the aortic valve , which prevents backflow from the aorta. It normally is composed of three flaps. When the ventricle relaxes and blood attempts to flow back into the ventricle from the aorta, blood will fill the cusps of the valve, causing it to close and producing an audible sound.
In Figure \(\PageIndex{12}\) a , the two atrioventricular valves are open and the two semilunar valves are closed. This occurs when both atria and ventricles are relaxed and when the atria contract to pump blood into the ventricles. Figure \(\PageIndex{12}\) b shows a frontal view. Although only the left side of the heart is illustrated, the process is virtually identical on the right.
Figure \(\PageIndex{13}\) a shows the atrioventricular valves closed while the two semilunar valves are open. This occurs when the ventricles contract to eject blood into the pulmonary trunk and aorta. Closure of the two atrioventricular valves prevents blood from being forced back into the atria. This stage can be seen from a frontal view in Figure \(\PageIndex{13}\) b .
When the ventricles begin to contract, pressure within the ventricles rises and blood flows toward the area of lowest pressure, which is initially in the atria. This backflow causes the cusps of the tricuspid and mitral (bicuspid) valves to close. These valves are tied down to the papillary muscles by chordae tendineae. During the relaxation phase of the cardiac cycle, the papillary muscles are also relaxed and the tension on the chordae tendineae is slight (see Figure 19.13 b ). However, as the myocardium of the ventricle contracts, so do the papillary muscles. This creates tension on the chordae tendineae (see Figure 19.14 b ), helping to hold the cusps of the atrioventricular valves in place and preventing them from being blown back into the atria.
The aortic and pulmonary semilunar valves lack the chordae tendineae and papillary muscles associated with the atrioventricular valves. Instead, they consist of pocket-like folds of endocardium reinforced with additional connective tissue. When the ventricles relax and the change in pressure forces the blood toward the ventricles, the blood presses against these cusps and seals the openings.
Interactive Link
Visit this site to observe an echocardiogram of actual heart valves opening and closing. Although much of the heart has been “removed” from this gif loop so the chordae tendineae are not visible, why is their presence more critical for the atrioventricular valves (tricuspid and mitral) than the semilunar (aortic and pulmonary) valves?
Disorders of the...
Heart Valves
When heart valves do not function properly, they are often described as incompetent and result in valvular heart disease, which can range from benign to lethal. Some of these conditions are congenital, that is, the individual was born with the defect, whereas others may be attributed to disease processes or trauma. Some malfunctions are treated with medications, others require surgery, and still others may be mild enough that the condition is merely monitored since treatment might trigger more serious consequences.
Valvular disorders are often caused by carditis, or inflammation of the heart. One common trigger for this inflammation is rheumatic fever, or scarlet fever, an autoimmune response to the presence of a bacterium, Streptococcus pyogenes , normally a disease of childhood.
While any of the heart valves may be involved in valve disorders, mitral regurgitation is the most common, detected in approximately 2 percent of the population, and the pulmonary semilunar valve is the least frequently involved. When a valve malfunctions, the flow of blood to a region will often be disrupted. The resulting inadequate flow of blood to this region will be described in general terms as an insufficiency. The specific type of insufficiency is named for the valve involved: aortic insufficiency, mitral insufficiency, tricuspid insufficiency, or pulmonary insufficiency.
If one of the cusps of the valve is forced backward by the force of the blood, the condition is referred to as a prolapsed valve. Prolapse may occur if the chordae tendineae are damaged or broken, causing the closure mechanism to fail. The failure of the valve to close properly disrupts the normal one-way flow of blood and results in regurgitation, when the blood flows backward from its normal path. Using a stethoscope, the disruption to the normal flow of blood produces a heart murmur.
Stenosis is a condition in which the heart valves become rigid and may calcify over time. The loss of flexibility of the valve interferes with normal function and may cause the heart to work harder to propel blood through the valve, which eventually weakens the heart. Aortic stenosis affects approximately 2 percent of the population over 65 years of age, and the percentage increases to approximately 4 percent in individuals over 85 years. Occasionally, one or more of the chordae tendineae will tear or the papillary muscle itself may die as a component of a myocardial infarction (heart attack). In this case, the patient’s condition will deteriorate dramatically and rapidly, and immediate surgical intervention may be required.
Auscultation, or listening to a patient’s heart sounds, is one of the most useful diagnostic tools, since it is proven, safe, and inexpensive. The term auscultation is derived from the Latin for “to listen,” and the technique has been used for diagnostic purposes as far back as the ancient Egyptians. Valve and septal disorders will trigger abnormal heart sounds. If a valvular disorder is detected or suspected, a test called an echocardiogram, or simply an “echo,” may be ordered. Echocardiograms are sonograms of the heart and can help in the diagnosis of valve disorders as well as a wide variety of heart pathologies.
Interactive Link
Visit this site for a free download, including excellent animations and audio of heart sounds.
Career Connection
Cardiologist
Cardiologists are medical doctors that specialize in the diagnosis and treatment of diseases of the heart. After completing 4 years of medical school, cardiologists complete a three-year residency in internal medicine followed by an additional three or more years in cardiology. Following this 10-year period of medical training and clinical experience, they qualify for a rigorous two-day examination administered by the Board of Internal Medicine that tests their academic training and clinical abilities, including diagnostics and treatment. After successful completion of this examination, a physician becomes a board-certified cardiologist. Some board-certified cardiologists may be invited to become a Fellow of the American College of Cardiology (FACC). This professional recognition is awarded to outstanding physicians based upon merit, including outstanding credentials, achievements, and community contributions to cardiovascular medicine.
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Cardiovascular Technologist/Technician
Cardiovascular technologists/technicians are trained professionals who perform a variety of imaging techniques, such as sonograms or echocardiograms, used by physicians to diagnose and treat diseases of the heart. Nearly all of these positions require an associate degree, and these technicians earn a median salary of $49,410 as of May 2010, according to the U.S. Bureau of Labor Statistics. Growth within the field is fast, projected at 29 percent from 2010 to 2020.
There is a considerable overlap and complementary skills between cardiac technicians and vascular technicians, and so the term cardiovascular technician is often used. Special certifications within the field require documenting appropriate experience and completing additional and often expensive certification examinations. These subspecialties include Certified Rhythm Analysis Technician (CRAT), Certified Cardiographic Technician (CCT), Registered Congenital Cardiac Sonographer (RCCS), Registered Cardiac Electrophysiology Specialist (RCES), Registered Cardiovascular Invasive Specialist (RCIS), Registered Cardiac Sonographer (RCS), Registered Vascular Specialist (RVS), and Registered Phlebology Sonographer (RPhS).
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Coronary Circulation
You will recall that the heart is a remarkable pump composed largely of cardiac muscle cells that are incredibly active throughout life. Like all other cells, a cardiomyocyte requires a reliable supply of oxygen and nutrients, and a way to remove wastes, so it needs a dedicated, complex, and extensive coronary circulation. And because of the critical and nearly ceaseless activity of the heart throughout life, this need for a blood supply is even greater than for a typical cell. However, coronary circulation is not continuous; rather, it cycles, reaching a peak when the heart muscle is relaxed and nearly ceasing while it is contracting.
Coronary Arteries
Coronary arteries supply blood to the myocardium and other components of the heart. The first portion of the aorta after it arises from the left ventricle gives rise to the coronary arteries. There are three dilations in the wall of the aorta just superior to the aortic semilunar valve. Two of these, the left posterior aortic sinus and anterior aortic sinus, give rise to the left and right coronary arteries, respectively. The third sinus, the right posterior aortic sinus, typically does not give rise to a vessel. Coronary vessel branches that remain on the surface of the artery and follow the sulci are called epicardial coronary arteries .
The left coronary artery distributes blood to the left side of the heart, the left atrium and ventricle, and the interventricular septum. The circumflex artery arises from the left coronary artery and follows the coronary sulcus to the left. Eventually, it will fuse with the small branches of the right coronary artery. The larger anterior interventricular artery , also known as the left anterior descending artery (LAD), is the second major branch arising from the left coronary artery. It follows the anterior interventricular sulcus around the pulmonary trunk. Along the way it gives rise to numerous smaller branches that interconnect with the branches of the posterior interventricular artery, forming anastomoses. An anastomosis is an area where vessels unite to form interconnections that normally allow blood to circulate to a region even if there may be partial blockage in another branch. The anastomoses in the heart are very small. Therefore, this ability is somewhat restricted in the heart so a coronary artery blockage often results in death of the cells (myocardial infarction) supplied by the particular vessel.
The right coronary artery proceeds along the coronary sulcus and distributes blood to the right atrium, portions of both ventricles, and the heart conduction system. Normally, one or more marginal arteries arise from the right coronary artery inferior to the right atrium. The marginal arteries supply blood to the superficial portions of the right ventricle. On the posterior surface of the heart, the right coronary artery gives rise to the posterior interventricular artery , also known as the posterior descending artery. It runs along the posterior portion of the interventricular sulcus toward the apex of the heart, giving rise to branches that supply the interventricular septum and portions of both ventricles. Figure \(\PageIndex{14}\) presents views of the coronary circulation from both the anterior and posterior views.
Diseases of the...
Heart: Myocardial Infarction
Myocardial infarction (MI) is the formal term for what is commonly referred to as a heart attack. It normally results from a lack of blood flow (ischemia) and oxygen (hypoxia) to a region of the heart, resulting in death of the cardiac muscle cells. An MI often occurs when a coronary artery is blocked by the buildup of atherosclerotic plaque consisting of lipids, cholesterol and fatty acids, and white blood cells, primarily macrophages. It can also occur when a portion of an unstable atherosclerotic plaque travels through the coronary arterial system and lodges in one of the smaller vessels. The resulting blockage restricts the flow of blood and oxygen to the myocardium and causes death of the tissue. MIs may be triggered by excessive exercise, in which the partially occluded artery is no longer able to pump sufficient quantities of blood, or severe stress, which may induce spasm of the smooth muscle in the walls of the vessel.
In the case of acute MI, there is often sudden pain beneath the sternum (retrosternal pain) called angina pectoris, often radiating down the left arm in males but not in female patients. Until this anomaly between the sexes was discovered, many female patients suffering MIs were misdiagnosed and sent home. In addition, patients typically present with difficulty breathing and shortness of breath (dyspnea), irregular heartbeat (palpations), nausea and vomiting, sweating (diaphoresis), anxiety, and fainting (syncope), although not all of these symptoms may be present. Many of the symptoms are shared with other medical conditions, including anxiety attacks and simple indigestion, so differential diagnosis is critical. It is estimated that between 22 and 64 percent of MIs present without any symptoms.
An MI can be confirmed by examining the patient’s ECG, which frequently reveals alterations in the ST and Q components. Some classification schemes of MI are referred to as ST-elevated MI (STEMI) and non-elevated MI (non-STEMI). In addition, echocardiography or cardiac magnetic resonance imaging may be employed. Common blood tests indicating an MI include elevated levels of creatine kinase MB (an enzyme that catalyzes the conversion of creatine to phosphocreatine, consuming ATP) and cardiac troponin (the regulatory protein for muscle contraction), both of which are released by damaged cardiac muscle cells.
Immediate treatments for MI are essential and include administering supplemental oxygen, aspirin that helps to break up clots, and nitroglycerine administered sublingually (under the tongue) to facilitate its absorption. Despite its unquestioned success in treatments and use since the 1880s, the mechanism of nitroglycerine is still incompletely understood but is believed to involve the release of nitric oxide, a known vasodilator, and endothelium-derived releasing factor, which also relaxes the smooth muscle in the tunica media of coronary vessels. Longer-term treatments include injections of thrombolytic agents such as streptokinase that dissolve the clot, the anticoagulant heparin, balloon angioplasty and stents to open blocked vessels, and bypass surgery to allow blood to pass around the site of blockage. If the damage is extensive, coronary replacement with a donor heart or coronary assist device, a sophisticated mechanical device that supplements the pumping activity of the heart, may be employed. Despite the attention, development of artificial hearts to augment the severely limited supply of heart donors has proven less than satisfactory but will likely improve in the future.
MIs may trigger cardiac arrest, but the two are not synonymous. Important risk factors for MI include cardiovascular disease, age, smoking, high blood levels of the low-density lipoprotein (LDL, often referred to as “bad” cholesterol), low levels of high-density lipoprotein (HDL, or “good” cholesterol), hypertension, diabetes mellitus, obesity, lack of physical exercise, chronic kidney disease, excessive alcohol consumption, and use of illegal drugs.
Coronary Veins
Coronary veins drain the heart and generally parallel the large surface arteries (see Figure \(\PageIndex{14}\)). The great cardiac vein can be seen initially on the surface of the heart following the interventricular sulcus, but it eventually flows along the coronary sulcus into the coronary sinus on the posterior surface. The great cardiac vein initially parallels the anterior interventricular artery and drains the areas supplied by this vessel. It receives several major branches, including the posterior cardiac vein, the middle cardiac vein, and the small cardiac vein. The posterior cardiac vein parallels and drains the areas supplied by the marginal artery branch of the circumflex artery. The middle cardiac vein parallels and drains the areas supplied by the posterior interventricular artery. The small cardiac vein parallels the right coronary artery and drains the blood from the posterior surfaces of the right atrium and ventricle. The coronary sinus is a large, thin-walled vein on the posterior surface of the heart lying within the atrioventricular sulcus and emptying directly into the right atrium. The anterior cardiac veins parallel the small cardiac arteries and drain the anterior surface of the right ventricle. Unlike these other cardiac veins, it bypasses the coronary sinus and drains directly into the right atrium.
Disorders of the...
Heart: Coronary Artery Disease
Coronary artery disease is the leading cause of death worldwide. It occurs when the buildup of plaque—a fatty material including cholesterol, connective tissue, white blood cells, and some smooth muscle cells—within the walls of the arteries obstructs the flow of blood and decreases the flexibility or compliance of the vessels. This condition is called atherosclerosis, a hardening of the arteries that involves the accumulation of plaque. As the coronary blood vessels become occluded, the flow of blood to the tissues will be restricted, a condition called ischemia that causes the cells to receive insufficient amounts of oxygen, called hypoxia. Figure \(\PageIndex{15}\) shows the blockage of coronary arteries highlighted by the injection of dye. Some individuals with coronary artery disease report pain radiating from the chest called angina pectoris, but others remain asymptomatic. If untreated, coronary artery disease can lead to MI or a heart attack.
The disease progresses slowly and often begins in children and can be seen as fatty “streaks” in the vessels. It then gradually progresses throughout life. Well-documented risk factors include smoking, family history, hypertension, obesity, diabetes, high alcohol consumption, lack of exercise, stress, and hyperlipidemia or high circulating levels of lipids in the blood. Treatments may include medication, changes to diet and exercise, angioplasty with a balloon catheter, insertion of a stent, or coronary bypass procedure.
Angioplasty is a procedure in which the occlusion is mechanically widened with a balloon. A specialized catheter with an expandable tip is inserted into a superficial vessel, normally in the leg, and then directed to the site of the occlusion. At this point, the balloon is inflated to compress the plaque material and to open the vessel to increase blood flow. Then, the balloon is deflated and retracted. A stent consisting of a specialized mesh is typically inserted at the site of occlusion to reinforce the weakened and damaged walls. Stent insertions have been routine in cardiology for more than 40 years.
Coronary bypass surgery may also be performed. This surgical procedure grafts a replacement vessel obtained from another, less vital portion of the body to bypass the occluded area. This procedure is clearly effective in treating patients experiencing a MI, but overall does not increase longevity. Nor does it seem advisable in patients with stable although diminished cardiac capacity since frequently loss of mental acuity occurs following the procedure. Long-term changes to behavior, emphasizing diet and exercise plus a medicine regime tailored to lower blood pressure, lower cholesterol and lipids, and reduce clotting are equally as effective.


4.4: Theories of Inequity and Inequality
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- Jennifer Hasty, David G. Lewis, & Marjorie M. Snipes
- OpenStax
Learning Objectives
By the end of this section, you will be able to:
- Differentiate between systematic and systemic inequities.
- Discuss theories of social inequality and anthropology’s past of upholding social inequalities.
- Describe the connections between power, agency, and resistance.
Social Stratification
Division of labor, in and of itself, is not hierarchical, but when different values are assigned to different types of labor and some positions or people have power over others, this creates a hierarchy. A hierarchy is a type of social organization in which certain people or roles are given more power and prestige than others. As discussed in Economic Anthropology, there are various possible divisions of labor depending on a group’s mode of production. Many gatherer-hunter groups experience a social structure described as egalitarian , in which the diverse roles in a system of production are all given the same decision-making power and accorded the same respect among the group. In such societies, power is usually afforded by age grades, with the elders holding the most power.
Conversely, when there are differences in status or power between various roles, social stratification results. Social stratification is the hierarchical organization of different groups of people, whether based on racial category, socioeconomic status, kinship, religion, birth order, or gender. In horticultural societies, this stratification can be linked to charismatic leaders or leaders whose power is culturally imbued at birth. State societies, and specifically market economies, are considered the most stratified, meaning they have the highest resource inequities. Whether in the Inca Empire of the 1300s or the contemporary United States, a complex system of social hierarchy and social inequality accompanies state-level societies.
Levels of Inequality
Although it is important to understand the ways in which societies control resource accumulation, it is also important to study the phenomena and experiences of inequality in one’s own culture. This section will examine how individuals experience different levels of social inequalities. In contemporary societies, experiences of social inequalities often have roots in systems of capitalism, colonialism, racism, and sexism, which all include a perceived superiority of one group over another.
Interpersonal inequalities , which are power imbalances that are rooted in personal biases, occur every day, reifying and naturalizing inequalities that exist at institutional and systemic levels. Institutional inequalities stem from the policies and practices of organizations (educational institutions, government, companies) that perpetuate oppression. Institutional inequalities exist outside of the day-to-day interactions that people experience, are often unseen, and feel like the status quo. Structural inequalities exist at a level above personal interactions and institutions because they are based on the accumulated effects of institutional decisions across society and history. This type of inequality is pervasive, global, and especially difficult to disrupt. Structural inequalities can reaffirm individual biases, creating a self-reinforcing cycle. Finally, systemic inequalities are the confluence of interpersonal, institutional, and structural inequalities; these are often portrayed by “isms” such as racism, classism, and sexism.
Inequality refers to the unequal distribution of resources. Most people learn about inequality at a young age when they are exposed to people from different socioeconomic classes in places such as schools, places of worship, or social organizations. They recognize that some people have more resources at their disposal, whether through inborn talents or social connections. Such people may wear more expensive clothing, drive more expensive cars, and even have more opportunities than others. Social inequalities are based on individual people’s backgrounds and how their opportunities in life have been affected by racism, sexism, classism, and other forms of oppression . In this context, oppression is defined as unjust exercises of power that may be overt or covert and are often used to control or inflict harm on entire groups of people. Inequity , on the other hand, refers to the unequal distribution of resources due to an unjust power imbalance. It is a type of inequality caused by this unequal distribution, often as a result of injustices against historically excluded groups of people. In the United States, inequity is seen today in areas such as the banking industry, access to voting, and the housing market, where minority groups continue to face challenges related to fairness and equitable distribution of resources. Social inequalities lead to inequity when the groups in charge of distribution allocate resources in ways that further oppress marginalized groups.
You may have seen images on social media trying to explain the difference between inequality and inequity—or, on the flip side, equality and equity. One problem with such images, as Sarah Willen, Colleen Walsh, and Abigail Fisher Williamson (2021) point out, is that because they depict individuals, audiences may interpret these images as calling for localized or individual solutions rather than systemic changes. Oppression and inequity most often are not interpersonal but exist on a structural level of economics, politics, and socialization that normalizes their presence.
In order to understand the differences between inequality and inequity, systematic oppression and systemic oppression, it is important to know that the word system has two different definitions. A system can refer to a formula for methodically attaining a goal, such as a system someone creates to study vocabulary before a foreign language exam. The term systematic oppression derives from this meaning; it is the intentional mistreatment of certain groups. On the other hand, the term system can also mean a combination of parts to form a complex whole, such as the organs in an organism. This definition is the root of the term systemic oppression , which describes how political, economic, and social inequalities are normalized and perpetuated. Many scholars have determined that systemic oppression is permanently ingrained in US laws, government, and society, with the result that it is both unseen and subconsciously upheld daily.
When discussing inequality and inequity, it is also important to understand power , which, in its simplest sense, is the ability to exert control, authority, or influence over others. Individuals with more power have more agency , or capability to act and make decisions. Agency should not be confused with free will because an individual’s agency is often heavily shaped by social characteristics such as race, gender, and class. Along with social inequalities, this chapter will discuss power, agency, and how the two are conceptualized by anthropologists through various perspectives and theoretical frameworks.
Classic Theories of Social Inequality
The remainder of this chapter will examine social inequalities in detail. It will cover racism, classism, and sexism along with some common paradigms and theoretical frameworks that explain systems of inequality and power.
According to philosopher Thomas Kuhn, paradigms are worldviews that often define a scientific discipline during a specific time period. In The Structure of Scientific Revolutions (1962), Kuhn argues that paradigms can shift when a dominant paradigm cannot explain newly discovered phenomena under which normal science operates. Each of the theories that follow was based on a paradigm shift in the social sciences of its time period. The frameworks that anthropologists use to understand power imbalances have been built on the critiques of many of the initial anthropological explanations for power imbalances and social inequalities.
Social Darwinism and Unilinear Cultural Evolution
Social Darwinism played an important role in the colonialist attitudes of the 19th and 20th centuries. Charles Darwin’s theory of evolution, discussed in detail in Biological Evolution and Early Human Evidence , speaks of how traits beneficial to the procreation of a species are passed down, creating changes over time that lead to the evolution of species on Earth. In his Principles of Biology (1864–1867), social scientist Herbert Spencer applies the principles of evolution to human societies, combining his concept of the “survival of the fittest” with French naturalist Jean-Baptiste Lamarck’s views that acquired characteristics can be passed down. Spencer argues that characteristics such as a tendency to work hard and achieve success are passed down from generation to generation, as are traits such as weaknesses and laziness, thus attributing ongoing social inequalities to biological differences.
Social Darwinists of the 19th and 20th centuries utilized Spencer’s survival theory (under Darwin’s name) to argue that competition for resources meant that “weak” human individuals should die out so that “stronger” traits could be passed down to the next generation. Social Darwinists claimed that any group that conquered another was better fit to survive and that those who were conquered would benefit from the civilizing influence of more powerful nations.
Although popular among certain social scientists, social Darwinism was not a term often used in anthropology. Anthropologists instead turned to the theory of unilinear cultural evolution (UCE), made famous by anthropologists E. B. Tylor and Lewis H. Morgan in the 19th century. UCE, which was based on comparing and contrasting different cultures, theorized that societies progressed in a linear fashion, from the lowest level of savagery through barbarism to civilization. Social Darwinism and UCE upheld social inequalities because these theories argued that the defining features of civilization were social hierarchy and inequality. They were the basis for White Europeans’ claims that their culture held more power, had more value, and allowed them to exert military power over lands that were not their own.
Functionalism
Functionalism is a theory attributed to French sociologist Emile Durkheim in the early 20th century. In anthropology, the best-known of the functionalists are Bronislaw Malinowski and A. R. Radcliffe Brown, who examined the purpose that certain cultural characteristics serve in the order of society. For functionalists, egalitarian societies have certain rituals or beliefs that maintain equality, while in stratified societies, the hierarchy of roles maintains order when conflict arises. The function of social stratification, then, is to give power to those who are most equipped to lead, or to motivate those with talents to achieve positions of power and create wealth for the larger society. A functionalist view understands social inequalities as a reflection of people’s varying levels of benefit to the group.
Later theorists criticized functionalism for its use of research that was ahistorical , meaning that it did not acknowledge the specific historical experiences of a group and thus attempted to understand societies without taking into consideration their connections to other cultures. For instance, functionalists largely ignored the impacts of colonialism on small, seemingly isolated populations, arguing instead that social stratification—and, consequently, global political inequalities—was an unyielding and inevitable part of the process of becoming a “complex society.”
Conflict Theory
Conflict theory, created by the late 19th-century political philosopher Karl Marx, offers a more pessimistic view. Marx argued that hierarchy is not a means of keeping society balanced but rather the main source of conflict among humans. He and Friedrich Engels originally conceptualized two classes of capitalism in terms of ownership. The bourgeoisie , descended from powerful families, were the owners of the means of production, while the proletariat were those who sold their labor and lived off a wage. The powerless majority, the proletariat, were far removed from the decision makers and power holders, who had separated the proletariat from their own skills through industrialization and mechanization. In this view, the conflict between those with wealth and the means of production and those without is the basis of all social conflict.
As more social scientists grappled with differences in class and wage, they began to critique conflict theory more. W. E. B. Du Bois ([1940] 1984), an American sociologist working in the early 20th century, added wage and race theories to the classic examination of class conflict. He questioned whether there was a relationship between one’s knowledge in a trade and one’s wages and subsequently concluded that the worth of labor was determined solely by capitalists (the bourgeoisie). Du Bois further observed that class distinctions were forming among Black groups in Philadelphia, mostly unnoticed by White people, who continued to generalize them as one monolithic group. His critique was that conflict theory did not take race into account as both an area wherein class differences occur and another area that can cause conflict (and detract from issues of class and wage). Du Bois’s pioneering ethnographic studies at the turn of the 20th century were among the earliest scientific research on Black Americans’ lived experience of race and racism in the United States. His influence on and relationship with anthropologist Franz Boas were significant factors in Boas’s own disavowal of race as a determinant of the value and worth of diverse cultures. Du Bois’s work remains relevant in the present day as anthropology continues to address its own historical roots in colonialism.
Critical Race Theory
Critical race theory (CRT) , developed by legal scholars in the 1980s, asserts that much of the inequity experienced by oppressed people in the United States can be understood through the critical lens of race. CRT states that racism is endemic, or regularly found in the laws, policies, and institutions of the United States. Thus, people who are socialized in American institutions often do not see the ways in which racism plays out in their daily lives. Notions of color blindness and meritocracy uphold the idea that racism either does not exist or is actually related to class, socioeconomics, or other factors. Color blindness is the idea that people “don’t see color,” meaning that they are unaware of the ways in which someone may experience the world because of the color of their skin. A meritocracy is a system in which people succeed entirely through their own hard work; thus, someone who believes in the notion of meritocracy overlooks any structural or racial inequities that may keep individuals from accessing the resources necessary for success (Delgado and Stefancic 2013). In the United States, these two concepts are often used together to blame poor (especially poor Black) individuals and families for their own misfortunes instead of looking to structural causes of poverty and income inequality. The term welfare queen is often used by politicians and the media to refer to a specific (Black or minority) demographic, even though statistically, White women are the most common recipients of government benefits. One way to challenge everyday endemic racism is to utilize counter-storytelling. These stories counteract the socialized assumptions that keep people of color marginalized. For instance, counter-stories are important in challenging the power of stereotypes such as the “welfare queen.”
Critical race theory has become a hotly debated topic among politicians in the United States. CRT is often misunderstood by critics, who see it as a one-sided examination of (particularly American) history and society because CRT examines society through the lens of power and oppression. It often focuses on which groups benefit from cultural changes, including such things as civil rights legislation, essential to a democracy’s guarantee of equal opportunity and protection under the law. In anthropology, CRT is an important tool for examining both modern institutions and the experiences of individuals in the United States, especially in regard to social inequalities. As just one example, CRT can shed light on the decisions made by those in power when redrawing the boundaries of voting districts. These decisions are often made with the goal of cementing a majority for a particular political party while diluting the voting power of citizens who don’t typically belong that party, a practice known as gerrymandering. It is important for social scientists to consider the potential role of race and racism in making these decisions. If race and/or racism were found to be a factor, then these political decisions would be considered an example of systemic oppression.
Power
More contemporary frameworks of social inequalities include an understanding of power. This section dives into the concepts and frameworks used in studying power. To recap, power is the ability to exert control, authority, or influence over others; agency , which comes from power, is the capability to act and make decisions. Power can be conceptualized as both subtle and coercive; in some contexts, it’s obvious who has power and how it’s utilized, but in other contexts, there are power imbalances that are allowed in everyday life. The point of this section is to contemplate why people allow certain power imbalances to exist while challenging others. Often, people allow power imbalances that they benefit from and resist imbalances that they do not benefit from. To better understand this, it is useful to discuss various concepts related to power, including hegemony, the state apparatus, biopolitics, and necropolitics.
Hegemony
Antonio Gramsci, famous for his writings on philosophy, political theory, sociology, linguistics, and history, came up with the concept of hegemony while imprisoned by the Fascist Italian government. A founding member of the Communist Party of Italy, he was arrested by Benito Mussolini’s Fascist regime for provoking class hatred and civil war and was sentenced to 20 years of imprisonment. In The Prison Notebooks , composed of 33 notebooks written during his imprisonment, Gramsci writes about power using the notion of hegemony. Hegemony describes how people with power keep their power through the subtle dissemination of certain values and beliefs. Hegemony relies on the maintenance of a “groups’’ authority and various mechanisms through which those in marginalized groups accept the leadership of another group’s authority. These mechanisms include cultural institutions such as education, religion, family, and common practices of everyday life. When a paradigm is so dominant that no one questions it, it becomes hegemonic. For instance, the idea that the United States is a democracy, even though many Americans are disenfranchised from voting and several presidential candidates have won the popular vote but lost the election, could be considered a hegemonic paradigm.
The State Apparatus
French Marxist philosopher Louis Pierre Althusser is known for his writings about ideologies of exploitation. Asking how those who are exploited continue to remain exploited, Althusser developed the concept of the state apparatus . The state apparatus consists of two intertwined but distinct sets of institutions, the repressive state apparatus and the ideological state apparatus, which function together to maintain state order and control. Repressive state apparatuses include institutions through which the ruling class enforces its control, such as the government, administrators, the army, the police, the courts, and prisons. These institutions are repressive because they function by violence or force. Althusser argues that the state also consists of ideological state apparatuses , which include distinct and specialized institutions such as religious institutions, public and private education systems, legal systems, political parties, communication systems (radio, newspapers, television), family, and culture (literature, arts, and sports). Ideological state apparatuses, although they include different institutions that are dominated by ruling class ideologies, are also sites where the ideologies of exploited classes can grow. Therefore, ideological state apparatuses can be places of class struggle and social change.
Biopolitics
French philosopher Michel Foucault conceptualized power through biopolitics , which refers to the ways populations are divided and categorized as a means of control, often by the state. This categorization and division—in terms of race, religion, or citizenship status, for instance—seeks to further marginalize certain groups and increase the power of the state. Biopolitics can be understood as the use of power to control a population through surveillance, which Foucault refers to as biopower in his book The History of Sexuality ([1978] 1990). An example of biopower in action is government control of immigrants, especially undocumented migrants. In his ethnography Pathogenic Policing: Immigration Enforcement and Health in the US South (2019), medical and legal anthropologist Nolan Kline describes immigrant policing as a form of biopower that attempts to control and govern immigrants through tactics based on fear, making undocumented immigrants fearful as they go about the normal activities of their daily lives, with many afraid to even seek health services when necessary.
Necropolitics
Cameroonian philosopher and political theorist Joseph-Achille Mbembe, known as Achille Mbembe, writes about power through the idea of necropolitics (the power of death). Necropolitics , an extension of Foucault’s biopolitics, explores the government’s power to decide how certain categories of people live and whose deaths are more acceptable. Mbembe describes this as a power to decide “who matters and who does not, who is disposable and who is not” (2003, 27). The power to determine a life’s worth resides within both political systems and the decisions that policy makers are tasked with. It has, quite literally, life-or-death consequences, from who has access to life-saving medical technology to who is most policed and most likely to end up in jail.
The Black Lives Matter social justice movement is a response to an understanding that modern necropolitics in the United States treats Black people as disposable. The Black Lives Matter movement has grown beyond the United States in response to other nations’ state policies that are seen as treating people of color as not worthy of protection or care.
Agency
Agency, or the ability to act and make decisions, has become an important concept in anthropology because it helps make sense of how powerful institutions interact with individuals.
With the theory of agency and structuration, British sociologist Anthony Giddens paved the way for the growth of theories on how humans interact with systems. Systems are the powerful, overarching beliefs through which the world is organized, which influence the ways in which individuals interact with their world. Although they most often go unnoticed and unquestioned, systems influence the decisions humans make. In terms of social inequality, in systems with unequal access to resources, the ability to decide or the options that one can choose between differ depending on diverse variables. The more power people have, the more choices they may be presented with, and the more they can mold and shape the systems in which they live through their decisions.
French sociologist Pierre Bourdieu attempted to explain how societal structures are upheld and changed by processes generated by individuals. The idea of habitus , or the ingrained habits and dispositions that are socialized into people from birth depending on their status in society, is used to explain how individuals uphold cultural systems such as capitalism, class, racism, or patriarchal values. Habitus is understood both to imbue people with certain skill sets and perspectives according to their life experiences and to make possible social change because it understands systems as generative instead of static. For instance, the modern capitalist system has not always existed as know it is today. Many smaller decisions, practices, and consequences have formed and reformed capitalism, reflecting diverse interests over time.
Resistance
In their attempts to better understand power and agency, Marxist and feminist anthropologists in the 1980s and 1990s wrote a number of ethnographies about the relationship between resistance and the systems that create social inequalities and oppression. Resistance , at the basic level, refers to the act of challenging power and domination. Power is nearly always resisted in both overt and subtle ways, but the difference is often reflected in how much agency individuals have in resisting systems of domination and oppression. This section uses the example of Palestine to explore ways in which Palestinians are resisting power.
The creation of the state of Israel in 1948 dispossessed the Palestinians who were indigenous to the land. Between 400 and 600 Palestinian villages were destroyed, and between 700,000 and 750,000 Palestinians were exiled from the portion of Palestine that became Israel.
While Israelis celebrate achieving independence in 1948, Palestinians refer to this period of displacement of hundreds of thousands from their homes as the Nakba , which translates from Arabic as “disaster” or “catastrophe.” The Nakba is ongoing in the Occupied Palestinian Territory (OPT), which includes the West Bank, East Jerusalem, and Gaza, where the occupation by Israel is illegal according to international laws. The Nakba is also ongoing for members of the Palestinian diaspora (the dispersion of a people from their original home) around the world who do not have the right to return.
Palestinians living in the West Bank and East Jerusalem live under a system of checkpoints, military occupation, and segregation from Jewish settlers. Palestinians in Gaza are living in an open-air prison with extremely limited access to clean water, inconsistent electricity, and no freedom of movement (Erakat and Azzeh 2016). Despite this level of oppression, Palestinians in different parts of the OPT and the Palestinian diaspora still have agency, and they use this agency in different ways to resist Israeli oppression and the devaluation of the Palestinian experience. While political and social movements are critically important for combating injustice and oppression, there are also Palestinians and Israelis working together to create cultural bridges between the communities. One example of this is the West-Eastern Divan Orchestra.
Founded in 1999 by pianist and conductor Daniel Barenboim, who was born in Argentina and moved to Israel as a child, and Palestinian scholar and activist Edward Said, the West-Eastern Divan Orchestra is a group of Israeli, Arab, and Palestinian musicians who work to promote equality and understanding across sociopolitical divides. The orchestra travels and performs internationally as an “orchestra against ignorance,” founded on the idea that when musicians come together to create music, they must work in harmony and respect each other. Not only intended to forge strong bonds among the musicians, the orchestra also serves to highlight the importance of respecting cultural differences and of recognizing a common humanity within the Middle East as a whole. Barenboim states emphatically that the orchestra’s purpose is not to make peace but to create the conditions for peace. Ethnocentrism underlies oppression, and model initiatives such as the West-Eastern Divan Orchestra serve as reminders of the importance of tolerance and respect as deterrents against oppression.