cell organisation 2.1

• cells are the building blocks of all living organisms
• the process by which cells become specialised is called differentiation
• differentiation occurs during the development of a multicellular organism
• large multicellular organisms have different systems inside them for exchanging and transporting materials
• a tissue is a group of similar cells that work together to carry out a particular function
• a tissue can include more than one type of cell
• in mammals, examples of tissues include:

  • muscular tissue, which contracts to move whatever its attached to
  • glandular tissue, which makes and secretes chemicals like enzymes and hormones
  • epithelial tissue which covers some parts of the body, eg the inside of the gut
• an organ is a group of different tissues that work together to perform a certain function
• an example of an organ is the stomach which consists of:

  • muscular tissue, which moves the stomach wall to churn up the food
  • glandular tissue which makes digestive juices to digest food
  • epithelial tissue, which covers the outside and inside of the stomach
• an organ system is a group of organs working together to perform a particular function
• an example of an organ system is the digestive system which is made up of:

  • glands which produce digestive juices
  • the stomach and small intestine which digest food
  • the liver which produces bile
  • the small intestine which absorbs soluble food molecules
  • the large intestine which absorbs water from undigested food which leaves faeces
• organ systems work together to make entire organisms