Concepts of spermatogenesis

Question 1

What are the main parts of the male reproductive system?

Answer 1

testes
duct system
accesory sex glands
penis

Question 2

What are the 2 functions of the testes?

Answer 2

production and transmission of spermatozoa
production of repro hormones (androgens)

(produce androgen and sperm)

Question 3

What is a Sertoli cell and what is its function?

Answer 3

essential for testes formation and spermatogenesis
spermocytes & spermatidis physically anchored to sertoli cell

removes material from elongating spermatid during cytoplasmic condensation

critcal role in mediating actions of hormones on spermatogenesis

Question 4

What are the 3 phases of spermatogenesis?

Answer 4

1. mitotic proliferation
2. meitoic division
3. cytodifferentiation (spermatogenesis)

Question 5

Wha is the structure of a spermatozoa?

Answer 5

head: acrosome (cap) - contains enzymes necessary for fertilisation

Mid-piece: surronded by mitochondrial shealth around 9 dense fibres, within whihc are 9 pairs of microtubules surronding another central pair (all called axoneme)

Tail: mid-piece, principal piece and end piece

Question 6

What are the 8 types of sperm damage?

Answer 6

Crater defect
Tapered heads
Ruffled acrosome
knobbed acrosome
coiled tail
double midpiece
foldede tail
detached head

Question 7

The rate of spermatogenesis is___

Answer 7

constant

Question 8

Explain the spermatogenic cycle?

Answer 8

different sperm initiate division at diff times.

- sperm going through school to graduation (gonia –> cyte –> cyte –> tid)

Question 9

How is spermatogenesis controlled?

Answer 9

GnRH pulses in hypothalumus

FSH and LH

Question 10

Timing or rate of spermatogenesis____ be changed

Answer 10

CANNOT

Question 11

What are the basic principles of spermatogenesis?

Answer 11

sperm cycle + sperm wave = constant sperm production

• under hormone control : Hyp-Pit-Gon
  timing or rate of spermatogenesis cannot be changed

Question 12

The efficiency of spermatogenesis ___ be changed

Answer 12

CAN

Question 13

What governs the rate and efficiency of sperm production>

Answer 13

• length of cycle (constant)
• weight of testes
• sperm production/unit weight of testis
• # of sperm feeding into cycle
• extent of cell loss at each stage

Question 14

Factors effecting efficency of spermatogenesis?

Answer 14

breakdown of blood-testis barrier
irradiation (radiation exposure)
heath and cryorchidism (failure of testes to descend)
diet
drugs/toxic agents
disease
endocrines

Question 15

What is the structure of the epididymas?

Answer 15

Caput (head)
Corpus (middle)
Cauda (tail)
- passage through epididymis takes 6 - 14 days

Question 16

Whaare the different types of penis’?

Answer 16

Shaft - blood reservoirs during errection (Os penis in dog)

Glans penis - tom, alpaca and boar –> corkskrew shape, stiff spine

fibroelastic - boar ram bull -> limited errectile tissue, presence f sigmoid flexure –> in body until errection

musculovascular –> stallion/human - no sigmoid flexure, retractor penis muscle, fills with blood (large corpus cavernosum)

Question 17

What causes errection?

Answer 17

• visual cues(others mating/lordosis)
• olfactory cues(sniffing vulva/ female urination/pheromones)
• tactile stimulation of the penis and perineum (pudendal nerve)
• complex neural signals
  
  • efferent innervation of penis controls errection
  • pelvic nerve promotes errection
  • hypogastric nerve suppresses errection
  • pudendal nerve promotes

parasympathetic neurons fire, release NO from terminals, activates enzyme –> increased blood flow to corpus cavernosa –> intracorporal pressure increases, compressing emissary venules, blood ‘trapped’

relaxation of retractor penis muscle –> straightening of sigmoid flexure

Question 18

What happens in ejaculation?

Answer 18

result of stimulation of glans penis

• causes contraction of muscles surronding vans deferens, seminal vesicles and prostate
  - urethralis
  - ischiocavernous
  - bulbospongiosus
• emmission occurs (movement of SP into urethra)
• spermatozoa and seminal plasma expelled

Question 19

WHat are the 2 stages of ejaculation?

Answer 19

2 stages:
emission and expulsion

Emission:

- sperm movd from epididymus to DD to urethra
- oxytocin, sympathetic controlled coontraction of smooth muscle    - seminal plasma(SP) expelled to urethra    - sperm and SP mix

Expulsion:

- contracting muscles surronding vas deferens and prostate
 - wave like pulsatile
 - distal dilation of c. spongiosum - enlarged glans
  - semen expelled

Question 20

What are the 3 fractions of ejaculation?

Answer 20

early fraction
sperm rich fraction
late fraction (may act as a plug)