Villus

In the syllabus and the exam

The villus is the structure-function centrepiece of the absorption content standard, and candidates are expected to link at least four features to efficient absorption: a thin, single-cell-thick epithelial wall that shortens the diffusion pathway, a rich capillary network that carries absorbed glucose and amino acids away to maintain a concentration gradient, a lacteal at the centre that absorbs fatty acids and glycerol into the lymphatic system, and microvilli on individual epithelial cells that further enlarge the absorbing surface. A well-worn SPM question shows a cross-section of a villus and asks candidates to label the lacteal, capillary network and epithelium, then explain why the small intestine's total surface area for absorption is so large; answers that describe only the number of villi present, without also mentioning microvilli or the folded lining, tend to lose marks. Candidates sometimes confuse the villus, a structure of the small intestine wall, with the microvillus, which is a much smaller finger-like extension on the surface of a single villus cell.

Example

The huge combined surface area of millions of villi allows digested nutrients to be absorbed into the blood quickly.

Related terms

DigestionAssimilationDiffusion

Source:SRC-DSKP-EN