Organ Systems

Major Role:
The main role of the skeletal system is to provide support for the body, to protect delicate internal organs and to provide attachment sites for the organs.

Major Organs:
Bones, cartilage, tendons and ligaments.

Major Role:
The main role of the muscular system is to provide movement.  Muscles work in pairs to move limbs and provide the organism with mobility.  Muscles also control the movement of materials through some organs, such as the stomach and intestine, and the heart and circulatory system. 

Major Organs:
Skeletal muscles and smooth muscles throughout the body.

Major Role:
The main role of the circulatory system is to transport nutrients, gases (such as oxygen and CO₂), hormones and wastes through the body. 

Major Organs:
Heart, blood vessels and blood.

Major Role:
The main role of the nervous system is to relay electrical signals through the body.  The nervous system directs behaviour and movement and, along with the endocrine system, controls physiological processes such as digestion, circulation, etc. 

Major Organs:
Brain, spinal cord and peripheral nerves.

Major Role:
The main role of the respiratory system is to provide gas exchange between the blood and the environment.  Primarily, oxygen is absorbed from the atmosphere into the body and carbon dioxide is expelled from the body.

Major Organs:
Nose, trachea and lungs.

Major Role:
The main role of the digestive system is to breakdown and absorb nutrients that are necessary for growth and maintenance.

Major Organs:
Mouth, esophagus, stomach, small and large intestines.

Major Role:
The main role of the excretory system is to filter out cellular wastes, toxins and excess water or nutrients from the circulatory system. 

Major Organs:
Kidneys, ureters, bladder and urethra.

Major Role:
The main role of the endocrine system is to relay chemical messages through the body.  In conjunction with the nervous system, these chemical messages help control physiological processes such as nutrient absorption, growth, etc.

Major Organs:
Many glands exist in the body that secrete endocrine hormones.  Among these are the hypothalamus, pituitary, thyroid, pancreas and adrenal glands.