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Flashcards in 13 - Repro - Conception Deck (31)
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Name the 4 phases of coitus:

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


Define coitus:

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


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

Activated = Sacral parasympathetic neurons
Inactivated = Thoracolumbar sympathetic neurons


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


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

Thickens + tenses


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


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

Become engorged + elevated


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)


What stimulates the pudendal nerve resulting in ejaculation?

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


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


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


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


Where is the orgasmic platform of a female?

Outer 1/3rd of vagina


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


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

Semen coagulates due to clotting factors (fibrinogen + semenogelin)


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

Seminal vesicles:
- Fibrinogen
- Semenogelin


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

- Capacitation
- Acrosome reaction


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


Which cells make up the corona radiata?

Follicular cells


What triggers the acrosome reaction?

The passage of sperm through the corona radiata


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


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

~ 15 minutes


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

ZP3 proteins


Name the reaction which prevents polyspermy:

Cortical reaction


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


Approximately how many sperm per ejaculation reach the fertilisation site?

~ 300 sperm


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

~ 299


How long do sperm survive in the female genital tract?

~ 5 days


When is the fertile period of the menstrual cycle?

Day 11-16 of menstrual cycle


Define syngamy:

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


How can polyploidy occur?

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