Fetal Membranes 2 Lecture 8 PDF

Fetal Membranes II Anatomy Unit  Objectives  1. Describe the development of chorion 2. Describe the chorionic villi fate of chorion 3. Describe the structure, functions, anomalies of the placenta  Case scenar...

Fetal Membranes II Anatomy Unit  Objectives  1. Describe the development of chorion 2. Describe the chorionic villi fate of chorion 3. Describe the structure, functions, anomalies of the placenta  Case scenario A 32-year-old pregnant woman at 30 weeks of gestation comes to her physician because of excess weight gain in a 2-week period. Ultrasonography reveals polyhydramnios. Which fetal abnormality is most likely responsible for the polyhydramnios? (A) Bilateral kidney agenesis (B) Umbilical cord knots (C) Velamentous placenta (D) Hypoplastic lungs (E) Esophageal atresia  Case scenario A 26-year-old pregnant woman experiences repeated episodes of bright red vaginal bleeding at week 28, week 32, and week 34 of pregnancy. The bleeding spontaneously subsided each time. The use of ultrasound shows that the placenta is located in the lower right portion of the uterus over the internal os. What is the diagnosis? (A) Hydatidiform mole (B) Vasa Previa (C) Placenta previa (D) Placental abruption  Chorion  Develops in the second week  Three layered membrane : 1. Syncytiotrophoblast 2. Cytotrophoblast 3. Extraembryonic mesoderm (somatic layer) Chorionic Villi  Definition: finger like processes from trophoblast into decidua basalis and capsularis  Types according to structure: Chorionic villi Structure  Outer syncytiotrophoblast. Primary villi  Inner cytotrophoblast  Outer syncytiotrophoblast. Secondary villi  Inner cytotrophoblast.  Extraembryonic mesoderm  Outer syncytiotrophoblast. Tertiary villi  Inner cytotrophoblast.  Extraembryonic mesoderm  Fetal blood vessels Fate of chorion: Cover chorionic sac till 8th week & as the chorionic sac enlarge  Villi facing decidua capsularis compressed and degenerate forming CHORION LEAVE  Villi facing decidua basalis increase in number &enlarge forming CHORION FRONDOSUM  Placenta barrier or membrane  Definition: membrane separating maternal from fetal blood.  Structure: Before 20th week Syncytiotrophoblast Cytotrophoblast Extra-embryonic mesoderm Endothelium of fetal capillarie After 20th week Syncytiotrophoblast Extra-embryonic mesoderm Endothelium of fetal capillarie late in pregnancy Syncytiotrophoblast Endothelium of fetal capillaries During the later stages of pregnancy, maternal blood is separated from fetal blood by the (A) syncytiotrophoblast only (B) cytotrophoblast only (C) syncytiotrophoblast and cytotrophoblast (D) syncytiotrophoblast and fetal endothelium (E) cytotrophoblast and fetal endothelium PLACENTA Definition: primary site of nutrient and gas exchange between mother and fetus. Structure:  Fetal part: chorion frondosum.  Maternal part: endometrium (decidua basalis) and maternal blood in the intervillous space Gross appearance:  Shape: discoid.  Diameter: 15-20cm.--Thickness: 2-3cm.  Wight: 500-600gm PLACENTA Surfaces: Fetal surface of placenta:  Smooth-shiny and covered by amnion.  Umbilical cord attached near its center.  Umbilical vessels branch on its surface to form chorionic vessels which enter chorionic villi. Maternal surface of placenta: Cobblestone appearance Functions of the Placenta  Exchange of metabolic & gaseous products between maternal & fetal bloodstreams – Respiratory function: Exchange of gases – – Nutritive function: Exchange of nutrients & electrolytes – – Transmission of maternal antibodies –as for diphtheria, small pox, and measles but some viruses as German measles and syphilis pass through placental membrane and cause fetal infection. – Excretory function: Co2 and other stuff  Barrier function: prevents passage of some bacteria and some drugs from maternal to fetal blood. Fetal drug addiction occurs after maternal use of drug as heroin. Functions of the Placenta  Endocrine function: Production of hormones Protein hormones: 1. Human chorionic gonadotropin (early pregnancy tests) 2. Human placental lactogen 3. Relaxin Steroid hormones: 4. Progesterone: from 4th month 5. Estrogen: increase sensitivity of myometrium to oxytocin ANOMALIES OF PLACENTA Anomalies in position  Placenta previa.  Placenta accreta, increta, percreta https://media-us.amboss.com/media/thumbs/big_62ceadc283ddd4.26766207.jpg https://media-us.amboss.com/media/thumbs/big_5c17dc5135f48.jpg ANOMALIES OF PLACENTA Anomalies in shape  Zonary placenta  Bipartite placenta: with one umbilical cord.  Tripartite placenta: with one umbilical cord  Irregular placenta.  Membranous placenta ANOMALIES OF PLACENTA 4. Anomalies in number Succenturiate Placenta: There is one or more small accessory placenta in addition to the main placenta which is retained in the uterus after delivery and causes postpartum hemorrhage.  Case scenario A 26-year-old pregnant woman experiences repeated episodes of bright red vaginal bleeding at week 28, week 32, and week 34 of pregnancy. The bleeding spontaneously subsided each time. The use of ultrasound shows that the placenta is located in the lower right portion of the uterus over the internal os. What is the diagnosis? (A) Hydatidiform mole (B) Vasa Previa (C) Placenta previa (D) Placental abruption For more details, please read  Larsen’s human embryology.  Langman's Medical Embryology,