Fertilisation and implantation

Question 1

maturation of spermatozoA

Answer 1

100 fold concentration of sperm, oestrogen dependent
completion of sperm modelling
changes in metabolism
acquisiton of forward motion
changes in membrane surface proteins, charge and fluidity
coating of sperm plasma membrane with glycoproteins
dpeends on adequate stimulation of epididymis by androgen

Question 2

what is coitus mediated by

Answer 2

sympatheti
parasympathetic
somatic

Question 3

coitus sympathetic

Answer 3

hypogastric nerve
vascular tone in penile and clitoral arteries
emission of semen in the urethra

Question 4

coitus parasympathetic

Answer 4

pelvic nerve
promotes vasodilation and erection of penile and clitoral tissues, lubrication

Question 5

coitus somatic

Answer 5

pudenal nerve
sensations following stimulation of glans penis/clitoris emisison in internal urethra
reflex rhythmical contractions of muscles during ejaculation

Question 6

where does fertilisation occur

Answer 6

in ampulla of fallopian tubes

Question 7

issues sperm encounters in the vagina

Answer 7

physical loss of sperm form vagina
survival of sperm cells in the vagina

Question 8

adaptations of sperm to prevent loss form vagina

Answer 8

semenogelin 1, 2 and fibronectin
aggregate to form coagulum
forced retention

broken down in 20 mins
via proteolytic cleavage of semenogelins by prostate specific antigen so sperm can regain motility and continue journey

Question 9

vaginal environment

Answer 9

normal vaginal flora prevent colonisation of pathogenic bacteria as lactobacillus produce lactic acid from anaerobic digestion of glycogen
vagna secretes hydrogen perodixde and antimicrobial peptides to exhibit strong adhesion to vaginal epithelium
abundance of immune cells

Question 10

how do the sperm neutralise and overwhelm vaginal defences

Answer 10

neutralisation of acidic vaginal environement by alkaline seminal fluid
attenuation of vaginal immune response by immunosuppressive compounds in the seminal fluid e.g. prostaglandins
large number of sperm ejaculated overwhelms innate immune
sperm deposited near cervical os allowing fast escape though cervix

Question 11

penetrating the cervix

Answer 11

sperm migrate out of seminal plasma and into mucus immediately

Question 12

characterisics of the cervical canal

Answer 12

cervical crypts

Question 13

quality of the cervical mucus

Answer 13

mucins
glycoproteins: long and flexible
aligned by secretory flow in the mucosal grooves
muc5B and muc4: hydrophillic

Question 14

penetrating cervix in follicular phase

Answer 14

oestrogen relxaes muscles of cervix
increases secretion and hydration of cervical mucus
facilitates sperm penetration into the uterus

Question 15

penetrating cervic in the luteal phase

Answer 15

progesterone decreases cervical mucus secretion and hydration level
impermeable to sperm and pathogens
protecting potential fertilised embryo

Question 16

travel through uterus

Answer 16

self propulsion
cilitated endothelial celsl of endometrium create fluid current
oestrogen driven contractions of myometrium towards fundus during follicular phase

Question 17

sperm capacitation

Answer 17

loss of glycoprotein coat
reveals binding sites and receptors, epididymal protease inhibitor which facilitates acrosome reaction and increases sperm receptivity to chemo-attractants
change in the surface membrane properties
loss of membrane cholesterol destabilises the plasma membrane
facilitates the acrosome reaction
increase in intracellular Ca2+
activation of protein kinase A needed for acrosome reaction

Question 18

how does the sperm enter the right fallopian tube

Answer 18

labelled microspheres show to be preferentially transported to fallopian tube in late follicular phase
dominant follicel secrete progesterone, disperses to ipsilateral fallopian tube, relaxation of musces at utero-tubual junction
ipsilateral to dominant follicle allows controlled sperm penetration

Question 19

how do sperm find the oocyte in the fallopian tube

Answer 19

specific receptors on capacitated sperm responding to chemo attractive substances: ANP or progesterone from follicualr fluid or cumulus oophorus or odorant recpetors similar to those in the olfactory epithelium

activation of adenylate kinase, cAMP mediated rise in intracellular Ca2+ for chemotaxis and chemokinesis

Question 20

ovulated oocyte pathway

Answer 20

moved from the surface of the ovary by fimbrated ostium
passes into the ampulla of fallopian tube adhering epithelium via cumulus cells
contractions of smooth muscle and oviductal cilia move cumulus oocyte to ampullary isthmic junction
intersittial celsl of Cajal

Question 21

fetilisation

Answer 21

Sperm hyaluronidases dissolve cumulus cell extracellular matrix
Sperm cell reaches the zona pellucida (ZP)
Short-lived binding of capacitated sperm to ZP3/ZP4 complex
Increased intracellular Ca2+ in sperm cell via activation GCPR
Exocytosis of acrosome enzymes (acrosome reaction)
“drill” into ZP
Acrosin
Hyaluronidases
Hexosaminidases

Question 22

use other flashcards

Answer 22

for fertilisatipn and cleavage

Question 23

what do the trophoblast outer rim form

Answer 23

trophectoderm
extra embryonic support tissue precursor

Question 24

what does the uterus consist of

Answer 24

An outer serous peritoneal layer
A thick layer of smooth muscles (myometrium) with spontaneous peristaltic activity
An internal endometrium consisting of a stromal matrix overlaid by a simple columnar epithelium containing ciliated and glandular cells

changes during hormone cycles

Question 25

maternal recognition of conceptus

Answer 25

trophoblasts secrete HCG prevents luteal regresison by binding to LH receptors on luteal cells, stimulates estrogen and progesteron secretion preventing endometrium shedding prepares uterus triggers deciduation of the endometrial lining to make the endometrium receptive to implantation

Question 26

deciduation

Answer 26

differentiation from elongated fibroblast like endometrial stromal cells into more rounded and high specialised secretory epithelioid cell type

Question 27

blastocyst in implantation

Answer 27

Oxygen and metabolic substrates from uterine secretions Continued growth and survival Trophoblast cells use specific transport mechanisms to accumulate ions and organic molecules Oxygen and carbon dioxide exchange through diffusion

Question 28

zona pellcuida in implantation

Answer 28

Zona Pellucida Prevents cells of pre-compaction conceptus from separating (monozygous twins) Prevents genetically distinct conceptuses from forming a chimera Prevents the blastocyst from implanting in an inappropriate location in the uterus

Question 29

mucins in implantation

Answer 29

Mucins (MUC-1) in the endometrial glycocalyx prevents binding of the conceptus and guides it to a receptive area

Question 30

phases of implantation

Answer 30

hatching apposition adhesion invasion

Question 31

hatching phase

Answer 31

ZP breaks down by lytic enzymes in glandualar secretions hatching of the conceptus by contraction/expansion of conceptus allowing rapid size increase

Question 32

apposition phase

Answer 32

paracrine signalling controlled unstable interaction between blastocyst and uterine epithelium tropholbasts express L-selectin to allow blastocyst to roll across surface of uterus until it finds receptive area of uterine epithelium that express sulphated oligosaccharide ligand leukaemia inhibitory factor: oestrogen induced cytokine that promotes luminal endothelial receptivity and stromal cell decidualisation

Question 33

adhesion

Answer 33

receptive areas of endometrium are the pinopodes EGF receptors expressed by trophoblast luminal cells express Hb-EGF which bnnds EGFR signals from blastocyst upreg cell adesion such as integrins which mediate firm adhesion of blastocyst to endometrial linng

Question 34

invasion

Answer 34

adhesion triggers local singlaling events: proliferate and differentiate into cytotrophoblast and syncytiotrophoblast St secrete TNFa which reduces intracellular adesion to allow ST invasion produce lytic enzymes to invade stromal celsl stromal reaction: oedema, increased sprouting and capillary growth, decidualisation then secondary decidualisation reaction and endometrial component of the placenta is prepared breakdown of decidual cells prodive nutrition ST projections will degrade maternal vessels casuing maternal blood to floow ST lacunae allowing direct uptake of nutrients cytotrophoblastic cells form finger like projections in the syncytiotrophoblast form foetal blood vessels endometrial epithelium reforms behind

Question 35

implantation window

Answer 35

Days 1-7 luteal phase Endometrium is prereceptive Long apical microvilli High surface charge Thick glycocalyx Days 7-10 receptive phase Transition to receptivity Pinopodes appear Loss of surface negative charge Shortening of microvilli Thinning of mucin coat If no implantation: Refactory phase Resist attachment