Chapter summary

The whole chapter in one list.

• Digestion breaks large, insoluble food molecules into small, soluble ones the body can absorb.
• Digestion begins in the mouth, continues in the stomach and is completed in the small intestine, where the end products are absorbed through the villi.
• The large intestine absorbs water; undigested matter leaves as faeces.
• Respiration happens in three stages: external respiration, gas exchange in the alveoli and cellular respiration.
• Gases cross the thin, moist walls of the alveoli by diffusion.

• Anaerobic respiration makes ethyl alcohol in plants and yeast, and lactic acid in animals, and releases less energy.
• The kidneys excrete by ultrafiltration, selective reabsorption and secretion in the nephrons.
• Blood is plasma (about 55%) and cells (about 45%): red cells carry oxygen, white cells defend, platelets clot.
• The four-chambered heart drives a double circulation: to the lungs and to the body.
• Normal adult blood pressure is about 120/80 mm Hg.
• The nervous system co-ordinates quickly by impulses; hormones co-ordinate more slowly through the blood.
• A reflex action is a quick, automatic response travelling along a reflex arc.
• Homeostasis keeps blood glucose, body temperature and water steady.