Placenta Flashcards
What is pre-eclampsia?
A hypertensive disorder affecting only human pregnancies.
Why is pregnancy history important in evaluating risk of CVD?
- Pre-eclampsia ~20 weeks inc. chance of death by cardiovascular complications
What are the five functions of the placenta?
- Self maintenance/renewal
- Exchange/transport/transfer
- Separation
- Protection from maternal infections
- Protection from maternal immune system
___% of conceptions are lost
70
The villous _____ is a trophoblast is a trophoblast progenitor cell type found mainly in the first trimester underlying the ______
Cytotrophoblast
Syncitiotrophoblast
How is the syncitiotrophoblast formed?
Fusion of the villous cytotrophoblast
What is the extravillous cytotrophoblast?
Differentiated cells that have migrated out of the villous placenta towards the maternal tissues
What are the components of the chorion?
- Extraembryonic mesoderm
- Cytotrophoblast
- Syncytiotrophoblast
What changes occur in the lacunar period of placental development?
- Lacunae formation
- Trophectoderm protrusions extend into lacunae forming trabeculae
What changes occur in the villous period of placental development?
- Primitive syncytium disappears
- Primary villi formed (proliferation and invasion by cytotrophoblasts)
- Lacunar system forms intervillous space
Around what day do secondary villi form in the placenta?
Day 14
Tertiary villi are formed in around days ____
18-20
What are the cell types present in a secondary villus?
- Syncitiotrophoblast
- Cytotrophoblast
- Extraembryonic mesoderm
The intervillous space is the area between the ____ and the _____ of the placenta.
Chorionic plate
Decidua basalis
Conception happens around day ___ of the cycle
14
What is the chorion laeve?
Smooth chorion formed by regression of villi that lie to the sides and towards the uterine lumen
What is the chorion frondosum?
Definitive placenta formed by villi at the base of the implantation site
What is the difference between floating and anchoring villi?
- Floating villi do not have contact with maternal tissues but are suspended in intervillous space
- Anchoring villi attach placenta to uterus
Spiral arteries do not empty directly into the uterine cavity, they are connected by capillaries to _____.
Draining veins
Around mid-gestation spiral arteries are lined by ______
Endovascular trophoblasts
Which inadequate physiological changes may cause placental malperfusion?
- Inadequate depth of trophoblast invasion
- Reduced number of vessels transformed
Small for Gestational Age babies are more likely to be born ____ or ____
Prematurely or still born
When does plugging of the spiral arteries occur?
Prior to mid-gestation
What is histiotrophic nutrition?
Nourishment of the foetus by glandular ‘milk’ during the first trimester
What is a missed miscarriage?
When a woman give signs that she is likely to have an impending miscarriage, but the condition resolves
Plugs in spiral arteries also stop _____ to prevent placental damage)
Pulsatile flow (of maternal blood)
What is a common finding in women with missed miscarriage?
Increased blood flow to the placenta (at weeks 7-9 or 10-11)
What structural changes occur in the placenta with gestational age?
- Early pregnancy
- Second trimester
- Third trimester
- Villi
- Size
- Early pregnancy: stroma more cellular and more vascularised
- Second trimester: villous cytotrophoblast thins down
- Third trimester: villous cytotrophoblast is sparse
- Villi: branching increases
- Size: increases
What are the three anatomical components of the decidua?
- Decidua basalis
- Decidua capsularis
- Decidua parietalis
The amnion is a vascular/avascular membrane that covers the _____
Avascular
Back of placenta and umbilical cord
The umbilical cord is formed from the ___ and ____
Yolk sac and allantois
Wharton’s jelly is a network of contractile ______ interspersed with _____
Myofibroblasts
Mucopolysaccharides
What is the difference between a false and true knot?
False knot = varicosity/ballooning of vessel
True knot = occlusion of vessels
What is a nuchal cord?
When the umbilical cord becomes wrapped around the foetal neck 360 degrees
When are umbilical cord knots pathologic?
When Wharton’s jelly is not functioning properly
How is the placenta adapted to maximise surface area for exchange?
- Villous structure tortuous with a large SA
- Syncytiotrophoblast has a microvillous surface
- Third trimester most villi are small tertiary villi
- Third trimester most foetal capillaries closely apposed to syncytiotrophoblast
Foetal blood has a greater affinity for ____ due to Hbf (foetal haemoglobin)
Oxygen
(Bohr Effect)
Foetal metabolites picked up by maternal blood cause pH to ____ therefore ____ affinity for oxygen
Lower
Decrease
(Haldane effect)
Loss of oxygen from maternal blood causes ____ capacity for CO2
Increased
What are the five functions of amniotic fluid?
- Buoyant medium for symmetrical growth
- Cushion for embryo/foetus
- Prevent adhesions of foetus with membranes
- Foetal movement -> muscle development
- Development of respiratory and GI tracts
Amniotic fluid is initially an ____ of ____ but then becomes predominantly ____
Ultrafiltrate of maternal plasma
Foetal urine
Fluid leaves amniotic cavity mainly by ____ (500-1000mls/day)
Foetal swallowing
Fluid can move across foetal skin (prior to keratinisation at ____ weeks)
24
What is polyhydraminos?
Excessive amniotic fluid possibly due to loss of swallowing (found in many cases of diabetic pregnancy)
What is oligohydraminos?
Lack of amniotic fluid (potentially due to kidney problems)
Amniocentesis usually occurs at ___ weeks gestation whereas CVS usually occurs at ___ weeks
14-16
10
After breaking off the placenta, where to syncytiotrophoblasts tend to deposit?
Lungs
What is cell-free foetal DNA?
A short piece of DNA that comes from the trophoblast
The placenta prevents the transmission of which infections?
- Hepatitis B
- Rabies
- Measles
- Malaria
What preventative measure is taken with babies that have mothers who are Hep B positive?
- Administered antiglobulin
- Hep B can be transmitted intrapartum
The placenta permits transmission of which infections?
- HIV
- CMV
- Smallpox and other related viruses
- Rubella
- Toxoplasmosis
What is the critical period of organogenesis?
20-70 days after last menstrual period
What consequence can thalidomide have in pregnancy?
Limb reduction defects
What consequence can diethylstilbestrol have in pregnancy?
Clear cell adenocarcinoma in vagina or cervix of adults after in utero exposure
What consequence can ethanol have in pregnancy?
Foetal alcohol syndrome
What consequence can recreational drugs have in pregnancy?
Intrauterine growth restriction and developmental delay
In pregnancy warfarin is swapped to ____
Aspirin
What is betamethasone?
A glucocorticoid given to prevent respiratory distress syndrome
