What are the organs of the human body?

  • An organ is a group of different tissues that work together to do a particular job.

  • Organs are grouped together into organ systems.

  • Examples of organ systems include the circulatory system and the digestive system.

A specialist nurse explains her knowledge of organs and organ systems

Layers of organisation

The human body is made up of many cells, so it is an example of a multicellular organism. A multicellular organism has five layers of organisation, called a hierarchy. Here they are in order of complexity:

  • Organelles - tiny structures which carry out various functions within a cell.
  • Cells - the basic unit of all living organisms.
  • Tissues - groups of similar cells that work together to perform a specific function. For example, brain tissue, muscle tissue and heart tissue.
  • Organs - different tissues working together to carry out a particular function.
  • Organ system - a group of organs that work together to do a job.

Organs

In an organ, different tissues work together to carry out a particular function. These are the main organs, as well as their primary function:

  • The brain controls thoughts, memory and other organs.
  • The heart pumps blood around the body.
  • The lungs separate oxygen from the air and remove carbon dioxide from the blood.
  • The stomach helps to digest food.
  • The intestines absorb nutrients from food.
  • The liver removes poisons from the blood.
  • The kidneys filter blood and produce urine.
  • The bladder stores urine.
  • The skin protects and contains the other organs.

Organ systems

Organs are organised into organ systems. An organ system is a group of organs that work together to do a job.

Key human organ systems:

  • The circulatory system includes the heart, veins and arteries. Its function is to transport substances in the blood, around the body.
  • The respiratory system includes the nose and the lungs. It takes in oxygen and removes carbon dioxide.
  • The digestive system includes the stomach and intestines. It breaks down food and absorbs nutrients.
  • The reproductive system includes the uterus and vagina in women, and the penis and testes in men. Its function is to create offspring.
  • The musculoskeletal system includes bones and muscles. It supports the body and allows movement.
  • The immune system includes bone marrow. It protects the body from infection.

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Activity - organs of the human body

Organs Quiz

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