The human body

Key points

  • Please note: this section contains links to websites that explain and illustrate the human reproductive (or genital) system.
  • The human body is a complex system that needs to be understood and cared for.
  • It includes sensory organs and the respiratory, circulatory (cardiovascular), digestive, urinary, muscular, skeletal, nervous, integumentary (skin), immune, endocrine and reproductive systems.
  • School A to Z features links to third-party websites and resources. We are not responsible for the content of external sites.

X-ray simulation of human lungs


Sensory organs

Traditionally, there are five senses: sight, smell, taste, touch and hearing. Each of the five senses consists of organs which have a special way of receiving information and passing this information on to the brain. Sight is probably the most developed sense in humans, followed closely by hearing.

Respiratory system

When air is breathed into the lungs, oxygen is absorbed into the blood, providing energy to body cells. 


Circulatory or cardiovascular system

Your circulatory system consists of your heart and blood vessels. These provide blood - full of oxygen and nutrients - to all parts of your body. Arteries carry blood away from the heart; veins return blood to the heart.


Digestive system

Your digestive system breaks down food so your body can use it to build and repair cells, and for energy. The digestive system includes your throat, stomach, small intestine, liver, gallbladder, pancreas and large intestine. Each of these parts has a role in the digestion and absorption of energy and nutrients.

Urinary system

Within the urinary system, the kidneys filter out waste products from the blood and this is combined with water to create urine. The urine is excreted out of the body.

Muscular system

You have more than 600 muscles in your body. Some of them help you move and lift, some of them help you to digest food and some of them keep your heart beating.

Skeletal system

The adult human body has 206 bones which protect and move the body.

Nervous system

Your central nervous system comprises of your brain and spinal cord. Through the spinal chord and a network of nerves throughout your body, your brain is able to control your body's activities and also receive information.

Skin (integumentary system)

Your skin is the largest organ of the body. It is made up of a thin outer layer (called the epidermis) and a thicker outer layer (called the dermis).

Lymphatic and immune system

The lymphatic system is responsible for the removal of excess fluid from the body and for the production of immune cells. The lymphatic system works with the immune system, which protects the body against disease.

Endocrine system

Your endocrine system is a collection of glands that produce hormones to regulate your body's growth, metabolism, and sexual development and function.

Reproductive system

The reproductive system or genital system is a system of organs within the body which work together for the purpose of reproduction. In humans, the male and femal reproductive systems are different.

More information


This site uses Google Translate, a free language translation service, as an aid. Please note translation accuracy will vary across languages.

Doing it by the book

As a parent it's only natural to want to help your child, but when it comes to homework and study, the completed work should be theirs.

Here are some important points to remember to ensure your child is following good practice for a lifetime of learning.