Limb (anatomy)

A limb is a major appendage of the body used for locomotion, manipulation, and support. In vertebrates, limbs typically include an arm or leg and are characterized by a skeletal framework consisting of bones, joints, muscles, tendons, ligaments, nerves, and blood vessels. The structure and function of limbs can vary significantly across different species and within the same species, depending on factors such as environment, lifestyle, and evolutionary adaptation.

Limbs are generally paired, with one on each side of the body. They are attached to the torso at the shoulder or hip girdle. The basic skeletal structure of vertebrate limbs is derived from a common ancestor and consists of a proximal segment (e.g., humerus in the upper limb, femur in the lower limb), an intermediate segment (e.g., radius and ulna in the upper limb, tibia and fibula in the lower limb), and a distal segment (e.g., carpal/metacarpal/phalanges in the upper limb, tarsal/metatarsal/phalanges in the lower limb).

The musculature of limbs is complex, allowing for a wide range of movements. Muscles are attached to bones via tendons and work in antagonistic pairs to produce flexion, extension, abduction, adduction, rotation, and other movements. Nerves transmit signals from the brain and spinal cord to the muscles, controlling movement and providing sensory feedback. Blood vessels supply the limb with oxygen and nutrients, while removing waste products.

Limbs are essential for a variety of functions, including walking, running, swimming, climbing, grasping, and manipulating objects. Their structure and function are highly adapted to the specific needs of each species. Injuries to limbs, such as fractures, sprains, and strains, can significantly impair mobility and function. Prosthetic limbs are often used to replace missing or non-functional limbs.