. Cunningham's Text-book of anatomy. Anatomy. Fig. 930.—Plios: Circulaees (natural size). A, as seen in a portion of jejunum which has been filled with alcohol and hardened B, a portion of fresh intestine spread out under water. testine is examined, it is seen to present a soft, velvety, or fleecy appearance (Fig. 930, B); this is due to the presence of an enormous number of minute processes, known as villi, which cover its surface. Thev are minute cylindrical or finger-like projections of the tunica mucosa (Fig. 929) about aVth or J^th of an inch (1-2 to 1 • 6 mm.) in height, and barely visib
. Cunningham's Text-book of anatomy. Anatomy. Fig. 930.—Plios: Circulaees (natural size). A, as seen in a portion of jejunum which has been filled with alcohol and hardened B, a portion of fresh intestine spread out under water. testine is examined, it is seen to present a soft, velvety, or fleecy appearance (Fig. 930, B); this is due to the presence of an enormous number of minute processes, known as villi, which cover its surface. Thev are minute cylindrical or finger-like projections of the tunica mucosa (Fig. 929) about aVth or J^th of an inch (1-2 to 1 • 6 mm.) in height, and barely visible to the naked eye, which are closely set all over the surface of the lining membrane of the small in- testine. Begin- ning at the edge of the pyloric valve, they are broad but short in the duodenum, and grow nar- rower as they are followed down through the in- testine to the valvula coli, at the edge of which they cease. They are found, not only on the general surface of the mucous mem- brane, but also upon the plicae circulares, and, while they are not present over the solitary lymph no'dules, they are found in the intervals between the individual nodules of the aggregated nodules. They play an important part in the absorption of the products of digestion which takes place in the small intestine. Plicae Circulares [Kerkringi].—When the intestine is empty and contracted, its mucous membrane is thrown into effaceable folds or rugae, which disappear on distension. But in addition to these, there are found in certain portions of the small intestine a series of large, permanent transverse folds, which are not effaceable ; these are known as plicae circulares (Fig. 930). These are usually more or less crescentic in shape, and resemble a series of closely placed shelves running transversely around the gut. They rarely form more than two-thirds of a circle; sometimes, however, they present a circular or even a spiral arrangement, the spiral extending little more than once roun
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
