Chapter 33

After studying this chapter, you should be able to:

• Define the special features of the circulation in the brain, coronary vessels, skin, and fetus, and how these are regulated.
• Describe how cerebrospinal fluid (CSF) is formed and reabsorbed, and its role in protecting the brain from injury.
• Understand how the blood—brain barrier impedes the entry of specific substances into the brain.
• Delineate how the oxygen needs of the contracting myocardium are met by the coronary arteries, and the consequences of their occlusion.
• List the vascular reactions of the skin and the reflexes that mediate them.
• Understand how the fetus is supplied with oxygen and nutrients in utero, and the circulatory events required for a transition to independent life after birth.

The distribution of the cardiac output to various parts of the body at rest in a normal man is shown in Table 33–1. The general principles described in preceding chapters apply to the circulation of all these regions, but the vascular supplies of many organs have additional special features that are important to their physiology. The portal circulation of the anterior pituitary is discussed in Chapter 18, the pulmonary circulation in Chapter 35, the renal circulation in Chapter 37, and the circulation of the splanchnic area, particularly the intestines and liver, in Chapters 25 and 28. This chapter is concerned with the special circulations of the brain, the heart, and the skin, as well as the placenta and fetus.

Table 33–1 Resting Blood Flow and O2 Consumption of Various Organs in a 63-kg Adult Man with a Mean Arterial Blood Pressure of 90 mm Hg and an O2 Consumption of 250 mL/min.

### Vessels

The principal arterial inflow to ...

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