The trapezius is a flat regular triangular muscle on the back of the neck and the upper thorax.The muscles of two sides lie side by side in the midline and collectively create a diamond shape/ trapezoid shape, therefore the name trapezius.
- The point of inception is at a line that move throughout the medial third of the superior nuchal line at the base of the skull above to the external occipital protuberance
- It afterwards comes down around the posterior free edge of the nuchal ligament, the vertebral spinous processes to the twelfth thoracic vertebra, and the stepping in supraspinal ligaments.
- The line of origin is an upside-down
It emerges from:
- Medial third of the superior nuchal line,
- External occipital protuberance,
- ligamentum nuchae,
- Spine of 7th cervical vertebra, and
- Spines of all thoracic vertebrae
As a constant line that
- Passes throughout the posterior border of the lateral third of the clavicle,
- Over the medial border of the acromion, and
- With the upper edge of the spine of the scapula (omitting the broadened triangular region at the spine’s medial end).
- With the lower edge of the spine of the scapula, ending at the tubercle of the spine, the line of attachment then doubles back over for a short length.
- Seen from above, the line of insertion is a V, directed laterally, on the top of the bony shoulder girdle.
The insertion takes place as follows:
- The superior fibers to be placed on to the posterior border of the lateral third of the clavicle, goes downwards and laterally.
- The middle fibers to be placed on to the medial margin of the acromion and upper lip of the crest of the spine of the scapula continue horizontally.
- The lower fibers to be placed on to the deltoid tubercle at the joint of medial and middle third of the spine of the scapula go on up and laterally.
- The trapezius is a substantial, broad, triangular muscle situated on the back of the chest, the top of the shoulder, and the hack of the neck.
- The upper fibers of the trapezius go on downward and outside The middle fibers pass horizontally outside; and the lower fibers pass up-ward and outside, heading towards the tubercle on the spine of the scapula through a small aponeurosis.
- The muscle differs in density in its different locations.
- The part on the back of the neck is quite thin
- It produces a muscular column on both side of the midline together with the deep semispinahs capitis muscle.
- In between these columns when the neck is upright, the nuchal ligament rests on the midline of the back of the neck, at the bottom of the vertical groove.
- In side view, the back analysis of the neck can be concave, directly, or convex. It ends up being a raised ridge when the head and neck are hexed forward.
It is by:
- spinal part of the accessory nerve (gives motor supply),.
- Ventral rami of C3 and C4 (bring proprioceptive sensations).
- The upper fibers of trapezius elevate the scapula as in shrugging the shoulder together with levator scapulae.
- The middle fibers of trapezius withdraw the scapula as in bracing back the shoulder together with rhomboids.
- The lower fibers of trapezius depress the medial part of the spine of the scapula.
- Acting with serratus anterior, so that the arm can be abducted beyond 90 ° the trapezius turns the scapula forward.
Palpate the trapezius while the shoulder is shrugged against the resistance. Failure to shrug (to increase) the shoulder is suggestive of muscle weak point.