Later Development, Develop. Physiol., Dr. D. Penney
Self-Assessment - Module 22:
- Which one of the following statements is incorrect regarding the ductus arteriosus?
- it is a shunt from the pulmonary artery to the aorta in the fetus
- blood flow may take place from the aorta to the pulmonary artery after birth, prior its closing.
- it is a shunt directly from the right atrium to the left atrium
- right to left blood flow decreases with the first breath after birth due to falling pulmonary vascular resistance.
- the smooth muscle in its walls is sensitive to rising PO2
- The foramen ovale
- closes anatomically within seconds to minutes after birth
- permits about twice a much blood to pass to the left atrium as that which flows into the right ventricle during fetal life
- closes functionally at birth because left atrial pressure rises above right atrial pressure
- is a shunt around the liver, allowing blood to flow directly from the umbilical vein to the right atrium
- is a round hole in the interventricular septum between the right and left hearts
- At birth:
- pulmonary vascular resistance falls shortly after the first breath, because of pulmonary arteriolar vasodilation
- the initial left atrial pressure rise occurs because the ductus arteriosus has closed.
- the foramen ovale closes because of umbilical cord clamping.
- right and left shunting of blood through the ductus arteriosus continues right up till the ductus closes.
- the adult circulation is functional within a few minutes after birth.
- Hypoxia has the following effects on the fetus, except
- increase in plasma catecholamines
- increase in use of glycolytic pathway and lactate
- increase in heart rate
- decrease on fetal blood pH
- decrease in fetal oxygen consumption
- Aging generally results in the following changes in the cardiovascular system, except:
- increased reliance by the heart on the Frank-Starling mechanism for increased stroke volume during exercise, as opposed to increases in inotropicity
- decreased (shortened) left ventricle ejection time
- cardiac hypertrophy
- increased stiffness (decreased compliance) of the arterial wall
- decreased maximal heart rate
- In the aged heart at rest, left ventricle ejection time is generally increased, while stroke volume is decreased ( T / F )
- 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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