1. =Trapezius.=—This is a flat, triangular muscle, the base of the
triangle corresponding with the spine. It is divided by an aponeurotic
portion into two divisions:
(=a=) =Trapezius cervicalis.=—_Origin._—The funicular portion of the
ligamentum nuchæ, from the second cervical to the third thoracic
vertebra.
_Insertion._—The spine of the scapula and the fascia of the shoulder and
arm.
(=b=) =Trapezius thoracalis s. dorsalis.=—_Origin._—The supraspinous
ligament, from the third to the tenth thoracic vertebra.
_Insertion._—The tubercle of the spine of the scapula.
_Action._—Acting as a whole, to elevate the shoulder; the cervical
portion draws the scapula forward and upward and the thoracic portion
draws it backward and upward.
_Structure._—The muscle arises by a short, thin aponeurosis, from which
the fibers of the flat fleshy portion converge to the spine of the
scapula and the aponeurosis which separates the two portions. The
cervical fascia joins the ventral edge of the cervical portion to the
mastoido-humeralis, or the two muscles may unite here.
_Relations._—Superficially, the skin and fascia; deeply, the
rhomboideus, latissimus dorsi, supraspinatus, infraspinatus, deltoid,
splenius, serratus magnus, and anterior deep pectoral muscles, and the
cartilage of the scapula.
_Blood-supply._—Deep cervical and intercostal arteries.
_Nerve-supply._—Spinal accessory nerve.