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Reproductive System > 14) Coitus and Fertilisation > Flashcards

14) Coitus and Fertilisation Flashcards

1
Q

What is coitus?

A

Act of sexual intercourse resulting in deposition of sperms in vagina

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2
Q

What is the effect of oestrogen on Leydig cells?

A

Increase sperm viability

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3
Q

Describe the change to the sperm’s head as it matures:

A

Nuclear condensation so head gets smaller

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4
Q

Describe the function of the acrosome:

A

Hydrolytic enzymes for penetration of ovum

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5
Q

Where are mitochondria found in sperm?

A

Around contractile filament in midpiece

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6
Q

What causes the loss of cytoplasm and organelles from sperm?

A

Testosterone

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7
Q

Describe the process by which sperm leave the epididymis:

A

Sexual arousal -> contraction of epididymal wall muscles -> expels sperm into vas

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8
Q

What happens if sperm aren’t expelled by epididymis?

A

Phagocytosed by epididymal epithelial cells

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9
Q

What are the phases of coitus?

A

Excitement
Plateau
Orgasmic
Resolution

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10
Q

What are the differences between male and female coital phases?

A

Men have refractory period after first orgasm where second is unlikely
Females have no refractory period

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11
Q

Describe the nervous changes in the male excitement phase:

A

Sensory and psychological stimulation -> limbic system

Activation of sacral parasympathetic and inhibition of sympathetic

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12
Q

Describe the process of arteriolar vasodilation in corpora cavernosa:

A

Ach acts on M3 receptors in endothelium -> rise in Ca2+ -> eNOS -> NO production -> vasodilation

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13
Q

What changes occur to male genitalia in excitement phase?

A

Erection of penis
Testes elevate and engorge
Scrotal skin thickens and tenses

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14
Q

What reflex is stimulated in the male plateau phase?

A

Sacrospinous reflex

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15
Q

How is blood kept in the penis during the plateau stage of coitus?

A

Contraction of ischiocavernosus (impedes venous return) causing venous engorgement

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16
Q

What glands are stimulated in the male plateau phase of coitus? What is their function?

A

Bulbourethral glands

Lubricate distal urethra and neutralise acidic urine

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17
Q

What two stages can the male orgasmic phase of coitus be split into?

A

Emission

Ejaculation

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18
Q

What reflex is stimulated in the emission stage of male orgasmic phase?

A

Thoracolumbar sympathetic reflex

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19
Q

What structures contract in the emission stage?

A

SM in ductus deferens, seminal vesicles and prostate

Internal and external urethral sphincters

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20
Q

Describe the ejaculation stage in male:

A

Filling of internal urethra stimulates pudendal nerve -> genital organs, ischiocavernosus and bulbocavernosus contraction -> expulsion of sperm

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21
Q

What occurs in the male resolution phase?

A

Sympathetics causes contraction of arteriolar SM in corpora cavernosa
Increased venous return causing flaccidity
Refractory period

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22
Q

Describe some of the changes in the female excitement phase:

A

Vaginal lubrication due to increased blood flow
Clitoris engorge with blood
Uterus elevates
Inner 2/3rds of vagina lengthens and expands

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23
Q

Describe some of the changes in the female plateau phase:

A

Labia minora deepens in colour

Bartholin’s gland secretion lubricates vestibule

24
Q

What structures contract in the female orgasm phase?

A

Lower 1/3rd of vagina rhythmically 3-15 times

Uterus and anal sphincter

25
Q

Describe some of the changes in the female resolution phase:

A

Clitoris descends and engorgement subsides
Labia returns to unaroused size and colour
Uterus descend, vagina shortens and narrows

26
Q

Describe the changes to the breast in the female excitement phase:

A

Breast size increases, nipples erect

27
Q

Describe the changes to the breast in the female plateau and orgasm phases:

A

Areola size increase, sex flush

28
Q

Describe the changes to the breast in the female resolution phase:

A

Decrease size and areola decreases in size

29
Q

What is the G spot?

A

Area of sensitivity located along anterior wall of vagina

30
Q

What changes occur to the female sexual response during ageing?

A

Reduced desire, rapid resolution
Reduced lubrication
Vagina loses elasticity

31
Q

What are some examples of changes to desire that cause sexual dysfunction?

A

Hypoactive or aversion (fear of sex)
Hyperactive
Kluver-Bacy syndrome

32
Q

What is Kluver-Bacy syndrome?

A

Bilateral medial temporal lobe lesions causing hyperphagia, hypersexuality, hyperorality

33
Q

What are some examples of changes to arousal that cause male sexual dysfunction?

A

Psychological
Tears in fibrous tissue of copora cavernosa
Vascular
Drugs (alcohol)

34
Q

What is an examples of a change to arousal that causes female sexual dysfunction?

A

Lack of lubrication

35
Q

Describe the mechanism of Viagra:

A

Inhibits cGMP breakdown in corpus cavernosum -> increased NO -> vasodilation -> erection

36
Q

What is normal volume of ejaculate volume?

A

2-4 ml

37
Q

What is a normal sperm count?

A

20-200x10^6 sperm per ml

38
Q

Describe the route of sperm to fallopian tubes:

A

Oxytocin stimulates uterine contractions that move sperm into fallopian tubes

39
Q

What happens to cervix after ovulation and why?

A

Thick, sticky plug to prevent bacteria entering uterine cavity

40
Q

What cytoplasmic maturation occurs to oocyte before ovulation?

A

MItochondria disperse
ER forms cortical granules round periphery
Lipid droplets provide energy

41
Q

How long can sperm survive?

A

5 days

42
Q

How long can oocyte survive?

A

6-24 hours

43
Q

What must sperm penetrate to fertilise oocyte?

A

Corona radiata and zona pellucida

44
Q

What is capacitation?

A

Removal of protein coat, exposing acrosomal enzymes

Tail movement changes to whip like action

45
Q

What protein do sperm bind to on zona pellucida?

Upon binding what happens?

A

ZP3

Influx of Ca2+ and acrosomal enzymes begin to digest ZP

46
Q

What are the two regions of oocyte plasma membrane?

A

Membrane that overlies metaphase chromosomes (no microvilli)

Remainder which has microvilli and is where sperm bind

47
Q

What is the fast block to polyspermy?

A

When sperm enters, Na+ channels open to cause wave of depolarisation across cytoplasm and stops further entry

48
Q

What is the slow block to polyspermy?

A

Ca2+ released from ER induces local exocytosis of cortical granules and response is amplified to form wave of exocytosis and prevent further entry

49
Q

What is syngamy?

A

Union of male and female pronuclei to form diploid zygote

50
Q

What can cause polyploidy?

A

Entry of more than one sperm

Failure of extrusion of second polar body

51
Q

What causes monozygotic twins?

A

In cleavage, totipotent cells become divided into 2 separate independent cell masses

52
Q

What causes dizygotic twins?

A

2 eggs ovulate and 2 eggs fertilised

53
Q

Why is cleavage important?

A

Generate a large number of cells form differentiation and gastrulation
Increase nuclear/cytoplasmic ratio

54
Q

What can cause ectopic pregnancy?

A

Failure of transport of morula into uterus

Implantation in incorrect position

55
Q

Where does hatching occur and why?

A

Occurs opposite inner cells mass to minimise risk of enzymatic damage to embryo

Reproductive System (24 decks)

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