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19. The Blood Vessels
Introduction to Hemodynamics

19. The Blood Vessels

Introduction to Hemodynamics

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Textbook Question
When we are cold or the external temperature is low, most venous blood returning from the distal part of the arm travels in the deep veins where it picks up heat (by countercurrent exchange) from the nearby brachial artery en route. However, when we are hot, and especially during exercise, venous return from the distal arm travels in the superficial veins and those veins tend to bulge superficially in a person who is working out. Explain why venous return takes a different route in the second situation.
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Textbook Question
Your friend Jillian, who knows little about science, is reading a magazine article about a patient who had an 'aneurysm at the base of his brain that suddenly grew much larger.' The surgeons' first goal was to 'keep it from rupturing,' and the second goal was to 'relieve the pressure on the brain stem and cranial nerves.' The surgeons were able to 'replace the aneurysm with a section of plastic tubing,' so the patient recovered. Jillian asks you what all this means. Explain.
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Textbook Question
Edema is a common clinical problem. On your first day of a clinical rotation, you encounter four patients who have edema for different reasons. Your challenge is to explain the edema in terms of either an increase or a decrease in one of the four pressures that causes bulk flow (see Focus Figure 18.1). (1) First you encounter Mrs. Taylor in the medical unit awaiting a liver transplant. What is the connection between liver failure and her edema? (2) Next in the obstetric ward, Mrs. So is experiencing premature labor and has edema in her legs. Which bulk flow pressures might be altered here? (3) In emergency, Mr. Herrera is in anaphylactic shock. His capillaries have become leaky, allowing plasma proteins that are normally kept inside the blood vessels to escape into the interstitial fluid. Which of the bulk flow pressures is altered in this case and in what direction is the change? (4) Finally, in oncology Mrs. O'Leary is recovering from breast cancer surgery. Her right breast and all of her axillary lymph nodes were removed. Unfortunately, this severed most of the lymphatic vessels draining her right arm. You notice that this arm is quite edematous. Why? Mrs. O'Leary is given a compression sleeve to wear on this arm to help relieve the edema. Which of the bulk flow pressures will be altered by the compression sleeve?
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