Intestinal Villi – Function, Structure and Diseases

What Are Intestinal Villi?

Intestinal villi (Latin: Villi intestinales) are tiny, finger-like projections that line the inner wall of the small intestine. They are a key structural feature of the intestinal mucosa and play a central role in the absorption of nutrients, vitamins, minerals, and water from digested food into the bloodstream. Together with even smaller projections called microvilli – located on the surface of individual intestinal cells (enterocytes) – they form the so-called brush border, which increases the total absorptive surface area of the small intestine to approximately 200 to 300 square meters.

Structure and Composition

Each intestinal villus consists of several layers and cell types that work together to perform its function:

• Epithelial cells (enterocytes): These cover the surface of the villus and actively absorb nutrients.
• Goblet cells: Produce mucus that protects the intestinal lining.
• Central lymphatic vessel (lacteal): Transports absorbed fats into the lymphatic system.
• Blood capillaries: Absorb water-soluble nutrients such as sugars and amino acids and carry them to the liver via the portal vein.
• Nerve fibers and smooth muscle cells: Enable movement of the villi to improve mixing and contact with intestinal contents.

Between the villi are small invaginations known as crypts of Lieberkühn, where new intestinal cells are continuously produced. The epithelial lining renews itself completely approximately every three to five days.

Functions of Intestinal Villi

The primary role of intestinal villi is absorption – the uptake of nutrients from the small intestine into the body. Specifically, they are responsible for:

• Absorbing carbohydrates (in the form of simple sugars such as glucose and fructose)
• Absorbing amino acids and peptides from protein digestion
• Absorbing fatty acids and glycerol via the lymphatic system
• Absorbing vitamins (fat-soluble via lymph, water-soluble via blood)
• Absorbing minerals such as iron, calcium, and zinc
• Reabsorbing water and electrolytes

Intestinal Villi and Disease

Damage to or loss of intestinal villi can have serious health consequences, as the absorptive surface area is drastically reduced. This leads to a condition known as malabsorption – impaired nutrient uptake from the gut.

Celiac Disease

The most common condition directly affecting intestinal villi is celiac disease (gluten-sensitive enteropathy). In this condition, the immune system reacts to gluten – a protein found in wheat, rye, and barley – and attacks the intestinal mucosa. This leads to progressive flattening and ultimately complete loss of the intestinal villi, known as villous atrophy. Symptoms include diarrhea, bloating, weight loss, and nutritional deficiencies.

Crohn Disease

Crohn disease is a chronic inflammatory bowel disease in which inflammation can occur throughout the entire gastrointestinal tract. This can damage the intestinal villi and lead to malabsorption.

Tropical Sprue

Tropical sprue is a condition occurring in tropical regions, caused by infectious agents that lead to villous atrophy similar to that seen in celiac disease.

Other Causes of Villous Damage

• Chemotherapy and radiation therapy
• Severe gastrointestinal infections
• Long-term malnutrition
• Certain medications (e.g., nonsteroidal anti-inflammatory drugs)

Diagnosis of Intestinal Villus Disorders

When a disorder of the intestinal villi is suspected, several diagnostic approaches are available:

• Small intestinal biopsy: A tissue sample from the small intestine, typically obtained during an upper endoscopy (gastroscopy), is the gold standard for evaluating the condition of intestinal villi.
• Blood tests: Antibodies against tissue transglutaminase (tTG-IgA) for suspected celiac disease, as well as markers of nutritional deficiencies (iron, vitamin B12, folate).
• Stool tests: Detection of fat in the stool (steatorrhea) as a sign of malabsorption.
• Capsule endoscopy: A swallowable camera capsule that allows visual examination of the entire small intestine.

Treatment and Regeneration

Treatment depends on the underlying condition. In celiac disease, a lifelong gluten-free diet is the only effective therapy. With strict dietary adherence, the intestinal villi can fully regenerate over a period of months to years. In inflammatory conditions such as Crohn disease, anti-inflammatory medications, immunosuppressants, and biologic therapies are used. Targeted nutritional supplementation (e.g., iron, vitamin D, B12) is often required to correct deficiencies caused by malabsorption.

References

1. Ludvigsson JF, Leffler DA, Bai JC, et al. The Oslo definitions for coeliac disease and related terms. Gut. 2013;62(1):43–52.
2. Greenberger NJ, Blumberg RS, Burakoff R. Current Diagnosis and Treatment: Gastroenterology, Hepatology, and Endoscopy. 3rd ed. New York: McGraw-Hill Education; 2016.
3. World Gastroenterology Organisation (WGO). Celiac Disease – Global Guidelines. WGO Practice Guidelines; 2016. Available at: https://www.worldgastroenterology.org