Coitus, Fertilisation and Preimplantation Flashcards
Describe what occurs in the excitement stage of the male sex response
- Psychological and physical stimulation of erogenous zones,
- Swelling and erection of penis due to PSNS,
- Relaxation of SM of corpora cavernosa, corpus spongiosum which allows increase in blood flow = increased volume and ridigity.
Describe the plateau stage of the male sex response
- Movement of ejaculate into prostatic or proximal part of urethra, under SNS control,
- Spinal reflex - forced expulsion of semen from urethra,
- Reflex reaction triggered by entry of semen from prostatic urethra into bulbous urethra
Describe the orgasm stage of the male sex response
- Release of tension,
- Generalised, rhythmic contraction of pelvic floor, ischiocavernosus and bulbospngiosus muscles,
- Spasmodic contractions of muscles of hip and anal sphincter.
Describe the resolution phase of the male sex response
- Return to pre-excitement state, personal satisfaction and well-being.
- Refractory period
Describe the excitement phase of the female sex response
- Psychological and physical stimulation of erogenous zones,
- Tumescence and erection of clitoris, engorgement of female tract
Describe the Plateau phase of the female sex response
- Marked vasocongestion,
- “Sex flush” - maculopapular rash on breasts, chest and epigastrium.
- Engorgement of labia, lower third of the vagina (with narrowing of diameter) and dilation of upper two thirds of vagina,
- Clitoral swelling and erection.
Describe the orgasm phase of the female sex response
- Release of tension,
- Generalised, rhythmic myotonic contractions of perivaginal muscles, anal sphincter and uterus
Describe the resolution phase of the female sex response
- Return to pre-excitement state, personal satisfaction and well-being.
- New excitement cycles may be initiated.
What is the most fertile stage of the cycle?
No more than 3 days before ovulation and no more than 1 day after ovulation. This is because sperm are viable for 24-72 hours and oocytes 12-24hours
What is the embryonic period?
The first 8 weeks where there is the preimplantation embryo, implantation and then differentiation and development of the organ systems
What is the foetal period?
8-40 weeks where differentiation continues and growth
Describe the transport of the ovum
- Fimbriae sweep over ovary surface and picks up the ovum.
- Sticky cumulus cells cling to the ciliated surface of the fimbriae.
- The movement of cilia and smooth muscle of fallopian tubule propels ovum to uterus.
- Fertilised in the ampulla
Describe the transport of sperm
- Ejaculation deposits 150-600 million sperm however mortality is high so only 50-100 make it due to acidic environment of vagina, uterotubal junction, phagocytosis by leukocytes and the length and energy requirements. Passage into cervical mucus depends on oestrogen-induced changes
Briefly describe the anatomy of a sperm cell
Head - Acrosome which contains enzymes to aid penetration of ovum and nucleus.
Midpiece - Contains mitochondria which provide energy for tail.
Tail - Specialised flagellum that propels sperm forward
What is capacitation of sperm?
Freshly ejaculated sperm cannot immediately penetrate ovum so capacitation occurs which results in;
- Change from wave-like beats to whip-like action of sperm tail,
- Sperm’s plasma membrane is altered so it is able to fuse with membrane of ovum.
