Placenta Flashcards
Remodelling of spiral arteries
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
Establishment of maternal circulation
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
Integrin switch
Extravillous cytotrophoblasts invade deep in to endometrium
During invasion alpha 6 beta 4 switched off by attachment
Cytotrophoblasts switch it back on
Primary villi
Columns of cytotrophoblasts covered in synctium which extend in to lacunae
Secondary villi
Invasion of extra embryonic mesoderm in to primary villi
Contains haematopoetic stem cells
Tertiary villi
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
Chorionic villi
New vascular beds join large vessels in connecting stalk
Chorion frondosum-> placenta proper-> embryonic pole
Chorion laeve-> smooth chorion-> some villi form then regress
Functions of placenta
Essential nutrient transport O2 in CO2 out, acts as lungs Protects from infection Endocrine organ Helps produce amniotic fluid Maintains maternal recognition of placenta
Simple diffusion
Blood gases Na, electrolytes Urea Fatty acids Non conjugated steroids Bilirubin
Active transport
Hexose sugars Amino acids Water soluble vitamins Nucleotides Cholesterol Calcium Glucose
Receptor mediated endocytosis
Maternal IgG via Fc receptor
Iron via transferrin receptor
Development of placenta in second trimester
Arborization of chorionic villi
Formation of stem and intermediate villi (small branches)
Vessel identity and vascular pruning
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
Development of placenta, third trimester
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
Maternal fetal barrier
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
Efficient exchange, surface area
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
Efficient maternal fetal transport, diffusion distance
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
Placental insufficiency, pre eclampsia
Reduced invasion of spiral arteries
Decreased maternal blood flow
Placental insufficiency, pre eclampsia with intro uterine growth restriction
Increased fetal vascular resistance
Abnormal umbilical artery
Reduced aminogenesis, reduced villus branching, reduced microvilli
Small baby
Diabetes
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
Amniotic fluid
8 weeks-> 15ml
20 weeks-> 450ml
Fetal kidneys main source
Oligohydroaminos-> insufficient amniotic fluid-> renal angensis
Polyhydroaminos-> excessive fluid-> no swallow
Used for diagnostics
