7.4: Bones of the Pectoral Girdle and Upper Limb

  1. Describe the location, structural features, and functions of the bones of the pectoral girdle

  2. Describe the location, structural features, and functions of the bones of the upper limb

  1. The Pectoral Girdle

    • Location: The pectoral girdle consists of the clavicle and the scapula, which function to attach the upper limb to the axial skeleton at the sternoclavicular joint.

    • The Clavicle (Collarbone):

      • Structural Features: An S-shaped bone. The sternal end (medial) is blunt and articulates with the manubrium, forming the sternoclavicular joint; the acromial end (lateral) is broad and flat, articulating with the scapula, forming the acromioclavicular joint. Near the acromial end is the conoid tubercle, where ligaments attach

      • Functions: Acts as a brace to keep the upper limb away from the thorax and transmits mechanical forces from the upper limb to the axial skeleton.

    • The Scapula (Shoulder Blade):

      • Location: Situated on the posterior aspect of the rib cage, spanning from ribs 22 to 77.

      • Structural Features:

      • Body: Largest part; has three boarders, or angles, superior, lateral, and medial angles

      • Spine: A prominent ridge on the posterior surface, which terminates at the acromion.

      • Acromion: The lateral tip of the spine that articulates with the clavicle.

      • Coracoid Process: An anterior projection for muscle attachment.

      • Glenoid Cavity: A shallow socket just lateral the lateral border that articulates with the head of the humerus.

      • Fossae: Includes the supraspinous (above the spine of the scaps), infraspinous (below spine), and subscapular (inferior coracoid process) fossae for muscle attachment.

      • Functions: Provides highly mobile attachment points for muscles that move the humerus and various motions of the shoulder.

  2. The Upper Limb

    • Location: Comprises the bones of the arm, forearm, and hand.

    • The Humerus (Arm):

      • Structural Features:

        • The largest bone of the upper limb.

        • a proximal (humeral) head articulates with the glenoid cavity of the shoulder, surrounding the head is the anatomical neck

        • greater tubercle (lateral the neck) and lesser tubercles separated by the bicipital groove, and a deltoid tuberosity for muscle attachment.

        • between the diaphysis and the anatomical neck is the surgical neck, but the diaphysis has one projection, called the deltoid tuberosity, and one radial groove for nerves

        • The distal end includes the flared ends: the lateral and medial epicondyle

        • The capitulum (lateral) and trochlea (medial) allow for articulation with the radius and ulna, respectively.

        • Proximal of the capitulum and trochlea and on the anterior are the lateral radial fossa and coronoid fossa; posteriorly is the olecranon fossa

        • Functions: Serves as a lever for the muscles of the arm and facilitates movements at the shoulder and elbow.

    • The Forearm (Radius and Ulna):

      • Ulna (Medial): Features the olecranon (point of the elbow) and the trochlear notch, which grips the humerus.

      • Radius (Lateral): Features a disc-shaped head that allows for rotation (pronation and supination) and a radial tuberosity.

      • Interosseous Membrane: A fibrous sheet connecting the two bones along their shafts. Distributes force more evenly between bones

      • Articulate with each other at the radioulnar joints (distal and proximal ends)

      • Ulna (Medial):

        • Olecranon: The large, bony prominence forming the point of the elbow.

        • Trochlear Notch: A U-shaped notch that grips the trochlea of the humerus. Proximal

        • Coronoid Process: Anterior projection that fits into the coronoid fossa of the humerus during flexion.

        • Radial Notch: Located on the lateral side of the coronoid process for articulation with the radius.

        • Ulnar Head and Styloid Process: Located at the distal end.

      • Radius (Lateral):

        • Radial Head: A disc-shaped proximal end that articulates with the capitulum and the ulna, allowing for rotation (pronation and supination).

        • Radial Tuberosity: Site of attachment for the biceps brachii muscle.

        • Ulnar Notch: Distal indentation for articulation with the ulna.

        • Styloid Process: Bony projection on the lateral distal end, forms lateral boundary of the wrist and aids in support

      • Interosseous Membrane: A strong fibrous sheet connecting the shafts of the radius and ulna.

    • The Hand (Manus):

      • Carpals: Proximal Row:

        • Scaphoid: Boat-shaped; most common carpal bone to be fractured; articulates with the radius

        • Lunate: Moon-shaped; articulates with the radius, but contacts with the ulna

        • Triquetrum: Pyramidal or three-cornered bone, articulates with the ulna

        • Pisiform: Small, pea-shaped; articulates with the anterior surface of the triquetrum

      • Distal Row:

        • Trapezium: Articulates with the thumb / proximally with the scaphoid (first metacarpal).

        • Trapezoid: Wedge-shaped bone; articulates with scaphoid proximally

        • Capitate: Largest carpal bone; centered in the wrist; articulates proximally with lunate and scaphoid

        • Hamate: Identified by its hook-like process (hamulus); proximally articulates with the triquetrum

      • Metacarpals: 55 bones that form the palm, numbered 11 (lateral/thumb) to 55 (medial/pinky).

        • Each metacarpal has 3 parts proximal epiphysis (base), diaphysis (body), and distal epiphysis (head)

      • Phalanges: 1414 bones that form the fingers. Each finger has a proximal, middle, and distal phalanx, except the thumb (pollex), which has only proximal and distal.

    • Functions: Specialized for grasping, manipulation, and fine motor tasks.