Male reproductive physiology

Question 1

What is the function of the testes?

Answer 1

Production of gametes (spermatozoa) and male sex hormone (testosterone)

Question 2

Where does spermatogenesis and spermiogenesis take place?

Answer 2

Convoluted seminiferous tubules in the testes

Question 3

Where does testosterone production take place?

Answer 3

interstitial cells of leydig, inbetween seminferous tubule coils

Question 4

Where is preseminal fluid created?

Answer 4

Acessory glands of male reproductive tract- seminal vesicles, prostate gland and bulbourethral glands (Cowper’s)

Question 5

Where do the testes develop in the foetus?

Answer 5

Abdomen- descend down inguinal canal so lie in scrotum at birth
Cryptorchidism- undescended testes, can lead to infertility and inc. risk of cancer

Question 6

What are the 4 stages of sperm formation?

Answer 6

1. formation of haploid gametes from spermatogonium (dip)
2. Spermiogenesis- spermatids undergo changes (motility)
3. Spermiation- SZ released into lumen of sem. tubules
4. Capacitation- modification of SZ between epididymis/ female genitals (fertilisation)

Question 7

Where do spermatozoa develop?

Answer 7

Progenitor cells next to BM (spermatogonia)- divide by mitosis, one will mature to become SZ, other left behind forming permanent reserve

Question 8

What happens to daughter cell after maturation?

Answer 8

Meiosis- 2 divisions, inital duplication of gen. material- primary spermatocyte with 2 copies of each 23 CS pairs.

Question 9

What occurs with the gene pairs after the initial duplication of daughter cell?

Answer 9

Hom. chromosomes line up and genetic recombination occurs- then split and cell division occurs (m1)
M1 forms secondary spermatocytes (haploid, unpaired chromosomes)

Question 10

What is the final divisions of secondary spermatocytes?

Answer 10

the final division- each spermatid contains hap. number unduplicated chromosomes
Must undergo further maturation > motile SZ (SG, spermiation, cap)

Question 11

What is spermiogenesis?

Answer 11

Differentiation into motile gametes within folds of sertoli cells, through nourishment, phagocytosing old cells and protecting sperm from bloodborne toxins

Question 12

What other roles do sertoli cells have?

Answer 12

Tight junctions between SC and BM : steroids penetrate and proteins may go other way
-secrete sperm into lumen (spermiation) w seminiferous tubule fluid ( high k+, andorgens, estrogens, inositol, glutamic acid)

Question 13

What is contained in the spermatozoon head?

Answer 13

Genetic material and enzymatic cap (acrosome)

Question 14

What is contained in the sperm neck?

Answer 14

Centrioles ( essential in sperm division, progenitors of centrioles in foetal cells), and many mitochondria for flagellar movement (corkscrew motion)

Question 15

What is the purpose of hormonal control of male reproduction?

Answer 15

Turnover of spermatozoon production, ensures appt. level of testosterone to maintain spermatogenesis/ secondary sexual characteristics of the male

Question 16

What is the function of the hypothalamo/anterior pituitary/end organ axis in male hormonal control?

Answer 16

GRH released from HT daily, ticking over gametogenesis and testosterone production.
Carried in HP circulation until reaching AP, stimulates LH and FSH.

Question 17

What is the role of FSH?

Answer 17

FSH promotes spermatogenesis by acting (along with locally produced testosterone) on sertoli cells- feedback by insulin on production in AP

Question 18

What is the role of LH?

Answer 18

Effect on interstitial cells of Leydig, causing them to releaes testosterone- feedback on production in AP and GnRH production in HT

Question 19

What is the function of testosterone?

Answer 19

Gives male phenotype in utero, prenatal structure changes resulting in male external genitalia
Develops/maintains male rep. system, responsible for 2nd sexual characteristics, e.g growth spurt etc
Anabolic hormone (muscle deposition, ^ MR) and libido and aggression

Question 20

How does sexual intercourse occur?

Answer 20

Motile male gametes > female GT to ovum. Erection, penetration and ejaculation, sperm near opening of cervical canal ( access to uterus and FT where fertilisation of egg can take place)

Question 21

How does an erection occur?

Answer 21

Dilation of penile arterioles > corpus cavernosa and spongiosum. Erotic cognitive stimuli, reinforced by sensory receptor stimulation of glans- further reinforced when veins draining penis compressed.

Question 22

How does the erection reflex occur?

Answer 22

PS dilator nerves and inactivation of S constrictor nerves- NO vasodilator pathway essential to erections, drugs ^ NO production and related VD (cGMP) can treat ED

Question 23

What happens in the emission phase of ejaculation?

Answer 23

Symp. reflex stimulates SM walles of epididymus, VD and accessory glands (prostate, sem vesicles- mixing of sperm and secretions, semen formed and deposited in urethra

Question 24

What happens in the expulsion phase of ejaculation?

Answer 24

Reflex contractions of skel muscle around base of penis (bulbocavernosus muscle), expel semen into vagina.

Question 25

What is the composition of semen?

Answer 25

Fluid from seminal vesicle (60%), rich in fructose to nourish sperm, prostaglandins and agents promote clotting of semen.
25% from prostate gland (citrate/proteases)- break down clotted semen
PSA also secreted ( prostate cancer marker)
Remaining- mucoid secretion of bulbourethral gland, lubricates urethra and clears away urine pre ej.