tissue, organs, systems

• cells are specialised to carry out different functions
• different types of tissues work together as organs
• a system is a group of organs that work together for a common purpose
• four basic types of tissue : epithelial, connective, muscular, nervous
• epithelial tissue is a covering or lining tissue

  
• epithelial tissue is found in the inside and outside of organs like the heart, kidneys, intestine and lungs
• cell that make up epithelium are very closely joined together
• epithelium cells vary in shape
• connective tissue provides support for the body and helps to hold all the body parts together
• connective tissue cells are not close together and are separated from each other by a large amount of material that is not made of cells, called matrix
• connective tissue includes blood, bone, cartilage, tendons and ligaments
• muscular tissue are long and thin and can contract to become shorter
• three types of muscular tissue : skeletal, smooth, cardiac
• smooth muscle does not have striations, cannot be contratcted voluntarily, and are in the walls of the stomach, intestine, blood vessels and in the iris.

  
• cardiac muscle makes up most of the heart, when the heart muscle contracts, it pumps blood

  
• skeletal muscles make up muscles that are attached to bones, they can be voluntarily moved and have striations

  
• nervous tissue is made of specialised nerve cells called neurons, which have projections that carry messages when the neuron is stimulated, it is found in the brain, spinal chord and nerves
• organs are body structures that are made up of two or more types of tissue. the tissues of an argan work together to carry out particular tasks
• organs have distinct shapes and some have smaller organs within. for example the skin has sweat glands, hair and nerves
• various organs are organised into systems. systems are a group of organs that work together to carry out a particular task
• digestive

  ingestion, breakdown and absorption of food
• respiratory

  intake of oxygen and removal of carbon dioxide
• circulatory

  transport of nutrients, oxygen and wastes to and from cells
• excretory

  removal of waste
• nervous

  detection of changes in the environment and coordination of body activities
• endocrine

  regulation and coordination of many body functions
• skeletal

  support and protection of body parts
• muscular

  movement and support
• immune

  protection against infection by micro-organisms
• reproductive

  production of new individuals
• all body systems work together to meet the needs of a functioning organism. no system can work in isolation