Body systems

A body system is a collection of parts able to work together to serve a common purpose – growth, reproduction and survival.

Each part of a system depends on the other parts to perform tasks that can’t be achieved by single parts acting alone.

Each individual system works in conjunction with other systems to improve our chances of survival by maintaining a stable internal body environment. This stable environment is known as homeostasis.

An example of the way these systems are inter-related is the blood. It is part of the cardiovascular system and it carries products of digestion (digestive system) to body cells, excretory wastes (excretory system) to the kidneys and hormones (endocrine system) to target organs such as those forming part of the reproductive system.

Cardiovascular system
The heart and blood vessels make up this system. The heart is a pump forcing blood into a network of blood vessels allowing it to travel to organs and delivery sites requiring oxygen gas for respirationnutrients and the removal of waste substances.

Digestive system
This system resembles a long tube with attached organs. Ingested food is broken down into constituent nutrient molecules that are then absorbed into the bloodstream. Indigestible remains are then egested.

Endocrine system
Composed of a number of small organs distributed throughout the body, the endocrine system coordinates the metabolic activity of body cells by interacting with the nervous system. Endocrine glands produce hormones (chemical messengers) released into the blood and transported to target sites around the body.

Excretory system
The excretory system is composed of the kidneys (urine-forming organs), the bladder (temporary storage for urine) and channels for moving this liquid waste around. Kidneys are blood purifiers filtering liquid from the bloodstream, removing undesirable substances (such as toxins) and returning those still required to the blood.

Immune system
The immune system is a protection mechanism composed of specialised cells, cell products, tissues, organs and processes within an organism that protect against pathogens.

Integumentary system
Commonly known as the skin, this system wraps the body in a protective covering with a number of functions such as UV protection and temperature regulation, taking it well beyond being just a mere covering.

Musculoskeletal system
The skeleton provides a framework on which the human body is arranged. It is articulated to allow free movement in conjunction with the skeletal muscles. They control movement, posture and assist the body with heat generation. Our bodies are held together by connective tissue.

Respiratory system
Our bodies are made up of countless cells all requiring oxygen to carry out the important process of respiration. In this process cells use oxygen gas and produce carbon dioxide gas – a waste product that must be removed from the body. The process of breathing allows these gases to be exchanged between the blood and lungs.

Reproductive system
The human body has a system of organs that work together for the purpose of reproduction. The biological purpose of this process is the continuation of life.

Nervous system
The nervous system is made up of a network of specialised cells, tissues and organs that coordinate and regulate the responses of the body to internal and external stimuli.

Equipped with his five senses, man explores the universe around him and calls the adventure science.

Edwin Powell Hubble (1889–1953)

Our five senses make up a system within the nervous system. They are responsible for receiving information from the environment outside the body and relaying it to the brain for processing.

The nervous system is made up of two parts:

• The central nervous system (CNS) is made of the brain and spinal cord. It receives information and responds to it.
• The peripheral nervous system (PNS) is composed of the nerves extending from the brain and spinal cord to the rest of the body. The PNS is made up of a sensory part (made of nerve fibres carrying impulses to the CNS from sensory receptors found in the five senses) and a motor part (taking messages from the CNS to muscles, glands and organs).