Anatomy of the Arm

The human arm is a complex structure that plays a vital role in movement, strength, and fine motor skills. Understanding its anatomy requires a systematic approach, moving step by step from bones to clinical relevance. This study plan is designed to help students and learners build a strong foundation in the anatomy of the arm.

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1. Introduction to the Arm

The arm (brachium) is the region between the shoulder and the elbow. It is important to differentiate the arm from neighboring regions:

• Arm (Brachium): Extends from the shoulder to the elbow.
• Forearm (Antebrachium): Lies between the elbow and the wrist.
• Hand (Manus): Extends beyond the wrist and contains the palm and fingers.

This distinction ensures clarity when studying anatomical structures.

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2. Bones of the Arm

The main bone of the arm is the humerus, a long bone that articulates with the scapula at the shoulder joint and with the radius and ulna at the elbow joint. Key features include:

• Head: Articulates with the glenoid cavity of the scapula.
• Shaft: Contains the radial groove where the radial nerve passes.
• Condyles: Trochlea and capitulum at the distal end for articulation with the forearm bones.
• Landmarks: Greater tubercle, lesser tubercle, deltoid tuberosity, and olecranon fossa.

Studying these with diagrams enhances understanding of their spatial orientation.

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Arm anatomy

3. Joints of the Arm

The arm contributes to major upper limb joints:

• Shoulder joint (glenohumeral): A ball-and-socket joint allowing wide range of movements.
• Elbow joint: A hinge-type joint made of:
  • Humeroulnar
  • Humeroradial
  • Proximal radioulnar

Movements possible: flexion, extension, pronation, and supination.

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4. Muscles of the Arm

Muscles are divided into compartments:

Anterior Compartment (Flexors, Musculocutaneous nerve):

• Biceps brachii
• Brachialis
• Coracobrachialis

Posterior Compartment (Extensors, Radial nerve):

• Triceps brachii
• Anconeus

Each muscle should be studied in terms of origin, insertion, action, and innervation.

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Arm anatomy

5. Blood Supply

• Arteries:

  • The brachial artery is the main blood supply.
  • Important branches: profunda brachii, superior ulnar collateral, and inferior ulnar collateral arteries.

• Veins:

  • Superficial veins: cephalic, basilic, and median cubital (commonly used for venipuncture).
  • Deep veins: paired brachial veins accompanying the artery.

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6. Nerve Supply

Derived from the brachial plexus:

• Musculocutaneous nerve → anterior compartment.
• Radial nerve → posterior compartment.
• Median and ulnar nerves → pass through the arm without major innervation.

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7. Surface Anatomy

Key visible and palpable features include:

• Biceps bulge.
• Brachial artery pulse (medial to the biceps tendon).
• Cubital fossa at the front of the elbow.
• Triceps and posterior groove landmarks.

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8. Clinical Correlations

Knowledge of arm anatomy has direct clinical applications:

• Humerus fracture: Midshaft fractures may injure the radial nerve.
• Brachial artery injury: May cause severe bleeding.
• Venipuncture: Performed at the median cubital vein.
• Compartment syndrome: Increased pressure in fascial compartments can damage nerves and blood vessels.

 Tip: Always study in layers—start with bones → muscles → vessels → nerves → clinical aspects. This structured method builds strong anatomical knowledge and helps link theory with practical applications.

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Blood Supply of the Arm

Arterial Supply

1. Main Source

• The arterial supply of the upper limb originates from the subclavian artery.
• After crossing the lateral border of the 1st rib, it becomes the axillary artery, which continues as the brachial artery at the lower border of teres major.

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2. Axillary Artery

• Divided into three parts by the pectoralis minor muscle:
  1. First part (proximal to pectoralis minor)
  2. Branch: Superior thoracic artery → supplies upper thoracic wall and first two intercostal spaces.
  3. Second part (posterior to pectoralis minor)
  4. Branches:
  5. Thoracoacromial artery → pectoral, deltoid, clavicular, and acromial branches.
  6. Lateral thoracic artery → supplies serratus anterior, pectoral muscles, breast.
  7. Third part (distal to pectoralis minor)
  8. Branches:
  9. Subscapular artery → circumflex scapular + thoracodorsal branches.
  10. Anterior circumflex humeral artery
  11. Posterior circumflex humeral artery (larger, accompanies axillary nerve around surgical neck of humerus).

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3. Brachial Artery

• Continuation of the axillary artery at lower border of teres major.
• Descends along the medial side of the arm with the median nerve.
• Terminates in the cubital fossa (near neck of radius) by dividing into radial and ulnar arteries.

Major branches:

• Profunda brachii artery (deep artery of the arm):

1. Largest branch, arises near beginning of brachial artery.
2. Runs with radial nerve in radial groove of humerus.
3. Supplies posterior compartment (triceps) and participates in elbow anastomosis.

• Superior ulnar collateral artery (with ulnar nerve).
• Inferior ulnar collateral artery.

Muscular branches to biceps, brachialis, coracobrachialis.

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4. Radial and Ulnar Arteries

• Radial artery:
  • Smaller terminal branch, runs along lateral forearm with radial nerve (superficial branch).
  • Passes around lateral wrist into dorsum, then into palm to form deep palmar arch.
  • Supplies lateral forearm, thumb, lateral 2½ fingers.
• Ulnar artery:
  • Larger branch, runs medially with ulnar nerve in distal forearm.
  • Gives off common interosseous artery → anterior & posterior interosseous arteries.
  • Enters palm via Guyon’s canal, forms superficial palmar arch.
  • Supplies medial forearm, medial 3½ fingers.

Hand Supply:

• Superficial palmar arch (mainly ulnar artery, completed by superficial branch of radial).
• Deep palmar arch (mainly radial artery, completed by deep branch of ulnar).

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Venous Drainage

1. Superficial Veins (Subcutaneous, Independent of Arteries)

• Cephalic vein:
  • From lateral side of dorsum of hand → ascends lateral forearm/arm → drains into axillary vein via deltopectoral groove.
• Basilic vein:
  • From medial side of dorsum of hand → ascends medial forearm/arm → joins brachial veins → forms axillary vein.
• Median cubital vein:
  • Connects cephalic and basilic veins at cubital fossa.
  • Common site for venipuncture due to accessibility and stability.

2. Deep Veins (Venae comitantes)

• Paired veins accompany arteries (radial, ulnar, brachial).
• Merge with basilic vein to form axillary vein, which continues as subclavian vein.

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Arterial Anastomoses Around Elbow

• Provide collateral circulation if brachial artery is compressed or injured.
• Collateral arteries (from brachial and profunda brachii):
  • Radial collateral artery.
  • Middle collateral artery.
  • Superior and inferior ulnar collateral arteries.
• Recurrent arteries (from radial and ulnar):
  • Radial recurrent artery.
  • Anterior and posterior ulnar recurrent arteries.
  • Interosseous recurrent artery.

Clinical importance: Maintains distal limb perfusion if brachial artery is ligated above the elbow.

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Clinical Notes

1. Brachial artery injury:
   • Common at the supracondylar region of humerus.
   • Risk of Volkmann’s ischemic contracture due to ischemia of forearm flexors.
2. Thrombosis/Embolism:
   • May block radial or ulnar arteries → ischemia of hand.
3. Venous access:
   • Median cubital vein → most common site for IV access, blood sampling.
   • Risk: injury to underlying structures if needle passes too deep.
4. Radial artery:
   • Common site for pulse palpation at wrist.
   • Used for arterial blood gas (ABG) sampling or coronary bypass grafting.

common diseases and conditions affecting the arm:

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1. Musculoskeletal Disorders

• Fractures – Breaks in bones such as the humerus, radius, or ulna due to trauma or falls.
• Dislocations – Commonly seen in the shoulder joint, where the humeral head slips out of the socket.
• Tendinitis – Inflammation of tendons, often affecting the biceps or triceps due to overuse.
• Tennis Elbow (Lateral Epicondylitis) – Pain on the outer side of the elbow caused by repetitive strain.
• Golfer’s Elbow (Medial Epicondylitis) – Pain on the inner side of the elbow due to repetitive wrist and arm movements.
• Carpal Tunnel Syndrome – Compression of the median nerve in the wrist, causing pain, tingling, and numbness in the hand and forearm.

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2. Nerve-Related Conditions

• Brachial Plexus Injury – Damage to the nerve network controlling the shoulder, arm, and hand.
• Radial Nerve Palsy (Saturday Night Palsy) – Leads to wrist drop and weakness due to nerve compression.
• Ulnar Nerve Entrapment – Causes tingling in the ring and little finger (“cubital tunnel syndrome”).

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3. Circulatory Disorders

• Deep Vein Thrombosis (DVT) of the Arm – A blood clot in arm veins causing swelling and pain.
• Peripheral Artery Disease (PAD) – Narrowing of arteries reduces blood flow to the arm.
• Lymphedema – Swelling due to blocked lymphatic drainage, often after surgery or infection.

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4. Infections & Inflammatory Conditions

• Cellulitis – Bacterial infection of skin and soft tissue, causing redness and swelling.
• Abscesses – Pus-filled swellings in muscles or under skin.
• Septic Arthritis – Infection in the elbow or shoulder joint.
• Bursitis – Inflammation of the fluid-filled sacs (bursae), commonly in the elbow (olecranon bursitis).

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5. Chronic & Degenerative Diseases

• Osteoarthritis – Degeneration of cartilage in shoulder or elbow joints, leading to stiffness and pain.
• Rheumatoid Arthritis – Autoimmune condition causing inflammation in multiple arm joints.
• Osteoporosis – Weak bones prone to fractures in the arm.

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6. Tumors and Growths

• Benign Bone Tumors – Such as osteochondroma in the humerus.
• Malignant Bone Tumors – Osteosarcoma, Ewing’s sarcoma (rare but serious).
• Soft Tissue Tumors – Lipomas (fatty lumps), sarcomas.