National 5 Biology 2.7 Absorption of materials

Features of an exchange surface

large surface area, thin walls and extensive blood supply

Absorption

taking up substances by cells

Alveoli

tiny air sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses out

Capillary network

highly branched network of tiny blood vessels having a large surface acting as an exchange surface

Digestion

breakdown of large insoluble food molecules into smaller soluble ones

Fatty acids and glycerol

products of fat digestion absorbed into the lacteal

Lacteal

central part of the villus where the products of fat digestion (fatty acids and glycerol) are absorbed

Lungs

organs where gas exchange occurs (absorption of oxygen and desorption of carbon dioxide

Small intestine

long tube like part of the digestive system with highly folded inner surface where most of the nutrients are absorbed

Villi

tiny finger like projections lining the small intestine giving a large surface area for absorbing the products of digestion

Villi capillaries

absorb glucose and amino acids