The 2 rows of carpal bones are connected to 2 bones of the arm--the ulna bone and the radius bone. Numerous muscles, ligaments, tendons, and sheaths can be found within the hand. The muscles are the structures that can contract, allowing movement of the bones in the hand. The ligaments are fibrous tissues that help bind together the joints in the hand. The difference between hand and arm is the composition of bones and their works. The hand is part of the arm but it is considered different from the forearm and upper arm.
According to human anatomy, the hand is the part below the wrist which has a palm, four fingers, and one thumb. There are different functions of hands It is the most distinctive feature of human being. There are around 27 bones in one human hand which consists of Phalanges, metacarpals, And carpals of wrist. It is the metacarpals that connectsFinger phalange to capals. Hand does most of the activities of the human body, it is also the most flexible body part of humans which enables them to do several activities like holding things, doing work, enabling deaf or for blind people to use them for their Sign Languages.
Hand is attached to the arm which provides hand, strength and support to do certain activities. Life of a human becomes extremely difficult without a hand. Both hands right and left are equally important for people. Although there are several people who have a habit of doing work from one hand. For example some people are lefty which make things difficult for them to do with their right hand. Some of the attached muscles run all the way into the hand. The humerus typically becomes a problem only when it breaks fractures.
There are many types of humerus fractures and as a result, the treatments for these fractures are quite variable. The radius is one of the two forearm bones and is on the thumb side of the forearm near the hand, but is always on the outside of the elbow. The position of the radius changes depending on how the hand is turned because the radius twists around the other forearm bone, the ulna. At the elbow, the radius is part of the odd shaped joint between the humerus and the two forearm bones.
The joint between the radius and humerus by itself is like a ball and socket joint, with the radius forming the socket.
The radius has many muscular attachments to move the elbow, forearm, wrist and fingers. The end of the radius leads to the wrist joint. The radius and ulna are joined by cartilage joints at the elbow and at the wrist. They are also joined by multiple ligaments. There are many ways that people injure the radius and the forearm. Breaking this bone is common because when we fall, the hands and arms are typically used to break the fall.
The ulna is one of the two forearm bones and is on the small finger side of the forearm. Unlike the radius, this bone does not twist, so when the hand changes position, the ulna is always in the same position on the inside part of the forearm. Like the radius, the ulna has joints at the elbow and wrist.
The joint between the ulna and humerus is a hinge type of joint. At the wrist, the ulna has a smaller surface in contact with the wrist bones and typically bears less of the force from the hand and wrist. The ulna is joined to the radius throughout the forearm with cartilage joints at the elbow and wrist and multiple ligaments connecting to the radius through the whole length of the forearm.
Like the radius, breaking the ulna bone is a common reason for problems with the ulna. The scaphoid is a bone in the wrist. It is part of the first row of wrist bones, but it helps to link the two rows of wrist bones together. Most of the scaphoid is covered with cartilage which contacts five other bones in the wrist and forearm. The part of the scaphoid without cartilage is attached to ligaments and has blood vessels that come from the radial artery.
Bones need blood flow to heal. A broken or fractured scaphoid can have difficulty healing, or may never heal, because of a disruption of blood flow through the scaphoid. An intact scaphoid is important and necessary for proper wrist function because of how it interacts with the other wrist bones. The lunate is a bone in the middle of the wrist in the first row of wrist bones.
Like most of the wrist bones, it is almost entirely covered in cartilage. This bone has a crescent shape when seen from the side and its large cartilage surface allows for significant wrist motion. It is uncommon to break the lunate, but the lunate can be involved with dislocations of the wrist and can rub against the ulna if the ulna is too long compared to the radius bone.
The triquetrum is a bone on the small finger side of the wrist in the first row of wrist bones. This bone adds stability to the wrist, gives the wrist a larger surface to bear weight transmitted from the hand, and makes a joint with other carpal bones including the pisiform.
This is a roughly trapezoidal-shaped bone in the second row of wrist bones and primarily holds the index finger metacarpal bone in place.
This bone is uncommonly injured. The trapezium is a saddle-shaped bone in the second row of wrist bones, and it is the main place where the thumb metacarpal connects to the wrist. This bone has an odd shape that allows the thumb to move in multiple directions, yet it stabilizes thumb as well. There are two main problems seen with this wrist bone. Breaking fracturing the bone is common, but the most common problem is arthritis between the trapezium and the bones it sits next to in the wrist and thumb.
The capitate is a large bone in the center of the second row of wrist bones. It arises from the front surface of the shoulder blade, and attaches to the lessor tuberosity of the humerus. Its main action is to rotate the arm towards the body internal rotation , as when putting your hand on your stomach. 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.
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