Trapezius muscle: • The trapezius muscle is a large, triangular, paired muscle located on the posterior aspect of the neck and thorax. • When viewed together, this pair forms a diamond or trapezoid shape. • The trapezius has many attachment points, extending from the skull and vertebral column to the shoulder girdle. • The trapezius belongs to the superficial layer of the extrinsic muscles of the back, along with latissimus dorsi, rhomboid major and minor, and levator scapulae muscles. • The trapezius is largely involved in movements of the shoulder girdle, and is therefore functionally considered as a muscle of the upper limb rather than of the back.  Diagram:  Origin:  The trapezius muscle has several origin points along the midline of the posterior neck and back.  The superior fibers attach on the superior nuchal line, of the occipital bone. Superior nuchal line of occipital bone:  The middle fibers originate from the spinous processes of T1-T4 vertebrae  The inferior fibers originate from the spinous processes of the T4-T12 vertebrae .  Insertion:  The superior fibers insert on the posterior border of the lateral third of the clavicle.  The middle fibers insert onto the medial margin of the acromion of the scapula, as well as the superior crest of the scapular spine.  The inferior fibers insert via an aponeurosis on a tubercule at the lateral apex of the medial end of the scapular spine.  Structure and relations: According to their attachments, course and location, it is divided into three functional parts. 1. The descending (upper) part, composed of superior fibres 2. The transverse (middle) part, composed of middle fibres 3. The ascending (lower) part, composed of inferior fibres  Along with latissimus dorsi, the trapezius is the most superficial of the superficial extrinsic back muscles.  It overlies the remaining muscles of this group, namely the rhomboids and levator scapulae.  Deep to the trapezius muscle we can also find the serratus posterior superior, which belongs to the intermediate layer of extrinsic muscles of the back.  In addition, the trapezius covers several muscles of the superficial layer of the intrinsic muscle group, such as the splenius capitis, splenius cervicis, spinalis, longissimus and iliocostalis muscles. The upper part of the trapezius also overlies the suboccipital region.  Blood supply: The arterial supply to trapezius varies depending on the level.  The descending (upper) part of the muscle is supplied by branches of occipital artery  The transverse (middle) part of the muscle is supplied by the superficial cervical artery,  The ascending (lower) part is supplied by subclavian artery.  Nerve supply:  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) and the C3 and C4 spinal nerves.

1. Trapezius muscle:
 The trapezius muscle is a large, triangular, paired muscle located on the
posterior aspect of the neck and thorax.
 When viewed together, this pair forms a diamond or trapezoid shape.
 The trapezius has many attachment points, extending from
the skull and vertebral column to the shoulder girdle.
 The trapezius belongs to the superficial layer of the extrinsic muscles of
the back, along with latissimus dorsi, rhomboid major and minor,
and levator scapulae muscles.
 The trapezius is largely involved in movements of the shoulder girdle, and
is therefore functionally considered as a muscle of the upper limb rather
than of the back.
 Diagram:

2.  Origin:
 The trapezius muscle has several origin points along the midline of the
posterior neck and back.
 The superior fibers attach on the superior nuchal line, of the occipital
bone.
Superior nuchal line of occipital bone:
 The middle fibers originate from the spinous processes of T1-T4
vertebrae
 The inferior fibers originate from the spinous processes of the T4-T12
vertebrae .
 Insertion:
 The superior fibers insert on the posterior border of the lateral third of
the clavicle.
 The middle fibers insert onto the medial margin of the acromion of the
scapula, as well as the superior crest of the scapular spine.
 The inferior fibers insert via an aponeurosis on a tubercule at the
lateral apex of the medial end of the scapular spine.

3.  Structure and relations:
According to their attachments, course and location, it is divided into
three functional parts.
1. The descending (upper) part, composed of superior fibres
2. The transverse (middle) part, composed of middle fibres
3. The ascending (lower) part, composed of inferior fibres
 Along with latissimus dorsi, the trapezius is the most superficial of the
superficial extrinsic back muscles.
 It overlies the remaining muscles of this group, namely
the rhomboids and levator scapulae.
 Deep to the trapezius muscle we can also find the serratus posterior
superior, which belongs to the intermediate layer of extrinsic muscles of
the back.
 In addition, the trapezius covers several muscles of the superficial layer of
the intrinsic muscle group, such as the splenius capitis, splenius
cervicis, spinalis, longissimus and iliocostalis muscles. The upper part of
the trapezius also overlies the suboccipital region.

4.  Blood supply: The arterial supply to trapezius varies depending on the
level.
 The descending (upper) part of the muscle is supplied by branches
of occipital artery
 The transverse (middle) part of the muscle is supplied by the
superficial cervical artery,
 The ascending (lower) part is supplied by subclavian artery.
 Nerve supply:
 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) and the C3 and C4 spinal nerves.
 Functions:
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.
Trapezius muscle is active, along with the deltoid muscle and
the rotator cuff muscles (Supraspinatus, Infraspinatus, Teres minor
& Subscapularis)
In addition, the trapezius is also involved in the movements of the head
and neck.
Descending (upper) fibers: produce an elevation of the scapula,
maintain the level of the shoulders and also causes an extension of the
head and neck.
Transverse (middle) fibers: The transverse (middle) fibers act
in retraction of the scapula, by pulling it towards the midline. The
trapezius muscle is also responsible for upward rotation of the scapula,
along with the serratus anterior muscle. This allows us to raise our arm
above our heads beyond the level of the shoulder.
Ascending (lower) fibers: The ascending (lower) fibers are
responsible for depression of the scapula, and thus lowering the

5. shoulder. Together with the descending part, the ascending fibers also
produce a rotation of the scapula.