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Repro > 1.2 - origin of the gametes - males > Flashcards

1.2 - origin of the gametes - males Flashcards

1
Q

how many gametes does the male system produce?

A

hundreds of million a day

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2
Q

where do germ cells colonise?

A

the seminiferous cords in the medulla of the primordial gonad

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3
Q

what do the seminiferous cords in the medulla of primordial gonad connect with?

A

rete testis, epididymis and vas deferens

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4
Q

what is the speed of post-natal growth of testis

A

slow

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5
Q

when do germ cells begin meiosis

A

AT puberty, NOT before

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6
Q

what happens at puberty to allow germ cells to begin meiosis?

A

hollow seminiferous tubules form from the seminiferous cords

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7
Q

how many tubules does each testis have? where do they empty into?

A

250-750 tubules
empty into the rete testis
into a single convoluted tube - epididymis

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8
Q

where does spermatozoa develop? in association with what?

A

within seminiferous tubules in association with Sertoli cells

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9
Q

what are the tubules separated from the surrounding interstitial tissue by?

A

blood testis barrier

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10
Q

Where is testosterone secreted?

A

Leydig cells in the interstitial tissue

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11
Q

what do the germ cells form?

A

spermatogonia stem cells

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12
Q

How do the spermatogonia stem cells maintain their population? what does this allow for

A

begin mitosis to maintain a population of self-regenerating stem cells that remain avaliable up to and beyond the age of 70
allowing for continuous sperm production at a high rate

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13
Q

what marks the beginning of spermatogenesis in a particular part of the tubule?

A

at intervals, groups of distinct cells: ‘A1 spermatogonia’ emerge

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14
Q

what happens to the A1 spermatogonia?

A

undergo differentiation to produce further A type (stem cells) and type B cells - committed to differentiation to spermatozoa

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15
Q

what happens to each type B sermatogonium?

A

then undergoes a fixed number of mitotic divisions to produce a clone (normally 64) of primary spermatocytes

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16
Q

what are all primary spermatocytes linked together by?

A

cytoplasm bridge

17
Q

how do primary spermatocytes begin meiosis?

A

push their way towards the lumen of the tubule

18
Q

what does the first division of meiosis produce?

A

2 haploid secondary spermatocytes

19
Q

what happens to the 2 haploid secondary spermatocytes?

A

each divides again to form spermatids

20
Q

how many spermatids does each A1 spermatogonium yields up to?

A

256 spermatids

21
Q

what happens to the spermatids?

A

re-modelled to form sperm by spermiogenesis

22
Q

what happens once the spermatozoa are produced?

A

the cytoplasmic bridges break down and the sperm are released into the lumen to be washed down to the rete testis

23
Q

what washes down the sperm to the rete testis?

A

fluid secreted from Sertoli cells

24
Q

how long does spermatogenesis take in a man?

A

70 days

25
Q

how often do new groups of A1 spermatogonia arise?

A

every 16 days (so 4 spermatogenic processes are going simultaneously)

26
Q

how is production continuous?

A

because different sections along the length of a tubule begin the process at different times, so some part is always releasing sperm
(if happened over whole testis at same time, sperm only produced intermittently)

27
Q

what sweeps along the length of tubule?

A

a spermatogenic ‘wave’ of production

28
Q

when does spermatozoa finally mature?

A

during progress through the epididymis

29
Q

what is ‘emission’?

A

during copulation contractions of the vas deferens sweep sperm to be mixed with other components of semen from the seminal vesicles (60% volume) and prostate (20% volume)

30
Q

what is emission controlled by?

A

sympathetic nervous system

31
Q

what is the purpose of emission?

A

to ejaculate semen into the female

32
Q

what is the volume of a typical ejaculation? how many sperms does it contain?

A

3.5ml contains about 350 million sperm

33
Q

how many sperms from ejaculation will reach the site of fertilisation?

A

fewer than 50

34
Q

what is the site of fertilisation?

A

ampulla of uterine tube in the female tract

Repro (78 decks)

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