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Reproductive System > Spermatogenesis > Flashcards

Spermatogenesis Flashcards

1
Q

why do the testes sit outside the body?

A

thermoregulation
- spermatogenesis can be dramatically affected by heat
- sit outside body cavity as spermatogenesis needs to occur at a few degrees lower than body temp (~34 degrees)

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2
Q

what are the testes made up of?

A
  • Leydig cells
  • seminiferous tubules
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3
Q

what do leydig cells produce

A
  • produce androgens - testosterone and DHT
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4
Q

what affects androgen production by Leydig cells

A

gonadotrophins - LH and FSH - from anterior pituitary
(GnRH from hypothalamus influence gonadotrophin release from AP)
- involves positive and negative feeback

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5
Q

what are androgens essential for the production of

A

sperm

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6
Q

what are seminferous tubules made up of

A
  • sertolli cells
  • spermatogonia stem cells
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7
Q

what do spermatogonia stem cells produce & what is a quality about them?

A
  • produce sperm
  • they are self-replacing (ie/ a stem cell)
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8
Q

what do sertolli cells do?

A

provide support for spermatogenesis
orchestrate spermatogenesis

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9
Q

[LONG] 3 main phases of spermatogenesis

A
  • mitotic proliferation -> produce large numbers of cells (spermatogonia germ cells [located same as spermatogonia stem cells] -> primary spermatocytes (diploid) and spermatogonia germ cells & spermatogonia stem cells -> spermatogonia stem cells and spermatogonia germ cells)
  • meiotic division I resulting in secondary spermatocytes (haploid) -> halves chromosome number & generates genetic diversity
  • meiotic division II resulting in round haploid spermatids (haploid)
  • spermiogenesis -> turning spermatocytes into sperm ie/ spermatids into spermatozoa
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10
Q

describe structure of seminferous tubules

A
  • spermatogonia at base of seminiferous tubule
  • Sertolli cells extend from bottom through to lumen (fluid filled cavity in centre)
  • various cell types within which are different types of sperm cells that developing
  • once sperm exits into lumen
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11
Q

3 main phases of spermatogenesis

A
  • mitotic proliferation producing large number of cells
  • meiotic division halving chromosomes and generating genetic diversity
  • spermiogenesis turning spermatocyte into sperm
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12
Q

meiotic division halves chromosome number and generates genetic diversity

A
  • primary spermatocytes undergo meiosis I to form 2 secondary spermatocytes (diploid -> haploid)with genetic diversity
  • meiosis II to form spermatids
    NOTE
  • chromosome from 2n to n & recombination
  • 2 haploid spermatids per secondary spermatocyte
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12
Q

mitotic proliferation produces large number of cells

A
  • spermatogonia stem cells are self-replacing (divide into themselves partially)
  • spermatogonia (diploid) also differentiate into primary spermatocytes (diploid)
  • spermatogonia -> type B spermatogonia -> intermediate spermatogonia -> primary spermatocyte
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13
Q

spermiogenesis

A
  • shape of spermatid changes from round to elongated ie/ to spermatozoon - chromatin condenses and cytoplasm removed
  • acrosome forms - containing enzymes for penetrating oocyte/egg membranes at fertilisation
  • tail forms & mid piece forms
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14
Q

what does the mid piece in spermatozoa do?
subsequently, what is importance of tail?

A
  • contains mitochondria -> providing energy necessary for whiplash motion of tail
  • whiplash motion of tail (from structure) allows sperm cell to move efficiently toward egg during fertilisation
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15
Q

what does it mean for spermatogenesis to be continuous spatially

A
  • see sperm at different stages of development simultaneously along seminiferous tubules
  • allowing sperm to be produced continuously
16
Q

what does it mean for spermatogenesis to be continuous temporally

A

production of sperm cells occurs continuously from puberty throughout man’s life
- ongoing generation of sperm cells (not finite number)

17
Q

how long is a spermatogenic cycle

A

between 63-72 days

18
Q

how much sperm being produced everyday?

A

about 300 million sperm

19
Q

where do the spermatozoa go from seminiferous tubules

A
  • exit the testes into epididymus
  • where spend ~6 days undergoing further maturation
20
Q

what is involved in the further maturation of spermatozoa in epididymus

A
  • removal & addition of proteins
  • gain ability to swim progressively
  • gain potential to fertilise
    It is androgen dependent
21
Q

where does final maturation (capacitation) of spermatozoa occur?

A

in female reproductive tract

22
Q

what is semen made up of

A

seminal plasma combine with spermatozoa at ejaculation

23
Q

where is seminal plasma produced

A

in male accessory glands, particularly prostate and seminal vesicles

24
Q

function of seminal plasma
list one negative

A
  • fluid vehicle for sperm
  • buffering (maintain pH env for viability of sperm), antioxidant, metabolic support for sperm
  • contain immune cells
  • ## important for establishment of implantation and pregnancy
  • vehicle of transfer of infection eg/ HIV
25
Q

how long is sperm viable for & how long is egg viable for

A

sperm ~2 days
egg ~1 day

26
Q

characterisations of “normal” and “sub fertile” semen
at least list the characteristics

A

ejaculate values
NORMAL
volume: 2-5mL
sperm conc: 100-700 million sperm
sperm motility: greater than 50% progressive motility
abnormal sperm: greater than 30%
SUBFERTILE
volume: less than 1.5mL
sperm conc: 40 million sperm
sperm motility: less than 32% progressive motility
abnormal sperm: greater than 4%

27
Q

around what age does sperm fertility / male fertility decline?

A

around 40 years of age

28
Q

what is reduced sperm fertility characterised by

A
  • reduced semen volume
  • reduced sperm number
  • increase in sperm abnormalities
    (missing semen progressive motility)
29
Q

what are factors that can negatively influence spermatogenesis temporarily and / or long-term

A
  • infection
  • temperature (hot bath)
  • chemical exposure
  • smoking
  • alcohol
  • obesity
30
Q

how common is infertility (stats)

A
  • 1 in 6 couples infertile globally
31
Q

when is infertile diagnosis made

A

after 12 months of unprotected sex with absence of successful pregnancy (can include fertilisation occurrence but unsustained pregnancy)

32
Q

proportion of which gender infertile

A

1/3 female, 1/3 male, 1/3 both / unknown

33
Q

what is a problem with males and infertility

A
  • males typically do not think / unaware that they’re infertile

Reproductive System (21 decks)

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