placenta, umbilical cord- discussion, viva

Placenta:

1. Give histological structures of the placenta
• Maternal surface irregular because of cotyledons separated by placental septa. It is formed by basal plate which includes decidua basalis
• Fetal surface is smooth, covered by amnion and gives attachment to umbilical cord. It is formed by amnion, chorionic plate, chorionic villi from outside inwards
2. What is decidua basalis?
• Decidua basalis is the part of endometrium present between the implanted embryo and myometrium
3. What are chorionic villi? What are the types? 
• Chorionic villi are the finger like projections from the chorionic plate formed by cytotrophoblast and syncytiotrophoblast. 
• 3 types of chorionic villi- primary, secondary, tertiary villi
4. Give the structure of the three villi
• Primary villi- simple cord with a solid core of cytotrophoblast surrounded by syncytiotrophoblast
• Secondary villi- projection with central core of mesoderm surrounded successively by cytotrophoblast and syncytiotrophoblast
• Tertiary villi- projection with fetal blood vessels in the core of mesoderm surrounded successively by cytotrophoblast and syncytiotrophoblast. along with fetal capillaries there are fibroblasts and phagocytic cells called Hofbauer cells
5. What are anchoring villi and floating or free villi
• Anchoring villi- villi attached to chorionic plate
• Floating or free villi- the branches from anchoring villi which float in intervillous spaces
6. Name the site of exchange occurring in placenta
• Exchange occurs between the embryonic blood in chorionic villi outside the embryo and maternal blood in lacunae called intervillous spaces of decidua basalis
7. Name the layers of placental barrier
• Upto 20 weeks
• Syncytiotrophoblast
• Cytotrophoblast
• Connective tissue of villi
• Endothelium of fetal capillaries
• After 20 weeks
• Syncytiotrophoblast
• Connective tissue of villi
• Endothelium of fetal capillaries
8. What are the functions of placenta?
• Exchange of nutrients, oxygen, carbon-dioxide, wastes between mother and fetus
• Passive immunity to fetus by transfer of maternal IgG antibodies
• Secretes human chorionic gonadotrophin (hCG), estrogen, progesterone and placental lactogen

Umbilical Cord:

1. Give the structure of umbilical cord
• It is surrounded by amnion
• It consists of two umbilical arteries and one umbilical vein
• The vessels are surrounded by primary mesoderm called Wharton's jelly which protects the vessels
2. What is Wharton's jelly?
• Wharton’s jelly is a mass of loose connective tissue with fibroblasts separated by fine collagen fibers and ground substance containing hydrated glycosaminoglycans rich in hyaluronic acid. It gives cushioning effect to vessels.
3. What are the functions of umbilical arteries and vein?
• Umbilical arteries- carry deoxygenated blood from fetus to placenta
• Umbilical vein- carry oxygenated blood from placenta to fetus