Repro: Coitus Flashcards
What changes to spermatids have to undergo to become spermatozoa?
The head undergoes nuclear condensation
The acrosome develops golgi-apparatus to make hydrolytic enzymes that enable penetration of the ovum
The mid piece has mitochondria packed around contractile filaments
There is a flagellum produced (tail)
What happens if sperm in the epididymis is not expelled?
Can be stored for several months but is phagocytosed by the epithelial cells
List the 4 phases of coitus
- excitement
- plateau
- orgasmic
- resolution
Describe the excitement phase in the male
Stimulation causes activation of sacral parasympathetic neurones and inhibits thoracolumbar sympathetic neurones.
The release of Ach binds to M3 receptors on endothelial cells which increases Ca and causes NO production.
NO causes vasodilation in the corpus cavernosa so there is increased blood flow causing erection.
Outline the plateau phase in the male
There is activation of the sacrospinous reflex which causes contraction of the ischiocavernosus at the base of the penis which causes venous engorgment.
The cowper’s glands are stimulated and secrete substances to lubricate and neutralise the urethra
Describe the emission phase in males
There is stimulation of the thoracolumbar sympathetic reflex which causes the smooth muscle in the vas deferens, ampulla of rectum and prostate to contract .
The internal and external urethral sphincters contract to prevent retrograde ejaculation
Describe the ejaculation phase in males
The sympathetic nervous system (L1,2) causes contraction of glands and ducts
The filling of internal urethra stimulates the pudendal nerve which causes contraction of the ischiocavernosus and bulbocavernosus which expels the semen
The anal sphincter contracts
Describe the resolution phase in males
There is activation of the thoracolumbar sympathetic pathway which causes contraction of the arteriolar smooth muscle in the corpus cavernosum
There is increased venous return and the penis becomes flaccid
No further orgasm is possible
Describe the excitement phase in the female
There is activation of sacral parasympathetic neurones and inhibition of thoracolumbar sympathetic neurones.
The clitoris engorges with blood and the uterus elevates. The inner 2/3rds of the vagina lengthens and expands to accommodate a penis
There is vaginal lubrication
Describe the plateau phase in females
There is further increase in muscle tone, heart rate and blood pressure
The labia minors deepen in colour due to increased blood flow and the clitoris withdraws under its hood.
There is bartholins gland secretion to lubricate the vestibule
Describe the plateau phase in females
The uterus is fully elevated and the inner 2/3rds of the vagina is fully distended
The outer 1/3 of the vagina forms the orgasmic platform - smooth muscle contracts
Describe the orgasm phase in females
The orgasmic platform (outer 1/3 of vagina) rhythmically contracts 3-15 times. The inner 2/3rds remains motionless
The uterus and anal sphincter contracts
The clitoris remains retracted under its hood.
Describe the resolution phase in females
There isnt one - multiple orgasms are possible
What is the G spot?
An area of erotic sensitivity on the anterior wall of the vagina.
The tissue is similar to that of the prostate so fluid released during ejaculation may be similar to prostatic secretions
What happens to the female sexual response with ageing?
(Particularly at the time of menopause)
- Some women report reduced desire
- Reduced vasocongestion so less vaginal lubrication
- loss of elasticity of vaginal and urethral tissue
- length and width of vagina decrease
- number of orgasmic contractions reduced
