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GGE > Gametes - Fertilisation > Flashcards

Gametes - Fertilisation Flashcards

1
Q

Overview of sperm penetration of the egg

A
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2
Q

MOA of erection

A

PS reflex - Arterioles dilate & SM relaxes via NO

Penis is engorged with blood

Expansion compresses the veins, slowing blood leaving the penis

Reflex is intitiated by a sensory stimuli

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3
Q

What sort of drugs may cause erectile dysfunction

A

Anti-cholinergic drugs

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4
Q

Erectile dysfunction and T2D

A

Hyperglycaemia - damages autonomic nerves

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5
Q

MOA of ejaculation

A

Spinal reflex is initiated (lack of muscle in penis shaft)

Sympathetic discharge to genital organs

Reproductive ducts/accessory glands contract peristaltically, discharging their contents into the urethra

Bulbocavernous muscle at the base of the penis experiences a rapid series of contractions, propelling semen from the urethra

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6
Q

How does viagra cause penile erection

A

ACh increases NO, increasing conc of cGMP

cGMP causes SM relaxation

Relaxation of arterioles leads to increased blood flow to penis

normally cGMP is degraded by phosphodiesterase 5, terminating its action

Viagra hence inhibits the PDE5 => decreased cGMP breakdown

Prolonged arteriolar dilation

Prolonged erection

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7
Q

How to know th effectiveness of a vasectomy

A

2 -ve samples, 1 month apart

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8
Q

Content of semen

A

Prostatic fluid - 30%

Epididymal fluid - 50%

Seminal vesicle fluid

CELLS

spermatozoa

Leukocytes

bacteria

epithelial cells

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9
Q

Reference ranges for semen

A
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10
Q

Function of fructose in seminal vesicle

A

Marker for seminal vesicle function - energy source

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11
Q

Function of prostaglandins in semen (from seminal vesicle)

A

Sperm motility

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12
Q

Function of proteins in semen (from seminal vesicle)

A

Coagulate semen

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13
Q

Function of alpha glucosidase (from epididymis)

A

Marker for epididymal function

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14
Q

Function of CD52 (from epididymis)

A

Seminal glycoprotein that is incorporated into sperm membrane

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15
Q

Substances present in semen that are produced by the seminal vesicles

A

Fructose

Prostaglandins

Proteins

(Also makes semen alkaline)

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16
Q

Substances present in semen that are produced by the epididymis

A

alpha glucosidase

CD52

Glycogen

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17
Q

Name the prostate secretions and their functions

A

Calcium - contractility of sperm & fertility

Zinc - anti-bacterial (marker for prostate function)

Citric acid - present in high conc, hence reduced levels are a biomarker in prostate cancer

Acid phosphatase - marker for prostatic function

Albumin

Prostatic Specific Antigen (PSA) - a protein produced by the epithelial cells of the prostate that is a biomarker for porstate cancer (> 4ng/ml)

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18
Q

Name 2 markers for prostatic function

A

Zinc

Acid phosphatase

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19
Q

Biomarkers for prostate cancer

A

Citric acid

PSA

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20
Q

At what pH do sperm die

A

6.9

Normal range is 7.2-8.4

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21
Q

Variation in speed of motility of sperm

A

Rapid progressive - >25 um/s

Slow progressive - 5-25 um/s

Non progressive - <5um/s

IMMOTILE - no flagellar movement

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22
Q

Aspermia

A

No semen ejaculated

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23
Q

Haematospermia

A

Blood present in semen

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24
Q

Leucocytospermia

A

WBCs present in semen

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25
Q

Azospermia

A

No spermatozoa found in semen

26
Q

Normospermia

A

Normal semen parameters

27
Q

Oligospermia

A

Low sperm conc

28
Q

Asthenospermia

A

Poor motility and/or forward progression

29
Q

Teratospermia

A

Reduced % of morphologically normal sperm

30
Q

Necrospermia

A

No live sperm in semen

31
Q

How would you describe sperm produced in the ST

A

Morphologically mature, functionally immature

Non-motile and not capable of fertilisation

32
Q

Define capacitation of sperm

A

The biochemical changes that happen within sperm allowing for full functional maturity

Takes place as the sperm travels within the uterine and oviductal fluid

Removal of glycoprotein covering the head of sperm

33
Q

What are the sperm cell membrane changes with capacitation

A
  1. Removal of cholesterol - increased fluidity of membrane
  2. Loss of glycoproteins - expose egg binding protein
  3. Fluctuations in Ca2+ - protein phosphorylation via cAMP (ABSOLUTE REQUIREMENT)
34
Q

Cellular processes that lead to capacitation

A
35
Q

Consequences of changes in sperm due to capacitation (due to increase in Ca2+)

A

Increased metabolism = fructose for energy

Flagellum increases rate of beating - increased sperm motility

Activation of acrosomal enzymes - pro-acrosin → acrosin

36
Q

Site of fertilisation

A

Tubal ampulla

Sperm are deposited in vagina and travel to tubal ampulla by flagellar movement

37
Q

What factors increase uterine contractility

A

Ovarian steroids influence sperm transport

  • High oestrogen of late follicular phase makes the cervical mucus alkaline and less viscous
  • PGs in seminal fluid
  • Oxytocin - localised
38
Q

Transport of sperm and egg in female reproductive tract

A
39
Q

Structure of ovulated oocyte

A
40
Q

Where is the zona pellucida first detected

Composition

When is the ZP no longer present

A
  • First detected in primary follicle
  • Matrix composed of sulfated glycoproteins
  • CHO residues (sperm receptors?)
  • Increase in width with development of oocyte
  • ZP stays until blastocyst is formed @ day 7 - embryo hatches out of ZP and implants on main body of uterine wall
41
Q

Function of zona pellucida

A

Species specific barrier

Removal of ZP allows cross fertilisation to occur with relative ease

42
Q

What does ZP3 do

A

Mediates sperm specific egg binding

43
Q

Function of ZP2

A

Mediates subsequent sperm binding

44
Q

Function of ZP1

A

Cross links ZP2 and ZP3

Protein meshwork formed

Not essential for fertilisation

NB -structural integrity of ZP

45
Q

What happens in the absence of ZP1

A

Premature hatching of embryos

46
Q

Overview of ZP1, ZP2 and ZP3 functions

A
47
Q

Sperm egg binding overview

A
48
Q

What is the sperm receptor of the egg

A

Galactosyl Transferase (Galtase)

49
Q

What are th egg receptors

A

O-linked oligosaccharide residues of ZP3

50
Q

What rxns does egg sperm binding intitiate

A

Acrosomal rxn

Sperm & cortical rxn

51
Q

ZP3 and the acrosome rxn

A
52
Q

What is the mediator of the acrosomal rxn

A

Galtase

53
Q

Overview of acrosomal rxn

A
54
Q

Describe the cortical rxn

A
  • Cortical granules are membrane bound vesicles just beneath the egg cell membrane
  • Exocytosis at fertilisation - granule enzymes released - digest proteins of ZP
  • Prevents poly spermy
55
Q

Overview of cortical rxn

A

Cortical granules = enzymes that digest ZP and prevent entry of 2 male pronuclei

56
Q

When is there decreased effective block to polyspermy

A

Age of ova

  • Time of insemination relative to ovulation
  • Aged oocyte increases chance of polyspermy

Heating of ova

  • Increased metabolism and lifespan of egg
  • Fever or environmental effect on body temp

Excessive sperm numbers

  • at site of fertilisation
  • Sperm barriers reduce numbers - cervix, uterus, utero-tubular junction
57
Q

What is the window of viability of an egg

A

24 hours

58
Q

Consequences of triploidy

A

3 pronuclei within one zygote

In vivo, such embryos almost always abort spontaneously

59
Q

Overview of egg activation

A
60
Q

Describe pronuclei fusion

A
  • Haploid sperm enters the egg
  • Becomes the sperm pronucleus
  • Sperm pronucleus swells and migrates towards the egg pronucleus
  • The pronuclear envelopes vesiculate (nuclear membranes break up to form a circle of small vesicles) and surround the chromatin of each nucleus
  • Chromatin from each pronucleus intermixes, forming the diploid zygote nucleus
  • Nuclear envelope reforms around the zygote nucleus & embryonic development begins
61
Q

Fusion of nuclei

A
62
Q

Early embryonic development

A

GGE (33 decks)

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