Organ Systems

Understanding the Eight Body Systems

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The musculoskeletal system as seen through the integumentary system. By Wunderfool / Getty Images

An organ system is a group of organs that work together to perform a complex function. There are eight organ systems in the human body. All of these are required for survival, either of the person or of the species.

Circulatory System

The circulatory system includes the heart and blood vessels (arteries and veins), as well as the blood itself. The circulatory system transports oxygen nutrients to all corners of the body and carries away byproducts of metabolism.

In order for blood to make it everywhere it needs to go, the circulatory system maintains the blood flow within a certain pressure range. Blood pressure that's too high puts undo stress on other organs and tissues. Low blood pressure means the blood--and its nutrients--won't make it to where it needs to go. High blood pressure kills you slowly while low blood pressure can kill you immediately.

Respiratory System

The respiratory system contains the lungs, trachea (windpipe) and all of the airways of the respiratory tree. It is responsible for breathing, which is the controlled movement of air in and out of the body (ventilation) and the movement of oxygen and carbon dioxide into and out of the bloodstream (respiration).

One of the least understood responsibilities of the respiratory system is to help regulate the body's pH balance. Carbon dioxide is made into carbonic acid, which the respiratory system can regulate through carbon dioxide levels.

Integumentary System

Integumentary system is skin, which includes all the sweat glands, hair follicles and plenty of nerves. The integumentary system is unique because it is the only single-organ system. Skin is both an organ and the entire organ system.

Endocrine System

The endocrine system includes all the glands that secret hormones into the bloodstream.

Most people find the endocrine system and the nervous system as the two most complicated systems in the body.

The endocrine system mostly regulates metabolism and utilizes the products of digestion.

Gastrointestinal System

The gastrointestinal system is affectionately known as the gut, which includes all the organs that carry food from where it enters to where it exits. The esophagus, stomach and intestines are all part of the gastrointestinal system. There is a lot of interaction between the gastrointestinal system (often called the GI tract) and the endocrine system.

The gastrointestinal system also plays host to a very important nerve called the vagus nerve. This is the main contributor to the parasympathetic nervous system and has a lot to do with slowing down metabolism, lowering heart rate and blood pressure, and stimulating the mechanics of digestion.

Musculoskeletal System

This is the skeleton and all the muscles, tendons and ligaments that are attached to it. The musculoskeletal system provides the framework and the engine for our movement, posture and productivity.

There are three types of muscles in the body: striated (skeletal or voluntary), smooth (visceral or involuntary) and cardiac (heart muscle). Only striated muscle is in the musculoskeletal system.

Nervous system

The nervous system includes the brain and spinal cord, plus all the nerves that are connected to both of these organs. The nervous system is incredibly detailed and includes the only tissue that isn't fed directly through contact with blood.

Reproductive System

The reproductive system the only system that is split into two parts. Half of us have a penis and testicles while the other half has a vagina, uterus and ovaries. This is the only organ system that is not complete in any one body and the only organ system that requires another person to complete its mission.

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