Anatomy of the hand

The hand is an intricately structured body part, which is understandable given its wide range of functions. Activities such as writing, typing, gripping, and other daily tasks require seamless coordination among muscles, tendons, bones, and nerves.

The hand is an intricately structured body part, which is understandable given its wide range of functions. Activities such as writing, typing, gripping, and other daily tasks require seamless coordination among muscles, tendons, bones, and nerves.

Bones

The bones of the hand are divided into three zones:

1. Carpal bones.
2. Metacarpal bones.
3. Fingers.

The carpal bones collectively form the carpus, which consists of eight bones arranged in two rows of four. The lower row includes:

• Os scaphoideum
• Os lunatum
• Os triquetrum
• Os pisiforme

The upper row includes:

• Os trapezium
• Os trapezoideum
• Os capitatum
• Os hamatum

There is limited movement between individual carpal bones, but together they enable full mobility of the hand and wrist. Since no muscles (except for the os pisiforme) attach directly to these bones, they primarily move when the rest of the hand or wrist moves.

The metacarpal bones connect to the upper row of carpal bones. There are five metacarpal bones, one for each finger, labeled with Roman numerals (I for the thumb, V for the little finger).

The fingers align with the metacarpal bones. The thumb has two phalanges, while the other fingers have three.

Capsule and ligaments

All hand bones are connected by capsules and ligaments, which are connective tissue structures that keep bones in place, providing strength and stability.

These structures crisscross and contain sensors that detect excessive stretch and potential damage. The hand and wrist muscles then contract to prevent injury to the capsules and ligaments.

There are two types of ligaments: intrinsic (short and stiff, mainly between carpal bones) and extrinsic (longer and more flexible, connecting forearm bones to carpal and metacarpal bones).

Muscles

Muscles are also categorized as intrinsic (shorter muscles that start and end in the hand, such as those that spread and close the fingers) and extrinsic (longer muscles that originate in the forearm and extend via tendons to the fingers, enabling wrist and finger extension and flexion).

Nerves

Nerves control muscles and provide sensation in the hand. Three key nerves, the median, ulnar, and radial, each govern different parts of the hand. Damage to a nerve can cause tingling, numbness, or muscle dysfunction in specific areas.

A critical area is the carpal tunnel, a groove formed by carpal bones and covered by a strong ligament. Nine tendons and the median nerve pass through this tunnel. Compression of the median nerve here causes carpal tunnel syndrome.

If you experience hand-related issues, consider making an appointment with a physiotherapist.