7.1 Coitus and Fertilisation

Question 1

What is stimulated in the excitement phase of coitus?

Answer 1

Sensory and psychological stimulation of the limbic system
Sacral parasympathetic neurones are activated
Thoracolumbar sympathetic neurones are inhibited

Question 2

In the excitement phase in the male, how is vasodilation achieved?

Answer 2

Ach release –> M3 receptors –> increased Ca2+ release –> activation of eNOS –> NO production

Question 3

How is an erection gained?

Answer 3

Vasodilation of the corpus cavernosa
Increased arterial penile blood flow
Reduced venous drainage

Question 4

What happens in the male plateau phase?

Answer 4

Sacrospinous reflex activated
Ischiocavernosus contracts and compresses the crus penis resulting in venous engorgement
Cowper’s and Littre’s glands secrete lubricating fluid
Testis completely engorged

Question 5

What is emission in the male sexual response cycle?

Answer 5

Contraction of the vas deferens, ampulla, seminal vesicles and prostate to create a pool of semen in the urethral bulb

Question 6

How does ejaculation occur?

Answer 6

Contraction of the glands, ducts and internal urethral sphincter. Pudendal nerve contracts the genital organs, ischiocavernosus and bulbocavernosus.
Sperm is expulsed.

Question 7

How is the male reproductive system returned to normal after coitus?

Answer 7

Increased venous return from the penis resolves the erection.
Refractory period where the male cannot produce enough sperm to repeat the cycle straight away

Question 8

What happens in the female excitement phase?

Answer 8

Vaginal lubrication from the Bartholins glands
Clitoris engorges with blood
Uterus elevates
Vagina lengthens and expands

Question 9

What happens in the female plateau phase?

Answer 9

Increase in muscle tone, BP and heart rate
Labia minora deepens in colour
Clitoris retracts
Orgasmic platform forms

Question 10

What happens in the female orgasmic phase?

Answer 10

Orgasmic platform contracts rhythmically
The uterus and anal sphincter contract
No refractory period

Question 11

How does the female reproductive system resolve after coitus?

Answer 11

Clitoris descends
Labia returns to normal size
Uterus descends
Vagina shortens

Question 12

Describe the breast changes thoughout coitus

Answer 12

Excitement–> breast size increases, nipple becomes erect
Plateau and orgasm–> Greater size increase, areola increases in size, sex flush
Resolution–> Return to normal size, flush disappears

Question 13

What is the G spot?

Answer 13

Area of erotic sensitivity located along the anterior wall of the vagina

Question 14

Describe some dysfunctions in sexual desire

Answer 14

Hypoactive- little or no interest
Aversion- fear or repulsion of sex
Hyperactive- very strong sexual desire
Nymphomaniac- obsessed with sex

Question 15

What is impotence?

Answer 15

Failure to get an erection

Question 16

What is oligospermia?

Question 17

When is the woman’s fertile period?

Answer 17

Days 11-16 of the menstrual cycle

Question 18

How long can sperm survive in the female reproductive tract?

Answer 18

5 days

Question 19

How many sperm cells reach the ovum?

Answer 19

300

Question 20

Describe the acrosome reaction

Answer 20

Sperm contacts corona radiata
Pushes through granulosa cells
Bind to ZP3 proteins on the zona pellucida
Acrosome enzymes digest zona pellucida
One sperm penetrates

Question 21

How is polyspermy blocked?

Answer 21

Wave of depolarisation from point of sperm entry.
Na+ channels open to depolarise cell
Ca2+ released from ER cause cortical granules to exocytose
Zona pellucida is strengthened

Question 22

What is syngamy?

Answer 22

Oocyte completes meiosis II and the oocyte and sperm nuclei fuse

Question 23

What is polyploidy?

Answer 23

3 or more pronuclei

From additional sperm or failure to expel other polar body