Final Exam (Lecture 60) - Implantation and Pregnancy

Question 1

Describe the four steps of embryonic preparation between syngamy and implantation.

Answer 1

• Development of the embryo
• Hatching
• Post-hatching embyrogenesis
• Prevention of luteolysis

Question 2

For post-hatching embryogenesis, where is the amnion formed? Where is the chorioallantoic membrane formed?

Answer 2

1) Amnion = “implantation pole”

2) Chorioallantoic membrane = distal pole

Question 3

Describe how ruminants and swine embryos differentially signal to the uterus that implantation is imminent, and how this signaling influences the ovary.

Answer 3

1) Ruminant embryos release INF-tau that decreases oxytocin receptors, thus preventing the release of the luteolytic hormone PGF2-alpha.

2) Swine embryos release estrogen that re-routes PFG2-alpha to the uterine lumen where it is destroyed, thus preventing ovarian luteolysis.

Question 4

What is the role of CG in maintaining the early part of pregnancy?

Answer 4

CG is an LH-like hormone released from implanted trophoblasts and this hormone maintains progesterone release from the CL.

Question 5

Describe the importance of accessory CL in the maintenance of early to mid-pregnancy.

Answer 5

Accessory CLs are formed to assist in progesterone release as the primary CL undergoes its inevitable involution.

Question 6

Describe the hormonal importance of the placenta in the maintenance of mid-pregnancy and beyond.

Answer 6

In some species, the placenta assumes the responsibility of producing most of the progesterone needed for the maintenance of pregnancy.