Reproductive endocrinology

Question 1

When does oogenesis begin, complete and cease?

Answer 1

Begins in utero, is suspended for many years and resumes at puberty

Completes with fertilisation

Ceases with menopause

Question 2

What is oogonia?

Answer 2

Completion of last pre-meiotic division to oocytes

Question 3

What happens at the start of each menstrual cycle to the primordial follicles?

Answer 3

Several follicles enlarge and a cavity forms around the ovum within the follicle called antrum formation

Question 4

What is contained within each primordial follicle?

Answer 4

An immature ovum

Question 5

What is the cavity around the ovum within the follicle during antrum formation filled with?

Answer 5

Follicular fluid

Question 6

During which day of the menstrual cycle does a dominant follicle become apparent?

Answer 6

6th

Question 7

What is the dominant follicle in menstruation?

Answer 7

At the start of the cycle, several follicles enlarge

One follicle in one ovary tends to grow more rapidly than the others in the first 6 days

The others regress, becoming atretic follicles

Question 8

What is the first half of the menstrual cycle called?

Answer 8

Follicular phase

Question 9

What happens during the follicular phase?

Answer 9

Maturation of egg, ready for ovulation at midcycle

Question 10

What signals the end of the follicular phase?

Answer 10

Ovulation

Question 11

What is the primary source of circulating estrogen?

Answer 11

The granulosa cells of the ovaries

Question 12

At birth, what is the primary oocyte surrounded by?

Answer 12

A single layer of granulosa cells

Question 13

What is a primary follicle?

Answer 13

The primary oocyte surrounded by a single layer of granulosa cells

Question 14

How does the primary follicle become the secondary follicle?

Answer 14

Oocyte grows (x1000) and follicle expands and becomes differentiated under hormonal influence

Question 15

What happens on about the 14th day of the cycle after the mature follicle has formed and the dominant follicle apparent?

Answer 15

The distended follicle ruptures and released the ovum into the abdominal cavity

This is ovulation

Question 16

What happens to the ovum that has been ovulated into the abdominal cavity?

Answer 16

Picked up by the fimbrae of the uterine tube (oviducts) and transported along to the uterus and out through the vagina

(Unless fertilisation occurs)

Question 17

What happens to the follicular cells left behind after ovulation?

Answer 17

Undergo lutenization to form the corpus luteum

Question 18

What hormone does the corpus luteum secrete?

Answer 18

Progesterone

Question 19

What is the main hormone secreted during the follicular phase?

Answer 19

Oestrogen

Question 20

How long does the corpus luteum grow after ovulation?

Answer 20

For 8-9 days

Question 21

What event signals the start of a new follicular phase?

Answer 21

The degeneration of the corpus luteum

It will survive no longer than 14 days after ovulation

Question 22

What is growth of the corpus luteum dependant on?

Answer 22

Developing a blood supply

Question 23

What happens to the corpus luteum if pregnancy occurs?

Answer 23

It persists and it secretes increasing quantities of oestrogen and progesterone until after delivery

Question 24

At what time do ova undergo the first part of the first meotic division and what happens after this?

Answer 24

At birth

There are roughly 2 million ova at this point, with 50% being atreic

The normal ones undergo the first part of the first meiotic division, and arrest in prophase in which those that survive persist into adulthood

Question 25

At what time do ova complete the first meiotic division?

Answer 25

Just before ovulation

Question 26

What happens to the daughter cells of the first meiotic division?

Answer 26

One, the secondary oocyte, recieves most of the cytoplasm The other, the first polar body, fragments and disappears

Question 27

When does the start of the second meiotic division occur and in which cells?

Answer 27

The second meiotic division only occurs in the secondary oocyte: the surviving daugther cell from the first meiotic division Second meiotic divison occurs almost immediately after the first, but is arrested at metaphase

Question 28

When is the second meiotic division completed?

Answer 28

When a sperm penetrates the oocyte This casts off the second polar body and the fertilised ovum proceeds to create a baby

Question 29

Which hormone stimulates the anterior pituitary to produce ovarian hormones?

Answer 29

GnRH

Question 30

What are the reproductive hormones that the anterior pituitary secretes?

Answer 30

FSH LH

Question 31

What does FSH do?

Answer 31

Acts on ovary Stimulates development of follicles FSH + LH stimulate secretion of oestradiol and ovulation

Question 32

What does LH do?

Answer 32

Acts on ovary Stimulates follicle maturation, ovulation and development of the corpus luteum FSH + LH stimulate secretion of oestradiol and ovulation

Question 33

What happens in the hypothalamus when the follicular phase begins?

Answer 33

Hypothalamus secretes GnRH Ant pituitary secretes FSH and a little LH Up to 15 follicles begin to mature and form granulosa cells and theca cells Oestrogen suppresses FSH production by the ant. pituitary (selection of dominant follicle)

Question 34

What is the role of the theca cells and granulosa cells during the follicular phase?

Answer 34

The theca cells produce androgen which is converted by the granulosa (aromatase) to oestradiol (thickens endometrium/thins cervical mucus)

Question 35

What happens in the hypothalamus once the dominant follicle has been selected?

Answer 35

Granulosa in the dominant follicle express LH receptor High levels of oestrogen at mid cycle cause hypothalamus to release GnRH Causes FSH and LH surge from ant. pituitary

Question 36

What happens to the levels of LH and FSH during ovulation?

Answer 36

They fall

Question 37

What happens to the remaining granulosa during the luteal phase?

Answer 37

Become part of the corpus luteum and secrete progesterone

Question 38

What happens to thecal cells during the luteal phase?

Answer 38

Convert androgen to oestrogen

Question 39

What happens 12 days into the luteal phase to oestrogen and progesterone levels?

Answer 39

If there is no hCG production from an embryo, the corpus luteum degenerates forming the corpus albicans This reduces the levels of oestrogen and progesterone, starting the cycle again by removing negative feedback

Question 40

At which stage of pregnancy does the corpus luteum degenerate to the corpus albicans?

Answer 40

6 weeks - the placenta takes over the function of secreting progesterone