chorionic stem villous blood vessel

A chorionic stem villous blood vessel is a blood vessel located within a chorionic stem villus, the largest type of chorionic villus that forms the structural trunk of the villous tree. These vessels carry fetal blood between the chorionic plate and the peripheral branches of the villous tree.

Chorionic stem villi contain the largest fetal blood vessels in the villous tree, including arterioles and venules as well as small arteries and veins. These vessels are supported by a dense fibrous stroma. As the villi branch into smaller subtypes, the vessel caliber decreases progressively until the terminal villous capillaries are reached.

The primary function of chorionic stem villous blood vessels is to distribute and collect fetal blood throughout the villous tree. They carry deoxygenated, nutrient-depleted fetal blood from the chorionic plate arteries to the peripheral villi for exchange, and return oxygenated, nutrient-rich blood from the peripheral villi back to the chorionic plate veins and ultimately to the fetus via the umbilical vein.

Chorionic stem villi arise from the chorionic plate (fetal side of placenta) and form the trunk-like branches of the villous tree. From each stem villus, intermediate villi and ultimately terminal villi branch off, creating a tree-like structure immersed in maternal blood in the intervillous space. Each stem villus and its branches form a functional cotyledon.

Fetal vascular malperfusion is a category of placental injury affecting fetal vessels including those in stem villi. Thrombosis, intimal cushions, or luminal obliteration in stem villous vessels can cause downstream villous avascular fibrosis. This condition is associated with fetal growth restriction, stillbirth, and adverse neonatal outcomes such as cerebral palsy.