A metacarpal is any of the tubular bones located in the hand between the wrist bones (carpals) and the bones of the fingers (phalanges) in land vertebrates. They are analogous to the metatarsal bones in the foot.
Metacarpal Bones Explained
Metacarpals are essential for hand structure and function, allowing for grasping, manipulation, and weight-bearing in some animals. Each hand typically has five metacarpal bones, one for each digit (finger).
- Location: Situated in the palm of the hand, connecting the wrist and fingers.
- Number: Typically five metacarpals per hand in humans and many other mammals.
- Structure: Each metacarpal consists of a base (articulates with the carpal bones), a shaft (the long, central part), and a head (articulates with the proximal phalanx of a finger).
Evolution and Variation
The number and structure of metacarpals can vary significantly among different species due to evolutionary adaptations.
- Reduction: In some mammals, such as horses, the number of metacarpals has been reduced during evolution to improve running speed and efficiency. For example, horses primarily use a single, highly developed metacarpal (the third metacarpal or cannon bone) for weight-bearing. The other metacarpals are reduced to splint bones.
- Specialization: Different metacarpals may be specialized for different functions. For example, in primates, the first metacarpal (thumb) is often opposable, allowing for precise grasping.
Clinical Significance
Metacarpal fractures are common injuries, often resulting from falls, direct blows, or crushing injuries. Treatment typically involves immobilization with a cast or splint, and in some cases, surgical intervention may be required.
Summary
In short, metacarpals are the long bones in the hand that connect the wrist to the fingers, playing a crucial role in hand function and varying across species due to evolutionary adaptations.
