13 - Repro - Conception Flashcards Preview

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Flashcards in 13 - Repro - Conception Deck (31):
1

Name the 4 phases of coitus:

1) Excitement
2) Plateau
3) Orgasmic
4) Resolution

2

Define coitus:

Act of sexual intercourse resulting in the deposition of sperm into the cervix

3

Which types of neurons are activated/inhibited during the excitement phase of coitus?

Activated = Sacral parasympathetic neurons
Inactivated = Thoracolumbar sympathetic neurons

4

How does the activation of parasympathetic neurons result in erection?

- Ach acts on M3 receptors on endothelial
- Gq receptors = ^Ca2+ = eNOS activation
- ^NO production
- vasodilation of corpora cavernosa
- ^blood flow to penis
- erection

5

What happens to the scrotal skin during the excitement phase of coitus?

Thickens + tenses

6

Which spinal reflex is activated during the plateau phase of coitus in males? What does this activate?

Sacrospinous reflex
- Contraction of ischiocavernosus
- Stimulation of bulbourethral glands

7

What happens to the testes during the plateau phase of coitus?

Become engorged + elevated

8

Which spinal reflex is activated during the orgasmic phase of coitus? What are the consequences of this in the male?

Thoracolumbar sympathetic reflex
- Contraction of smooth muscle of vas deferens, prostate, seminal vesicles, internal and external urethral sphincters
- Semen pools in urethral bulb (internal urethra)

9

What stimulates the pudendal nerve resulting in ejaculation?

Filling of the internal urethra (due to thoracolumbar sympathetic reflex)

10

What prevents a male from immediate repeated orgasms?

Refractory period due to penile flaccidity occuring in the resolution phase of coitus:
- vasoconstriction in corpora cavernosum allows restoration of venous flow

11

Describe the changes to the female genital tract during the excitement phase of coitus:

- Clitoris engorges
- Vaginal lubrication
- Inner 2/3rds of vagina lengthens and expands
- Uterus elevates

12

Describe the changes to the female genital tract during the plateau phase of coitus:

- Labia minora deepen in colour
- Clitoris withdraws under hood
- Bartholin's gland secretions lubricate vestibule

13

Where is the orgasmic platform of a female?

Outer 1/3rd of vagina

14

Why does ageing often reduce sexual desire?

- Change in body shape = lower self-esteem
- Decreased lubrication of female tract
- Loss of elasticity of vaginal tissue
- Decreased number of orgasmic contractions
- More rapid resolution

15

Immediately post-ejaculation, what happens to prevent sperm being lost in the vagina?

Semen coagulates due to clotting factors (fibrinogen + semenogelin)

16

Which gland is responsible for the production of the clotting factors present in semen? Name the main 2 clotting factors:

Seminal vesicles:
- Fibrinogen
- Semenogelin

17

What reactions occur during the passage of sperm from the cervix to the fallopian tube?

- Capacitation
- Acrosome reaction

18

What occurs during capacitation, and how long does it typically take?

- Removal of glycoprotein coat - exposes acrosomal enzymes
- Tail movements change from waves to whip-like motion

Several hours

19

Which cells make up the corona radiata?

Follicular cells

20

What triggers the acrosome reaction?

The passage of sperm through the corona radiata

21

Describe the acrosome reaction:

- Proteins on head of sperm bind to ZP3 proteins on zona pellucida
- Signalling mechanism = ^Ca2+ and ^cAMP in sperm
- Acrosomal enzymes digest through zona pellucida ~ 15 mins

22

How long does it usually take for sperm to digest through the zona pellucida?

~ 15 minutes

23

To which proteins on the zona pellucida do sperm bind to?

ZP3 proteins

24

Name the reaction which prevents polyspermy:

Cortical reaction

25

Describe the cortical reaction (to prevent polyspermy):

Fast block = Na+ channels open = depolarisation of oocyte membrane

Slow block = Ca2+ released from ER = exocytosis of cortical granules

26

Approximately how many sperm per ejaculation reach the fertilisation site?

~ 300 sperm

27

How many sperm are required to disperse the zona pellucida on average?

~ 299

28

How long do sperm survive in the female genital tract?

~ 5 days

29

When is the fertile period of the menstrual cycle?

Day 11-16 of menstrual cycle

30

Define syngamy:

The union of male and female pronuclei to form a diploid zygote

31

How can polyploidy occur?

- Failure of cortical reaction
- Failure to extrude second polar body