Intestinal Epithelial Villus – Structure, Function & Disease
An intestinal epithelial villus is a tiny, finger-like projection of the small intestine lining that massively increases the surface area available for nutrient absorption into the body.
Things worth knowing about "Intestinal epithelial villus"
An intestinal epithelial villus is a tiny, finger-like projection of the small intestine lining that massively increases the surface area available for nutrient absorption into the body.
What is an Intestinal Epithelial Villus?
An intestinal epithelial villus (plural: villi) is a microscopic, finger-like projection of the mucous membrane lining the small intestine. Together with the even smaller microvilli – tiny hair-like structures on the surface of epithelial cells – the villi form the so-called brush border. This arrangement increases the inner surface area of the small intestine to approximately 200 square meters, enabling highly efficient absorption of nutrients from digested food into the bloodstream.
Structure of the Intestinal Epithelial Villus
Each intestinal villus consists of several functionally important components:
- Epithelial cells (enterocytes): These cells cover the surface of the villus and are directly responsible for nutrient absorption.
- Goblet cells: These cells secrete mucus (mucin) to protect and lubricate the intestinal lining.
- Blood capillaries: These absorb water-soluble nutrients such as sugars and amino acids and transport them via the portal vein to the liver.
- Central lymph capillary (lacteal): This vessel transports fat-soluble nutrients, particularly dietary fats and fat-soluble vitamins, into the lymphatic system.
- Connective tissue and smooth muscle cells: These provide structural support and allow the villus to move, which promotes nutrient absorption.
Function of the Intestinal Epithelial Villi
The primary role of the intestinal villi is absorption – taking up digested nutrients from the gut lumen into the circulation. The following substances are absorbed by the villi:
- Carbohydrates (as monosaccharides, e.g., glucose and fructose)
- Proteins (as amino acids and dipeptides)
- Fats (as fatty acids and monoglycerides, later transported as chylomicrons via the lymph)
- Vitamins (both water-soluble and fat-soluble)
- Minerals and trace elements (e.g., calcium, iron, zinc)
- Water
Beyond nutrient absorption, the villi also play an important role in intestinal immune defense, as specialized immune cells (such as intraepithelial lymphocytes) are located within the villus epithelium.
Diseases Affecting the Intestinal Villi
Several conditions can damage or destroy the intestinal villi, leading to significant impairment of nutrient absorption:
- Coeliac disease: An autoimmune condition in which gluten triggers an immune response that attacks the intestinal villi, causing characteristic villous atrophy (flattening or total loss of villi). This results in malabsorption and nutritional deficiencies.
- Crohn's disease: A chronic inflammatory bowel disease that can damage all layers of the intestinal wall, including the villi.
- Tropical sprue: An infectious condition that also causes villous atrophy.
- Short bowel syndrome: Following surgical removal of sections of the small intestine, the available villous surface area is reduced.
- Radiation enteritis: Radiation-induced damage to the intestinal mucosa and villi.
Diagnostic Relevance
Assessing the condition of the intestinal villi is a key diagnostic step when malabsorption disorders are suspected. The method of choice is endoscopic small bowel biopsy, in which small tissue samples are taken and examined histologically. The Marsh classification is used, for example, to grade the degree of villous atrophy in coeliac disease – ranging from minimal changes (Marsh I) to complete loss of villi (Marsh III).
Regeneration and Renewal
The cells lining the intestinal villi renew themselves very rapidly – the complete turnover of the intestinal epithelium takes only about 3 to 5 days. The stem cells responsible for this renewal are located in the crypts of Lieberkühn, small glands situated between the villi. This high regenerative capacity allows the intestine to recover relatively quickly after injury or inflammation – for example, following a strict gluten-free diet in patients with coeliac disease.
References
- Marieb E.N., Hoehn K.: Human Anatomy and Physiology. 10th edition. Pearson Education, 2015.
- Green P.H.R., Cellier C.: Celiac Disease. New England Journal of Medicine, 2007; 357(17):1731–1743. DOI: 10.1056/NEJMra071600.
- World Gastroenterology Organisation (WGO): Global Guidelines – Celiac Disease. WGO, 2016. Available at: https://www.worldgastroenterology.org
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