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MCAT Biology Question — Blood Pressure

  • by Kerry Goldstein
  • Jan 15, 2015
  • MCAT Biology, MCAT Blog, MCAT Question of the Day

Physiologic dead space is any region in the lungs where air is entering the alveoli, but no oxygen exchange is taking place because the alveolus is not adequately perfused with blood. If a person’s pulmonary arterioles have constricted so much that the lungs have a significant increase in physiologic dead space, the constriction would most directly result in increased blood pressure where?

A) Aorta

B) Vena cava

C) Left ventricle

D) Right ventricle

 

 

Explanation

A) Aorta

B) Vena cava

C) Left ventricle

D) Right ventricle

The blood flows from the right ventricle into the pulmonary arteries and then the pulmonary arterioles. Constriction in the pulmonary arterioles would create a “back up” of blood in the pulmonary arteries and the right ventricle, thus increasing pressure. More generally, we may note that any time there is a blockage in the circulatory system, the pressure behind the blockage increases, and the pressure downstream from the blockage decreases.

 

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