Placenta

Question 0

Remodelling of spiral arteries

Answer 0

Extravillous cytotrophoblasts invade maternal spiral arteries
Replace endothelium and smooth muscle
Ensure arteries remain open as no longer under maternal control
High flow low resistance
Not remodelled properly in pre eclampsia

Question 1

Establishment of maternal circulation

Answer 1

Synctiotrophoblast invade maternal sinusoids and keep moving up to spiral arteries
Lacunae become continuous with sinusoids and fill with maternal blood
Blood drains passively in to decidual veins

Question 2

Integrin switch

Answer 2

Extravillous cytotrophoblasts invade deep in to endometrium
During invasion alpha 6 beta 4 switched off by attachment
Cytotrophoblasts switch it back on

Question 3

Primary villi

Answer 3

Columns of cytotrophoblasts covered in synctium which extend in to lacunae

Question 4

Secondary villi

Answer 4

Invasion of extra embryonic mesoderm in to primary villi

Contains haematopoetic stem cells

Question 5

Tertiary villi

Answer 5

Haematopoetic stem cells from new blood vessels which connect to primitive capillary plexus-> chorionic vessels-> unbilical stalk-> fetal vessels
Fetal blood now in contact with maternal-> haematotrophic nutrition

Question 6

Chorionic villi

Answer 6

New vascular beds join large vessels in connecting stalk
Chorion frondosum-> placenta proper-> embryonic pole
Chorion laeve-> smooth chorion-> some villi form then regress

Question 7

Functions of placenta

Answer 7

Essential nutrient transport 
O2 in CO2 out, acts as lungs
Protects from infection 
Endocrine organ
Helps produce amniotic fluid
Maintains maternal recognition of placenta

Question 8

Simple diffusion

Answer 8

Blood gases
Na, electrolytes
Urea
Fatty acids
Non conjugated steroids
Bilirubin

Question 9

Active transport

Answer 9

Hexose sugars
Amino acids
Water soluble vitamins 
Nucleotides
Cholesterol
Calcium 
Glucose

Question 10

Receptor mediated endocytosis

Answer 10

Maternal IgG via Fc receptor

Iron via transferrin receptor

Question 11

Development of placenta in second trimester

Answer 11

Arborization of chorionic villi

Formation of stem and intermediate villi (small branches)

Question 12

Vessel identity and vascular pruning

Answer 12

Vascular endothelial growth factor-> birth, migration and proliferation of endothelial cells-> tube formation
Angiopoietin 1-> recruit and interact with peri endothelial cells-> maintain vessel integrity
Smooth muscle and pericyte wrapping of endothelial cells

Question 13

Development of placenta, third trimester

Answer 13

Terminal villus capillaries and terminal villi develope
Second burst of angiogenesis in response to fetal growth
Elongates existing blood vessels-> coil and bulge in to surrounding trophoblast
Cytotrophoblast regresses
Only synctium and cap endothelium between fetal and maternal blood

Question 14

Maternal fetal barrier

Answer 14

Syncytial layer-> no cell borders-> nutrients have to go through synctium
Continuous endothelium->restrictive cellular tight and adheren junctions-> most nutrients have to go through endothelial cells
Molecules >65kPa can’t cross paracellular cleft, have to go through endothelial cells
Phosphylation of junctions can occur in an inflammatory response-> loss of barrier functions
Macrophages in stroma-> hofbauer cells

Question 15

Efficient exchange, surface area

Answer 15

Extensive branching of chorionic villi
Extensive vascular network
Highly coiled terminal villus capillaries
Microvilli on synctiotrophoblast
Increased endoplasmic reticulum and vesicular system for transplacental transport

Question 16

Efficient maternal fetal transport, diffusion distance

Answer 16

Fetal capillaries dilated and close to synctium
No cytotrophoblasts
Elongation and thinning of syncytiotrophoblast cytoplasm
Extrusion of excess accumulation of nuclei into maternal blood-> syncytial knots

Question 17

Placental insufficiency, pre eclampsia

Answer 17

Reduced invasion of spiral arteries

Decreased maternal blood flow

Question 18

Placental insufficiency, pre eclampsia with intro uterine growth restriction

Answer 18

Increased fetal vascular resistance
Abnormal umbilical artery
Reduced aminogenesis, reduced villus branching, reduced microvilli
Small baby

Question 19

Diabetes

Answer 19

Over nutrition
Increased placental angiogenesis and villus growth
Basement membrane thickening-> abnormal microvilli
Leaky blood vessels-> impaired placental barrier
Maternal hyper-> dysregulation of glucose transporters and insulin receptors
Fetal hyperglycaemia and hyperinsulinaemia
Large baby
Risk of post natal hypo

Question 20

Amniotic fluid

Answer 20

8 weeks-> 15ml
20 weeks-> 450ml
Fetal kidneys main source
Oligohydroaminos-> insufficient amniotic fluid-> renal angensis
Polyhydroaminos-> excessive fluid-> no swallow
Used for diagnostics