Spermatogenesis

Question 1

what’s composed in peritubular compartment

Answer 1

leydig cells

vasculature

Question 2

what do leydig do

Answer 2

secrete testosterone

Question 3

2 compartments of testes

how do we keep them separate?

Answer 3

1. seminiferous tubules: developing germ cells. sertoli cells
2. interstitial spaces:
   leydig cells
   blood and lymph

separated by blood-testis barrier

Question 4

2 functions of blood-testis barrier

Answer 4

• prevents immune reaction to spermatozoe (as immune system develops before sperm)
• separates fluids of different composition - creates gradients

Question 5

where is the blood-testis barrier

Answer 5

between seminiferous tubules and interstitial spaces - between neighbouring sertoli cells

zonular junctions and filament bundles

Question 6

can a primary spermatocyte get through BTB?

Answer 6

yes

Question 7

3 stages of spermatogenesis

Answer 7

primordial germ cell –> spermatozoa

1. mitotic proliferation
   (spermatogonia undergoes self-renewal mitotic division to replenish stem cell pool)
2. meiotic divisions
   (primary spermatocyte enters meiosis 1. 46 chromosomes. DNA copy number 4C.–> secondary which has 23 chromosomes 2C. ) Further meiosis 2 –> 2 haploid chromosomes. (23 and 1C).
3. spermiogenesis (cell modelling)
   spermatocyte -> spermatid –> head (acrosome and nucleus), middle piece, principal piece, end piece (9+2 microtubular arrangement)

Question 8

from 1 spermatogonia you get

Answer 8

4 spermatozoa

Question 9

what is spermiation

Answer 9

occurs at end of differentation:

• cytoplasmic links broken
• spermatozoa released into tubule lumen
• sperm virtually immobile

Question 10

what does the sertoli cell do after spermiation

Answer 10

secretes fluid to flush from seminiferous tubules through rete testis to epididymis.

Question 11

epididymal fluid

Answer 11

protects sperm 
perevents motility (aided instead by peristaltic contractions)

Question 12

what process needs to occur (to sperm) for fertilisation to occur

Answer 12

CAPACITATION
normally occurs in female repro tract. glycoprotein coat is stripped.

• -> head acquires capacity to initiate acrosome reaction
• -> hyperactivation (increased flagellar beats)

Question 13

normal 
semen volume 
pH
sperm conc
total sperm count 
total sperm motility (%)
sperm morphology (% normal)

Answer 13

>1.5ml
>7.2
>15 million 
>39 million sperm/ejaculate 
40% motility 
>4% normal sperm

Question 14

GnRH 
from where 
in what way 
stimulates what 
eg.

Answer 14

from hypothalamus
in pulsatile secretions
anterior pituitary gonadotrophs: LH and FSH control testicular functions

Question 15

Rs for leydig

Answer 15

leydig cells have Rs. stimulates synthesis and secretion of testosterone.

Question 16

What does FSH do?

Answer 16

required for max sperm reduction.

it acts on sertoli cells

Question 17

how do we get oestrogen from testosterone

Answer 17

it is aromatised

Question 18

effects of oestrogen on testes

Answer 18

produce hormone called inhibin.

if LOTS of testosterone: inhibin is produced (-> piuitary and decreases amount of FSH)

Question 19

if low inhibin, what about levels of gonadotropin

Answer 19

high LH and FSH

Question 20

functions of FSH on sertoli cells

Answer 20

increased RNA and protein synthesis 
increased energy metabolism 
increased cyclic AMP 
increased androgen receptors 
increased FSH receptors

increased fluid secretion
increased ABP secretion
increased inhibin secretion

Question 21

what hormones do the testes synthesise?

Answer 21

1. testosterone (steroid) by leydig cells
2. oestrogens (steroid) by sertoli and leydig cells
3. inhibins (peptide) by sertoli cells
4. oxytocin (peptide) by leydig cells

Question 22

when is testosterone blocked

Answer 22

when primary spermatocytes enter meiotic prophase

Question 23

causal diagnosis of male infertility
10% is
14% is
4% is

Answer 23

28% infertile men are given causal diagnosis
10% previous gonadotoxic chemo or radiotherapy for treatment of malignant disease
14% testosterone abuse or other chronic disease (diabetes)
4% genetic disorders (Kleinefelter’s, microdeletions on Y)