The hand in the human body is made up of the wrist, palm, and fingers. The most flexible part of the human skeleton, the hand enables us to perform many of our daily activities.
The hand’s complex anatomy consists of 27 bones, 27 joints, 34 muscles, over 100 ligaments and tendons, numerous blood vessels, nerves, and soft tissue.
It is important to understand the normal anatomy of the hand in order to learn about diseases and conditions that can affect our hands.
HAND AND WRIST
The wrist is comprised of 8 bones called carpal bones. These wrist bones connect to 5 metacarpal bones that form the palm of the hand. Each metacarpal bone connects to one finger or a thumb at a joint called the metacarpophalangeal joint, or MCP joint. This joint is commonly referred to as the knuckle joint.
The bones in our fingers and thumb are called phalanges. Each finger has 3 phalanges separated by two joints. The first joint, closest to the knuckle joint, is the proximal interphalangeal joint or PIP joint. The second joint nearer the end of the finger is called the distal interphalangeal joint, or DIP joint. The thumb in the human body only has 2 phalanges and one interphalangeal joint.
Soft Tissue Anatomy
Our hand and wrist bones are held in place and supported by various soft tissues. These include:
Cartilage Shiny and smooth, cartilage allows smooth movement where two bones come in contact with each other.
Tendons Tendons are soft tissue that connects muscles to bones to provide support. Extensor tendons enable each finger to straighten.
Ligaments are strong rope like tissue that connects bones to other bones and help hold tendons in place providing stability to the joints. The volar plate is the strongest ligament in the hand and prevents hyperextension of the PIP joint.
Muscles Muscles are the fibrous tissues capable of contracting to cause body movement.
Nerves are responsible for carrying signals back and forth from the brain to muscles in ourbody, enabling movement and sensation such as touch, pain, and hot or cold. The three main nerves responsible for hand and wrist movement all originate at the shoulder area and include the following:
Radial: The radial nerve runs down the thumb side of the forearm and provides sensation to the back of the hand from the thumb to the third finger.
Median: The median nerve travels through the wrist tunnel, also called carpal tunnel, providing sensation to the thumb, index finger, long finger, and part of the ring finger.
Ulnar: The ulnar nerve travels through a tunnel in the wrist called Guyon’s tunnel formed by two carpal bones and the ligament that connects them together. The ulnar nerve supplies feeling to the little finger and half of the ring finger.
The two main vessels of the hand and wrist are:
Radial Artery: The radial artery is the largest artery supplying the hand and wrist area. Traveling across the front of the wrist, nearest the thumb, it is this artery that is palpated when a pulse is counted at the wrist.
Ulnar Artery: The ulnar artery travels next to the ulnar nerve through Guyon’s canal in the wrist. It supplies blood flow to the front of the hand, fingers and thumb.
Bursae: Bursae are small fluid filled sacs that decrease friction between tendons and bone or skin. Bursae contain special cells called synovial cells that secrete a lubricating fluid. When this fluid becomes infected, a common painful condition known as bursitis can develop.
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