Villi

Villi are small, finger-like projections that extend into the lumen of the small intestine. They are part of the intestinal mucosa layer. The villi increase the internal surface area of the intestinal walls making available a greater surface area for absorption. Each villus is approximately 0.5-1.6 mm in length and has many microvilli, each of which are much smaller than a single villus. The villi are connected to the blood vessels so the circulating blood then carries these nutrients away.

Structure

Villi are specialized for absorption in the small intestine as they have a thin wall, one cell thick, which enables a shorter diffusion path. They have a large surface area so there is more space for absorption. The presence of many villi and microvilli increases the surface area of the intestine and facilitates the absorption of nutrients.

Function

The main functions of the villi and the microvilli are to increase the amount of surface area available for the absorption of nutrients, break down food products into their smallest usable components (amino acids, fatty acids, monosaccharides), and then absorb these small molecules for use in the body's cells.

Clinical significance

Damage to the villi can result in decreased absorption of nutrients, which can lead to conditions such as celiac disease or tropical sprue.

See also

• Microvillus
• Intestinal villus
• Rugae
• Peyer's patches

References

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