A sharp tongue and a dull mind are usually found in the same head.
Proverb
The neck is a region of considerable anatomic and functional complexity situated in a relatively small area. Recent advances in medical imaging have enhanced the ability to differentiate among the structures of the neck (Fig. 5.1).
FIG. 5.1 Coronal CT reformat demonstrating massive cervical lymphadenopathy.
OBJECTIVES
• List the three anatomic sections of the pharynx.
• List and identify the laryngeal cartilages.
• Identify and describe the esophagus and trachea.
• Identify and state the function of the salivary glands.
• Describe the location and function of the thyroid gland.
• List the lymph node regions of the neck.
• Identify the fascial spaces.
• Identify the pharyngeal muscles.
• State the triangles of the neck, and identify the muscles located within them.
• Describe the course of the major vessels located within the neck.
ORGANS
The structures of the neck are attached by connective tissue and muscles. They are located primarily in the anterior and middle portions of the neck and include the pharynx, larynx, esophagus, trachea, salivary glands, thyroid gland, and lymph nodes.
Pharynx
The pharynx is a funnel-shaped fibromuscular tube approximately 12 cm long that acts as an opening for both the respiratory and digestive systems. The pharynx extends from the base of the skull and ends inferiorly as the continuation of the esophagus. The pharynx is divided into three sections: nasopharynx, oropharynx, and laryngopharynx (Figs. 5.2-5.5).
The nasopharynx is the most superior portion of the pharynx. It is an extension of the nasal cavities along with the nasal mucosa. The nasopharynx has a respiratory function; it allows for the passage of air from the nasal cavity to the larynx. Posteriorly, the boundaries of the nasopharynx are the clivus and upper cervical spine. It is bordered inferiorly by the soft palate and the posterior muscular extension of the hard palate, and extends down to the level of the uvula, which is a projection on the posterior edge of the soft palate (Figs. 5.2-5.7). In the roof and posterior wall of the nasopharynx is a collection of lymphoid tissue known as the pharyngeal tonsils, commonly called the adenoids (Figs. 5.2-5.5). Within the lateral wall of the nasopharynx, posterior to the inferior nasal conchae, is the opening of the eustachian tube (auditory tube), which connects the middle ear to the nasopharynx (Fig. 5.2; see also Chapter 2, temporal bone).
The oropharynx is the posterior extension of the oral cavity and extends from the soft palate to the level of the hyoid bone (Figs. 5.2, 5.4, 5.5, 5.8, and 5.9). It is separated from the larynx by the epiglottis. Two additional pairs of lymphoid tissue are found within the oropharynx: the palatine tonsils, which are located on the lateral walls, and the smaller lingual tonsils, which are situated on the base of the tongue (Figs. 5.2, 5.3, 5.5, and 5.9). Collectively, the tonsils initiate specific defense mechanisms of the immune system by protecting against pathogens entering the nasopharynx and oropharynx. At the union of the base of the tongue and the epiglottis are two pouchlike openings called valleculae. The valleculae are common sites for foreign objects to become lodged within the pharynx (Figs. 5.2-5.5 and 5.10-5.12).
The narrow laryngopharynx continues from the oropharynx and lies between the hyoid bone and the entrance to the larynx and esophagus (Figs. 5.2-5.5). It continues as the esophagus at the level of the cricoid cartilage of the larynx. Within the anterior walls of the laryngopharynx, along either side of the larynx, are two depressions or cavities termed the piriform sinuses (recesses). These sinuses divert food away from the entrance of the larynx and into the esophagus (Figs. 5.3 and 5.12-5.17). The laryngopharynx is commonly referred to as the hypopharynx.
Larynx
The larynx is the bony skeleton that surrounds and protects the vocal cords and is commonly called the voice box. It begins at the laryngopharynx, continues to the trachea, and marks the beginning of the respiratory pathway by allowing for the passage of air into the trachea. The larynx consists of an outer skeleton made up of nine cartilages that extend from approximately the third to the sixth cervical vertebrae. These cartilages are connected to one another by ligaments and are moved by numerous muscles. Three of the cartilages are unpaired: the thyroid, epiglottis, and cricoid. The three paired cartilages are the arytenoid, corniculate, and cuneiform (Figs. 5.18-5.21). The largest and most superior is the thyroid cartilage. It consists of a right and left lamina that unite anteriorly to form a shield that protects the vocal cords (Figs. 5.16-5.20, 5.22, and 5.23). The posterior aspect of the lamina has superior and inferior projections termed the superior and inferior horns (cornua), respectively. The anterior union of the lamina forms a vertical projection commonly referred to as the laryngeal prominence (Adam’s apple). Just above the laryngeal prominence is an area where the laminae do not meet, creating the superior thyroid notch. On the posterior aspect of this projection is the attachment for the epiglottis (Fig. 5.18). The leaf-shaped epiglottis differs from the other cartilages in that it is elastic and allows for movement. It is covered with a mucous membrane and projects superiorly and posteriorly behind the tongue. It is attached to the thyroid cartilage via the thyroepiglottic ligament and to the hyoid bone via the hyoepiglottic ligament. During swallowing, the epiglottis folds back over the larynx, preventing the entry of liquids or solid food into the respiratory passageways (Figs. 5.18-5.21, 5.24, and 5.25). The paired arytenoid cartilages are shaped like pyramids and are situated at the posterior aspect of the larynx just on top of the cricoid cartilage (Figs. 5.18, 5.19, 5.26, and 5.27). Articulating with the superior surface of the arytenoid cartilages are the small, elastic, horn-shaped corniculate cartilages (Figs. 5.18 and 5.19). These cartilages are involved in the movement of the vocal cords for the production of sound. The small, curved cuneiform cartilages lie within the folds of tissue termed the aryepiglottic folds that extend between the lateral aspect of the arytenoid cartilage and epiglottis (Figs. 5.3 and 5.30). The cricoid cartilage is a complete ring that forms the base of the larynx. The posterior portion is broader than the anterior portion, and this is where the other laryngeal cartilages rest. The cricoid cartilage marks the junction between the larynx and the trachea and the beginning of the esophagus (Figs. 5.2, 5.12, 5.19-5.21, 5.28, and 5.29).
Resultant swelling of the epiglottis caused by bacterial or viral infections can be very dangerous (acute epiglottitis). This condition can result in direct blockage of the glottis and airway, leading to suffocation and death.
The inner structures of the larynx include the false and true vocal cords and the aryepiglottic folds. The false and true vocal cords consist of two pairs of ligaments that extend from the arytenoid cartilages to the posterior laminal surface of the thyroid cartilage. They are separated by a space termed the laryngeal ventricle (Figs. 5.18, 5.20, and 5.21). The superior pair of ligaments is called the vestibular folds or false vocal cords because they are not directly involved in the production of sound. The inferior pair is the true vocal cords, named accordingly for their involvement in the production of sound (Figs. 5.18, 5.20, 5.21, 5.26, and 5.27). The true vocal cords extend toward the midline in a closed position during phonation. With quiet respiration, the true vocal cords are in a relaxed position, creating an opening between them called the glottis (Figs. 5.26, 5.27, 5.30, and 5.31). The glottis is the part of the larynx most directly involved with voice production. The aryepiglottic folds consist of tissue projecting off the arytenoid cartilages to the inferior margin of the epiglottis. These folds form the lateral margins of the entrance to the larynx. Located lateral to these folds, between the larynx and thyroid cartilage, are two mucosal pouches called the piriform sinuses whose medial borders form the lateral walls of the larynx (Figs. 5.3, 5.12, and 5.14-5.17).
Esophagus and Trachea
The esophagus is a muscular tube that extends down from the laryngopharynx to the cardiac orifice of the stomach (Figs. 5.32-5.34). It begins posterior to the cricoid cartilage and descends through the thoracic cavity between the trachea and anterior longitudinal ligament of the vertebrae (Figs. 5.20 and 5.21). The esophagus then enters the abdominal cavity through an opening in the diaphragm termed the esophageal hiatus to join the stomach (Fig. 5.32). There are two narrowed areas, or sphincters, of the esophagus: esophageal and cardiac. The esophageal sphincter is situated at the entrance of the esophagus and functions to prevent air from entering the esophagus. The inferior or cardiac sphincter prevents reflux from the stomach into the esophagus. The trachea extends from the larynx to the lungs and lies immediately anterior to the esophagus (Figs. 5.2, 5.20, 5.21, and 5.325.34). Considered an elastic tube, the trachea is reinforced by approximately 16-20 C-shaped pieces of cartilage that maintain an open passageway for air. The cartilages are closed posteriorly by elastic connective tissue that allows for the passage of food through the esophagus. The trachea bifurcates into the right and left mainstem bronchi at the carina, at approximately the T5 level.
The tracheostomy is currently one of the most frequently performed procedures and is one of the oldest surgical procedures described, dating back at least 3500 years. It is an operative procedure that creates a surgical airway in the trachea via an incision in the neck and insertion of a tracheostomy tube between the second and third tracheal rings.
Salivary Glands
The salivary glands are exocrine glands that collectively produce and empty saliva into the oral cavity via ducts. More than 750 minor salivary glands are scattered throughout the mouth and throat. They can be found in the mucosa of the oral cavity, palate, paranasal sinuses, pharynx, trachea, and bronchi. They consist of both mucous and serous glands that help with the total production of saliva. Up to a quart of saliva is produced each day to aid in the process of digestion. Saliva also helps protect the teeth from bacteria and moisten food for ease of swallowing.
There are three large paired salivary glands: parotid, submandibular, and sublingual (Fig. 5.35). Each pair of salivary glands has a distinctive cellular organization and produces saliva with slightly different properties. The largest of these are the parotid glands, which are situated in front of the ear, wedged between the ramus of the mandible and the sternocleidomastoid muscle (Figs. 5.36-5.39). The parotid glands extend inferiorly from the level of the external auditory meatus to the angle of the mandible. Their appearance differs from that of the other salivary glands because of the fatty tissue and intraglandular lymph nodes they contain. The parotid duct (Stensen duct) emerges from the anterior edge of the gland. It passes under the zygomatic arch to enter the oral cavity opposite the second upper molar (Figs. 5.36 and 5.37). The submandibular glands border the posterior half of the mandible, extending from the angle of the mandible to the level of the hyoid bone (Figs. 5.40-5.42). The submandibular duct (Wharton duct) opens into the oral cavity on either side of the lingual frenulum immediately posterior to the teeth (Fig. 5.43). The lingual frenulum is a small midline fold of mucous membrane that extends from the floor of the mouth to the undersurface of the tongue. The sublingual glands are the smallest of the salivary glands and lie under the tongue on the floor of the mouth (Figs. 5.43 and 5.44). Numerous (10-20) sublingual ducts (Rivinus ducts) open in a line along the floor of the mouth. Some of these ducts may fuse to form the Bartholin duct, which opens into or adjacent to the submandibular duct (Fig. 5.35).
The mumps virus often targets the salivary glands, most commonly the parotid gland. Infection usually occurs between 5 and 9 years of age. Because of the development of an effective mumps vaccine, the incidence of this disease has been dramatically reduced.
Thyroid Gland
The thyroid gland is an endocrine gland located at the level of the cricoid cartilage. It consists of two lobes that are joined together anteriorly by the isthmus (Figs. 5.45 and 5.46). In the axial plane, the thyroid gland appears as a wedge-shaped structure, hugging both sides of the trachea (Figs. 5.47 and 5.48). The thyroid gland excretes the hormones thyroxine (T4), triiodothyronine (T3), and calcitonin, which affect almost every cell in the body. Thyroxine and triiodothyronine stimulate cell metabolism and are essential for normal body growth. Calcitonin lowers the blood calcium level and promotes bone formation. Also involved with metabolism of calcium and phosphorus are the parathyroid hormones (PTHs), which are produced by the parathyroid glands. The parathyroid glands are located on the posterior surface of the thyroid lobes and are usually four in number (Fig. 5.45).
Thyroid nodules are abnormal growths of thyroid cells that form a lump within the thyroid gland. The majority of these nodules are benign, but they can also be cancerous in a small percentage of cases. The nodules can be solid or filled with fluid and are often discovered incidentally during a physical examination or on computed tomography (CT), magnetic resonance (MR), or ultrasound imaging. Most of the nodules are asymptomatic, but they can cause hyperthyroid or hypothyroid symptoms. A fine-needle aspiration may be used to take a biopsy of the cells in the nodule to determine if the nodule is cancerous. The majority of benign thyroid nodules do not require treatment.
Hypothyroidism is an underproduction of the thyroid hormone. The most common form is an autoimmune disease called Hashimoto's thyroiditis, also known as chronic lymphocytic thyroiditis or autoimmune thyroiditis. In Hashimoto's thyroiditis, the body sees the thyroid gland as foreign and attacks it. Symptoms include fatigue, sensitivity to cold, excess weight gain, poor circulation, dry skin, hair loss, depression, and poor digestion.
Lymph Nodes
The neck has an extensive lymphatic network containing approximately 40% of the body’s total number of lymph nodes. It is estimated that there are 800 lymph nodes located throughout the body, and roughly 300 of these are located in the relatively small area of the head and neck. Lymph nodes are clustered in regions throughout the vessels of the lymphatic system. The lymph vessels carry fluid from the interstitial spaces to the regional lymph nodes, which filter the lymphatic fluid of harmful foreign particles before being emptied into the venous blood supply. In the head and neck, lymph nodes are grouped along the lower border of the jaw, in front of and behind the ears, and deep in the neck along the larger blood vessels (Figs. 5.49 and 5.50). They drain the skin of the scalp and face, tissues of the nasal cavity, oral cavity, pharynx, trachea, upper esophagus, thyroid gland, and salivary glands. The lymph nodes of the neck can be classified or divided into seven levels or regions for ease of identification, both clinically and surgically (Figs. 5.25, 5.42, and 5.49-5.51 and Table 5.1).
FIG. 5.49 Top, Oblique view of lymph nodes in the head and neck. Bottom, Regional classification of lymph nodes of the neck.
TABLE 5.1 Imaging-Based Classification of Neck Lymph Node Levels
|
Node |
Location |
|
Level I Submental and Submandibu lar Nodes Level IA Submental nodes Level IB Submandibular nodes |
Located above the hyoid bone and the body of the mandible and in front of the posterior boundary of the submandibular gland Between the medial margins of the anterior bellies of the digastric muscles Lateral to the level IA nodes and anterior to the back of the submandibular gland |
|
Level II Upper Internal Jugular Nodes |
Upper third of the internal jugular vein Extend from the skull base to the level of the hyoid bone |
|
Level IIA Level IIB |
Located posterior to the submandibular gland and bounded posteriorly by the sternocleidomastoid (SCM) muscle A level II node that lies medial, lateral, anterior, or posterior to the internal jugular vein A level II node that lies posterior to the internal jugular vein and is separated by a fat plane |
|
Level III Midjugular Nodes |
Extend from the carotid bifurcation or hyoid bone inferiorly to the cricoid cartilage Lie anterior to the SCM muscle |
|
Level IV Low Jugular Nodes |
Extend from the bottom of the cricoid to the level of the clavicle Lie lateral to the carotid arteries |
|
Level V Posterior Triangle Nodes |
Bordered anteriorly by the SCM muscle, posteriorly by the trapezius muscle, and inferiorly by the clavicle |
|
Level VA |
Upper level V nodes that extend inferiorly from the skull base to the cricoid cartilage |
|
Level VB |
Lower level V nodes that extend from the bottom of the cricoid cartilage to the clavicle |
|
Level VI Upper Visceral Nodes |
Extend from the hyoid bone to the top of the manubrium Lie between the carotid arteries |
|
Level VII Superior Mediastinal Nodes Supraclavicular nodes Retropharyngeal nodes |
Extend from the top of the manubrium to the brachiocephalic vein, between the carotid arteries Nodes at or caudal to the clavicle and lateral to the carotid artery Nodes behind the pharynx Extend medial to the internal carotid artery from the base of the skull inferiorly to the hyoid bone |
Fascial Spaces
Structures located in the neck can be divided into supra- and infrahyoid structures based on their location in relation to the hyoid bone. The horseshoe-shaped hyoid bone lies in the anterior aspect of the neck superior to the thyroid cartilage and below the mandible; it forms a base for the tongue (Figs. 5.2, 5.11, 5.19, and 5.20). The suprahyoid neck extends from the base of the skull to the hyoid bone, and the infrahyoid neck extends from the hyoid bone to the clavicles. The suprahyoid and infrahyoid regions of the neck are further divided by deep layers of cervical fascia that encase the anatomy of each region, forming compartments or potential spaces called fascial spaces. There are seven suprahyoid spaces, one infrahyoid space, and four spaces that span the length of the neck to include both the supra- and infrahyoid regions, as follows:
SUPRAHYOID NECK
• Parapharyngeal space (PPS)
• Pharyngeal mucosal space (PMS)
• Masticator space (MS)
• Parotid space (PS)
• Carotid space (CS)
• Retropharyngeal space (RPS), including the danger space (DS)
• Perivertebral space (PVS), including the prevertebral and paraspinal spaces
INFRAHYOID NECK
• Visceral space (VS)
SUPRA- and INFRAHYOID NECK
• Carotid space (CS)
• Retropharyngeal space (RPS)
• Perivertebral space (PVS)
• Posterior cervical space (PCS)
Each compartment or space is associated with pathology specific to the anatomic structures contained within it. Knowledge of the anatomy in these compartments improves the ability to predict the spread of pathology throughout the soft tissue structures in the neck and aids in their surgical intervention (Figs. 5.52-5.55).
The fascial spaces can be identified on the sequential images in Figs. 5.53-5.69 and are described in more depth in Table 5.2.
TABLE 5.2 Suprahyoid and Infrahyoid Neck Spaces and Contents
MUSCLES
Numerous muscles are located within the neck. Each muscle can be difficult to identify individually because the margins seem to blend together in cross-sectional images. This section of the text addresses only the largest and most significant muscles of the neck region.
Pharyngeal and Tongue Muscles
The pharyngeal muscles include the circular layer of constrictors and the inner longitudinal layers (Table 5.3).
There are three overlapping constrictor muscles (superior, middle, inferior) that are responsible for constricting the pharynx and inducing peristaltic waves during swallowing. The three inner longitudinal muscles are the stylopharyngeus, palatopharyn- geus, and salpingopharyngeus muscles, all involved with elevating the pharynx and larynx during swallowing and speaking (Figs. 5.71-5.74). The extrinsic muscles of the tongue are responsible for changing the position of the tongue and include the genioglossus, hyoglossus, styloglossus, and palatoglossus muscles (Figs. 5.70-5.76).
TABLE 5.3 Pharyngeal Muscles
Muscles Within the Anterior Triangle
The neck is frequently divided into two areas called the anterior and posterior triangles by the sternocleidomastoid (SCM) muscle. Everything anteromedial to the SCM muscle is considered part of the anterior triangle, and everything posterior to the SCM muscle is considered part of the posterior triangle. The SCM muscle is a broad, straplike muscle that originates on the sternum and clavicle and inserts on the mastoid tip of the temporal bone. It functions to turn the head from side to side and flex the neck (Figs. 5.77 and 5.78) The platysma is the most superficial muscle found in the anterior portion of the neck. It arises from the fascia and skin overlying the pectoralis major and deltoid muscles and extends superiorly as a thin, broad muscle to the inferior portion of the mandible. It is considered a chief muscle for facial expression (Figs. 5.62, 5.63, and 5.80).
Other muscles of the anterior triangle are referred to as the muscles of the throat and can be divided into the suprahyoid and infrahyoid muscle groups (Figs. 5.77 and 5.78). These muscle groups are named according to their location in relation to the hyoid bone. The suprahyoid and infrahyoid muscles aid in the movement of the hyoid bone and larynx. The suprahyoid muscles (digastric, mylohyoid, stylohyoid, geniohyoid) connect the hyoid bone to the temporal bone and mandible and elevate the hyoid and floor of the mouth and tongue during swallowing and speaking (Figs. 5.70, 5.75, 5.76, and 5.78). The infrahyoid muscles (thyrohyoid, sternohyoid, sternothyroid, omohyoid) are often called strap muscles because of their ribbon-like appearance (Fig. 5.78). They act primarily to depress the hyoid bone and extend inferiorly to insert on the sternum, thyroid cartilage, and scapula (Table 5.4; see sequential images in Figs. 5.52-5.69).
TABLE 5.4 Neck Muscles
|
|
Origin |
Insertion |
Action |
|
Front of Neck—Anterior Triangle |
|||
|
Platysma |
• Fascia and skin over pectoralis major and deltoid muscles |
• Base of mandible and skin of lower face |
• Changes facial expression |
|
Sternocleidomastoid (SCM) |
|||
|
Sternal head Clavicular head |
• Upper manubrium • Sternal end of clavicle |
• Mastoid process, lateral half of superior nuchal line |
• Flexes head and neck |
|
Infrahyoid Muscles Thyrohyoid Sternohyoid Sternothyroid Omohyoid |
• Thyroid cartilage • Superior border of manubrium and medial clavicle • Manubrium and medial end first costal cartilage • Superior border of scapula |
• Inferolateral border hyoid bone • Hyoid bone • Thyroid cartilage • Inferolateral border hyoid bone |
• Lower hyoid bone, raise larynx • Lower hyoid bone • Lower larynx • Lower hyoid bone and larynx |
|
Suprahyoid Muscles |
|||
|
Digastric
Mylohyoid Stylohyoid Geniohyoid |
• Posterior belly—mastoid notch of temporal bone; anterior belly—lower border of mandible • Body of mandible • Styloid process of temporal bone • Mandibular symphysis |
• Ends as intermediate tendon between the two bellies that attach to the hyoid bone • Mandibular symphysis and hyoid bone • Superior surface of hyoid bone • Body of hyoid bone |
• Jaw opener (speech muscle) • Elevate floor of mouth • Move hyoid bone posterior and superior • Jaw opener |
|
Prevertebral Muscles |
|||
|
Longus capitis Longus colli |
• Anterior tubercles of transverse processes of C3-C6 • Bodies of C4-T3; anterior tubercles of transverse processes of C3-C6 |
• Basilar part of occipital bone • Anterior arch of C1; anterior tubercles of transverse processes of C5-C6, anterior bodies of C2-C4 |
• Flex head • Flex neck, rotate and bend neck laterally |
|
Back of Neck—Posterior Triangle Scalene Muscles |
|||
|
Anterior Middle Posterior Trapezius Levator scapulae Splenius capitis Splenius cervicis |
• Anterior tubercles of transverse processes of C3-C6 • Posterior tubercles of transverse processes of C2-C7 • Posterior tubercles of transverse processes of C4-C6 • Occipital bone and spinous processes C7-T12 • Transverse processes of upper four cervical vertebrae • Lower cervical and upper thoracic vertebrae • Spinous processes of T1-T6 and ligamentum nuchae |
• Scalene tubercle of first rib • First rib • Second rib • Clavicle; acromion; scapular spine • Vertebral border of the scapula • Occipital bone • Posterior tubercles of transverse processes of C1-C4 |
• Elevates first rib, flexes cervical vertebrae • Elevates first rib, flexes cervical vertebrae • Laterally flexes head; rotates head and neck • Elevates the scapula • Raises the scapula • Extends head • Extends head |
Muscles Within the Posterior Triangle
The muscles of the posterior triangle include the trapezius, splenius capitis, levator scapulae, and anterior, middle, and posterior scalene muscles. The trapezius muscle, a superficial muscle located on the posterior portion of the neck, elevates the scapula. It originates from the occipital bone and spinous processes of C7-T12 to insert on the clavicle, acromion, and spine of the scapula (Figs. 5.79 and 5.80). Located just anterior to the trapezius muscle, the splenius capitis muscle arises from the lower cervical and upper thoracic vertebrae to insert on the occipital bone and acts to extend the head (Figs. 4.54, 5.54, and 5.55). The levator scapulae muscle is located in the posterolateral portion of the neck. It arises from the transverse processes of the upper four cervical vertebrae to insert on the vertebral border of the scapula and acts to raise the scapula (Figs. 5.77-5.79). The scalene muscle group (anterior, middle, and posterior scalene muscles) is located in the anterolateral portion of the neck. The muscles originate from the transverse processes of the cervical vertebrae to insert on the first two ribs.
Together, the scalene muscles act to elevate the upper two ribs and flex the neck. The anterior and middle scalene muscles can serve as landmarks for the brachial plexus as it courses between them (Figs. 5.77 and 5.78).
(These muscles are identified on Figs. 5.52-5.69 and listed in Table 5.4.) Two other prominent muscle groups found in the neck are the erector spinae and transversospinal, which are discussed in Chapter 4.
VASCULAR STRUCTURES
The extracranial vessels of the neck include the carotid and vertebral arteries and the jugular veins (Tables 5.5 and 5.6). These vessels are located primarily in the lateral portions of the neck (Figs. 5.81-5.86). The vascular structures can be identified in the sequential images in Figs. 5.56-5.69.
Carotid Arteries
The right common carotid artery arises from the brachiocephalic trunk posterior to the sternoclavicular joint. The left common carotid artery arises directly from the aortic arch (Fig. 5.81). The common carotid arteries lie medial to the internal jugular vein and bifurcate into the internal and external carotid arteries at approximately the level of the third and fourth cervical vertebrae (C3-C4). Located on the external surface at the bifurcation of the common carotid artery is the carotid body, a small neurovascular structure that acts as a chemoreceptor to sense changes in the chemical composition of blood to regulate oxygen and pH levels (Fig. 5.82). The internal carotid artery ascends the neck, vertically, to enter the base of the skull through the carotid canal of the temporal bone. At its origin, there is a dilatation called the carotid sinus, which contains baroreceptors that react to changes in arterial blood pressure (Fig. 5.82). The internal carotid artery has no branches in the neck but has branches in the head to supply blood to the orbit and brain. As the external carotid artery ascends the neck, it passes through the parotid gland to the level of the temporomandibular joint, where it divides into its terminal branches to supply blood to the face and neck. These branches include the superior thyroid, lingual, facial, occipital, posterior auricular, and ascending pharyngeal arteries (Figs. 5.81-5.85 and Table 5.5). The external carotid artery changes position in relation to the internal carotid artery as it ascends the neck. At its lower level, the external carotid artery is anterior and medial to the internal carotid artery and then becomes anterior and lateral to the internal carotid artery at its higher level (Figs. 5.56-5.69).
Carotid body tumors are the most common paraganglioma of the head and neck. These tumors develop within the adventitia of the medial aspect of the carotid bifurcation. The most common presentation is as an asymptomatic palpable neck mass in the anterior triangle of the neck. As the tumor enlarges and compresses the carotid artery and the surrounding nerves, other symptoms may also be present, such as pain, tongue paresis, hoarseness, Horner syndrome, and dysphagia. These tumors are treated with either surgery or radiotherapy.
Vertebral Arteries
The vertebral arteries begin as a branch of the subclavian artery and ascend the neck through the transverse foramina of C6-C1. They then enter the foramen magnum and join to form the basilar artery. The vertebral and basilar arteries supply blood to the posterior aspect of the brain (Figs. 5.56-5.69 and 5.82-5.85).
TABLE 5.5 Arteries of the Neck
|
Arteries of the Neck |
Origin |
Branches |
|
Common Carotid Artery |
Internal and external carotid arteries |
|
|
Left Common Carotid Right Common Carotid |
Aortic arch Right brachiocephalic artery |
|
|
Internal Carotid Artery |
Common carotid artery |
Ophthalmic, anterior and middle cerebral arteries |
|
External Carotid Artery |
Common carotid artery |
Superior thyroid, lingual, facial, occipital, posterior auricular, and ascending pharyngeal arteries |
|
Vertebral Arteries |
Subclavian artery |
Posterior inferior cerebellar artery |
TABLE 5.6 Veins of the Neck
|
Veins of the Neck |
Termination |
Tributaries |
|
Internal jugular vein |
Subclavian vein |
Inferior petrosal sinus, facial, lingual, pharyngeal, superior and middle thyroid, and occasionally the occipital veins |
|
External jugular vein |
Subclavian vein |
Retromandibular, anterior jugular, temporal, and maxillary veins, and occasionally the occipital vein |
|
Vertebral veins |
Brachiocephalic vein |
Internal and external vertebral venous plexuses and deep cervical veins |
Jugular and Vertebral Veins
The internal jugular veins drain blood from the brain and superficial parts of the face and neck and are typically the largest of the vascular structures of the neck (Table 5.6). The internal jugular veins commence at the jugular foramen in the posterior cranial fossa and descend the lateral portion of the neck to unite with the subclavian vein to form the brachiocephalic vein (Figs. 5.81 and 5.86). The internal jugular veins typically run lateral to the common carotid artery and posterior to the internal carotid artery at the upper levels of the neck (Figs. 5.56-5.69). Tributaries of the internal jugular vein include the inferior petrosal sinus, facial, lingual, pharyngeal, superior, and middle thyroid veins, and often the occipital vein. One of these tributaries, the facial vein, is commonly identified as it drains the anterior and lateral regions of the face (Fig. 5.86).
The external jugular veins begin near the angle of the mandible and cross the SCM just beneath the skin to empty into the subclavian vein. Tributaries of the external jugular veins include the retromandibular and anterior jugular veins and occasionally the occipital veins. Blood from the lateral region of the face is drained by the retromandibular vein that courses inferiorly through the parotid gland. The anterior jugular vein begins at approximately the level of the hyoid bone and drains blood from the lower lip. This vessel passes beneath the SCM to open into the termination of the external jugular vein. Jugular veins are identified in Figs. 5.56-5.69.
The vertebral veins course within the transverse foramina of the cervical vertebrae along with the vertebral arteries to drain the cervical spinal cord and the posterior surface of the skull (Figs. 5.53, 5.54, 5.61, and 5.69; see also Chapter 4, Fig. 4.132). The vertebral veins drain into the posterior aspect of the brachiocephalic vein. The vascular structures can be identified on the sequential images in Figs. 5.52-5.69.
REFERENCES
Applegate, E. (2010). The anatomy and physiology learning system (4th ed.). St. Louis: Saunders.
Fehrenback, M. J., & Herring, S. W. (2017). Illustrated anatomy of the head and neck (5th ed.). St. Louis: Elsevier.
Frank, G. (2012). Merrill’s atlas of radiographic positions and radiologic procedures (12th ed.). St. Louis: Mosby.
Haaga, J. R., & Boll, D. T. (2017). CT and MRI of the whole body (6th ed.). Philadelphia: Elsevier.
Larsen, W. J. (2002). Anatomy: Development, function, clinical correlations. Philadelphia: Saunders.
Mosby. (2012). Mosby’s medical, nursing, and allied health dictionary (8th ed.). St. Louis: Mosby.
Ryan, S., & McNicholas, M. (2010). Anatomy for diagnostic imaging (3rd ed.). Philadelphia: Saunders.
Seidel, H. M., Ball, J. W., & Dams, J. E., et al. (2010). Mosby’s guide to physical examination (7th ed.). St. Louis: Mosby.
Som, P. M., & Curtin, H. D. (2011). Head and neck imaging (5th ed.). St. Louis: Mosby.
Standring, S. (2012). Gray’s anatomy: The anatomical basis of clinical practice (41st ed.). New York: Elsevier.
