villi


Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Related to villi: Arachnoid villi, Chorionic villi

villi:

see digestive systemdigestive system,
in the animal kingdom, a group of organs functioning in digestion and assimilation of food and elimination of wastes. Virtually all animals have a digestive system. In the vertebrates (phylum Chordata, subphylum Vertebrata) the digestive system is very complex.
..... Click the link for more information.
.

Villi

 

microscopic processes of the inner membranes of a number of organs, chiefly in higher vertebrate animals and man.

(1) Processes of the intestinal mucous membrane in some amphibians, birds, and mammals. They are formed by intestinal epithelium and connective tissue rich in muscles, blood and lymph vessels, and nerves. There are about 4 million villi in the human intestine, and they have a total area of about 43 sq m. Their shape and size vary depending on the nature of the nutrients and the segment of the intestine. They are 0.3-0.5 mm high and about 0.1 mm thick. Villi are covered with a single layer of epithelium consisting of different kinds of cells. Food is actively absorbed through the villi. Muscle contractions of the villi help to mix food in the intestinal cavity and move nutrients arriving through the epithelium along the blood vessels (products of protein and carbohydrate decomposition) and lymph vessels (products of lipolysis). The epithelial cells of the villi are sloughed off and gradually replaced with new ones multiplying in crypts (invaginations of the mucous membrane). The surface of columnar epithelial cells of the villi, which faces the intestinal lumen, has cytoplasmatic processes, or microvilli, on whose external membranes so-called parietal (membrane) digestion takes place. Invertebrates have no villi. However, intestinal epithelium with a border having microvilli is common in many of them. Sometimes the microvilli responsible for parietal digestion cover the external body surface, especially in parasitic forms not having an intestine.

(2) Projections of the synovial membrane of joint capsules, covered with an epithelioid layer of synovial cells.

(3) Projections of one of the embryonic membranes, the chorion.

E. S. KIRPICHNIKOVA

References in periodicals archive ?
It effectively prevented sloughing and denaturating of villi and microvilli in the small intestine with clear and intact villi margin and intrinsic morphology.
It is known that excess syncytial knot formation occurs in generalized from whenever the fetal circulation through the villi appears to be reduced.
Cytomegalovirus immunohistochemistry will highlight both intranuclear and intracytoplasmic inclusions and may highlight eosinophilic necrotic debris within the villi and infected cells that do not show classic viral cytopathic effect (Figure 3, A and B).
These ridges form a series of crisscross elevations across the mucosal surface, leading to a mucosal "ground plan" from which villi originate, as revealed by scanning electron microscopy (EM) (15) (Figure 1, 2).
wall, the villi absorb nutrients and deposit them in the capillaries
The aim of this work is to perform a review of the morphological features of the human placenta and its free chorionic villi in normal pregnancies and in the presence of high blood pressure and diabetes.
The results showed a trend toward systematic improvement in villous health in newly diagnosed patients adhering to a gluten-free diet whereas the other cohort groups representing healthy villi showed negligible further improvement as expected.
At 14 weeks, villi were better developed, and intestinal glands were seen in abundance.
In ileum, widely separated villi lined with a single layer of columnar epithelium with basal oval nuclei and numerous goblet cells.
Placental histology was studied in trisomy 18, which featured cystic and dilated chorionic villi with hydropic change [16].
"And then you can count how many crypts and villi are there and how complex they look."