Male anatomy and function Flashcards
1
Q
the testes
A
- Contained within the scrotum
- Septa divide testis into ~250 lobules
- Each lobule contains 1-4 seminiferous tubules
- Male gametes develop in the seminiferous tubules
- Spermatogonia mature into spermatozoa
2
Q
ducts of the male repro system
A
- Sperm delivered to exterior through system of ducts:
- Seminiferous tubules –> Straight tubules –> Rete testis -> Efferent ductules –> Epididymis –> Vas deferens –> ejaculatory duct –> urethra
3
Q
seminiferous tubules
A
site of sperm production
lined by complex of stratified epithelium
4
Q
male HPG axis - hormonal regulation
A
- hypothalamus releases GnRH, stimulating ant pituitary to release FSH and LH
- LH stimulates leading cells to release testosterone. FSH stimulates the Sertoli cells to release ABP, inhibit and MIS. ABP binds to testosterone, keeping it at high concentration.
- inhibin negatively feeds back to ant pituitary, inhibiting further release of FSH. testosterone negatively feeds back to the hypothalamus and pituitary, inhibiting further release of GnRH, FHS and LH
5
Q
cells in the seminiferous tubules
A
o Spermatogonia develop into sperm
o Sertoli cells – nourishment & protection for developing sperm & produce androgen binding protein and growth factors & contain receptors to bind testosterone and FSH
o no blood supply
6
Q
cells in the interstitial space
A
o Leydig cells: secrete testosterone, in response to lutenizing hormone (LH) from the pituitary -> testosterone diffuses into seminiferous tubules
o Peritubular myoid cells: peristaltic movement
o Capillary cells of blood vessels
7
Q
blood-testes barrier
A
- Separates the testes from the normal circulatory processes of the body
- Tight junctions between adjacent Sertoli cells form the blood testis barrier
- Prevents blood and other body fluids entering the lumen of the seminiferous tubules
o Allows only secretions from Sertoli cells to enter
o Protects developing sperm from the body’s immune system
o Restricts passage of drugs to spermatocytes and spermatids
o No immune cells = no inflammation
8
Q
two phases to from mature sperm
A
- Spermiogenesis: remodelling and maturing of spermatids into mature spermatozoa (differentiation)
- Spermatogenesis: development of spermatozoa in seminiferous tubules
mitosis: production of identical daughter cells
meiosis: spermatogenesis, development of spermatozoa in seminiferous tubules
9
Q
spermatogenesis
A
- Meiosis: Formation of haploid Spermatids from diploid Spermatogonia (development of spermatozoa in seminiferous tubules)
- Stem cells enter into spermatogenesis ~ every 16 days
10
Q
spermatogenesis
A
- The remodelling and maturing of spermatids into mature spermatozoa through differentiation
- Occurs in close association with sertoli cells which provide nutrients
- 4 phases of maturation and remodeling
- Discarding excess cytoplasm (residual body) and adding tail and acrosomal cap
- The 4 phases of maturation and remodeling: 1 Golgi phase 2 Cap phase 3 Acrosome phase 4 Maturation phase
- A: round spermatid with small acrosomal vesicle
- B - Early cap-phase spermatid showing SPANXa/d staining of the nuclear periphery
- As the acrosomal cap migrates posteriorly spermatid begins to elongate
11
Q
spermatozoa (sperm)
A
- Head & acrosome for enzymatic penetration of the egg at fertilisation
- Midpiece containing the mitochondrion
- Tail for forward propulsion
- Sperm is stored in epididymis till needed
- During ejaculation sperm musculature in vas deferens rhythmically contracts
- Degradation of sperm which is not ejaculated
12
Q
genetic reflexes in men (sexual response cycle)
A
- Erection of penis: Dilatation of the penile arterioles & filling of the erectile tissues o Vasocongestion (tissue engorgement)
- Emission: Movement of semen into the posterior urethra due to contraction of prostate, vas deferens, seminal vesicles & bulbourethral glands
o Mediated mainly by sympathetic fibres via the hypogastric nerve
o Integrated in upper lumbar segments of the spinal cord - Ejaculation: Propulsion of semen out of the penis by contraction of the smooth muscles of the urethra and striated muscles of bulbospongiosus
o Reflex contraction of the bulbospongiosus -> pulsatile release of semen - Orgasm can occur without ejaculation
13
Q
erectile tissue in penis
A
- Corpus spongiosum: surrounds urethra
- Corpus cavernosa: paired dorsal erectile bodies
- During arousal, nerves in penis release vasoactive intestinal peptide (VIP) and nitric oxide (NO)
o vasodilation – increased blood flow to arteries in corpus cavernosa
o “helicine arteries“ empty into corpora cavernosa enclosed by the trabeculae engorging it with blood -> swelling = erection & compression of veins and venules to maintain erection
14
Q
semen
A
- Milky-white mixture of sperm and accessory gland secretions
- Contains fructose (ATP), protects & activates sperm, and facilitates sperm movement
- Alkaline fluid neutralizes acidity of male urethra and female vagina and enhances motility
- 2–5 ml semen are ejaculated ~20–150 million sperm/ml
15
Q
accessory gland secretions
A
- Seminal Vesicles: ~65% of seminal fluid, alkaline, prostaglandins, clotting proteins & fructose (ATP)
- Prostate: ~30% of seminal fluid, contains enzymes & secrets milky, slightly acid fluid
- Bulbourethral glands: <5% of seminal fluid, thick, clear mucus to lubricate glans penis, alkaline –> neutralizes traces of acidic urine in urethra
