Physiology is the study of how the human body works under normal conditions. You use physiology when you exercise, read, breathe, eat, sleep, move or do just about anything.

Physiology is generally divided into ten physiological organ systems: the cardiovascular system, the digestive system, the endocrine system, the immune system, the muscular system, the nervous system, the renal system, the reproductive system, the respiratory system, and the skeletal system. Let’s look at each system in a bit more detail.



Cardiovascular system

The cardiovascular system is made up of your heart and lots of blood vessels. The job of the cardiovascular system is to pump blood around your body, bringing oxygen and other nutrients to the cells, and removing waste products.

Digestive system

The digestive system is made up of many organs, including the stomach and intestines that break down food that you eat into nutrients your body can use.

Endocrine system

The endocrine system is made up of many glands throughout the body that secrete chemicals called hormones. The job of the endocrine system is to regulate the internal environment of the body, including growth and metabolism.

Immune system

The immune system is made up of a series of defense mechanisms that protect your body from outside invaders and defend against disease.

Muscular system

Your muscles make up your muscular system, which allows you to move, aids in posture, and sustains life.

Nervous system

The nervous system is made up of your brain, spinal cord, and a system of nerves that extend throughout your body. The nervous system acts as the control center for all of the other physiological systems and allows for communication between the systems.

Renal system

The renal system is primarily made up of the kidneys, with several accessory organs. The job of the renal system is to regulate the composition of fluids in the body, and excrete the remaining unneeded components.

Reproductive system

The reproductive system is made of gonads, or sex organs, and many other accessories and supporting organs. The ultimate goal of the reproductive system is the production of offspring from the egg and sperm and the survival of the species. The male and female reproductive systems are very different, but both are necessary for successful reproduction.

Respiratory system

The respiratory system is made up of your lungs and a system of airways that connect your lungs to the outside. The job of the respiratory system is to allow oxygen into the body and to remove carbon dioxide from the body.

Skeletal system

Your skeletal system is made up of your bones, joints, cartilage, and connective tissues.

As you can see from these brief explanations, each physiological system works to perform different functions in the body. It is important to remember, though, that each system works with every other system to keep you alive.

When you become sick or injured, your normal physiology is disrupted. We call this altered state “pathophysiology”, which is a term derived from the Greek word pathos, meaning disease.