jejunum lamina propria

The jejunum lamina propria is the layer of loose connective tissue within the mucosal layer of the jejunum, the middle segment of the small intestine. It lies between the simple columnar epithelium of the intestinal surface and the muscularis mucosae, and it contains the supporting structures for the overlying villi.

The jejunum lamina propria is similar in composition to that of the ileum but contains fewer lymphoid structures. While the ileum lamina propria is notably rich in Peyer's patches (organized lymphoid follicles), the jejunum has only scattered isolated lymphoid follicles in its lamina propria. The jejunum also has taller villi and more prominent circular folds (plicae circulares), reflecting its primary role in nutrient absorption.

The jejunum lamina propria contains fibroblasts, myofibroblasts, smooth muscle cells, plasma cells (which secrete IgA), lymphocytes, macrophages, dendritic cells, mast cells, and eosinophils. The subepithelial fibroblasts form a sheath around the crypts of Lieberkühn and play roles in regulating epithelial cell differentiation and function.

The jejunum lamina propria supports the intestinal villi by providing a vascular and lymphatic core to each villus. Each villus contains a central lacteal (lymphatic capillary) surrounded by a fenestrated capillary network within the lamina propria. These structures collect absorbed nutrients: lipids enter the lacteal as chylomicrons while amino acids and sugars enter the blood capillaries.

Celiac disease (gluten-sensitive enteropathy) classically affects the jejunum most severely, with villous atrophy, crypt hyperplasia, and a dense inflammatory infiltrate in the lamina propria dominated by lymphocytes and plasma cells. Giardiasis can also cause jejunal mucosal changes. Tropical sprue and common variable immunodeficiency (with absent plasma cells in the lamina propria) are other important conditions affecting this structure.