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Any of the minute fingerlike projections of the fetal chorion that contain fetal blood vessels and that combine with maternal uterine tissue to form the placenta.
Etymology: Gk, chorion + L, villus, shaggy hair
any of the tiny vascular fibrils on the surface of the chorion that infiltrate the maternal blood sinuses of the endometrium and help form the placenta.
pl. villi [L.] a small process or protrusion, as from the free surface of a membrane.
microscopic projections of the arachnoid into some of the venous sinuses. Called also arachnoid granulations.
threadlike projections originally occurring uniformly over the external surface of the chorion.
multitudinous threadlike projections covering the surface of the mucous membrane lining the small intestine, serving as the sites of absorption of fluids and nutrients.
slender projections from the surface of the synovial membrane into the cavity of a joint; called also haversian glands.