Lab Exam 2

Question 1

Describe the general function of the cardiovascular system

Answer 1

The general function of the cardiovascular system is to circulate blood throughout the body to meet the changing needs of body cells. To remain healthy, all cells require (1) a continuous delivery of oxygen and nutrients and (2) the removal of carbon dioxide and other waste products. The cardiovascular system is effective in fulfilling its function if it provides adequate perfusion to maintain the health of all body cells. and healthy, patent (open and unblocked) blood vessels. If the heart fails to pump sufficient volumes of blood, or the vessels become hardened or occluded (blocked), then an adequate amount of blood may not reach the body’s cells.

Question 2

Differentiate among the three primary types of blood vessels

Answer 2

Arteries transport blood away from the heart; veins transport blood toward the heart; and capillaries serve as the sites of exchange, either between the blood and the alveoli (air sacs) of the lungs or between the blood and the systemic cells.

Question 3

Compare and contrast pulmonary circulation and systemic circulation of the cardiovascular system. Trace blood flow through both circulations.

Answer 3

Blood flow through pulmonary circulation
1 Deoxygenated blood enters the right atrium from the venae cavae (SVC and IVC) and coronary sinus (not shown). This blood then
2 passes through the right AV valve (tricuspid valve),
3 enters the right ventricle,
4 passes through the pulmonary semilunar valve, and
5 enters the pulmonary trunk.
6 This blood continues through the right and left pulmonary arteries to both lungs, and
7 enters pulmonary capillaries of both lungs for gas exchange.
8 This blood, which is now oxygenated, enters right and left pulmonary veins, and is returned to
9 the left atrium of the heart.

Blood flow through systemic circulation
1 Oxygenated blood enters the left atrium,
2 passes through the left AV valve (bicuspid or mitral valve),
3 enters the left ventricle,
4 passes through aortic semilunar valve, and
5 enters the aorta.
6 This blood is distributed by the systemic arteries, and
7 enters systemic capillaries for nutrient and gas exchange.
8 This blood, which is now deoxygenated, ultimately drains into the SVC, IVC, and coronary sinus (not shown), and
9 enters the right atrium.

Question 4

Describe the location of the heart in the thoracic cavity

Answer 4

The heart is positioned posterior to the sternum left of the body midline between the lungs within the mediastinum. The orientation of the heart is slightly rotated such that its right side or right border is located more anteriorly, whereas its left side or left border is located more posteriorly. The postero-superior surface of the heart is called the base. The inferior, conical end of the heart is called the apex

Question 5

List and describe the structural components of the pericardium

Answer 5

The protective layers of the heart include the pericardial sac, composed of an outer fibrous pericardium and an inner serous membrane called the parietal layer of serous pericardium. Tightly adhered to the heart is a serous membrane called the visceral layer of serous pericardium. The space between the parietal and visceral layers is called the pericardial cavity, which contains serous fluid produced by both serous membranes.

The fibrous pericardium, which is composed of dense irregular connective tissue that encloses the heart but does not attach to it. Rather, this layer is attached inferiorly to the diaphragm and superiorly to the base of the great arterial trunks (pulmonary trunk and aorta).
The parietal layer of the serous pericardium, which is composed of simple squamous epithelium and an underlying delicate layer of areolar connective tissue, adheres to the inner surface of the fibrous pericardium.
∙ The visceral layer of the serous pericardium (also called the epicardium) is also composed of a simple squamous epithelium and an underlying delicate layer of areolar connective tissue. This serosal layer adheres directly to the heart. The two serosal layers are continuous with one another (near the great vessels of the heart) and separated by a potential space called the pericardial cavity.

The fibrous pericardium and the parietal layer of the serous pericardium together compose the more loosely fitting “bag,” called the pericardial sac.

Question 6

Compare the superficial features of the anterior and posterior aspects of the heart.

Answer 6

Anterior view: The portion of the right atrium that is most noticeable is its wrinkled, flaplike extension called the right auricle. Portions of both the left auricle of the left atrium and the left ventricle are also visible. Also seen in this view are the positions of attachment for both the pulmonary trunk to the right ventricle and the aorta to the left ventricle. Note that the pulmonary trunk splits into the right and left pulmonary arteries, and that the aorta includes the ascending aorta (which extends superiorly from the heart), the curved aortic arch, and the descending aorta (which extends inferiorly through the trunk.

Posterior view
Sulci of the Heart
The atria are separated from the ventricles externally by a relatively deep groove called the coronary sulcus (or atrioventricular sulcus), which extends around the circumference of the heart. It can be viewed on both the anterior and posterior view. An interventricular sulcus is a groove between the ventricles that extends inferiorly from the coronary sulcus toward the heart apex, and delineates the superficial boundary between the right and left ventricles. The anterior interventricular sulcus is located on the anterior side of the heart, and the posterior interventricular sulcus is located on the posterior side of the heart. Located within all of these sulci are coronary vessels associated with supplying blood to the heart wall.

Question 7

Name the three layers of the heart wall and the tissue components of each

Answer 7

The epicardium is the outermost heart layer and is also called the visceral layer of serous pericardium. This layer is composed of simple squamous epithelium and an underlying layer of areolar connective tissue. As we age, the epicardium thickens as it becomes more invested with adipose connective tissue.

The myocardium is the middle layer of the heart wall. It is composed of cardiac muscle tissue and is the thickest of the three heart wall layers. Contraction of cardiac muscle composing the myocardium generates the force necessary to pump blood. The ventricular myocardium may change in thickness as we age or if we participate in regular, rigorous exercise. For example, it hypertrophies in response to narrowing of systemic arteries because the heart must work harder to pump the blood.

The internal surface of the heart and the external surfaces of the heart valves are covered by endocardium. The endocardium, like the epicardium, is composed of a simple squamous epithelium and an underlying layer of areolar connective tissue. The epithelial layer of the endocardium is continuous with the epithelial layer called the endothelium, which lines the blood vessels

Question 8

Right atrium

Answer 8

The internal wall of the right atrium is smooth on its posterior surface, but it exhibits muscular ridges called pectinate muscles on its anterior wall and within the auricle. Inspection of the interatrial septum reveals an oval depression called the fossa ovalis. It occupies the former location of the fetal foramen ovale, which shunted blood from the right atrium to the left atrium, bypassing the lungs during fetal life. Immediately inferior to the fossa ovalis is the opening of the coronary sinus, which drains deoxygenated blood from the heart wall. Openings of the superior and inferior venae cavae are also visible. Thus, three veins drain deoxygenated blood into the right atrium: the coronary sinus, superior vena cava, and inferior vena cava.

Question 9

Right ventricle

Answer 9

The internal wall surface of the right ventricle displays characteristic large, smooth, irregular muscular ridges, called the trabeculae carneae. Extending from the internal wall of the right ventricle are typically three cone-shaped, muscular projections called papillary muscles. Papillary muscles anchor thin strands of collagen fibers called tendinous cords or chordae tendineae, which are attached to the free edge of the right atrioventricular valve. The superior portion of the right ventricle narrows into a smooth-walled region leading into the pulmonary trunk. The pulmonary semilunar valve is positioned between the right ventricle and pulmonary trunk. Deoxygenated blood is pumped from the right ventricle through the open pulmonary semilunar valve into the pulmonary trunk.

Question 10

Left atrium

Answer 10

The left atrium, like the right atrium, has pectinate muscles in its auricle. Openings of the pulmonary veins are visible. Separating the left atrium from the left ventricle is the left atrioventricular opening, which contains the left AV valve. Oxygenated blood flows from the left atrium, through the left atrioventricular opening when the valve is open, into the left ventricle.

Question 11

Left ventricle

Answer 11

The internal surface of the left ventricle also displays characteristic trabeculae carneae. It has two papillary muscles that are anchored by tendinous cords. The entrance into the aorta is located at the superior aspect of the left ventricle. The aortic semilunar valve is positioned at the boundary of the left ventricle and ascending aorta. Oxygenated blood is pumped from the left ventricle through the open aortic semilunar valve into the pulmonary trunk.

Question 12

Compare and contrast the structure and function of the two types of heart valves

Answer 12

Atrioventricular valve
When open, the cusps of the valve extend into the ventricles. This allows blood to move from an atrium into the ventricle. When the ventricles contract, blood is forced superiorly as ventricular pressure rises. This causes the AV valves to close. The papillary muscles secure the tendinous cords that attach to the lower surface of each AV valve cusp. This prevents the valve from inverting into the atrium when the valve is closed. By being properly held in place, the cusps of the AV valves prevent backflow of blood into the atrium.

Semilunar Valves
The pulmonary semilunar valve is located between the right ventricle and the pulmonary trunk, and the aortic semilunar valve is located between the left ventricle and the ascending aorta. Each valve is composed of three pocketlike cusps, which have the shape of a half-moon. Neither papillary muscles nor tendinous cords are associated with these valves.
The semilunar valves open when the ventricles contract and the force of the blood pushes the semilunar valves open and blood enters the arterial trunks. The valves close when the ventricles relax and the pressure in the ventricle becomes less than the pressure in an arterial trunk. Blood in the arteries begins to move backward toward the ventricle and is caught in the cusps of the semilunar valves, and they close. The closure of the semilunar valves prevents backflow of blood into the ventricle.

Question 13

Describe the location and function of the fibrous skeleton

Answer 13

The heart is supported internally by a fibrous skeleton composed of dense irregular connective tissue. This fibrous skeleton performs the following functions:
∙ Provides structural support at the boundary between the atria and the ventricles
∙ Forms supportive fibrous rings to anchor the heart valves
∙ Provides a rigid framework for the attachment of cardiac muscle tissue
∙ Acts as an electric insulator because it prevents propagation of action potentials directly from the atria to the ventricles, thus preventing the ventricles from contracting at the same time as the atria
Cardiac muscle cells are arranged in spiral bundles around the heart chambers attached to the fibrous skeleton. When the atria contract, they compress the wall of the chambers inward, thus narrowing them and moving the blood inferiorly into the ventricles. When the ventricles contract, the action is similar to the wringing of a mop in that it begins at the apex of the heart and compresses superiorly, moving the blood into the great arteries.

Question 14

Identify the coronary arteries and describe the specific areas of the heart supplied by their major branches.

Answer 14

The vessels that transport oxygenated blood to the wall of the heart are called coronary arteries, whereas coronary veins transport deoxygenated blood away from the heart wall.
Right and left coronary arteries are positioned within the coronary sulcus of the heart to supply the heart wall (figure 19.13a). These arteries are the first and only branches of the ascending aorta and originate immediately superior to the aortic semilunar valve.
The right coronary artery typically branches into the right marginal artery to supply the lateral wall of the right ventricle, and the posterior interventricular artery (or posterior descending artery) to supply the posterior wall of both the left and right ventricles. The left coronary artery typically branches into the circumflex artery to supply the lateral wall of the left ventricle, and the anterior interventricular artery (also called the left anterior descending artery, or LAD) to supply both the anterior wall of the left ventricle and most of the interventricular septum

Question 15

Describe blood flow through the coronary arteries

Answer 15

Coronary arterial blood flow to the heart wall is intermittent. This occurs because coronary vessels are patent (open) when the heart is relaxed and blood flow is possible. However, coronary vessels are compressed when the heart contracts, temporarily interrupting blood flow. Thus, blood flow to the heart wall is not a steady stream; it is impeded and then flows, as the heart rhythmically contracts and relaxes.

Question 16

Identify the coronary veins and describe the specific areas of the heart drained by their major branches.

Answer 16

Transport of deoxygenated blood from the myocardium occurs through one of several cardiac veins. These include the great cardiac vein within the anterior interventricular sulcus, positioned alongside the anterior interventricular artery; the middle cardiac vein within the posterior interventricular sulcus, positioned alongside the posterior interventricular artery; and a small cardiac vein positioned alongside the right marginal artery. These cardiac veins all drain into the coronary sinus, a large vein that lies within the posterior aspect of the coronary sulcus. The coronary sinus then returns this deoxygenated blood directly into the right atrium of the heart.

Question 17

Describe the three tunics common to most vessels

Answer 17

The innermost layer of a blood vessel wall is the tunica intima, or tunica interna. It is composed of an endothelium that is adjacent to the blood vessel lumen and a thin subendothelial layer of areolar connective tissue. The endothelium both provides a smooth surface as the blood moves through the lumen of the blood vessel and releases substances (e.g., nitric oxide, endothelin) to regulate contraction and relaxation of smooth muscle within the tunica media. Recall that the endothelium is continuous with the endocardium, which is the inner lining of the heart.
The tunica media is the middle layer of the vessel wall. It is composed predominantly of circularly arranged layers of smooth muscle cells that are supported by elastic fibers. Contraction of smooth muscle in the tunica media results in vasoconstriction, or narrowing of the blood vessel lumen; relaxation of the smooth muscle causes vasodilation, or widening of the blood vessel lumen.
The tunica externa is the outermost layer of the blood vessel wall. It is composed of areolar connective tissue that contains elastic and collagen fibers. The tunica externa helps anchor the vessel to other structures. Very large blood vessels require their own blood supply to the tunica externa in the form of a network of small arteries called the vasa vasorum. The vasa vasorum extends through the tunica externa.

Question 18

Explain the distinguishing features of the tunics found in arteries, capillaries, and veins.

Answer 18

Arteries and veins that supply the same body region and tend to lie next to one another are called companion vessels. Compared to their venous companions, arteries have a thicker tunica media, a narrower lumen, and more elastic and collagen fibers. These differences mean that arterial walls can spring back to shape and are more resilient and resistant to changes in blood pressure than are veins. In addition, an artery remains patent (open) even without blood in it.
In contrast, veins have a thicker tunica externa, a wider lumen, and less elastic and collagen fibers than a companion artery. The wall of a vein is typically collapsed if no blood is in the vessel.
Capillaries are unique in that they contain only the tunica intima composed of an endothelium and its underlying basement membrane; there is no subendothelial layer. Having this thin barrier allows for rapid gas and nutrient exchange between the blood in capillaries and the tissues.

Question 19

Elastic arteries

Answer 19

Elastic arteries are the largest arteries. They are also called conducting arteries because they conduct blood—from the heart to the smaller muscular arteries.
these are present throughout all three tunics, especially in the tunica media. The abundant elastic fibers allow the artery to stretch and accommodate the blood when a heart ventricle ejects blood into it during ventricular systole (contraction) and then recoil, which helps propel the blood through the arteries during ventricular diastole (relaxation).
The largest arteries close to the heart (e.g., aorta, pulmonary trunk, brachiocephalic, common carotid, subclavian) and the common iliac arteries are examples of elastic arteries. Elastic arteries branch into muscular arteries.

Question 20

Muscular arteries

Answer 20

These medium-sized arteries are also called distributing arteries because they distribute blood to specific body regions and organs.
Muscular arteries have a proportionately thicker tunica media, with multiple layers of smooth muscle cells. Unlike in elastic arteries, the elastic fibers in muscular arteries are confined to two circumscribed sheets: The internal elastic lamina separates the tunica media from the tunica intima, and the external elastic lamina separates the tunica media from the tunica externa. The relatively greater amount of muscle and lesser amount of elastic tissue result in a better ability to vasoconstrict and vasodilate, although with a lessened ability to stretch in comparison to elastic arteries.
Most named arteries (e.g., the brachial, anterior tibial, coronary, and inferior mesenteric arteries) are examples of muscular arteries. Muscular arteries branch into arterioles.

Question 21

Arterioles

Answer 21

In general, arterioles have fewer than six layers of smooth muscle in their tunica media. Larger arterioles have all three tunics, whereas the smallest arterioles may have a tunica intima surrounded by a single layer of smooth muscle cells. Smooth muscle in the arterioles is slightly contracted. This contracted state is called vasomotor tone and is regulated by the vasomotor center in the brainstem. Sympathetic motor tone results in vasoconstriction, which allows for varying degrees of change from this slightly contracted state.
Arterioles have a significant role in regulating systemic blood pressure and blood flow to the different areas of the body.

Question 22

Describe the general anatomic structure and function of capillaries.

Answer 22

Capillaries are the smallest blood vessels. They connect arterioles to venules. The narrow vessel diameter means erythrocytes must move in single file (termed rouleau) through each capillary. Capillaries consist solely of an endothelial layer (of simple squamous cells) resting on a basement membrane. The narrow vessel diameter and the thin wall are optimal for exchange of substances between blood and body tissues.

Question 23

Compare the anatomic structure, function, and location of continuous capillaries, fenestrated capillaries, and sinusoids

Answer 23

Continuous capillaries are the most common type of capillary. The endothelial cells form a complete, continuous lining around the lumen that rests on a complete basement membrane. Tight junctions secure endothelial cells to one another; however, they do not form a complete “seal.” The gaps between the endothelial cells are called intercellular clefts. Materials can move into or out of the blood either through endothelial cells by membrane transport processes or between endothelial cells through intercellular clefts by diffusion and bulk flow.
The size of intercellular clefts prevents the movement of large substances, including formed elements and plasma proteins, while allowing the movement of fluid containing small substances, such as glucose, amino acids, and ions. Continuous capillaries are found, for example, in muscle, the skin, the thymus, the lungs, and the central nervous system.
Fenestrated capillaries are also composed of a complete, continuous lining of endothelial cells and a complete basement membrane. However, small regions of the endothelial cells are extremely thin; these thin areas are called fenestrations (or pores). Fenestrations are small enough to prevent formed elements from passing through the wall yet large enough to allow the movement of some smaller plasma proteins. capillaries are seen where a great deal of fluid transport between the blood and interstitial tissue occurs. Examples of structures that contain fenestrated capillaries include the small intestine, the ciliary process of the eye, the choroid plexus of the brain in the production of cerebrospinal fluid, most of the endocrine glands to facilitate the absorption of hormones into the blood, and the kidneys for the filtering of blood.
Sinusoids, or discontinuous capillaries, have an incomplete lining of the endothelial cells with large openings, or gaps, and the basement membrane is either discontinuous or absent. These openings allow for transport of large substances (formed elements, large plasma proteins), as well as plasma between the blood and tissues. Sinusoids are found in red bone marrow for the entrance of formed elements into the blood, the liver and spleen for the removal of aged erythrocytes from the cardiovascular circulation, and some endocrine glands for the movement of hormone molecules into the blood.

Question 24

Trace the pathway of vessels from the right ventricle to the lungs and back to the left atrium

Answer 24

Deoxygenated blood is transported to the lungs.
1 Right atrium
2 Right ventricle
3 Pulmonary trunk
4 Pulmonary arteries
5 Pulmonary arterioles
6 Gas exchange occurs
in the pulmonary capillaries.
Oxygenated blood is transported from the lungs back to the heart.
7 Pulmonary venules
8 Pulmonary veins
9 Left atrium
10 Left ventricle
11 Aorta

Question 25

Describe features of the pulmonary circulation that distinguish it from systemic circulation

Answer 25

Pulmonary arteries have less elastic connective tissue and wider lumens than systemic arteries. Compared to the systemic circulation, pulmonary vessels are relatively short, because the lungs are close to the heart. As a result, blood pressure is lower throughout the pulmonary circulation in comparison to the systemic circulation. The pressure changes associated with the pulmonary circulation are as follows:
- Blood leaves the right ventricle with a systolic pressure of about 15 to 25 mm Hg, depending upon whether the body is resting or active.
- Blood pressure drops as the blood passes through the pulmonary trunk and right and left pulmonary arteries, reaching an overall pressure of about 10 mm Hg in the pulmonary capillaries of the alveoli. This lower pressure means that the blood moves more slowly in pulmonary capillaries than in systemic capillaries, facilitating gas exchange within the lungs.
- Blood exits the pulmonary capillaries into progressively larger veins that become the pulmonary veins; blood pressure is almost 0 mm Hg as these veins empty into the left atrium.

Question 26

Diagram and explain the cerebral arterial circle and its function

Answer 26

The cerebral arterial circle (circle of Willis) is an important arterial anastomosis. This anastomosis is located around the hypophyseal fossa of the sphenoid bone, which houses the pituitary gland. The circle is formed from posterior cerebral arteries, posterior communicating arteries (branches of the posterior cerebral arteries), internal carotid arteries, anterior cerebral arteries, and an anterior communicating artery (which connects the two anterior cerebral arteries). This arterial circle equalizes blood pressure in the brain and can provide collateral channels, should one vessel become blocked.

Question 27

Describe the general structure and function of dural venous sinuses

Answer 27

Some cranial venous blood is drained by the vertebral veins that extend through the transverse foramina of the cervical vertebrae and drain into the brachiocephalic veins. However, most of the venous blood of the cranium drains through several large veins collectively known as the dural venous sinuses. Recall that these large, modified veins are formed between the two layers of dura mater and receive excess cerebrospinal fluid. Blood from the dural venous sinus system is drained primarily into the internal jugular vein.

Question 28

Describe the composition and function of the hepatic portal system

Answer 28

Blood that has passed through the capillaries of digestive organs and the spleen, and is then drained by its respective veins, is not directly returned to the inferior vena cava and returned to the heart. Instead, the blood is transported from the veins of the digestive organs and spleen into a hepatic portal system that drains the blood into the liver before this blood drains to the inferior vena cava.
The hepatic portal system provides the means for the liver to process blood that has passed through the blood vessels of the digestive organs before it is returned to the heart and redistributed throughout the body. This blood is nutrient-rich, is deoxygenated, and may contain harmful substances that were absorbed from the digestive organs. The hepatic portal system also receives products of erythrocyte destruction from the spleen, so that the liver can recycle some of these components.
Within the hepatic portal system, blood from the digestive organs drains into three main venous branches:
1. The splenic vein, a horizontally positioned vein
2. The inferior mesenteric vein, a vertically positioned vein
3. The superior mesenteric vein, another vertically positioned vein located more to the right side of the body
Blood from all three of these veins drains into the hepatic portal vein, which drains blood to the liver (at its inferior portion). Some small veins, such as the left and right gastric veins, drain directly into the hepatic portal vein. The venous blood in the hepatic portal vein flows through the sinusoids of the liver. In these sinusoids, the venous blood mixes with arterial oxygenated blood entering the liver via the hepatic arteries. Thus, deoxygenated but high-nutrient-filled blood from digestive organs and oxygenated blood from the hepatic artery merge and flow within the liver sinusoids.
Blood leaves the liver (from its superior portion) through hepatic veins that merge with the inferior vena cava.

Question 29

Trace the route of blood from the gastrointestinal tract to the inferior vena cava

Answer 29

Blood from the digestive organs → drain into the 3 venous branches: splenic vein, inferior mesenteric vein, and superior mesenteric vein (all apart of hepatic portal system) → liver → hepatic veins → inferior vena cava

Question 30

Trace the pathway of blood circulation in the fetus

Answer 30

1 Oxygenated blood from the placenta enters the body of the
fetus through the umbilical vein.
2 The blood from the umbilical vein is shunted away from the liver and directly toward the inferior vena cava through the ductus venosus.
3 Oxygenated blood in the ductus venosus mixes with deoxygenated blood in the inferior vena cava.
4 Blood from the superior and inferior venae cavae empties into the right atrium.
5 Because pressure is greater on the right side of the heart than on the left side, most of the blood is shunted from the right atrium to the left atrium via the foramen ovale. This blood flows into the left ventricle and then is pumped out through the aorta.
6 A small amount of blood enters the right ventricle and then the pulmonary trunk, but much of this blood is shunted from the pulmonary trunk to the aorta through a vessel detour called the ductus arteriosus.
7 Blood is transported to the rest of the body, and the deoxygenated blood returns to the placenta through a pair of umbilical arteries.
8 Nutrient and gas exchange occurs at the placenta, and the cycle repeats.