Logan Steele
The clavicle, or collarbone, is an S-shaped bone that connects the arm to the body. It is the most commonly fractured bone, often caused by a fall or blow to the shoulder. The clavicle plays an important role in functional movement, connecting the axial skeleton to the pectoral girdle, and acting as a brace for the shoulder. There are five muscles attached to the clavicle, including the deltoid, trapezius, sternocleidomastoid, pectoralis major, and subclavius muscles. These muscles provide dynamic stability to the acromioclavicular joint and enable a variety of arm movements.
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What You'll Learn
- The trapezius muscle attaches to the posterior surface of the lateral third of the clavicle
- The deltoid muscle attaches to the anterior surface of the lateral third of the clavicle
- The sternocleidomastoid muscle attaches to the medial third of the clavicle
- The pectoralis major muscle attaches to the anterior surface of the medial third of the clavicle
- The subclavius muscle attaches to the subclavian groove of the clavicle
The trapezius muscle attaches to the posterior surface of the lateral third of the clavicle
The clavicle, or collarbone, is an S-shaped bone that serves as a strut between the shoulder blade and the sternum (breastbone). It is the only long bone in the body that lies horizontally. The clavicle plays an essential role in functional movement, serving as the connection between the axial skeleton and the pectoral girdle. This allows the clavicle to act as a brace for the shoulder, transferring weight from the upper limbs to the axial skeleton.
The trapezius muscle is a large, triangular, broad, and thin superficial back muscle that resembles a trapezoid. It is one of the commonly affected muscles in facioscapulohumeral muscular dystrophy (FSHD). The trapezius is also one of the broadest and most superficial (closest to the skin) muscles of the upper back and trunk. It is often used as a landmark when dissecting a cadaver. The trapezius has upper, middle, and lower groups of fibres. The upper fibres can elevate and upwardly rotate the scapula and extend the neck. The middle fibres adduct (medially retract) the scapula, while the lower fibres depress and aid the upper fibres in upwardly rotating the scapula.
The trapezius muscle has several origin points along the midline of the posterior neck and back. The superior fibres attach to the medial third of the superior nuchal line, the external occipital protuberance of the occipital bone, and the nuchal ligament. These fibres have a descending course towards their insertion point. The middle fibres originate from the spinous processes of T1-T4 vertebrae and their intervening supraspinous ligaments. These fibres are directed horizontally, running laterally towards the shoulder. The inferior fibres originate from the spinous processes of the T4-T12 vertebrae and their respective supraspinous ligaments.
The trapezius muscle is attached to the posterior surface of the lateral third of the clavicle. The superior fibres of the trapezius converge laterally on the superior angle of the scapula to attach to their respective insertion points. The superior fibres insert on the posterior border of the lateral third of the clavicle. The trapezius muscle is the only muscle of the upper limb that does not receive its innervation from the brachial plexus. Instead, motor innervation is conveyed by the accessory nerve (CN XI) and the anterior rami of the C3 and C4 spinal nerves.
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The deltoid muscle attaches to the anterior surface of the lateral third of the clavicle
The clavicle, or collarbone, is a long, slender, S-shaped bone that serves as a strut between the shoulder blade and the sternum (breastbone). It is the only long bone in the body that lies horizontally. The clavicle plays an essential 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.
The deltoid muscle is a thick, triangular shoulder muscle that gets its name from its shape, which resembles the Greek letter delta (Δ). It is a skeletal muscle, meaning it is a voluntary muscle that can be moved by choice. The deltoid muscle has three functionally and anatomically distinct parts: the clavicular (anterior), acromial (middle), and scapular spinal (posterior). The clavicular part of the deltoid muscle attaches to the anterior surface of the lateral third of the clavicle. This anterior deltoid helps move the arm forward, and you use it when reaching for an object on a shelf.
The deltoid muscle is one of five muscles attached to the clavicle, with two attaching to the lateral third of the bone and three attaching to the medial third. The other muscle attached to the lateral third of the clavicle is the trapezius muscle, which attaches along the posterior surface of the lateral third of the bone. The three muscles attached to the medial third of the clavicle are the sternocleidomastoid muscle, the pectoralis major muscle, and the subclavius muscle.
The deltoid muscle is superficial, meaning it is close to the skin's surface. It is also broad at its origin and narrow at its base. The muscle fibres run inferiorly towards the humeral shaft and converge into a strong tendon that inserts into the deltoid tuberosity on the lateral aspect of the shaft of the humerus. The deltoid muscle helps to move the arm forward, backward, and to the side. It works alongside other shoulder muscles, such as the rotator cuff muscles, to enable a variety of movements.
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The sternocleidomastoid muscle attaches to the medial third of the clavicle
The clavicle, or collarbone, is a slender, S-shaped long bone that serves as a strut between the shoulder blade and the sternum. It plays an essential 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 is the most commonly fractured bone, often caused by falls or direct hits to the shoulder.
The sternocleidomastoid muscle is a large, two-headed neck muscle that originates from two locations: the manubrium of the sternum and the clavicle. It has two heads, the sternal head, and the clavicular head, which attach to the medial third of the clavicle. The clavicular head is composed of fleshy and aponeurotic fibres that arise from the upper frontal surface of the medial third of the clavicle and direct vertically upward. The two heads are separated at their origins by a triangular interval but blend into a thick, rounded muscle below the middle of the neck.
The sternocleidomastoid muscle travels obliquely across the side of the neck and inserts at the mastoid process of the temporal bone of the skull. This muscle is easily visible and palpable, and its contraction can lead to a condition called torticollis or wry neck. It plays a crucial role in rotating the head to the opposite side and flexing the neck. When both sides of the muscle act together, they flex the neck and extend the head.
The sternocleidomastoid muscle is also an accessory muscle of respiration, working alongside the scalene muscles of the neck. It protects vital neurovascular structures in the neck and aids in the formation of the triangles of the neck. Additionally, it serves as a landmark for central venous catheterization and other surgical procedures.
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The pectoralis major muscle attaches to the anterior surface of the medial third of the clavicle
The clavicle, or collarbone, is a long, slender, S-shaped bone that serves as a strut between the shoulder blade and the sternum. It is the only long bone in the body that lies horizontally. The clavicle plays an essential role in functional movement, acting as a brace for the shoulder and allowing weight transfer from the upper limbs to the axial skeleton.
The pectoralis major is a fan-shaped muscle that consists of three parts that originate from three different sites. The clavicular part, also known as the clavicular head, originates from the anterior surface of the medial third of the clavicle. The other two parts are the sternocostal part and the abdominal part. The pectoralis major is the most superficial muscle in the pectoral region.
The pectoralis major muscle is a broad, paired, superficial muscle located on the anterior surface of the thoracic cage. It is a large muscle and is the most superficial muscle in the chest area. In males, it is covered by the deep layer of fascia, subcutaneous tissue, and the adjacent skin. In females, it is covered by the breast.
The pectoralis major has four actions that are primarily responsible for the movement of the shoulder joint. Firstly, it flexes the humerus, as in throwing a ball underhand or lifting a child. Secondly, it adducts the humerus, as when flapping the arms. Thirdly, it rotates the humerus medially, as occurs when arm-wrestling. Finally, acting together with the latissimus dorsi muscle, the pectoralis major pulls the trunk forwards or upwards when its humeral attachment is fixed. This action is important in activities such as climbing.
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The subclavius muscle attaches to the subclavian groove of the clavicle
The clavicle, or collarbone, is a long, slender, S-shaped bone that serves as a strut between the shoulder blade and the sternum. It is the only long bone in the body that lies horizontally. The clavicle plays an essential role in functional movement, serving as the connection between the axial skeleton and the pectoral girdle, allowing the clavicle to act as a brace for the shoulder.
The subclavius muscle is a small, triangular muscle in the anterior thorax located between the clavicle and the first rib. It originates from the upper border of the first rib and its cartilage. The subclavius muscle attaches to the subclavian groove of the clavicle, specifically to the inferior surface of the middle third of the clavicle.
The subclavius is enveloped in the clavipectoral fascia along with the pectoralis minor, coracobrachialis, and short head of the biceps. The pectoralis major muscle courses superficially to the subclavius and clavipectoral fascia. The subclavius muscle is innervated by the subclavian nerve, a branch of the brachial plexus.
The subclavius muscle is important in preventing injury to the adjacent subclavian blood vessels and the superior trunk of the brachial plexus in the event of a fractured clavicle. It also helps to stabilize the sternoclavicular joint and draws the clavicle downwards and forward. Additionally, the subclavius may work synergistically with other muscles during downward rotation of the scapula via depression of the clavicle.
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Frequently asked questions
There are five muscles attached to the clavicle, distributed at either the lateral third or medial two-thirds of the bone.
The trapezius muscle and the deltoid muscle.
The sternocleidomastoid muscle, the pectoralis major muscle, and the subclavius muscle.
The clavicle is a slender, S-shaped long bone that serves as a strut between the shoulder blade and the sternum (breastbone).
The clavicle acts as a brace for the shoulder, allowing weight to be transferred from the upper limbs to the axial skeleton.
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