Histology of the Small Intestine

The histology of each part of the small intestine varies. The jejunum has the most prominent folds and villi, while the distal ileum has fewer folds but has Peyer's patches, which are aggregated lymphoid nodules in the lamina propria.

The small intestine has a series of circular folds, each with fingerlike projections called intestinal villi.

The villi are covered by simple columnar epithelium. These epithelial cells are also called absorptive cells or enterocytes, as they possess microvilli that absorb nutrients from chyme.

The goblet cells, also housed in the villi, secrete mucus.

The lamina propria, or the core of a villus, contains blood capillaries and a large lymphatic vessel called a lacteal.

The base of a villus also has intestinal glands, or crypts, that secrete intestinal juice.

Additionally, the intestinal glands also contain Paneth and enteroendocrine cells.

Paneth cells secrete lysozyme and perform phagocytosis, regulating the microbial population in the small intestine.

Enteroendocrine cells like S, CCK, and K cells, secrete hormones like secretin, cholecystokinin, and glucose-dependent insulinotropic peptides respectively.