General Anatomy

Objectives

When you have completed this section, you should be able to

• trace the usual route taken by the blood from the heart and back again, and describe the common variations on this route;
• describe the structure of a blood vessel; and
• describe the different types of arteries, capillaries, and veins.

Think About It

From figure 20.7 and your other knowledge, calculate the approximate volume of blood in the systemic capillaries. What percentage of the systemic blood is this?

Key Point Review

1. Explain how an anastomosis and a portal system differ from the simple artery -> capillary -> vein scheme of circulation.

2. Name the three tunics of a typical blood vessel and explain how they differ from each other.

3. Describe the route of blood flow through a capillary bed.

4. Contrast the two types of capillaries.

5. Explain why many veins have valves but arteries do not.

Blood Flow, Pressure, and Resistance

Objectives

When you have completed this section, you should be able to

• explain the relationship between blood pressure, resistance, and flow;
• describe how blood pressure is expressed and how pulse pressure and mean arterial blood pressure are calculated;
• describe three factors that determine resistance to blood flow; and
• explain how vasomotion influences blood flow and describe some local, neural, and hormonal influences on vasomotion.

Key Point Review

6. For a healthy 15-year-old girl at rest, what would be typical readings for systolic pressure, diastolic pressure, pulse pressure, and mean arterial blood pressure?

7. Explain why arterial blood flow is pulsatile and venous flow is not.

8. According to Poiseuille's law, which factors are directly proportional to blood flow? Which are inversely proportional?

9. What are the three primary mechanisms for controlling blood vessel radius? Give a brief explanation of each.

Capillary Exchange

Objectives

When you have completed this section, you should be able to

• describe the routes by which fluid passes through the capillary endothelium;
• describe the mechanisms and forces involved in capillary fluid exchange; and
• calculate the net pressures that cause capillary filtration and reabsorption.

Key Point Review

10. List the three mechanisms of capillary exchange and relate each one to the structure of capillary walls.

11. What forces favor capillary filtration? What forces favor reabsorption?

12. How can a capillary be shifted from a predominantly filtering to a predominantly reabsorbing role?

Venous Return and Circulatory Shock

Objectives

When you have completed this section, you should be able to

• explain how blood in the veins is returned to the heart;
• discuss the importance of physical activity in venous return; and
• discuss several causes of circulatory shock and name and describe the stages of shock.

Think About It

Why is venous pooling not a problem when you are sleeping and the skeletal muscle pump is inactive?

Key Point Review

13. Explain how respiration aids venous return.

14. Explain how muscular activity and venous valves aid venous return.

15. Define circulatory shock. What are some of the causes of low venous return shock?

Special Circulatory Routes

Objective

When you have completed this section, you should be able to

• explain how the brain maintains stable perfusion;
• discuss the causes and effects of strokes and transient ischemic attacks;
• explain the mechanisms that increase muscular perfusion during exercise; and
• contrast the blood pressure of the pulmonary circuit with that of the systemic circuit, and explain why the pressure difference is important in pulmonary function.

Think About It

What abnormal skin coloration would result from pulmonary edema?

Key Point Review

16. In what conspicuous way does blood flow to the brain differ from flow to the skeletal muscles?

17. How does a stroke differ from a transient ischemic attack? Which of these bears closer resemblance to a myocardial infarction?

18. How does the low hydrostatic blood pressure in the pulmonary circuit affect the fluid dynamics of the capillaries there?

19. Contrast the vasomotor responses to hypoxia in the lungs and skeletal muscles.

Anatomy of the Pulmonary Circuit

Objective

When you have completed this section, you should be able to

• trace the route taken by blood in the pulmonary circuit.

Key Point Review

20. Trace the flow of an RBC from right ventricle to left atrium, naming the vessels along the way.

21. The lungs have two separate arterial supplies. Explain their functions.

Anatomy of the Systemic Arteries

Objectives

When you have completed this section, you should be able to

• identify the principal arteries of the systemic circuit; and
• trace the flow of blood from the heart to any major organ.

Think About It

There are certain similarities between the arteries of the hand and foot. What arteries of the wrist and hand are most comparable in arrangement and function to the arcuate artery and plantar arch of the foot?

Key Point Review

22. Concisely contrast the destinations of the external and internal carotid arteries.

23. Briefly state the tissues that are supplied with blood by (a) the circle of Willis, (b) the celiac trunk, (c) the superior mesenteric artery, and (d) the external iliac artery.

24. Trace the path of an RBC from the left ventricle to the metatarsal arteries. State two places along this path where you can palpate the arterial pulse.

Anatomy of the Systemic Veins

Objective

When you have completed this section, you should be able to

• identify the principle veins of the systemic circuit and trace the flow of blood from any major organ to the heart.

Key Point Review

25. If you were dissecting a cadaver, where would you look for the internal and external jugular veins? What muscle would help you distinguish one from the other?

26. How do the vertebral veins differ from the vertebral arteries in their superior terminations?

27. By what route does blood from the abdominal wall reach the superior vena cava?

28. Trace one possible path of an RBC from the fingertips to the right atrium, naming the veins along the way.

29. State two ways in which the great saphenous vein has special clinical significance. Where is this vein located?

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