biology - human nutrition (digestive system)

Identify in diagrams and images the main organs of the digestive system

Describe the functions of the organs of the digestive system

1. ingestion – the taking of substances, e.g. food and drink, into the body

• teeth: physically break down food and increases surface area so it’s easier for enzymes to break it down

• salivary glands: release saliva which contains amylase and digests starch into maltose

• oesophagus: contractions of the walls of the oesophagus force the food downwards; this is peristalsis

2. digestion – the breakdown of food

• stomach: contracts muscular walls, protease enzymes break down proteins into amino acids, and hydrochloric acid is produced which kills bacteria

• pancreas: amylase, protease and lipase enzymes are produced

• liver: bile is produced

• gallbladder: releases bile into the small intestine (neutralises acid from stomach and emulsifies lipids)

3. absorption – the movement of nutrients from the intestines into the blood

• small intestines: acidic stomach contents are neutralised by bile, and it is covered in villi which have a huge surface area for diffusion and have a single layer of surface cells

assimilation – uptake and use of nutrients by cells

• large intestine: absorbs most of excess water, solid left forms faeces

• rectum: faeces are stored here

egestion – the removal of undigested food from the body as faeces

• anus: faeces leave the body

Classes of enzymes

investigating energy content in food (practical)

1. weigh food sample

2. place 20cm³ of water in a boiling tube

3. measure temp of water

4. light food and hold under boiling tube

5. continue until it no longer burns

6. stir water and measure final temp