Logan Steele
The subclavius muscle is a small, triangular muscle in the pectoral region of the thorax. It is a stabiliser of the clavicle during movements of the shoulder and arm, and also helps to prevent injury to the brachial plexus and subclavian vessels in the event of a clavicular fracture. The subclavius muscle is innervated by the subclavian nerve (C5-6), and receives arterial blood from the clavicular branch of the thoracoacromial artery and the suprascapular artery.
| Characteristics | Values |
|---|---|
| Shape | Short and triangular |
| Location | Thoracic wall, underneath the clavicle |
| Origin | First rib |
| Insertion | Undersurface of the middle third of the clavicle |
| Function | Stabilize the clavicle during movements of the shoulder girdle, prevent dislocation of the clavicle at the sternoclavicular joint, protect neurovascular structures in the event of a clavicular fracture, control the position of the scapula in relation to the thorax |
| Innervation | Subclavian nerve (C5-6), a branch of the brachial plexus |
| Blood Supply | Clavicular branch of the thoracoacromial artery, with contributions from the suprascapular artery |
| Envelopment | Clavipectoral fascia, along with the pectoralis minor, coracobrachialis, and short head of the biceps |
| Overlying Muscle | Pectoralis major |
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What You'll Learn
Subclavius muscle's origin and insertion
The subclavius muscle is pronounced as ["sʌb'kleɪvɪəs"].
Subclavius Muscles Origin and Insertion:
The subclavius muscle is a small, triangular muscle in the anterior thorax, located between the clavicle and the first rib. It plays a crucial role in stabilizing the clavicle and preventing injuries to the surrounding structures.
The subclavius muscle originates from the first rib and its adjacent first costal cartilage. Specifically, it arises from the sternal or upper border of the first rib, near its articulation with the costal cartilage. From its origin, the muscle fibres travel superolaterally, forming a muscle belly that inserts into the clavicle.
The insertion point of the subclavius muscle is on the inferior surface or undersurface of the middle third of the clavicle. This area is also known as the groove for the subclavius muscle. The muscle attaches to the clavicle via a broad tendon, which allows for the movement and stabilization of the clavicle.
In some individuals, the subclavius muscle may also have an additional insertion point at the coracoid process of the scapula. However, this variation is not present in all people.
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. This fascia helps to support and stabilize the subclavius muscle as it functions to stabilize the clavicle and protect the underlying neurovascular structures.
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Its nerve supply
The subclavius muscle is innervated by the nerve to the subclavius, also known as the subclavian nerve (C5-6). This nerve is a small branch that arises from the superior trunk of the brachial plexus. The brachial plexus is a network of nerves that supply the arm and shoulder. It is formed by the anterior rami of the lower four cervical nerves and the first thoracic nerve.
The subclavian nerve provides motor and sensory innervation to the subclavius muscle. It supplies the muscle with nerve fibres that control its contraction and relaxation, allowing it to perform its function of stabilizing the clavicle during movements of the shoulder and arm. The nerve also carries sensory information from the muscle to the central nervous system, providing feedback on position, movement, and any pain or discomfort.
In addition to the nerve supply, the subclavius muscle also has a blood supply that is important for its function. It receives arterial blood from the clavicular branch of the thoracoacromial artery, with additional contributions from the suprascapular artery. This blood supply provides the oxygen and nutrients necessary for the muscle to function and recover from fatigue.
The subclavius muscle plays a crucial role in preventing injuries to the adjacent neurovascular structures, such as the brachial plexus and subclavian vessels, in the event of a fractured clavicle. By stabilizing the clavicle and protecting these underlying structures, the subclavius muscle helps to prevent dislocation of the clavicle at the sternoclavicular joint. However, it is important to note that the subclavius muscle itself can also be susceptible to injury or strain, leading to pain along the clavicle, sternoclavicular joint, shoulder, or even radiating into the arm.
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Blood supply to the subclavius muscle
The subclavius muscle (pronounced: sub-CLAY-vee-us) is a short, triangular muscle of the thoracic wall, located underneath the clavicle. Its primary function is to stabilise the clavicle during movements of the shoulder and arm, while also preventing dislocation of the clavicle at the sternoclavicular joint. Additionally, the subclavius muscle plays a protective role for the underlying neurovascular structures, such as the brachial plexus and subclavian vessels, in the event of a clavicular fracture.
The blood supply to the subclavius muscle is primarily through the clavicular branch of the thoracoacromial artery, with additional contributions from the suprascapular artery. The subclavius muscle receives arterial blood from these sources, ensuring adequate oxygen and nutrient delivery for its functions.
The thoracoacromial artery is a vital blood vessel that arises from the second part of the axillary artery, which itself is a continuation of the subclavian artery. The thoracoacromial artery provides oxygenated blood to the muscles and tissues of the chest, shoulder, and upper arm. It has four main branches: the acromial, deltoid, pectoral, and clavicular branches. The clavicular branch, as its name suggests, supplies blood to the clavicle and the surrounding area, including the subclavius muscle.
The suprascapular artery, another contributor to the blood supply of the subclavius muscle, arises from the third part of the axillary artery. It passes through the quadrangular space, formed by the teres minor and triceps muscles, along with the axillary nerve. The suprascapular artery provides blood flow to the supraspinatus and infraspinatus muscles of the shoulder, as well as the surrounding structures, including the subclavius muscle.
An understanding of the blood supply to the subclavius muscle is essential for comprehending its functions and physiological interactions with adjacent structures. By receiving arterial blood from the clavicular branch of the thoracoacromial artery and the suprascapular artery, the subclavius muscle maintains its activity and contributes to the overall stability and protection of the clavicle and surrounding neurovascular structures.
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Subclavius muscle's function
The subclavius muscle is a small, triangular muscle located in the pectoral region of the anterior chest wall, just beneath the clavicle. Its name, cleverly reflecting its precise location, comes from the Latin "sub", meaning "under", and "clavius", referring to the clavicle or collarbone.
The subclavius originates at the junction of the first rib and its costal cartilage and inserts onto the middle third of the clavicle. This muscle is one of the three "pivotal muscles" of the shoulder girdle, along with the pectoralis minor and teres minor. Its primary function is to actively stabilise the clavicle at the sternoclavicular joint during movements of the shoulder and arm. When the lateral end of the clavicle is depressed, the subclavius assists the pectoralis minor and rhomboideus major in a downward rotation for the glenoid cavity in the scapula, helping to brace the clavicle into position against the sternum.
Additionally, the subclavius plays a protective role by preventing injuries to the adjacent neurovascular structures, such as the subclavian vessels and the superior trunk of the brachial plexus, in the event of a clavicle fracture. This protective function is particularly important given that the collarbone is the most commonly broken long bone in the human body.
Problems with the subclavius muscle can occur if the collarbone has been dislocated or broken, and various activities can cause pain in the muscle, including lifting heavy objects and working with arms outstretched.
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Clinical correlations of the subclavius muscle
The subclavius muscle is a short, triangular muscle of the thoracic wall that lies underneath the clavicle. Its main function is to stabilise the clavicle during movements of the shoulder girdle and arm. It also plays a role in preventing injuries to the adjacent neurovascular structures in the event of clavicle fractures.
The subclavius muscle has been clinically correlated with various conditions and procedures. One notable correlation is with venous cannulation below the clavicle. The anatomical relationship between the subclavius muscle and the subclavian vein is important in this context. Studies have found that the subclavius muscle and subclavian vein are closely adherent in a significant proportion of specimens, with some reports of catheter entrapment by the subclavius muscle. This information is relevant for clinical procedures to prevent complications such as the "catheter pinch-off syndrome". Ultrasound guidance has been recommended for central venipuncture to avoid penetration of the subclavius muscle.
Another clinical correlation of the subclavius muscle is its association with thoracic outlet syndrome (TOS). TOS is a condition characterised by compression or irritation of the brachial plexus, which consists of nerves and vessels passing deep to the subclavius muscle. The subclavius posticus muscle, a variant of the subclavius muscle, has been implicated in causing brachial plexus compression, leading to neurogenic thoracic outlet syndrome. This syndrome can also have vascular implications. Additionally, the absence of the subclavius muscle has been linked to unilateral thoracic outlet syndrome.
Furthermore, the subclavius muscle has been mentioned in relation to shoulder pain and shoulder joint instability. In a case report, a 56-year-old man presented with pain in his right anterior shoulder, arm, and hand. MRI studies revealed the absence of the subclavius muscle, which is an exceedingly rare anatomical variation. This correlation highlights the potential role of the subclavius muscle in shoulder joint function and stability.
The subclavius muscle has also been implicated in costoclavicular syndrome, another type of thoracic outlet syndrome. This syndrome is characterised by the entrapment of vessels and nerves between the clavicle and the first rib, within the costoclavicular space. This entrapment can lead to irritations of the brachial plexus and circulatory disorders of the arm. Costoclavicular syndrome can be caused by fractures, thoracic deformities, or other factors.
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Frequently asked questions
Sub-cla-vi-us.
It is a small, triangular muscle in the pectoral region of the thorax.
The subclavius muscle helps to stabilize the clavicle during movements of the shoulder and arm. It also helps to prevent dislocation of the clavicle at the sternoclavicular joint.
The subclavius muscle is located underneath the clavicle, originating from the first rib and inserting on the undersurface of the middle third of the clavicle.
The subclavius muscle helps to protect the underlying neurovascular structures, such as the brachial plexus and subclavian vessels, from potential damage in the event of a clavicle fracture.
