The gonads: Development and function of the reproductive system (dave's notes only so far)

Question 1

What is the sex-determining chromosome and where is the gene responsible?

Answer 1

Y chromosome determines the male sex, and a gene on the short arm of the y chromosome produces a testis determining factor (TDF). If TDF produced: male.

Question 2

Until what time are the gonads undifferentiated?

Answer 2

6 weeks.

Question 3

What becomes the vas deferens in the male? What happens to this in females?

Answer 3

The wolffian duct plus mesonephros. Regresses in the female.

Question 4

What forms the fallopian tube in the female?

Answer 4

The malarian ligament.

Question 5

What causes regression of female parts in a male?

Answer 5

Testosterone and malarian inhibitory factor

Question 6

What occurs in Turners syndrome?

Answer 6

45XO -> develop female external and internal genitalia but the ovary doesn’t fully develop

Question 7

What occurs in Klinefelters syndrome?

Answer 7

47XXY ->develop male genitalia but the testis doesn’t fully develop.

Question 8

What does increased foetal androgen exposure cause in females?

Answer 8

Female genitalia internally (no MIF) but external genitalia are masculinised.

Question 9

What does decreased foetal androgen exposure cause in males?

Answer 9

Male gonads but external genitalia remain female.

Question 10

What occurs to hormone secretion at puberty?

Answer 10

During childhood, gonadotrophin is low. At puberty pulsatile GnRH begins. This stimulates FSH and LH

Question 11

How is pituitary secretion of sex hormones regulated?

Answer 11

GnRH stimulates gonadotrophs in the anterior pituitary to produce LH and FSH. Increased activity (of what???) is associated with an increase in frequency and amplitude.

Question 12

What are FSH and LH?

Answer 12

Glycoproteins which function via G proteins and adenylate cyclase.

Question 13

What is the effect of FSH in males?

Answer 13

FSH increases spermatogenesis and acts on Sertoli cells and inhibin for negative feedback.

Question 14

What is the effect of FSH on sertoli cells?

Answer 14

FSH stimulates sertoli cells to secrete ABH???. This increases testosterone concentration in the seminiferous tubule.

Question 15

What is the effect of LH in males?

Answer 15

LH stimulates leydig cells to produce testosterone ->negative feedback???

Question 16

What is the effect of FSH in females?

Answer 16

FSH stimulates the developing follicle ->inhibin ->negative feedback??

Question 17

What is the effect of LH in fmales?

Answer 17

With FSH, LH causes an increase in oestradiol (negative feedback ) -> ????

Question 18

At mid cycle, what occurs in females?

Answer 18

Negative feedback becomes positive for a short time, resulting in an ovulatory surge.

Question 19

How is most serum testosterone and DHT found?

Answer 19

90% is protein bound; 60% to GBG, 30% to albumin

Question 20

What may happen to testosterone in fat?

Answer 20

A small amount may be converted to oestradiol

Question 21

How is testosterone metabolised and excreted?

Answer 21

Hepatic metabolism, renal excretion.

Question 22

What is DHT?

Answer 22

Dihydrotestosterone is a more potent form of testosterone and amplifies the effect of testosterone.

Question 23

What are the actions of testosterone and DHT?

Answer 23

Anabolic actions, maturation of the wolffian structures and external genitalia, and DHT stimulates development of secondary sexual characteristics.

Question 24

Define secondary sexual characteristic

Answer 24

Any physical characteristic developing at puberty which distinguishes between the sexes but is not directly involved in reproduction.

Question 25

When is the menstrual cycle timed from?

Answer 25

The first day of bleeding.

Question 26

What is the hormonal status prior to day one of the menstrual cycle?

Answer 26

E2, inhibin and progesterone are providing negative feedback resulting in low levels of FSH and LH

Question 27

What happens after day one of the menstrual cycle?

Answer 27

A new set of follicles develop, with one becoming dominant. FSH and LH levels gradually rise, and with combined action result in E2 rising.

Question 28

What hormonal event causes ovulation?

Answer 28

E2 feedback on LH becomes positive, resulting in an LH surge followed by ovulation.

Question 29

What occurs after ovulation?

Answer 29

Negative feedback and inhibin starts again, and luteolysis begins at about day 24.

Question 30

What is luteolysis?

Answer 30

The structural and functional degradation of the corpus luteum.

Question 31

What are the actions of oestradiol?

Answer 31

Growth and maturation of follicles
Increase amount and excitability of uterine muscle
Endometrial proliferation
Thins and alkalises cervical mucous
Increases proliferation of ductal tissue in the breast
Causes negative feedback on FSH secretion, and both positive and negative feedback on LH

Question 32

How is oestradiol found in the serum? How is it secreted?

Answer 32

90% bound to GBG and albumin. Removed by the liver with some stored in bile.

Question 33

What is progesterone secreted by?

Answer 33

The corpus luteum and placenta

Question 34

How is progesterone found in the serum?

Answer 34

Bound to albumin and CBG??

Question 35

What are the actions of progesterone?

Answer 35

Increases gland growth in the endometrium (with E2 in the luteal phase)
Decreases excitability of the myometrium
Stimulates the lobules and alveoli of the breast and supports secretory function of the breast
Thermogenic

Question 36

At what age does menopause occur? What does it result in?

Answer 36

Between 45-55, results in decrease in sensitivity in the ovary to LH and FSH ->levels increase. E2 and inhibin secretion fall, reducing negative feedback, resulting in a further increase in LH and FSH.

Question 37

Menopause occurs when…

Answer 37

E2 levels are insufficient to induce ovulation.