What is the digestive system?
An organ system in which several organs work together to digest and absorb food.
What organs is the digestive system made up of?
Salivary glands, stomach, liver, pancreas, small intestine and large intestine.
What do the salivary glands do?
Produces digestive juices.
What does the stomach do?
Digests food.
What does the liver do?
Produces bile which helps the digestion of lipids (fats and oils).
What does the pancreas do?
Produces biological catalysts called digestive enzymes which speed up the digestive reactions.
What does the small intestine do?
Digests food and absorbs soluble food molecules, e.g. glucose.
What does the large intestine do?
Absorbs water from undigested food, leaving faeces.
List stages of digestion.
- Food is digested in mouth, stomach and small intestine
- Digested food is absorbed into bloodstream in the small intestine
- excess water is absorbed back into the body in the large intestine
- any undigested food passes out of the anus as faeces
What are the processes that happen in the digestive system?
Ingestion (eating) - digestion (breaking down) - absorption - egestion (removal from body)
What happens during absorption?
Digested food molecules are absorbed in the small intestine - they pass through the walls of small intestine and into our bloodstream. The digestive food molecules are carried around the body to where they are needed.
How is the small intestine adapted for absorption?
- has a thin wall (one cell thick)
- has many tiny villi to give a really big surface
What happens during egestion?
Excess water is absorbed back into body in the large intestine. Undigested food is left then, stored in rectum, and comes through anus as faeces.
Why are bacteria in the digestive system important?
- can digest some substances that humans can’t (e.g. certain carbohydrates)
- reduce size of harmful bacteria multiplying and causing disease
- produce some vitamins that humans need - vitamins B and K
What does bile do?
Produced in the liver, stored in the gall bladder before released into the small intestine. Alkaline to neutralises HCl from the stomach.
Emulsifies fat to form small droplets which increases the surface area.
Alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
