Male reproductive system Flashcards
What are the male reproductive organs?
Paired testes
Paired epididymides
Paired ductus deferens
Penis
Accessory sex glands
What does the testes produce?
Sperm and testosterone
Epididymus function
Sperm maturation and storage
Ductus deferens function
Sperm transport @ time of ejaculation
What are the accessory sex organs?
Prostate
Seminal vesicles
Bulbourethral glands
Ampulla
When and where do the tests develop and migrate?
Develop in the abdominal cavity, then migrate to the scrotum:
Before birth- ruminants and pigs
After birth- dogs and horses
Cryptorchidism
Retention of the testes in the abdominal cavity
Infertile because they lack sperm but have libido because they produce testosterone
Counter-current exchange
Between testicular artery and vein (pampiniform plexuses)
Main reason for testicular temp being 3-4 degrees lower than body temp
What factors help in lowering testicular temp?
Sweat glands in the scrotum
Smooth muscle cells of the tunica dartos
Cremaster muscle
What is each testis covered by?
A capsule of tunica vaginalis (peritoneum) and tunica albuginea (dense CT)
What does each testicular lobe have?
2-4 seminiferous tubules
Interstitial tissue that contains BVs and Leydig cells
Seminiferous tubules
30-70 cm long
Long convoluted part
Short straight part @ both ends that open into the rete testis
What is each ST surrounded by?
Peritubular myoid cells, sertoli (somatic), and germ cells
Most numerous to least numerous # of Leydig cells
Pig –> horse –> dog –> bull –> sheep and goat
Stratified seminiferous epithelium cells
Somatic and germ cells containing spermatogonia, primary spermatocytes, secondary spermatocytes, round spermatids and elongated spermatids
When germ cells are released into the lumen, they’re referred to as _________
Spermatozoa
Rete testis
Network of tubules that empty into efferent ductules
Efferent ductules
15-20 in #
Located @ proximal end of tests and empties to the epididymus
Epididymus
Highly convoluted, long tube (80 m in horse)
Caput (head), corpus (body), cauda (tail)
Cauda is continuous with the ductus deferens
Ducutus deferens
Long muscular tube that dilates to form ampulla
Narrows to form ejaculatory duct that empties into the urethra at the colliculus seminalis
What are the 3 stages of spermatogenesis?
- Proliferation
- Maturation
- Metamorphosis
Proliferation
Increase in # of stem cells
Spermatogonia (2n) proliferate and divide mitotically
Maturation
Reduction in # of chromos from diploid (2n) to haploid (n)
What happens to the spermatocytes during the maturation stage?
Primary spermatocytes undergo meiosis 1
Secondary spermatocytes undergoes meiosis 2
Metamorphosis
Change in shape from round cell to elongated cell
Spermatids don’t divide but undergo metamorphosis (acrosome and tail formation)
When does spermatogenesis start?
With puberty and continues until death
Spermatogenesis cycle in the bull?
52 days
Proliferation= 13 day
Maturation= 19 days
Metamorphosis= 20 days
Spermatogenesis for the boar and ram?
Boar: 34 days
Ram 48 days
What are the morphological changes during metamorphosis called?
Spermiogenesis
What happens during spermiogenesis
Nucleus: becomes elongated, chromatin condensed and metabolically inactive
Golgi: form acrosome
Centriole: attaches to distal end of the nucleus and forms tail
Mitochondria: surround mid peice of spermatozoa
What happens to the cytoplasm during spermiogenesis?
Most removed as residual body and phagocytosed by sertoli cell
Remaining remains attached to the neck of sperm as protoplasmic droplet
What is the function of the Sertoli cell?
Support, protection and the nutrition of germ cells
Regulate sperm produced
Release sperm
Phagocytosis
What are the endocrine and exocrine secretions of Sertoli cells?
Exocrine: androgen and testicular fluid
Endocrine: estrogen, anti-mullerian hormone and inhibin
Blood-testis barrier
TJs of the lateral borders of 2 adjacent cells near basal area of epithelium
Divides the seminiferous epithelium into basal and adluminal
What is the function of blood-testis barrier?
Allows the basal compartment to get their nutrients by diffusion from BVs
Basal compartment of seminiferous epithelium
Contain spermatogonia and basal part of Seritoli cells (nucleus and cytoplasm)
Adluminal compartment of the seminiferous epithelium
Contains germ cells, except spermatogonia, and apical pt of Sertoli cells
Where is the aromatase enzyme?
Sertoli cells in males, granulosa cell in females, and fat cells in males and females
What is the role of aromatase enzyme in the sertoli cell?
Converts testosterone into estrogen
Aromatase inhibitors
Used to increase height because estrogen accelerates growth plate fusion
Treats breast cancer in postmenopausal women
Inhibin- FSH loop
FSH stimulates inhibin secretion that downregulates FSH secretion (negative-feedback)
Sertoli cell tumor
More common in cyrptorchid testis
Higher estrogen and inhibin levels and lower FSH level than in controls
5 alpha redutase
Present in the epididymus, accessory glands and external genitalia
Converts testosterone into DHT
DHT
5-10 times more potent than testosterone
Required for the development of accessory sex glands and the external genitalia
5 alpha reductase inhibitors
Reduces DHT level and are used to treat prostate hypertrophy in humans
Leydig cells
Eosinophilic cytoplasm (large amount of SER, lipid, mitochondria)
Secretes testosterone
Ejaculate volume
Pig: 200-250 ml
Horse: 100-150 ml
Dog: 10-15 ml
Bull: 5-7 ml
Sheep and goat: 1 ml or less
What is the function of the leydig cell?
Testosterone –> for spermatogenesis
How is T level within the surrounding ST?
50-100 times higher than the circulation
High level essential for spermatogenesis
Testosterone
Has a negative-feedback on LH
exogenous T implant/ steroids –> low LH –> shrinkage of Leydig cells –> low T level within ST –> loss of germ cells –> atrophy testis
Leydig cell tumor
High T, leading to prostate hypertrophy
Seminal Plug
Formed by sertoli cells
Prevents retrograde transfer of sperm from the rete testis into the ST
Efferent Ductules epithelium
Simple columnar that contains ciliated and non-ciliated cells
What does the non-ciliated cells of the efferent ductules do?
Have apical microvilli and absorb almost 90% of testicular fluid leaving the rete testis or testis
Epididymus epithelium
Lined by pseudostratified columnar epithelium with stereocilia
Surrounded by 1-3 layers and CT
What do columnar cells of the epididymus cells do?
Absorb testicular fluid and secrete glycoproteins
Epididymus tail
Stores sperm until they are ejaculated (continuous sperm discharge in the urine)
Only time the sperm moves
Ductus deferens structure
Pseudostratified columnar with stereocilia
Thick smooth muscle wall arranged in circular, longitudinal and oblique
What are the 2 erectile bodies of the penis
Corpora cavernosa penis (CCP)
Corpus spongiosum (CS)
Have cavernous spaces (venous sinus)
Vascular penis
Numerous cavernous spaces surrounded SM
Increase penis length during erection from engorgement of cavernous spaces with blood
What species have a vascular penis?
Horse and man
Fibrous penis
Few cavernous spaces, dense fibrous CT
Increase penis length during erection mainly results from straightening of the sigmoid flexure
Which species have a fibrous penis?
Ruminants, pig
Which animals have an intermediate penis?
Carnivores (os penis gives additional rigidity)
How is the penis supplied?
Helical (coiled) artery
Smooth muscle cushion under endothelium
Flaccid penis
Smooth muscle cushion has sympathetic tone
Receive little blood (blood directed from arterioles to venules)
Erect Penis
Smooth muscle cushion is relaxed (parasympathetic)
Helical a. dilated, engorged with blood
Molecular mechanism of erection
Parasympathetic system stimulation –> release of NO –> binds with Guanylate Cyclase –> increased levels of cGMP –> relaxation of cavernous smooth muscle cells –> engorgement of venous sinuses with blood –> penis enlargement
Morphology of sperm
Oval: ruminant and man
Sickle: rodents
Hunter: avian
Transport of sperm in excurrent ducts
ST –> rete testis (testicular fluid pressure) –> efferent ductules (testicular fluid) –> head of the epididymus (ciliary movement, smooth muscle cell contraction) –> body of EP –> tail of EP (SM contraction)
Functional changes of sperm
Testicular sperm are immotile and infertile
Acquire abilities by the time they reach the tail of EP
Biochemical changed in the sperm
Sperm during their transit in EP (10-12 days) acquire on their surface epididymal glycoproteins which enable them to acquire motility and fertilizing abilities
Capacitation
Sperm loose proteins in the female tract