How Do We Digest Our Food???

1. How Do We Digest Our Food??? • Digestion is a continuous process occurring in the mouth, progressing through the digestive tract and ending at the anus. • The process of digestion can be either mechanical, involving the use of grinding structures; such as strong muscles and teeth, or chemical involving enzymes secreted along the gut.

2. How Do We Digest Our Food???

3. How Do We Digest Our Food??? • Digestion aims to breakdown complex organic molecules in food into smaller less complex units that are able to rapidly diffuse across the lining of the small intestine into the bloodstream. • What cannot be digested or broken down by mechanical and chemical digestion is eliminated as faeces

4. How Do We Digest Our Food??? • Bile, secreted from the gall bladder, aims to decrease the size of lipid molecules so as to increase the surface area exposed to lipase and therefore increase enzymic activity.

5. How Do We Digest Our Food??? • Enzymes are like a lock and key where a specific key will fit the lock to break the seal. • Each enzyme involved in digestion is limited to reactions with only one or very few types of good substances.

6. How Do We Digest Our Food??? • Once the food has been adequately broken down, the molecules of glucose, fructose, amino acids, and fatty acids are absorbed through the villi of the small intestine. • The villi are small and finger like in structure to optimise the rate of diffusion of organic molecules.

7. How Do We Digest Our Food??? • What food is not broken down, usually cellulose and fibrous based material passes through the bowel. • At this point water and vitamin K is absorbed. • Movement through the colon is much slower than through the small intestine. • Faeces are the end result of digestion.

8. How Do We Digest Our Food??? • Required macro and micronutrients are circulated around the body via a network of arteries and capillaries plus veins to all cells in order to provide them with the energy required for cellular respiration.

9. Linking digestion to circulation • Prior to going to the cells nutrients are transported to the livervia the hepatic portal vein where they are screened and sometimes converted. • Nitrogen is converted to urea before circulating again. • Glucose to glycogen • Amino acids to protein and glycogen • Vitamins and minerals are stored. • After being screened by the liver, nutrients are transported once again by the hepatic vein to the heart travelling through the left atrium and ventricle and finally via the aorta to the kidneys.