Placenta Fetal Surface

Placenta Maternal Surface

Development Placenta is developed from two sources Fetal Chorion Frondosum Maternal Decidua basalis Stem villi 13th day Arterio-Capillary-venous system completed in each villus on 21st day

Fetal haemodynamics Foetal blood flow throuhg the placenta 400 ml per minute Pressure in the umbillical artery 60 mm Hg Pressure in the umbilical vein 10 mm Hg Foetal capillary pressure in villi 20 – 40 mmHg O2 Saturation Umb artery 50 –60 % Umb vein 70 – 80% PO2 20 – 25 mm Hg 30 – 40 mmHg

Intervillous haemodynamics Blood in the placenta _____________ 500 mls Blood in the intervillous space ______ 150 mls Blood flow in the inter villous space _ 500-600 mls Pressure in the inter villous space During UT contraction ________ 30- 50 mm Hg During UT relaxation _________ 10- 15 mm Hg Pressure in the UT artery _________ 70- 80 mm Hg Pressure in the UT vein________ 08 mm Hg

Spiral Arterioles at the Placental Site

Placental Function Urea, uric acid creatinine By simple diffusion Respiratory Oxygen supply to the fetus is at the rate of 5ml/Kg/min (cord blood flow of 165 – 330 ml/min Excretory Urea, uric acid creatinine By simple diffusion Nutritive function Glucose. Lipids. Amino acids, Water and electrolides, Vitamens

Facilitated diffusion Simple diffusion Water Sodium Potassium Chloride Oxygen,CO2, Facilitated diffusion Glucose Active transport Fatty acids Amino acids Vitamins Calcium, Phosphorus, Iron

Hormonal Barrier function Human Chorionic Somatomammotropin (HSG) Human Chorionic Gonadotrophin (HCG) Human Chorionic Thyrotropin (HCT) Corticotrophin Releasing Hormone (CRH) Oestrogen Progestogens Adrenocorticoids Barrier function Placental membrane in early pregnancy _____ 0.02 mm at term ____ 0.002mm Substances more than 500 Daltons can not cross

Immunological Enzymatic function Fibrinoid coating of trophoblast Specific mucoprotein mucopolysaccharides by Decidua Placental hormones ( HCG,steriods) have weak immunosuppressive property. Nitabuch’ layer between decidua & trophoblast inactivate antigen Enzymatic function Oxytocinase Phpsphplipase A2