It permits movement of the body, maintains posture and circulates blood throughout the body. Main organs - muscles.

It functions as a barrier to protect the body from the outside world. It also functions to retain body fluids, protect against disease, eliminate waste products, and regulate body temperature. Main organs - skin, hair, nails, and sweat glands.

The basic unit of structure and function in a living thing.

A group of similar cells that perform the same function.

A structure in the body that is composed of different kinds of tissue.

A group of organs that work together to perform a specific function.

It transports oxygen, waste, nutrients, hormones, heat, etc... around the body. Main organs - heart, blood, blood vessels, and lymphatics.

It breaks down food into absorbable units that enter the blood for distribution to body cells. Main organs - esophagus, stomach, small intestine, and colon.

It regulates the body's growth, metabolism, and sexual development and function. Main organs - pituitary, thyroid, ovaries, and testes.

It protects and supports body organs and provides a framework the muscles use to support movement. Main organs - bones and joints.

It allows us to breathe and exchange carbon dioxide for oxygen. Main organs - nose, larynx, trachea, diaphragm, bronchi, and lungs.

It is responsible for producing offspring. Main organs - uterus, penis, ovaries, and testes.

It gets rid of wastes, useless byproducts excreted from cells, eradicates harmful chemical buildups and maintains a steady, balanced chemical concentration in the body. Main organs - kidneys, ureters, bladder, and urethra.

It filters fluid in the body; mounts the attack against foreign substances in the body. Main organs - lymph nodes, spleen, thymus, white blood cells.