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The clavicle, also known as the collar bone, is a long bone that connects the arm to the trunk. It plays a crucial role in functional movement, acting as a brace for the shoulder and allowing weight transfer from the upper limbs to the axial skeleton. The clavicle has multiple attachment sites for muscles, including the trapezius, deltoid, sternocleidomastoid, pectoralis major, subclavius, and sternohyoid muscles. These muscles have various functions, such as depressing and retracting the scapula, elevating and rotating the shoulder, and providing stability to the shoulder joint. In this text, we will focus on the specific muscle responsible for retracting the clavicle and its associated anatomy and functions.
| Characteristics | Values |
|---|---|
| Clavicle structure | Double curved long bone |
| Clavicle location | Front part of the shoulder |
| Clavicle articulation | Medially with the sternum at the sternoclavicular joint |
| Laterally with the acromion process of the scapula | |
| Clavicle shape | Sigmoid-shaped |
| Clavicle function | Connection between the arm and the trunk |
| Connection between the axial skeleton and the pectoral girdle | |
| Muscles attached to the lateral third of the clavicle | Trapezius muscle |
| Deltoid muscle | |
| Muscles attached to the medial third of the clavicle | Sternocleidomastoid muscle |
| Pectoralis major muscle | |
| Subclavius muscle | |
| Sternohyoid muscle |
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What You'll Learn
- The trapezius muscle is attached to the clavicle's posterior surface
- The deltoid muscle is attached to the clavicle's anterior surface
- The sternocleidomastoid muscle is attached to the superior surface
- The pectoralis major muscle is attached to the anterior surface
- The subclavius muscle is attached to the subclavian groove
The trapezius muscle is attached to the clavicle's posterior surface
The clavicle, or collarbone, is a long, double-curved bone that connects the arm to the trunk. It is the only long bone in the body that lies horizontally. The lateral third of the clavicle serves as an attachment site for the trapezius muscle.
The trapezius muscle is a large, triangular, paired muscle located on the posterior aspect of the neck and thorax. It is one of the broadest and most superficial muscles of the upper back and trunk. The muscle is comprised of particularly long muscle fibres spanning a large width of the upper back. The trapezius muscle has several origin points along the midline of the posterior neck and back. Its attachment points include the spinous process of C7-T12 of the spine, ligamentum nuchae, scapulae, clavicles, and ribs.
The trapezius muscle is the only muscle of the upper limb that does not receive its innervation from the brachial plexus. Instead, motor innervation to the trapezius is conveyed by the accessory nerve (CN XI) as well as the anterior rami of the C3 and C4 spinal nerves, which also contain proprioceptive/sensory fibres from the muscle. The trapezius muscle has three sections: upper, middle, and lower. The upper fibres can elevate and upwardly rotate the scapula and extend the neck. The middle fibres adduct (medially retract) the scapula. The lower fibres depress and aid the upper fibres in upwardly rotating the scapula.
The trapezius muscle is attached to the posterior surface of the lateral third of the clavicle. The superior fibres of the trapezius insert on the posterior border of the lateral third of the clavicle. The trapezoid ligament is larger and roughly quadrilateral in shape, inserting onto the distal clavicle along the trapezoidal line/ridge. The trapezoid ligament restrains posterior clavicular displacement and AC compression.
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The deltoid muscle is attached to the clavicle's anterior surface
The clavicle, or collarbone, is a double-curved long bone that connects the arm to the trunk. It is the only long bone in the body that lies horizontally. The lateral end of the clavicle is flat and articulates with the shoulder to form the acromioclavicular joint. The medial end is quadrangular and articulates with the clavicular notch of the manubrium of the sternum to form the sternoclavicular joint.
The deltoid muscle is a thick, triangular shoulder muscle that gets its name from its resemblance to the Greek letter delta (Δ). It has a broad origin and a narrow base. The deltoid has three functionally and anatomically distinct parts: the clavicular (anterior) part, the acromial (middle) part, and the scapular spinal (posterior) part. The clavicular part originates from the superior surface and the anterior border of the lateral third of the clavicle. This part of the deltoid assists in flexion of the shoulder and internal rotation of the arm. The anterior deltoids are the front delts that help move the arm forward, such as when reaching for an object on a shelf.
The acromial part arises from the lateral margin and superior surface of the acromion of the scapula. This part of the deltoid abducts the arm. The scapular spinal part originates from the lateral 1/3 of the spine of the scapula, on the crest. This part of the deltoid extends and externally rotates the arm. The posterior deltoids are the rear delts that help move the arm backward, such as when pitching a baseball.
The deltoid muscle plays a crucial role in the stabilization of the glenohumeral joint. It produces a line of force during static contraction, preventing inferior displacement of the joint when carrying heavy objects with the arm fully adducted. The deltoid also undergoes eccentric contraction when the arm is lowered or adducted, allowing for controlled adduction.
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The sternocleidomastoid muscle is attached to the superior surface
The sternocleidomastoid muscle is a two-headed neck muscle that gets its name from its points of attachment: sterno- (sternum), cleido- (clavicle), and -mastoid (mastoid process). The clavicular head of the sternocleidomastoid muscle attaches to the superior surface of the medial third of the clavicle. The clavicle, also known as the collarbone, is a double-curved, sigmoid-shaped long bone that connects the arm to the trunk. It articulates medially with the sternum at the sternoclavicular joint and laterally with the acromion process of the scapula. The medial end of the clavicle is quadrangular and articulates with the clavicular notch of the manubrium of the sternum to form the sternoclavicular joint. The lateral end of the clavicle is flat and articulates with the shoulder to form the acromioclavicular joint.
The sternocleidomastoid muscle originates from two locations: the manubrium of the sternum and the clavicle. It travels obliquely across the side of the neck and inserts at the mastoid process of the temporal bone of the skull. The muscle is thick and narrow at its center, broadening and thinning at either end. The sternal head is tendinous in the front and fleshy behind, arising from the upper part of the front of the manubrium sterni. It travels superiorly, laterally, and posteriorly. The clavicular head is composed of fleshy and aponeurotic fibers that arise from the upper, frontal surface of the medial third of the clavicle and are directed almost vertically upward.
The two heads of the sternocleidomastoid muscle are separated from one another at their origins by a triangular interval (lesser supraclavicular fossa) but gradually blend below the middle of the neck into a thick, rounded muscle. The triangle formed by the clavicle and the sternal and clavicular heads of the sternocleidomastoid muscle is used as a landmark in identifying the correct location for central venous catheterization. The medial edge of the sternocleidomastoid muscle serves as a lead structure when placing a central venous catheter (CVC).
Contraction of the sternocleidomastoid muscle can result in a condition called torticollis or wry neck, characterized by a tilted head appearance. Treatment for torticollis involves physiotherapy exercises to stretch the involved muscle and strengthen the muscle on the opposite side of the neck. Unilateral contraction of the sternocleidomastoid muscle flexes the cervical vertebral column to the same side (lateral flexion) and rotates the head to the opposite side. Bilateral contraction elevates the head by dorsally extending the upper cervical joints while also flexing the lower cervical column, resulting in an overall bending of the neck towards the chest.
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The pectoralis major muscle is attached to the anterior surface
The clavicle, or collar bone, is a double-curved long bone that connects the arm to the trunk. It is the only long bone in the body that lies horizontally. The medial end of the clavicle articulates with the sternum at the sternoclavicular joint, while the lateral end articulates with the acromion process of the scapula at the acromioclavicular joint. The clavicle plays a crucial role in functional movement, serving as the connection between the axial skeleton and the pectoral girdle, allowing it to act as a brace for the shoulder and facilitating weight transfer from the upper limbs to the axial skeleton.
The pectoralis major muscle is a fan-shaped muscle that consists of three parts: the clavicular part, the sternocostal part, and the abdominal part. The clavicular part of the pectoralis major muscle originates from the anterior surface of the medial half of the clavicle, specifically the medial clavicle anteriorly. This muscle is the most superficial muscle in the pectoral region and is also the largest muscle of the anterior chest wall. It is a paired, superficial muscle located on the anterior surface of the thoracic cage.
The pectoralis major muscle has a broad origin, and its fibers from all three parts run laterally, converging towards the proximal humerus. The distal attachment of both the clavicular and sternocostal heads is onto the intertubercular sulcus of the humerus. The upper and lower fibres of the pectoralis major insert into the crest of the greater tubercle of the humerus. The muscle is innervated by the lateral and medial pectoral nerves, which stem from the brachial plexus.
The pectoralis major muscle plays a crucial role in the movement of the upper limb. It adducts and medially rotates the upper limb, drawing the scapula anteroinferiorly. The clavicular head acts independently to flex the upper limb, while the sternocostal head facilitates the extension of the flexed arm by pulling it downwards. Additionally, the pectoralis major muscle assists in climbing by pulling the trunk forwards or upwards when its humeral attachment is fixed. It also plays a role in forced breathing by facilitating inspiration.
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The subclavius muscle is attached to the subclavian groove
The clavicle, also known as the collar bone, is a double-curved, sigmoid-shaped long bone that connects the arm to the trunk. It plays an essential role in functional movement, serving as a connection between the axial skeleton and the pectoral girdle. The clavicle has five muscles attached to it, two on its lateral third and three on its medial two-thirds.
The subclavius muscle is one of the muscles attached to the medial two-thirds of the clavicle. Specifically, the subclavius muscle is attached to the subclavian groove, which is located on the inferior surface of the middle third of the clavicle. The subclavius muscle originates from the upper border of the first rib and its cartilage, with its tendon inserting into the subclavian groove.
The subclavius muscle is enclosed by the clavipectoral fascia, a fibrous connective tissue that spans the interval between the clavicle and the pectoralis minor muscle. The subclavius is a small, triangular muscle located in the anterior thorax, between the clavicle and the first rib. It functions to depress the shoulder and pull the clavicle anteroinferiorly. Additionally, the subclavius helps to protect the adjacent subclavian blood vessels and the superior trunk of the brachial plexus in the event of a fractured clavicle.
Myofascial pain or muscle strain of the subclavius can result in pain along the clavicle, sternoclavicular joint, shoulder, or even radiating into the arm. This pain can be caused by heavy lifting, chronic forward shoulder positioning, using a heavy backpack or strap across the clavicle, or sleeping on one's side with the upper extremity positioned overhead.
The subclavius muscle also contributes to controlling the position of the scapula in relation to the thorax and may play a role in regulating the output of kinetic energy during the movement of the upper extremity.
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Frequently asked questions
The trapezius, rhomboids, and latissimus dorsi muscles are responsible for retracting the clavicle.
The clavicle, also known as the collar bone, is a long, double-curved bone that connects the arm to the trunk. There are two clavicles in a person, one on the right and one on the left side.
The clavicle acts as a brace for the shoulder, allowing weight transfer from the upper limbs to the axial skeleton. It also protects neurovascular structures entering the thorax.
Six muscles are attached to the clavicle, distributed across its lateral third and medial two-thirds. The trapezius and deltoid muscles are attached to the lateral third, while the medial third includes the sternocleidomastoid, pectoralis major, sternohyoid, and subclavius muscles.
