villous

Villous is an anatomical adjective describing structures that resemble or consist of villi, the finger‑like projections found in several organs. The term derives from Latin villus, meaning tuft of hair. It is used to describe features of both the intestinal mucosa and the placenta, among other tissues.

In the intestine, intestinal villi project into the lumen of the small intestine and increase the surface area available for nutrient absorption. Each villus contains a core of lamina propria with blood vessels and a central lacteal, surrounded by a simple columnar epithelium with microvilli. Villous height and architecture contribute to absorptive efficiency and are modulated by diet, injury, and disease.

In the placenta, chorionic villi are projections of fetal tissue that extend into the maternal intervillous space. They contain a mesenchymal core with fetal blood vessels and are covered by trophoblastic epithelium. Floating villi extend into maternal blood, while anchoring villi connect to the decidua. The terminal villi, at the distal ends, are the primary sites of maternal–fetal exchange.

Pathology often centers on changes in villous structure. Villous atrophy or blunting reduces absorptive or exchange surface and is a hallmark of conditions such as celiac disease and certain infections. Placental villitis denotes inflammation of placental villi and can accompany infectious or immune‑mediated processes; villous immaturity or edema may be seen in fetal growth restriction or other placental dysfunctions.

Overall, the term villous emphasizes origination from or resemblance to villi in functional and diagnostic contexts.