Anatomy of the Hand

The hand is a body part with a highly intricate structure. That is hardly surprising when you think about everything you can do with it. Writing, typing, gripping, and other daily activities require close coordination among all the 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 together form the carpus. This consists of eight bones. They lie in two rows of four bones next to each other. In the lower row, one bone lies on top of the others. They are connected to each other by capsules and ligaments.
The lower row consists of:

• Os scaphoïdeum
• Os lunatum
• Os triquetrum
• Os pisiforme

The upper row consists of:

• Os trapezium
• Os trapezoïdeum
• Os capitatum
• Os hamatum

There is little movement between the individual carpal bones. Together, however, they provide full mobility of the hand and wrist. Because, with the exception of the os pisiforme, no muscles attach to these bones, they mainly move when the rest of the hand or the wrist moves.

The metacarpal bones border the upper row of carpal bones. There are five in total, one (één) for each finger. They are indicated with a Roman numeral, with the thumb being I and the little finger V.

The fingers lie in line with the metacarpal bones. The thumb has two phalanges; the other fingers have three.

Capsule and ligaments

All the bones of the hand are connected by capsules and ligaments. These are connective tissue structures that keep the bones neatly in place. In addition, they provide strength and stability.

These structures crisscross each other and have receptors that warn of excessive stretch and impending damage. The muscles of the hand and wrist can then contract to prevent damage to capsules and ligaments.

There are two types of ligaments, intrinsic and extrinsic ligaments. Intrinsic ligaments are short and stiff and are mainly found between the carpal bones. Extrinsic ligaments are more flexible and much longer. They connect the bones of the forearm with the carpal and metacarpal bones.

Muscles

With muscles, we also speak of intrinsic and extrinsic muscles. Intrinsic muscles are shorter muscles that begin and end in the hand. These are, for example, the muscles that allow us to spread and close the fingers.

Extrinsic muscles are much longer. They begin in the forearm and then run with long tendons over the hand, mainly to the fingers. These include the muscles that extend and flex the wrist and fingers.

Nerves

Nerves control the muscles and provide sensation in the hand. There are three important nerves in the hand: the median, ulnar, and radial nerves. Each nerve supplies a different part of the hand. When one nerve has problems, this can cause tingling, numbness, or loss of muscle function in part of the hand.

An important part of the hand is the carpal tunnel. This is a kind of groove formed by the carpal bones. A strong ligament lies over it. Nine tendons èn the median nerve run through the tunnel. When this nerve is compressed and causes symptoms, this is called carpal tunnel syndrome.

Do you have symptoms? Make an appointment with a physical therapist.