Cambridge O Level Biology · Syllabus 5090 · Human Nutrition
Lacteal
What is Lacteal?
A blind-ended lymph vessel running up the centre of a villus. It receives the products of lipid digestion — fatty acids and glycerol — after they have passed through the epithelial cells, and carries them into the lymphatic system, which is a different initial route from the blood capillaries that take up glucose and amino acids.
This definition is part of the Human Nutrition chapter in Cambridge O Level Biology.
Common mistakes with Lacteal
- “All nutrients enter the blood in the same way.” Why it is wrong Water enters by osmosis; glucose and ions enter by diffusion when a gradient allows and by active transport when it does not; the products of lipid digestion enter the lacteal, not a blood capillary. Write instead Name the process that fits the substance in the question, and say why that process is the one required.
- “A villus is a cell.” Why it is wrong A villus is a projection of the intestinal wall made of many cells, containing a capillary network and a lacteal. A single cell contains neither. Write instead "A villus is a finger-like projection of the wall of the small intestine, covered by an epithelium one cell thick."
Questions students ask about Lacteal
Is a villus a single cell?
No. A villus is a finger-like projection of the wall of the small intestine, made of many cells. Its outer covering, the epithelium, is one cell thick, and inside it are a dense network of blood capillaries and a central lacteal — none of which a single cell could contain.
What does the hepatic portal vein carry, and where?
It carries most of the molecules and ions absorbed in the ileum — glucose, amino acids, mineral ions and water — in blood, from the capillaries of the small intestine directly to the liver. It is unusual among veins because it runs from one capillary network to another instead of returning blood to the heart. The products of lipid digestion are the exception: they enter the lacteals and travel through the lymphatic system, joining the blood later.