ZOO 3713C Lecture Notes - Lecture 12: Yolk Sac, Esophageal Atresia, Umbilical Cord
Document Summary
Yolk salk hypoblast / extraembryonic mesoderm. Amniotic membrane is two cell layers: 1. As the amnion enlarges it encompasses the embryo on the ventral side, merging around the umbilical cord. Amnion forms the epithelial layer of the umbilical cord. With embryo growth the amnion obliterates the chorionic cavity. Amniotic sac is fluid filled called amniotic fluid: the embryo is bathed in the fluid. Up to week 20 fluid is similar to fetal serum (keratinization) After 20 weeks contribution from urine, maternal serum filtered thru endothelium of nearby vessels, filtration from fetal vessels in cord. Near birth can contain fetal feces called meconium: amnionic fluid (500-1000 ml) exchanged every 3 hrs, 1. Across the amnion exchange with maternal fluids: 2. Fetal swallowing (20 ml/hour) to gut absorption by fetus out the umbilical cord to placenta. Hydraminos excess fluid (>2000 ml), esophageal atresia. Oligohydraminos insufficient fluid (<500 ml) , renal agenesis. Allows free movement which aids in neuromuscular development.
