Pectoral Girdle and Upper Limb Anatomy

Overview of the Pectoral Girdle and Upper Limb Anatomy

Anatomy of the Pectoral Girdle

  • Definition: The pectoral girdle, also known as the shoulder girdle, consists of two main bones: the clavicles and the scapulae.

    • Components:

    • Clavicle (collarbone): An S-shaped bone that is positioned anteriorly.

    • Scapula (shoulder blade): A flat triangular bone located posteriorly.

Clavicle

  • Shape: S-shaped bone that serves as a key support structure in the pectoral girdle.

  • Articulations:

    • Medial end (Sternal end): Articulates with the sternum at the manubrium.

    • Lateral end (Acromial end): Articulates with the scapula at the acromion.

  • Functions:

    • Acts as an anchor for muscles.

    • Serves as a brace to hold the scapula and arms laterally.

  • Landmarks:

    • Conoid tubercle: A bony prominence on the inferior surface of the clavicle.

    • Costoclavicular ligament impression: A feature for ligament attachment on the inferior side.

Scapula

  • Function: The scapula allows for significant mobility of the shoulder joint, not being rigidly attached to the axial skeleton, which contributes to a full range of motion.

  • Articulations:

    • Glenohumeral joint: The joint where the head of the humerus fits into the glenoid cavity of the scapula.

  • Key Features:

    • Glenoid cavity: A shallow socket that accommodates the humeral head.

Mobility of the Pectoral Girdle

  • Mobility Characteristics:

    • Scapula's lack of attachment to the axial skeleton enhances arm mobility.

    • The deep socket configuration leads to a substantial range of motion at the shoulder joint, but it also makes the joint susceptible to dislocations due to its shallowness.

  • Related Joints:

    • Sternoclavicular joint: Joint between the clavicle and the sternum.

    • Acromioclavicular joint: Joint between the clavicle and the acromion of the scapula.

General Structure of the Appendicular Skeleton

  • Definition: The appendicular skeleton consists of limbs and their girdles, which are crucial for body movement.

  • Components:

    • Pectoral girdle: Attaches upper limbs to the body trunk.

    • Pelvic girdle: Attaches lower limbs to the body trunk.

Humerus Anatomy

  • Definition: The humerus is the long bone of the upper arm that articulates with the scapula proximally and the radius and ulna distally.

  • Key Features:

    • Head: The rounded proximal end that fits into the glenoid cavity of the scapula.

    • Anatomical neck: A slight constriction just inferior to the head of the humerus that serves as a landmark.

    • Greater tubercle and Lesser tubercle: Separated by the intertubercular sulcus, these are attachment sites for the rotator cuff muscles.

    • Surgical neck: Located below the tubercles, it is the most frequently fractured part of the humerus.

Articulation of the Humerus with the Radius and Ulna

  • Distal Articulations:

    • The trochlea of the humerus articulates with the ulna, providing a hinge-like movement, while the capitulum articulates with the radius, allowing for rotational movements.

Upper Limb Composition

  • Total Number of Bones: 30 bones form the skeletal framework of each upper limb.

  • Components:

    • Humerus: Bone of the arm.

    • Radius and Ulna: Bones of the forearm.

    • Carpal bones: 8 bones in the wrist.

    • Metacarpal bones: 5 bones in the palm.

    • Phalanges: 14 bones in the fingers.

Bone Markings

  • Humerus:

    • Deltoid tuberosity: A raised area on the shaft of the humerus for muscle attachment.

    • Radial groove: A slight depression that accommodates the radial nerve.

    • Coronoid fossa: A depression that allows the coronoid process of the ulna to fit during arm flexion.

    • Olecranon fossa: A large cavity on the posterior side that accommodates the olecranon of the ulna during extension.