Physiology is the way that systems in the human body, work and/or function.

There are roughly 12 to 14 systems in the human body:

*The Integumentary System is the skin that covers the human body and all of the functional components therein.

*The Circulatory System consists of the heart and blood circulation.

*The Skeletal System consists of the bones.

*The Muscular System consists of all the muscles in the human body.

*The Endocrine System consists of chemical messaging and hormones.

*The Nervous System consists of the brain to spinal cord functions and fluids therein.

*The Reproductive System consists of the gametes (sex organs) and all of the functions therein.

*The Immune System consists of the body’s response to intrusion, or regulation (and sometimes initiation) of dis-ease.

*The Lymphatic System consists of fluid monitoring and all of the functions therein.

* The Renal System consists of the kidneys, ureters, bladder, and urethra, working together to filter out waste and excess fluids from the blood.

*The Respiratory System consists of the inhalation of chemical gases (oxygen), and exhalation of chemical gases (carbon dioxide).

*The Exocrine System consists of the skin, nail, and hair along with all of the functions therein (may be regarded as part of the integument given nails are components of skin).

*The Cardiovascular System consists of the heart, arteries, and veins that complement the circulatory system.