Library
- Bones & skeleton
The human skeleton is the internal framework of 206 named bones that support the body, protect the organs, anchor the muscles, and store minerals.
- Brain & nerves
The nervous system is the brain, spinal cord, and peripheral nerves that carry signals between the body and the central nervous system.
- Digestive system
The digestive system is the tube and glands that take in food, break it down, absorb the nutrients, and expel the waste — from the mouth to the anus.
- Heart & blood vessels
The cardiovascular system is the heart together with the arteries, veins, and capillaries that circulate blood through every tissue of the body.
- Joints & ligaments
A joint is a place where two or more bones meet, and ligaments are the tough fibrous bands that hold the bones together at the joint.
- Lungs & breathing
The respiratory system is the airways and lungs that draw air in, transfer oxygen to the blood, and release carbon dioxide.
- Muscles
The muscular system is the roughly 600 named skeletal muscles that pull on bones to produce movement, plus the smooth muscle of the organs and the cardiac muscle of the heart.
- Organs
An organ is a structure made of two or more tissues that work together to perform a specific job — such as the kidneys filtering blood or the thyroid gland producing hormones.