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Age features of the small intestine
Last reviewed: 23.04.2024
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The small intestine of the newborn has a length of 1.2-2.8 m; at the age of 2-3 years, its length is on average 2.8 m. By the middle of the period of the second childhood its length is equal to the length of the gut of the adult person (about 5-6 m). The width of the lumen of the small intestine by the end of the first year is 16 mm, and by 3 years - 23.2 mm.
The duodenum of the newborn has an annular shape, its curves are formed later. The beginning and the end of it are located at level I of the lumbar vertebra. At the age of more than 5 months, the upper part of the duodenum is at the level of the XII thoracic vertebra; to 7 years, the descending part drops to the II lumbar vertebra and even lower (to 12 years). The duodenal glands of the newborn are of small size, they are weaker than the adult. Most intensively, they develop in the first years of a child's life.
In the newborn, the location of the jejunal and ileal loops is different - horizontal and vertical, which is related to the position of the mesentery root and the functional state of the gut. The folds and villi of the mucous membrane are weakly expressed. The number of intestinal glands increases in the first year of life. Single and group lymphoid nodules (lymphoid plaques) in the thickness of the mucous membrane of the intestine in the newborn are already present. The muscular membrane is poorly developed, especially its longitudinal layer.
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