Correctly Label The Anatomical Features Of The Scapula

The scapula, also known as the shoulder blade, is a vital bone connecting the upper arm to the torso. Understanding its complex anatomy is essential for medical professionals, physical therapists, athletes, and anyone interested in human anatomy. This article provides a detailed guide to correctly labeling the anatomical features of the scapula, ensuring accurate identification and comprehension of its structure and function.

Introduction to the Scapula

The scapula is a flat, triangular bone located in the upper back. It plays a crucial role in shoulder movement and stability, serving as an attachment point for numerous muscles, ligaments, and tendons. Its unique shape and various anatomical features enable a wide range of motion in the shoulder joint. To accurately study and understand the function of the scapula, it is important to correctly identify and label its different parts.

Anterior View of the Scapula (Costal Surface)

The anterior view, also known as the costal surface, faces the ribs. Here's a breakdown of the key features:

Subscapular Fossa: This large, concave depression covers most of the anterior surface. It serves as the attachment site for the subscapularis muscle, a major rotator cuff muscle. The fossa is characterized by several oblique ridges that run from the superomedial to the inferolateral aspect, increasing the surface area for muscle attachment.
Superior Border: The uppermost edge of the scapula. It is relatively thin and extends from the superior angle to the base of the coracoid process.
Medial Border (Vertebral Border): The longest border of the scapula, running parallel to the vertebral column. It extends from the superior angle to the inferior angle. Several muscles attach along this border, including the rhomboid minor, rhomboid major, and serratus anterior.
Lateral Border (Axillary Border): This border runs from the inferior angle to the glenoid cavity. It is thicker than the medial border and serves as the attachment site for the teres minor and teres major muscles.
Superior Angle: The junction of the superior and medial borders. It is located at the level of the second rib.
Inferior Angle: The junction of the medial and lateral borders. It moves forward around the thorax when the arm is abducted.
Coracoid Process: A hook-like or beak-like projection arising from the superior border near the glenoid cavity. It projects anteriorly and laterally, providing attachment points for several muscles and ligaments, including the pectoralis minor, coracobrachialis, biceps brachii (short head), and the coracoclavicular ligament.
Glenoid Cavity (Glenoid Fossa): A shallow, pear-shaped depression located on the lateral angle of the scapula. It articulates with the head of the humerus to form the glenohumeral joint (shoulder joint). The glenoid labrum, a fibrocartilaginous ring, deepens the glenoid cavity and enhances joint stability.
Scapular Notch (Suprascapular Notch): A small notch located on the superior border, just medial to the coracoid process. The suprascapular nerve passes through this notch (or sometimes beneath the superior transverse scapular ligament that bridges the notch), while the suprascapular artery passes above the ligament.

Posterior View of the Scapula (Dorsal Surface)

The posterior view, or dorsal surface, is characterized by the spine of the scapula, which divides the surface into two fossae. Key features include:

Spine of the Scapula: A prominent ridge of bone that runs across the posterior surface of the scapula. It begins medially as a smooth triangular area and becomes progressively more elevated as it extends laterally, eventually forming the acromion.
Acromion: A flattened, expanded process that forms the highest point of the shoulder. It articulates with the clavicle at the acromioclavicular joint. The acromion provides attachment for portions of the deltoid and trapezius muscles.
Infraspinous Fossa: The larger of the two fossae on the posterior surface, located inferior to the spine of the scapula. It serves as the attachment site for the infraspinatus muscle, one of the rotator cuff muscles.
Supraspinous Fossa: The smaller fossa located superior to the spine of the scapula. It provides attachment for the supraspinatus muscle, another rotator cuff muscle.
Superior Border: As seen from the anterior view, the superior border is the uppermost edge of the scapula.
Medial Border (Vertebral Border): Also visible from the posterior view, this border runs parallel to the vertebral column.
Lateral Border (Axillary Border): The lateral border extends from the glenoid cavity to the inferior angle.
Superior Angle: The junction of the superior and medial borders.
Inferior Angle: The junction of the medial and lateral borders.

Lateral View of the Scapula

The lateral view provides a clear perspective of the glenoid cavity and surrounding structures:

Glenoid Cavity (Glenoid Fossa): The pear-shaped depression that articulates with the head of the humerus. Its orientation is slightly anterior and superior.
Acromion: The lateral extension of the scapular spine, forming the point of the shoulder.
Coracoid Process: Projects anteriorly and laterally from the superior border.
Supraglenoid Tubercle: A small eminence located just above the glenoid cavity. It serves as the origin of the long head of the biceps brachii muscle.
Infraglenoid Tubercle: A tubercle located just below the glenoid cavity. It is the origin of the long head of the triceps brachii muscle.
Neck of the Scapula: The constricted region connecting the head of the scapula (including the glenoid cavity) to the body of the scapula.

Borders and Angles of the Scapula

The borders and angles of the scapula are crucial reference points for understanding its orientation and muscle attachments.

Borders

Superior Border: Thin and sharp, extending from the superior angle to the base of the coracoid process. The omohyoid muscle attaches near the scapular notch.
Medial Border (Vertebral Border): Long and relatively straight, running parallel to the vertebral column. It serves as the attachment site for the levator scapulae, rhomboid minor, rhomboid major, and serratus anterior muscles.
Lateral Border (Axillary Border): Runs from the inferior angle to the glenoid cavity. The teres minor muscle attaches to its upper portion, and the teres major muscle attaches to its lower portion. A groove near the upper part of the lateral border, the axillary groove, allows the circumflex scapular artery to pass through.

Angles

Superior Angle: Formed by the junction of the superior and medial borders. It is covered by the trapezius muscle.
Inferior Angle: Formed by the junction of the medial and lateral borders. It moves with arm abduction and serves as an attachment site for the latissimus dorsi and teres major muscles.

Processes and Fossae of the Scapula

Processes

Acromion: The lateral extension of the scapular spine, articulating with the clavicle. It serves as an attachment site for the deltoid and trapezius muscles.
Coracoid Process: A hook-like projection that provides attachment for the pectoralis minor, coracobrachialis, and biceps brachii (short head) muscles, as well as the coracoclavicular ligament.
Spine of the Scapula: A prominent ridge dividing the posterior surface into the supraspinous and infraspinous fossae.

Fossae

Subscapular Fossa: A large concave depression on the anterior surface, serving as the attachment site for the subscapularis muscle.
Supraspinous Fossa: Located superior to the spine of the scapula on the posterior surface, providing attachment for the supraspinatus muscle.
Infraspinous Fossa: Located inferior to the spine of the scapula on the posterior surface, providing attachment for the infraspinatus muscle.
Glenoid Cavity (Glenoid Fossa): A shallow, pear-shaped depression that articulates with the head of the humerus.

Muscle Attachments on the Scapula

Understanding the muscle attachments on the scapula is crucial for comprehending shoulder movement and stability. Here is a summary of the primary muscle attachments:

Subscapularis: Attaches to the subscapular fossa on the anterior surface.
Supraspinatus: Attaches to the supraspinous fossa on the posterior surface.
Infraspinatus: Attaches to the infraspinous fossa on the posterior surface.
Teres Minor: Attaches to the upper portion of the lateral border.
Teres Major: Attaches to the lower portion of the lateral border and the inferior angle.
Deltoid: Attaches to the acromion and the spine of the scapula.
Trapezius: Attaches to the spine of the scapula, acromion, and the superior border.
Rhomboid Minor: Attaches to the medial border, near the superior angle.
Rhomboid Major: Attaches to the medial border, inferior to the rhomboid minor.
Levator Scapulae: Attaches to the medial border, from the superior angle to the spine of the scapula.
Serratus Anterior: Attaches to the medial border on the anterior surface.
Pectoralis Minor: Attaches to the coracoid process.
Coracobrachialis: Attaches to the coracoid process.
Biceps Brachii (Short Head): Attaches to the coracoid process.
Triceps Brachii (Long Head): Originates from the infraglenoid tubercle.
Omohyoid: Attaches near the scapular notch.
Latissimus Dorsi: Attaches near the inferior angle.

Clinical Significance

The scapula is involved in numerous clinical conditions. Accurate anatomical knowledge is essential for diagnosis and treatment. Here are a few examples:

Scapular Fractures: Fractures of the scapula are relatively rare but can occur due to high-energy trauma. The spine of the scapula, glenoid cavity, and acromion are common sites of fracture.
Scapular Winging: This condition occurs when the serratus anterior muscle is weak or paralyzed, causing the medial border of the scapula to protrude posteriorly.
Rotator Cuff Tears: The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) attach to the scapula and humerus. Tears of these muscles can cause pain and limited shoulder function.
Impingement Syndrome: Compression of the supraspinatus tendon beneath the acromion can lead to pain and inflammation.
Scapulothoracic Bursitis: Inflammation of the bursa between the scapula and the rib cage can cause pain and clicking sensations with shoulder movement.
Adhesive Capsulitis (Frozen Shoulder): This condition involves inflammation and thickening of the shoulder joint capsule, leading to pain and stiffness. Scapular movement is often affected.

Common Misconceptions

Confusing the Acromion and Coracoid Process: The acromion is the lateral extension of the scapular spine, while the coracoid process is a hook-like projection arising from the superior border.
Misidentifying the Supraspinous and Infraspinous Fossae: The spine of the scapula clearly divides these two fossae. The supraspinous fossa is superior to the spine, while the infraspinous fossa is inferior.
Ignoring the Importance of Muscle Attachments: The scapula serves as a critical attachment site for numerous muscles that control shoulder movement. Understanding these attachments is essential for comprehending shoulder biomechanics.
Overlooking the Significance of the Glenoid Cavity: The glenoid cavity is a crucial component of the shoulder joint. Its shape and orientation significantly impact shoulder stability and range of motion.
Neglecting the Borders and Angles: The borders and angles of the scapula serve as important landmarks for identifying muscle attachments and assessing scapular position.

Practical Tips for Learning Scapular Anatomy

Use Anatomical Models: Physical models provide a three-dimensional representation of the scapula, allowing for hands-on learning.
Study Anatomical Charts and Illustrations: Visual aids can help reinforce your understanding of scapular anatomy.
Use Online Resources: Numerous websites and apps offer interactive tools and quizzes for learning anatomical structures.
Practice Palpation: Palpate the scapula on yourself or a partner to identify key landmarks.
Clinical Observation: Observe scapular movement in patients or athletes to understand its role in functional activities.
Flashcards: Create flashcards with images and labels to test your knowledge of scapular anatomy.
Dissection: If possible, participate in anatomical dissections to gain a firsthand understanding of scapular structure.
Teach Others: Teaching others is a great way to reinforce your own learning.

Conclusion

Accurately labeling the anatomical features of the scapula is essential for anyone studying or working in the fields of medicine, physical therapy, sports science, or human anatomy. This detailed guide has provided a comprehensive overview of the key structures, including the anterior and posterior views, borders, angles, processes, fossae, and muscle attachments. By understanding the complex anatomy of the scapula, professionals and students can better diagnose and treat shoulder conditions, improve athletic performance, and deepen their knowledge of the human body. With consistent study, practice, and the use of appropriate resources, mastering scapular anatomy is an achievable and rewarding endeavor.