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reproduction, development and aging > male tract, spermatogenesis and endocrine control (1) > Flashcards

male tract, spermatogenesis and endocrine control (1) Flashcards

1
Q

testis glands

A

exocrine glands
- secretory products = spermatozoa

endocrine gland
- secretory product = mainly testosterone

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2
Q

gonocytes

A

primitive germ cells that become spermatogonia

only present in early life - up to minipuberty

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3
Q

spermatogonia

A

germ cells - pre-sperm cells that replicate by mitosis

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4
Q

sertoli cells

A

epithelial cells - lumen of tubule help developing pre-sperm cells
- increase in number during minipuberty

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5
Q

leydig cells

A

interstitial cells

- main product is androgen

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6
Q

myoid cells

A

contractile

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7
Q

primordial germ cells

A

will become either sperm or oocytes

first seen around 3-4 weeks post-conception

first found in the yolk sac of the extraembryonic tissues and migrate to the gonadal ridges via the hindgut

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8
Q

germ cell tumours

A

thought to arise from PGCs

93% of germ cell tumours are found in the testis

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9
Q

leydig cells production

A

produce testosterone

adult leydig cells differentiate from stem cells at puberty

initial production by embryonic leydig cells not dependent on stimulation by testosterone 7-8 weeks

approx 14 weeks gestation production of testosterone becomes LH/hCG dependent

Leydig cells secrete testosterone from 8-10 weeks onwards

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10
Q

when do leydig cells produce the most testosterone

A

2 months postpartum

2-3ng/ml minipuberty

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11
Q

why is mini-puberty important

A
  • masculinising the neonatal brain
  • promoting sertoli cell proliferation
  • promoting differentiation of gonocytes into dark AD-spermatogonia
  • may have implication for the timing of orcidoplexy
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12
Q

role of steroli cells

A

nurse cells that promote post mitotis development of sperm precursors

line the inside of the seminiferous tubules (& produce ST fluid)

create the blood testis barrier

nourishing spermatogonia

reabsorb the excess cytoplasm - residual body

maintain the spermatogonial stem cell niche

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13
Q

steroli cell quantity

A

the number of cells is proportional to the sperm production capacity of the seminiferous tubule

the number does not increase after puberty

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14
Q

importance of blood-testis barrier

A

created by sertoli cells

important for fertility and prevention of anti-sperm antibody production

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15
Q

moving testes

A

descent of the testis occurs in 2 phases
1) transabdominal abdominal (10-15 weeks)
2) inguino-scrotal (25-35 weeks)
(androgen is important)

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16
Q

cryptorchidism

A

failure to descend (unilateral or bilateral)

  • maldescent = goes to anterior abdominal wall, perineum or thigh -ectopic
  • most self correct within 3 months
  • can correct surgically - orchidopexy
17
Q

failure of testes to descend leads to

A
  1. infertility - due to excess temperature
    (spermatogenesis requires a lower temperature which is found in the scrotum but not abdomen)
  2. is one of the few known risk factors for testicular cancer
18
Q

changes at puberty

A

marked increase in proliferation of spermatogonia

cords develop a lumen - become seminiferous tubules

beginning of sperm production

19
Q

spermatogenesis

A
  • takes place in the seminiferous tubules of the testes
  • only occurs after puberty
  • huge no. of sperm produced constantly
  • 3 phases
    - mitotic division
    - meiotic division
    - cytodifferentiation
20
Q

mitotic division

A

at puberty the primary germ cells are reactivated
spermatogonial stem cells

stermatogonia divide by mitosis
- 1 daughter cell remains undifferentiated to maintain the stem cell population

  • the other daughter cell continues to divide by mitosis forming spermatogonia. the spermatogonia continue to divide by mitosis
21
Q

where does mitotic division occur and what happens when its complete

A

occurs in the basal compartment of the seminiferous tubules

when the mitotic divisions are complete the spermatogonia move between adjacent sertoli to the adluminal compartment of the seminiferous tubules

(in the adluminal compartment the cells = primary stermatocytes which undergo meiosis)

22
Q

meiosis

A

during meiosis 1 the DNA content doubles
- each of the spermatocytes stoll has 46 chromosomes

at the end of meiosis 1 the cells are called secondary spermatocytes (these have 23 chromosomes each with 2 chromatids)

secondary spermatocytes then divide very rapidly (meiosis 2) to give four spermatids each with 23 chromosomes

23
Q

final process of spermatogenesis

A

spermiogenesis in which the round spermatids differentiate their shape and become spermatozoa (sperm)

24
Q

residual body

A

unnecessary cytoplasm is shed as the residual body

25
Q

what happens to spermiogenesis in the absence of androgen

A

is does not occur and spermatogenesis arrests after meiosis

the transition from round spermatids to elongated spermatids doesnt happen

26
Q

describe the time of the spermatogenic wave

A

~16 days between successive waves of developing spermatozoa
thus at any one point on a tubule, the interval between the release of successive waves of sperm into the lumen is 16 days.

the cycle of the seminiferous epithelium is always the same length of time

27
Q

epididymis shape and orientation

A

comma shaped organ running superior and posterior to the testes

efferent tubules of the rete testis drain into the head of the epididymis

7.5cm long with a single convoluted tubule of about 4-6m in length

28
Q

epididymis function

A

sperm spend 1-14 days passing through the epididymis during which theyre concentrated 100 fold

fluid reabsoprtion is mediated by stereocilia

sperm gain the ability for motility and fertilisation

29
Q

Vas deferens structure

A

45cm long

3 muscular layers surrounding the epithelial lining

- inner longitudinal
- middle circular
- outer longitudinal

at the epididymal end, lumen = simple tube
prior to prostate gland, lumen = enlarged and folded with many crypts (allows additional sperm storage)
- this region is called the ampulla

30
Q

Vas deferens function

A

major site of sperm storage

31
Q

seminal vesicles structure

A

highly folded tubular/pouch-like glands

surrounding the secretory tissue is extensive SM

excretory duct joins VD to become ejaculatory duct

unsusceptible to tumour growth

32
Q

seminal vesicles secretion

A

secrete an alkaline fluid containing fructose which is the major energy source for sperm

semenogelin, a Zn2+ binding protein, is the major protein produced by the seminal vesicles

33
Q

prostate gland

A

doughnut-shaped organ the size of a golf ball

surrounds the prostatic urethra

secretes a milky coloured slightly acidic fluid

secreted the protein = Prostate specific antigen
-PSA breaks down the seminal coagulum

34
Q

prostate gland zones

A

central zone
- surrounds urethra 25% of glands (resistant to carcinoma

peripheral zone
- surrounds the central zone 70% of glands (main site of carcinoma)

transition zone
- 5% of glands surrounds the proximal prostatic urethra (major site of benign hyperplasia)

anterior zone
- fibromuscular tissue no glands

35
Q

process of erection

A
  1. parasympathetic nerve activity induces ACh release
  2. ACh induces NO release by endothelial cells of the corpora
  3. NO induces cGMP production which in turn causes vasodilation
  4. corpora relax and engorge with blood
  5. venous outflow is reduced increasing erection
36
Q

action of viagra

A

used to enhance erection

  1. blocks the action of type V phosphodiesterase
  2. phosphodiesterase breaks down cGMP
  3. inhibiting phosphodiesterase increases levels of cGMP
  4. = vasodilation
37
Q

can viagra be used to treat erectile dysfunction

A

no
not useful if erectile dysfunction occurs because of parasympathetic nerve damage because there is no stimulation of NO and subsequent cGMP production

38
Q

contents of semen

A

prostatic fluid = 30%

sperm = 10%

seminal vesicle fluid = 60%

39
Q

normal ejaculates

A

2-5mls in volume

contain at least 20 million sperm/ml

reproduction, development and aging (27 decks)

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