Placental & Fetal Physiology PDF

# Placenta Formation and Fetal Circulation ## Placenta Formation - **Placenta is formed from trophoblasts upon implantation** - **Formly interlocked** - **Fetal (chorionic) epithelium is bathed in fetal blood** ### Parts of the Placenta - **Decidua parietal** - Fused decidua parietalis, chorion...

# Placenta Formation and Fetal Circulation ## Placenta Formation - **Placenta is formed from trophoblasts upon implantation** - **Formly interlocked** - **Fetal (chorionic) epithelium is bathed in fetal blood** ### Parts of the Placenta - **Decidua parietal** - Fused decidua parietalis, chorion laeve and amnion - **Decidua basalis** - **Chorion frondosum** - **Decidua capsularis** - **Chorion laeve** - **Amniotic cavity** - **Yolk sac** - **Uterine cavity** - **Amniotic cavity** - **Placenta** ### Nitabuch Layer - The layer of fibrinoid degeneration where invading trophoblasts meet the decidua. - **Dysfunction causes placental defects** ### Lobules of the Placenta - Responsible for regulation ### Circumvallate Placenta - A thickened, greyish-white ring on the fetal surface, created by a double fold of amnion and chorion with degenerated decidua and fibrin in between. ### Types of Placenta - **Bilobate** - **Succenturiate** ## Fetal Circulation - Fetal circulation is **opposite to the usual**. - **Oxygenated blood from mother** - (via umbilical vein) - by pass liver - **Ductus venosus** - **Inferior vena cava** (mixes with deoxygenated blood) - **Right atrium** - **Superior vena cava** - **Lung** - **Foramen ovale** - **Pulmonary trunk** - **Right atrium** - **Right ventricle** - **Inferior vena cava** - **Ductus venosus** - **Portal vein** - **Umbilical vein** - **Umbilicus** - **Placenta** - **Ductus arteriosus** - **Pulmonary veins** - **Left atrium** - **Umbilical arteries** - **Descending aorta** ## Umbilical Cord - **Perivascular Whartons Jelly** - **Umbilical cord lining** - **Intervascular Whartons Jelly** - **Umbilical epithelium** - **Umbilical arteries** - **Allantois** ## Abnormal Cord Length - **Normal cord length is 50-60cm, averagely 55 cm** - **Short Cord**: < 35 cm is defined as short cord. It may lead to fetal distress, placental abruptio, prolonged labour. - **Long Cord**: > 80 cm is defined as long cord. It can result in cord around neck, cord around body, cord knot, cord prolapse, and cord compression. ## Timing of Fetal Development - **After 3^rd trimester ** - **The first to become** ## Variations of the Placenta - **Complete** - **Partial** - **Marginal** - **Low lying** - **Vasa previa with velamentous cord insertion** - **Vasa previa with a bilobed placenta** ## Placental Abruption - **Revealed placental abruption** - **Concealed placental abruption** - **Accreta** - **Increta** - **Percreta** ## Velamentous Cord Insertion - **Normal Umbilical Cord Insertion** - **Velamentous Cord Insertion** ## Fetal Development - **Fertilized egg (zygote)** - **Fertilization** - **Cleavage** - **2-cell stage** - **4-cell stage** - **8-cell uncompacted morula** - **8-cell compacted morula** - **Early blastocyst** - **Blastocoel** - **Inner cell mass** - **Late-stage blastocyst** - **Zona pellucida** (hatching) - **Epiblast** - **Hypoblast** ## Summary of Important Points - **Placenta is formed from trophoblasts upon implantation** - **Fetal (chorionic) epithelium is bathed in fetal blood** - **The layer of fibrinoid degeneration where invading trophoblasts meet the decidua is called the Nitabuch layer.** - **Dysfunction causes placental defects** - **The fetal circulation is opposite to the usual** - **The chorion frondosum forms the placenta** - **The placental barrier between maternal and fetal blood that allows exchanges of nutrients and gases and also represents the endocrine tissue of the human placenta. ** - **The inner cellular layer of the trophoblast of an embryonic placental mammal that gives rise to the plasmodial syncytiotrophoblast covering the placental villi. ** ## References - This document has been modified with Flexcil app (Android) [https://www.fexcil.com](https://www.fexcil.com)