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Repro > spermatogenesis > Flashcards

spermatogenesis Flashcards

1
Q

what is the route of sperm when a male ejaculates

A

out of testes
through vans deferens
enters prostatic urethra as the ejaculatory duct
ejaculatory duct is where vas deferens combines with the seminal vesicle outflow

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2
Q

what is the principle hormone regulating spermatogenesis

A

testosterone

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3
Q

where are the testes

A

lue in the scrotum

outside of body cavity

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4
Q

what is the optimum temp for sperm production

A

1.5-2.5 degrees below body temp

overheating testes reduces sperm count

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5
Q

what is the site of spermatogenesis

A

seminiferous tubules of the testes

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6
Q

how is the testes structured

A

made up of lobules
each lobule contains tiny coiled up tubes, these are the seminiferous tubules.
all seminiferous tubules come together in the rete testis. here sperm is concentrated
rete testis leads onto epididymus which is site of sperm storage and then vans deferens. vans deferens will subsequently join urethra.

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7
Q

where is sperm stored

A

epididymus

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8
Q

what happens in the seminiferous tubules

A

sperm develop here between the sertoli cells (SC)

around inner edge of tubule, spertogonium divide by (1) mitosis to increase their # (2) meisos to develop into sperm

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9
Q

what happens to spermatogoia that commit to meiosis

A

develop into sperm.

  • move towards lumen, to in between sertoli cells
  • final mature sperm is released into seminiferous tubule lumen.
  • sperm move up to rete testes, to epididymus for storage until release
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10
Q

where are the leydig cells and what is their function

A

lie just outside the seminiferous tubule and produce testosterone

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11
Q

how are sertoli cells (SC) arranged in the seminiferous tubule

A

SC form tight junctions between themselves - allows for developing sperm to be in confined compartments in the tubule. (adluminal compartment)

  • sertoli cells divide the tubule into: a luminal compartment running through the middle, interstitial space and adluminal space.
  • keeps spermatogonia isolated where they can receive nourishment & secretions from the Sertoli cells.
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12
Q

what is the adluminal copartment

A

inner side of the seminiferous tubule, isolated from blood and lymph
created by tight junctions of sertoli cells

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13
Q

what is the blood testis barrier

A

a physical barrier between the blood vessels and the seminiferous tubules
created by the tight junctions between the SC

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14
Q

why many the blood testis barrier pose a problem during vasectomy

A

the barrier means immune system never sees inside of testis & has never seen the bodies own gametes
in vasectomy, contents of testis may leak into circulation - immune system sees gametes for first time and makes antibodes against own sperm.
Is a problem if reversing the vasectomy bc due to the antibodies

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15
Q

what is oogonia

A

an immature female reproductive cell that gives rise to primary oocytes by mitosis

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16
Q

similarities between oogonia and spermatogenesis

A
  • all oogonia are laid own in female foetus. spermatogonia are also laid down in male foetus
  • oogonia undergo meiosis to make oocyte. spermatogonia undergo meiosis to make spermatocyte
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17
Q

difference between oogonia and spermatogenesis

A

female cannot make more oocyte by mitosis (finite # as was laid down in foetal life)
male can replenish spermatogonia by meiosis (so lifetime supply of gametes)

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18
Q

are spermatogonia haploid or diploid

A

diploid

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19
Q

how do spermatogonia become sperm

A

commit to meiosis (become primary spermatocyte)

  • after meiosis 1, become secondary spematocyte (haploid with identical sister chromatids)
  • after meiosis 2, come spermatids (haploid with 23 chromosomes)
  • undergo morphological change to become spermatozoa (lose cytoplasm and develop flagella)
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20
Q

timeline of Ad (A-dark) spermatogonia

A

always replace themselves

- small # develop into Ap spermatogonia which will then become B spermatogonia

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21
Q

timeline of B-spermatogonia

A

commit to meiosis and become primary spermatocytes.

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22
Q

what are the three basic steps of spermiogenesis

A
  1. Mitotic proliferation of spermatogonia
  2. Meiosis and development of spermatocytes
  3. Spermiogenesis, elongation, loss of cytoplasm and movement of cellular contents
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23
Q

what is spermiogenesis

A

Spermiogenesis is the final stage of spermatogenesis, which sees the maturation of spermatids into mature, motile spermatozoa.

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24
Q

what controls the movement of sperm into the lumen of the sperm

A

controlled by Sertloi cell secretions and factors produced by Sertoli cells are required for the sperm development

25
Q

what is the HPG

A

Hypothalamic – Pituitary – Gonadal Axis

26
Q

HPG for females

A

Hypothalamus releases GnRH

  • > pituitary which releases LH/FSH
  • > ovary which releases Oestrogen/Progesterone
  • > which has -ve feedback on pituitary and hypothalamus
27
Q

HPG for males

A

Hypothalamus releases GnRH

  • > gonadotrophs of ant pituitary which releases LH/FSH
  • > testes which releases Testosterone/Oestrogen/DHT
  • > which has -ve feedback on pituitary and hypothalamus
28
Q

what is the main difference between male and female HPG axis

A

Female HPG is cylic
so oestrogen dominates first half of the cycle; progesterone dominates second half after ovulation.
male = not cyclic. has exactly the same control mechanism that doesn’t change

29
Q

Where does LH from ant pituitary exert its action in males

A

leydig cells of testis.

cause production of testosterone.

30
Q

Where does FSHH from ant pituitary exert its action in males

A

binds to its receptor on SC +maintains pop of SC.

stimulates androgens to be converted to oestrogens by aromatase present in Sertoli cells.

31
Q

what may interefere with the -ve feedback of HPG

A

The anabolic steroids will feedback on the hypothalamus and pituitary and reduce the secretions of FSH/LH.

32
Q

what happens when FSH/LH is reduced in males

A

As FSH maintains the Sertoli cell population reduced FSH leads to testicular atrophy.
males have some aromatase, so when v high androgens, some will be converted to oestrogens. so get growth of breast tissue.

33
Q

what system controls erection and ejaculation

A

ANS.
Parasympathetics control beginning & end (the erection and final evacuation of the urethra)
Sympathetics control movement of sperm into epididymis, vas deferens, penile urethra and expulsion of glandular secretions

34
Q

what is corpus cavenosum

A

one of a pair of sponge-like regions of erectile tissue which contain most of the blood in the penis during an erection

35
Q

mechanism of erection

A

penis has copus cavenosum
- cavernosal arteries dilate and blood rushes in
- simultaneously, under parasymp control - venous return of penis constricts
so net increase bf into corpus cavernosum
constricted venous return and higher blood pressure = erection

36
Q

what is the normal ejaculate volume

A

1.5ml-6ml
approximately 120 million sperm
- initial portion of the ejaculate that is most sperm rich
- may miss first part of the ejaculate when giving semen sample .’, incorrect result.

37
Q

Of sperm in ejaculate, how many reach egg

A

120 sperm in ejaculate

  1. 9% lost before reaching ampulla of uterine tube
    - 120,000 sperm get near to egg
    - only one enters egg
38
Q

what is contained in the seminal fluid

A

Seminal fluid that is ejaculated consists of secretions from

  • The seminal vesicles
  • Prostate
  • Bulbo-urethral gland combined with epididymal fluid
39
Q

what is the bulbo-urethral secretion

A

a clear viscous secretion, high in salt known as pre-ejaculate

40
Q

what is the purpose of bulbo-urethral secretion

A
  • helps lubricate inside of urethra for the spermatozoa to pass through
  • helps neutralise traces of acidic urine (the fluid is alkaline).
    prevents damage to sperm due to friction and acid
41
Q

where are the seminal vesicle secretions added to sperm

A

at ejaculation, sperm released from epididymis and move up vans deferens
at ampulla, seminal vesicles add secretions as it enters ejaculatory duct

42
Q

what percentage of ejaculate is seminal vesicle secretiosn

A

50-70%

43
Q

what do seminal vesicle secretions contain

A

proteins, enzymes, fructose, mucus, vitamin C and prostaglandins

44
Q

what is the significance of fructose in seminal vesicle secretions

A

act as an energy source for sperm. If there is no fructose in a semen sample it indicates a problem with the seminal vesicles.

45
Q

what percentage of seminal fluid is postate secretions

A

30%

46
Q

what is the make up of prostate secretions

A

less than 1%

include proteolytic enzymes, prostatic acid phosphatase and prostate-specific antigen

47
Q

what is the significance of enzymes of prostate secretion in the seminal fluid

A

when semen first ejaculated, is lumpy thick viscous to help deposit sperm around cervix.
- enzymes then cause liquefaction of the semen .’. allowing sperm to swim up the cervical os

48
Q

normal sperm concentration in ejaculate

A

15 million/ml and above, below this is likely to be subfertility

49
Q

when should liquefaction of ejaculate occur

A

in less than 30mins

50
Q

what percentage of sperm should be motile

A

minimum is 40%

51
Q

what is the normal vitality of sperm in ejaculate

A

at least 58% should be alive

52
Q

what should the normal pH of ejaculate be

A

7.2

53
Q

what is the normal leukocyte concentration in seminal fluid

A

: Less than 1million/ml (lots of white cells indicate a urinary tract infection)

54
Q

what is spermatozoon

A

mature motile sperm

55
Q

what does oocyte contain

A

contains all the machinery needed for cell division, the proteins, ribosomes, nutrients, enzymes etc. are in the egg.
All mitochondria is from the mother.

56
Q

what is the purpose of mitochondria of spermatozoon

A

used to power the flagella to propel the sperm forward

57
Q

what is the acrosome

A

structure acting as a bag containing digestive enzyme

58
Q

what is the importance of the acrosome

A

As the sperm approaches the egg, the bag bursts and the enzymes cut through the zona pellucida

59
Q

why can freshly ejaculated sperm not fertilise an egg

A

must undergo 2 processes
1 - capacitation. akes 4-18 hours and involves changing the properties of the acrosome
2 -

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