Session 7 - Conception and Pregnancy Flashcards
What is the average amount of semen in ml? Number of sperm per ml? Number of sperm swimming forward vigorously? Number of sperm with abnormal morphology? How long should liquefaction take?
- 2-4 ml
- 20-200 million sperm per ml
- >60% sperm swimming forward vigorously
- <30% abnormal morphology
- Liquefaction within 1 hour – sperm solidifies quickly but liquefies within 1 hour
Describe the physiological processes involved in emission. What spinal nerves are involved?
- Movement of ejaculate into prostatic urethra – can get some leakage
- Vas deferens peristalsis
- Accessory gland secretions e.g. bulbourethral
- contraction of glands and ducts
- bladder internal sphincter contracts to prevent urine output
- rhythmic striatal muscle contractions
Sympathetic L1,L2
What needs to occur for an erection to take place?
- Arteries of corpora cavernosa need to vasodilate
- Therefore, need decrease in intracellular calcium in the smooth muscles of the arteries
- Contraction of skeletal muscle at base of penis – increases pressure in penis and contributes to erection
- Blockage of venous drainage to keep blood in the penis
Explain the mechanism through which the penis vasodilates
- PS stimulation results in release of ACH to the endothelium of the artery
- Ach bonds to M3 receptor and results in a rise in intracellular calcium, activation of NOS and formation of NO
- NO diffuses into vascular smooth muscle and increases amount of cGMP in the smooth muscle cell. NO can also be released directly from nerves.
- cGMP results in increased uptake of calcium in SER, therefore less calcium in cell –> erection.
How does viagra work?
Works by inhibiting cGMP breakdown by PDE5
Explain how ED can result from psychological conditions or tears in fibrous tissue of corpora cavernosa.
- Can be psychological – results in stimulation of sympathetic nervous system –> loss of erection
- Tears in fibrous tissue of corpora cavernosa –> blood leaves area and erection lost
What occurs to a female when sexually excited?
Blood engorgement and erection of clitoris, vaginal mucosa, breast and nipples
Describe what happens when a sperm meets an egg
- Sperm pushes through granulosa cells and proteins on sperm head bind to ZP3 proteins of zona pellucida (ZP)
- Binding triggers acrosome reaction:
- Acrosomal enzymes released from sperm digest path through ZP
- Sperm penetrates and fusion of plasma membrane soccurs
- Sperm moves into cytoplasm to form a zygote
- Polyspermy blocked by the cortical reaction
- Egg completes Meiosis 2 and the 2 nuclei fuse
- Cleavage occurs – a series of metabolic changes and rapid mitotic division, increasing number of cells without growth, forming morulla.
Describe th eprocess involved in sperm transport through the cervix and uterus
- Sperm coagulates due to clotting factors – preventing sperm from being physically lost
- 15 mins later, semen re-liquefies by action of proteolytic enzymes from prostate. Majority of sperm do not enter cervix and are lost by leakage from vagina
- Sperm that enter uterus travel 15-20 cm to reach uterine tube. Transport is result of their own propulsive tails and the fluid currents caused by action of ciliated cells in the uterine tract.
What is the capcitation of sperm? what happens in capacitation?
Maturing of sperm.
- Sperm cell membrane changes to allow fusion with oocyte cell surface – removal of glycoprotein coat
- Tail movement changes from a beat to a whip-like action.
- Sperm becomes responsive to signals from oocyte
How is capacitation and acrosome reaction induced in sperm?
Both induced by influx of calcium and rise in cAMP in spermatozoa.
What is the acrosome reaction of sperm and what happens during it?
Maturing of sperm when it comes into contact with oocyte zona pellucida
- Membranes fuse
- Acrosome swells and frees its content by exocytosis
- Proteolytic enzymes and further binding facilitate penetration of zona pellucida by sperm.
Explain why the pulling out technique isnt 100%
Sperm found in pre-ejaculate
What is the rhythm method of contraception? What are the fertile periods of the menstrual cycle?
sex is only had on days where fertilisation isn’t possible. Fertile period is day 7-16 of a regular 28 day cycle.
What is a vasectomy?
Divide the vas deferens bilaterally, preventing sperm from entering ejaculate.
