Digestive System

1. Digestive System D. Crowley, 2007

2. Digestive System • To be able to label the digestive system, and explain the function of each part

3. Organs • You tasks is to discuss, then list the organs you believe play a role in digestion • Lots of organs play a role in digestion, including: - • Mouth • Stomach • Intestines • Anus • (+ liver and pancreas (although food does not pass through these)) • (*appendix helps digest cellulose in some animals, but has no real use in humans)

4. Digestive System • The food we eat has to be broken down into a form that our bodies can use - this is digestion • Digestion is needed to absorb food into our bodies - obtaining as many nutrients from the food as possible • Digestion happens in the digestive system, beginning at the mouth and ending at the anus • After we swallow, food passes through these organs: - • Oesophagus (gullet or food pipe) • Stomach • Small intestine • Large intestine

5. Digestive System • Using your worksheet, and exploring science 8 (page 10) label the digestive system • Then, in your book make a list of the key parts of the digestive system, and add some key information about them Mouth Salivary gland Oesophagus (gullet or food pipe) Small intestine Stomach Large intestine *Appendix Rectum & anus

6. Digestive System Mouth - putting food in your mouth is called feeding or ingestion. Teeth grind the food down, and saliva (produced from salivary glands) help make the food moist, easing swallowing (as well as the enzyme amylase which helps break down starch) Mouth Salivary gland Oesophagus (gullet or food pipe) Oesophagus (gullet) - when you swallow, the trachea (windpipe) is shut off, and food passes down the oesophagus. Muscles in the wall above the food contract, making the piper narrower above the food, pushing it down (this is why you can eat, even when upside down)! Small intestine Stomach Large intestine *Appendix Stomach - food is churned up with the strong acid (pH 1-2) Rectum & anus

7. Digestive System Small intestine - small molecules are absorbed through the small intestine wall Mouth Salivary gland Large intestine - food which we cannot digest (e.g. fibre) is passed into the large intestine, where water is removed. This forms a more solid material - faeces Oesophagus (gullet or food pipe) Small intestine Stomach Large intestine Rectum & anus - faeces is stored in the rectum, eventually being pushed out of the anus - faeces is egested *Appendix Rectum & anus *Appendix - in some animals, helps to break down cellulose, but no known use in humans

8. Digestive System • Digestion involves some key organs: mouth; oesophagus; stomach; small and large intestines etc… • However some organs play a vital role in digestion, even though food does not pass through them: - • The liver produces bile helping with the digestion of fat • The pancrease produces chemicals called digestiveenzymes, which help break down food molecules • Any undigested food passes out of the anus as faeces Digestive System

9. Cows • Why is it that cows have 4 stomachs? • Cows, goats, sheep and several other animals belong to a class of animals called ruminants. Ruminants have four stomachs and digesting their food in these stomachs, rather than in their intestines. • Ruminants eat food, regurgitate it as cud and eat it again. The stomachs are filled with bacteria that aid in digestion • This is all because its difficult to break the grass down and absorb the nutrients (cellulose cell walls). It takes a long time to ‘process’ this food, which is why they have four stomachs!

10. Rabbits • Why do rabbits eat their ‘poo’?! • This is a similar situation for the rabbits as it was with the cows - its difficult to get all the nutrients from the grass, as the cell wall (cellulose) is difficult to break down • For this reasons rabbits re-ingest their excrement, helping get all the nutrients within • In other words, the eat their poo to get a second shot at absorbing all the nutrients they passed out first time