MEPX
Chapter 2 of 14All chapters
  1. 1How the body is organised
  2. 2Cells and tissues
  3. 3The skeleton
  4. 4Muscles
  5. 5Heart and circulation
  6. 6Blood
  7. 7Lungs and breathing
  8. 8Digestion
  9. 9Kidneys and liver
  10. 10The nervous system
  11. 11The brain
  12. 12Hormones
  13. 13Skin and senses
  14. 14The immune system

Chapter 2 of 14

Cells and tissues

The unit everything is built from.

Inside a cell

A membrane holds the contents, the nucleus stores DNA, and mitochondria release energy from glucose. Ribosomes build proteins from the instructions the DNA supplies.

  • Red blood cells are unusual: they drop their nucleus to carry more oxygen.
  • Nerve cells can be a metre long, while most others are microscopic.

Four tissue types

Epithelial tissue covers surfaces, connective tissue supports and joins, muscle contracts, and nervous tissue signals. Every organ is a mixture of the four.