Gross Anatomy base material 6

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31

Root of the neck

 

 

OPTIONAL READING

Moore, Clinically Oriented Anatomy, 7th ed., Deep structures of neck section through Nerves in root of neck.

CHAPTER CONTENT S

DEEP NECK AND R OOT OF THE NECK SKELE TAL FR AME W ORK

PRE VERTEBR AL MUSCLES IN THE NECK

DEEP NECK MUSCLES/MUSCLES REL ATED TO THE R OOT OF THE NECK

BLOOD AND LY MPH VESSELS ASSOCI ATED WITH THE R OOT OF THE NECK

NER VES

OT H E R O R G A N S

 

Root of the neck

 

 

The root of the neck (base of the neck, cervicothoracic region) is important because it is the region of continuity between the neck andthorax, and the neck and upper limbs. It can be somewhat confusing since neither the origin nor the destination of many important structures can be seen, yet you must know something about these structures in order to make sense of their functional significance.

 

Skele tal fr ame w ork

  • The bony architecture underlying the root of the neck is the superiorthoracic aperture. Structures traverse this opening in order to pass from or to the thorax, neck, and upper limb. Let’s quickly review its boundaries:
  • T-1 vertebra posteriorly
  • Suprasternal notch anteriorly
  • The first ribs laterally

 

The medial part of the clavicle is also an important landmark in the rootof the neck.

 

Pre vertebr al muscles in the neck

  • The scalene muscles, part of the prevertebral group of muscles, figure prominently when describing nerves and vessels in the root of the neck. The three scalene muscles (geometry buffs – what is a “scalene” triangle?) are located anterior and lateral to the cervical vertebrae, deep to the sternocleidomastoid. They attach above to the transverse processes of C-3 through C-7 vertebrae and below to the upper two ribs. They function to flex the neck and can also actas accessory respiratory muscles by raising the first two ribs during inspiration. The scalene muscles are covered externally by the prevertebral fascia.
  • Anterior scalene: inserts onto rib 1; phrenic nerve courses on its surface, subclavian vein passes anterior, and subclavian artery passes posterior
  • Middle scalene: inserts on the first rib behind the anterior scalene. The gap between the anterior and middle scalene muscles is traversed by the brachial plexus and the subclavian artery
  • Posterior scalene: small, inserts on rib 2; can be fused with middle scalene. The middle and posterior scalene muscles are located in the floor of the posterior triangle.

Figure 31.1 GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.185.

 

The other muscles in the prevertebral group are the longus capitis andlongus colli (also called longus cervicis). These muscles are in the deep neck, posterior to the neck viscera (pharynx, esophagus). Like the scalene muscles, they are covered by prevertebral fascia. The longus capitis attaches above to the occipital bone and below to the cervical vertebrae. The longus colli attaches above and below to the bodies and transverse processes of cervical vertebrae. These muscles flex the head and neck. The details of these muscles are not too important, but they are landmarks for locating the sympathetic trunks, which we will see in lab.

 

Blood and ly mph vessels associ ated with the r oot of the neck

  • Subclavian arteries: these have different origins (review these!), but similar

courses in the root of the neck. Both subclavian arteries arch over the lung apices posterior to the anterior scalene muscles and dive deep tothe middle part of the clavicle. Their branches are best studied by dividing the artery into three parts, based on its relationship to the anterior scalene muscle:

  • Part I: medial to anterior scalene; the lung apices, cervicalpleura, and sympathetic trunks lie posteriorly
  • Part II: deep to anterior scalene
  • Part III: lateral to anterior scalene
  • Beyond the first rib, the subclavian artery changes its name to become the

axillary artery.

 

  • Three large branches arise from Part 1, one small branch arisesfrom Part 2, and typically there are no branches from Part 3.However, variations do occur.
  • Vertebral artery: From Part 1 – ascends through the transverse foramina

of cervical vertebrae 1 through 6 (misses the 7th) and enters the skull through foramen magnum. The two vertebral arteries fuseto form the basilar artery in the cranial cavity

  • Thyrocervical trunk: short stump from Part 1, near the medialborder of anterior scalene – gives off three major branches
  • Suprascapular artery: crosses anterior scalene, phrenic nerve, and brachial plexus; dives deep to clavicle; suppliesscapula and scapular muscles
  • Transverse cervical artery: Crosses the anterior scalenemuscle and brachial plexus, parallel to and above thesuprascapular artery, then crosses the posterior triangle of the neck. It usually divides into a superficial and deep branch. These supply the brachial plexus, trapezius muscle, and scapular muscles in the back.
  • Common variation: the deep branch of the transverse cervical artery may be absent – instead, it may arisedirectly from the 3rd part of subclavian artery. If this is the case, this variant artery is called the dorsal scapular artery

 

  • Inferior thyroid artery: the largest branch of the thyrocervical trunk. Passes medially, behind the carotid sheath and anterior to the longus colli muscle. Serves the thyroid and parathyroid glands as well as the larynx.
  • Internal thoracic artery: remember this guy from our study of the chest wall? Sure you do! It arises from Part 1 of the subclavian artery and heads south, deep to the costal cartilages and parallel to the lateral borders of thesternum. Supplies the chest wall, diaphragm, and anterior abdominal wall (via its superior epigastric branch).
  • Costocervical trunk: From Part 2. Variable and small – normally gives off two branches that supply the deep neckand upper intercostal spaces. Not too important.
  • Subclavian vein: the continuation of the axillary vein, proximal to rib 1; it courses superficial to the anterior scalene muscle and below the clavicle.
  • Deep to sternoclavicular joint: joins internal jugular vein to form the brachiocephalic vein
  • Only constant tributary: external jugular vein

Figure 31.2 Branches of the subclavian arteries. Note relationship to anterior scalene muscle.

GRAY’ S ANATOMY FOR STUDENTS, 3RD. ED., FIG. 8.187.

 

  • Thoracic duct: passes from the mediastinum into the neck via the superior thoracic aperture, posterior to the esophagus
  • Arches to the left, deep to the carotid sheath and anterior to the arterial branches of the subclavian artery, theanterior scalene muscle, and the phrenic nerve
  • Usually empties into the junction of the left subclavian and internal jugular veins (the left venous angle)
  • Normally receives lymph from all regions of the body below the diaphragm, left side of the thorax, left side of the head and neck, and left upper limb (~ 75% of the body’s lymph drainage).
  • Right lymph duct: formed by the union of lymph trunks from the right side of the thorax, right side of the head and neck, and right upper limb (~ 25% of body’s lymph). Enters the junction of the right subclavian and internal jugular veins (right venous angle). Frequently, the trunks do not unite to form the right lymph duct, but drain independently to the venous system.

Figure 31.3 GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.191.

 

 

 
   

Figure 31.4 Variation in lymph ducts and trunks at root of neck. GRAY’S ANATOMY FOR STUDENTS, 3RD ED., FIG.8.192.

 

CLINIC AL APPLIC ATION

Central Venous Access is a procedure used to place a catheterin a large vein. The venous access site depends on the reason for the placement and the anatomy of the patient. Large veins at the root of the neck (subclavian and internal jugular veins) are often selected. A subclavian approach places the catheter in the subclavian vein under the middle third of the clavicle. An internal jugular insertion is done between the sternal and clavicular heads of the sternocleidomastoid, lateral to the pulsations of the common carotid artery. Usually the right internal jugular vein is selected because it is more vertically in-line with the SVC and there are less complications on the right side, given that the left dome of the lung rises higher into the neck and the thoracic duct is on the left.

 
   

 

Ner ves

  • Brachial plexus: somatic nerve plexus, originates in root of the neck, and terminates in the axilla, where it gives off large nerves that supply the upper limb. Smaller branches are given off in the neck, supplying muscles of the pectoral girdle, primarily those that move the scapula.
  • We will tackle the brachial plexus in detail when we study the upper limb. For now, realize that the roots of the plexus(ventral rami of spinal nerves C-5, C-6, C-7, C-8, and T-1) emerge from the vertebral column between the anterior and middle scalene muscles in the root of the neck.

CLINIC AL APPLIC ATION

THOR A CIC OUTLE T SY NDR OME

Compression or irritation of the brachial plexus and/or subclavian artery in the region between the clavicleand first rib, through which nerves and vessels reach the upper limb

  • Can produce variety of symptoms: pain, numbness, tingling, weakness, or coldness in upper limb
  • Caused by any number of anatomic circumstances:
  • Compression of the inter-scalene space (between anterior and middle scalene muscles)
  • Costoclavicular approximation: reduced space between clavicle and rib 1 (due to trauma or postural problems)
  • An extra rib (cervical rib) or extra-long transverse process of C7
  • Compression by the tendon of pectoralis minor muscle

 

•         Vagus nerves and Recurrent Laryngeal nerves

  • Right: crosses anterior to right subclavian artery; gives off right recurrent laryngeal nerve that loops posterior to the right subclavian artery in the root of the neck.
  • Left: enters the superior mediastinum between the left common carotid and left subclavian arteries; recall that the left recurrent laryngeal nerve originates in the mediastinum, not in the root of the neck
  • Both recurrent laryngeal nerves: ascend in tracheoesophageal grooves to reach larynx
  • Sympathetic trunk: lies posterior to the carotid sheath, deep to the prevertebral fascia, and anterior to the longus capitismuscle. Ascends into the deep neck via the superior thoracic aperture.
  • Does not have chain ganglia associated with each spinal nerve; instead, the original eight embryonic ganglia fused into3 or 4 cervical chain ganglia. Much variation in arrangement! There seem to be two consistent, large sympathetic ganglia in the neck.

Figure 31.6 Vagus and phrenic nerves at the root of the neck. Note the relationship of the subclavian vessels and anterior scalene muscle. GRAY’ S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.188.

 

  • Cervicothoracic ganglion (stellate ganglion): lies anterior to the neck of rib 1, posterior to the vertebral artery origin; formed by the fusion of the first thoracic ganglion and the lowest cervical ganglion.
  • Superior cervical ganglion: the largest and highest ganglion of the sympathetic trunk – lying opposite C2. Contains ALL of the postganglionic sympathetic neuron cell bodies that innervate tissues in the head.
  • Take heart, there are some constants regarding cervical chain ganglia:
  • They all have gray rami communicantes connected to cervical spinal nerves (several spinal nerves may receivegray rami from one ganglion). What is their function?
  • They all give off tiny cervical cardiac nerves, which pass through the superior thoracic aperture to the cardiac autonomic nerve plexus. Function?

Figure 31.7 NETTER, ATLAS OF HUMAN ANATOMY, 8TH ED., PLATE 142 (REVISED).

 

Ot h e r o r g a n s

  • Trachea and esophagus: pass through the center of the superior thoracic aperture. The trachea can be easily palpatedjust above the suprasternal notch. In the tracheoesophageal groove between are the recurrent laryngeal nerves.
  • Apices of the lungs (covered by cervical pleura): project above the level of the first rib, through the superior thoracic aperture into the root of the neck
  • The subclavian artery and vein groove the pleura just anterior to the apex.
  • Note that the lungs and pleura are vulnerable to injuries in the region of the supraclavicular fossa. Trauma to the root of the neck can produce a pneumothorax!

Figure 31.8 Cervical pleura rises into the root of the neck through the superior thoracic aperture. GRAY’S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.186.

 

ADDITIONAL DETAILED VIDEOS FOR YOUR STUDY

4.1.12 Anterior neck muscles.

4.9.1 Subclavian and common carotid arteries.

4.9.8 Branches of thyro-cervical trunk; externalcarotid artery and its branches (just thyrocervical trunk).

1.1.14 Nerves of the shoulder region: the brachial plexus (intro through divisions and trunks)(BP intro, and suprascapular nerve and after).

4.8.14 Sympathetic trunk, cervical plexus(sympathetic trunk part).

 

 

 

 

38

Pterygopalatine fossa

OPTIONAL READING

Clinically Oriented Anatomy, 7th ed., Pterygopalatine fossa section through The bottom line: Pterygopalatine fossa.

The pterygopalatine fossa (PPF) is a small, bilateral bony spaceimmediately behind the maxilla. Shaped like an inverted teardrop, it is about the size of a thumbnail.

Bony borders

  • Anterior = posterior surface of maxilla.
  • Posterior = anterior surface of the pterygoid process of sphenoidbone (the strut of bone from which the medial and lateral pterygoid plates project).
  • Medial = perpendicular plate of the palatine bone.
  • Lateral = open to the infratemporal fossa via the pterygomaxillary fissure.
  • Superior = body of the sphenoid bone (contains sphenoidal sinuses).
  • Inferior = the anterior and posterior walls slope towards each other inferiorly, but don’t quite meet. The gap creates the palatine canalwhich descends from the PPF to the palate.

 

Co m m u n i c at i o n s

The pterygopalatine fossa is small, but mighty; it communicates with manyregions of the head via bony passageways that open on its walls:

 

Wall of PPF

Name of opening

Communicates with . . .

Contents

Anterior

Inferior orbital fissure

Orbit

Infra-orbital nerve of (V2) and artery Zygomatic nerve of

(V2)

Posterior

Formen rotundum

Middle cranial fossa

Maxillary nerve (V2)

Posterior

Pterygoid (Vidian)canal

Middle cranial fossa via foramen lacerum

Nerve of pterygoid canal (Vidian nerve) Artery of pterygoid canal

Medial

Sphenopalatine foramen

Nasal cavity

Sphenopalatineartery Nasopalatine nerve of (V2)

Lateral

Pterygomaxillary

fissure

Infratemporal fossa

Maxillary artery Posterior superior alveolar nerve of (V2)

Floor

Palatine canal

Palate, via greater and lesser palatine foramina

Greater and lesser palatine nerves of(V2) Descending palatine artery

Figure 38.1. CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.97.

Co n t e n t s o f t h e p p f o s s a

The contents of this tiny space are three in number: (1) pterygopalatine ganglion (a parasympathetic ganglion introduced earlier in the course), (2) maxillary nerve (V2) and its branches, and (3) the terminal (third) part of the maxillary artery. As we discuss each of these, it is important to visualize their courses in and out of the PPF through the bony openings we considered above. In lab, use pipe cleaners or wires to simulate the courses of these nerves and vessels.

Figure 38.2 Schematic of PPF showing its connections to other regions of the head. This is a lateral to medial view looking through the pterygomaxillary fissure. CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.98.

Figure 38.3 Anterior view of isolated sphenoid bone. The anterior surfaces of the pterygoid processes (shown in yellow) form the posterior wall of the PPF. The three bony apertures in the posterior wall can be seen best in this view. GRAY’S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.150.

Pterygopalatine ganglion

The largest of the four parasympathetic ganglia in the head, it is said tocontain the largest collection of neuron cell bodies in the head outside the brain.

  • Preganglionic parasympathetic fibers to the pterygopalatine ganglion are supplied by the greater petrosal nerve, a branch of the facial nerve (CN VII). The greater petrosal nerve enters the pterygopalatinefossa through its posterior wall as part of the nerve of the pterygoid canal (Vidian nerve).
  • The pterygopalatine ganglion contains the cell bodies of postganglionic parasympathetic neurons, whose axons aresecretomotor to the lacrimal gland, nasal glands, and glands of the hard and soft palates and nasopharyx. These fibers reach their targets by hitching rides on branches of V2.
  • The nerve of the pterygoid canal is a composite nerve consisting of two parts:
  • Postganglionic sympathetic fibers (deep petrosal nerve) whose cell bodies are in the superior cervical ganglion. These fibers reach the pterygoid canal by ascending along the internal carotid artery in the carotid canal as part of the carotid plexus. Once in the PPF,they are distributed to glands and blood vessels via branches of V2.
  • Preganglionic parasympathetic fibers (greater petrosal nerve) –these fibers leave the genu of the facial nerve in the temporal bone, traverse the floor of the middle cranial fossa under the dura, descend in foramen lacerum, and join the fibers of the deep petrosal nerve at the posterior opening of the pterygoid canal.
  • The greater petrosal nerve also probably carries taste fibers from taste buds on the palate. These special sensory fibers reach the greater petrosal nerve by first ascending from the palate in palatine branches of V2 and then passing through or around the pterygopalatine ganglion. They have cell bodies in the geniculate ganglion of CN VII.

 

Nerve of pterygoid canal = Greater petrosal nerve + deep petrosal nerve.

Figure 38.4. Formation of the nerve of the pterygoid canal. GRAY’S ANATOMY FOR STUDENTS, 3RD ED., FIGURE 8.153.

Maxillary nerve (V2)

As described earlier in our little chat on cranial nerves, V2 carries sensory fibers from the midface and cheekbones, lower eyelids, upper teeth and gingivae, maxillary sinus, palate, nasopharynx, and the mucosa in the posterior-inferior nasal cavity (lateral nasal wall and septum). To reach these areas, V2 first enters the pterygopalatine fossa via the foramen rotundum. Within the fossa, V2 is connected to the pterygopalatine ganglion. Several of the branches of V2 that originate in the PPF pass through the ganglion first, but their nerve fibers do not synapse within it.

Nerves that originate directly from V2 within the pterygopalatine fossa:

  • Posterior superior alveolar nerves – pass through the pterygomaxillary fissure, skirt the infratemporal fossa, and penetrate the body of the maxilla. They carry sensation from the maxillary sinus,upper molar and premolar teeth, and their gingivae.
  • Ganglionic branches (2) – connect to the pterygopalatine ganglion (the ganglion appears to hang from V2 by these tiny supports). Sensorynerve fibers from the palate, nasopharynx, and nasal cavities reach V2through the ganglionic branches. Also, postganglionic parasympatheticand sympathetic nerve fibers leave the pterygopalatine ganglion andjoin V2 through the ganglionic branches.
  • Zygomatic nerve – enters the orbit via the inferior orbital fissure.Passes along the lateral wall of the orbit and divides into zygomaticofacial and zygomaticotemporal nerves, which supply the face and “temple” regions, respectively.
  • Infra-orbital nerve – essentially the continuation of V2 as it leaves the PPF and enters the orbit via the inferior orbital fissure. In the floor of the orbit the

infra-orbital nerve occupies a groove which guides it into the infra-orbital canal, which then transmits the nerve onto the midface through the infra-orbital foramen. Anterior and middle superior alveolar nerves that supply the upper incisor and canine teeth branch from the infra-orbital nerve.

The following nerves are sensory branches of V2 that pass through the pterygopalatine ganglion, thus appearing to beconnected to the ganglion itself.

  • Pharyngeal nerve – sensory to the upper nasopharynx.
  • Greater and lesser palatine nerves – sensory to the hard and soft palates, respectively. They descend in the palatinecanal as two separate nerves, then reach their targets through the greater and lesser palatine foramina.
  • Posterior lateral nasal nerves supply the mucosa of the posterior lateral nasal wall (conchae and meatuses). Some branch directly from the pterygopalatine ganglion, while others are derived from the palatine nerves as they descend in the palatine canal.
  • Nasopalatine nerve – passes through the sphenopalatine foramen, hops across the sphenoid bone, and then passesobliquely forward across the nasal septum. It is sensory to a good portion of the nasal septum, then sends it terminal portion through the incisive fossa to supply the anterior part of the hard palate and gums, behind the upper incisor teeth

Figure 38.5 Branches of V2 in PPF. CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.98.

Concerning ALL of the branches of V2:

  • They carry both sensory and autonomic fibers.
  • Sensory neurons have cell bodies in the trigeminal ganglion.
  • Parasympathetic neurons (postganglionic) have cell bodies in the pterygopalatine ganglion.
  • Sympathetic neurons (postganglionic) have cell bodies in the superior cervical ganglion.

Figure 38.6 Diagrams showing sensory and autonomic pathways in branches of V2. CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.100.

Maxillary artery

The tale of the maxillary artery has already been told = it arises as one of the two terminal branches of the external carotid artery and most of its course is through the infratemporal fossa. Upon reaching the pterygomaxillary fissure, the tail end of the maxillary artery enters the pterygopalatine fossa. Anatomists refer to this as the third (or pterygopalatine) part of the artery. It produces four or five branches within the PPF, but we will only dwell on the important ones here:

  • Infra-orbital artery – enters the orbit via the inferior orbital fissure with the nerve of the same name. Supplies thefloor of the orbit, the inferior rectus and inferior oblique muscles, and the midface.
  • Descending palatine artery – traverses the palatine canal and near its inferior end divides into greater and lesser palatine arteries, supplying the hard and soft palates, respectively, through their corresponding foramina.
  • Sphenopalatine artery – a large artery that is essentially the continuation of the maxillary artery. It is directed mediallythrough the sphenopalatine foramen to enter the lateral wall of the nasal cavity. You will recall that this artery is the primary blood supply to the posterior nasal cavity and that serious epistaxis results if it is damaged.

Figure 38.7. Branches of maxillary artery in PPF. CLINICALLY ORIENTED ANATOMY, 7TH ED., FIGURE 7.98.

 

VIDEOS: TYING IT ALLTOGETHER

Dr. Acland: Thepterygopalatine fossa and maxillary nerve.

UBC: Pterygopalatine fossatraffic analogy.
 

CLINIC AL APPLIC ATION

PTER YGOPAL ATINE GANGLION AND V 2 BLOCKS

Blockage of the pterygopalatine ganglion with an anesthetic hasbeen shown to be useful in management of cluster headaches and various types of facial neuralgias that don’t respond to conventional pharmacologic therapy. The preferred approach to the PPF and ganglion is through the nasal cavity. An applicator with anesthetic (or needle if injected) is positioned just posteriorto the middle nasal concha, allowing the anesthetic to diffuse through the nasal mucosa into the pterygopalatine fossa via the sphenopalatine foramen.

Dentists who wish to block V2 often use the intra-oral approach of injecting an anesthetic into the pterygopalatine fossa via the greater palatine foramen and palatine canal. To do this, an angled needle is advanced 25–30 mm up the palatine canal and an anesthetic solution is introduced, flooding the pterygopalatinefossa (sounds worse than having a root canal!). This blocks V2and numbs all the areas it supplies, allowing the dentist to work on teeth anywhere in the upper quadrants.