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How does the trophoblast help form the placenta?

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A series of medical illustrations showing the stages of childbirth: the baby's position at the onset of labor, flexion, internal rotation of the head, extension, external rotation of the head, and the uterus immediately after birth with the placenta and umbilical cord. — birth Sequential changes in the position of the child during labour.

The trophoblast is essential to the formation of the placenta through its ability to invade the endometrium and establish a connection between the fetus and the mother.1

The process involves several key stages:

Invasion and Erosion: The trophoblast secretes enzymes that erode the uterine lining, allowing the blastocyst to implant. It differentiates into an outer layer, the syncytiotrophoblast, and an inner layer, the cytotrophoblast.12
Formation of Lacunae: The syncytiotrophoblast develops cavities (lacunae) that tap into maternal blood vessels. This creates an intervillous space filled with maternal blood, which serves as the site for physiological exchange.312
Development of Villi: The cytotrophoblast forms finger-like projections that extend into the syncytiotrophoblast. These become the cores of chorionic villi. As connective tissue and fetal blood vessels grow into these villi, they create a treelike structure that facilitates the diffusion of nutrients, oxygen, and waste between maternal and fetal bloodstreams without the two mixing.341
Anchoring: Some villi attach to the maternal tissue to anchor the placenta, while others float freely in the maternal blood lake to maximize exchange surface area.31