Session 2 : Reproduction

Question 1

Outline the basic HPA axis which controls gametogenesis in males and females?

Answer 1

Hypothalamus - GnRH
Anterior pituatary Gonadotroph cells - FSH & LH
Act on Gonads : Gonadal steroids (Oestrogen or Progesterone)
Steroids act on the reproductive tract & will also (negatively feedback to the hypothalamus & AP)

Question 2

Outline what happens in the follicular phase of the menstural cycle?

Answer 2

Early follicular stage : FSH is high (no inhibin or oestrogen). There will be development and enlargement of a number of primordial follicles to primary follicles. FSH binds to the granulosa cells.
When follicles have theca interna they can make oestrogen and inhibin.
Mid folicular stage : only one or two follicles will be left as the inhibin would inhibit FSH and development of follicles. There will be elevated levels of LH as oestrogen has a positive feedback effect to increase it.
Pre ovulation : Surge in LH due to oestrogen and inhibin effects. Granulosa cells will become sensitive to LH to then make progesterone. This will modulate the GnRH pulse generator, both oestrogen and progesterone increase the anterior pituatary sensitivity to GnRH.

Question 3

What happens in ovulation?

Answer 3

There is an LH surge : this will cause the contractions of the muscular uterine wall & increase in collegenase activity to release the egg from the ovary.
Meiosis 1 is complete and meiosis 2 begins, this is arrested in P2.

Question 4

What happens in the proliferative phase ?

Answer 4

Elevated levels of oestrogen.
Fallopian tube functioning, cervical mucus thin and alkaline, thickening of the endometrium, growth and motility of the myometrium, vaginal changes & skin, hair & metabolism changes

Here the uterine walls are rapidly profilerating so that they are prepared for the future conceptus.

Question 5

What happens to the effect of oestrogen in the absence of progesterone ?

Answer 5

At moderate levels it can inhibit the HPA axis

At higher levels it will postively feedback to cause the LH surge

Question 6

What happens to the effect of oestrogen in the presence of progesterone ?

Answer 6

Progesterone increases the inhibitory effect of oestrogen, even at higher levels (so there is no LH surge.)

Question 7

How is oestrogen made by the granulosa and thecal cells?

Answer 7

LH -> theca interna - > androgens (androsterone)

FSH -> granulosa cells -> converts the androgen into oestrogen

Question 8

Describe the regulatory effects of the hormone testosterone ?

Answer 8

maintenance of the male internal genitalia
(prostate, seminal vesicles, vas deferens, epididymis) 
metabolic effects (anabolic action) 
behavioural effects-aggression & sexual activity

Question 9

Describe the determinative effects of testosterone ?

Answer 9

This will be the secondary characteristics of males: facial hair, male pattern baldness, hair, smell, increase in body size in comparison to females, hoarseness in voice, central nervous effects, effects on the body composition (more muscle to fat ratio)

Question 10

What is the role of inhibin in males ?

Answer 10

Inhibin will be used to inhibit the release of FSH.
This will then lower the activity of the Sertoli cells.
This will reduce spermatogenesis.

Question 11

What hormone are the Sertoli cells sensitive to and what is the effect?

Answer 11

They are sensitive to FSH. This will facilitate spermatogenesis and the creation of substances which potentiate the process.
Note: testosterone is also really important in this process as well.

Question 12

What are the leydig cells responsive to and what is the effect?

Answer 12

Leydig cells are sensitive to LH.

This will the on cause an increase in testosterone formation.

Question 13

What things can effect the menstrual cycle?

Answer 13

Low body weight ( effects the onset of puberty as well)
Emotional stress
Physiology : pregnancy or lactation

Question 14

What is the corpus luteum ?

Answer 14

The corpus luteum is the remnant of the follicular cells which surrounded the egg. The granulosa and theca cells become luteinised (become visibly yellow).

Question 15

What is the role of the corpus luteum?

Answer 15

The role of the corpus luteum is to make oestrogen and progesterone the hormones which will be necessary to maintain the epithelium of the uterus in preparation for implantation .

Question 16

At what point does the future conceptus signal to effect the menstrual cycle ?

Answer 16

Week of twos: syncitiotrophoblast
This will produce hcg (human chorionic gonadotropin) this will have a luteinising effect upon the corpus luteum, and to ensure the maintenance of the luteal phase.

Question 17

What happens in menses?

Answer 17

A sudden fall in progesterone and oestrogen levels:
The elaborate secretary epithelium of the endometrium
collapses – this is apoptotic cell death. The tissue is shed as a menstrual bleed, spiral arteries contract to reduce blood loss.

Question 18

What is the role of the corpus luteum in pregnancy ?

Answer 18

The corpus luteum will ensure there is oestrogen and progesterone which will inhibit the ovarian cycle , maintain the uterine lining until the placenta can take over the role. This happens at 4 months.

Question 19

In males which hormones potentiate the effect of LH?

Answer 19

The hormones prolactin and inhibin .

Question 20

What happens in the secretory phase of the uterine cycle ?

Answer 20

The main hormone at play progesterone but also oestrogen.
The roles include :
Making cervical mucus Acidic and thick to prevent infection and polyspermy.
Further thickening of endometrium into secretory form Thickening of myometrium, but reduction of motility
Changes in mammary tissue
Increased body temperature
Metabolic changes Electrolyte changes

Question 21

Outline what happens in the luteal phase of the ovarian cycle?

Answer 21

Surge of LH will begin to decrease as progesterone increases ( has an inhibitory effect)
There is the development of the corpus luteum.

Question 22

How long is the menstural cycle ?

Answer 22

21-35 days 
Follicular stage variable 
luteal phase (-/+2) 14 days