Anatomy Study Notes: Upper Limb Osteology

Gross Anatomy of Upper and Lower Limbs

Introduction to Osteology

  • Osteology: The study of bones.

  • The upper limbs are anatomically divided into four main segments:

    • Pectoral girdle: Comprising the scapula and clavicle.

    • Arm: Dominated by the humerus.

    • Forearm: Comprising the radius and ulna.

    • Hand: Composed of carpals, metacarpals, and phalanges.

Joints of the Upper Limb

  • Glenohumeral Joint: The shoulder joint formed by the articulation between the head of the humerus and the glenoid cavity of the scapula.

  • Elbow Joint: Connects the humerus with the radius and ulna.

  • Wrist Joint: Involves the radiocarpal joint, connecting the radius with the carpal bones.

  • Acromioclavicular Joint: Part of the pectoral girdle.

  • Key joints and components:

    • Acromioclavicular joint

    • Glenohumeral joint

    • Elbow joint

    • Distal radioulnar joint

    • Wrist joint

  • Carpal Bones: 8 in total.

  • Metacarpals: 5 in total.

  • Phalanges: 14 in total (3 per finger, 2 in the thumb).

The Humerus

Overview

  • Humerus: The largest bone in the upper limb.

  • Connects at two major joints:

    • Glenohumeral joint (with scapula)

    • Elbow joint (with radius and ulna)

  • Structure: Consists of a proximal end, a shaft, and a distal end.

Proximal End of Humerus

  • Contains:

    • Head: Ball-shaped and articulates with the scapula.

    • Anatomical neck: A groove encircling the head, distinct from the tubercles.

    • Greater tubercle: Located laterally; provides attachment for three muscles.

    • Lesser tubercle: Projects anteriorly; serves as an attachment point for subscapularis.

    • Intertubercular groove: Also known as bicipital groove; contains the long head of biceps and branches of the anterior circumflex humeral artery.

Shaft of Humerus

  • Deltoid Tuberosity: Lateral aspect; site for attachment of the deltoid muscle.

  • Radial Groove: Posterior aspect; contains the radial nerve and deep artery of the arm.

Distal End of Humerus

  • Condyle: Broader end of the humerus; consists of:

    • Capitulum: Articulates with the radius.

    • Trochlea: Articulates with the ulna.

  • Epicondyles: Lateral and medial prominent features for muscle attachment;

    • Medial epicondyle: Attaches to forearm flexors and ulnar nerve.

    • Lateral epicondyle: Attaches to forearm extensors.

  • Fossae:

    • Coronoid fossa: Accommodates the coronoid process of the ulna during flexion.

    • Olecranon fossa: Receives the olecranon of the ulna during extension.

    • Radial fossa: Accommodates the head of the radius when the forearm is flexed.

Applied Anatomy of Humerus

  • Fractures: Common sites are the surgical neck, shaft, and supracondylar region. Injuries related to these locations include:

    • Surgical neck: Associated with injury to axillary nerve and circumflex humeral arteries.

    • Radial groove: Damage to radial nerve.

    • Distal end: Involves median nerve.

The Ulna

Overview

  • Ulna: Medial and longer of the two forearm bones.

  • It articulates with the trochlea of the humerus and the radius.

  • Structure: Comprises a proximal end, body, and distal end.

Proximal End of Ulna

  • Features two prominent projections:

    • Olecranon: Projects posteriorly.

    • Coronoid process: Projects anteriorly.

  • Trochlear notch: Articulates with the trochlea of the humerus.

  • Radial notch: On the lateral side, where it articulates with the radius.

  • Infra-corner is the tuberosity of ulna for biceps tendon attachment.

Body and Distal End of Ulna

  • The body tapers distally; at the end, there is a disc-like head and a conical styloid process.

The Radius

Overview

  • Radius: Lateral and shorter of the two forearm bones.

  • The proximal end has:

    • A cylindrical head for articulation with the humerus.

    • A neck and a radial tuberosity for biceps attachment.

  • The body widens distally.

Distal End of Radius

  • The distal end has a rectangular cross-section.

  • Contains the ulna notch for the ulna's head and the styloid process on the lateral aspect.

Bones of the Hand

Composition

  • The hand skeleton includes the metacarpals and phalanges:

  • Metacarpus: 5 metacarpal bones, each with a body and two ends.

  • Phalanges: Each digit has 3 phalanges except for the thumb which has 2.

Carpal Bones

  • The carpus consists of 8 carpal bones arranged in two rows:

    • Proximal Row: From lateral to medial - Scaphoid, Lunate, Triquetrum, Pisiform.

    • Distal Row: From lateral to medial - Trapezium, Trapezoid, Capitate, Hamate (with a hook-like process called the hook of hamate).