|Define the region of the body called the neck.||The neck (L. collum, cervix) joins the head to the trunk and limbs and serves as a major conduit for structures passing between them. In addition, several important organs with unique functions are located here: the larynx, thyroid, and parathyroid glands, for example.|
|Define the skeleton of the neck.|
The skeleton of the neck is formed by the cervical vertebrae (C1-C7), hyoid bone (referred to as the hyoid in common usage), manubrium of the sternum, and clavicles (Fig. 8.1A). The mobile hyoid lies in the anterior part of the neck at the level of the C3 vertebra in the angle between the mandible and thyroid cartilage. The hyoid does not articulate with any other bone and functionally serves as an attachment for anterior neck muscles and a prop to keep the airway open (Fig. 8.1B, C).
| Describe the subcutaneous tissue of the neck (superficial cervical fascia) and list its general|
The subcutaneous tissue of the neck (superficial cervical fascia) is usually a thin layer of connective tissue that lies between the dermis of the skin and the investing layer of deep cervical fascia (Fig. 8.2B, C). It contains:
2.Blood and lymphatic vessels
3.Superficial lymph nodes
4.Variable amounts of fat
5. Anterolaterally, it contains the platysma.
|Describe the three layers of deep cervical fascia.|
The deep cervical fascia consists of three fascial layers (Fig. 8.2):
These layers support the viscera (e.g., the thyroid gland), muscles, vessels, and deep lymph nodes. These fascial layers provide the slipperiness that allows structures in the neck to move and pass over one another without difficulty (e.g., when swallowing and turning the head and neck). These fascial layers form natural cleavage planes, allowing separation of tissues during surgery.
|Describe the investing layer of deep cervical fascia and its attachments. Describe the|
relationship of the investing layer of deep cervical fascia to the sternocleidomastoid and
trapezius muscles. What is the clinical significance of the investing fascia with regard to spread of infection in the neck?
The investing layer of the deep cervical fascia, the most superficial deep fascial layer, surrounds the entire neck deep to the skin and subcutaneous tissue (Fig. 8.2). At the "four corners" of the neck, the investing layer splits into superficial and deep layers of fascia to enclose (invest) the sternocleidomastoid (SCM) and trapezius muscles.
Inferiorly, the investing layer of fascia attaches to the manubrium of the sternum, clavicles, acromions, and spines of the scapulae. The investing layer is continuous posteriorly with the periosteum covering the C7 spinous process and the nuchal ligament (L. ligamentum nuchae) (Fig. 8.2B). Just superior to the manubrium, the fascia remains divided into the two layers that enclose the SCM; one layer attaches to the anterior and the other to the posterior surface of the manubrium.
The investing layer of deep cervical fascia helps prevent the spread of abscesses. If an infection occurs between the investing layer of deep cervical fascia and the muscular part of the pretracheal fascia surrounding the infrahyoid muscles, the infection usually does not spread beyond the superior edge of the manubrium. If, however, the infection occurs between the investing fascia and the visceral part of the pretracheal fascia, it can spread into the thoracic cavity anterior to the pericardium.
|What is the suprasternal space?|| |
A suprasternal space lies between these layers and encloses the inferior ends of the anterior jugular veins, the jugular venous arch, fat, and a few deep lymph nodes (Fig. 8.2A).
| Describe the limits of the pretracheal layer of deep cervical fascia and its muscular and|
the thin pretracheal layer of deep cervical fascia is limited to the anterior part of the neck (Fig. 8.2). It extends inferiorly from the hyoid into the thorax, where it blends with the fibrous pericardium covering the heart. The pretracheal layer includes a thin muscular part, which encloses the infrahyoid muscles, and a visceral part, which encloses the thyroid gland, trachea, and esophagus and is continuous posterosuperiorly with the buccopharyngeal fascia. The pretracheal layer blends laterally with the carotid sheaths.
|What is buccopharyngeal fascia?|| |
Buccopharyngeal fascia marks the posterior end of the pretracheal layer of deep cervical fascia.
| Define the carotid sheath and its extent and|
The carotid sheath is a tubular fascial investment that extends from the cranial base to the root of the neck. This sheath blends anteriorly with the investing and pretracheal layers of fascia and posteriorly with the prevertebral layer of deep cervical fascia. The carotid sheath contains (Fig. 8.2B, C):
1.The common and internal carotid arteries.
2.The internal jugular vein (IJV).
3.The vagus nerve (CN X).
4.Some deep cervical lymph nodes.
5.The carotid sinus nerve.
6.Sympathetic nerve fibers (carotid periarterial plexuses).
The carotid sheath communicates with the mediastinum of the thorax inferiorly and the cranial cavity superiorly. These communications represent potential pathways for the spread of infection and extravasated blood.
|Describe the limits and contents of the prevertebral layer of deep cervical fascia.||Prevertebral-the prevertebral layer of deep cervical fascia forms a tubular sheath for the vertebral column and the muscles associated with it, such as the longus colli and longus capitis anteriorly, the scalenes laterally, and the deep cervical muscles posteriorly (Fig. 8.2). This layer of fascia is fixed to the cranial base superiorly and inferiorly and fuses with the anterior longitudinal ligament centrally at approximately T3 vertebra. The prevertebral layer extends laterally as the axillary sheath (see Chapter 6), which surrounds the axillary vessels and brachial plexus.|
|Describe the retropharyngeal space and its clinical significance.|
The retropharyngeal space is the largest and most clinically important interfascial space in the neck because it is the major pathway for the spread of infection (Fig. 8.2A). It is a potential space that consists of loose connective tissue between the visceral part of the prevertebral layer of deep cervical fascia and the buccopharyngeal fascia. Inferiorly, the buccopharyngeal fascia is continuous with the pretracheal layer of deep cervical fascia. The alar fascia crosses the retropharyngeal space. This thin layer is attached along the midline of the buccopharyngeal fascia from the cranium to the level of the C7 vertebra and extends laterally to blend with the carotid sheath. The retropharyngeal space is closed superiorly by the base of the cranium and on each side by the carotid sheath. This space permits movement of the pharynx, esophagus, larynx, and trachea relative to the vertebral column during swallowing.
Pus from an abscess posterior to the prevertebral layer of deep cervical fascia may extend laterally in the neck and form a swelling posterior to the SCM. The pus may perforate the prevertebral layer of deep cervical fascia and enter the retropharyngeal space, producing a bulge in the pharynx (retropharyngeal abscess). This swelling may cause difficulty in swallowing (dysphagia) and speaking (dysarthria). Similarly, air from a ruptured trachea, bronchus, or esophagus (pneumomediastinum) can pass superiorly in the neck.
|What is alar fascia?|| |
The alar fascia crosses the retropharyngeal space. This thin layer is attached along the midline of the buccopharyngeal fascia from the cranium to the level of the C7 vertebra and extends laterally to blend with the carotid sheath.
|How is the neck divided into four regions?|| |
To allow clear communications regarding the location of structures, injuries, or pathologies, the neck is divided into regions (Fig. 8.3). The four major regions are the (1) sternocleidomastoid region, (2) posterior cervical region, (3) lateral cervical region, and (4) anterior cervical region.
| Describe the sternocleidomastoid region of the neck. Describe the action and innervation|
of the sternocleidomastoid muscle.
The sternocleidomastoid muscle (SCM) visibly divides each side of the neck into anterior and lateral cervical triangles. The region between these triangular regions, corresponding to the area of this broad, strap-like muscle, is the sternocleidomastoid region. The SCM has two heads: the rounded tendon of the sternal head attaches to the manubrium, and the thick fleshy clavicular head attaches to the superior surface of the medial third of the clavicle. The two heads are separated inferiorly by a space, the lesser supraclavicular fossa. The heads join superiorly as they pass obliquely upward to attach to the mastoid process of the temporal bone and the superior nuchal line of the occipital bone.
The sternocleidomastoid muscle has motor innervation supplied by Spinal accessroy Nerve (CN XI).
The sternocleidomastoid muscle has pain and proprioception innervation supplied by C2 and C3.
|What is torticollis? What causes torticollis?|
Torticollis is a contraction of the cervical muscles that produces twisting of the neck and slanting of the head (Fig. B8.1). The most common type of congenital torticollis (wry neck) results from a fibrous tissue tumor (L. fibromatosis colli) that develops in the SCM before or shortly after birth. Occasionally, the SCM is injured when an infant's head is pulled excessively during a difficult birth, tearing its fibers (muscular torticollis). This tearing may result in a hematoma that may develop into a fibrous mass entrapping a branch of the spinal accessory nerve (CN XI), thus denervating part of the SCM. Surgical release of a partially fibrotic SCM from its distal attachments to the manubrium and clavicle may be necessary to enable the child to tilt and rotate the head normally.
Cervical dystonia (abnormal tonicity of the cervical muscles), commonly known as spasmodic torticollis, usually begins in adulthood. It may involve any bilateral combination of lateral neck muscles, especially the SCM and trapezius.
| Describe the posterior cervical region. What is the relationship of the suboccipital region|
to the posterior cervical region?
The region posterior to the anterior border of the trapezius is the posterior cervical region (Fig. 8.3). The suboccipital region is deep to the superior part of this region.
|Describe the borders of the posterior triangle of the neck.|
The lateral cervical region (posterior triangle of the neck) is bounded (Fig. 8.3 and Table 8.1):
-Anteriorly by the posterior border of the SCM.
-Posteriorly by the anterior border of the trapezius.
-Inferiorly by the middle third of the clavicle between the trapezius and the SCM.
-By an apex, where the SCM and trapezius meet on the superior nuchal line of the occipital bone.
-By a roof, formed by the investing layer of deep cervical fascia.
-By a floor, formed by muscles covered by the prevertebral layer of deep cervical fascia.
The lateral cervical region wraps around the lateral surface of the neck like a spiral and is covered by skin and subcutaneous tissue containing the platysma.
| How is the posterior triangle of|
the neck subdivided into the occipital triangle and the omoclavicular (= subclavian) triangle?
For more precise localization of structures, the lateral cervical region is divided into a larger occipital triangle superiorly and a small omoclavicular triangle inferiorly by the inferior belly of the omohyoid (Fig. 8.3).
|Describe the arteries of the posterior triangle of the neck.|
The arteries in the lateral cervical region are:
1.Cervicodorsal trunk (transverse cervical artery) 2.Suprascapular artery
3.Third part of the subclavian artery, and
4. Part of the occipital artery
The cervicodorsal trunk originates from the thyrocervical trunk, a branch of the subclavian artery, and divides into the superficial cervical and dorsal scapular arteries. The cervicodorsal trunk runs superficially and laterally across the phrenic nerve and anterior scalene muscle, 2 to 3 cm superior to the clavicle. It then crosses (passes through) the trunks of the brachial plexus, supplying branches to their vasa nervorum (blood vessels of nerves) and passing deep to the trapezius.
The superficial cervical artery accompanies CN XI along the anterior (deep) surface of the trapezius. The dorsal scapular artery runs anterior to the rhomboid muscles, accompanying the dorsal scapular nerve. The dorsal scapular artery may arise independently, directly from the subclavian artery.
The suprascapular artery, from the cervicodorsal trunk, a branch of the thyrocervical trunk, or from the subclavian artery, passes inferolaterally across the anterior scalene muscle and phrenic nerve. It crosses the subclavian artery (third part) and the cords of the brachial plexus. It then passes posterior to the clavicle to supply muscles on the posterior aspect of the scapula. The suprascapular artery may arise directly from the subclavian artery.
The occipital artery, a branch of the external carotid artery (Fig. 8.5A), crosses the lateral cervical region at its apex and ascends to supply the posterior half of the scalp.
The third part of the subclavian artery supplies blood to the upper limb. It begins approximately a finger's breadth superior to the clavicle, opposite the lateral border of the anterior scalene muscle. It lies posterosuperior to the subclavian vein in the inferior part of the lateral cervical region (Fig. 8.4E). The pulsations of the artery can be felt
on deep pressure in the omoclavicular triangle just superior to the clavicle (Fig. 8.3). The artery is in contact with the first rib as it passes posterior to the anterior scalene muscle; consequently, compression of the artery against this rib can control bleeding in the upper limb.
|Describe the veins of the posterior triangle of the neck|
The veins in the posterior triangle of the neck are:
3.Anterior Jugular Vein
4.Internal Jugular Vein
5.External Jugular Vein
The external jugular vein begins near the angle of the mandible (just inferior to the auricle of the external ear) by the union of the posterior division of the retromandibular vein with the posterior auricular vein (Fig. 8.4A). The EJV crosses the SCM obliquely, deep to the platysma, and then pierces the investing layer of deep cervical fascia, which forms the roof of this region, at the posterior border of the SCM. The EJV descends to the inferior part of the lateral cervical region and terminates in the subclavian vein.
The major venous channel draining the upper limb, the subclavian vein, courses through the inferior part of the lateral cervical region, passing anterior to the anterior scalene muscle and phrenic nerve (Fig. 8.4E). The subclavian vein joins the IJV to form the brachiocephalic vein posterior to the medial end of the clavicle (Fig. 8.4A, E). Just superior to the clavicle, the EJV receives the cervicodorsal (transverse cervical), suprascapular, and anterior jugular veins.
|Describe the nerves of the posterior triangle of the neck.|
The nerves of the posterior triangle of the neck are:
1.Spinal Accessory Nerve (CN XI)
2.Roots of the Brachial Plexus (Anterior Rami C5-C8 and T1)
4.Braches of the Cervical Plexus (C1-C4), deep and superficial
5.Cutaneous Branches of the Cervical Plexus
A.Lesser Occipital Nerve
B.Great Auricular Nerve
C.Transverse Cervical Nerve
8.Accessory Phrenic Nerve
| Describe the course of the spinal|
accessory nerve in the posterior triangle.
The spinal accessory nerve passes deep to the SCM, supplying it before entering the lateral cervical region at or inferior to the junction of the superior and middle thirds of the posterior border of the SCM (Fig. 8.4B). It passes posteroinferiorly, within or deep to the investing layer of deep cervical fascia, running on the levator scapulae from which it is separated by the prevertebral layer of fascia. CN XI then disappears deep to the anterior border of the trapezius at the junction of its superior two thirds with its inferior one third.
| What parts of the brachial plexus are present in the|
The roots of brachial plexus (anterior rami of C5-C8 and T1) appear between the anterior and the middle scalene muscles (Fig. 8.4). Five rami unite to form the three trunks (superior, middle, and inferior) of the brachial plexus (Fig. 8.4E), which descend inferolaterally through the lateral cervical region. The plexus then passes between the first rib, clavicle, and superior border of the scapula (the cervicoaxillary canal) to enter the axilla, providing innervation for most of the upper limb.
|Describe the cervical plexus of nerves.|
The anterior rami of C1-C4 make up the roots of the cervical plexus, which consists of nerve loops. The plexus lies anteromedial to the levator scapulae and middle scalene muscle and deep to the SCM. The superficial branches of the plexus that initially pass posteriorly are cutaneous branches (Fig. 8.4B, C). The deep branches passing anteromedially are motor branches, including the roots of the phrenic nerve and the ansa cervicalis (Fig. 8.5B).
| What are the cutaneous branches of|
the cervical plexus?
Cutaneous branches of the cervical plexus, often called the nerve point of the neck, emerge around the middle of the posterior border of the SCM, and supply the skin of the neck, superolateral thoracic wall, and the scalp between the auricle and the external occipital protuberance. Close to their origin, the roots of the cervical plexus receive communicating branches (L. rami communicantes), most of which descend from the superior cervical ganglion in the superior part of the neck.
|What is the ansa cervicalis?|
The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid sheath.
Branches from the ansa cervicalis innervate three of the four infrahyoid muscles, including the sternohyoid muscle, the sternothyroid muscle, and the omohyoid muscle.
|Define the boundaries of the anterior triangle of the neck.|
The anterior cervical region (anterior triangle of the neck) has a/an (Fig. 8.3B):
-Anterior boundary: formed by the median line of the neck.
-Posterior boundary: formed by the anterior border of the SCM.
-Superior boundary: formed by the inferior border of the mandible.
-Apex: located at the jugular notch in the manubrium of the sternum.
-Roof: formed by subcutaneous tissue containing the platysma.
-Floor: formed by the pharynx, larynx, and thyroid gland.
| What are the four triangles into|
which the anterior triangle of the neck can be subdivided?
The anterior cervical region is subdivided into four smaller triangles:
1.The unpaired submental triangle
three small paired triangles by the digastric and omohyoid muscle
|What are the contents of each of the triangles of the neck? See ECA, Fig. 8.3, p. 597.|
|What are the boundaries of the submental triangle?|
The submental triangle is inferior to the chin. The apex of the triangle is at the mandibular symphysis, the site of union of the halves of the mandible during infancy, and the base of the triangle is formed by the hyoid. Laterally, it is bounded by the right and left anterior bellies of the digastric muscles. The floor of the submental triangle is formed by the two mylohyoid muscles, which meet in a median fibrous raphe (Fig. 8.5D). This triangle contains several small submental lymph nodes and small veins that unite to form the anterior jugular vein (Fig. 8.5A).
|What are the boundaries of the submandibular triangle?|| |
The submandibular triangle is a glandular area between the inferior border of the mandible and the anterior and posterior bellies of the digastric muscle. The floor of the submandibular triangle is formed by the mylohyoid and hyoglossus muscles, and the middle pharyngeal constrictor.
|What are the boundaries of the carotid triangle?|
The carotid triangle is a vascular area bounded by the superior belly of the omohyoid, the posterior belly of the digastric, and the anterior border of the SCM (Fig. 8.5A and B). The common carotid artery ascends into the carotid triangle (Fig. 8.5B and C). Its pulse can be auscultated or palpated by compressing it lightly against the transverse processes of the cervical vertebrae.
|List the Suprahyoid muscles.||The suprahyoid muscles are superior to the hyoid bone and connect it to the cranium. The suprahyoid muscle group includes:|
As a group, these muscles constitute the substance of the floor of the mouth, supporting the hyoid in providing a base from which the tongue functions and in elevating the hyoid and larynx in relation to swallowing and tone production.
|List the Infahyoid muscles.|| The Infahyoid muscles are inferior to the hyoid bone. These four muscles anchor the hyoid, sternum, clavicle, and scapula and depress the hyoid and larynx during swallowing and speaking (Table 8.2). These muscles are:|
| Explain how the infrahyoid muscles can be|
divided into a superficial plane of muscles and a deep plane.
| The infrahyoid group of muscles are arranged in two planes: a superficial plane made up of the sternohyoid and omohyoid, and a deep plane composed of the sternothyroid and thyrohyoid.|
| Which of the infrahyoid muscles|
limits the superior expansion of an enlarged thyroid gland?
|The sternothyroid covers the lateral lobe of the thyroid gland, attaching to the oblique line of the lamina of the thyroid cartilage immediately superior to the gland. This muscle limits superior expansion of an enlarged thyroid gland.|
| What feature of the thyroid cartilage serves as a landmark for the bifurcation of the common|
carotid artery into its terminal branches?
At the level of the superior border of the thyroid cartilage (C4 vertebral level), the common carotid artery divides into the internal and external carotid arteries.
|What is the carotid sinus? What is its function?|| |
Innervated principally by the glossopharyngeal nerve (CN IX) through the carotid sinus nerve, as well as the vagus nerve, the carotid sinus is a baroreceptor (pressoreceptor) that reacts to changes in arterial blood pressure..
|What is the carotid body? What is its function?|
The carotid body, an ovoid mass of tissue, lies on the medial (deep) side of the bifurcation of the common carotid artery in close relation to the carotid sinus (Fig. 8.6C). Supplied mainly by the carotid sinus nerve (CN IX) and by CN X, the carotid body is a chemoreceptor that monitors the level of oxygen in the blood. It is stimulated by low levels of oxygen and initiates a reflex that increases the rate and depth of respiration, cardiac rate, and blood pressure.
|List the branches of the external carotid artery.|| The branches of the external cartoid artery are:|
1.Ascending pharnygeal artery
3.Posterior Auricular Artery
4.Superior Thyroid Artery
"Sometimes A Little Fat Or Picante Makes Super Tacos."
|Name the terminal branches of the external carotid artery.|| |
Each external carotid artery runs posterosuperiorly to the region between the neck of the mandible and the lobule of the auricle, where it is embedded in the parotid gland. Here it divides into two terminal branches: the maxillary and superficial temporal arteries.
|What is the direct continuation of the sigmoid sinus?|
Most veins in the anterior cervical region are tributaries of the IJV, usually the largest vein in the neck (Fig. 8.6B, D). The IJV drains blood from the brain, anterior face, cervical viscera, and deep muscles of the neck. The IJV commences at the jugular foramen in the posterior cranial fossa as the direct continuation of the sigmoid sinus.
| Name the tributaries of the internal|
The tributaries of the IJV are:
1.Inferior Petrosal Vein
5.Superior Thyroid vein
6.Middle Thyroid Vein
*7.Occipital Vein (sometimes)
|Where is the superior bulb of the internal jugular vein located?|| |
The IJV commences at the jugular foramen in the posterior cranial fossa, where its superior bulb is located.
|Where is the inferior bulb of the internal jugular vein located?|
Posterior to the sternal end of the clavicle, the IJV unites with the subclavian vein to form the brachiocephalic vein. The inferior end of the IJV dilates to form the inferior bulb of the IJV (Fig. 8.6D). This bulb has a bicuspid valve that permits blood to flow toward the heart while preventing backflow into the vein
|Describe the termination of the internal jugular vein.|| |
Posterior to the sternal end of the clavicle, the IJV unites with the subclavian vein to form the brachiocephalic vein.
|What cutaneous nerve supplies the skin of the anterior triangle of the neck?||Transverse Cervical Nerve (C2 and C3) suuplies the skin covering the the anterior cervical region.|
|Describe the course of the hypoglossal nerve in the anterior triangle of the neck.|| |
The hypoglossal nerve (CN XII), the motor nerve of the tongue, enters the submandibular triangle deep to the posterior belly of the digastric muscle to supply the muscles of the tongue (Fig. 8.5B-D). Branches of the glossopharyngeal and vagus nerves are located in the submandibular and carotid triangles.
| How would you instruct someone|
to palpate the submandibular gland in a living individual?
The submandibular gland nearly fills the submandibular triangle. It is palpable as a soft mass inferior to the body of the mandible, especially when the tongue is pushed against the maxillary incisor teeth.
| How would you instruct someone|
to palpate the submandibular and submental lymph nodes in a living individual?
The submandibular lymph nodes lie superficial to the gland and, if enlarged, can be palpated by moving the fingers from the angle of the mandible along its inferior border (Fig. SA8.1E). If this is continued until the examiner's fingers meet under the chin, enlarged submental lymph nodes can be palpated in the submental triangle.
| How would you instruct someone|
to palpate the carotid pulse in a living individual?
The carotid pulse can be palpated by placing the index and third fingers on the thyroid cartilage and pointing them posterolaterally between the trachea and SCM. The pulse is palpable just medial to the SCM.