Spermatogenesis

Question 1

What are the 2 major compartments of the testes?

Answer 1

• seminiferous tubules: contain developing germ cells and sertoli cells
• interstitial cells: contain Leydig cells and blood and lymph vessels

Question 2

What divides the seminiferous tubules from interstitial spaces and its function?

Answer 2

• blood-testes barrier

- prevents immune reaction to spermatozoa and separates fluids of different composition

Question 3

What are the 3 stages of production of mature spermatozoa?

Answer 3

• mitotic proliferation
• meiotic divisions
• cell modelling (spermiogenesis)

Question 4

How long is the spermatogenic cycle?

Answer 4

• 74 days

- occurs in waves every 16 days

Question 5

What happens to the spermatozoa during differentiation?

Answer 5

• cytoplasmic links broken

- released into tubular lumen and sperm is immobile

Question 6

How can sperm move if they are initially immobile?

Answer 6

• sertoli cells secrete fluids that flush the spermatozoa from the seminiferous tubules through rete testis to the epididymis
• epididymis fluid suppresses motility
• sperm moved by peristaltic muscle contraction

Question 7

Describe the process of capacitation

Answer 7

• must occur before the sperm is able to fertilise oocyte
• glycoprotein coating gained in epididymis is stripped
• head acquires capacity to initiate acrosome reaction
• hyperactivation

Question 8

How is infertility in males diagnosed?

Answer 8

Semen analysis:

• determination of sperm
• concentration/total count
• motility
• morphology

Question 9

Define oligozoospermia, teratozoospermia, asthenozoospermia and azoospermia

Answer 9

• oligozoospermia: reduced sperm count (less than 15 million/ml)
• teratozoospermia: reduced percentage of sperm with normal
  morphology
• asthenozoospermia: reduced sperm motility (less than 40%)
• azoospermia: absence of sperm in ejaculate

Question 10

Describe the role of the hypothalamus and pituitary gland in spermatogenesis

Answer 10

• hypothalamus secreted GnRH which binds to gonadotrophic cells on anterior pituitary
• causes release of LH and FSH

Question 11

Describe regulation of gonadotropin secretion

Answer 11

• high GnRH pulse amplitude and frequency preferentially stimulates LH synthesis and secretion
• low GnRH pulse frequency stimulates FSH synthesis and secretion

Question 12

Other than sex hormones what do the anterior and posterior pituitary glands secrette?

Answer 12

Anterior:
- lactotrophs (secrete prolactin)

Posterior:

• neurosecretory hormones:
• arginine
• vasopressin
• oxytocin

Question 13

What is the importance of LH and FSH on spermatogenesis?

Answer 13

• Leydig have receptors for LH
• binding stimulates synthesis and secretion of testosterone
• low testosterone levels halt spermatogenesis
• FSH required for max sperm production
• acts on Sertoli cells

Question 14

What happens when FSH binds to Sertoli cells?

Answer 14

• increases RNA and protein synthesis
• increased energy metabolism
• increased inhibin secretion
• increased cAMP, ABP and fluid secretion
• increased androgen receptors

Question 15

What hormones are synthesised by the testes?

Answer 15

Leydig cells:

• testosterone
• oxytocin
• oestrogen

Sertoli cells:

• oestrogen
• inhibins