Anatomy of the Clavicle

Clavicle

• Connects the upper limb to the trunk
• Has a double curve in a horizontal plane
• Medial two-thirds convex anteriorly, sternal end articulates with the manubrium of the sternum at the sternoclavicular (SC) joint
• Lateral third flattened and concave anteriorly, acromial end articulates with the acromion of the scapula at the acromioclavicular (AC) joint
• Curvatures increase resilience and give it the appearance of an elongated "S"
• Acts as a movable, crane-like strut supporting the scapula and free limb, keeping them away from the trunk
• Allows the scapula to move on the thoracic wall at the "scapulothoracic joint"
• Enables elevation of ribs for deep inspiration
• Forms one of the bony boundaries of the cervico-axillary canal, protecting the neurovascular bundle supplying the upper limb
• Transmits shocks from the upper limb to the axial skeleton
• Subcutaneous and palpable throughout its length, often used as a landmark in clinical procedures
• Designated as a long bone, has no medullary cavity, consisting of spongy bone with a shell of compact bone
• Superior surface is smooth, lying deep to the skin and platysma muscle in the subcutaneous tissue
• Inferior surface is rough with strong ligaments binding it to the 1st rib near the sternal end and suspending the scapula from the acromial end
• Conoid tubercle near the acromial end gives attachment to the conoid ligament, the medial part of the coracoclavicular ligament
• Trapezoid line also near the acromial end gives attachment to the trapezoid ligament, the lateral part of the coracoclavicular ligament
• Subclavian groove in the medial third of the shaft of the clavicle is the site of attachment of the subclavius muscle
• Impression for the costoclavicular ligament is a rough, often depressed, oval area that gives attachment to the ligament binding the 1st rib to the clavicle

Scapula

• Triangular flat bone lying on the posterolateral aspect of the thorax, overlying the 2nd–7th ribs
• Convex posterior surface divided by the spine of the scapula into a small supraspinous fossa and a larger infraspinous fossa
• Concave costal surface forms a large subscapular fossa
• Three fossae provide attachments for fleshy muscles
• Body is thin and translucent superior and inferior to the spine
• Spine continues laterally as the flat, expanded acromion, forming the subcutaneous point of the shoulder and articulating with the acromial end of the clavicle
• Deltoid tubercle of the scapular spine is the prominence indicating the medial point of attachment of the deltoid
• Spine and acromion serve as levers for attached muscles, particularly the trapezius
• Suspended from the clavicle by the coracoclavicular ligament
• Acromion is a lateral extension, so the AC joint is lateral to the mass of the scapula and its attached muscles
• Glenohumeral (shoulder) joint is inferior to the AC joint
• Glenoid cavity articulates with the head of the humerus at the glenohumeral joint
• Glenoid cavity is a shallow, concave, oval fossa, directed anterolaterally and slightly superiorly
• Coracoid process is superior to the glenoid cavity and projects anterolaterally, resembling a bent finger pointing to the shoulder
• Has medial, lateral, and superior borders, as well as superior, lateral, and inferior angles
• Medial border is parallel to and approximately 5 cm lateral to the spinous processes of the thoracic vertebrae
• Lateral border runs superolaterally toward the apex of the axilla
• Lateral border terminates at the truncated lateral angle of the scapula
• The glenoid cavity is the primary feature of the head
• Shallow constriction between the head and body defines the neck of the scapula
• Superior border is marked near the junction of its medial two thirds and lateral third by the suprascapular notch
• The scapula is capable of considerable movement on the thoracic wall at the physiological scapulothoracic joint, providing the base from which the upper limb operates.

This quiz delves into the anatomy of the clavicle, its structure, and its essential functions in the upper limb's movement and stability. Learn about its articulations, curvatures, and role as a protective structure for the neurovascular bundle. Enhance your understanding of this critical bone and its clinical significance.