Human Body

Tissues, Organs, and Glands

What is an organ system?

An organ system is a group of organs working together to perform a vital body function. There are 12 major organ systems in the human body.

Organ Systems and Their Functions
Organ System Components Functions
Cardiovascular and circulatory Heart, blood, and blood vessels Transports blood throughout the body, supplying nutrients and carrying oxygen to the lungs and wastes to kidneys
Digestive Mouth, esophagus, stomach, intestines, liver, and pancreas Ingests food and breaks it down into smaller chemical units
Endocrine Pituitary, adrenal, thyroid, and other ductless glands Coordinates and regulates the activities of the body
Excretory Kidneys, bladder, and urethra Removes wastes from the bloodstream
Immune Lymphocytes, macrophages, and antibodies Removes foreign substances
Integumentary Skin, hair, nails, and sweat glands Protects the body
Lymphatic Lymph nodes, lymphatic capillaries, lymphatic vessels, spleen, and thymus Captures fluid and returns it to the cardiovascular system
Muscular Skeletal muscle, cardiac muscle, and smooth muscle Allows body movements
Nervous Nerves, sense organs, brain, and spinal cord Receives external stimuli, processes information, and directs activities
Reproductive Testes, ovaries, and related organs Carries out reproduction
Respiratory Lungs, trachea, and other air passageways Exchanges gases—captures oxygen (O2) and disposes of carbon dioxide (CO2)
Skeletal Bones, cartilage, and ligaments Protects the body and provides support for locomotion and movement


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