absorption of materials

• we need oxygen , nutrients and food for respiration
• normally have large surface area , extensive blood supply , thin walls to make them efficient at gas exchange
• wate materials like co2 need to be removed from the cell
• lungs are gas exchange organs
• the trachea has goblet cells to produce mucus to trap foreign materials , cillia brush the mucus up and out
• alvieoli are have thin and moist walls with a large surface area , oxygen diffuses out the alveoli and co2 diffuses in
• digestion is the breakdown of large insoluble molecules into small soluble particles , carried out by enzymes
• villi line the small intestine walls they have large surface area and thin walls and there is lots of them
• in villi blood capillaries absorb glucose and amino acids and the lacteal absorbs glycerol and fatty acids