It is a broad triangular muscle extending along the dorsal midline from the level of atlas to the end of the thoracic region, and covers a part of the shoulder. It consists of cervical (trapezius cervicis) and dorsal(trapezus thoracis) parts.
Origin: Ligamentum nuchae and supraspinous ligament from the level of the atlas to the twelfth dorsal vertebra.
Insertion: The tuberous part of the spine of the scapula and the scapular fascia.
Action: To elevate the shoulder as a whole. The cervical part draws it forwards and the dorsal part backwards.
Blood supply: Deep cervical, dorsal and intercostal arteries.
Nerve supply: Spinal accessory nerve.
Latissimus dorsi
It is a very wide muscle extending on the lateral wall of the thorax from the dorso-lumbar spine to the arm. It has an aponeurotic origin, which is succeeded by a wide muscular portion.
Origin: Lumbodorsal fascia, 11th and 12th ribs and fascia over the intercostal and external oblique muscles.
Insertion: The anterior part in common with the teres major to the medial (teres) tubercle of the humerus; the middle part to the aponeurosis on the deep face of the long head of triceps; the posterior part along with the deep pectoral to the medial tuberosity of the humerus. The tensor fasciae antibrachii originates from the lateral surface of this muscle.
