Maximus Gage
The scapula, or shoulder blade, is a flat, triangular bone that connects the clavicle to the humerus. It is not a muscle, but several muscles attach directly to it, including the deltoid, latissimus dorsi, trapezius, serratus anterior, levator scapulae, rhomboids, and pectoralis minor. These muscles are responsible for the scapula's movement and stabilization, allowing for a wide range of motion in the arm. The scapula has two surfaces, three borders, three angles, and three processes, providing multiple points of attachment for muscles and ligaments.
| Characteristics | Values |
|---|---|
| Description | Thick, flat, triangular bone |
| Location | Thoracic wall |
| Function | Provides attachment for three groups of muscles: intrinsic, extrinsic, and stabilizing and rotating muscles |
| Groups of Muscles | Intrinsic, Extrinsic, Stabilizing and Rotating |
| Intrinsic Muscles | Rotator cuff (SITS muscle) — subscapularis, supraspinatus, infraspinatus, and teres minor |
| Extrinsic Muscles | Biceps, triceps, and deltoid |
| Stabilizing and Rotating Muscles | Trapezius, serratus anterior, levator scapulae, and rhomboid muscles |
| Borders | Superior, lateral, and medial |
| Angles | Lateral, superior, and inferior |
| Processes | Coracoid and acromion |
| Nerves | Dorsal scapular, upper and lower subscapular, and suprascapular nerves |
| Veins | Axillary vein, suprascapular veins, and anastomotic tributaries |
| Lymph Nodes | Axillary and supraclavicular lymph nodes |
| Injury | Winging of the scapula may occur after injury to the long thoracic or spinal accessory nerves |
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What You'll Learn
The scapula is a bone, not a muscle
The scapula, or shoulder blade, is a bone, not a muscle. It is a thin, flat, triangular bone that lies underneath the clavicle on the thoracic wall. The scapula has two surfaces, three borders (superior, lateral, and medial), three angles, and three processes.
The scapula is an important bone as it provides a point of attachment for a number of muscles that make up the arm and shoulder. These muscles can be divided into three groups: intrinsic, extrinsic, and stabilizing and rotating muscles. The intrinsic muscles include the rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, and teres minor), which attach to the surface of the scapula and are responsible for internal and external rotation of the shoulder joint, along with humeral abduction. The extrinsic muscles include the biceps, triceps, and deltoid, which attach to different parts of the scapula and are responsible for several actions of the glenohumeral joint. The third group, which is mainly responsible for stabilization and rotation of the scapula, consists of the trapezius, serratus anterior, levator scapulae, and rhomboid muscles.
The scapula also has several bony projections for the attachment of muscles, ligaments, and other soft-tissue structures. For example, the levator scapulae attaches at the superior angle of the scapula, while the teres major attaches at the inferior angle. The rhomboids major and minor attach to the medial border of the scapula, and the serratus anterior attaches to the medial margin. The subscapularis originates on the anterior surface of the scapula, and the infraspinatus attaches to the posterior surface. The supraspinatus attaches to the superior portion of the posterior side of the scapula.
The scapula plays an important role in the movement of the arm and shoulder. It articulates with the humerus and clavicle, forming the glenohumeral (shoulder) joint and acromioclavicular joint, respectively. The scapulohumeral rhythm refers to the combination of motions of the scapula, clavicle, and humerus to achieve full elevation of the arm, with a 2:1 ratio. This means that for every two degrees of movement at the humerus, the scapula moves one degree. To achieve the full 180 degrees of elevation of the arm, 120 degrees of movement occur at the glenohumeral joint, while 60 degrees of upward rotation occurs at the scapulothoracic joint.
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The scapula has three borders, three angles, and three processes
The scapula, or shoulder blade, is a flat, triangular bone that connects the clavicle to the humerus. It is not a muscle, but it does provide attachment to several groups of muscles. These muscles include the rotator cuff muscles, teres major, subscapularis, teres minor, and infraspinatus. The scapula has three borders, three angles, and three processes.
The three borders of the scapula are the superior, medial, and lateral borders. The superior border is the shortest and thinnest, extending from the superior angle to the base of the coracoid process. The medial border, also known as the vertebral border, is the longest of the three borders and extends from the superior angle to the inferior angle. The lateral border, or axillary border, is the thickest of the three and begins at the lower margin of the glenoid cavity, inclining obliquely downward and backward to the inferior angle.
The three angles of the scapula are the superior, lateral, and inferior angles. The superior angle is formed by the junction of the superior and medial borders. The lateral angle, or glenoid angle, is broad and bears the glenoid cavity, which is directed forward, laterally, and slightly upward. The inferior angle is where the medial and lateral borders meet.
The three processes of the scapula are the coracoid, acromion, and spine. The acromion forms the summit of the shoulder and is a large, somewhat triangular or oblong process that projects laterally and then curves forward and upward to overhang the glenoid cavity. The spine of the scapula is a protruding ridge of bone that separates the posterior surface of the scapula into two divisions: the supraspinous fossa and the infraspinous fossa. The supraspinous fossa is concave, smooth, and broader at its vertebral end, while the infraspinous fossa is much larger and presents a prominent convexity.
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The scapula provides attachment points for many muscles
The scapula, or shoulder blade, is a flat, triangular bone that connects the clavicle to the humerus. It provides attachment points for many muscles, including the intrinsic, extrinsic, and stabilising and rotating muscles.
The intrinsic muscles of the scapula include the rotator cuff muscles: the subscapularis, supraspinatus, infraspinatus, and teres minor. These muscles attach to the surface of the scapula and are responsible for the internal and external rotation of the shoulder joint, as well as humeral abduction. The supraspinatus and infraspinatus muscles are located in the supraspinous and infraspinous fossa, respectively, which are the two parts of the posterior surface of the scapula, divided by the spine of the scapula. The subscapularis, meanwhile, attaches to the anterior surface of the scapula, also known as the subscapular fossa. The teres major, which attaches to the inferior angle of the scapula, is separated from the infraspinatus muscle by a fibrous septum attached to a ridge on the outer part of the back of the scapula.
The extrinsic muscles of the scapula include the biceps, triceps, and deltoid muscles. These muscles attach to the coracoid process and supraglenoid tubercle of the scapula, the infraglenoid tubercle of the scapula, and the spine of the scapula. The long head of the biceps brachii arises from the supraglenoid tubercle, while the long head of the triceps arises from the infraglenoid tubercle. The deltoid arises from the lower border of the crest of the spine and from the lateral border of the acromion.
The third group of muscles attached to the scapula includes the levator scapulae, trapezius, rhomboids, and serratus anterior. These muscles are responsible for rotational movements and stabilization of the scapula. The levator scapulae attaches at the superior angle of the scapula, while the rhomboids major and minor attach to the medial border. The trapezius is inserted into the upper border of the crest of the spine and into the medial border of the acromion. The serratus anterior is inserted along the medial border of the costal surface, with one digitation from the superior angle to the root of the spine, two digitations to the medial border, and five digitations to the inferior angle.
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The scapula is essential for the full range of motion of the arm
The scapula, or shoulder blade, is a flat, triangular bone that connects the clavicle to the humerus. It is an important bone as it provides a point of attachment for several muscles that make up the arm and shoulder. These muscles include the rotator cuff muscles, teres major, subscapularis, teres minor, and infraspinatus. The scapula also articulates with the humerus and clavicle, forming the glenohumeral (shoulder) joint and acromioclavicular joint, respectively.
The scapula's stability is dependent on the surrounding musculature, with several muscles attaching directly to it. These include the levator scapulae, which attaches at the superior angle of the scapula, and the teres major, which attaches at the inferior angle. The rhomboids major and minor attach to the medial border of the scapula, while the serratus anterior attaches to the medial margin. The subscapularis originates on the anterior surface of the scapula, and the infraspinatus attaches to the posterior surface. The supraspinatus attaches to the superior portion of the posterior side of the scapula.
The muscle synergists for upward rotation of the scapula are the upper and lower trapezius and the serratus anterior. The trapezius is a large triangular muscle at the back of the shoulder that helps lift and lower the shoulder. The deltoid muscle, on the other hand, is responsible for moving the arm forward, backward, and to the side. These muscles, along with the scapula's unique structure and attachments, contribute to the full range of motion of the arm.
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The scapula is associated with several clinical conditions
The scapula, or shoulder blade, is a flat, triangular bone located at the back of the trunk. It is surrounded and supported by a complex system of muscles that work together to help with arm movement. The scapula is associated with several clinical conditions, including:
Scapular Dyskinesis
Scapular dyskinesis is a condition characterised by abnormal scapular positioning or motion, which can cause difficulty in moving the arm, especially during overhead activities. It can result in weakness in the affected arm, with fatigue and limited range of motion. Treatment for scapular dyskinesis may include physical therapy, corrective maneuvers, and a maintenance conditioning program to restore normal scapular position and motion.
Winging of the Scapula
Winging of the scapula refers to the scapula protruding posteriorly when a posterior force is applied to the extended upper extremity. It can be caused by injuries to the long thoracic or spinal accessory nerves, or by fascioscapulohumeral dystrophy, affecting several muscles related to the scapula. Treatment may involve strengthening exercises and restoring good posture.
Scapular Dysplasia
Scapular dysplasia describes an abnormal morphology of the scapula, which can be primary or acquired. Primary dysplasia is due to incomplete ossification of the glenoid, leading to bilateral anatomical changes and symptoms such as clicking, instability, or pain.
Nerve Injuries
Injuries to nerves surrounding the scapula, such as the thoracodorsal nerve, can occur during surgical procedures or trauma. These injuries can result in paralysis of the associated muscles, impacting the function of the scapula and shoulder joint.
Joint Instability
The scapula forms the acromioclavicular and glenohumeral joints. Instability in these joints can impact the movement and function of the scapula and shoulder complex. Assessment of joint instability and subsequent treatment, such as physical therapy, can help restore proper scapular function.
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Frequently asked questions
The scapula, or shoulder blade, is a thick, flat, triangular bone that lies on the thoracic wall. It connects the clavicle to the humerus, forming the glenohumeral (shoulder) joint.
No, the scapula is a bone. However, it provides attachment points for several muscles, including the rotator cuff muscles, teres major, subscapularis, teres minor, infraspinatus, biceps, triceps, and deltoid.
The scapula provides a point of attachment for the muscles that make up the arm and shoulder, allowing a wide range of movement and mobility for the upper limb. It also articulates with the humerus and clavicle to form the glenohumeral and acromioclavicular joints, respectively.
The scapula has two surfaces, three borders (superior, lateral, and medial), three angles (lateral, superior, and inferior), and three processes (coracoid, acromion, and spine).
The intrinsic muscles of the scapula, or the rotator cuff muscles, attach directly to its surface. These include the subscapularis, supraspinatus, infraspinatus, and teres minor. The extrinsic muscles, including the biceps, triceps, and deltoid, attach to different parts of the scapula, such as the coracoid process and supraglenoid tubercle.
