Conniventes

Conniventes, in anatomical terminology, refers to the circular folds of the mucosa and submucosa lining the interior of the small intestine. They are also known as valvulae conniventes or plicae circulares. These permanent folds contribute significantly to the absorptive surface area of the small bowel.

Anatomy and histology

Conniventes are transverse, crescent- or ring-shaped folds that extend mainly through the mucosa and submucosa. They are composed of connective tissue cores covered by a mono-layer of simple columnar epithelium with goblet cells. The folds increase the luminal surface area and create micro-convexities that aid in mixing intestinal contents and exposing nutrients to the absorptive surface. Blood vessels, nerve fibers, and lymphatic tissue support the mucosa within the folds.

Distribution and variation

Plicae circulares are most prominent in the proximal portions of the small intestine, particularly the jejunum, and gradually diminish in height toward the distal ileum. They are present in the duodenum and jejunum and persist to a lesser extent in the ileum, where they eventually become less conspicuous. They are not present in the large intestine.

Function

The primary roles of conniventes are to increase the absorptive surface area and to slow the transit of chyme, allowing more time for digestion and nutrient absorption. Together with villi and microvilli, they substantially enhance the efficiency of nutrient uptake in the small intestine.

Clinical notes

Radiographic imaging and endoscopy can depict these folds as characteristic circular ridges in the small bowel. Alterations in their prominence can be observed in certain diseases that affect mucosal architecture or intestinal motility.