Luteal Regression And Menstruation

Question 1

When no pregnancy occurs

Answer 1

the CL will regress around 10 days post-ovulation-termed luteolysis.

Question 2

When pregnancy occurs

Answer 2

the CL is maintained, and it continues to produce progesterone.

Question 3

CL regression consists of two phases, the control mechanisms of which are complex and differ between species:

Answer 3

1. Functional luteolysis
2. Structural luteolysis

Question 4

Functional luteolysis:

Answer 4

may be a result of either low LH or high estrogen or both.

Question 5

Structural luteolysis:

Answer 5

in humans may involve apoptosis, although autophagocytosis has also been proposed to be the main mechanism involved in this process.

Question 6

Withdrawal of the ovarian steroids progesterone and estrogen:

Answer 6

1. occurs with the onset of luteal regression. The CL physically decreases in size and is ultimately replaced by connective tissue. As a result of the whitish connective tissue, the CL is now called the corpus albicans (Latin = ‘whitish body’).
2. stimulates the release of PGF2-a, which causes vasospasms of the spiral arteries and contractions of the myometrium (menstrual cramps).
3. disrupts the blood supply to the endometrium that leads to hypoxia and tissue necrosis. The functionalis layer of the endometrium is thus sloughed off and expelled from the uterus by the uterine contractions leaving behind the basalis layer of the endometrium. The basalis will be the tissue foundation for the secretory endometrium of the next menstrual cycle.
4. removes steroidal negative feedback on the pituitary. The pituitary gonadotropin output will therefore increase and a new menstrual cycle will ensue.