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Do now! In pairs can you discuss what a “balanced diet” is? Bunny suicide #4 Last lesson • Components of a balanced diet What did you eat yesterday? • Stick in the sheet “What food contains” • Put the title “What I ate yesterday” in your books • Think carefully and write a list of everything you ate and drank yesterday. Include quantities. • Read pages 6 and 7 of your book. • Write 3 sentences explaining if you had a balanced diet yesterday (or not!) The digestive system Today’s lesson A long tube! We can think of the digestive system as if it were a long tube Breaking up of food During its journey down the tube, food is gradually broken down into smaller parts until it can be absorbed by the blood. This is called digestion. The journey begins in the mouth Ingestion Putting food into the mouth is called ingestion (feeding). Teeth The incisors help us to bite the food into large chunks the food Teeth The molars help to grind the food into even smaller pieces. Saliva Salivary glands produce saliva which makes the food moist and easier to swallow Saliva Saliva also contains enzymes, which are chemicals which break down the food chemically. Gullet/oesophagus/food pipe The gullet is a tube with a muscular wall that squeezes the food into the stomach Gullet/oesophagus/food pipe To show that this is true you can try drinking water whilst standing on your head! Gullet/oesophagus/food pipe It takes around 10 seconds for food to travel from the mouth to the stomach Stomach The stomach is a stretchy muscular bag which mixes the food with hydrochloric acid and pepsin, an enzyme which helps to digest protein molecules Stomach The stomach churns the food for about 2 – 4 hours Small intestine The stomach squirts food into the small intestine. Small intestine Here food is mixed with digestive juices from the liver and pancreas. Small intestine Bile from the liver breaks up fat. Small intestine Pancreatic juice neutralises the stomach acid and contains enzymes that digest carbohydrates, proteins and fats. (small intestine) Small intestine As food passes along the long tube of the small intestine, its molecules become small enough to be absorbed into the blood through the intestine walls. Surface area The lining of the small intestine has a large surface area to help this to happen. villi Small intestine The small intestine is about 6.5 metres long and food spends up to 6 hours here. Large intestine The large intestine absorbs water from what remains of the food. Large intestine Semi-solid (if you’re lucky!) faeces are formed after 12-36 hours in the large intestine. Rectum Faeces are stored in the rectum until there is a convenient moment to get rid of them! Anus They exit through your anus. This is called egestion. Peristalsis Throughout its journey, the food is squeezed down the digestive system by muscular walls in a process called peristalsis. Role play?! Draw the sentence!