Metacarpal bones

Metacarpal Bones

human hand with the metacarpal bones

The metacarpal bones are a group of five long bones in the hand located between the phalanges (bones of the fingers) and the carpal bones of the wrist, which together form the skeleton of the palm. They are part of the appendicular skeleton and contribute to the complex structure that allows for a wide range of motion and dexterity in the human hand.

Structure and Function

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An anatomical illustration of the human hand with the metacarpal bones highlighted.

Anatomy of the Metacarpals

Each metacarpal bone is cylindrical in shape and has three parts: the base, shaft, and head. The base is the portion that articulates with the carpal bones, the shaft is the elongated part, and the head is the rounded portion that connects to the phalanges.

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Diagram showing the parts of a metacarpal bone.

The first metacarpal bone, associated with the thumb, is shorter and more mobile than the others, allowing for the thumb's unique opposable function. This opposability is a key factor in the ability of humans to perform precision grip tasks.

Function

The metacarpals support the palm and allow for the movement of the fingers. They play a vital role in hand functions such as gripping, holding, and manipulating objects of various sizes and shapes. The arrangement of the metacarpal bones also contributes to the arches of the hand, which help in the distribution of forces during hand activities.

Development and Ossification

Metacarpal bones develop from cartilage through a process called endochondral ossification. This process typically begins in the womb and continues through childhood and adolescence until the bones fully ossify.

An X-ray showing the ossification of metacarpal bones in a developing child.

Clinical Significance

Fractures and Injuries

Metacarpal bones are susceptible to fractures, commonly resulting from direct trauma or compressive forces. Boxer's fracture is a well-known injury specifically affecting the neck of the second and third metacarpal bones.

Disorders

Certain conditions, such as rheumatoid arthritis, can affect the metacarpal bones, leading to pain and reduced hand function. Moreover, congenital anomalies such as brachydactyly or syndactyly may involve the metacarpal bones.

Comparative Anatomy

In other mammals, the structure of the metacarpal bones varies according to the species' mode of locomotion. In hoofed animals, these bones are elongated and adapted to bear weight, while in winged creatures like bats, they are elongated and connected to support the wing membrane.

See Also

• Carpus
• Phalanx bones
• Skeletal system
• Hand anatomy

External Links

• HandCare.org - Information on hand anatomy and care from the American Society for Surgery of the Hand.
• National Library of Medicine - Bookshelf - Detailed information on the anatomy of the metacarpal bones.