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The trapezius muscle is a large, triangular, paired muscle located on the posterior aspect of the neck and thorax. It is the most superficial of the extrinsic muscles of the back. The trapezius has several functions, including stabilizing the scapula and controlling it during movements of the shoulder and upper limb. The trapezius is the only muscle of the upper limb that does not receive its innervation from the brachial plexus. So, which nerve innervates the trapezius muscle?
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What You'll Learn
- The trapezius is the only upper-limb muscle not innervated by the brachial plexus
- Instead, it is innervated by the spinal accessory nerve and branches of the cervical plexus
- The trapezius is the most superficial extrinsic back muscle
- It is involved in head and neck movements
- The muscle is also involved in shoulder movements
The trapezius is the only upper-limb muscle not innervated by the brachial plexus
The trapezius muscle is a large, strong, flat, and triangular muscle that extends over the back of the neck and upper thorax. It is the most superficial muscle on the posterior aspect of the neck and thorax and is functionally considered a muscle of the upper limb. The trapezius has many attachment points, extending from the skull and vertebral column to the shoulder girdle.
The arterial supply to the trapezius varies depending on its level. The descending (upper) part of the muscle is supplied by transverse muscular branches arising from the occipital artery, which passes along the deep surface of the muscle. The transverse (middle) part of the muscle is supplied by the superficial cervical artery or by a branch from the transverse cervical artery. The ascending (lower) part is supplied by muscular branches of the dorsal scapular artery, which arises from the subclavian artery.
The main function of the trapezius is stabilizing the scapula in its anatomical place, as well as controlling it during movements of the shoulder and upper limb. The upper fibres of the trapezius elevate the scapula, the middle fibres retract, and the lower fibres depress. The trapezius works in conjunction with several muscles, including the rhomboids, levator scapulae, serratus anterior, deltoid, and latissimus dorsi, to produce coordinated movements, primarily involving the scapula.
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Instead, it is innervated by the spinal accessory nerve and branches of the cervical plexus
The trapezius muscle is a large, triangular, paired muscle located on the posterior aspect of the neck and thorax. It is the most superficial of the extrinsic muscles of the back. The trapezius is the only muscle of the upper limb that does not receive its innervation from the brachial plexus.
The trapezius has many attachment points, extending from the skull and vertebral column to the shoulder girdle. It is involved in movements of the shoulder girdle and is, therefore, functionally considered a muscle of the upper limb rather than of the back. The main function of the trapezius is to stabilise the scapula in its anatomical place and control it during movements of the shoulder and upper limb.
The descending (upper) fibres of the trapezius act with the levator scapulae muscle to produce an elevation of the scapula at the scapulothoracic joint. The transverse (middle) fibres of the trapezius draw the scapula medially, a movement known as scapular retraction. The ascending (lower) fibres of the trapezius pull the scapula downward.
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The trapezius is the most superficial extrinsic back muscle
The trapezius muscle is the most superficial extrinsic back muscle. It is a large, strong muscle that is essential for several functions, including stabilising the scapula and controlling it during movements of the shoulder and upper limb. The trapezius is a flat, triangular muscle that extends over the back of the neck and upper thorax, forming a diamond or trapezoid shape. It is unique among the muscles of the upper limb in that it does not receive its innervation from the brachial plexus. Instead, it is innervated by the accessory nerve (CN XI) and the anterior rami of the C3 and C4 spinal nerves.
The trapezius has several important functions. Firstly, it plays a crucial role in maintaining the position of the scapula, ensuring smooth and efficient shoulder movement. This is achieved through its coordinated action with other muscles such as the serratus anterior, rhomboids, and latissimus dorsi. The upper fibres of the trapezius elevate the scapula, while the lower fibres depress and rotate it. Additionally, the trapezius is involved in active movements of the head and neck, such as side bending and turning the head, and elevating and depressing the shoulders.
The trapezius muscle has a broad attachment site, originating from the skull, nuchal ligament, and the spinous processes of C7-T12. Its fibres attach to the clavicle, acromion, and scapula spine. This extensive attachment site contributes to the muscle's large size and various functions. The arterial supply to the trapezius varies depending on its level, with the descending (upper) part supplied by branches of the occipital artery, the transverse (middle) part by the superficial cervical artery, and the ascending (lower) part by muscular branches of the dorsal scapular artery.
The trapezius muscle is also involved in throwing actions, working alongside the deltoid muscle and rotator cuff muscles. Furthermore, it assists in maintaining posture, enabling the spinal column to remain erect when standing. The trapezius is the only muscle that provides the necessary lift for arm elevation during shoulder abduction, working in conjunction with the supraspinatus muscle. This collaboration ensures smooth and powerful arm elevation.
Overall, the trapezius muscle, as the most superficial extrinsic back muscle, plays a crucial role in stabilisation, movement, and posture. Its unique structure and innervation contribute to its various functions, making it an important component of the human body's musculoskeletal system.
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It is involved in head and neck movements
The trapezius muscle is involved in head and neck movements. The muscle is divided into three parts: descending (superior), ascending (inferior), and middle. The descending fibres produce an ipsilateral lateral flexion of the head and neck by acting on the atlanto-occipital joint and upper cervical vertebrae, respectively. Unilateral contraction may also result in the contralateral rotation of the head at the atlantoaxial joint. Bilateral contraction of the descending part of the trapezius causes an extension of the head and neck. The upper trapezius is frequently involved in neck injuries and has a clear pain referral pattern to the head.
The trapezius muscle also helps in turning the head to either side, elevating and depressing the shoulders, and rotating the arm internally. It works in conjunction with several muscles to produce coordinated movements, primarily involving the scapula. For example, the rhomboids (major and minor) work closely with the trapezius to retract and stabilize the scapula, playing a key role in shoulder movement and posture. The rhomboids also assist in the downward rotation of the scapula, balancing the action of the trapezius during shoulder movements.
The trapezius muscle is also involved in active movements such as side bending and turning the head, elevating and depressing the shoulders, and internally rotating the arm. It is crucial during movements that involve pushing, reaching forward, or pulling down, as it helps maintain scapular stability, allowing the shoulder to move efficiently.
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The muscle is also involved in shoulder movements
The trapezius muscle is involved in several shoulder movements. It is the most superficial muscle on the posterior aspect of the neck and thorax. The muscle is large, strong, and flat, extending over the back of the neck and upper thorax. It is also broad and triangular, forming a diamond or trapezoid shape.
The trapezius muscle is a key player in shoulder movements, particularly in scapular retraction and stabilization. The upper fibres of the trapezius elevate the scapula, while the lower fibres help with its upward rotation. The middle fibres of the trapezius retract the scapula, pulling it medially, and also stabilise it. The trapezius works closely with other muscles, such as the deltoid, to ensure smooth and powerful arm elevation. This collaboration allows for a full range of motion during shoulder abduction.
Additionally, the trapezius muscle is involved in the downward rotation of the scapula, working in conjunction with the latissimus dorsi. This action is crucial for activities like pulling, rowing, or swimming. The muscle also assists in shoulder adduction, extension, and internal rotation, providing stability during arm and shoulder movements.
The trapezius muscle is also active during throwing actions, working alongside the deltoid muscle and the rotator cuff muscles. It is involved in active movements such as side bending and turning the head, elevating and depressing the shoulders, and internally rotating the arm.
The trapezius muscle has many attachment points, extending from the skull and vertebral column to the shoulder girdle. Its broad attachment range enables its involvement in various shoulder movements.
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Frequently asked questions
The trapezius is a large, triangular, paired muscle located on the posterior aspect of the neck and thorax.
The trapezius is involved in movements of the shoulder girdle and is therefore considered a muscle of the upper limb. It is also involved in the movement of the head and neck.
The trapezius has many attachment points, extending from the skull and vertebral column to the shoulder girdle.
The trapezius muscle is the only muscle of the upper limb that does not receive its innervation from the brachial plexus. Instead, it is innervated by the spinal accessory nerve (CN XI) and the anterior rami of the C3 and C4 spinal nerves.
