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Repro > Spermatogenesis > Flashcards

Spermatogenesis Flashcards

1
Q

function of the testis

A
  • produce and store sperm

- produce hormones with regulate spermatogenesis

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2
Q

overheating of the testes has what effect?

A

reduces sperm count

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3
Q

where are the testes located and why?

A

in the scrotum, outside of the body cavity

-optimum temp for sperm production

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4
Q

what are the testis made up of?

A

90% seminiferous tubules, site of spermatogenesis

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5
Q

where do the seminiferous tubules meet?

A

tightly coiled tubules all meet at the rete testis, then go to epididymus

  • stored in epididymus for a few days
  • upon ejaculation, move through vas deferens
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6
Q

what do sperm start as?

A

spermatogonia

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7
Q

why can men always reproduce throughout their lifetime?

A

mitotic proliferation of spermatogonia means they have a lifetime supply of sperm

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8
Q

where are the spermatogonia located?

A

on the basement membrane

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9
Q

where are Sertoli cells located?

A

they lie along the seminiferous tubules

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10
Q

what are adluminal compartments and what do they do?

A

tight junctions between the sertoli cells

  • protected from the immune system and toxic agents
  • specific enclosed environment for spermatogenesis which is filled with Sertoli cell secretions
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11
Q

movement of sperm in tubules

A

Sperm start to be made on the edge, and as they form they start to move to the lumen. Once they reach they lumen they are fully fledged sperm

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12
Q

what are the spaces between the tubules filled with?

A

blood and lymphatic vessels
Leydig cells
interstitial fluid

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13
Q

Sperm stages during spermatogenesis

A 
Spermatogonia
Primary spermatocytes	
Secondary spermatocytes	
Spermatids
Spermatozoa
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14
Q

Spermatogonia

A

diploid
germ cell on the basement membrane, capable of dividing to produce more spermatogonia, or producing primary spermatocytes

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15
Q

Primary spermatocytes

A

46 XY diploid
move into the adluminal compartment
chromosome replication, production of sister chromatids which exchange DNA (recombination) before meiosis 1

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16
Q

Secondary spermatocytes

A

have undergone meiosis 1

haploid, 23X and 23Y

17
Q

Spermatids

A

meiosis 2
haploid, 4 spermatids
spermatid differentiation from round to elongated
loss of cytoplasm

18
Q

Spermatozoa

A

Mature sperm extruded into the lumen.

19
Q

how often is there a new cycle in spermatogenesis?

A

every 16 days

20
Q

are the sperm cell divisions complete, and what happens as a result of this?

A

no, each cell division from a spermatogonium to a spermatid is incomplete

  • the cells remain connected to one another by cytoplasmic bridges forming a syncytium allowing synchronous development
  • waves of cells at different stages moving down the tubule
21
Q

Oogonia v Spermatogonia

A

oocytes begin meiosis before birth, spermatocytes begin meiosis after puberty
lifetime supply of spermatocytes, limited supply of oocytes

22
Q

Leydig cells

A
  • have LH receptors, convert cholesterol into androgens
  • LH binding stimulus testosterone production contributes to the male sexual characteristics
  • testosterone also binds to the sertoli cell, stimulating spermatogenesis
23
Q

sertoli cells

A
  • FSH receptors, converts androgens to oestrogen
  • FSH binding maintains Sertoli cell health and population
  • Sertoli cell is in control of all the secretions into the adluminal compartment to maintain spermatogenesis
24
Q

action of anabolic steroids

A

interfere with negative feedback, reducing FSH and LH and causing testicular atrophy

25
Q

an erection causes what?

A

vasodilation of corpus cavernosum
-under parasympathetic control
partial constriction of the venous return

26
Q

what does the autonomic nervous system cause?

A

co-ordinated smooth muscle contractions of vas deferens, glands and urethra

27
Q

role of sympathetic nervous system in ejaculation?

A

movement of sperm into epididymis, vas deferens, penile urethra (emission)

28
Q

role of somatic nervous system in ejaculation?

A

expulsion of the glandular secretions

& evacuation of urethra

29
Q

what is the initial portion of the ejaculate?

A

sperm rich

30
Q

what happens to the initial portion of the ejaculate?

A

90% lost before it reaches the ampulla of the uterine tube

31
Q

what is seminal fluid?

A

consists of secretions from:

seminal vesicles, prostate, bulbo-urethral gland combined with epididymal fluid

32
Q

role of Bulbo-Urethral Gland in seminal fluid?

A
  • this gland secretes before ejaculation
  • produces a clear viscous secretion high in salt, known as pre-ejaculate
  • lubricates the urethra for spermatozoa to pass through, reduces risk of sperm being damaged by friction
  • neutralises traces of acidic urine
33
Q

role of seminal vesicles in seminal fluid?

A
  • comprise 50-70% of the ejaculate
  • contains proteins, enzymes, fructose, mucus, vitamin C and prostaglandins
  • high fructose concentrations provide energy source
  • high pH protects against acidic environment in vagina
  • smooth muscle contractions moving the sperm up.
34
Q

role of prostate in seminal fluid?

A
  • secretes milky or white fluid, 30% of the seminal fluid
  • protein content is less than 1% and includes proteolytic enzymes, prostatic acid phosphatase and prostate-specific antigen - involved in liquefaction
  • high zinc concentration, antibacterial
35
Q

structure of the spermatozoa

A

end piece, principal piece and midpiece

  • nucleus has the DNA – most important bit
  • hardly any cytoplasm
  • mitochondrial sheath – needs lots of mitochondria producing ATP for movement
  • 9 pairs of tubules, with a pair in the center – this is the pattern all the way down the tail
36
Q

do fresh sperm fertilise the egg?

A

Fresh sperm will never fertiliise the egg, they need to undergo a process called capacitation which involves changes in the membrane over the head of the sperm, takes between 4-18 hours.

37
Q

what receptor to the sperm bind to on the zona pellucida?

A

zp3

Repro (11 decks)

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