Male reproductive physiology

Question 1

Where do spermatogenesis and spermiogenesis occur?

Answer 1

seminiferous tubules of tests

Question 2

What cells produce testosterone?

Answer 2

interstitial cells of leydig

Question 3

What are the accessory glands and what do they do?

Answer 3

seminal vesicles
bulbourethral gland
prostate gland
- produce fluid medium used to transport spermatozoa

Question 4

What is cryptorchidism and why does it need to be treated?

Answer 4

• undescended tests (never descend down inguinal canal)
• can lead to infertility and increased cancer risk
• so treated with surgery

Question 5

Why are testes located outside the body?

Answer 5

• Temperature regulation, need temp of 32 degrees for spermatogenesis
• being outside the body cools them

Question 6

How are testes temperature regulated?

Answer 6

• cremaster muscle does pull the testes toward the body in cold weather to keep them warmer
• use counter current system with spermatic arteries and pampiniform plexus to maintain 32 degree temp

Question 7

What is spermatogenesis?

Answer 7

Production of haploid gametes from diploid precursors (spermatogonium) which are found at basal lamina of seminiferous tubules

Question 8

What is spermiogenesis?

Answer 8

gametes (spermatids) change to become motile

Question 9

What is spermiation?

Answer 9

release of spermatozoa into lumen of seminiferous tubules

Question 10

What cells house the spermatozoa as they undergo spermiogenesis and what else do they do?

Answer 10

Sertoli cells

• nourish sperm cells
• phagocytose old cells
• protect from blood toxins
• form blood testicle barrier which allow steroids in but not proteins
• secrete sperm into lumen along with seminiferous tubule fluid

Question 11

What is the structure of the spermatozoon?

Answer 11

• head made of nuclear material and acrosomal cap
• mid section contains centrioles (needed for cell division), mitochondrial spiral (provides energy for tail) and tail = flagella (moves in corkscrew motion)

Question 12

How are hormones controlled in males?

Answer 12

• Hypothalamus release GRH which stimulates FSH and LH release from ant pituitary
• FSH stimulates inhibin release and spermatogenesis by the Sertoli cells
• LH stimulates testosterone release by Leydig cells
• Testosterone also stimulates sertoli to continue spermatogenesis
• negative feedback from testosterone on GRH and LH
• Negative feedback from inhibin on FSH

Question 13

What is the function of testosterone?

Answer 13

• essential in spermiogenesis but must be local source rather than taking testosterone supplements (which will reduce endogenous testosterone)
• development of male phenotype in utero
• further changes during puberty

Question 14

What does testosterone cause during puberty?

Answer 14

• male reproductive structure in early adulthood and secondary sexual characteristics
• causes adolescent growth spurt in bones and musculature and fusion of epiphyses
• increases metabolic rate
• increases muscle deposition
• causes behavioural changes

Question 15

How is erection achieved?

Answer 15

• Corpus cavernosa and spongiosum fill with blood to become turgid
• Erotic stimuli, mechanical stimuli to glans and anterior penis
• venous compression to prevent blood leaving
• sympathetic constrictor nerves inhibited and parasympathetic dilator nerves are activated
• Nitrous oxide vasodilators and cGMP are essentially and often used in erectile dysfunction medication

Question 16

What are the two phases of ejaculation?

Answer 16

• Emission

- Expulsion

Question 17

What are the components of the semen?

Answer 17

• fluid from seminal vesicles
• rich in fructose (for nourishment)
• prostaglandins (prevent clotting)
• prostate gland secretions contain citrate and protease (breakdown clotted semen)
• PSA (prostate specific antigen) also secreted
• mucoid secretions of bulbourethral gland which lubricate urethra and clear urien before ejaculation

Question 18

What is capacitation?

Answer 18

rendering of spermatozoa to become capable of fertilising female gamete
- occurs in-between epididymis and female genital tract

Question 19

What is capacitation?

Answer 19

rendering of spermatozoa to become capable of fertilising female gamete

• occurs in-between epididymis and female genital tract
• not mature until reaches capacitation and can enzymatically penetrate ovum using acrosomal cap

Question 20

What happens in spermatogenesis?

Answer 20

• spermatogonia divide via mitosis, one cell will mature to become spermatozoa and one is left as permanent reserve
• daughter cell differentiates to form primary spermatocyte (diploid with duplicated chromosomes i.e. 2n + 2n)
• primary spermatocyte will then undergo meiosis I (form two secondary spermatocytes)
• Secondary spermatocytes are haploid cells but with duplicated chromosomes (n + n)
• then Meiosis II to form 4 daughter cells
• daughter cells (spermatids) are haploid and have unduplicated chromosomes (n)
• these then undergo further maturation to become spermatozoa

Question 21

What occurs in the emission phase of ejaculation?

Answer 21

• sympathetic reflex stimulates nerves in smooth muscle of epididymus, vas deferens and accessory glands
• causing sperm and secretions of glands to mix to form semen

Question 22

What occurs the expulsion phase of ejaculation?

Answer 22

• reflex contraction of the skeletal muscle around base of penis
• this expels semen with great force into vagina