male tract, spermatogenesis and endocrine control (1)

Question 1

testis glands

Answer 1

exocrine glands
- secretory products = spermatozoa

endocrine gland
- secretory product = mainly testosterone

Question 2

gonocytes

Answer 2

primitive germ cells that become spermatogonia

only present in early life - up to minipuberty

Question 3

spermatogonia

Answer 3

germ cells - pre-sperm cells that replicate by mitosis

Question 4

sertoli cells

Answer 4

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

Question 5

leydig cells

Answer 5

interstitial cells

- main product is androgen

Question 6

myoid cells

Answer 6

contractile

Question 7

primordial germ cells

Answer 7

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

Question 8

germ cell tumours

Answer 8

thought to arise from PGCs

93% of germ cell tumours are found in the testis

Question 9

leydig cells production

Answer 9

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

Question 10

when do leydig cells produce the most testosterone

Answer 10

2 months postpartum

2-3ng/ml minipuberty

Question 11

why is mini-puberty important

Answer 11

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

Question 12

role of steroli cells

Answer 12

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

Question 13

steroli cell quantity

Answer 13

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

the number does not increase after puberty

Question 14

importance of blood-testis barrier

Answer 14

created by sertoli cells

important for fertility and prevention of anti-sperm antibody production

Question 15

moving testes

Answer 15

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

Question 16

cryptorchidism

Answer 16

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

Question 17

failure of testes to descend leads to

Answer 17

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

Question 18

changes at puberty

Answer 18

marked increase in proliferation of spermatogonia

cords develop a lumen - become seminiferous tubules

beginning of sperm production

Question 19

spermatogenesis

Answer 19

• 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

Question 20

mitotic division

Answer 20

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

Question 21

where does mitotic division occur and what happens when its complete

Answer 21

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)

Question 22

meiosis

Answer 22

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

Question 23

final process of spermatogenesis

Answer 23

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

Question 24

residual body

Answer 24

unnecessary cytoplasm is shed as the residual body

Question 25

what happens to spermiogenesis in the absence of androgen

Answer 25

is does not occur and spermatogenesis arrests after meiosis the transition from round spermatids to elongated spermatids doesnt happen

Question 26

describe the time of the spermatogenic wave

Answer 26

~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

Question 27

epididymis shape and orientation

Answer 27

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

Question 28

epididymis function

Answer 28

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

Question 29

Vas deferens structure

Answer 29

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

Question 30

Vas deferens function

Answer 30

major site of sperm storage

Question 31

seminal vesicles structure

Answer 31

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

Question 32

seminal vesicles secretion

Answer 32

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

Question 33

prostate gland

Answer 33

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

Question 34

prostate gland zones

Answer 34

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

Question 35

process of erection

Answer 35

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

Question 36

action of viagra

Answer 36

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

Question 37

can viagra be used to treat erectile dysfunction

Answer 37

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

Question 38

contents of semen

Answer 38

prostatic fluid = 30% sperm = 10% seminal vesicle fluid = 60%

Question 39

normal ejaculates

Answer 39

2-5mls in volume contain at least 20 million sperm/ml