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Identify the structures of the digestive system
Name the three processes that occur in the digestive system
Digestion Absorption Egestion
What is the function of the mouth?
Food is chewed and broken down into smaller pieces - mechanical digestion Amylase in the saliva breaks down starch into maltose
What is the function of the oesophagus?
Carries food to the stomach
What is the function of the stomach?
Secretes protease which breaks down proteins into amino acids Contains hydrochloric acid which kills any bacteria present in the food
What is the function of the pancreas?
Secretes carbohydrase and lipase which are transported to the small intestine
What occurs in the small intestine?
Digestion is completed: Carbohydrase breaks down carbohydrates into simple sugars Proteases break down proteins into amino acids Lipases break down lipids into fatty acids and glycerol
Food molecules are absorbed into the bloodstream
Describe how the small intestine is adapted for the absorption of food molecules
Surrounded by a network of capillaries which provide a good blood supply, maintaing a high concentration gradient Many villi (in walls of small intestine) and microvilli (in walls of villi) to increase the surface area for absorption Walls of villi one cell thick giving a short diffusion distance
What is the function of the large intestine?
Reabsorbs water into the bloodstream
What is the function of the liver?
Produces bile
What is the function of the gallbladder?
Stores bile prior to its release into the small intestine
What is the name of the tube that transports bile form the gallbladder to the small intestine?
Bile duct
What is bile?
A liquid secreated by the liver that aids digestion of lipids in the small intestine
Describe the two main functions of the bile in the small intestine
Neutralises acid from the stomach to provide optimum conditions for enzymes in the small intestine Emulsifies lipids, providing a grater surface area for lipases to digest them
How is food moved through the digestive system?
By peristalsis
Describe the process of peristalsis
Wave of muscle contracts behind the food & forces it down the gut
What is the function of the rectum?
Stores faeces prior to egestion
What process occurs via the anus?
Egestion
What is egestion?
The removal of undigested waste material from the body
How can the gut be modelled?
Using visking tubing
Describe the limitations of the visking tubing model
