Lecture 8 - The Gonads 1

Question 1

How do the gonads develop in males and females?

Answer 1

Males - testes Females - ovaries

Question 2

What differentiates the ovaries from testes in embryogenesis?

Answer 2

The SRY gene on Y chromosome makes gonad develop into testes

Question 3

When does spermatogenesis begin?

Answer 3

In puberty

Question 4

When does oogenesis begin?

Answer 4

Reach 6-7 million oogonia at 24 weeks and cells begin deteriorating (atresia) and when puberty is reached 400,000 and by the time menopause is reached, 300-400

Question 5

What are the functions of the gonads?

Answer 5

Production of gametes - gametogenesis Steroidogenesis - Androgens (MALES, females) and Oestrogens/Progesterones (FEMALES males)

Question 6

Describe the process of Spermatogenesis:

Answer 6

Germ cell (diploid) > spermatogonia (mitotic, ^ testosterone) > 1ry spermatocytes (1st meiotic) > 2ry spermatocytes (2nd meiotic/HAPLOID) > Spermatids > Spermatozoa

Question 7

How long does spermatogenesis take?

Answer 7

Around 70 days

Question 8

How do males retain some spermatogenic capability throughout life?

Answer 8

A pool of spermatogonia remain for subsequent cycles

Question 9

At what rate is sperm produced?

Answer 9

300-600 sperm/gm in testis/second

Question 10

Describe the process of oogenesis:

Answer 10

Germ cell (diploid) > Oogonia (mitotic) > 1ry oocyte (1st meiotic) > 2ry oocyte (HAPLOID, 2ry meiotic and takes both cytoplasms, so 1st polar body dies - occurs during ovulation) > Ovum (with 2nd polar body)

Question 11

What happens to primordial follicles?

Answer 11

They are arrested in development and enter atresia - cell degradation then death

Question 12

Key features of testes:

Answer 12

Coiled seminiferous tubules - spermatogenesis Rete testis, Vasa efferentia Epididymis - stores sperm and sperm gain motility Vas deferens - surrounded by smooth muscle, propels sperm to urethra and other secretions added

Question 13

Key features of seminiferous tubules:

Answer 13

Leydig cells - close to ST Sertoli cells - Sperm develop in folds of sertoli cells, where they then move into tubule lumen - connected very tightly leading to blood-testes barrier

Question 14

What are Sertoli cells?

Answer 14

Form seminiferous tubules Synthesise FSH and androgen receptors (ABG) In response to FSH - INHIBIN produced Associated with developing spermatocytes

Question 15

What are Leydig cells?

Answer 15

Lie outside ST Synthesise LH receptors In response to LH are the main source of testicular androgens - testosterone (testosterone in testicles is 1000x higher than in blood)

Question 16

Key features of ovaries:

Answer 16

GRAFFIAN FOLLICLE: Ovum, Follicular fluid, Granulosa cells, Thecal cells

Ovarian stroma

Follicles undergoing atresia

Remnants of last corpus luteum

Question 17

What is the precursor molecules to steroids?

Answer 17

Cholesterol

Question 18

How do we differentiate between which steroid produced?

Answer 18

Different enzymes present in each target tissue

Question 19

How is Dihydrotestosterone formed?

Answer 19

Chol > preg > prog > 17 OH prog > androstenedione > testosterone > DHT

Question 20

How is 17 beta oestradiol formed?

Answer 20

Chol > preg > prog > 17 OH prog > androstenedione > EITHER a) testosterone > oestrone > 17BO OR b) Oestrone > 17BO

Question 21

How long does the menstrual cycle last?

Answer 21

Between 20-35 days, usually 28

Question 22

When does MC begin?

Answer 22

On first day of menstruation

Question 23

What is menstruation?

Answer 23

Loss of blood and cellular debris from necrotic uterine epithelium

Question 24

When does ovulation occur?

Answer 24

Around day 14

Question 25

What does the menstrual cycle consist of?

Answer 25

Ovarian cycle and Endometrial cycle

Question 26

What is the process of the menstrual cycle?

Answer 26

Follicular phase (OC) \> 17BO \> Proliferative phase (EC) (thickening of endometrium) & Ovulation (OC) \> Luteal phase (OC) \> Prog (stimulates secreation of hormones) and 17BO \> Secretory phase (EC)

Question 27

When does 17BO secretion begin?

Answer 27

When follicles increase in growth and when dominant follicle secretes ^ oestrogen levels - maintaining it for 36 hrs where -ve feedback turns to +ve feedback, surging LH and FSH causing ovulation

Question 28

What is the ovarian cycle?

Answer 28

Pre-antral follicle \> Early antral follicle \> late antral follicle \> Graffian follicle \> OVULATION + LUTEAL PHASE (release of ovum and corpus luteum)

Question 29

How is the ovum chosen?

Answer 29

They're selected sporadically for development and the most highly developed can then survive on its own, so the others undergo atresia

Question 30

What hormones are produced during the ovarian cycle by the follicle?

Answer 30

The late antral follicle produces 17BO in granulosa cells from androgens (contain aromatase) FSH and LH are secreted to the follicle Thecal cells have LH receptors and synthesise androgens from LH, which then diffuse to granulosa cells

Question 31

What hormones are produced during ovarian cycle by the corpus luteum?

Answer 31

Androgens converted into 17BO and progesterone under LH and FSH influence

Question 32

What is the dominant hormone in the proliferative phase?

Answer 32

Oestrogen

Question 33

What happens to the endometrium during the early and late phase of the proliferative phase?

Answer 33

Early: thin Late: thickens - mitosis

Question 34

What happens to the glands during early and late phases of proliferative phase?

Answer 34

Early: Straight Late: Enlarge, coil, increased blood supply to endomentrium

Question 35

What happens to endometrium and glands during secretory phase?

Answer 35

Endom: becomes secretory Glands: secrete glycogen, mucopolysaccharides; mucosa engorged with blood

Question 36

What is the dominant hormone in the secretory phase?

Answer 36

Progesterone (small oestrogen influence)

Question 37

What days correspond to each part of the cycle?

Answer 37

1-5 = Menstruation 6-14 = Proliferative phase 14-15 = Ovulation 15-28 = Secretory phase