Anatomy and function of the arm muscles.

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The muscles of the arms are attached to the scapula, shoulder bones ( humerus ), forearm bones ( radius and ulna ), wrist, fingers, and thumb. These muscles control the movement of the elbow, forearm, wrist, and fingers. With an injury or neuromuscular disorder, daily tasks that require the use of hands and arms can be challenging.

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Anatomical structure and location.

Each arm is made up of 24 different muscles that control the movement of the elbow, forearm, wrist, and fingers. Compared to the five shoulder muscles, the lower arm contains 19 different muscles, which are divided into the front (front of the arm) and the back (back of the arm). They can be superficial (close to the skin) or deep (underlying the superficial group).

Flexors are groups of muscles that flex and move parts of the body, such as an arm, hand, or fingers, closer to the body, while extensors are groups of muscles that expand and move parts of the body away from the body.

Shoulder

The five shoulder muscles originate from the front of the scapula, called the scapula , or the top of the humerus, the longest bone that makes up the shoulder.

Shoulder muscles that have more than one head or muscle segments have a portion originating from each location. The biceps brachii at the front of the arm has two heads and the triceps at the back of the arm has three heads. Although each head originates from a different location, all heads of the same muscle group connect and adhere to the same location.

The biceps brachii attaches to the upper part of the radius, the forearm bone on the side of the thumb, while the muscles of the humerus, triceps and anconus attach to the upper part of the ulna, the forearm bone on the pinky side. …

The brachialis muscle is the only muscle in the shoulder that does not connect to the bones of the forearm and attaches to the humerus. All of these muscles are long muscles that run the length of the shoulder, with the exception of the anconeus, a small, short muscle only 9 to 10 centimeters (cm) long that crosses the back of the elbow.

Front of forearm (front of forearm)

The superficial muscles of the front of the arm are long and run along the forearm. The pronator ring, the flexor radialis of the wrist, the flexor carpi ulnaris, and the palmar longus muscle originate from a specific part of the lower end of the humerus called the medial epicondyle.

The pronator circular adheres to the lower end of the radius near the wrist, while the flexor radius of the wrist and the flexor ulna of the wrist adhere to the carpus and metacarpals of the wrist and hand. The palmar muscle attaches to the palmar fascia, the connective tissue of the palm. While the superficial flexor muscle begins as a single muscle, it divides into four separate tendons that attach to the phalanx bones of the index, middle, ring, and little fingers.

The deep muscles of the front of the hand are at the base of the superficial muscles. The deep flexor of the fingers originates in the upper part of the ulna and the long flexor of the thumb, in the middle of the radius. Both muscles meet with the connective tissue that connects the radius and ulna in the forearm.

While both muscles are long and run the length of the forearm, the flexor hallucis longus has a long tendon that attaches to the base of the thumb, while the deep flexor muscle begins as a single muscle but splits into four. separate tendons that are attached to the muscle. phalanx. bones of the index, middle, ring and little fingers.

The pronator quadratus is a small square muscle, approximately 6 cm long, that connects the lower end of the ulna horizontally with the lower end of the radius near the wrist.

Back of the forearm (back of the forearm)

Like the muscles of the front of the arm, the superficial muscles of the back of the arm are long and run the length of the forearm. The extensor radialis brevis of the wrist, the extensor ulnaris of the wrist, the extensor digiti minimi, and the extensor digiti minimi begin at a specific portion of the lower end of the humerus called the lateral epicondyle. The longitudinal and radial extensors of the wrist originate in an area immediately above the lateral epicondyle, called the crest of the epicondyle.

The extensor radialis longus of the wrist, the extensor radialis brevis, and the extensor ulnaris of the wrist are attached to the metacarpals of the wrist, while the radius muscle attaches to the end of the radius near the wrist at a prominence. bone called the radial styloid process. Although the extensor digitorum begins as a single muscle, it divides into four separate tendons that attach to the phalanx bones of the index, middle, ring, and little fingers. The minimal extensor of the fingers attaches only to the little finger.

The deep muscles of the back of the hand are at the base of the superficial muscles. The instep is attached to the lateral epicondyle of the humerus, like most of the superficial muscles of the posterior part of the forearm, while the abductor thumb, the long extensor thumb, the short extensor digitorum of the thumb, and the extensor indus muscle are formed at different points along the ulna, radius, etc. d. and the connective tissue that connects the radius and ulna in the forearm.

The instep is attached to the outer edge of the radius, while the extensor pointer, a small muscle near the end of the forearm, connects to the index finger. The long abductor thumb, long extensor thumb, and short extensor thumb are attached to the thumb.

Function

The shoulder muscles, the area between the shoulder and the elbow, primarily control the movement of the elbow. The biceps brachii, coracobrachialis, and brachii control elbow flexion or elbow flexion. The brachioradialis muscle of the forearm also contributes to elbow flexion. The triceps brachii, together with a small contribution from the anconeus, controls the movement opposite to the extension of the elbow. The biceps brachii and triceps brachii also contribute to shoulder flexion and extension, respectively.

The muscles in the lower arm, the area between the elbow and the wrist, control the movement of the wrist, forearm, and fingers. The flexor radialis of the wrist, the flexor ulnaris of the wrist, and the flexor palmaris longus or flexor of the wrist, while their counterparts (the extensor radialis longus of the wrist, the extensor radialis brevisis longus, and the extensor ulnaris longus of the wrist). the wrist) extend the wrist.

The pronator teres and the pronator square perform the function of pronation of the forearm, the movement of turning the forearm so that the palm is towards the ground, while the instep supports the function of supinating the forearm, the movement of turning the forearm to than palm up. The biceps brachii and brachioradialis also help supinate the forearm.

The superficial flexor of the fingers and the deep flexor of the fingers control flexion of the fingers, while the extensor of the fingers controls the extension of the fingers. The index and little fingers also receive additional signals from the extensor digitorum, which extends the index finger, and from the extensor digitorum minimus, which extends the little finger.

The thumb has its own set of muscles, which includes the long flexor of the thumb, which flexes the thumb, the extensor pollicis longus and the extensor pollicis brevis, which extends the thumb, and the abductor pollicis longus, which abducts the thumb, perpendicular movement of the thumb of the palm.

Related conditions

Neuromuscular disorders

Neuromuscular disorders are conditions that affect the nerves that send electrical signals to the muscles to control movement. Symptoms of these disorders include muscle weakness, muscle atrophy called atrophy, muscle spasms, cramps or spasms, muscle pain, numbness and tingling, and decreased coordination and fine motor skills.

Many neuromuscular disorders are inherited, but they can also be acquired for reasons that are not fully understood, including spontaneous genetic mutations and impaired immune systems.

Common neuromuscular disorders that can affect the muscles of the arms include:

Trauma, damage

Hand injuries or injuries can cause a variety of problems, including pain, weakness, and difficulty with daily and work tasks.

Common injuries that affect the arm muscles include:

Tests

Several tests are used to confirm the diagnosis of an arm muscle injury or disorder, including:

  • Magnetic Resonance Imaging (MRI): An MRI is a scan that provides a clear image of soft tissue structures, including muscles and tendons, to detect muscle tears or tendinitis, which is an inflammation of a muscle tendon.
  • Electromyography (EMG): The EMG test can be used to assess the electrical activity of your muscles. Electrical activity is often reduced in neuromuscular disorders.
  • Nerve conduction tests: Nerve conduction tests can be used to evaluate how signals travel from the nerves to the muscles. Signal transmission can be delayed by nerve compression or neuromuscular disease.
  • Muscle biopsy: A muscle biopsy involves taking a sample of muscle tissue to check its quality.
  • Genetic Testing: Many neuromuscular disorders are inherited. Genetic testing can examine specific genes and mutations associated with neuromuscular disorders to determine the diagnosis or risk of developing the disease.

Get the word of drug information

The upper and lower arms are made up of 24 different muscles. Problems can arise from injuries, frequent use, or neuromuscular disorders that cause muscle weakness in the elbows, forearms, wrists, or fingers. This weakness can interfere with your ability to complete daily tasks. Allow injured or overworked muscles to rest to relieve pain and discomfort. A visit to a physical therapist will help you return to your daily activities and exercise without restrictions.

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