7. Male physiology

Question 1

What are the main components of the male preproductive tract?

Answer 1

Sperm travels through:
1. Testes
2. Epididymis
3. Seminal vesicles+prostate -> Vas deferens
4. Urethra
5. Penis

TESVUP

Question 2

What is the function of testes?

Answer 2

Spermatogenesis occurs in tissue of semineferous tubules of testes - testes inside scrotum - outside the body lower temp for spermatogenesis

Question 3

Explain how spermatogenesis occurs?

Answer 3

Spermatogonium maturation from basal -> apical membrane of semineferous tubules -> released into the lumen - travels to epididymis

Question 4

What tissue supports spermatogenesis?

Answer 4

Seminiferous tubules inside testes

Question 5

What tissue supports steroidogenesis in testes?

Answer 5

Interstitium - Leydig cells - produces hormones

Question 6

What are Sertoli cells and where are they found?

Answer 6

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

Question 7

What are the functions of Sertoli cells?

Answer 7

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

Question 8

What defines the number of Sertoli cells?

Answer 8

Sertoli stop dividing at puberty - no increase after - each Sertoli cell supports a fixed number of germ cells - ratio is species dependent

Question 9

What is the composure of the intestitium?

Answer 9

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

Question 10

What is secreted by Leydig cells?

Answer 10

Leydig cells secrete testosterone

Question 11

What is testosterone required for?

Answer 11

Testosterone required for:
- spermatogenesis: destruction of Leydig cells in the interstitial tissue - no testosterone - gradual degeneration of spermatogenesis -> spermatogenesis restored when testosterone restored

Question 12

What moves the sperm out of the testes?

Answer 12

Peritubular myoid cells (PTM cells) - contractile - smooth muscle cells - outside of seminiferous tubules -> push sperm out of seminiferous tubule lumen into epididymis

Question 13

What makes peritubular myoid cells contract?

Answer 13

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

Question 14

How long is epididymis and how it fits into testis?

Answer 14

Epidydimis - 6m long - very coiled to fit inside the scrotum on top of testis

Question 15

What is the function of epididymis?

Answer 15

Epididymis function:
- sperm concentration - sperm becomes more concetrated - majority of liquid absorbed
- movement
- structural maturation
- sperm storage before ejaculation - also stored in vas deferens

Question 16

What is an important epididymis environment condition for sperm maturation?

Answer 16

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

Question 17

What epididymis structure helps concentrate the sperm?

Answer 17

Epididymal stereocilia help concentrate the sperm - on the apical epithelial cell surface - stereocilia - increase SA for absorption of testicular fluid

Question 18

What is required for normal epididymis function?

Answer 18

Androgens (testosterone) required for normal development and function of the epididymis - testosterone KO epididymis shriveled

Question 19

What is the function of vas deferens?

Answer 19

Vas deferens provides contractile power for ejaculation and stores some of the sperm along epididymis

Question 20

How is sperm moved through vas deferens?

Answer 20

Vas deferens - straight muscular tube - thick muscular layers contract in peristalsis - move sperm along in ejaculation

Question 21

What is a surgical contraceptive for males?

Answer 21

Vasectomy - ligation of vas deferens - sperm can’t pass thorugh - sperm phagocytosed - reabsorbed by the system

Question 22

What is a popular anatomical target for male contraception?

Answer 22

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

Question 23

What is congenital bilateral absence of vas deferens (CBAVD)?

Answer 23

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

Question 24

What is the composition of semen?

Answer 24

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

Question 25

What are the two organs producing seminal fluid?

Answer 25

Accessory glands: **prostate gland** + **seminal vesicle** - attached to vas deferens - **mix with sperm**

Question 26

What are the components of seminal fluid produced by the seminal vesicle?

Answer 26

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

Question 27

Explain how seminal fluid changes it viscosity

Answer 27

**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

Question 28

What are the components of seminal fluid produced by the prostate gland?

Answer 28

Prostatic fluid mixes with sperm - first part of ejaculate - **alkaline + contains Zn ions**

Question 29

Explain what is benign prostatic hyperplasia (BPH)?

Answer 29

**Benign prostatic hyperplasia** (BPH) - **non-cancerous enlargement of prostate** due to **cell multiplication** - normally happens at older age

Question 30

Explain what is prostate specific antigen (PSA)

Answer 30

**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**

Question 31

What is required for normal prostate function?

Answer 31

**Androgens** - when **no androgens prostate shrivels** - lumen decreases

Question 32

What structure makes the penis erect?

Answer 32

Penis erects when **corpus cavemosum enlarges** - **cavernosal spaces expand**

Question 33

What is the mechanims behind penis erection to deliver sperm into female tract?

Answer 33

**cGMP levels relax smooth muscle** which makes the **penis erect** - **viagra inihbits cGMP** **degradation** - erect for longer

Question 34

Lecture summary