8.1 The Placenta Flashcards
Describe the process of implantation
Uterine epithelium breached and conceptus implants within the stroma.
What is meant by haemomonochorial?
One layer of cells separating the maternal and fetal blood supply
Why is implantation important?
Establishes an area of exchange
Anchor the placenta
Establish maternal blood flow in the placenta
What is a primary villi?
Early projections of trophoblast
What is a secondary villi?
Invasion of mesenchyme into the core of the villi
What is a tertiary villi?
Invasion of mesenchyme core by fetal vessels
What is an ectopic pregnancy?
Implantation away from the uterine body eg. in the fallopian tubes
What is placenta praevia?
Implantation in the lower uterine segment meaning the growth of the placenta covers the cervical opening. Requires a C-section and can cause haemorrhage
What cells are involved in preparing the uterus for implantation?
Pre-decidual cells
What is decidualisation?
Pre-decidual cells balance the invading force of the trophoblast so the fetus does not invade through the full-thickness of the endometrium
What is special about the arterial supply in the endometrium?
Remodelled to create a low resistance vascular bed
This maintains the high flow required to meet fetal demand especially in late gestation
What is pre-eclampsia?
Endometrial lining not replaced by fetal tissue so there is inadequate modification of the vessel walls
What are the 3 ways of twinning occuring?
2 amniotic sacs, 2 chorionic sacs, 2 placentas
2 amniotic sacs, 1 chorionic sac, 1 placenta
1 amniotic sac, 1 chorionic sac, 1 placenta
Describe the appearance of the 1st trimester placenta
Relatively thick
Complete cytotrophic layer under syncytiotrophoblast
Describe the appearance of the full term trimester placenta
Thin barrier
Increased surface area
No cytotrophoblast layer
What type of blood do the umbilical veins carry?
Oxygenated blood
What type of blood do the umbilical arteries carry?
De-oxygenated blood
What products does the placenta synthesise?
Glycogen, cholesterol, fatty acids
Progesterone, oestrogen
hCG, hCS, hCT, hCC
What is the function of hCG?
Maintains the secretory function of the corpus luteum
What is a molar pregnancy?
No fetal tissue
Only outer cell mass
Lots of hCG produced
What is choriocarcinoma?
Tumour of the chorionic membrane
Why does the placenta release progesterone?
Increase appetite to build up fat stores
What substances move by diffusion across the placenta?
Water, electrolytes, gases, urea
What substances move by facilitated diffusion across the placenta?
Glucose
What substances move by active transport across the placenta?
Amino acids
Iron
Vitamins
What substances move by receptor-mediated transport across the placenta?
IgG
What is a teratogen?
Substance that can move across the placenta but is toxic to the fetus eg. alcohol, thalidomide
What is haemolytic disease?
Rhesus blood group incompatibility of mother and fetus
Mother creates antibodies to the fetus and then gives them to the fetus
Give 2 infections which can be passed on to the fetus
Varicella voster virus
Rubella
