07.1 Coitus and Fertilisation

Question 1

What are the 4 phases of coitus?

Answer 1

Excitement
Plateau
Orgasmic
Resolution

Question 2

How does the reversible erection physiologically occur during the excitement phase?

Answer 2

Parasympathetic nerves
M3 receptors
NO Production
Arteriolar vasodilation
Corpus cavernosa fills with blood

Question 3

What occurs in the plateau phase for men?

Answer 3

Sympathetic stimulation
Contraction of ischiocavernosus - impedes venous return and arteriolar flow = maintains erection
Cowper’s and Littre’s glands - lubricates and neutralises acidic urine

Question 4

What occurs in the orgasm stage for men?

Answer 4

Emission - Ejaculate pooled in urethral bulb

Ejaculation - Expulsion of semen

Question 5

What happens in the resolution stage of coitus for men?

Answer 5

Activation of sympathetic nervous system
Increased venous return
Refractory period

Question 6

What happens in the excitement stage for females?

Answer 6

Vaginal lubrication
Clitoris engorges with blood
Uterus elevates
Increase in HR and BP

Question 7

What happens in the plateau phase for women?

Answer 7

Further increase in HR and BP
Clitoris withdraws
Bartholins gland lubricates vestibule
Orgasmic platform forms

Question 8

What happens in the orgasmic phase for women?

Answer 8

Orgasmic platform contracts rhythmically 3-15 times
Uterus contracts, anal sphincter contracts
No refractory period

Question 9

What happens in the resolution phase for women?

Answer 9

Clitoris descends and engorgement subsides
Uterus descends
Vagina shortens and narrows

Question 10

How long can sperm survive in the female genital tract?

Answer 10

Up to 5 days

Question 11

How long can the oocyte live for?

Answer 11

Up to 24 hours

Question 12

What reaction prevents polyspermy?

Answer 12

Cortical reaction

Question 13

How can polyploidy occur?

Answer 13

Polyspermy

Failure of extrusion of 2nd polar body