It is the largest and strongest rotator cuff muscle, and, in addition to its importance during throwing and racquet sports, it is an important stabilizer of the shoulder joint. It forms the back wall of our armpit axilla on the way to its attachment to the humerus. Despite its strength and importance, the latissimus is frequently used as a muscle transfer, or as a flap to cover a large wound or for breast reconstruction.
Fortunately, most patients are able to compensate for its loss within 9 to 12 months. The pectoralis major is a large chest muscle with two heads. The clavicular head arises from the collar bone clavicle , while the sternocostal head arises from the breastbone sternum and rib cage.
The two heads join to form a flat tendon which attaches to the upper humeral shaft, just in front of the latissimus tendon. It provides power for many arm actions, including flexion as when throwing a ball side-armed , internal rotation arm-wrestling , and adduction pulling the arm in towards the body. Injuring the pectoralis major usually requires a substantial force, typically occurring in weight-lifters during a bench press when fatiguing and losing control of the weights.
The third major muscle in the front of the arm is the coracobrachialis. Named for its origin and insertion, it arises from the coracoid process of the shoulder blade and inserts into the humerus. Its main role is to flex the shoulder, bringing the arm forward, as happens during normal walking.
It also pulls the arm in towards the body adduction , working in conjunction with the deltoid to stabilize the arm while reaching. Arising from the mid-forearm from the radial shaft, the flexor pollicis longus allows us to bend the tip of our thumb. It is the ninth tendon to pass through the carpal tunnel on its way to the thumb.
Located deep in the forearm, the flexor digitorum profundus arises from the ulna and interosseous membrane. From the muscle, four tendons emerge which pass through the carpal tunnel and insert into the tips of the index, middle, ring, and small fingers.
Its primary action is to bend these fingers, and due to its insertion past the last joint of the finger, it is able to bend all three finger joints. Unlike the FDS, there is a common muscle belly for the middle, ring, and small fingers, typically preventing us from bending the tip of one of these fingers without the others bending as well. There is a separate muscle belly for the index finger FDP, though, contributing to its independence.
The flexor digitorum superficialis arises from the medial epicondyle an elbow bone between the palmaris longus and the flexor carpi ulnaris muscles. In the forearm, the FDS has four independent muscle bellies from which four tendons arise. After crossing the wrist, they pass through the carpal tunnel, then spread out to the index, middle, ring, and small fingers.
The primary function of the FDS is to bend the middle joint of each finger except the thumb. The final muscle to arise from the medial epicondyle an elbow muscle is the flexor carpi ulnaris. It also has two heads, with the larger head arising from the ulna beginning just below the elbow and continuing over two-thirds the length of the forearm.
It then becomes a tendon, crosses the wrist, and attaches at the pisiform bone at the base of the palm. This large muscle is built for power, bending and deviating the wrist away from the thumb. Arising from the outside of the elbow is the brachioradialis BR.
The BR inserts into the end of the radius bone, just below the wrist joint the distal radius , in line with the thumb. The forearm is in neutral position when the thumb is up, small finger towards the ground.
In this position, the BR is a pure flexor of the elbow. If the palm is facing towards the ground, the BR can twist the forearm until the thumb is in the up position again neutral. When the palm is facing up, the BR twists the forearm back to the neutral position. The flexor carpi radialis arises adjacent to the pronator teres an elbow muscle , crosses the elbow and wrist, and attaches to the base of the second hand bone.
Its primary role is to bend the wrist, and it can help to move the wrist towards the thumb. At the wrist, the FCR tendon passes through a tunnel and is prone to tendonitis or even rupturing. Fortunately, we can live without the function of the FCR; therefore it is a commonly used tendon for reconstruction or as a tendon transfer.
Next to the FCR arises the palmaris longus muscle. This muscle, with a long tendon, travels down the forearm to the center of the wrist and palm, where it attaches to the palmar aponeurosis a fibrous tissue layer between the thenar and hypothenar muscles. It functions as a flexor of the wrist, and like the FCR is expendable. When present, it is frequently used as a source for tendon graft, where it is removed and used to rebuild a ligament or more important tendon.
It is also a commonly used tendon transfer. The main action of this muscle is to straighten the thumb at its middle joint. The extensor pollicis longus attaches at the thumb and acts primarily to straighten the tip of the thumb. Tendonitis of the EPL is unusual, however it is prone to rupture in its compartment.
Most typically, this originates from non-displaced wrist fractures breaks or inflammatory arthritis. The extensor carpi radialis brevis arises just above the elbow. It crosses both the elbow and wrist joints before inserting onto the third hand bone. Its main function is to straighten the wrist and stabilize the wrist during power grasp. This is known as intersection syndrome. The ECRB is also often partially responsible for pain on the outside of the elbow, also known as tennis elbow or lateral epicondylitis.
When the origin of the ECRB is damaged from overuse, aging, or injury, the pain of tennis elbow occurs. Fortunately, this condition is usually self-limiting.
The extensor carpi radialis longus arises just above the ECRB muscle on the outside of the elbow and attaches to the 2nd hand bone. It is important to understand the normal anatomy of the hand to learn more about diseases and conditions that can affect our hands.
The wrist is comprised of 8 carpal bones. These wrist bones are attached to the radius and ulna of the forearm to form the wrist joint. They connect to 5 metacarpal bones that form the palm of the hand. Each metacarpal bone connects to one finger at a joint called the metacarpophalangeal joint or MCP joint.
This joint is also 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 interphalangeal joints, except for the thumb, which only has 2 phalanges and one interphalangeal joint. The first joint close to the knuckle joint is called the proximal interphalangeal joint or PIP joint. The joint closest to the end of the finger is called the distal interphalangeal joint or DIP joint.
Our hand bones are held in place and supported by various soft tissues. These include: articular cartilage, ligaments, muscles and tendons. Articular cartilage is a smooth material that acts as a shock absorber and cushions the ends of bones at each of the 27 joints, allowing smooth movement of the hand.
Ligaments are tough rope-like tissue that connect bones to other bones, holding them in place and providing stability to the joints. Each finger joint has two collateral ligaments on either side, which prevents the abnormal sideways bending of the joints. The volar plate is the strongest ligament in the hand. It joins the proximal and middle phalanx on the palm side of the joint and prevents backwards bending of the PIP joint hyperextension.
Intrinsic muscles are small muscles that originate in the wrist and hand. The sheaths are tubular structures that surround part of the fingers. The tendons connect muscles in the arm or hand to the bone to allow movement. In addition, there are arteries, veins and nerves within the hand that provide blood flow and sensation to the hand and fingers.
Health Home Treatments, Tests and Therapies. There are 3 major types of bones in the hand itself, including: Phalanges. Metacarpal bones.
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