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1 of 27 “Well, yeah, of course I’m impressed Frank, but strollers can’t be good for your digestion.” 2 of 27 What is Digestion ? The body carries out digestion of food to convert large insoluble food molecules into smaller soluble ones. Carbohydrate Protein Lipid Small food molecules can pass through the walls of the small intestine and then dissolve into the blood stream. Large food molecules cannot do this. 3 of 27 Digestive System a) Teeth 4 of 27 b) Tongue c) Salivary Glands d) Oesophagus e) Liver f) Gall Bladder g) Stomach h) Pancreas i) Small Intestine j) Large Intestine k) Rectum In the Mouth Digestion begins in the mouth where food is broken down by the teeth. This is called mechanical breakdown. The small parts of food are mixed with saliva and swallowed. 5 of 27 In the Mouth Saliva contains enzymes that start to chemically breakdown some of the starch and fats in the food. Enzymes are biological catalysts that speed up chemical reactions. 6 of 27 Enzymes in Action 7 of 27 Amylase and Starch Amylase breaks the long starch chains into glucose molecules. How long can you keep a piece of bread in your mouth? 8 of 27 Down to the Stomach Food then passes the epiglottis, a flap of skin and cartilage that prevents food from entering the trachea (air tube). 9 of 27 10 of 27 11 of 27 Down to the Stomach The food is moved down the oesophagus with the help of wave like contractions, a process called peristalsis. 12 of 27 In the Stomach The stomach is a hollow muscular sac with a variety of functions. a) b) c) 13 of 27 It stores masticated food. Produces acid and enzymes for chemical breakdown. Churns food before it moves on to the rest of the digestive system. The Journey So Far... 14 of 27 After the Stomach The contents of the stomach are then moved to the small intestine. Here, the content is mixed with bile and enzymes from the pancreas and intestinal walls. 15 of 27 Mmmmmm… Bile! Bile – a greeny-yellow substance excreted from the gall bladder which emulsifies fats to allow absorption, neutralizes the chyme. 16 of 27 Small Intestine The digestive enzymes chemically break down food particles. These nutrients are then absorbed into the blood stream though the wall of the small intestine. 17 of 27 Villi The walls of the small intestine are not smooth. They are covered in villi which increases the surface area 18 of 27 Large Intestine After the long trip through the small intestine, the remains enter the large intestine. Here remains are fermented by the action of gut bacteria, excess water is absorbed and faeces is stored until released. 19 of 27 Label the Diagram 20 of 27 Digestion Summary 21 of 27 22 of 27 23 of 27 Anagrams 24 of 27 Digestion Quiz 25 of 27