male reproductive system Flashcards
the male reproductive system produces what cells
sperm cells
which can be transferred to female
in what way is the male reproductive system different to females
anatomically
as Some hormones are same, but act in very different ways
what is the scrotum and what compartments is it divided into
Pouch containing testes
- L lower than R to avoid compression between thighs
Divided into R & L compartments
- by internal median septum
- Externally marked by seam
(perineal raphe)
what temp is required for sperm production
<37oC
name the 3 mechanisms for regulating testes temperature
cremaster muscle
dartos muscle
pampiniform complex
how does the cremaster muscle regulate testes temp
strips of internal abdominal oblique muscle, contracts when cold to draw testes nearer body
how does the dartos muscle regulate testes temp
subcutaneous layer of smooth muscle, contracts when cold, so taut & wrinkled
how does the pampiniform complex regulate testes temp
extensive vein network, cools blood [by 2oC] & testis [so sperm formed] by acting as a ‘countercurrent heat exchanger’.
explain the Countercurrent Heat Exchanger
blood flowing towards testis is leaving body at body temperature (37oC) but since the vessels (arteries) are close to the cooler blood from the testis entering the body, heat is lost (exchanged) and so blood enters the testis at the cooler temperature of 35oC, required for sperm production.
The cooler blood coming from the testis then gains heat from nearby vessels containing blood flowing in the opposite direction, so enters the body at a warmer temperature.
explain testes shape
Each testis is oval (4x2.5cm)
what glands do testes have
Both exocrine (sperm) & endocrine (testosterone ) glands
whats the outer cover of the testes called
tunica vaginalis
whats the White fibrous capsule of the testes called
tunica albuginea
what doe the Connective tissue septa divide testes organ into
300 cone/wedge-shaped lobules
each testes lobule conatins how many seminiferous tubules
1-3
what are seminiferous tubules
slender ducts [70cm long] where sperm produced
what between the Between sem.tub. (seminiferous tubules) in testes
clusters of interstitial cells [cells of Leydig], producing testosterone
what are sem.tub. (seminiferous tubules) lined by
several layers of germ cells (in process of becoming sperm) & fewer tall sustentacular [Sertoli] cells
- provide nutrients, waste removal, growth factors; secrete inhibin –> which regulate rate of sperm production
Spermatogenesis occurs where
in the seminiferous tubules
how does spermatogenesis start and what happens
it starts at the outer edge of the tubule (at the top of the diagram) and sperm matures towards the lumen of the tubule (at the base of the diagram), to become a spermatozoon.
what forms the blood-testies barrier (BTB)
Tight junctions between adjacent Sertoli cells
what does the blood testes barrier prevent and whys this important
proteins & other large molecules from getting to germ cells, i.e., prevent attack from immune system
- Important because germ cells are genetically different from other cells of body
what occurs when Blood testes barrier fails to form adequately in adolescence
sterility
- immune system produces autoantibodies against the germ cells.
name the components of the Germinal epithelium of testis
1.Basal lamina
2.Spermatogonia
3.Spermatocyte 1st order
4.Spermatocyte 2nd order
5.Spermatid
6.Mature spermatid
7.Sertoli cell
8.tight junction (BTB)
1 starts at bottom of layer, cells 2 -6 go all the way up to 6 which is top of layer
8 is where the 2 sertoli cells(7) join, which is just above cell 2
number 7 are the big cells which the rest surround
what are the Rete Testis (pronounced reetee)
Seminiferous tubules [combined length ~1/2 mile] lead into a network called the rete testis
(250 to 300 metres of seminiferous tubule per testis)
Where sperm partially mature
Sperm is moved along by what
by flow of fluid secreted by sustentacular cells & possibly by cilia on some rete cells
Sperm do NOT swim while in the male reproductive tract!!!!!
Testes begin development where
near kidney
explain the process of testes development (descend)
In foetus, testis goes through a passageway
- inguinal canal [weak spot inguinal hernia]
As testes descend
- accompanied by ever-elongating testicular arteries, veins, lymphatic vessels, nerves, sperm ducts & extensions of internal abdominal oblique muscle
how many boys in uk are born with undescended testicles and why and what can be done
5%
infertility as testes too warm for spermatogenesis
correct with hormone injections or surgery
where does sperm go after leaving testis
sperm travel through series of 4 ducts to reach outside
name the 4 ducts that sperm travel through when leave testes
12 Efferent Ductules
Epididymis
Vas Deferens (ductus deferens)
Ejaculatory Duct
explain the process and ducts used for sperm to travel through to exit the testes
Rete of Testis
then to:
12 Efferent Ductules:
- with clusters of ciliated cells to help drive sperm along
then to:
Epididymis
- Comma-shaped [head, body, tail] with 6m coiled duct where sperm matures
then to:
Vas Deferens (ductus deferens)
- Up through inguinal canal, down behind bladder, widens into ampulla, unites with duct of seminal vesicle
then to:
Ejaculatory Duct
- Where vas deferens & duct of seminal vesicle meet
what happens in the epididymis spermatic duct
Sperm matures over 20 days
Stored sperm fertile for ~50 days
Duct reabsorbs 90% fluid secreted by testis
what happens in the Vas Deferens spermatic duct
SMCs (smooth muscle cell) produce peristaltic contractions during ejaculation
- drive sperm from epididymis to ejaculatory duct
name the 3 sets of accessory gland
Seminal Vesicles (pair of)
Prostate Gland
Bulbourethral (Cowper) Glands
explain the accessory glands Seminal Vesicles
theyre a pair
Posterior to urinary bladder
1 associated with each vas deferens
Size of little finger, complex labyrinth
Secretion ~60% of semen
explain the Prostate accessory Gland
Surrounds urethra & ejaculatory duct
Walnut-sized
Aggregate of ~50 glands
Empty thro’ ~20 pores in urethral wall
Thin, milky secretion ~30% semen
explain the Bulbourethral (Cowper) accessory Glands
Pair brownish, spherical 1cm diameter
Inner (near body) end of penis
Ducts lead into penile urethra
During sexual arousal produce clear, slippery fluid, lubricates head of penis & neutralises acidity of residual volume
what 2 systems share the male urethra
urinary & reproductive systems
how long is the male urethra
20cm
explain the shape of the male urethra
S-shaped
- down from bladder, anterior at root of penis, down into penis
what are the 3 regions of the male urethra
Prostatic
- near bladder
Membraneous
- passes through muscular floor of pelvic cavity
Penile
what does the penis do in terms of for reproduction
Deposits semen in vagina
explain the structure of the penis
3 columns of erectile tissue (fill with blood to enlarge & engorge):
- 2 corpus cavernosa
- 1 corpus spongiosum (forms cap = glans)
Loose fold of skin
- foreskin,covers glans
Root of penis
- bulb (from corpus spongiosum)
- crus (from corpus cavernosa)
what is semen and how much is produced
seminal fluid
2-5ml per ejaculation
what does semen compose of
60% seminal vesicle fluid
30% prostatic fluid
10% sperm & spermatic duct secretions
trace bulbourethral fluid
what should sperm count be and what is it if someones infertile
Sperm count = 50-120 million sperm/ml
Infertility if <15 million/ml
explain the structure of the mature spermatozoan
head:
- acrosome
- nucleus
-neck
tail:
- mitochondria
- middle piece
- principal piece
- end piece
explain the composition of semen
Spermatozoa
- digest path through cervical mucus, fertilise egg
Fructose
- energy for sperm motility
Fibrinogen
- causes semen to clot
- clotting enzymes -> converts fibrinogen to fibrin after ejaculation, so semen clot & adhere to vagina/cervix
Fibrinolysin
- liquefies semen after 15 min ejaculation to liberate sperm
Prostaglandins
- reduce viscosity of cervical mucus
Spermine
- neutralise vaginal acidity
what happens in a vasectomy
1cm segment of ductus deferens removed
Spermatozoa cannot pass
- Scar tissue forms permanent seal
Ejaculation seems ‘normal’ to the male
- Secretions of epididymis & testes semen volume only 5% total
Spermatozoa continue to develop but remain within epididymis until they degenerate
explain ejaculation once having a vasectomy
still ejaculate but semen contains no sperm
sperm and hormones can still be produced but not ejaculated as vas defences cut
inhibin is secreted by what cells
Sertoli cells
what does inhibin do
reduce FSH secretion & sperm production without reducing LH & testosterone secretion
what happens when inhibin secretion when sperm count drops
When sperm count drops
<20 million sperm /ml,
inhibin secretion drops &
FSH secretion rises to stimulate sperm production
what happens to males at puberty
Hypothalamus becomes less sensitive to inhibitory effect of androgens
Rate of GnRH secretion increases
Increased FSH
- sperm cells formed)
LH release
- interstitial Leydig cells secrete more testosterone
