How are cells organised?

• Cell = specialised for a particular function e.g. muscle cells
• Tissue = A group of specialised cells working together to carry out a function e.g. muscle cells in muscle tissue
• Organ = A group of tissue working together to carry out a function e.g. muscle, nerve and epithelium work together in the heart
• Organ system = a group of organs working together to carry out a particular function e.g. digestive system