Wikijunior:Human Body/Anatomy

Anatomy describes the composition and relationships of parts of our body. Just describing how our body is composed of many parts helps us guess and memorize functions of our body. Anatomy is what this book is mostly about and it is fascinating to see how well our body is designed. Anatomy deals with organs or groups of organs. An organ is a distinct part of our body with a function, for example our heart. Anatomy of the movement apparatus (all organs that are involved in movement), for example, deals with muscles, bones and tendons. Groups of organs such like this are also called organ systems.

How to approach an organ?
If you learn about the anatomy of an organ or an organ system, you will soon notice that you can look at an organ from afar and also very close up. If you go to extremes you use a microscope to look at single cells of an organ. All organs are made from cells. Therefore we will understand a lot about an organ by both looking at it with the naked eye - which we will call the macroscopic view - and at cells - which we call the microscopic view. In the individual descriptions of organs you will therefore find both macroscopic and microscopic aspects of that organ.

We now list some subtopics of anatomy and where you can find more information about those organs in this book.

There are many different types of organs such as the heart, liver, brain etc.

Movement apparatus
The movement apparatus deals with the organs needed for movement: bones, muscles and tendons. While we often think of movement in terms of walking, climbing, or moving our mouths to talk, movement goes on inside of us as well. For example, our digestive systems use muscles in organs to transport food through the digestive process. Likewise, movement inside of our bodies by the diaphragm allows us to take in air from our surroundings.

Circulatory system
The so called circulatory system involves everything that keeps our blood in order and flowing. Organs are blood vessels, heart, bone marrow and the spleen. The liver also takes part in keeping our blood healthy, but it has many more functions, too. The lungs help in the purification and oxygenation of blood.

Respiratory system
The respiratory system allows us to breathe in order to take in oxygen. This involves the mouth, epiglottis, trachea and the lungs. The respiratory system closely interacts with the circulatory system, because one important function of the blood is to transport oxygen. The heart acts like a pump circulating all the clean blood to different parts of the body and pumps the impure blood for purification to the lungs. The main function of lung is exchange of gases i.e. transport of carbon dioxide and oxygen. There is a specialised network of pulmonary capillaries which carries out gases exchange across the alveoli. Oxygen enters pulmonary capillaries from alveoli and carbon dioxide enters into the alveoli from pulmonary capillaries. This exchange of gases occurs because of pressure gradient across the alveoli and pulmonary capillaries. Alveoli is the functional unit of lung.

Digestive system
Have you been hungry recently? Our digestive system deals with all the food we take in. Food travels from the mouth through the esophagus to the stomach. From there, the small intestine and the large intestine actually absorb nutrients (the small components in our food that our body can make use of) and water. Finally, faeces is excreted through the anus.

Urinary system
The urinary system we only feel when we urinate, or when we have an urge to do so. The kidneys are a filter that cleanses the blood. Also, if we drink more fluid than we need, excess fluid is transported through the kidneys as urine to the bladder. Since unhealthy substances are excreted through the urine, you can see that drinking enough fluid helps keep you healthy.

Reproductive system
The reproductive system differs between men and women. These organs are needed for a couple to have children. A baby is carried by a woman in the uterus. The special organ of the placenta is formed during pregnancy and is shared between mother and child who feeds through this organ.

Nervous system
The nervous system is composed of the brain, medulla and nerves. The nervous system contains our consciousness and we use our nervous system to control the rest of our body.

Other organs
The liver is a very important organ, producing many substances that other cells need. It plays an important part in collecting the digestive products with juices that aid digestion. It also stores energy (glycogen) which can be turned into quick form of energy (glucose). In this way the organ plays a major role in providing instant energy to supply important organs.

It is very important to remember that cutting off glucose and oxygen to the brain can make a person unconscious in 3 minutes. Thymus, spleen and tonsils in children help the immune system to defend against bacteria and viruses.

The largest organ on the human body is the epidermis, also known as our skin.