Question 1

What is a lacteal and what does it absorb?

Accepted Answer

A lacteal is the blind-ended lymphatic capillary at the centre of each intestinal villus. It absorbs dietary fats — fatty acids and glycerol re-packaged as chylomicrons — along with fat-soluble vitamins (A, D, E and K). These substances drain into the lymph and later reach the bloodstream via the thoracic duct.

Question 2

How do villi increase the absorptive surface area of the small intestine?

Accepted Answer

The small intestine is folded at three nested levels: permanent circular folds (plicae circulares) in the wall, finger-like villi projecting from the mucosa, and microscopic microvilli (the brush border) on each epithelial cell. Together these greatly multiply the absorptive surface available for nutrient exchange.

Question 3

How are fats absorbed in the small intestine?

Accepted Answer

Because fats are not water-soluble, fatty acids and glycerol are first bundled into micelles with bile salts. They diffuse into the epithelial cells, are re-formed into triglycerides, coated with proteins to form chylomicrons, and released into the lacteal — entering the lymph rather than the blood capillaries.

Question 4

What is a chylomicron?

Accepted Answer

A chylomicron is a lipoprotein particle assembled inside intestinal epithelial cells: a core of re-formed triglycerides (plus fat-soluble vitamins) surrounded by a protein coat. Chylomicrons are too large for blood capillaries, so they are transported into the lacteal and travel through the lymph.

Question 5

Where does most absorption occur in the human digestive system?

Accepted Answer

Most absorption occurs in the small intestine. The large intestine absorbs water, some minerals and certain drugs; the stomach absorbs very little (some water, alcohol and a few drugs); and essentially no absorption takes place in the mouth.

Villi Absorption Lab — How a 6-Metre Tube Gets a Massive Surface

Practice

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