Anatomy of Upper Limb

The upper limb is the region of the body that includes the arm, forearm, wrist, and hand. The bones of the upper limb include the clavicle, scapula, humerus, radius, ulna, carpals, metacarpals, and phalanges. The upper limb is attached to the axial skeleton at the sternoclavicular joint.

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

Bones of Upper Limb

• Clavicle: It is an S-shaped bone that connects the sternum to the scapula.
• Scapula: It is a flat, triangular-shaped bone that sits on the posterior aspect of the rib cage.
• Humerus: It is the long bone of the upper arm that articulates with the scapula and radius.
• Radius: It is the lateral bone of the forearm that articulates with the humerus and ulna.
• Ulna: It is the medial bone of the forearm that articulates with the humerus and radius.
• Carpals: These are the small bones that make up the wrist.
• Metacarpals: These are the five long bones that make up the palm of the hand.
• Phalanges: These are the bones that make up the fingers.

Muscles of Upper Limb

The muscles of the upper limb can be classified into different categories based on their location, action, and function. Here are some of the main categories of muscles in the upper limb:

• 1. Shoulder muscles:
  • Deltoid muscle: Abducts the arm at the shoulder joint.
  • Pectoralis major muscle: Adducts and medially rotates the arm at the shoulder joint.
  • Latissimus dorsi muscle: Adducts and extends the arm at the shoulder joint.
  • Rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis): Stabilize the shoulder joint and assist with rotation.
• 2. Arm muscles:
  • Biceps brachii muscle: Flexes the elbow joint and supinates the forearm.
  • Triceps brachii muscle: Extends the elbow joint.
• 3. Forearm muscles:
  • a. Flexor muscles: Flex the wrist and fingers.
    • Flexor carpi radialis muscle: Flexes the wrist and abducts the hand.
    • Flexor carpi ulnaris muscle: Flexes the wrist and adducts the hand.
    • Palmaris longus muscle: Flexes the wrist and tenses the palmar aponeurosis.
    • Flexor digitorum superficialis muscle: Flexes the wrist and the proximal interphalangeal joints of the fingers.
    • Flexor digitorum profundus muscle: Flexes the wrist and the distal interphalangeal joints of the fingers.
    • Flexor pollicis longus muscle: Flexes the distal phalanx of the thumb.
  • b. Extensor muscles: Extend the wrist and fingers.
    • Extensor carpi radialis longus muscle: Extends the wrist and abducts the hand.
    • Extensor carpi radialis brevis muscle: Extends the wrist and abducts the hand.
    • Extensor carpi ulnaris muscle: Extends the wrist and adducts the hand.
    • Extensor digitorum muscle: Extends the wrist and the fingers.
    • Extensor pollicis longus muscle: Extends the distal phalanx of the thumb.
    • Extensor pollicis brevis muscle: Extends the proximal phalanx of the thumb.
• 4.Hand muscles:
  • a. Intrinsic muscles: Control fine movements of the fingers and thumb.
    • Lumbrical muscles: Flex the metacarpophalangeal joints and extend the interphalangeal joints of the fingers.
    • Interossei muscles: Abduct or adduct the fingers.
    • Thenar muscles: Abduct and flex the thumb.
    • Hypothenar muscles: Adduct and flex the little finger.
  • b. Extrinsic muscles: Control movement of the hand and fingers.
    • Flexor digitorum superficialis muscle: Flexes the proximal interphalangeal joints of the fingers.
    • Flexor digitorum profundus muscle: Flexes the distal interphalangeal joints of the fingers.
    • Extensor digitorum muscle: Extends the fingers.

Overall, the muscles of the upper limb work together to produce a wide range of movements and provide stability and fine motor control for the arm, forearm, wrist, and hand.

Blood Supply of Upper Limb:

The upper limb is supplied by a network of blood vessels that originate from the subclavian artery, which is a major artery that arises from the aortic arch. The subclavian artery gives rise to three main branches that supply blood to the upper limb:

1. Axillary artery: The axillary artery is a continuation of the subclavian artery and runs through the axilla (armpit) region. It gives rise to several branches that supply blood to the muscles and structures of the shoulder region.
2. Brachial artery: The brachial artery is the main artery of the upper arm and runs along the medial aspect of the arm. It gives rise to several branches that supply blood to the muscles and structures of the arm.
3. Radial and ulnar arteries: The brachial artery bifurcates into the radial and ulnar arteries in the forearm. These arteries supply blood to the muscles and structures of the forearm and hand. The blood vessels of the upper limb are also accompanied by veins that carry deoxygenated blood back to the heart. The veins of the upper limb include the cephalic vein, which runs along the lateral aspect of the arm, and the basilic vein, which runs along the medial aspect of the arm. These veins merge to form the axillary vein in the axilla, which then becomes the subclavian vein.

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Venous drainage of the upper limb:

The veins of the upper limb can be divided into superficial and deep veins. The superficial veins are located just below the skin and drain into the deep veins, which are located deeper in the tissue. The deep veins of the upper limb follow the same course as the arteries and have the same names. The veins of the upper limb ultimately drain into the axillary vein, which then becomes the subclavian vein.

The main superficial veins of the upper limb include the cephalic vein, which runs along the lateral aspect of the arm, and the basilic vein, which runs along the medial aspect of the arm. These two veins unite in the region of the elbow to form the median cubital vein, which is commonly used for drawing blood.

Lymphatic Drainage of the Upper Limb:

The lymphatic system of the upper limb is an important part of the immune system and plays a crucial role in defending the body against infection. The lymphatic vessels of the upper limb drain into lymph nodes located in the axilla region. The axillary lymph nodes are grouped into three levels: level I is located along the lateral border of the pectoralis minor muscle, level II is located deep to the pectoralis minor muscle, and level III is located along the subclavian vein.

The lymphatic vessels from the hand and fingers drain into the lymph nodes in the axilla region via the superficial and deep lymphatic vessels. The lymphatic vessels from the forearm, arm, and shoulder also drain into the axillary lymph nodes, but they also receive drainage from the lymph nodes in the cervical and supraclavicular regions.

In summary, the venous drainage of the upper limb is important for carrying deoxygenated blood back to the heart, while the lymphatic drainage is important for removing waste products and defending the body against infection.

Nerve Innervation of Upper Limb:

The nerves that innervate the upper limb originate from the brachial plexus, which is a network of nerves that arises from the spinal cord at the level of the fifth cervical vertebra (C5) to the first thoracic vertebra (T1). The brachial plexus gives rise to five major nerves that innervate the upper limb:

1. Axillary nerve (C5-C6): The axillary nerve innervates the deltoid muscle and the teres minor muscle.
2. Musculocutaneous nerve (C5-C7): The musculocutaneous nerve innervates the biceps brachii muscle, the brachialis muscle, and the coracobrachialis muscle.
3. Radial nerve (C5-T1): The radial nerve innervates the triceps brachii muscle, the brachioradialis muscle, the extensor carpi radialis muscle, the extensor carpi ulnaris muscle, and the extensor digitorum muscle.
4. Median nerve (C5-T1): The median nerve innervates the flexor carpi radialis muscle, the palmaris longus muscle, the flexor digitorum superficialis muscle, the flexor digitorum profundus muscle, and the pronator teres muscle.
5. Ulnar nerve (C8-T1): The ulnar nerve innervates the flexor carpi ulnaris muscle, the flexor digitorum profundus muscle, and the intrinsic muscles of the hand, including the hypothenar muscles, the interossei muscles, and the lumbrical muscles.

The nerves of the upper limb provide both motor and sensory innervation. In addition to controlling muscle movements, these nerves also transmit sensory information, such as touch, temperature, and pain, from the skin and other tissues of the upper limb back to the spinal cord and brain.

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