The human hand comprises the wrist, palm, and fingers and consists of 27 bones, 27 joints, 34 muscles, over 100 ligaments and tendons, and many blood vessels and nerves.
The hands enable us to perform many daily activities, such as driving, writing and cooking. It is important to understand the normal anatomy of the hand to learn more about diseases and conditions that can affect our hands.
There are 27 bones in the human hand: 8 in the wrist (the carpal bones), 5 in the palm (the metacarpal bones), and 14 in the fingers and thumb (the phalanges).
The carpal bones are arranged in two rows: The proximal row (closest to the forearm) includes the scaphoid, lunate, triquetrum, and pisiform, while the distal row (closest to the fingers) includes the trapezium, trapezoid, capitate, and hamate.
There are numerous joints in the hand and wrist, each providing a different type of movement. The main ones are:
The hand and wrist contain various types of soft tissues that work together to enable the complex movements and functions of the hand.
The skin protects the hand and also provides a sense of touch. The skin on the palm and fingers is thick and hairless, with unique ridges (fingerprints) that provide grip. Under the skin, a layer of subcutaneous tissue contains fat and connective tissue, serving as padding and insulation.
Ligaments are tough rope-like tissues that connect bones to other bones, holding them in place and providing joint stability. Each finger joint has two collateral ligaments, one on either side, which prevent the abnormal sideways bending of the joints. The volar plates are particularly strong structures on the palm side of each MCP and IPJ that prevent excessive backward bending of the joints (hyperextension).
The muscles of the hand and wrist are categorised into two groups: extrinsic and intrinsic. The extrinsic muscles originate in the forearm and insert into various points in the hand. They provide strength, stability and power for wrist and finger movement. The intrinsic muscles are smaller, originating and inserting within the hand, providing fine motor control and finger movement.
There are nine extrinsic muscles grouped into flexors and extensors:
There are 20 intrinsic muscles in the hand. These are typically organised into groups based on their location and function:
The tendons of the hand and wrist are strong, flexible bands of fibrous tissue that connect the muscles of the forearm to the bones of the hand and fingers. The primary groups of tendons in the hand are the flexor and extensor tendons.
These tendons originate from the muscles in the forearm and run along the wrist and hand's underside (palm side). They allow you to bend your wrist, fingers and thumb (flexion).
Finger flexor tendons run through a sheath or tunnel called the carpal tunnel as they cross the wrist.
These tendons originate from muscles in the forearm and run along the top (backside) of the wrist and hand. They allow you to straighten your wrist, fingers and thumb (extension).
Extensor tendons are held in place on the back of the hand by a band known as the extensor retinaculum. This ensures that the tendons stay close to the bone and work effectively.
These tendons allow the fine and complex movements of the wrist, hand, and fingers, enabling us to perform various tasks, from writing to grasping objects.
The hand's nerves carry electrical signals from the brain to the muscles in the forearm and hand, enabling movement. They also carry the senses of touch, pain and temperature from the hands to the brain.
The three main nerves of the hand and wrist are the ulnar nerve, radial nerve and median nerve. All three nerves originate at the shoulder and travel down the arm to the hand. Each of these nerves has sensory and motor components.
The hand and wrist are supplied by a rich network of blood vessels, which provide oxygenated blood to the tissues and remove deoxygenated blood. Here are the main blood vessels involved:
The main arteries that supply the hand and wrist are the radial and ulnar arteries, which are branches of the brachial artery (the major artery of the upper limb).
These two arteries are interconnected in the hand via the superficial and deep palmar arches, creating a redundant system to ensure that even if one pathway is blocked, blood can still reach all parts of the hand.
Veins return deoxygenated blood from the tissues back to the heart. A network of small veins (venules) drains the hand and fingers. These unite to form larger veins:
The radial and ulnar veins form the brachial veins in the forearm, near the elbow, which continues as the axillary vein in the upper arm, and then the subclavian vein, returning blood to the heart via the superior vena cava.
Bursae are small, fluid-filled sacs that provide a cushion between bones and soft tissues like muscles, tendons, and skin. They reduce friction and allow for smooth movement between structures. While bursae are found throughout the body, there are relatively few in the hand and wrist compared to other areas like the shoulder or knee.
Most bursae in the hand and wrist are associated with the tendons. The hand and wrist tendons do not have true synovial sheaths; instead, they have a specialised structure known as a tendon sheath, a type of bursa that wraps around the tendon, reducing friction as the tendon moves.
In the hand and wrist, bursae or tendon sheaths can be found in places like:
Inflammation of these bursae, a condition known as bursitis, can cause pain and limit movement. On the hand, this is more commonly seen in the tendon sheaths, resulting in conditions like trigger finger or De Quervain's tenosynovitis.
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