The Human Digestive System — Revision notes

Digestive system

A roughly nine-metre-long tube running through the body that breaks food down into tiny nutrients small enough to enter the blood

Mouth

Where digestion begins — teeth cut and grind food, the tongue mixes it, and salivary glands release saliva to soften it

Oesophagus

The muscular tube connecting the mouth to the stomach that uses peristalsis to push food downward

Peristalsis

Waves of muscular squeezing that push food along the digestive tract regardless of gravity

Stomach

A stretchy bag that holds food and releases hydrochloric acid to break it down and kill germs

Hydrochloric acid

A strong chemical secreted by the stomach to break apart food and kill harmful germs

Small intestine

The longest part of the digestive system (around 6 metres), where most digestion and nutrient absorption happens

Villi

Millions of tiny, finger-like bumps lining the inside walls of the small intestine that maximize surface area for nutrient absorption

Gland

A part of the body that makes and releases chemicals

Pancreas

A gland that makes digestive chemicals and releases them into the small intestine, without food ever passing through it

Liver

An organ that produces bile and sends it into the small intestine to help digest fats

Bile

A liquid made by the liver that breaks fats into tiny droplets, giving lipase enzymes a bigger surface to work on

Fibre

An undigestable part of food that bulks up waste and keeps it moving through the digestive system

Large intestine

The organ responsible for pulling water back out of unabsorbed waste to firm it up before it reaches the rectum

Rectum

Where faeces is stored until it leaves the body

Anus

A ring of muscle that controls the exit of faeces from the body

What this lesson covers

How well do you know each one? Be honest: red means go back over it.

• Explain why the body needs food and why it must be broken down firstNot yetSort ofGot it
• Name the organs of the digestive system in the order food passes through themNot yetSort ofGot it
• Describe how the oesophagus moves food using peristalsisNot yetSort ofGot it
• Explain how the stomach and small intestine are adapted to their jobs, including villiNot yetSort ofGot it
• Describe the roles of the pancreas, liver and bile in digesting fatsNot yetSort ofGot it
• Explain what the large intestine does and why fibre matters even though it isn't digestedNot yetSort ofGot it

Test yourself

Cover the answer, say it out loud, then check the full quiz on the lesson page.

• Straight after the stomach, where does food go next?
• Which of these does food NOT pass through?
• Which part pulls water back out of your waste?

Topic quiz

12 questions on this topic only — not mixed with anything else, one at a time.

Spelling challenge

Read the definition, then type the correct spelling of the term. Uses the same terms as above.