Limb (anatomy)

A limb is a jointed part of the body. It has muscles and is used to move. Many animals use limbs to carry weight. They also use them to walk or run on land. Limbs help animals touch or grab objects. The very end of a limb is called the extremity.

Limbs work in a very organized way. They attach to the main body at a point called a girdle. The front limbs use a pectoral girdle. The back limbs use a pelvic girdle. These girdles connect to the limbs using ball-and-socket joints. This type of joint allows for movement. The bones grow from the body outward toward the tip.

Most four-legged animals share a similar bone pattern. This pattern comes from ancestors that lived a long time ago. These ancestors were fish-like creatures called sarcopterygians. They lived during a time called the Late Devonian. These animals survived a major event called the Late Devonian extinction. This shared history explains why many different animals have similar limbs.

Each limb has three main bone sections. The first part is the stylopodium. It has one long bone like the humerus or femur. The next part is the zeugopodium. It has two bones like the radius and ulna. The last part is the autopodium, which is the hand or foot. This part includes small bones called the mesopodium.

Humans use their limbs in special ways. Our upper limbs are our arms. Our lower limbs are our legs. We walk on two legs, which is called bipedalism. Our hands have five digits called fingers. These fingers help us do fine motor skills. This means we can move small things with great care. We can even make tools with our hands.