Later Development, Develop. Physiol., Dr. D. Penney

Self-Assessment - Module 22:

1. Which one of the following statements is incorrect regarding the ductus arteriosus?
   1. it is a shunt from the pulmonary artery to the aorta in the fetus
   2. blood flow may take place from the aorta to the pulmonary artery after birth, prior its closing.
   3. it is a shunt directly from the right atrium to the left atrium
   4. right to left blood flow decreases with the first breath after birth due to falling pulmonary vascular resistance.
   5. the smooth muscle in its walls is sensitive to rising PO₂

2. The foramen ovale
   1. closes anatomically within seconds to minutes after birth
   2. permits about twice a much blood to pass to the left atrium as that which flows into the right ventricle during fetal life
   3. closes functionally at birth because left atrial pressure rises above right atrial pressure
   4. is a shunt around the liver, allowing blood to flow directly from the umbilical vein to the right atrium
   5. is a round hole in the interventricular septum between the right and left hearts

3. At birth:
   1. pulmonary vascular resistance falls shortly after the first breath, because of pulmonary arteriolar vasodilation
   2. the initial left atrial pressure rise occurs because the ductus arteriosus has closed.
   3. the foramen ovale closes because of umbilical cord clamping.
   4. right and left shunting of blood through the ductus arteriosus continues right up till the ductus closes.
   5. the adult circulation is functional within a few minutes after birth.

4. Hypoxia has the following effects on the fetus, except
   1. increase in plasma catecholamines
   2. increase in use of glycolytic pathway and lactate
   3. increase in heart rate
   4. decrease on fetal blood pH
   5. decrease in fetal oxygen consumption

5. Aging generally results in the following changes in the cardiovascular system, except:
   1. increased reliance by the heart on the Frank-Starling mechanism for increased stroke volume during exercise, as opposed to increases in inotropicity
   2. decreased (shortened) left ventricle ejection time
   3. cardiac hypertrophy
   4. increased stiffness (decreased compliance) of the arterial wall
   5. decreased maximal heart rate

6. In the aged heart at rest, left ventricle ejection time is generally increased, while stroke volume is decreased ( T / F )

7. In the fetal human heart, muscle cells constitute 75% or more of the total cells by number, while in the adult heart muscle cells constitute about 25% of the total cells. ( T / F )

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