Digestive system

What are the 2 main roles of the human digestive system?

1. Digestion

2. Absorption

1. Starch

2. Protein

3. Lipids

are broken down into:

1. simple sugars (Glucose & Maltose)

2. Amino acids

3. Glycerol + fatty acids

1. Starch

2. Protein

3. Lipids

are broken down by:

1. Amylase

2. Protease

3. Lipase

What do we absorb back into the bloodstream?

1. Glucose

2. Amino acids

3. Glycerol + fatty acids

4. Vitamins

5. Minerals

6. Water

What happens in the mouth?

1. The teeth physically break down the food to increase the surface area for enzymes and to make it easier to swallow

2. the salivary glands release saliva which lubricates the food for swallowing and contains amylase, which breaks down starch into simple sugars

What does the food pass through to get to your stomach?

Oesophagus

What happens in the stomach?

1. the walls contract to mix the contents and move the food

2. produces pepsin which breaks down protein into amino acids

3. produces HCl which kills bacteria and provides the right pH for enzymes

What happens before food enters the small intestine

Before food enters the small intestine, the pancreas releases pancreatic fluid and the gallbladder releases bile

What are pancreatic juices?

a mixture of amylase, protease and lipase

What is bile and what does bile do?

1. Neutralises the HCl from the stomach as it’s an alkali

2. Emulsifies fats, which gives them a larger surface area

3. Stored in the gallbladder but made in the liver

What happens in the small intestine?

1. The food is fully digested by carbohydrase, lipase. lactase and protease

2. Absorbed by villi

what are Villi?

Small projections in the wall of the intestines, with a large surface area for diffusion, a single layer of surface cells for short diffusion distance, small microvilli to further increase surface area, and a good blood supply to maintain the concentration gradient

What happens in the large intestine?

Most of the excess water is absorbed

What happens in the rectum & anus?

The leftover mixture, called faeces, is stored in the rectum, until ready to release from the anus