Male and Female Reproductive Physiology: Control of Testicular and Ovarian Function 2

Question 1

What triggers the LH surge?

Answer 1

A rise in amount of oestrogen being produced.

Question 2

What does the LH surge do?

Answer 2

Increases GnRH pulse frequency

Induces and maintains GnRH receptors in the anterior pituitary. (more responsive anterior pituitary to GnRH)

Granulosa cells start to express LH receptors as well as theca cells.

LH surge triggers ovulation about 36 hours later.

Formation of the corpus luteum.

Question 3

How does the LH surge trigger ovulation?

Answer 3

LH surge triggers ovulation about 36 hours later. This is by stimulating follicular maturation, stimulates granulosa cells to synthesize progesterone (essential for ovulation), resumption of oocyte meiosis, upregulates cyclooxygenase-2 which is important for production of proteolytic enzymes, follicle wall degradation, and release of secondary oocyte (Ovulation)

Question 4

What does the corpus luteum produce during the luteal phase?

Answer 4

Inhibin A to reduce FSH secretion

High levels of oestradiol

Progesterone which inhibits oestradiol effects when high in levels.

Question 5

What does the corpus luteum of the embryo do in the absence of implanting embryo?

Answer 5

CL undergoes atresia leading to drop in progesterone, E2, and inhibin.

Question 6

How is the menstrual cycle timed?

Answer 6

First day of menses (bleeding) is day 1 of the cycle.

Length of cycle = interval between consecutive menses

Average interval = 28 days

Common variation is 21 to 35 days

Question 7

How long is the luteal phase?

Answer 7

Luteal phase is usually constant at 12 - 14 days

Question 8

How long is the follicular phase?

Answer 8

Follicular phase varies in length. Ovulation occurs 12 - 14 days prior to next menses.