Sex And Fertilisayion Flashcards
Outline the epididymal maturation of sperm
• On entry, spermatozoa not capable of movement
• Once at the tail of the epididymis they are capable of movement and have the potential to fertilise (capable of interacting with oocyte to begin fertilisation)
• Addition of secretory products to
surface of sperm
• Maturation
– Dependent on support of the epididymis by androgens
What are the functions of semen
- Spermatozoa
- Seminal plasma - derived from accessory glands of the male reproductive tract
• Function: – Transport medium – Nutrition – Buffering capacity – ? Role for prostaglandins in stimulating muscular activity in the female tract
What are the phases in the huma sexual response
• Excitement phase
– Psychogenic and / or somatogenic stimuli
• Plateau phase
• Orgasm phase
• Resolution phase
– Return to haemodynamic norm followed by a refractory period in males
Explain male sexual response i - erection
Stimulants
Psychogenic
Tactile (sensory afferents of penis and perineum)
Efferents
Somatic and autonomic efferents
•Pelvic nerve (PNS)
•Pudendal nerve (somatic)
Result = haemodynamic changes
Describe teh anatomical changes in erection
• Tunica albuginea • Erection requires – Sinusoidal relaxation – Arterial dilation – Venous compression Tunica albuginea gives counter pressure to engorgement of corpus spongiosum. This contributes to venous compression
Describe the innervation and neurophysiology of erection
• Fibres – Lumbar and sacral spinal levels • Pelvic nerve and pelvic plexus • Cavernous nerve to corpora and vasculature • Inhibition of sympathetic arterial vasoconstrictor nerves • Activation of PNS • Activation of non-adrenergic, non-cholinergic, autonomic nerves to arteries, releasing Nitric Oxide (NO)
What are the roles of NO in erection
• Post-ganglionic fibres release ACh • ACh bonds to M3 receptor on endothelial cells • A rise in [Ca2+]i , activation of NO Synthase and formation of NO • NO diffuses into vascular smooth muscle and causes relaxation (vasodilation) • NO also released directly from nerves
What are the causes of erectile dysfunction
• Psychological (descending inhibition of spinal reflexes) - psychogenic smulation may bot be possible/may be interrupted • Tears in fibrous tissue of corpora cavernosa • Vascular (arterial and venous) • Drugs
Therapy to treat: Viagra™ slows rate at which cGMP is degraded - cGMP rapports erection
Descrime emmission
• Under sympathetic auto control
• Emission
– Movement of semen into prostatic urethra
– Contraction of SM in prostate, vas deferens and seminal vesicles - tubular structures with outer covering of SM - propel glandular secretions along duct system
• Ejaculation
– Expulsion of semen
What happens in ejactulation
• Contraction of glands and ducts (smooth muscle)
• Bladder internal sphincter contracts
– Preventing retrograde ejaculation
• Rhythmic striatal muscle contractions (pelvic floor, and perineal muscles ischiocavernosus, bulbospongiosus)
Give a summary of the autonomic control of male sexual function
Erection • Sympathetic – Inhibition (reduction of tone at arterioles) • Parasympathetic – Active
Ejaculation
• Sympathetic
– Active
• ducts
Describe the changes to cervical mucus over the menstrual cycle
• The character of cervical mucus changes over the course of the menstrual cycle
• Oestrogen
– Thin, stretchy - supports movement of male gamete through tract
• Oestrogen and progesterone
– Thick, sticky; forms a plug - inhospitable to sperm, forms a mechanical barrier
What is capacitation
- further maturation of sperm in female reproductive tract (6-8 hours)
- sperm cell membrane changes to allow fusion with oocyte cell surface
- tail movement changes from beat to whip-like action (fig B)
- now capable of undergoing the acrosome reaction (fig C)
What is the fertile window
- Spermatozoa 48 -72hr
- Oocytes 6 – 24 hr (max)
- Fertile period: sperm deposition up to 3 days prior to ovulation or day of ovulation
Give an overview o events in fertilisation
- Occurs normally in the ampulla of the uterine tubes
- requires loss of sperm outer shell (acrosome)
- penetration of ovum membrane, fusion of ova and sperm membrane
- eventual formation and fusion of pronuclei
