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Shoulder Girdle: Clavicle & Scapula
Shoulder Girdle: Clavicle & Scapula
Includes labeled diagrams, downloadable notes, anatomy quizzes, and interactive learning tools
The shoulder girdle connects each upper limb to the axial skeleton and is made up of two bones on each side: the clavicle and the scapula. These bones work together to anchor muscles and allow a wide range of movements of the arm.
Unlike the pelvis, the right and left pectoral girdles are not directly joined, and each is attached to the axial skeleton by only one highly mobile joint. This design provides the upper limb with a high degree of flexibility and freedom of movement.
Clavicle
The clavicle, or collarbone, is a long, S-shaped bone that lies horizontally across the front of the shoulder, just above the first rib. Structurally has three main anatomical parts:
medial (sternal) end
lateral (acromial) end
shaft
The medial part is more rounded, while the lateral part is flatter.
The bone has a double curvature, being convex anteriorly near the sternum and concave anteriorly near the scapula. Various muscles attach along its surfaces, including the deltoid, trapezius, pectoralis major, and sternocleidomastoid.
Its medial (sternal) end articulates with the manubrium of the sternum, forming the sternoclavicular joint, which is the only direct bony connection between the upper limb and the axial skeleton.
Its lateral (acromial) end articulates with the acromion of the scapula, forming the acromioclavicular joint.
The clavicle acts as a strut that holds the scapula and shoulder joint laterally away from the body, allowing for greater mobility of the arm. It also transmits forces from the upper limb to the trunk and protects important underlying nerves and blood vessels.
The clavicle is the most commonly fractured bone in the body, often due to falls on an outstretched hand or direct blows to the shoulder. When fractured, the weight of the limb may cause the shoulder to drop, and muscle forces may pull the bone fragments out of alignment.
Scapula
The scapula (shoulder blade) is a flat, triangular bone located on the posterior side of the shoulder. It is surrounded by muscles and does not directly articulate with the ribs, allowing it to move freely across the back of the thoracic cage.
The scapula plays a key role in anchoring the upper limb and serving as a site for numerous muscle attachments.
The scapula has three borders (superior, medial, and lateral) and three angles (superior, inferior, and lateral).
The lateral angle contains the glenoid cavity, a shallow socket that articulates with the head of the humerus to form the glenohumeral joint. Just above and below this cavity are the supraglenoid and infraglenoid tubercles, which serve as attachment points for arm muscles.
On its posterior surface, the scapula features a prominent ridge called the spine, which divides the bone into two fossae: the supraspinous fossa above and the infraspinous fossa below. These fossae provide attachment areas for muscles that move the shoulder.
The spine extends laterally to form the acromion, which creates the bony tip of the shoulder and articulates with the clavicle.
Another important projection is the coracoid process, a hook-like structure on the anterior side that serves as an attachment point for ligaments and muscles of the chest and arm.
The anterior surface of the scapula contains the subscapular fossa, a broad depression that also provides space for muscle attachment.
Altogether, the scapula has three fossae:
supraspinous fossa
infraspinous fossa
subscapular fossa
all of which are important for muscle function and shoulder movement.
The clavicle and scapula move together as a functional unit, allowing the shoulder to perform complex motions such as lifting, rotating, and extending the arm.
The acromioclavicular joint connects the clavicle to the scapula and is supported by ligaments, especially the strong coracoclavicular ligament. Injuries to this joint, such as ligament tears, can result in a condition known as a “shoulder separation,” often seen in contact sports.
Need a recap? Take a look at the shoulder girdle anatomy notes here.
Need a recap? Take a look at the shoulder girdle anatomy notes here.
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References
References
Gray, H. (1918). Anatomy of the human body (W. H. Lewis, Ed.; 20th ed.). Lea & Febiger.
J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix. (2013, April 25). Anatomy and Physiology. OpenStax. https://openstax.org/books/anatomy-and-physiology/pages/8-1-the-pectoral-girdle.
Based on OpenStax, Anatomy and Physiology (2013), licensed under CC BY 4.0.
Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.
Content paraphrased; adaptations were made.
Sobotta, J. (1914). Atlas and text-book of human anatomy (J. P. McMurrich, Ed.; W. H. Thomas, Trans.). W.B. Saunders Company.
Image Credis
Image Credis
Images used in this guide and games are from the following source:
Sobotta, J. (1914). Atlas and text-book of human anatomy (J. P. McMurrich, Ed.; W. H. Thomas, Trans.). W.B. Saunders Company.
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