OVERVIEW
BONES OF NECK
Cervical Vertebrae
Hyoid Bone
BLUE BOX: Bones of Neck. Cervical Pain; Injuries of Cervical Vertebral Column; Fracture of Hyoid Bone
FASCIA OF NECK
Cervical Subcutaneous Tissue and Platysma
Deep Cervical Fascia
BLUE BOX: Cervical Fascia. Paralysis of Platysma; Spread of Infections in Neck
SUPERFICIAL STRUCTURES OF NECK: CERVICAL REGIONS
Sternocleidomastoid Region
TABLE 8.1. Cervical Regions/Triangles and Contents
TABLE 8.2. Cutaneous and Superficial Muscles of Neck
Posterior Cervical Region
Lateral Cervical Region
Anterior Cervical Region
TABLE 8.3. Muscles of Anterior Cervical Region (Extrinsic Muscles of Larynx)
Surface Anatomy of Cervical Regions and Triangles of Neck
BLUE BOX: Superficial Structures of Neck: Cervical Regions. Congenital Torticollis; Spasmodic Torticollis; Subclavian Vein Puncture; Right Cardiac Catheterization; Prominence of External Jugular Vein; Severance of External Jugular Vein; Lesions of Spinal Accessory Nerve (CN XI); Severance of Phrenic Nerve, Phrenic Nerve Block, and Phrenic Nerve Crush; Nerve Blocks in Lateral Cervical Region; Injury to Suprascapular Nerve; Ligation of External Carotid Artery; Surgical Dissection of Carotid Triangle; Carotid Occlusion and Endarterectomy; Carotid Pulse; Carotid Sinus Hypersensitivity; Role of Carotid Bodies; Internal Jugular Pulse; Internal Jugular Vein Puncture
DEEP STRUCTURES OF NECK
Prevertebral Muscles
Root of Neck
TABLE 8.4. Prevertebral Muscles
BLUE BOX: Deep Structures of Neck. Cervicothoracic Ganglion Block; Lesion of Cervical Sympathetic Trunk
VISCERA OF NECK
Endocrine Layer of Cervical Viscera
Respiratory Layer of Cervical Viscera
TABLE 8.5. Muscles of Larynx
Alimentary Layer of Cervical Viscera
TABLE 8.6. Muscles of Pharynx
Surface Anatomy of Endocrine and Respiratory Layers of Cervical Viscera
BLUE BOX: Viscera of Neck. Thyroid Ima Artery; Thyroglossal Duct Cysts; Aberrant Thyroid Gland; Accessory Thyroid Glandular Tissue; Pyramidal Lobe of Thyroid Gland; Enlargement of Thyroid Gland; Thyroidectomy; Injury to Recurrent Laryngeal Nerves; Inadvertent Removal of Parathyroid Glands; Fractures of Laryngeal Skeleton; Laryngoscopy; Valsalva Maneuver; Aspiration of Foreign Bodies and Heimlich Maneuver; Tracheostomy; Injury to Laryngeal Nerves; Superior Laryngeal Nerve Block; Cancer of Larynx; Age Changes in Larynx; Foreign Bodies in Laryngopharynx; Sinus Tract from Piriform Fossa; Tonsillectomy; Adenoiditis; Branchial Fistula; Branchial Sinuses and Cysts; Esophageal Injuries; Tracheo-Esophageal Fistula; Esophageal Cancer; Zones of Penetrating Neck Trauma
LYMPHATICS OF NECK
BLUE BOX: Lymphatics in Neck. Radical Neck Dissections
OVERVIEW
The neck is the transitional area between the base of the cranium superiorly and the clavicles inferiorly. The neck joins the head to the trunk and limbs, serving as a major conduit for structures passing between them. In addition, several important organs with unique functions are located here: the larynx and the thyroid and parathyroid glands, for example.
The neck is relatively slender to allow the flexibility necessary to position the head to maximize the efficiency of its sensory organs (mainly the eyeballs but also the ears, mouth, and nose). Thus, many important structures are crowded together in the neck, such as muscles, glands, arteries, veins, nerves, lymphatics, trachea, esophagus, and vertebrae. Consequently, the neck is a well-known region of vulnerability. Further, several vital structures, including the trachea, esophagus, and thyroid gland, lack the bony protection afforded other parts of the systems to which these structures belong.
The main arterial blood flow to the head and neck (the carotid arteries) and the principal venous drainage (the jugular veins) lie anterolaterally in the neck (Fig. 8.1). Carotid/jugular blood vessels are the major structures commonly injured in penetrating wounds of the neck. The brachial plexuses of nerves originate in the neck and pass inferolaterally to enter the axillae and continue into and supply the upper limbs.
FIGURE 8.1. Dissection of anterior neck. The fascia has been removed and the muscles on the left side have been reflected to show the hyoid bone, thyroid gland, and structures related to the carotid sheath: carotid artery, internal jugular vein (IJV), vagus nerve (CN X), and deep cervical lymph nodes.
In the middle of the anterior aspect of the neck is the thyroid cartilage, the largest of the cartilages of the larynx, and the trachea. Lymph from structures in the head and neck drains into cervical lymph nodes.
BONES OF NECK
The skeleton of the neck is formed by the cervical vertebrae, hyoid bone, manubrium of the sternum, and clavicles (Figs. 8.2 and 8.3). These bones are parts of the axial skeleton except the clavicles, which are part of the appendicular skeleton.
FIGURE 8.2. Cervical vertebrae. A. The 3rd–6th vertebrae are “typical” cervical vertebrae; the 1st, 2nd, and 7th are “atypical.” B and C. Illustration and radiograph of articulated cervical vertebrae. D. Typical cervical vertebra demonstrating a rectangular body with articular unci (uncinate processes) on its lateral aspects, a triangular vertebral foramen, a bifid spinous process, and foramina transversaria.
FIGURE 8.3. Bones and cartilages of neck. A. The bony and cartilaginous landmarks of the neck are the vertebrae, mastoid and styloid processes, angles of the mandible, hyoid bone, thyroid cartilage, clavicle, and manubrium of the sternum. B and C. The hyoid bone and its features are demonstrated.
Cervical Vertebrae
Seven cervical vertebrae form the cervical region of the vertebral column, which encloses the spinal cord and meninges. The stacked, centrally placed vertebral bodies support the head, and the intervertebral (IV) articulations—especially the craniovertebral joints at its superior end—provide the flexibility necessary to allow positioning of the head.
The cervical vertebrae, cervical IV joints, and movement of the cervical region of the vertebral column are described with the back (Chapter 4); therefore, only a brief review follows.
The four typical cervical vertebrae (3rd–6th) have the following characteristics (Fig. 8.2A & D):
• The vertebral body is small and longer from side to side than anteroposteriorly; the superior surface is concave, and the inferior surface is convex.
• The vertebral foramen is large and triangular.
• The transverse processes of all cervical vertebrae (typical or atypical) include foramina transversaria for the vertebral vessels (the vertebral veins and, except for vertebra C7, the vertebral arteries).
• The superior facets of the articular processes are directed superoposteriorly, and the inferior facets are directed inferoposteriorly.
• Their spinous processes are short and, in individuals of European heritage, bifid.
There are three atypical cervical vertebrae (C1, C2, and C7) (Fig. 8.2A):
• The C1 vertebra or atlas: a ring-like, kidney-shaped bone lacking a spinous process or body and consisting of two lateral masses connected by anterior and posterior arches. Its concave superior articular facets receive the occipital condyles.
• The C2 vertebra or axis: a peg-like dens (odontoid process) projects superiorly from its body.
• The vertebra prominens (C7): so-named because of its long spinous process, which is not bifid. Its transverse processes are large, but its foramina transversaria are small.
Hyoid Bone
The mobile hyoid bone (or simply, the hyoid), lies in the anterior part of the neck at the level of the C3 vertebra in the angle between the mandible and the thyroid cartilage (Fig. 8.3). The hyoid is suspended by muscles that connect it to the mandible, styloid processes, thyroid cartilage, manubrium of the sternum, and scapulae.
The hyoid is unique among bones for its isolation from the remainder of the skeleton. The U-shaped hyoid derives its name from the Greek word hyoeidçs, meaning “shaped like the letter upsilon,” the 20th letter in the Greek alphabet. The hyoid does not articulate with any other bone. It is suspended from the styloid processes of the temporal bones by the stylohyoid ligaments (Fig. 8.3A) and is firmly bound to the thyroid cartilage. The hyoid consists of a body and greater and lesser horns (L. cornua). Functionally, the hyoid serves as an attachment for anterior neck muscles and a prop to keep the airway open.
The body of the hyoid, its middle part, faces anteriorly and is approximately 2.5 cm wide and 1 cm thick (Fig. 8.3B & C). Its anterior convex surface projects anterosuperiorly; its posterior concave surface projects postero-inferiorly. Each end of its body is united to a greater horn that projects posterosuperiorly and laterally from the body. In young people, the greater horns are united to the body by fibrocartilage. In older people, the horns are usually united by bone. Each lesser horn is a small bony projection from the superior part of the body of the hyoid near its union with the greater horn. It is connected to the body of the hyoid by fibrous tissue and sometimes to the greater horn by a synovial joint. The lesser horn projects superoposteriorly toward the styloid process; it may be partly or completely cartilaginous in some adults.
BONES OF NECK
Cervical Pain
Cervical pain (neck pain) has several causes, including inflamed lymph nodes, muscle strain, and protruding intervertebral (IV) discs. Enlarged cervical lymph nodes may indicate a malignant tumor in the head; however, the primary cancer may be in the thorax or abdomen because the neck connects the head to the trunk (e.g., lung cancer may metastasize through the neck to the cranium). Most chronic cervical pain is caused by bony abnormalities (e.g., cervical osteoarthritis) or by trauma. Cervical pain is usually affected by movement of the head and neck, and it may be exaggerated during coughing or sneezing, for example.
Injuries of Cervical Vertebral Column
Fractures and dislocations of the cervical vertebra may injure the spinal cord and/or the vertebral arteries and sympathetic plexuses passing through the foramina transversaria. See the blue boxes “Dislocation of Cervical Vertebrae” (p. 457), “Fracture and Dislocation of Atlas” (p. 458), and “Fracture and Dislocation of Axis” (p. 459).
Fracture of Hyoid Bone
Fracture of the hyoid (or of the styloid processes of the temporal bone; see Chapter 7), occurs in people who are manually strangled by compression of the throat. This results in depression of the body of the hyoid onto the thyroid cartilage. Inability to elevate the hyoid and move it anteriorly beneath the tongue makes swallowing and maintenance of the separation of the alimentary and respiratory tracts difficult and may result in aspiration pneumonia.
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