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.


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.

Watch the video for Sonia's story about heart donation.

Sonia, an organ donor recipient, describes how heart donation improved her life

Activity - organs of the human body

Organs Quiz

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