1. Pima Medical Institute BIO 120
Hole’s Essentials of Human Anatomy & Physiology
Lesson13
Cardiovascular System
BIO 120 Lesson 13 – Cardiovascular System
David Shier, Jackie Butler, Ricki Lewis, Hole’s Essentials of Human Anatomy & Physiology, 10th Ed. CopyrightThe McGraw-Hill Companies, Inc. Created by Dr. Melissa Eisenhauer, Trevecca Nazarene University

2. Cardiovascular System
 Introduction
A. The cardiovascular system consists of the heart and vessels (arteries, capillaries and veins.)
B. A functional cardiovascular system is vital for supplying oxygen and nutrients to tissues and removing wastes from them.
C. Deoxygenated blood is carried by the pulmonary circuit to the lungs, while the systemic circuit sends oxygenated blood to all body cells.
The heart pumps 7,000 liters of blood through the body each day, contracting some 2.5 billion times in an average lifetime. This muscular pump forces blood through arteries, which connect to smaller-diameter vessels called arterioles. Arterioles branch into the tiniest tubes, the capillaries, which are sites of nutrient, electrolyte, gas, and waste exchange. Capillaries converge into venules, which in turn converge into veins that return blood to the heart, completing the closed system of blood circulation. Theses structures—the pump and its vessels—form the cardiovascular system.
The pulmonary circuit sends oxygen depleted (deoxygenated) blood to the lungs to pick up oxygen and unload carbon dioxide. The systemic circuit sends oxygen-rich (oxygenated) blood and nutrients to all body cells and removes wastes. Without circulation, tissues would lack a supply of oxygen and nutrients, and wastes would accumulate.

3. The below figure shows the general pattern of blood transport in the cardiovascular system
The cardiovascular system transports blood between the body cells and organs such as the lungs, intestines, and kidneys that communicate with the external environment. Vessels in the pulmonary circuit carry blood from the heart to the lungs and back to the heart, replenishing oxygen and releasing the metabolic waste CO2. Vessels of the systemic circuit supply all of the other cells.
Figure 13.1

4.  Structure of the Heart
A. The heart is a hollow, cone-shaped, muscular pump within the thoracic cavity.
B. Size and Location of the Heart
1. The average adult heart is 14 cm long and 9 cm wide.
2. The heart lies in the mediastinum under the sternum; its apex extends to the fifth intercostal space.
The heart is a hollow, cone-shaped, muscular pump. It lies within the thoracic cavity and rests on the diaphragm (see figure 13.2, slide 7).
Heart size varies with body size. An average adult’s hear is about 14 centimeters long and 9 centimeters wide. The heart is within the mediastinum, bordered laterally by the lungs, posteriorly by the vertebral column, and anteriorly by the sternum. The base of the heart, which attaches to several large blood vessels, lies beneath the second rib. The heart’s distal end extends downward and to the left, terminating as a bluntly pointed apex at the level of the fifth intercostal space.

5. C. Coverings of the Heart 1. The pericardium encloses the heart.
2. It is made of two layers: the outer, tough connective tissue fibrous pericardium surrounding a more delicate visceral pericardium (epicardium) that surrounds the heart.
The pericardium encloses the heart and proximal ends of the large blood vessels to which it attaches. The pericardium consists of an outer bag, the fibrous pericardium. The fibrous pericardium is dense connective tissue. It is attached to the central portion of the diaphragm, the posterior of the sternum, the vertebral column, and the large blood vessels emerging from the heart.
The fibrous pericardium surrounds a more delicate, double-layered sac. The innermost layer of this sac, the visceral pericardium (epicardium), covers the heart.

6. 3. At the base of the heart, the. visceral pericardium folds back to
3. At the base of the heart, the visceral pericardium folds back to become the parietal pericardium that lines the fibrous pericardium.
4. Between the parietal and visceral pericardia is a potential space (pericardial cavity) filled with serous fluid.
At the base of the heart, the visceral pericardium turns back on itself to become the parietal pericardium, which forms the inner lining of the fibrous pericardium (see figure 13.2, slide 7; and figure 13.4, slide 10). Between the parietal and visceral layers of the pericardium is a space, the pericardial cavity, that contains a small volume of serous fluid (see figure 13.4, slide 10).

7. The heart is within the mediastinum and is enclosed by a layered pericardium.
Figure 13.2

8. 1. The wall of the heart is composed of three distinct layers.
D. Wall of the Heart
1. The wall of the heart is composed of three distinct layers.
2. The outermost layer, the epicardium, is made up of connective tissue and epithelium, and houses blood and lymph capillaries along with coronary arteries. It is the same as the visceral pericardium.
The wall of the heart is composed of three distinct layer —an outer epicardium, a middle myocardium, and an inner endocardium (see figure 13.4, slide 10). The epicardium, which corresponds to the visceral pericardium, protects the heart by reducing friction. It is a serous membrane that consist of connective tissue beneath epithelium. Its deeper portion often contains adipose tissue, particularly along the paths of coronary arteries and cardiac veins that carry blood through the myocardium.

9. a. The endocardium contains the Purkinje fibers.
3. The middle layer called myocardium consists of cardiac muscle and is the thickest layer of the heart wall.
4. The inner endocardium is smooth and is made up of connective tissue and epithelium, and is continuous with the endothelium of major vessels joining the heart.
a. The endocardium contains the Purkinje fibers.
The thick middle layer, or myocardium, consists mostly of cardiac muscle tissue that pumps blood out of the heart chambers. The muscle fibers are organized in planes, separated by connective tissue richly supplied with blood capillaries, lymph capillaries, and nerve fibers.
The inner layer, or endocardium, consists of epithelium and connective tissue that contains many elastic and collagenous fibers. The endocardium also contains blood vessels and some specialized cardiac muscle fibers, called Purkinje fibers.

10. The heart wall has three layers: an endocardium, a myocardium, and an epicardium.
Figure 13.4

11. E. Heart Chambers and Valves
1. The heart has four internal chambers: two atria on top and two ventricles below.
a. Atria receive blood returning to the heart and have thin walls and ear-like auricles projecting from their exterior.
b. The thick-muscled ventricles pump blood to the body.
Internally, the heart is divided into four hollow chambers—two on the left and two on the right (see figure 13.5, slide 16). The upper chambers, called atria, have thin walls and receive blood returning to the heart. Small, earlike projections called auricles extend anteriorly from the atria. The lower chambers, the ventricles, receive blood from the atria and contract to force blood out of the heart into arteries.

12. 2. A septum divides the atrium and. ventricle on each side. Each also
2. A septum divides the atrium and ventricle on each side. Each also has an atrioventricular (A-V) valve to ensure one way flow of blood.
a. The right A-V valve (tricuspid) and left A-V valve (bicuspid or mitral valve) have cusps to which chordae tendinae attach.
A solid, wall-like septum separates the atrium and ventricle on the right side from their counterparts on the left. As a result, blood from one side of the heart never mixes with blood from the other side (except in the fetus). An atrioventricular valve (A-V valve), the tricuspid on the right and the mitral on the left, ensures one-way blood flow between the atria and the ventricles.

13. b. Chordae tendinae are, in turn,. attached to papillary muscles
b. Chordae tendinae are, in turn, attached to papillary muscles in the inner heart wall that contract during ventricular contraction to prevent the backflow of blood through the A-V valves.
The large tricuspid valve, which has three tapered projections called cusps as its name implies, lies between the right atrium and the right ventricle. The valve permits blood to move from the right atrium into the right ventricle and prevents backflow.
Strong, fibrous strings called chordae tendineae attach to the cusps of the tricuspid valve on the ventricular side. These strings originate from small mounds of cardiac muscle tissue, the papillary muscles, that project inward from the walls of the ventricle. The papillary muscles contract when the ventricle contracts. As the tricuspid valve closes, these muscles pull on the chordae tendineae and prevent the cusps from swinging back into the atrium.

14. 3. The superior and inferior vena. cavae bring blood from the body to
3. The superior and inferior vena cavae bring blood from the body to the right atrium.
4. The right ventricle has a thinner wall than does the left ventricle because it must pump blood only as far as the lungs, compared to the left ventricle pumping to the entire body.
The right atrium receives blood from two large veins—the superior vena cava and the inferior vena cava. A smaller vein, the coronary sinus, also drains blood into the right atrium from the myocardium of the heart itself.
The right ventricle has a thinner muscular wall than the left ventricle (see figure 13.5, slide 7). This right chamber pumps blood a short distance to the lungs against a relatively low resistance to blood flow. The left ventricle, on the other hand, must force blood to all the other parts of the body against a much greater resistance to flow.

15. 5. At the base of the pulmonary trunk
5. At the base of the pulmonary trunk leading to the lungs is the pulmonary valve, which prevents a return flow of blood to the ventricle.
6. The left atrium receives blood from four pulmonary veins.
7. The left ventricle pumps blood into the entire body through the aorta, guarded by the aortic valve that prevents backflow of blood into the ventricle.
When the muscular wall of the right ventricle contracts, the blood inside its chamber is put under increasing pressure, and the tricuspid valve closes passively. As a result, the only exit for the blood is through the pulmonary trunk, which divides to form the left and right pulmonary arteries that lead to the lungs. At the base of this trunk is a pulmonary valve with three cusps. This valve allows blood to leave the right ventricle and prevents backflow into the ventricular chamber (see figure 13.6, slide 18).
The left atrium receives blood from the lungs through four pulmonary veins—two from the right lung and two from the left lung. Blood passes from the left atrium into the left ventricle through the mitral valve (shaped like a miter, a type of headpiece), or bicuspid valve, which prevents blood from flowing back into the left atrium from the ventricle.
When the left ventricle contracts, the mitral valve closes passively, and the only exit is through a large artery, the aorta. At the base of the aorta is the aortic valve, which has three cusps. The aortic valve opens and allows blood to leave the left ventricle as it contracts. When the ventricular muscles relax, this valve closes and prevents blood from backing up into the ventricle (see figure 13.6, slide 18).

16. Heart Valves
Table 13.1 summarizes the locations and functions of the hear valves.

17. Coronal section of the heart showing the connection between the left ventricle and the aorta, as well as the four hollow chambers.
Figure 13.5

18. 2. These tough rings prevent dilating of tissue in this area.
F. Skeleton of the Heart
1. Rings of dense connective tissue surround the pulmonary trunk and aorta to provide attachments for the heart valves and fibers.
2. These tough rings prevent dilating of tissue in this area.
Rings of dense connective tissue surround the pulmonary trunk and aorta at their proximal ends. These rings provide firm attachments for the heart valves and for muscle fibers; they also prevent the outlets of the atria and ventricles from dilating during contraction. The fibrous rings, together with other masses of dense connective tissue in the portion of the septum between the ventricles (interventricular septum), constitute the skeleton of the heart (see figure 13.6b, slide 19).

19. Heart valve.
b) The skeleton of the heart consist of fibrous rings to which the heart valves are attached (superior view).
Figure 13.6

20. G. Path of Blood through the Heart
1. Blood low in oxygen returns to the right atrium via the venae cavae and coronary sinus.
2. The right atrium contracts, forcing blood through the tricuspid valve into the right ventricle.
Blood that is low in oxygen and high in carbon dioxide enters the right atrium through the vena cava and coronary sinus. As the right atrial wall contracts, the blood passes through the tricuspid valve and enters the chamber of the right ventricle (see figure 13.7, slide 23).

21. 3. The right ventricle contracts, closing
3. The right ventricle contracts, closing the tricuspid valve, and forcing blood through the pulmonary valve into the pulmonary trunk and arteries.
4. The pulmonary arteries carry blood to the lungs where it can rid itself of excess carbon dioxide and pick up a new supply of oxygen.
When the right ventricular wall contracts, the tricuspid valve closes, and blood moves through the pulmonary valve and into the pulmonary trunk and its branches (pulmonary arteries).
From the pulmonary arteries, blood enters the capillaries associated with the alveoli (microscopic air sacs) of the lungs. Gas exchanges occur between blood in the capillaries and air in the alveoli.

22. 5. Freshly oxygenated blood is returned to
5. Freshly oxygenated blood is returned to the left atrium of the heart through the pulmonary veins.
6. The left atrium contracts, forcing blood through the left bicuspid valve into the left ventricle.
7. The left ventricle contracts, closing the bicuspid valve and forcing open the aortic valve as blood enters the aorta for distribution to the body.
The freshly oxygenated blood, low in carbon dioxide, returns to the heart through the pulmonary veins that lead to the left atrium.
The left atrial wall contracts, and blood moves through the mitral valve and into the chamber of the left ventricle. When the left ventricular wall contracts, the mitral valve closes, and blood moves through the aortic valve and into the aorta and its branches.

23. The right ventricle forces blood to the lungs, whereas the left ventricle forces blood to all other body parts.
Figure 13.7

24. H. Blood Supply to the Heart
1. The first branches off of the aorta, which carry freshly oxygenated blood, are the right and left coronary arteries that feed the heart muscle itself.
2. Branches of the coronary arteries feed many capillaries of the myocardium.
The first two branches of the aorta, called the right and left coronary arteries, supply blood to the tissues of the heart. Their openings lie just beyond the aortic valve (see figure 13.8, slide 25). The heart must beat continually to supply blood to body tissues. To do this, myocardial cells require a constant supply of freshly oxygenated blood.
Branches of the coronary arteries feed the many capillaries of the myocardium (see figure 13.9, slide 27).

25. The openings of the coronary arteries lie just beyond the aortic valve.
Figure 13.8

26. 3. The heart muscle requires a. continuous. supply of freshly
3. The heart muscle requires a continuous supply of freshly oxygenated blood, so smaller branches of arteries often have anastomoses as alternate pathways for blood, should one pathway become blocked.
4. Cardiac veins drain blood from the heart muscle and carry it to the coronary sinus, which empties into the right atrium.
The smaller branches of these arteries usually have connections (anastomoses) between vessels that provide alternate pathways for blood, called collateral circulation. These detours in circulation may supply oxygen and nutrients to the myocardium when a coronary artery is blocked.
Branches of the cardiac veins, whose paths roughly parallel those of the coronary arteries, drain blood that has passed through myocardial capillaries. These veins join an enlarged vein on the heart’s posterior surface—the coronary sinus—which empties into the right atrium.

27. Figure 13.9 Blood vessels associated with the surface of the heart.
Anterior view
Posterior view
Figure 13.9

28.  Heart Actions
A. The cardiac cycle consists of the atria beating in unison (atrial systole) followed by the contraction of both ventricles, (ventricular systole) then the entire heart relaxes for a brief moment (diastole).
The heart chambers function in a coordinated fashion. Their actions are regulated so that atria contract, called atrial systole, while ventricles relax, call ventricular diastole; then ventricles contract (ventricular systole) while atria relax (atrial diastole). Then the atria and ventricle both relax for a brief interval. This series of events constitutes as complete heart-beat, or cardiac cycle.

29. B. Cardiac Cycle
1. During the cardiac cycle, pressure within the heart chambers rises and falls with the contraction and relaxation of atria and ventricles.
2. When the atria fill, pressure in the atria is greater than that of the ventricles, which forces the A-V valves open.
3. Pressure inside atria rises further as they contract, forcing the remaining blood into the ventricles.
During the cardiac cycle, pressure within the heart chambers rises and falls an it is these changes that open and close the valves, much like door being blown open or closed by the wind. When pressure in the ventricle is low, early in diastole, the pressure difference between the atria and ventricles causes the A-V valves to open and the ventricles to fill, about 70% of the returning blood enters the ventricles prior to contraction. When the atria contract, the remain 30% of returning blood is pushed into the ventricles (see figure 13.10a, slide 31).
Then, as the ventricle contract, ventricular pressure rises sharply, and as soon as the ventricular pressure exceeds the atrial pressure, the A-V valves close. At the same time, the papillary muscles contract, and by pulling on the chordae tendineae, they prevent the cusps of the A-V valves from bulging too far into the atria.
During ventricular contraction, the A-V valves remain closed. The atria are now relaxed, and pressure in the atria is quite low, even lower than venous pressure. As a result, blood flows into the atria from the large, attached veins. That is as the ventricles are contracting, the atria are filling, already preparing for the next cardiac cycle (see figure 13.10b, slide 31).

30. 4. When ventricles contract,. pressure inside them increases
4. When ventricles contract, pressure inside them increases sharply, causing A-V valves to close and the aortic and pulmonary valves to open.
a. As the ventricles contract, papillary muscles contract, pulling on chordae tendinae and preventing the backflow of blood through the A-V valves.
When ventricular pressure exceeds the pressure in the pulmonary trunk (right side) and aorta (left side), the pulmonary and aortic valves open; blood is ejected from each valve’s respective ventricle into these arteries. As blood flows out of the ventricles, ventricular pressure begins to drop, and it drops even further as the ventricles begin to relax. When ventricular pressure is lower than blood pressure in the aorta and pulmonary trunk, the pressure difference is reversed, and the semilunar valves close. The ventricle continue to relax, and as soon as ventricular pressure is less than arterial pressure, the A-V valves open, and the ventricles begin to fill once more. Atria and ventricles are both relaxed for a brief interval.

31. A cardiac cycle. The atria (a) empty during atrial systole and (b) fill with blood during atrial diastole.
Figure a & b

32. C. Heart Sounds
1. Heart sounds are due to vibrations in heart tissues as blood rapidly changes velocity within the heart.
2. Heart sounds can be described as a "lubb-dupp" sound.
A heartbeat heard through a stethoscope sounds like lubb-dupp. These sounds are due to vibrations in the heart tissues associated with the closing of the valves.

33. 3. The first sound (lubb) occurs as ventricles contract and A-V valves are closing.
4. The second sound (dupp) occurs as ventricles relax and aortic and pulmonary valves are closing.
The first part of a heart sound (lubb) occurs during ventricular contraction, when the A-V valves are closing. The second part (dupp) occurs during ventricular relaxation, when the pulmonary and aortic valves are closing.

34. D. Cardiac Muscle Fibers
1. A mass of merging fibers that act as a unit is called a functional syncytium; one exists in the atria (atrial syncytium) and one in the ventricles (ventricular syncytium).
A mass of merging cells that function as a unit is called a functional syncytium. Two such structures are in the heart—into the atrial walls, and in the ventricular walls. Portions of the heart’s fibrous skeleton separate these masses of cardiac muscle fibers from each other, except for a small area in the right atrial floor. In this region, the atrial syncytium and the ventricular syncytium are connected by fibers of the cardiac conduction system.

35. E. Cardiac Conduction System
1. Specialized cardiac muscle tissue conducts impulses throughout the myocardium and comprises the cardiac conduction system.
2. A self-exciting mass of specialized cardiac muscle called the sinoatrial node (S-A node or pacemaker), located on the posterior right atrium, generates the impulses for the heartbeat.
Throughout the heart are clumps and stands of specialized cardiac muscle tissue whose fibers contain only a few myofibrils. Instead of contracting, these areas initiate and distribute impulses throughout the myocardium. They comprise the cardiac conduction system, which coordinates the events of the cardiac cycle (see figure 13.11, slide 38).
A key portion of this conduction system, is the S-A node or sinoatrial node, a small, elongated mass of specialized cardiac muscle tissue just beneath the epicardium. It is located in the right atrium near the opening of the superior vena cava, and its fibers are continuous with those of the atrial syncytium. The cells of the S-A node can reach threshold on their own, and their membranes contact one another. Without stimulation from nerve fibers or any other outside agents, the nodal cells initiate impulses that spread into the surrounding myocardium and stimulate cardiac muscle fibers to contract. S-A node activity is rhythmic. The S-A node initiate one impulse after another, seventy to eight times a minute in an adult. Because it generates the heart’s rhythmic contractions, it if often called the pacemaker.

36. 3. Impulses spread next to the atrial. syncytium, it contracts, and
3. Impulses spread next to the atrial syncytium, it contracts, and impulses travel to the junctional fibers leading to the atrioventricular node (A-V node) located in the septum.
a. Junctional fibers are small, allowing the atria to contract before the impulse spreads rapidly over the ventricles.
As a cardiac impulse travels from the S-A node into the atrial syncytium, the right and left atria begin to contract almost simultaneously. The cardiac impulse does not pass directly into the ventricular syncytium, which is separated fro the atrial syncytium by the fibrous skeleton of the heart. Instead, the impulse passes along fibers (junctional fibers) of the conduction system that lead to a mass of specialized cardiac muscle tissue called the A-V node or atrioventricular node. This node is located in the inferior portion of the septum that separates the atria (interatrial septum) and just beneath the endocardium. It provides the only normal conduction pathway between the atrial and venticular syncytia.
The junctional fibers that conduct the cardiac impulse into the A-V node have very small diameter, and because small fibers conduct impulses slowly, they delay impulse transmission. The impulse is delayed further as it moves through the A-V node, allowing more time for the atria to contract completely so that they empty all their blood into the ventricles prior to ventricular contraction.

37. 4. Branches of the A-V bundle give. rise to Purkinje fibers leading to
4. Branches of the A-V bundle give rise to Purkinje fibers leading to papillary muscles; these fibers stimulate contraction of the papillary muscles at the same time the ventricles contract.
Once the cardiac impulse reaches the distal side of the A-V node, it passes into a group of large fibers that make up the A-V bundle (bundle of His). The A-V bundle enters the upper part of the interventricular septum and divides into right and left bundle branches that lie just beneath the endocardium. About halfway down the septum, the branches give rise to enlarged Purkinje fibers.
Purkinje fibers spread form the interventricular septum into the papillary muscles, which project inward form ventricular walls and then continue downward to the apex of the heart. There they curve around the tips of the ventricles and pass upward over the lateral walls of these chambers. Along the way, the Purkinje fibers give off many small branches, which becomes continuous with cardiac muscle fibers. When impulses on the Purkinje fibers stimulate these muscle fibers, the ventricular walls contract with a twisting motion. This action squeezes blood out of the ventricular chambers and forces it into the aorta and pulmonary trunk.

38. The cardiac conduction system coordinates the cardiac cycle.
Figure 13.11

39. F. Electrocardiogram
1. An electrocardiogram is a recording of the electrical changes that occur during a cardiac cycle.
2. The first wave, the P wave, corresponds to the depolarization of the atria.
3. The QRS complex corresponds to the depolarization of ventricles and hides the repolarization of atria.
An electrocardiogram, or ECG, is a recording of the electrical changes that occur in the myocardium during a cardiac cycle.
To record an ECG, electrodes are placed on the skin and connected by wires to an instrument that responds to very weak electrical changes by moving a pen or stylus on a moving strip of paper. Up-and-down movements of the pen correspond to electrical changes in the myocardium.
When the S-A node trigger a cardiac impulse, atrial fibers depolarize, producing an electrical change. The pen moves, and at the end of the electrical change, returns to the base position. This first pen movement produces a P wave, corresponding to depolarization of the atrial fibers that will lead to contraction of the atria (see figure 13.14, slide 41).
When the cardiac impulse reaches ventricular fibers, they rapidly depolarize. Because ventricular walls are thicker than those of the atria, the electrical change is greater, and the pen deflects more. When the electrical change ends, the pen returns to the baseline, leaving a mark called the QRS complex. This mark consists of a Q wave, and R wave, and an S wave, and corresponds to depolarization of ventricular fibers just prior to the contraction of the ventricular walls.

40. 4. The T waves ends the ECG pattern. and corresponds to ventricular
4. The T waves ends the ECG pattern and corresponds to ventricular repolarization.
The electrical changes occurring as the ventricular muscle fibers repolarize slowly produce a T wave as the pen deflects again, ending the EDG pattern.

41. An electrocardiogram record electrical changes in the myocardium during a cardiac cycle.
A normal ECG
In an ECG pattern, the P wave results form a depolarization of the atria, the QRS complex results from a depolarization of the ventricles, and the T wave results from a repolarization of the ventricles.
Figure 13.14

42. G. Regulation of the Cardiac Cycle
1. The amount of blood pumped at any one time must adjust to the current needs of the body (more is needed during strenuous exercise).
2. The S-A node is innervated by branches of the sympathetic and parasympathetic divisions, so the CNS controls heart rate.
The volume of blood pumped changes to accommodate cellular requirements. For example, during strenuous exercise, skeletal muscles requires more blood, and the heart rate increase in response. Since the S-A node normally controls heart rate, change in this rate are often a response to factors that affect the S-A node, such as the motor impulses carried on the parasympathetic and sympathetic nerve fibers (see chapter 9, p. 249).

43. a. Sympathetic impulses increase the speed of heart rate.
b. Heart rate is decreased by parasympathetic impulses.
Sympathetic fibers reach the heart and join the S-A and A-V nodes as well as other areas of the atrial and ventricular myocardium. The endings of these fibers secrete norepinephrine in response to nerve impulses, which increase the rate and force of myocardial contractions.
The parasympathetic fibers that innervate the heart arise from neurons in the medulla oblongata. Most of these fibers branch to the S-A and A-V nodes. When the nerve impulses reach nerve fiber endings, they secrete acetylcholine, which decrease S-A and A-V node activity. As a result, the heart rate decreases.

44. 3. The cardiac control center of the. medulla oblongata maintains a
3. The cardiac control center of the medulla oblongata maintains a balance between the sympathetic and parasympathetic divisions of the nervous system in response to messages from baroreceptors which detect changes in blood pressure.
Reflexes called baroreceptor reflexes involving the cardiac control center of the medulla oblongata maintain balance between the inhibitory effects of parasympathetic fibers and the excitatory effects of sympathetic fibers. These baroreceptors (pressoreceptors), can detect changes in blood pressure. Rising pressure stretches the receptors, and they signal the cardioinhibitor center in the medulla, oblongata. In response, the medulla oblongata sends parasympathetic impulses to the heart, decreasing heart rate. This action helps lower blood pressure toward normal.

45. 4. Impulses from the cerebrum or. hypothalamus may also influence
4. Impulses from the cerebrum or hypothalamus may also influence heart rate, as do body temperature and the concentrations of certain ions.
Impulses from the cerebrum or hypothalamus also influence the cardiac control center. Such impulses may decrease heart rate, as occurs when a person faints following an emotional upset, or they may increase heart rate during a period of anxiety.
Two other factors that influence heart rate are temperature change and certain ions. Rising body temperature increase heart action, which is why heart rate usually increase during fever. On the other hand, abnormally low body temperature decreases heart action.
Of the ions that influence heart actions, the most important are potassium (K+) and calcium (Ca+2) ions. In hyperkalemia, excess extracellular potassium ions decrease the rate and force of contractions. In hypokalemia, deficient extracellular potassium ions may cause a potentially life-threatening abnormal hear rhythm (arrhythmia).
In hypercalcemia, excess extracellular calcium ions increase heart actions, posing the danger that the heart will contract for an abnormally long time. Conversely, in hypocalcemia, low extracellular calcium concentration depresses heart action.

46. Figure 13.16 Baroreceptor reflex. Schematic of a general reflex arc.
Autonomic nerve impulses alter the activities of the S-A and A-V nodes.
Figure 13.16

47.  Blood Vessels
A. The blood vessels (arteries, arterioles, capillaries, venules, and veins) form a closed tube that carries blood away from the heart, to the cells, and back again.
B. Arteries and Arterioles
1. Arteries are strong, elastic vessels adapted for carrying high-pressure blood.
2. Arteries become smaller as they divide and give rise to arterioles.
The blood vessels form a closed circuit of tubes that carries blood from the hear to the body cells and back again. These vessels include arteries, arterioles, capillaries, venules, and veins.
Arteries are strong, elastic vessels that are adapted for carrying blood away from the heart under high pressure. These vessels subdivide into progressively thinner tubes and eventually give rise to finer, branched arterioles.

48. 3. The wall of an artery consists of. an endothelium, tunica media
3. The wall of an artery consists of an endothelium, tunica media (smooth muscle), and tunica externa (connective tissue).
4. Arteries are capable of vasoconstriction as directed by the sympathetic impulses; when impulses are inhibited, vasodilation results.
The wall of an artery consists of three distinct layers (see figure 13.17a, slide 49). The innermost layer (tunica internal) is composed of a layer of simple squamous epithelium, called endothelium, that rests on a connective tissue membrane that is rich in elastic and collagenous fibers. Endothelium helps prevent blood clotting by providing a smooth surface that allow blood cells and platelets to flow through without being damaged and by secreting biochemicals that inhibit platelet aggregation.
The middle layer (tunica media) makes up the bulk of the arterial wall. It includes smooth muscle fibers, which encircle the tube, and a thick layer of elastic connective tissue.
The outer layer (tunica externa) is relatively thin and chiefly consists of connective tissue with irregular elastic and collagenous fibers. This layer attached the artery to the surrounding tissues.
The sympathetic branches of the autonomic nervous system innervate smooth muscle in artery and arteriole walls. Impulses on these vasomotor fibers stimulate the smooth muscles to contract, reducing the diameter of the vessel. This is called vasoconstriction. If vasomotor impulses are inhibited, the muscle fibers relax, and the diameter of the vessel increases. This is called vasodilation. Changes in the diameters of arteries and arterioles greatly influence blood flow and blood pressure.

49. Blood vessels.
The wall of an artery
The wall of a vein.
Figure 13.17

50. C. Capillaries
1. Capillaries are the smallest vessels, consisting only of a layer of endothelium through which substances are exchanged with tissue cells.
2. Capillary permeability varies from one tissue to the next, generally with more permeability in the liver, intestines, and certain glands, and less in muscle and considerably less in the brain (blood-brain barrier).
Capillaries, the smallest-diameter blood vessels, connect the smallest arterioles and the smallest venules. Capillaries are extensions of the inner linings of arterioles in that their walls are composed of endothelium. These thin walls form the semipermeable layer through which substances in the blood are exchanged for substances in the tissue fluid surrounding body cells.
The openings in capillary walls are thin slits where endothelial cells overlap (see figure 13.19, slide 51). The sizes of these openings and, consequently, the permeability of the capillary wall vary from tissue to tissue. For example, the openings are smaller in capillaries of smooth, skeletal, and cardiac muscle than they are in capillaries associated with endocrine glands, the kidneys, and the lining of the small intestine.

51. In capillaries, substances are exchanged between the blood and tissue fluid through openings (slits) separating endothelial cells.
Figure 13.19

52. 3. The pattern of capillary density also
3. The pattern of capillary density also varies from one body part to the next.
a. Areas with a great deal of metabolic activity (leg muscles, for example) have higher densities of capillaries.
Capillary density reflects tissue’s rates of metabolism. Muscle and nerve tissues, which use abundant oxygen and nutrients, are richly supplied with capillaries. Tissues with slow metabolic rates, such as cartilage, the epidermis, and the cornea, lack capillaries.

53. 4. Precapillary sphincters can regulate the amount of blood entering a capillary bed and are controlled by oxygen concentration in the area.
a. If blood is needed elsewhere in the body, the capillary beds in less important areas are shut down.
Smooth muscles that encircle capillary entrances regulate blood distribution in capillary pathways. These muscles form precapillary sphincters, which may close a capillary by contracting or open it by relaxing. A precapillary sphincter responds to the demands of the cells the capillary supplied. When these cells have low concentrations of oxygen and nutrients, the sphincter relaxes, when cellular requirements have been met, the sphincter may contract again. In this way, blood flow can follow different pathways through a tissue to meet the changing cellular requirements.
Routing of blood flow to different parts of the body is due to vasoconstriction and vasodilation of arterioles and percapillary sphincters. For example, during exercise, blood enters the capillary networks of the skeletal muscles, where the cells have increased oxygen and nutrient requirements. At the same time, blood can bypass some of the capillary networks in the digestive tract tissues, where demand for blood is less immediate.

54. D. Exchanges in the Capillaries
1. Blood entering capillaries contains high concentrations of oxygen and nutrients that diffuse out of the capillary wall and into the tissues.
a. Plasma proteins remain in the blood due to their large size.
Gases, nutrients, and metabolic by-products are exchanged between the blood in capillaries and the tissue fluid surrounding body cells. The substances exchanged move through capillary walls by diffusion, filtration , and osmosis (see chapter 3, pp ).
Because blood entering systemic capillaries carries high concentrations of oxygen and nutrients, these substance diffuse through the capillary walls and enter tissue fluid. Conversely, the concentrations of carbon dioxide and other wastes are generally greater in the tissues, and such wastes diffuse into the capillary blood.
Plasma proteins generally remain in the blood because they are too large to diffuse through the membrane pores or slitlike openings between eh endothelial cells of most capillaries. Also, these bulky proteins are not soluble in the lipid portions of capillary cell membranes.

55. 2. Hydrostatic pressure drives the. passage of fluids and very small
2. Hydrostatic pressure drives the passage of fluids and very small molecules out of the capillary at this point.
3. At the venule end, osmosis, due to the osmotic pressure of the blood, causes much of the tissue fluid to return to the bloodstream.
4. Lymphatic vessels collect excess tissue fluid and return it to circulation.
Whereas diffusion depends on concentration gradients, filtration forces molecules through a membrane with hydrostatic pressure. In capillaries, the blood pressure generated when ventricle walls contract provides the force for filtration.
Blood pressure also moves blood through the arteries and arterioles. This pressure decreases as the distance from the heart increases, because of friction (peripheral resistance) between the blood and the vessel walls. For this reason, blood pressure is greater in the arterioles than in capillaries. Blood pressure is similarly greater at the arteriolar end of a capillary than at the venular end. Therefore, the filtration effect occurs primarily at the arteriolar ends of capillaries.
The effect of capillary blood pressure, which favors filtration, opposes the actions of the plasma colloid osmotic pressure, which factors reabsorpton. At the arteriolar end of capillaries, the blood pressure is higher than the colloid osmotic pressure, so filtration predominates. At the venular end, the colloid osmotic pressure is essentially unchanged, but the blood pressure has decrease do to resistance through the capillary, so reabsorption predominates (see figure 13.21, slide 56).
Normally, more fluid leaves the capillaries than returns to them. Closed-ended vessels called lymphatic capillaries collect the excess fluid and return it through lymphatic vessels to the venous circulation.

56. Water and other substances leave capillaries because of a net outward pressure at the capillaries' arteriolar ends. Water enters a the capillaries' venular ends because of a net inward pressure. Substances move in and out along the length of the capillaries according to their respective concentration gradients.
Figure 13.21

57. E. Venules and Veins
1. Venules leading from capillaries merge to form veins that return blood to the heart.
2. Veins have the same three layers as arteries have and have a flap-like valve inside to prevent backflow of blood.
a. Veins are thinner and less muscular than arteries; they do not carry high-pressure blood.
b. Veins also function as blood reservoirs.
Venules are microscopic vessels that continue from the capillaries and merge to form veins. The veins, which carry blood back to the atria, follow pathways that roughly parallel those of the arteries.
The walls of veins are similar to those of arteries in that they are composed of three distinct layers (see figure 13.17b, slide 49). However, the middle layer of the venous wall is poorly developed. Consequently, veins have thinner walls that have less smooth muscle and less elastic connective tissue than those of comparable arteries, but their lumens have a greater diameter.
Many veins, particularly those in the upper and lower limbs, have flaplike valves, which project inward from their linings. Valves are usually composed of two leaflets that close if blood begins to back up in a vein (see figure 13.23, slide 58). These valves aid in returning blood to the heart because they open if blood flow is toward the heart, but close if it is in the opposite direction.
Veins also function as blood reservoirs. For example, in hemorrhage accompanied by a drop in arterial blood pressure, sympathetic nerve impulses reflexly stimulate the muscular walls of the veins. The resulting venous constrictions help maintain blood pressure by returning more blood to the heart. This mechanism ensures a nearly normal blood flow even when as much as 25% of blood volume is lost.

58. Figure 13.23 Venous Valves Venous valves…
a) Allow blood to move toward the heart, but…
b) … prevent blood from moving backward away from the heart
Figure Venous Valves

59. Characteristics of Blood Vessels
Table 13.2 summarizes the characteristics of blood vessels.

60.  Blood Pressure
A. Blood pressure is the force of blood against the inner walls of blood vessels anywhere in the cardiovascular system, although the term "blood pressure" usually refers to arterial pressure.
Blood pressure is the force blood exerts against the inner walls of blood vessels. Although this force occurs throughout the vascular system, the term blood pressure most commonly refers to pressure in arteries supplied by branches of the aorta.

61. B. Arterial Blood Pressure
1. Arterial blood pressure rises and falls following a pattern established by the cardiac cycle.
a. During ventricular contraction, arterial pressure is at its highest (systolic pressure).
b. When ventricles are relaxing, arterial pressure is at its lowest (diastolic pressure).
Arterial blood pressure rises and falls in a pattern corresponding to the phases of the cardiac cycle. That is, contracting ventricles (ventricular systole) squeeze blood out and into the pulmonary trunk and aorta, which sharply increase the pressures in these arteries.
The maximum pressure during ventricular contraction is called systolic pressure. When the ventricles relax (ventricular diastole), the arterial pressure drops, and the lowest pressure that remains in the arteries before the next ventricular contraction is termed the diastolic pressure.
A sphygmomanometer is used to measure arterial blood pressure. The results of this blood pressure measurement are reported as a fraction, normal about 120/80. in this notation, the upper number indicates the arterial systolic pressure in mm Hg (SP), and the lower number indicates the arterial diastolic pressure in mm Hg (DP).
(see figure 13.24, slide 62, which shows how these pressure decrease as distance form the left ventricle increases).

62. Blood pressure decrease as the distance from the left ventricle increase. Systolic pressure occurs during maximal ventricular contraction. Diastolic pressure occurs when the ventricles relax.
Figure 13.24

63. Blood Pressure
2. The surge of blood that occurs with ventricular contraction can be felt at certain points in the body as a pulse.
The surge of blood entering the arterial system during a ventricular contraction distends the elastic arterial walls, but the pressure drops almost immediately as the contraction ends, and the arterial walls recoil. This alternate expanding and recoiling of the arterial wall can be felt as a pulse in an artery that runs close to the surface. The radial artery is commonly used to take a person’s pulse. Other sites where an arterial pulse is easily detected include the carotid, brachial, and femoral arteries.

64. C. Factors that Influence Arterial Blood Pressure
1. Arterial pressure depends on heart action, blood volume, resistance to flow, and blood viscosity.
2. Heart Action
a. Heart action is dependent upon stroke volume and heart rate (together called cardiac output); if cardiac output increases, so does blood pressure.
Arterial blood pressure depends on a variety of factors. These include heart action which includes heart rate and stroke volume, and blood volume, peripheral resistance, and blood viscosity (see figure 13.25, slide 67).
In addition to producing blood pressure by forcing blood into the arteries, heart action determines how much blood enters the arterial system with each ventricular contraction. The volume of blood discharged from the ventricle with each contraction is called the stroke volume and equals about 70 milliliters in an average weight male at rest. The volume discharged from the ventricle per minute is called the cardiac output, calculated by multiplying the stroke volume by the heart rate in beats per minute (cardiac output = stroke volume X heart rate). Thus, if the stroke volume is 70 milliliters and the heart rate is 72 beat per minute, the cardiac output is 5,040 milliliters per minute.
Blood pressure varies with cardiac output. If either stroke volume or heart rate increases, so does cardiac output, and as a result, blood pressure initially rises. Conversely, if stroke volume or heart rate decreases, cardiac output decreases, and blood pressure also initially decreases.

65. 3. Blood Volume
a. Blood pressure is normally directly proportional to the volume of blood within the cardiovascular system.
b. Blood volume varies with age, body size, and gender.
Blood volume equals the sum of the formed elements and plasma volumes in the vascular system. Although the blood volume varies somewhat with age, body size, and sex, it is usually about 5 liters for adults, or 8% of body weight in kilograms.
Blood pressure is normally directly proportional to blood volume within the cardiovascular system. Thus, any changes in blood volume can initially alter blood pressure. For example, if a hemorrhage reduces blood volume, blood pressure initially drops. If a transfusion restores normal blood volume, normal blood pressure may be reestablished. Blood volume can also fall if the fluid balance is upset, as happens in dehydration. Fluid replacement can reestablish normal blood volume and pressure.

66. 4. Peripheral Resistance
a. Friction between blood and the walls of blood vessels is a force called peripheral resistance.
b. As peripheral resistance increases, such as during sympathetic constriction of blood vessels, blood pressure increases.
Friction between the blood and the walls of blood vessels produces a force called peripheral resistance, which hinders blood flow. Blood pressure must overcome this force if the blood is to continue flowing. Therefore, factors that alter the peripheral resistance change blood pressure. For example, contracting smooth muscles in arteriolar walls increase the peripheral resistance by constricting these vessels. Blood backs up into the arteries supplying the arterioles, and the arterial pressure rises. Dilation of arterioles has the opposite effect—peripheral resistance lessens, and arterial blood pressure drops in response.

67. 5. Blood Viscosity
a. The greater the viscosity (ease of flow) of blood, the greater its resistance to flowing, and the greater the blood pressure.
Viscosity is the ease with which a fluid’s molecules flow past one another. The greater the viscosity, the greater the resistance to flowing.
Blood cells and plasma proteins increase blood viscosity. The greater the blood’s resistance to flowing, the great is the force needed to move it through the vascular system. Thus, it is not surprising that blood pressure rises as blood viscosity increases and drops as viscosity decreases.
Figure Some factors that influence arterial blood pressure

68. D. Control of Blood Pressure
1. Blood pressure is determined by cardiac output and peripheral resistance.
2. The body maintains normal blood pressure by adjusting cardiac output and peripheral resistance.
Blood pressure (BP) is determined by cardiac output (CO) and peripheral resistance (PR) according to this relationship:
BP = CO X PR
Maintenance of normal arterial pressure therefore requires regulation of these two factors. For example, cardiac output, depending on the volume of blood discharged from the ventricle (stroke volume), is affected by the blood volume entering the ventricle. Entering blood mechanically stretches myocardial fibers in the ventricular wall. Within limits, the longer these fibers, the greater is the force with which they contract.

69. 3. Cardiac output depends on stroke. volume and heart rate, and a
3. Cardiac output depends on stroke volume and heart rate, and a number of factors can affect these actions.
a. The volume of blood that enters the right atrium is normally equal to the volume leaving the left ventricle.
The more blood that enters the heart from the veins, the greater the ventricular distension, the stronger the contraction, the greater the stroke volume, and the greater the cardiac output. Conversely, the less blood that returns from the veins, the less the ventricle distends, the weaker the ventricular contraction, the lesser the stroke volume and cardiac output. This mechanism ensures that the volume of blood discharged from the heart is equal to the volume entering its chambers.

70. b. If arterial pressure increases,. the cardiac center of the
b. If arterial pressure increases, the cardiac center of the medulla oblongata sends parasympathetic impulses to slow heart rate.
c. If arterial pressure drops, the medulla oblongata sends sympathetic impulses to increase heart rate to adjust blood pressure.
Baroreceptors in the walls of the aorta and carotid arteries sense changes in blood pressure. If arterial pressure increases, nerve impulses travel from the baroreceptors to the cardiac center of the medulla oblongata. This center relays parasympathetic impulses to the S-A node in the heart, and the heart rate decreases in response.
As a result of this cardioinhibitor reflex; cardiac output falls and blood pressure decreases toward the normal level (see figure 13.26, slide 71).
Decreasing arterial blood pressure initiates the cardioaccelerator reflex; which sends sympathetic impulses to the S-A node. As a result, the heart beats faster, increasing cardiac output and arterial pressure.

71. If blood pressure rises, baroreceptors initiate the cardioinhibitor reflex, which lowers the blood pressure.
Figure 13.26

72. d. Other factors, such as. emotional upset, exercise, and
d. Other factors, such as emotional upset, exercise, and a rise in temperature can result in increased cardiac output and increased blood pressure.
Other factors that increase heart rate and blood pressure include exercise, a rise in body temperature, and emotional response, such as fear, and anger.

73. 4. The vasomotor center of the. medulla oblongata can adjust the
4. The vasomotor center of the medulla oblongata can adjust the sympathetic impulses to smooth muscles in arteriole walls, adjusting blood pressure.
a. Certain chemicals, such as carbon dioxide, oxygen, and hydrogen ions, can also affect peripheral resistance.
The vasomotor center of the medulla oblongata continually sends sympathetic impulses to smooth muscles in the arteriole walls, keeping them in a state of tonic contraction, which helps maintain the peripheral resistance associated with normal blood pressure.
Certain chemicals, including carbon dioxide, oxygen, and hydrogen ions, also influence peripheral resistance by affecting precapillary sphincters and smooth muscle in arteriole walls. for example, increasing blood carbon dioxide, decreasing blood oxygen, and lowering blood pH relaxes smooth muscle in the systemic circulation. This increases local blood flow to tissues with high metabolic rates, such as exercising skeletal muscles. In addition, epinephrine and norepinephrine vasoconstrict many systemic vessels, increasing peripheral resistance.

74. E. Venous Blood Flow
1. Blood flow through the venous system is only partially the result of heart action and instead also depends on skeletal muscle contraction, breathing movements, and vasoconstriction of veins.
Blood pressure decreases as blood moves through the arterial system and into the capillary networks, so that little pressure remains at the venular ends of capillaries (see figure 13.24, slide 62). Blood flow through the venous system is only partly the direct result of heart action and depends on other factors, such as skeletal muscle contraction, breathing movements, and vasoconstriction of veins (vasoconstriction).

75. a. Contractions of skeletal. muscle squeeze blood back
a. Contractions of skeletal muscle squeeze blood back up veins one valve at a time.
b. Differences in thoracic and abdominal pressures draw blood back up the veins.
Contracting skeletal muscles press on nearby vessels, squeezing the blood inside. As skeletal muscles press on veins with valves, some blood moves from one valve section to another (see figure 13.23, slide 58). This massaging action of contracting skeletal muscles helps push blood through the venous system toward the heart.
Respiratory movement also move venous blood. During inspiration, the pressure within the thoracic cavity is reduced as the diaphragm contracts and the rib cage moves upward and outward. At the same time, the pressure within the abdominal cavity is increased as the diaphragm presses downward on the abdominal viscera. Consequently, blood is squeezed out of abdominal veins and forced into thoracic veins. During exercise, these respiratory movements act with skeletal muscle contractions to increase the return of venous blood to the heart.

76.  Paths of Circulation
A. The body’s blood vessels can be divided into a pulmonary circuit, including vessels carrying blood to the lungs and back, and a systemic circuit made up of vessels carrying blood from the heart to the rest of the body and back.
Blood vessels can be divided into two major pathways. The pulmonary circuit or pulmonary circulation consists of vessels that carry blood from the heart to the lungs, and back to the heart. The systemic circuit or systemic circulation carries blood from the heart to all other parts of the body and back again. The systemic circuit includes the coronary circulation.

77. B. Pulmonary Circuit
1. The pulmonary circuit is made up of vessels that convey blood from the right ventricle to the pulmonary arteries to the lungs, alveolar capillaries, and pulmonary veins leading from the lungs to the left atrium.
Blood enters the pulmonary circuit as it leaves the right ventricle through the pulmonary trunk. The pulmonary trunk extends upward and posteriorly from the heart. About 5 centimeters above its origin, the pulmonary trunk divides into the right and left pulmonary arteries, which penetrate the right and left lungs, respectively (see figure 13.5, slide 17). After repeated divisions, the pulmonary arteries give rise to arterioles that continue into the capillary networks associated with the walls of the alveoli, where gas is exchanged between the blood and the air.
From the pulmonary capillaries, blood enters the venules, which merge to form small veins, and these veins in turn converge to form still larger veins. Four pulmonary veins, two from each lung, return blood to the left atrium. This completes the vascular loop of the pulmonary circuit.

78. C. Systemic Circuit
1. The systemic circuit includes the aorta and its branches leading to all body tissues as well as the system of veins returning blood to the right atrium.
Freshly oxygenated blood moves from the left atrium into the left ventricle. Contraction of the left ventricle forces this blood into the systemic circuit, which includes the aorta and its branches that lead to all the body tissues, as well as the companion system of veins that returns blood to the right atrium.

79. A. The aorta is the body’s largest artery.
 Arterial System
A. The aorta is the body’s largest artery.
B. Principal Branches of the Aorta
1. The branches of the ascending aorta are the right and left coronary arteries that lead to heart muscle.
2. Principal branches of the aortic arch include the brachiocephalic, left common carotid, and left subclavian arteries.
The aorta is the largest diameter artery in the body. It extends upward from the left ventricle, arches over the heart to the left, and descends just anterior and to the left of the vertebral column (see figure 13.27, slide 81).
The first portion of the aorta is called the ascending aorta. Located at its base are the three cusps of the aortic valve, and opposite each cusp is a swelling in the aortic wall called an aortic sinus. The right and left coronary arteries arise from two of these sinuses (see figure 13.8, slide 25).
Three major arteries originate from the aortic arch (arch of the aorta): the brachiocephalic artery, the left common carotid artery, and the left subclavian artery.

80. 3. The descending aorta (thoracic. aorta) gives rise to many small
3. The descending aorta (thoracic aorta) gives rise to many small arteries to the thoracic wall and thoracic viscera.
4. The abdominal aorta gives off the following branches: celiac, superior mesenteric, suprarenal, renal, gonadal, inferior mesenteric, and common iliac arteries.
The upper part of the descending aorta is left of the midline. It gradually extends medially and finally lies directly in front of the vertebral column at the level of the twelfth thoracic vertebra. The portion of the descending aorta above the diaphragm is the thoracic aorta. It branches into the thoracic wall and thoracic viscera.
Below the diaphragm, the descending aorta becomes the abdominal aorta, and it branches into the abdominal wall and various abdominal organs. Branches to abdominal organs include: the celiac artery, which gives rise to the gastric, splenic, and hepatic arteries; the superior mesenteric artery (supplies small intestine and superior portion of large intestine) and inferior mesenteric artery (supplies inferior portion of large intestine); and the suprarenal arteries, renal arteries, and gonadal arteries, which supply blood to the adrenal glands, kidneys, and ovaries or tests, respectively.
The abdominal aorta ends near the brim of the pelvis, where it divides into right and left common iliac arteries. These vessels supply blood to lower regions of the abdominal wall, the pelvic organs, and the lower extremities.

81. Figure 13.27 Major Branches of the Aorta
Major branches of the aorta (a. stands for artery)
Figure Major Branches of the Aorta

82. Major Branches of the Aorta
Table 13.3 summarizes the major branches of the aorta.

83. C. Arteries to the Head, Neck, and Brain
1. Arteries to the head, neck, and brain include branches of the subclavian and common carotid arteries.
2. The vertebral arteries supply the vertebrae and their associated ligaments and muscles.
Branches of the subclavian and common carotid arteries supply blood to structures within the neck, head, and brain (see figure 13.28, slide 86). The main divisions of the subclavian artery to these regions include the vertebral and thyrocervical arteries. The common carotid artery communicates with these regions by means of the internal and external carotid arteries.
The vertebral arteries pass upward through the foramina of the transverse processes of the cervical vertebrae and enter the skull through the foramen magnum. These vessels supply blood to the vertebrae and to their associated ligaments and muscles.

84. 3. In the cranial cavity, the vertebral
3. In the cranial cavity, the vertebral arteries unite to form a basilar artery which ends as two posterior cerebral arteries.
4. The posterior cerebral arteries help form the circle of Willis which provides alternate pathways through which blood can reach the brain.
In the cranial cavity, the vertebral arteries unite to form a single basilar artery. This vessel passes along the ventral brainstem and gives rise to branches leading to the pons, midbrain, and cerebellum. The basilar artery ends by dividing into two posterior cerebral arteries that supply portions of the occipital and temporal lobes of the cerebrum.
The posterior cerebral arteries also help form the cerebral arterial circle (circle of Willis) at the base of the brain, which connects the vertebral artery and internal carotid artery systems (see figure 13.29, slide 85).
The union of these systems provides alternate pathways for blood to circumvent blockages and reach brain tissues. It also equalizes blood pressure in the brain’s blood supply.

85. Figure 13.29 – Cerebral Arterial Circle (circle of Willis)
The cerebral arterial circle (circle of Willis) is formed by the anterior and posterior cerebral arteries, which join the internal carotid arteries. (a. is for artery.)
Figure – Cerebral Arterial Circle
(circle of Willis)

86. 5. The right and left common carotid arteries
5. The right and left common carotid arteries diverge into the external carotid and internal carotid arteries.
6. Near the base of the internal carotid arteries are the carotid sinuses that contain baroreceptors to monitor blood pressure.
The left and right common carotid arteries diverge into the internal and external carotid arteries. The external carotid artery courses upward on the side of the head, giving off branches to structures in the neck, face, jaw, scalp, and base of the skull. The internal carotid artery follows a deep course upward along the pharynx to the base of the skull. Entering the cranial cavity it provides them major blood supply to the brain.
Near the base of the internal carotid arteries are enlargements called carotid sinuses that, like aortic sinuses, contain baroreceptors controlling blood pressure.

87. The major arteries of the head and neck
The major arteries of the head and neck. Note that the clavicle has been removed (a. stands for artery)
Figure 13.28

88. Major Branches of the External and Internal Carotid Arteries
Table 13.4 summarizes the major branches of the external and internal carotid arteries.

89. D. Arteries to the Shoulder and Upper Limb. 1. The subclavian artery
D. Arteries to the Shoulder and Upper Limb 1. The subclavian artery continues into the arm where it becomes the axillary artery.
2. In the shoulder region, the axial artery becomes the brachial artery that, in turn, gives rise to the ulnar and radial arteries.
The subclavian artery, after giving off branches to the neck, continues into the arm (see figure 13.30, slide 90). It passes between the clavicle and the first rib, and becomes the axillary artery, the axillary artery supplies branches to structure in the axilla and chest wall and becomes the brachial artery, which follows the humerus to the elbow. It gives rise to a deep branchial artery that curves posteriorly around the humerus and supplies the triceps brachii. With the elbow, the brachial artery divides into an ulnar artery and a radial artery.
The ulnar artery leads downward on the ulnar side of the forearm to the wrist. Some of its branches supply the elbow joint, and some supply blood to muscles in the forearm.
The radial artery travels along the radial side of the forearm to the wrist, supplying the lateral muscles of the forearm. As the radial artery nears the wrist, it approaches the surface and provides a convenient vessel for taking he pulse (radial pulse).
At the wrist, the branches of the ulnar and radial arteries join to form a network of vessels. Arteries arising from this network supply blood to the hand.

90. The major arteries to the shoulder and upper limb.
Figure 13.30

91. E. Arteries to the Thoracic and Abdominal Walls
1. Branches of the thoracic aorta and subclavian artery supply the thoracic wall with blood.
2. Branches of the abdominal aorta, as well as other arteries, supply the abdominal wall with blood.
Blood reaches the thoracic wall through several vessels. The internal thoracic artery, a branch of the subclavian artery, gives off two anterior intercostal arteries that supply the intercostal muscles and mammary glands. The posterior intercostal arteries arise form the thoracic aorta and enter the intercostal spaces. They supply the intercostal muscles, the vertebrae, the spinal cord, and the deep muscles of the back.
Branches of the internal thoracic and external iliac arteries provide blood to the anterior abdominal wall. Paired vessels originating from the abdominal aorta, including the phrenic and lumbar arteries, supply blood to structures in the posterior and lateral abdominal wall.

92. F. Arteries to the Pelvis and Lower Limb
1. At the pelvic brim, the abdominal aorta divides to form the common iliac arteries that supply the pelvic organs, gluteal area, and lower limbs.
The abdominal aorta divides to form the common iliac arteries at the level of the pelvic brim, and these vessels provide blood to the pelvic organs, gluteal region, an lower limbs (see figure 13.31, slide 94).

93. 2. The common iliac arteries divide. into internal and external iliac
2. The common iliac arteries divide into internal and external iliac arteries.
a. Internal iliac arteries supply blood to pelvic muscles and visceral structures.
b. External iliac arteries lead into the legs, where they become femoral, popliteal, anterior tibial, and posterior tibial arteries.
Each common iliac artery divides into an internal and an external branch. The internal iliac artery gives off many branches to pelvic muscles and visceral structure, as well as to the gluteal muscles and the external reproductive organs.
The external iliac artery provides the main blood supply to the lower limbs. It passes downward along the brim of the pelvis and branches to supply the muscles and skin in the lower abdominal wall. Midway between the symphysis pubis and the anterior superior iliac spine of the ilium, the external iliac artery becomes the femoral artery.
The femoral artery, which approaches the anterior surface of the upper thigh, branches to muscles and superficial tissues of the thigh. These branches also supply the skin of the groin and the lower abdominal wall.
As the femoral artery reaches the proximal border of the space behind the knee, it becomes the popliteal artery. Braches of this artery supply blood to the knee joint and to certain muscles in the thigh and calf. The popliteal artery diverges into the anterior and posterior tibial arteries.
The anterior tibial artery passes downward between the tibia and fibula, giving off branches to the skin and muscles in the anterior and lateral regions of the leg. This vessel continues into the foot as the dorsalis pedis artery, which supplies blood to the foot. The posterior tibial artery, the larger of the two popliteal branches, descends beneath the calf muscles, branching to the skin, muscles, and other tissues of the leg along the way.

94. Major vessels of the arterial system (a. stands for artery).
Figure 13.31

95. B. Characteristics of Venous Pathways
 Venous System
A. Veins return blood to the heart after the exchange of substances has occurred in the tissues.
B. Characteristics of Venous Pathways
1. Larger veins parallel the courses of arteries and are named accordingly; smaller veins take irregular pathways and are unnamed.
Venous circulation returns blood to the heart after blood and body cells exchange gases, nutrients, and wastes.
Larger veins typically parallel the courses of named arteries, and often bear the same names as their arterial counterparts. For example, the renal vein parallels the renal artery, and the common iliac vein accompanies the common iliac artery.

96. 2. Veins from the head and upper. torso drain into the superior vena
2. Veins from the head and upper torso drain into the superior vena cava.
3. Veins from the lower body drain into the inferior vena cava.
4. The vena cavae merge to join the right atrium.
The veins that carry blood from the lungs and myocardium back to the heart have already been described. The veins from all the other parts of the body converge into two major pathways, the superior and inferior vena cava, which lead to the right atrium.

97. C. Veins from the Head, Neck, and Brain
CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
C. Veins from the Head, Neck, and Brain
1. The jugular veins drain the head and unite with the subclavian veins to form the brachiocephalic veins.
The external jugular veins drain blood from the face, scalp., and superficial regions of the neck. These vessels descend on either side of the neck and empty into the right and left subclavian veins (see figure 13.32, slide 97).
The internal jugular veins, which are somewhat larger than the external jugular veins, arise form numerous veins and venous sinuses of the brain and from deep veins in parts of the face and neck. They descend through the neck and join the subclavian veins. These unions of the internal jugular and subclavian veins form large brachiocephalic veins on each side. The vessels then merge an give rise to the superior vena cava, which enters the right atrium.
Figure 13.32

98. D. Veins from the Upper Limb and Shoulder
1. The upper limb is drained by superficial and deep veins.
2. The basilic and cephalic veins are major superficial veins.
3. The major deep veins include the radial, ulnar, brachial, and axillary veins.
A set of deep veins and a set of superficial ones drain the upper limb. The deep veins generally parallel the arteries in each region and have similar names, such as the radial veins, ulnar veins, brachial veins, and axillary vein. The superficial veins connect in complex networks just beneath the skin. They also communicate with the deep vessels of the upper limb, providing many alternate pathways through which blood can leave the tissues (see figure 13.33, slide 99).
The basilic vein ascend from the forearm to the middle of the arm, where it penetrates deeply and joins the brachial vein. The basilic and brachial veins merge, forming the axillary vein. The cephalic vein courses upward form the hand to the shoulder. In the shoulder, it pieces the tissues and empties into the axillary vein. Beyond the axilla, the axillary vein becomes the subclavian vein.

99. The major veins of the upper limb and shoulder
The major veins of the upper limb and shoulder. Through drawn as one vessel, many of the peripheral veins are in pairs.
Figure 13.33

100. E. Veins from the Abdominal and Thoracic Walls
1. Tributaries of the brachiocephalic and azygos veins drain the abdominal and thoracic walls.
Tributaries of the brachiocephalic and azygos veins drain the abdominal and thoracic walls. For example, the brachiocephalic vein receives blood from the internal thoracic vein, which generally drains the tissues the internal thoracic artery supplied, some intercostal veins also empty into the brachiocephalic vein.
The azygos vein originate in the dorsal abdominal wall and ascends through the mediastinum on the right side of the vertebral column to join the superior vena cava. It drains most of the muscular tissue in the abdominal and thoracic walls.

101. F. Veins from the Abdominal Viscera
1. Blood draining from the intestines enters the hepatic portal system and flows to the liver first rather than into general circulation.
2. The liver can process the nutrients absorbed during digestion as well as remove bacteria.
Most veins carry blood directly to the atria of the heart. Veins that drain the abdominal viscera are exceptions (see figure 13.34, slide 103). They originate in the capillary networks of the stomach, intestines, pancreas, and spleen and carry blood from these organs through a hepatic portal vein to the liver. This unique venous pathway is called the hepatic portal system.
About 80% of the blood flowing to the liver in the hepatic portal system comes from capillaries in the stomach and intestines, and is oxygen-poor but nutrient-rich. The liver handles these nutrients in a variety of ways. The liver helps regulate blood concentrations of recently absorbed amino acids and lipids by modifying them into forms cells can use, by oxidizing them, or by changing them into storage forms. The liver also stores certain vitamins and detoxifies harmful substances.

102. 3. Hepatic veins drain the liver, gastric
3. Hepatic veins drain the liver, gastric veins drain the stomach, superior mesenteric veins lead from the small intestine and colon, the splenic vein leaves the spleen and pancreas, and the inferior mesenteric vein carries blood from the lower intestinal area.
Tributaries of the hepatic portal vein include:
Right and left gastric veins from the stomach
Superior mesenteric vein from the small intestine, ascending colon, and transverse colon
Splenic vein from a convergence of several veins draining the spleen, the pancreas, and a portion of the stomach. Its larges tributary, the inferior mesenteric vein, bring blood upward from the descending colon, sigmoid colon, and rectum.

103. Veins that drain the abdominal viscera.
Figure 13.34

104. G. Veins from the Lower Limb and Pelvis
1. Deep and superficial veins drain the leg and pelvis.
2. The deep veins include the anterior and posterior tibial veins which unite into the popliteal vein and femoral vein; superficial veins include the small and great saphenous veins.
3. These veins all merge to empty into the common iliac veins.
Veins that drain blood from the lower limb are divide into deep and superficial groups, as is the case in the upper limb (see figure 13.35, slide 105). The deep veins of the leg, such as the anterior and posterior tibial veins, are names for the arteries they accompany. At the level of the knee these vessels form a single trunk, the popliteal vein. This vein continues upward through the thigh as the femoral vein, which in turn becomes the external iliac vein.
The superficial veins of the foot, leg, and thigh connect to form a complex network beneath the skin.. These vessels drain into two major trunks—the small and great saphenous veins.
The small saphenous vein ascend along the back of the calf, enters the popliteal fossa, and joins the popliteal vein. The great saphenous vein, which is the longest vein in the body, ascend tin front of the medial malleolus and extends upward along the medial side of the leg and thigh. In the thigh, it penetrates deeply and joins the femoral vein. Near its termination, the great saphenous vein receives tributaries from a number of vessels that drain the upper thigh, groin, and lower abdominal wall.
In the pelvic region , vessels leading to the internal iliac vein carry blood away from the organs of the reproductive, urinary, and digestive systems, the internal iliac veins unite with the right and left external iliac veins to form the common iliac veins. These vessels, in turn, merge to produce the inferior vena cava.

105. Figure 13.35 Major Vessels of the Venous System
Major vessels of the venous system. For simplification, the paired brachial, radial, ulnar, anterior and posterior tibial veins are depicted as singular vessels.
Figure Major Vessels of the Venous System

106. Relationship of Cardiovascular System to the Other Ten Body Systems
Relationship of Cardiovascular System to the Other 10 Body Systems

107. Relationship of Cardiovascular System to the Other 10 Body Systems
Anastomosis – connection between two blood vessels, sometimes produced surgically.
Angiospasm – muscular spasm in the wall of a blood vessel.
Arteriograph – injection of radiopague solution into the vascular system for X-ray examination of arteries.
Cardiac tamponade – compression of the heart by fluid accumulating within the pericardial cavity.
Congestive heart failure – inability of the left ventricle to pump adequate blood to cells.
Cor pulmonale – pulmonary hypertension and hypertrophy of the right ventricle
Embolectomy – removal of an embolus through an incision in a blood vessel.
Relationship of Cardiovascular System to the Other 10 Body Systems

108. Relationship of Cardiovascular System to the Other 10 Body Systems
Endarterectomy – removal of the inner wall of an artery to reduce an arterial occlusion.
Palpitation – awareness of a heartbeat that is unusually rapid, strong, or irregular.
Pericardiectomy – excision of the pericardium
Phlebitis – inflammation of a vein, usually in the lower limbs.
Phlebotomy – incision or puncture of a vein to withdraw blood.
Sinus rhythm – the normal cardiac rhythm regulated by the S-A node.
Thrombophlebitis – formation of a blood clot in a vein in response to inflammation of the venous wall.
Valvotomy – incision a valve.
Venography – injection of radiopague solution into the vascular system for X-ray examination of veins