8.2

Bones of the Upper Limb

Learning Objectives

  • Identify the divisions of the upper limb and describe the bones in each region.

  • List the bones and bony landmarks that articulate at each joint of the upper limb.

Divisions of the Upper Limb

  • The upper limb is divided into three regions:

  • Arm: Located between the shoulder and elbow joints.

  • Forearm: Located between the elbow and wrist joints.

  • Hand: Located distal to the wrist.

  • Total Bones in Each Upper Limb: 30 bones.

  • Upper Arm: 1 bone (Humerus).

  • Forearm: 2 bones (Ulna - medial; Radius - lateral).

  • Base of Hand: 8 carpal bones.

  • Palm of Hand: 5 metacarpal bones.

  • Fingers/Thumb: 14 phalanx bones.

Humerus

  • The only bone in the upper arm region.

  • ### Structure of Humerus

  • Proximal End: (Head): Large, round, smooth region that faces medially, articulates with the glenoid cavity of the scapula to form the glenohumeral (shoulder) joint.

  • Anatomical Neck: Margin of the head's smooth area.

  • Greater Tubercle: Expanded bony area on the lateral side of the proximal humerus.

  • Lesser Tubercle: Smaller bony area found on the anterior aspect.

  • Intertubercular Groove (Sulcus): Passage for the tendon of the biceps brachii muscle; located between the greater and lesser tubercles.

  • Surgical Neck: Located at the humerus shaft's base; a common site for fractures.

  • Deltoid Tuberosity: Roughened, V-shaped area on the lateral side of the humerus shaft; site of attachment for the deltoid muscle.

  • ### Distal End of Humerus

  • Articulates with: Radius and Ulna to form the elbow joint.

  • Medial Epicondyle: Larger projection on the medial side; serves as an attachment point for forearm muscles.

  • Lateral Epicondyle: Smaller projection on the lateral side.

  • Trochlea: Spindle-shaped region, articulates with the ulna.

  • Capitulum: Knob-like structure that articulates with the radius.

  • Coronoid Fossa: Receives the coronoid process of the ulna when the elbow is flexed.

  • Radial Fossa: Receives the head of the radius during elbow flexion.

  • Olecranon Fossa: Larger depression on the posterior side, receives the olecranon process of the ulna during forearm extension.

Ulna

  • The medial bone of the forearm, runs parallel to the radius.

  • ### Structure of Ulna

  • Proximal End: Features a C-shaped trochlear notch, articulates with humerus' trochlea.

  • Coronoid Process: Prominent lip of bone forming the inferior margin of the trochlear notch; roughened area for muscle attachment located below the trochlear notch (Ulnar Tuberosity).

  • Radial Notch: A small area articulating with the proximal radius to form the proximal radioulnar joint.

  • Olecranon Process: Forms the bony tip of the elbow.

  • ### Shaft of Ulna

  • Interosseous Border: Attachment line for the interosseous membrane connecting the ulna and radius.

  • Distal End: Formed by the rounded head of the ulna; includes the Styloid Process of the Ulna, a short bone projection serving as an attachment point.

  • Carrying Angle: The forearm deviates laterally by 5–15 degrees from the arm, allowing freer movement and accommodating wider pelvis in females.

Radius

  • The lateral bone of the forearm.

  • ### Structure of Radius

  • Proximal End: Disc-shaped head; articulates with the capitulum of the humerus and radial notch of the ulna (proximal radioulnar joint).

  • Neck of Radius: Narrow region below the head.

  • Radial Tuberosity: Bony protuberance serving as a muscle attachment point.

  • Shaft: Slightly curved; features an interosseous border for attachment to the interosseous membrane.

  • Distal End: Smooth surface articulates with two carpal bones (distal carpal joint).

    • Ulnar Notch: Articulates with the head of the ulna to form the distal radioulnar joint.

    • Styloid Process of the Radius: Projection that serves as attachment for lateral wrist joint ligaments; projects more distally than radial styloid process.

Carpal Bones

  • Eight small carpal bones form the wrist and hand base.

  • ### Arrangement of Carpal Bones

  • Proximal Row (Lateral to Medial): Scaphoid (boat-shaped), Lunate (moon-shaped), Triquetrum (three-cornered), Pisiform (pea-shaped).

  • Distal Row (Lateral to Medial): Trapezium (table), Trapezoid (resembles a table), Capitate (head-shaped), Hamate (hooked).

  • Mnemonic: “So Long To Pinky, Here Comes The Thumb.”

  • ### Articulations of Carpal Bones

  • Proximal carpal bones articulate with the distal end of the radius and a fibrocartilaginous pad of the ulna.

  • Distal carpal bones articulate with metacarpal bones to form the carpal-metacarpal joints.

Metacarpal Bones

  • Five elongated bones forming the palm of the hand.

  • Articulations: Each metacarpal articulates with one of the distal carpal bones (carpometacarpal joints) and with proximal phalanges at the metacarpophalangeal joints.

  • Numbering: 1–5, starting from the thumb (first metacarpal). Special mobility of the first metacarpal allows for independent thumb motion.

Phalanx Bones

  • Total Count: 14, with each called a phalanx bone.

  • Structure: 2 in the thumb (proximal and distal) and 3 each in fingers 2–5 (proximal, middle, distal).

  • Interphalangeal Joints: Articulations between adjacent phalanges.

  • ## Fractures of Upper Limb Bones

    • Common Injuries: Fractures commonly result from falls onto an outstretched hand.

    • Common Fractures:

    • Humeral Fractures: Could involve the surgical neck or shaft, often resulting in serious complications such as nerve damage or arterial compression.

    • Colles Fracture: A transverse fracture across the distal radius, characterized by a “dinner fork” deformity of the wrist. Most common in individuals over 50, particularly those with osteoporosis.

    • Scaphoid Fracture: The most commonly fractured carpal bone, associated with poor blood supply leading to slow healing and risk of necrosis.

    • Concerns Following Injury: Potential for ischaemia and nerve damage, especially after swelling."}