Lymphoid plaques of the small intestine

Lymphoid plaques (noduli lymphoidei aggregati), or as they are also called, Peyer's patches, are nodular accumulations of lymphoid tissue. The plaques are located in the walls of the small intestine, mainly its terminal section - the ileum, in the thickness of the mucous membrane and in the submucosa. In these places, the muscular plate of the mucous membrane is interrupted or absent. Lymphoid plaques look like flat formations, mainly oval or round, slightly protruding into the lumen of the intestine. Plaques are most often located on the side opposite the mesenteric edge of the intestine, in some cases - near the mesenteric edge of the intestine. The long size of the plaques is usually oriented along the intestine. There are plaques lying obliquely in relation to the long axis of the intestine or even in the transverse direction. The latter are occasionally located at the very end of the ileum, near the ileocecal valve. The circular folds of the mucous membrane are interrupted at the site of lymphoid plaques. The plaques are located almost next to each other, sometimes the distance between them reaches several tens of centimeters. The number of lymphoid plaques during the period of their maximum development (in children and adolescents) is 33-80.

The length of lymphoid plaques varies widely - from 0.2 to 1.5 cm, the width does not exceed 0.2-1.5 cm. The mucous membrane of the ileum in the area of lymphoid plaques is uneven, bumpy. Between the tubercles, the transverse dimensions of which reach 1-2 mm, there are small depressions.

Lymphoid plaques are built from lymphoid nodules, the number of which in one plaque ranges from 5-10 to 100-150 or more. Between the nodules there is diffuse lymphoid tissue, thin bundles of connective tissue fibers. Intestinal glands are found between individual nodules. Nodules often lie one above the other in two rows. The size of lymphoid nodules that form plaques in children, adolescents and young men ranges from 0.5 to 2 mm. The central part of most nodules is occupied by a large reproduction center.

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Development and age-related features of lymphoid plaques of the ileum

An accumulation of lymphoid cells in the thickness of the terminal section of the small intestine can be detected in the fetus in the 4th month of intrauterine life. The boundaries of the future nodules are unclear, the cellular elements in them are loosely arranged. The intestinal mucosa is thickened in these places. In a 5-month-old fetus, the nodules in the mucosa become rounded, and their contours are more defined. The size of the lymphoid plaques of the ileum in fetuses does not exceed 2 cm in length and 0.2 cm in width, their number before birth varies from 5 to 21. In newborns, these plaques do not yet protrude above the surface of the mucous membrane. Their number reaches 30, and the length of the largest of them is 2-3 cm. In single nodules that are part of the plaques, there are already reproduction centers. As the child ages, the number of nodules containing a reproduction center increases rapidly. In children in the first year of life, lymphoid plaques already protrude above the surface of the mucous membrane. After 20 years and especially in people over 30 years old, the borders of lymphoid plaques are less noticeable on the surface of the mucous membrane, and after 40-50 years, the surface of the mucous membrane above the plaques is smoothed out.

The number of lymphoid plaques decreases with age. In people over 40, the number of plaques does not exceed 20, and over 60 - 16. The size of plaques and the number of lymphoid nodules in their composition decrease. After 50-60 years, reproduction centers in lymphoid nodules are rare.

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