A minute finger-like projection from a membranous surface. Millions of villi are present on the mucous lining of the small intestine. Each intestinal villus contains a small lymph vessel and a network of capillaries.
Its surface is covered with hundreds of hairlike structures (microvilli).
The villi and microvilli provide a large surface area for absorption of food molecules from the intestine into the blood and the lymphatic system.
One of the minute processes thickly distributed upon the inner surface of the small INTESTINE, giving it, to the naked eye, a velvety appearance, and greatly assisting absorption of digested food. (See also DIGESTION; ABSORPTION; ASSIMILATION.)
n. (pl. villi) one of many short finger-like processes that project from some membranous surfaces. Numerous intestinal villi line the small *intestine. Each contains a network of blood capillaries and a *lacteal. Their function is to absorb the products of digestion and they greatly increase the surface area over which this can take place. Chorionic villi are folds of the *chorion (the outer membrane surrounding a fetus) from which the fetal part of the *placenta is formed. They provide an extensive area for the exchange of oxygen, carbon dioxide, nutrients, and waste products between maternal and fetal blood. See also arachnoid villus; chorionic villus sampling.
A method of diagnosing genetic abnormalities in a fetus using a small sample of tissue taken from the chorionic villi at edge of the placenta. Because the cells have the same chromosome makeup as those in the fetus, they can be used to detect genetic abnormalities. Chorionic villus sampling (CVS) is usually performed in the first 3 months of pregnancy in women who are at a higher-than-normal risk of having a child with a chromosomal disorder, such as Down’s syndrome, or a genetic disease, such as thalassaemia. Chromosome analysis of the villi cells takes place in the laboratory. CVS slightly increases the risk of miscarriage. choroid A layer of tissue at the back of the eye, behind the retina. The choroid contains many blood vessels that supply nutrients and oxygen to the retinal cells and to surrounding tissues in the eye. choroiditis Inflammation of the choroid. It is often caused by infections such as toxocariasis or toxoplasmosis, more rarely by sarcoidosis, syphilis, and histoplasmosis. It sometimes has no obvious cause. Treatment includes corticosteroid drugs for the inflammation, and antibiotic drugs for any causative infection.... chorionic villus sampling
one of the thin-walled projections outwards of the arachnoid membrane into the blood-filled sinuses of the dura, acting as a one-way valve for the flow of cerebrospinal fluid from the subarachnoid space into the bloodstream. Large villi, known as arachnoid granulations (or Pacchionian bodies), are found in the region of the superior sagittal sinus. They may be so distended as to cause pitting of the adjacent bone.... arachnoid villus
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