7. Conception and Contraception Flashcards
What is the normal volume of ejaculate?
2-4ml.
What are the main constituents of semen?
Testes: sperm, >40 x 10^6 per ejaculate.
Seminal vesicles = 60% of volume: alkaline fluid, fructose, prostaglandins, clotting factors (fibrinogen).
Prostate gland = 25% of volume: milky + acidic fluid, proteolytic enzymes, citric acid, phophotase.
Bulbourethral glands/Cowper’s glands = small volume: alkaline fluid, mucous.
Describe the physiological process involved in emission.
Emission = movement of ejaculate into the prostatic urethra before ejaculation. This is from peristalsis of the vas deferens and secretions from the seminal vesicles.
What are the stimulants in erection of the penis?
Psychogenic, tactile (sensory afferents of penis and perineum).
What are the efferents involved in erection of the penis?
Soamtic and autonomic effects - pelvic nerve (PNS), and pudendal nerve (somatic).
Outline the haemodynamic changes in erection.
Inhibition of sympathetic arterial vasoconstrictor nerves, activation of parasympathetic nervous system via pelvic nerve, activation of non-adrenergic + non-cholinergic nerves to arteries releasing NO, NO diffuses into and causes relaxation of vascular muscle.
How does activation of parasympathetic nervous system via pelvic nerve contribute to erection?
Release of ACh -> M3 receptors.
Rise in [Ca2+] -> activation of NO.
NOS -> formation of NO.
How does NO cause relaxation of vascular smooth muscle once it’s diffused in?
NO -> cGMP -> Ca2+ taken up into stores so lower [Ca2+] meaning less actin-myosin cross-bridges formed.
How do the corpa cavernosa change in erection?
Central arteries straighten and enlarge lumen so more blood can flow into and dilate the cavernous spaces.
How does the corpus spongiosum change in erection?
Dilates a bit, not too much otherwise the urethra would be closed off.
How do the bulbospongiosus and ischiocavernosus muscles contribute to erections?
Compress veins egressing from corpora cavernosa, impeding return of venous blood. Helps engorge the corpa cavernosa to become engorged with blood -> turgid.
What are the causes of erectile dysfunction?
Physchological - descending inhibition of spinal reflexes, tears in fibrous tissue of corpa cavernosa, vascular (arterial and venous, most common), factors blocking NO (alcohol, anti-hypertensives, diabetes).
What can be used to treat erectile dysfunction and how does it work?
Viagra - inhibits breakdown of cGMP, maintain erection.
What are the physiological changes in the female that facilitate coitus?
Vaginal lubrication, swelling and engorgement of the external genitalia, internal enlargement of the vagina, cervical mucus.
How does cervical mucus change under the influence of oestrogen compared to progesterone and oestrogen?
Oestrogen - abundant, clear, non-viscous mucous.
Progesterone + oestrogen - thick, sticky mucous plug.
What is the mechanism of ejaculation?
Spinal reflex. Sympathetic nervous system control (L1, L2). Contraction of glands and ducts by smooth muscle, bladder internal sphincter contracts to prevent entry of semen into bladder, rhythmic striatal muscle contractions (of pelvic floor, ischiocavernosus, bulbospongiosus, hip and anal muscles).
How does sperm travel through the cervix and uterus?
Most sperm are lost in the vagina. Those that enter uterus travel 15-20cm to reach uterine tube, which takes a few hours. The sperm themselves have propulsive capacity so move by this and currents in fluid from ciliated cells in the uterine tract.
How does sperm change after ejaculation?
Semen coagulates after ejaculation then re-liquifies after 10-20 minutes.
What are capacitation and acrosomal reactions of sperm induce dby?
Influx of calcium and rise in cAMP in spermatozoa.
