Anatomy, Physiology and Fetal Development Flashcards

Which hormone, secreted by the trophoblast, maintains the corpus luteum in early pregnancy?

Answer: Human chorionic gonadotropin (hCG)

hCG is produced by the trophoblast after implantation. It signals the corpus luteum to keep making progesterone until the placenta takes over, around 8-12 weeks.

In fetal circulation, which structure shunts blood from the right atrium directly to the left atrium?

Answer: Foramen ovale

The foramen ovale lets most oxygenated blood bypass the nonfunctional fetal lungs by passing from the right atrium to the left atrium. It normally closes after birth when pulmonary pressure falls.

Which vessel carries oxygenated blood from the placenta to the fetus?

Answer: The umbilical vein

The single umbilical vein carries oxygen- and nutrient-rich blood to the fetus. The two umbilical arteries carry deoxygenated blood back to the placenta.

Which pelvic type is classically considered most favorable for vaginal birth?

Answer: Gynecoid

The gynecoid pelvis has a rounded inlet, a wide subpubic arch, and generous diameters. These suit passage of a fetal head in most presentations.

Implantation of the blastocyst typically occurs about how many days after fertilization?

Answer: 6-10 days

The blastocyst reaches the uterus about 3-5 days after fertilization and implants in the endometrium around days 6-10.

Around which gestational age does the placenta take over progesterone production from the corpus luteum (the luteal-placental shift)?

Answer: 8-12 weeks

The placenta becomes the main source of progesterone at roughly 8-12 weeks. This is why pregnancy loss from corpus luteum removal is unlikely after about 10 weeks.