Early Development, Devel. Physiol., Dr. D. Penney
8. The embryonic heart at the 16 somite stage (25 days post-ovulation):
A. has a ventricle separated into right and left chambers
B. has an atrium made up of a single chamber
C. is a straight tube made up of two tissue layers
D. is an "S" shaped structure made up of bulbus, truncus, ventricle, atria and sinus venosus
E. B & D
Self-Assessment - Module 21: (Cont.)
9. The site of greatest pressure drop, thus resistance, on the venous side of the fetal circulation occurs across the:
A. umbilical artery
B. umbilical vein
C. inferior vena cava
D. collecting veins of the placenta
E. ductus venosus
10. Of the blood which returns to the fetal heart, what percent flows to the left ventricle via the foramen ovale and what percent to the right ventricle?
A. 4, 96
B. 16, 84
C. 28, 72
D. 50, 50
E. 63, 37
11. Which one of the following statements is INCORRECT regarding the ductus arteriosus?
A. it is a shunt from the pulmonary artery to the aorta in the fetus
B. blood flow may take place from the aorta to the pulmonary artery after birth, prior its closing.
C. it is a shunt directly from the right atrium to the left atrium
D. right to left blood flow decreases with the first breath after birth due to falling pulmonary vascular resistance.
E. the smooth muscle in its walls is sensitive to rising P02
12. Which of the following statements BEST characterizes the ductus venosus of the fetus?
A. it receives most of its blood from the umbilical vein
B. it sends its blood to the liver
C. both of the above statements are correct
D. it contains blood of a lower oxygen content than the blood in the umbilical arteries
E. statements A and D are correct
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