male tract, spermatogenesis and endocrine control (1) Flashcards Preview

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

Flashcards in male tract, spermatogenesis and endocrine control (1) Deck (39):
1

testis glands

exocrine glands
- secretory products = spermatozoa

endocrine gland
- secretory product = mainly testosterone

2

gonocytes

primitive germ cells that become spermatogonia
(only present in early life - up to minipuberty)

3

spermatogonia

germ cells - pre-sperm cells that replicate by mitosis

4

sertoli cells

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

5

leydig cells

interstitial cells
- main product is androgen

6

myoid cells

contractile

7

primordial germ cells

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

8

germ cell tumours

thought to arise from PGCs

93% of germ cell tumours are found in the testis

9

leydig cells production

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

10

when do leydig cells produce the most testosterone

2 months postpartum

(2-3ng/ml minipuberty)

11

why is mini-puberty important

- masculinising the neonatal brain

- promoting sertoli cell proliferation

- promoting differentiation of gonocytes into dark AD-spermatogonia

- may have implication for the timing of orcidoplexy

12

role of steroli cells

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

13

steroli cell quantity

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

the number does not increase after puberty

14

importance of blood-testis barrier

created by sertoli cells

important for fertility and prevention of anti-sperm antibody production

15

moving testes

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

16

cryptorchidism

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

failure of testes to descend leads to

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

changes at puberty

marked increase in proliferation of spermatogonia

cords develop a lumen - become seminiferous tubules

beginning of sperm production

19

spermatogenesis

- 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

mitotic division

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

where does mitotic division occur and what happens when its complete

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

meiosis

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

final process of spermatogenesis

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

24

residual body

unnecessary cytoplasm is shed as the residual body

25

what happens to spermiogenesis in the absence of androgen

is does not occur and spermatogenesis arrests after meiosis

the transition from round spermatids to elongated spermatids doesnt happen

26

describe the time of the spermatogenic wave

~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

epididymis shape and orientation

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

epididymis function

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

Vas deferens structure

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

Vas deferens function

major site of sperm storage

31

seminal vesicles structure

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

seminal vesicles secretion

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

prostate gland

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

prostate gland zones

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

process of erection

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

action of viagra

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

can viagra be used to treat erectile dysfunction

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

38

contents of semen

prostatic fluid = 30%

sperm = 10%

seminal vesicle fluid = 60%

39

normal ejaculates

2-5mls in volume

contain at least 20 million sperm/ml