Implantation and placental function Flashcards
Where does fertilisation occur
occurs in oviducts
Where does fertilised egg move to
Lumen of uterus
What is placentation recognition of pregnancy
Establishing physical and nutritional contract
Required for supply of nutrients leading to growth
What is maternal recognition of pregnany
Signals presnece to mother and prevents luteal regession
What is the first differentiation step
6 days after fertilisation, cells of blastocyst differntaited into trophectoderm
Trophhectoderm will become placenta
Inner mass becomes feotus
Define apposition
Positioning of blastocyst within uterine cavity
Define adhesion
Cells of trophoblast fix to maternal tissue and each other
Achieved via group of cell adhesion molecules (laminin, fibronectin)
What happens during differentiation
Trophectoderm differentiates into cytotrophoblast and syncytiotrophoblast
What is cytotrophoblast
Single nucleus which rapidly divides in vivo
What syncytiotrophoblasts
Derived from fused cytotrophoblast. Multinucleated
Describe placental formation
trophoblasts form villous structures
cytotrophoblasts break through trophoblast shell
invade through decidual tissue
triophoblast reach maternal spinal arteries
spiral arteries widened allowing greater flow of maternal drug
What is the barrier between maternal and foetal circulation
Villous trophoblast
What regulates invasion
Embryo exists in hypoxic environement
Oxygen gradient between mam and feotus regulates invasion
What happens to oocyte during fertilisation
Corpus luteum doesn’t degenerate
Progesterone doesn’t degenerate
Endometrium is maintained
When can hCG be detected
4 weeks
When does hCG surge
week 10
What happens as hCG falls and progesterone and oestrogen increases
Latter two hormones are unstable
What does the foetal surface of the placenta
Smooth covered in amnion
What does maternal surface of the placenta
Dull, grey divided into contledons
What does smaller branches of imbilical artery supply?
Chorionic villi
What is main site of exchange in placenta
Capillary networks
What is transported in
a) umbilical vein
b) umbilical artery
a) away from maternal side to baby. Oxygenated blood and nutrients
b) away from baby carries waste and deoxygenated blood
How many spiral arteries are there in maternal circulation
80-100
Functions of placenta
nutrients
prevents luteal regression
site of exchange of gases
nutrient exchange and waste exchange
How are water and electrolytes transported across placenta
Simple diffusion
How is glucose transported
Facilitated via GLUTS
How are amino acids transported across placenta
Active transport via transporter protein
Large proteins and cells transported across placenta?
Pinocytosis
What does placenta allow through
igG antibodies hormones antibiotics sedatives some viruses
Can foetus cells cross placenta
Y
What hormones does placenta secrete?
hCG, hPL, oestrogen, progesterone, human placental growth hormone, insulin growth factors, relaxin
What 3 factors help prevent rejection of feotus by maternal immune system?
- Trophoblast cells express HLA G which is not recognised by host immune cells
- Ilfiltrating leucocytes release IL-2 which regulates immune system
- Decidual reaction cells become swollen and tightly packed forming physical barrier
