Placenta Flashcards
At what day does implantation occur?
7
What are the contents of the umbilical cord?
2 arteries
1 vein
Wharton’s jelly
Amnion cover
What are the fetal membranes?
Chorion
Amnion
Yolk sac
Allantois
Where does early nutrition of the embryo come from?
Simple diffusion through the zona pellucida
Blastocyst fluid and yolk sac
What day does long term nutrition start?
Day 12 placenta takes over nutritional supply
What day does the blastocyst attach and then implant to the endometrium?
Attaches at day 6-7
Implantation at days 12-13
Where is the blastocyst fertilised and then implanted?
Ampulla of the uterine tube
Fundus of the uterus (uterine cavity)
What triggers decidualisation and what day does it occur?
Day 7
Blastocyst implantation on endometrial lining and PROGESTERONE
Uterine cells become decidual cells when they accumulate lipid and glycogen
What changes occur during decidualisation?
Trophoblast differentiates into cut-trophoblast and syncitiotrophoblast
Uterine lining changes epithelium to become decidual cells
What are the 3 decidual layers?
Decidua basalis (maternal placenta) Decidua capsularis (covers blastocyst) Decidua parietalis (covers remainder of uterine cavity)
What condition does ectopic pain mimic?
Appendicitis
What are some ectopic implantation sites?
Anywhere within peritoneal cavity with a blood supply
95% within uterine tubes
What are the functions of the placenta?
Hormones (hCG, progesterone, oestrogen)
Immunity (passive, IgG)
Nutrition (O2, CO2, glucose)
What are lacuna networks, what day do they appear?
Days 10-12
Open spaces in the syncitiotrophoblast (= lacunae that fill with maternal blood)
Adjacent lacunae fuse
Maternal spiral arteries open into them
What vein does maternal blood return in?
Endometrial vein
Outline primary, secondary and tertiary chorionic villi
Cells from cytotrophoblast invade syncitiotrophoblast to form primary chorionic villi
Extraembryonic mesenchyme grows into primary villi to form secondary chorionic villi
Blood vessels develop in the extraembryonic mesoderm providing communication with umbilical artery and vein
At what week is foetal blood present?
By the end of week 3 (once tertiary chorionic villi are formed)
What’s the deal with foetal and maternal circulation and blood flow around the placenta?
Branched chorionic villi bathed in maternal blood of placenta essential for embryonic survival
Foetal and maternal circulations never mix, are just in very close contact
Which zone of the uterus does the placenta sit in?
Junctional zone
What are the components of the foeto-maternal membrane?
Maternal blood -> Syncitiotrophoblast -> Cytotrophoblast -> Foetal capillaries
Why does the placenta thin throughout pregnancy?
Majorly from week 22/38
Majority of cut-trophoblast layer lost
Surface area increases and thins to meet increased metabolic demands of foetus
What are some placental dysfunctions?
Transport unwanted substances/pathogens Implantation site (ectopic/previa) Abruption (revealed, concealed, both) Uncontrolled invasion (accreta/percreta) Inadequate blood flow
What’s accreta and percreta?
When placenta implants at wrong location/too deeply
Can go partly through myometrium (accreta) or all the way through it (percreta)
What’s placenta previa?
Insertion of the placenta low down in the uterine cavity - it covers internal os = patient presents with bleeding
What could result in inadequate blood flow to the placenta?
Pre-eclampsia = failure of normal invasion of trophoblast cells leading to maladaptation of maternal spiral arteries
Impairment: maternal vascular disease, post gestational age
Mechanical: IVC compression
Volume: maternal haemorrhage or hydration
