7. Male physiology Flashcards
What are the main components of the male preproductive tract?
Sperm travels through:
1. Testes
2. Epididymis
3. Seminal vesicles+prostate -> Vas deferens
4. Urethra
5. Penis
TESVUP
What is the function of testes?
Spermatogenesis occurs in tissue of semineferous tubules of testes - testes inside scrotum - outside the body lower temp for spermatogenesis
Explain how spermatogenesis occurs?
Spermatogonium maturation from basal -> apical membrane of semineferous tubules -> released into the lumen - travels to epididymis
What tissue supports spermatogenesis?
Seminiferous tubules inside testes
What tissue supports steroidogenesis in testes?
Interstitium - Leydig cells - produces hormones
What are Sertoli cells and where are they found?
Sertoli cells - somatic cells - support the maturation of sperm cells - spermatogenesis - located in seminiferous tubule epithelium - very large cells - stretch all way from basal to apical membrane of the seminiferous tubule epithelium
What are the functions of Sertoli cells?
Sertoli functions:
- structural: Sertoli are scaffold for germ cells to move basal -> apical in seminiferous tubule epithelium
- protective: Sertoli form blood testis barrier - immunologically privelleged site - immune system can’t attack
- secretory: Sertoli secrete fluid to seminiferous tubule lumen + androgen binding protein to transport androgens
- phagocytic: Sertoli absorb waste organelles of developing germ cells
- stimulatory: between Sertoli - sperm gap junctions allow signalling
- receive and transmit endocrine and paracrine signals: Sertoli have receptors for FSH, testosterone - germ cells don’t - signal to germ cells the needed signal in response to the hormone
SSSEPPP
What defines the number of Sertoli cells?
Sertoli stop dividing at puberty - no increase after - each Sertoli cell supports a fixed number of germ cells - ratio is species dependent
What is the composure of the intestitium?
The interstitium composes:
- blood vessels - seminiferous tubules avascular - molecules travel in blood diffuse into maturing sperm from interstitium
- Leydig cells - steroidogenic
- supporting cells
- fibroblasts - secrete ECM
What is secreted by Leydig cells?
Leydig cells secrete testosterone
What is testosterone required for?
Testosterone required for:
- spermatogenesis: destruction of Leydig cells in the interstitial tissue - no testosterone - gradual degeneration of spermatogenesis -> spermatogenesis restored when testosterone restored
What moves the sperm out of the testes?
Peritubular myoid cells (PTM cells) - contractile - smooth muscle cells - outside of seminiferous tubules -> push sperm out of seminiferous tubule lumen into epididymis
What makes peritubular myoid cells contract?
Peritubular myoid cells (PTM) cells contract after receiving a signal from Sertoli cells - ET-1 - binds to dimer receptor on PTM cells => seminiferous tubules contract and push sperm out into epididymis
How long is epididymis and how it fits into testis?
Epidydimis - 6m long - very coiled to fit inside the scrotum on top of testis
What is the function of epididymis?
Epididymis function:
- sperm concentration - sperm becomes more concetrated - majority of liquid absorbed
- movement
- structural maturation
- sperm storage before ejaculation - also stored in vas deferens
What is an important epididymis environment condition for sperm maturation?
More acidic epididymis pH important for sperm tail development - pH change into more alkaline causes sperm tail malformations - C-ros gene responsible for acidic pH
What epididymis structure helps concentrate the sperm?
Epididymal stereocilia help concentrate the sperm - on the apical epithelial cell surface - stereocilia - increase SA for absorption of testicular fluid
What is required for normal epididymis function?
Androgens (testosterone) required for normal development and function of the epididymis - testosterone KO epididymis shriveled
What is the function of vas deferens?
Vas deferens provides contractile power for ejaculation and stores some of the sperm along epididymis
How is sperm moved through vas deferens?
Vas deferens - straight muscular tube - thick muscular layers contract in peristalsis - move sperm along in ejaculation
What is a surgical contraceptive for males?
Vasectomy - ligation of vas deferens - sperm can’t pass thorugh - sperm phagocytosed - reabsorbed by the system
What is a popular anatomical target for male contraception?
Vas deferens: vasectomy + vasalgel – new method being developed:
- gel injected into vas deferens - forms a block - allows fluids to pass thorugh but not sperm cells - reversible by injection of sodium bicarbonate
What is congenital bilateral absence of vas deferens (CBAVD)?
CBVAD - vas deferentia (pl) don’t develop properly - common in men with cystic fribrosis - CFTR gene mutation - severity of phenotype depends on type and position of CFTR gene mutation
What is the composition of semen?
Semen composition:
- 4% sperm
- 70% nutrients (fructose)
- 25% alkaline solution - for sperm to survive in acidic uterine environment
- 15 lubricant
Semen plasma secreted by prostate + seminal vesicle
What are the two organs producing seminal fluid?
Accessory glands: prostate gland + seminal vesicle - attached to vas deferens - mix with sperm
What are the components of seminal fluid produced by the seminal vesicle?
Seminal vesicle produces ~70-85% of semen plasma - second part of ejaculate - contains fructose + proteins - semenogelin I + II - make semen co-agulate - become more thick
Explain how seminal fluid changes it viscosity
Semen changes its viscosity:
- semen coagulates after ejaculation: PSA+Zinc ions from prostate + semenogelin from seminal vesicles crosslink
- semen liquidifies in female tract: Zinc binds semenogelin - PSA activate - breaks down crosslinking - semen liquidifies - better motility sperm + stays in female tract longer
What are the components of seminal fluid produced by the prostate gland?
Prostatic fluid mixes with sperm - first part of ejaculate - alkaline + contains Zn ions
Explain what is benign prostatic hyperplasia (BPH)?
Benign prostatic hyperplasia (BPH) - non-cancerous enlargement of prostate due to cell multiplication - normally happens at older age
Explain what is prostate specific antigen (PSA)
Prostate specific antigen (PSA) - kallikrein 3 (klk3) - antigen produced by prostate cells - cleaves semenogelin proteins to liquidify semen in female reproductive tract - levels may increase with prostate cancer/BPH - can be used as diagnostic test
What is required for normal prostate function?
Androgens - when no androgens prostate shrivels - lumen decreases
What structure makes the penis erect?
Penis erects when corpus cavemosum enlarges - cavernosal spaces expand
What is the mechanims behind penis erection to deliver sperm into female tract?
cGMP levels relax smooth muscle which makes the penis erect - viagra inihbits cGMP degradation - erect for longer
Lecture summary
