Biology 1.3 The Digestive System

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