2.6c absorption of materials

they hold the airways open at all times

the diffusion of oxygen from an area of high concentration in the lungs to an area of low concentration in the red blood cells and the diffusion of carbon dioxide from an area of high concentration in the blood to an area of low concentration in the lungs.

• large surface area (millions of alveoli)-rapid diffusion of gases • thin walls(one cell thick) - rapid diffusion of gases • good blood supply (network of millions of capillaries) - products of diffusion are carried away quickly • they are moist (thin layer of water) - allows the oxygen to dissolve

the alveoli

• trachea • bronchus • bronchiole • alveoli

hair-like cells that have upwards in a wave like motion to move trapped germs and dirt away from the lungs.

the airways are lined by cells that produce mucus that traps microorganisms, dust and dirt. cilia move the trapped dirt, dust and microorganisms away from the lungs.

to absorb the products of carbohydrate digestion (glucose) and protein digestion (amino acids)

to absorb the products of fat digestion (fatty acids and glycerol)

• millions of villi - large surface area for rapid diffusion of food molecules into the villi • good blood supply - transport the food molecules rapidly around the body. • thin lining-the walls of the villi are only one cell thick-allows rapid diffusion

• the movement of food through the digestive system • occurs along the length of the alimentary canal and not just the oesophagus • the muscles behind the food contract and the muscles in front of the food relax

to absorb the food molecules into the blood stream

the breakdown of large, insoluble food molecules into small, soluble food molecules by enzymes.

because only small, soluble food molecules can dissolve and diffuse through the wall of the small intestine and enter the blood