Krummdarm

Krummdarm, in anatomical usage, refers to the ileum, the final portion of the small intestine between the jejunum and the cecum. In adults it typically measures about 3 to 4 meters in length and is suspended in the abdomen by the mesentery, which carries vessels, nerves, and lymphatics. The ileum is divided into proximal and distal segments, with the terminal ileum ending at the ileocecal valve, which regulates the flow of chyme into the large intestine and helps prevent backflow.

Histologically, the mucosa of the ileum contains well-developed villi and crypts, with numerous goblet cells and specialized lymphoid tissue known as Peyer’s patches in the lamina propria and underlying submucosa. This lymphoid tissue is part of the gut-associated immune system and plays a role in immune surveillance.

Functions of the Krummdarm include reabsorption of most bile acids and vitamin B12, which are important for fat digestion and red blood cell production, respectively. The ileum also continues the absorption of water, electrolytes, and nutrients, and participates in immune defense through Peyer’s patches. The distal ileum can exhibit absorption adaptations for bile acids and fats depending on dietary intake and intestinal health.

Clinical relevance includes diseases that commonly affect the terminal ileum, such as Crohn’s disease, which can cause inflammation, strictures, and malabsorption. Surgical removal of the ileum (ileectomy) can lead to bile acid malabsorption and B12 deficiency, with associated diarrhea and nutritional consequences.