Jejunal Villus – Function, Structure and Diseases

What Is a Jejunal Villus?

A jejunal villus (plural: villi) is a tiny, finger-shaped protrusion of the mucosal lining found in the jejunum, the middle section of the small intestine located between the duodenum and the ileum. These structures are a defining anatomical feature of the small intestine and are essential for the digestion and absorption of nutrients.

Structure and Anatomy

Jejunal villi are composed of several specialized cell types and tissue components:

• Enterocytes: The predominant epithelial cells covering the villus surface. Their luminal surface is covered with microvilli (brush border), further multiplying the absorptive surface area.
• Goblet cells: Secrete mucus (mucin) to protect and lubricate the intestinal lining.
• Enteroendocrine cells: Release hormones that regulate digestive processes.
• Blood and lymphatic capillaries: Each villus contains a central lymphatic vessel (lacteal) and a network of blood capillaries through which absorbed nutrients enter the bloodstream and lymphatic system.

The combined effect of villi and microvilli expands the effective absorptive surface of the small intestine to approximately 200–300 square meters, despite the intestine being only a few meters in length.

Function of Jejunal Villi

The primary function of jejunal villi is the absorption of nutrients from the digested food mass (chyme). The jejunum is particularly active in absorbing:

• Carbohydrates (e.g., glucose, fructose) following enzymatic breakdown
• Amino acids and peptides from protein digestion
• Fatty acids and monoglycerides from fat digestion (absorbed via the lymphatic system)
• Fat-soluble vitamins (A, D, E, K)
• Water-soluble vitamins such as folic acid and vitamin B1
• Minerals including calcium, iron, and magnesium

Clinical Relevance

Conditions that damage or destroy jejunal villi lead to significantly impaired nutrient absorption, resulting in malabsorption syndromes. Key conditions include:

Coeliac Disease

In coeliac disease (gluten-sensitive enteropathy), the ingestion of gluten – a protein found in wheat, barley, and rye – triggers an immune response that causes villous atrophy, meaning the villi flatten and eventually disappear. This leads to diarrhoea, weight loss, bloating, and nutritional deficiencies.

Crohn Disease

This chronic inflammatory bowel disease can affect any part of the gastrointestinal tract, including the jejunum. Inflammation damages the villous architecture and impairs absorption.

Tropical Sprue

An infectious condition, likely caused by bacterial overgrowth, that also leads to villous atrophy and is most common in tropical regions.

Short Bowel Syndrome

Following surgical removal of large portions of the small intestine, reduced villous surface area leads to severe nutritional deficiencies and dependence on parenteral nutrition.

Diagnosis

Changes in jejunal villi are typically identified through a small intestinal biopsy, obtained during an upper endoscopy or capsule endoscopy. The biopsy is assessed histologically (under a microscope) for villous height, crypt depth, and the villous-to-crypt ratio. Imaging methods such as capsule endoscopy and MR enterography (MRI with contrast) are also used to evaluate the small intestinal mucosa.

Regeneration of Villi

The small intestinal mucosa has a remarkable capacity for self-renewal. Enterocytes on the villous surface are continuously replaced, with a full cell turnover occurring approximately every 3–5 days. In conditions such as coeliac disease, consistent adherence to a strict gluten-free diet often allows the villous architecture to recover fully over time.

References

1. Lüllmann-Rauch, R. & Asan, E. (2019). Taschenlehrbuch Histologie (6th ed.). Thieme Verlag.
2. Kasper, D. L. et al. (2015). Harrison's Principles of Internal Medicine (19th ed.). McGraw-Hill Education.
3. World Gastroenterology Organisation (WGO) Global Guidelines: Celiac Disease (2016). Available at: https://www.worldgastroenterology.org