Organ Systems
An organ system is a group of organs that cooperate on a shared function. By long convention the human body is divided into eleven systems. They are catalogued here, each with its own overview.
The division is a convenience, not a hard boundary — the systems overlap constantly. The pancreas belongs to both the digestive and endocrine systems; bone is part of the skeletal system but also makes blood cells. Understanding the organism means seeing how these systems interlock.
The eleven systems
Section titled “The eleven systems”- Integumentary — skin, hair, nails; the body’s outer barrier.
- Skeletal — bones, cartilage, joints; structure and protection.
- Muscular — muscles; movement and posture.
- Nervous — brain, spinal cord, nerves; fast control and sensing.
- Endocrine — hormone-producing glands; slow, chemical control.
- Cardiovascular — heart and blood vessels; transport.
- Lymphatic / immune — lymph vessels, nodes, immune cells; defense.
- Respiratory — lungs and airways; gas exchange.
- Digestive — gut and accessory organs; breaking down food.
- Urinary — kidneys and bladder; filtering and water balance.
- Reproductive — gonads and associated organs; producing offspring.
Two ways to group them
Section titled “Two ways to group them”It can help to remember the systems by what they do: boundary and support (integumentary, skeletal, muscular), control and communication (nervous, endocrine), transport and defense (cardiovascular, lymphatic/immune, respiratory), and maintenance and continuity (digestive, urinary, reproductive).