Male reproductive physiology Flashcards
What is the function of the testes?
Production of gametes (spermatozoa) and male sex hormone (testosterone)
Where does spermatogenesis and spermiogenesis take place?
Convoluted seminiferous tubules in the testes
Where does testosterone production take place?
interstitial cells of leydig, inbetween seminferous tubule coils
Where is preseminal fluid created?
Acessory glands of male reproductive tract- seminal vesicles, prostate gland and bulbourethral glands (Cowper’s)
Where do the testes develop in the foetus?
Abdomen- descend down inguinal canal so lie in scrotum at birth
Cryptorchidism- undescended testes, can lead to infertility and inc. risk of cancer
What are the 4 stages of sperm formation?
- formation of haploid gametes from spermatogonium (dip)
- Spermiogenesis- spermatids undergo changes (motility)
- Spermiation- SZ released into lumen of sem. tubules
- Capacitation- modification of SZ between epididymis/ female genitals (fertilisation)
Where do spermatozoa develop?
Progenitor cells next to BM (spermatogonia)- divide by mitosis, one will mature to become SZ, other left behind forming permanent reserve
What happens to daughter cell after maturation?
Meiosis- 2 divisions, inital duplication of gen. material- primary spermatocyte with 2 copies of each 23 CS pairs.
What occurs with the gene pairs after the initial duplication of daughter cell?
Hom. chromosomes line up and genetic recombination occurs- then split and cell division occurs (m1)
M1 forms secondary spermatocytes (haploid, unpaired chromosomes)
What is the final divisions of secondary spermatocytes?
the final division- each spermatid contains hap. number unduplicated chromosomes
Must undergo further maturation > motile SZ (SG, spermiation, cap)
What is spermiogenesis?
Differentiation into motile gametes within folds of sertoli cells, through nourishment, phagocytosing old cells and protecting sperm from bloodborne toxins
What other roles do sertoli cells have?
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)
What is contained in the spermatozoon head?
Genetic material and enzymatic cap (acrosome)
What is contained in the sperm neck?
Centrioles ( essential in sperm division, progenitors of centrioles in foetal cells), and many mitochondria for flagellar movement (corkscrew motion)
What is the purpose of hormonal control of male reproduction?
Turnover of spermatozoon production, ensures appt. level of testosterone to maintain spermatogenesis/ secondary sexual characteristics of the male
What is the function of the hypothalamo/anterior pituitary/end organ axis in male hormonal control?
GRH released from HT daily, ticking over gametogenesis and testosterone production.
Carried in HP circulation until reaching AP, stimulates LH and FSH.
What is the role of FSH?
FSH promotes spermatogenesis by acting (along with locally produced testosterone) on sertoli cells- feedback by insulin on production in AP
What is the role of LH?
Effect on interstitial cells of Leydig, causing them to releaes testosterone- feedback on production in AP and GnRH production in HT
What is the function of testosterone?
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
How does sexual intercourse occur?
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)
How does an erection occur?
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.
How does the erection reflex occur?
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
What happens in the emission phase of ejaculation?
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
What happens in the expulsion phase of ejaculation?
Reflex contractions of skel muscle around base of penis (bulbocavernosus muscle), expel semen into vagina.
What is the composition of semen?
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.
