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Human Anatomy The Neck The neck is the region of the body that lies between the lower margin of the mandible above and the suprasternal notch and the upper border of the clavicle below. It is strengthened by the cervical part of the vertebral column, which is convex forward and supports the skull. Behind the vertebrae is a mass of extensor muscles and in front is a smaller group of flexor muscles. In the central region of the neck are parts of the respiratory system, namely, the larynx and the trachea, and behind are parts of the alimentary system, the pharynx and the esophagus. At the sides of these structures are the vertically running carotid arteries, internal jugular veins, the vagus nerve, and the deep cervical lymph nodes Skin of the Neck The natural lines of cleavage of the skin are constant and run almost horizontally around the neck. This is important clinically because an incision along a cleavage line will heal as a narrow scar, whereas one that crosses the lines will heal as a wide or heaped-up scar. Cutaneous Nerves The skin overlying the trapezius muscle on the back of the neck and on the back of the scalp as high as the vertex is supplied segmentally by posterior rami of cervical nerves. Superficial Fascia The superficial fascia of the neck forms a thin layer that encloses the platysma muscle. Also embedded in it are the cutaneous nerves ,the superficial veins, and the superficial lymph nodes. Platysma The platysma muscle is a thin muscular sheet embedded in the superficial fascia of the neck. Origin: Deep fascia over pectoralis major and deltoid m. Insertion: Body of mandible and angle of mouth. Nerve supply: cervical branch of Facial nerve. Action: Depresses mandible and angle of mouth. Platysma muscle Sternocleidomastoid muscle Key Neck Muscles Sternocleidomastoid Muscle: When the sternocleidomastoid muscle contracts, it appears as an oblique band crossing the side of the neck from the sternoclavicular joint to the mastoid process of the skull. It divides the neck into anterior and posterior triangles. The muscle is covered superficially by skin, fascia, the platysma muscle, and the external jugular vein. •Origin: Manubrium sterni and medial third of clavicle •Insertion: Mastoid process of temporal bone and occipital bone •Nerve supply: Spinal part of accessory nerve •Action: Two muscles acting together extend head and flex neck; one muscle rotates head to opposite side. Boundaries: superiorly inferiorly anteriorly inferiorly posteriorly anteriorly Contents of the posterior triangle: A) Nerves and Plexuses: 1. Cutaneous branches of the cervical plexus (supraclavicular nerve, lesser occipital nerve, greater auricular nerve and transverse cervical nerve) enter the posterior triangle by piercing the fascia over its floor, and run for some distance between the floor and roof, before piercing the latter to become subcutaneous. 2. Muscular branches arising from the cervical plexus for the levator scapulae and trapezius run deep to the fascia of the floor. 3. The spinal accessory nerve (Cranial Nerve XI) runs downwards and laterally across the triangle lying between the two layers of the fascia forming the roof. 4. The trunks of the brachial plexus are seen in the lower part of the triangle. A number of branches arising from the plexus are related to the triangle. 5. Phrenic nerve (C3,4,5) B) Vessels: Subclavian Artery (Third part) Transverse cervical artery Suprascapular Artery Terminal part of External jugular vein C) Lymph Nodes: Occipital lymph node Supraclavicular lymph node