Health and Social Care Unit 16 Ao1 Digestive System

The Digestive System

What is digestion?

Digestion is the process by which food and drink are broken down into their smallest parts so the body can use them to build and nourish cells and to provide energy.

Why is digestion important?

When you eat your food, it is not in a form that the body can use as nourishment. Food and drink must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body.

Digestion involves mixing food with digestive juices, moving it through the digestive tract, and breaking down large molecules of food into smaller molecules. Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine.

The Mouth

Once food is in the mouth, the taste buds begin determining the chemicals within the food thru their nerve endings, in order to give you the taste sensations of salt, sweet, sour or bitter.

As your teeth chew and grind the food, breaking it down, it's mixed with saliva. This contains many enzymes including salivary amylase, which begins to break down the long chains of starch found in foods (such as bread, cereals, pasta and potatoes) Saliva also contains mucin, which moistens the food so it can pass easily through the digestive (gastrointestinal) tract.

The Oesophagus

After the food has been swallowed, it's carried down the oesophagus (a muscular tube) towards the stomach. The oesophagus can contract and relax in order to propel the food onwards.

The stomach

The stomach is a sack made of muscle, and when it's empty, it has a volume of only 50ml but this can expand to hold up to 1.5 litres or more after a meal.

The walls of the stomach are made of three different layers of muscle that allow it to churn food around and make sure it's mixed with the stomach's acidic digestive juices. The presence of hydrochloric acid in the stomach prevents the action of salivary amylase and helps to kill bacteria that...