Women's Health - Physiology of Pregnancy Flashcards
What is fertilisation?
Fusion of haploid sperm and oocyte
Where does fertilisation typically occur?
Ampulla of fallopian tube
What are the 6 stages of fertilisation?
- Capacitation
- Acrosome Reaction
- Adhesion + entry
- Cortical reaction
- Meiosis II
- Syngamy
What is capacitation?
Final stage of sperm maturation ; involves exposure of receptor sites involved in zona pellucida penetration.
What occurs during the acrosome reaction?
Loss of acrosome cap on the head of the sperm cell leads to release of lytic enzymes, which allows the sperm to penetrate the zona pellucida
What happens during adhesion and entry?
Fusion of sperm and egg membranes and the head of the sperm if phagocytosed - it then breaks down to release the sperm nucleus.
What happens during the cortical reaction?
modification of the zona pellucida, induced by
membrane fusion and mediated by cortical granules
What is the purpose of the cortical reaction?
Prevent polyspermy
What completes during meiosis II?
Oocyte completes meiosis II I (which until this point is arrested in
metaphase II) to give the second polar body.
What occurs during syngamy?
Pronuclei replicate DNA
the male and female pronuclei replicate DNA and shed their nuclear
membranes as they move toward one another, before aligning at a common metaphase
plate and undergoing mitosis.
When does implantation of blastocyst into the endometrium occur?
Day 6-7
What is formed during gastrulation?
Trilaminar disc from the primitive streak
What makes up the trilaminar disc?
endoderm
mesoderm
ectoderm
When do organ systems begin to develop?
Week 3-8
What is neurulation?
Development of the neural tube from the ectoderm
When does neurulation occur?
Week 4
At what week is the threshold of viability?
Week 23
What is the main purpose of placental exchange?
Gaseous and nutrition
How does oxygen move from mother to fetus?
Higher affinity of HbF
(oxygen moves readily from maternal to foetal haemoglobin (HbF) due
to HbF’s higher affinity)
How does CO2 move from fetus to mother?
Diffusion down concentration gradient
(CO2 diffuses from foetal to maternal blood down the concentration gradient).
How is glucose transferred to the fetus?
Facilitated diffusion (maternal to foetal circulation)
How do amino acids and free fatty acids cross from mother to foetus?
Active transport
Which hormones are produced/supplied by the placenta?
Human Chorionic Gonadotrophin (hCG)
Human Placental Lactogen (hPL)
Progesterone
Oestrogen
Which cells produced Human Chorionic Gonadotrophin (hCG) ?
Trophoblast cells
Purpose of hCG
maintains the corpus luteum to allow for sufficient progesterone production until
the placenta takes over
What hormone maintains the corpus luteum?
hCG
What does Human Placental Lactogen (hPL) increase?
Fatty acids, insulin
(increases maternal free fatty acid and insulin
levels, as well as inducing maternal insulin resistance.)
What is the effect of progesterone during pregnancy?
Inhibits uterine contractility
Thickens endometrium
Function of Oestrogen
stimulates myometrial growth
oxytocin receptor synthesis
pregnancy-related breast changes
What hormone stimulates myometrial growth?
Oestrogen
When does blastocyst implantation occur?
Day 6-7
What happens immediately after blastocyst implantation?
Trophoblastic invasion into the highly vascular uterine wall.
What invades the uterine wall during implantation?
Trophoblastic cells
What happens by mid-late week 2 (after the trophoblastic cells have invaded the uterine wall)?
trophoblastic cells invade endometrial capillaries and venules and form lacunae,
filled with maternal blood.
What fills the lacunae formed by trophoblastic invasion?
Maternal blood
What are the projections of invading cells called?
Primary villi
What forms within the villi of the placenta?
Foetal vessels
The projections of invading cells are referred to as primary villi - they form
branches which become secondary and tertiary villi.
What are the functional units of the placenta?
Cotyledons
What are cotyledons formed from?
stem villi and collections of their secondary/tertiary villi
What forms the exchange surface between maternal and foetal circulation?
Cotyledons
What forms the umbilical cord?
Amniotic membrane tube
(a tube of amniotic membrane which surrounds the connecting stalk
and vitelline duct)
Which vessels carry deoxygenated blood from the foetus to the mother?
the 2 Umbilical arteries
Which vessel carries oxygenated blood to the foetus?
The umbilical vein
What happens during systole in maternal blood flow?
Flows into intervillous space
(During systole, maternal blood flows out of flaccid invaded spiral arterioles into the intervillous space - it is here
that it contacts the foetal exchange surface of the chorionic plate, before rejoining the maternal circulation via
collecting venules. Maternal blood is supplied by the uterine arteries, branches of the internal iliac arteries.)
Where does maternal blood contact the fetal exchange surface?
Chorionic plate
What supplies maternal blood?
Uterine arteries, branches of the internal iliac arteries.