Topic 50 of 55 in the MU Plovdiv syllabus for Cytology, Histology and Embryology (Dental Medicine, Year 1). The free AceMed note covers it in 5 sections, about 339 words (3 min of reading), with 13 flashcards.
In this note
Introduction
Amnion:
Chorion:
Yolk Sac:
Allantois:
Amnion:
Structure: The amnion is a thin, transparent membrane that surrounds the fetus.
Location: It forms from the epiblast layer of the bilaminar embryonic disc and grows to encase the fetus.
Function:
Contains amniotic fluid, which cushions and protects the fetus.
Maintains a stable temperature and pressure around the fetus.
Allows for fetal movement, which is important for musculoskeletal development.
Prevents adhesions between the fetus and the membranes.
Chorion:
Structure: The chorion is the outermost membrane surrounding the fetus and the amnion. It is formed by the trophoblast layer (specifically the cytotrophoblast and syncytiotrophoblast) and the extra-embryonic mesoderm.
Location: The chorion is located outside the amnion and forms the outermost layer of the fetal membranes.
Function:
Contributes to the formation of the placenta.
In the early stages of pregnancy, the chorionic villi (finger-like projections) invade the maternal endometrium to establish maternal-fetal blood exchange.
Produces human chorionic gonadotropin (hCG), which helps maintain the pregnancy by supporting the corpus luteum and stimulating the production of progesterone.
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