Theme 3: GUM (Repro/Urinary)

Question 1

In which cells do the spermatazoa develop?

Answer 1

The sertoli cells of the testes, which are closely associated with the semineferous tubules.

Question 2

In the male, which cells produce testosterone?

Answer 2

The leydig (interstitial) cells of the testes.

Question 3

What do the spermatogonia stem cells arise from?

Answer 3

Proliferation of the germ cells which have colonised the sex cords of the primordial gonad.

Question 4

What do the sex cords connect and what do they ultimately become?

Answer 4

Rete testis, epididymis and vas deferens. They become the semineferous tubules during puberty.

Question 5

Which event marks the start of spermatogenesis in the semineferous tubule?

Answer 5

The A1 spermatogonia arising from the spermatogonia stem cells.

Question 6

How often do A1 spermatogonia arise in the tubules?

Answer 6

Approx. every 16 days.

Question 7

What do the A1 spermatogonia differentiate into?

Answer 7

Either into more Type A spermatogonia (stem cells) or into Type B spermatogonia which are then committed to differentiation to sperm.

Question 8

What do the Type B spermatogonia give rise to?

Answer 8

They divide by mitosis; usually 1 Type B spermatogonia will give rise to 64 primary spermatocytes (which are joined by cytoplasmic bridges).

Question 9

What do the primary spermatocytes give rise to?

Answer 9

They divide by meiosis: 1st stage giving rise to two haploid secondary spermatocytes; 2nd stage yields four spermatids.

Question 10

How many spermatids can one A1 spermatogonia give rise to?

Answer 10

256 spermatids.

Question 11

How long does a complete cycle of spermatogenesis take?

Answer 11

~70 days; therefore four cycles occurring at once (because A1 spermatogonia arise every ~16 days). This is referred to as the ‘spermatogenic wave’.

Question 12

What occurs in spermiogenesis?

Answer 12

The cytoplasmic bridges linking the spermatids are broken down before they are released into the tubule lumen and are washed away into the rete testis by fluid secreted from the Sertoli cells.

Question 13

Where does final maturation of spermatozoa take place?

Answer 13

In the epididymis

Question 14

What happens during emission?

Answer 14

The vas deferens contracts sweeping the sperm which is then mixed with fluid from the seminal vesicles (60%) and prostate (20%), This process is dependent on the sympathetic nervous system.

Question 15

In the control of female reproduction, what hormone does the hypothalamus release and what does it stimulate the release of?

Answer 15

GnRH (gonadotrophin releasing hormone) stimulates the release of LH and FSH from the gonadotrophs of the anterior pituitary gland.

Question 16

What cells does LH act on?

Answer 16

Thecal cells which are formed from the stromal cells surrounding the oocyte. Can also bind to outer granulosa cells, resulting in the LH surge (in the pre-ovulatory follicle).

Question 17

What effect does the binding of LH to thecal cells have?

Answer 17

LH binding to the thecal cells results in the production of androgens.

Question 18

What cells does FSH act on?

Answer 18

Only binds to granulosa cells, which are flat follicular cells.

Question 19

What effect does FSH binding to granulosa cells have?

Answer 19

FSH binding to granulosa cells results in the conversion of androgens produced by thecal cells (in response to LH) to oestrogens.

Question 20

What is the LH surge?

Answer 20

During the pre-ovulatory phase (37 hours before ovulation), oestrogens cause LH receptors to appear on granulosa cells. Leads to rapid changes in follicle and within 3 hours the follicle restarts meiosis.

Question 21

During the luteal phase, what effects does LH have?

Answer 21

LH acts on the corpus luteum which in response secretes oestrogen and progesterone.