Human Nutrition Part 2

Digestive system (relating to digestion)

Organs of digestive system

Mouth, oesophagus, stomach, small intestine and large intestine.

Organs that dont form part of the route but are involved with digestion.

Salivary glands, pancreas, liver and gall bladder.

What is ingestion

Food and drink are taken into the body through the mouth.

Mechanical digestion

Food is broken down into smaller pieces without a chemical change to the food molecules.

Chemical digestion

Large, insoluble molecules are broken down into small soluble molecules.

Absorption

Small food molecules and ions move through the wall of the intestine into the blood.

Egestion

Food that has not been digested or absorbed passes out of the body as faeces.

Mouth

Food is ingested here, and the teeth break food into smaller pieces during mechanical digestion.

Salivary glands

Saliva is secreted into the mouth. The enzyme amylase in the saliva begins to digest starch into maltose. Saliva lubricates the food for easy swallowing.

Oesophagus

The tube connects the mouth to the stomach; contractions of the walls of the oesophagus force the food downwards.

Stomach

The stomach mechanically digests food through churning and begins protein digestion with protease enzymes. Hydrochloric acid creates an optimal pH for these enzymes and kills pathogens.

Liver

Bile is produced here. Bile aids the digestion of fats, as well as neutralising stomach acids as it exits the stomach.

Small intestine: ileum

Food and water are absorbed into the blood through villi in the lining of the ileum.

Large intestine: Colon

Remaining water is absorbed from food into the blood, and the solid waste left behind in the colon forms faeces.

Large intestine: rectum

Faeces are stored here prior to egestion.

Large intestine: Anus

Faeces leave the body through the anus; this process is known as egestion.