male reproductive biology

Question 1

the bipotential gonad

Answer 1

has both wolffian and mullerian ducts

for males,
wolffian ducts differentiate epididymis, vas deferents
mullerian ducts regress (apoptosis)

for females ,
muller an ducts differentiate to oviducts, Fallopian tubes, uterus, cervix and upper vagina
wolffian ducts regress (apoptosis)

Question 2

SRY controls

Answer 2

early testis differentiation
sertoli and leydig cells
sertoli cells secrete AMH - causes female reproductive structures to regress
leading cells secrete testosterone which induces differentiation of the wolffian duct system (epididymis, vas deference, sex accessory glands)

Question 3

no-SRY gene

Answer 3

7-8 weeks - primitive gonad cortex develops not ovary (medullar regresses)
embryonic ovary does not secrete hormones

Question 4

puberty is regulated by

Answer 4

HPG axis
adrenal cortex also secondarily involved

brain stimulates the hypothalamus to increase production of GnRH which stimulates anterior pituitary to increase LH and FSH to trigger gonads to produce sex hormones
ovaries produce oestrogen (oestradiol) and testes produce testosterone
FSH and LH also stimulate the development go oocytes and spermatozoa

Question 5

hypothalamus in puberty

Answer 5

hypothalamus generates pulses of GnRH around 12th year of life

Question 6

pulses of GnRH dependant on

Answer 6

pulses typically occur at night, due in part to gradual decrease in nocturnal melatonin secretion from pineal gland
also influences by nutritional status of body and growth rate
GH an IGF-1 stimulate reproductive function
leptin/ghrelin - metabolic hormones that determine size of fat stores

Question 7

kisspeptin

Answer 7

patients with Kiss1 or KissR null mutations have hypogonadotrophic hypogonadism (HH) - pathological impubertism + infertility of CNS origin
a rise in the pulsatile release of kisspeptin in the median eminence takes place at puberty
exogenous administration of kisspeptins advances the onset of puberty and activates the pulsatile release of GnRH

Question 8

testosterone is secreted by

Answer 8

leydig cells in response to LH

Question 9

dehydrotestosterone

Answer 9

made from testosterone by 5a-reductase in some target cells
binds receptor stringer than testosterone
amplifies action of testosterone in some target tissues

Question 10

systemic testosterone inhibits

Answer 10

GnRH and LH secretion

Question 11

blood testes barrier

Answer 11

sertoli barrier

keeps testosterone in testes to prevent diffusion into blood and negative feedback

Question 12

Sertoli cells secrete ABP

Answer 12

androgen binding protein

binds testosterone and keeps it at local high testosterone

Question 13

testes

Answer 13

formed near kidneys - descend to scrotum

guided by gubernaculum through inguinal canal

Question 14

undescended testes

Answer 14

crytorchidism - infertility

Question 15

scrotum

Answer 15

sweat glands, pampiniform plexus, cremaster and darts muscles (increases in temperature causes cremaster and dartos to relax and the testes drop)

Question 16

pampiniform plexus

Answer 16

warm blood comes down and looses heat to testicular blood rising back up

Question 17

spermatogenesis

Answer 17

occurs in seminiferous tubules

Question 18

epididymis

Answer 18

coiled tube which enlarges into vas deferens

Question 19

vas deferens enters

Answer 19

prostate gland
content pass into ejaculatory duct and into the internal urethra
and urethra carries sperm away

Question 20

germ cells in seminiferous tubules

Answer 20

spermatogenia

mature, proliferate and differentiate into spermatozoa

Question 21

Sertoli cells

Answer 21

nourish and provide support for developing spermatozoa by providing local hormones, lipids and glycogen
create blood testis barrier

Question 22

myofibroblasts

Answer 22

contractile
when sperm are in the seminiferous tubules they can’t move yet - must be mechanically moves out before they acquire motility

Question 23

spermatogenesis

Answer 23

primordial germ cells migrate and become spermatogonia

Question 24

spermatogonia

Answer 24

at puberty, spermatogonia mature, proliferate and differentiate into 1° spermatocyte
meiosis 1 into 2 x 2° spermatocytes
meiosis 2 into 4 x spermatids
differentiate into mature spermatozoa

Question 25

1 spermatogonium

Answer 25

can make 512 sperm

Question 26

spermatozoa

Answer 26

contain haploid genome acrosome - large quantities of hyaluronidase and proteolytic enzymes to facilitate ovum penetration minimal cytoplasm tails - mitochondria-packed so lots of power motile microtubules flagellate

Question 27

epididymal sperm maturation

Answer 27

testicular spermatozoa are incapable of fertilising eggs (unless injected) maturation achieved at distal corpus or cauda acquire progressive motility biochemical changes - increasing capacity for glycolysis, increase phospholipid FA content, activate CatSper (Ca trigger for acrosome reaction)

Question 28

seminal vesicles

Answer 28

``` paired glands 65% of seminal fluid alkaline prostaglandins, fibrinogen and fructose semenogelin (prevents early sperm capacitance, limits motility) ```

Question 29

semenogelin

Answer 29

gel slowing down the sperm so they can acquire motility without moving away

Question 30

prostate

Answer 30

30% of seminal fluid liquefying enzymes, fibrinolysis PSA - serine protease - hydrolyses semenogelin (sperm motility inhibitor)

Question 31

PSA

Answer 31

enzyme that gets rid of semenogelin

Question 32

bulbourethral glands

Answer 32

``` paired glands 5% seminal fluid alkaline pre ejaculatory fluid make movement of ssperm easier ```

Question 33

vasodilation in erection

Answer 33

increased arterial blood flow to corpora cavernosa | turgor compresses veins to limit loss of blood creating erection

Question 34

corpus spongiosum

Answer 34

remains pliable in erection - prevents urethral occlusion

Question 35

erection is controlled by

Answer 35

integrating centres (lumbar) activated by descending path (aroounsal) and afferents from genitalia parasympathetic nerves in penis release - ACh + VIP (co-transmitters) create vasodilation - NANC fibres release nitric oxide for vasodilation

Question 36

erection is sympathetic or parasympathetic

Answer 36

parasympathetic

Question 37

emission

Answer 37

movement of semen through the urethra vas deferens smooth muscle contraction move sperm forward prostate, seminal vesicle smooth muscle contraction move prostatic and seminal fluid forward mix in internal urethra (+ bulbourethral secretions)

Question 38

ejaculation

Answer 38

propulsion, expulsion | rhythmical contraction of bulbospongiosus (skeletal muscle)

Question 39

way finding of sperm

Answer 39

use chemotaxis (using sensing progesterone receptors) and thermotaxis (seek warmer environment)

Question 40

capacitation of sperm

Answer 40

PSA degrades semenogelin increase in motility, alkaline uterine/fallopian fluid alters membrane (increase in calcium permeability and CatSpur channels)

Question 41

acrosome reaction

Answer 41

hyaluronidase and proteolytic enzymes digest proteins in ovum ECM sperm reaches zona pellucida sperm membrane binds receptor proteins, entire acrosome rapidly dissolves and releases enzymes open penetrating pathway for the sperm to enter the ovum sperm head and oocyte membranes fuse (cortical reaction) and deliver sperm genome

Question 42

sperm membrane binds

Answer 42

ZP3 proteins

Question 43

why does only 1 sperm enter the oocyte

Answer 43

sperm entry causes Ca2+ release which triggers cortical reaction

Question 44

cortical reaction

Answer 44

cortical granules exocytosed into the periviteline space

Question 45

cortical granules contain

Answer 45

proteases - that severe ZP3 receptors - any other bound sperms fall off and new sperm can't bind hyalin - forms a layer hardening the vitelline membrane making it impenetrable hygroscopic mucopolysaccharides (GAGs) expand the vitelline space