Anatomy of Upper Limb

The arm, forearm, wrist, and hand are all parts of the upper limb. The clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, and phalanges are among the upper limb's bones. The sternoclavicular joint is where the upper limb is joined to the axial bone.

Read this blog further to get a quick overview of this important topic for anatomy preparation and ace your NEET PG exam preparation.

WHAT ARE THE BONES OF UPPER LIMB?

Bones of upper limb include:

• Clavicle: It is an S-shaped bone that joins the sternum to the scapula.
• Scapula: it is a triangular-shaped, flat bone that rests on the back of the rib cage.
• Humerus: The upper arm's long bone that joins the scapula and radius at the elbow.
• Radius is the forearm bone that articulates with the humerus and ulna on the side.
• Ulna: The medial forearm bone that articulates with the humerus and radius is the ulna.
• Carpals: The wrist is made up of a number of tiny bones.
• Metacarpals: The five long bones that make up the hand's palm are called this.
• Phalanges- these bones make up the fingers.

What Are The Muscles of the Upper Limb?

Upper limb Muscles: Based on their position, activity, and function, the upper limb muscles can be divided into a variety of groups. The following are some of the major groups of muscles in the upper limb:

1. Shoulder muscles

• The deltoid muscle moves the shoulder joint to abduct the arm.
•  pectoralis major: Adducts and medially rotates the arm at the shoulder joint when the pectoralis major muscle is contracted.
• The latissimus dorsi muscle stretches and adducts the arm at the shoulder joint.
•  Rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, and teres minor): These muscles help with rotation and stabilize the shoulder joint.

2. Muscles in the arms:

•  The biceps brachii muscle, which flexes the elbow joint and supinates the forearm.
•   Triceps brachii muscle: Allows for elbow extension.

3. The flexor muscles in the forearm - These allow you to flex your wrist and fingers.Flexes the wrist and abducts the hand while using the flexor carpi radialis muscle.The flexor carpi ulnaris muscle adducts the hand and flexes the wrist.• Palmaris longus muscle: Tends the palmar aponeurosis and flexes the wrist.• The proximal interphalangeal joints of the fingers and the wrist are flexed by the flexor digitorum superficialis muscle.Flexing the wrist and the distal interphalangeal joints of the fingers is accomplished by the flexor digitorum profundus muscle.The distal phalanx of the thumb is flexed by the flexor pollicis longus muscle.

4. Extensor muscles: Extend your fingers and wrist.Muscle Extensor Carpi Radialis Longus: Abducts the hand and extends the wrist.Muscle Extensor Carpi Radialis Brevis: Abducts the hand and extends the wrist.• Muscle extensor carpi ulnaris: Adducts the hand and extends the wrist.The muscle known as the extensor digitorum extends the wrist and fingers.The muscle known as the extensor pollicis longus extends the thumb's distal phalanx.The proximal phalanx of the thumb is extended by the extensor pollicis brevis muscle.

5. Hand muscles

 Intrinsic muscles: Manage the delicate movements of the thumb and fingers

• Lumbrical muscles: Extend the fingers' interphalangeal joints and flex the metacarpophalangeal joints.
• Interossei muscles: The fingers can be abducted or added
• Thumb abduction and flexion via thenar muscles
• Hypothenar muscles: The little finger can be adducted and flexed.

 Extrinsic muscles Manage finger and hand motion.

• The muscle known as the flexor digitorum superficialis bends the fingers' proximal interphalangeal joints.
• The distal interphalangeal joints of the fingers are flexed by the muscle known as the flexor digitorum profundus.The muscle known as Extensor Digitorum extends the fingers.
• The muscles of the upper limb function as a unit to create a variety of motions, provide stability, and fine motor control for the arm, forearm, wrist, and hand.

What Is The Blood Supply of Upper Limb?

The subclavian artery, a significant artery that emerges from the aortic arch, is the source of a network of blood arteries that supply the upper limb. Three major branches emerge from the subclavian artery to feed blood to the upper limb:

1. Axillary artery: Running through the axilla (armpit), the axillary artery is a continuation of the subclavian artery. It sprouts a number of branches that supply the muscles and supporting tissues of the shoulder with blood.

2. Brachial artery: The brachial artery, which runs along the medial aspect of the arm, is the primary artery of the upper arm. It sprouts a number of branches that feed blood to the arm's muscles and supporting tissues.

3. Radial and ulnar arteries: In the forearm, the brachial artery splits into the radial and ulnar arteries. The muscles and skeletal components of the forearm and hand are supplied with blood by these arteries.

Along with the blood vessels in the upper limb, there are veins that return the deoxygenated blood to the heart. The basilic vein and cephalic vein, which both travel along the arm's medial and lateral sides, respectively, are two of the upper limb's veins. These veins combine to produce the subclavian vein, or axillary vein, in the axilla.

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Venous drainage of the upper limb:

The subclavian artery, a significant artery that emerges from the aortic arch, is the source of a network of blood arteries that supply the upper limb. Three major branches emerge from the subclavian artery to feed blood to the upper limb:

1. Axillary artery: Running through the axilla (armpit), the axillary artery is a continuation of the subclavian artery. It sprouts a number of branches that supply the muscles and supporting tissues of the shoulder with blood.

2. Brachial artery: The brachial artery, which runs along the medial aspect of the arm, is the primary artery of the upper arm. It sprouts the cephalic vein, which runs along the lateral aspect of the arm, and the basilic vein, which runs down the medial aspect of the arm. The median cubital vein, which is frequently used to take blood, is formed when these two veins combine in the area of the elbow. Number of branches that feed blood to the arm's muscles and supporting tissues.

Lymphatic drainage of the upper limb:

Upper limb lymphatic drainage: The lymphatic system in the upper limb is a critical component of the immune system and protects the body from infection. The lymph nodes in the area of the axilla are where the lymphatic veins of the upper limb empty into. The three levels of axillary lymph nodes are level I, deep to the pectoralis minor muscle, and level II, along the subclavian vein. Level I is situated along the lateral border of the pectoralis minor muscle.

The superficial and deep lymphatic veins carry lymph from the hand and fingers to the lymph nodes in the axilla region. 

In addition to draining into the axillary lymph nodes, the lymphatic arteries from the forearm, arm, and shoulder also receive drainage from the lymph nodes in the cervical and supraclavicular areas.

In conclusion, lymphatic drainage is critical for eliminating waste products and protecting the body from infection, while the venous drainage of the upper leg is crucial for returning deoxygenated blood to the heart.

Also Read : Dislocated Shoulder: Causes, Symptoms, Risk Factors, Diagnosis, Treatment, Prevention and Complications

Nerve innervation of the upper limb:

Upper limb nerve innervation: 

The brachial plexus, a network of nerves that emerges from the spinal cord at the level of the fifth cervical vertebra (C5) to the first thoracic vertebra (T1), is the source of the nerves that innervate the upper limb. Five main nerves originate from the brachial plexus and innervate the upper limb:

1. Axillary nerve (C5-C6): The axillary nerve supplies the deltoid and teres minor muscles with nerve fibres.
2. Musculocutaneous nerve (C5-C7): This nerve supplies the biceps brachii, brachialis, and coracobrachialis muscles with sensory information.
3. Radial nerve (C5-T1): The radial nerve is responsible for innervating the muscles of the triceps brachii, brachioradialis, extensor carpi radialis, extensor carpi ulnaris, and extensor digitorum.
4. Median nerve (C5-T1): The median nerve supplies the pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum profundus, and flexor digitorum superficialis muscles.
5. Ulnar nerve (C8-T1): The ulnar nerve supplies the intrinsic hand muscles, such as the lumbrical, interossei, and hypothenar muscles, as well as the flexor digitorum profundus and flexor carpi ulnaris.

Both motor and sensory innervation are provided by the upper limb's nerves. These nerves not only regulate muscle contractions but also provide touch, temperature, and pain signals from the skin and other tissues of the upper limb back to the spinal cord and brain.

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