Placenta

The placenta is a vital organ that facilitates nutrient, gas, and waste exchange between the mother and the fetus, ensuring the proper development of the fetus. It consists of both fetal and maternal components, each with specific structures and functions.

Fetal Component of the Placenta

1. Cytotrophoblast

Location: Inner layer of chorionic villi
Function: Produces new cells, contributing to the structure and growth of the placenta.
Characteristics:
- Acts as a cellular layer forming the initial scaffold of the placenta.

2. Syncytiotrophoblast

Location: Outer layer of chorionic villi
Function: Synthesizes and secretes hormones essential for pregnancy.
- Notably secretes human chorionic gonadotropin (hCG), which is structurally similar to luteinizing hormone (LH).
- hCG Role: Stimulates the corpus luteum to secrete progesterone, crucial for maintaining the pregnancy during the first trimester.
Immunological Feature: Lacks MHC-I expression, which reduces the likelihood of maternal immune system attacks on the fetal cells.

Component	Location	Function	Key Feature
Cytotrophoblast	Inner layer of chorionic villi	Produces cells	Cell formation
Syncytiotrophoblast	Outer layer of chorionic villi	Synthesizes hCG; protects fetus from immune attack	Lacks MHC-I, immune evasion

Maternal Component of the Placenta

Decidua Basalis

Origin: Derived from the maternal endometrium.
Function: Provides maternal blood to the lacunae (intervillous spaces) for nutrient and gas exchange.
Location: Forms the outer layer of the placenta, anchoring it to the uterine wall and supporting fetal development.

Component	Origin	Function
Decidua basalis	Maternal endometrium	Supplies maternal blood to fetal lacunae

Points to Remember

The placenta is the main site for maternal-fetal exchange.
Cytotrophoblast forms the cellular foundation of the placenta.
Syncytiotrophoblast produces hormones like hCG, critical for pregnancy maintenance.
The decidua basalis provides maternal blood to the fetal component for nutrient and gas exchange.
Syncytiotrophoblast’s lack of MHC-I prevents maternal immune attacks on fetal tissues.

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