PHARYNX, CRANIOVERTEBRAL JOINTS, PREVERTEBRAL REGION STEVEN J. ZEHREN, PH.D.

SUBDIVISIONS OF PHARYNX

C6 Sphenoid sinus Pharyngeal tubercle of occipital bone NASOPHARYNX Soft palate OROPHARYNX Root of tongue Epiglottis Vertebral bodies LARYNGOPHARYNX C6 The pharynx is part of both the respiratory and digestive systems (ie, parts of the pharynx transmit both air and food). It is divided into three parts: 1) nasopharynx (behind the nasal cavity) which extends from the sphenoid and occipital bones (above) to the soft palate (below) 2) oropharynx (behind the oral cavity) which extends from the soft palate to the epiglottis and 3) laryngopharynx (behind the larynx) which extends from the epiglottis to the lower border of the cricoid cartilage. The laryngopharynx is continuous with the esophagus below (at level of CV6), but anteriorly it opens into the larynx. 2. Thus the pathway for air flow is nasal cavity > nasopharynx > oropharynx > laryngopharynx > larynx > trachea. 3. The pathway for food is oral cavity > oropharynx > laryngopharynx > esophagus. Cricoid cartilage Trachea Esophagus

PHARYNX IN POSTERIOR VIEW Base of skull (5 cm) Note how the pharynx tapers (funnel-shaped) from the base of the skull (widest part, 5 cm.) to its junction with the esophagus (narrowest part of entire digestive tract, 1.5 cm.). Is it any wonder that a bolus of food or foreign object might become trapped at this point? CV6 (1.5 cm) Esophagus

NASOPHARYNX (MUCOSA INTACT) Pharyngeal tonsil Orifice of auditory tube Choana Pharyngeal recess Torus tubarius Torus levatorius Salpingopharyngeal fold Uvula Pharyngeal isthmus The SUPERFICIAL FEATURES OF THE NASOPHARYNX are seen in this plate.   In the lateral wall of the nasopharynx is the OPENING OF THE AUDITORY TUBE. The TORUS TUBARIUS is a mucosal bulge just above the opening of the auditory tube and is produced by the underlying cartilage of the tube. Posterior to the torus is a blind cul-de-sac, the PHARYNGEAL RECESS. Cancers sometimes develop here. In the roof of the nasopharynx is a mass of lymphatic tissue, the (NASO)PHARYNGEAL TONSIL. The nasopharyngeal tonsil can become swollen ("adenoids") to the point that the respiratory passage is blocked and the child must breathe through the mouth. If not treated, persistent mouth breathing can lead to malgrowth of the face. The tonsils involute after puberty. Note also the torus levatorius and salpingopharyngeal fold. These mucosal elevations are produced by underlying muscles. 3. The opening connecting the nasopharynx with the nasal cavity is the choana (pleural choanae); that connecting the nasopharynx with the oropharynx is the pharyngeal isthmus. The pharyngeal isthmus is bounded anteriorly by the uvula (of soft palate) and posteriorly by the wall of the pharynx.

NASOPHARYNX (MUCOSA REMOVED) Cartilage of auditory tube Tensor (veli) palatini Levator (veli) palatini Salpingopharyngeus The PHARYNGEAL MUCOSA HAS BEEN REMOVED TO EXPOSE THE UNDERLYING MUSCLES AND OTHER STRUCTURES. Note the cartilage of the auditory tube and three muscles: tensor palati, levator palati and salpingopharyngeus. These muscles are used in swallowing.

PHARYNGOTYMPANIC (AUDITORY) TUBE Orient: Coronal Section The auditory tube connects the nasopharynx with the tympanic (middle ear) cavity; hence it is also known as the pharyngotympanic tube. It serves to equalize pressure in the middle ear with the atmospheric pressure. It also acts as a conduit for the spread of infection into the middle ear! Nasopharynx Tympanic cavity Pharyngotympanic (auditory) tube

OROPHARYNX IN ANTERIOR VIEW (BOUNDARIES OF OROPHARYNGEAL ISTHMUS) Soft palate Palatoglossal arch Dorsum of tongue The opening by which the oropharynx communicates with the oral cavity is the OROPHARYNGEAL ISTHMUS. This opening is bounded by the soft palate above, dorsum of the tongue below, and on the sides by the palatoglossal arches.

Median glossoepiglottic fold Lateral glossoepiglottic fold Epiglottis Median glossoepiglottic fold Lateral glossoepiglottic fold Vallecula Palatopharyngeal arch Palatine tonsil Lingual tonsil Root Palatoglossal arch The lateral wall of the oropharaynx is marked by two folds (arches), the palatoglossal arch and the palatopharyngeal arch. These arches are folds of mucosa covering muscles of the same name. Between the arches is the palatine tonsil. (The tonsil has crypts (tubular indentations) which open onto its medial surface). The post. one-third of the tongue (root) lies in the oropharynx and is rough due to nodules of lymphatic tissue (lingual tonsil). Note the median and lateral glossoepiglottic folds of mucosa with the vallecula in between. During surgery, an intubation tube can be secured by hooking it into the valleculae. Body

TONSILLAR BED Tonsillar br. of facial a. Superior constrictor External palatine (paratonsillar) v. Glossopharyngeal n. (IX) Orient: Lateral wall of oropharynx with palatine tonsil and mucosa removed. Point out palatoglossus and palatopharyngeus muscles, and posterior 1/3 of tongue (not labelled). The palatine tonsil lies in the tonsillar bed, the muscular part of which is formed by the sup. pharyngeal constrictor m. Other structures lying in the tonsillar bed include IX (which is sensory to the tonsil and post. 1/3 of the tongue), the ext. palatine v. (paratonsillar v.) and numerous (five) small tonsillar aa.(including the tonsillar br. of the facial a.) With such a rich blood supply it is not surprising that hemorrhage during tonsillectomy can be severe. Patients may experience a temporary loss of sensation on the post. one-third of the tongue following tonsillectomy due to edema and compression of IX.

TONSILLAR BED Superior constrictor Styloid process & Stylohyoid ligament The styloid pr. may be very long and extend into the region of the palatine tonsil. This can impinge on the tonsil and cause pain.   Lesser horn of hyoid bone

Peritonsillar Abscess Note the position of the peritonsillar abscess. It is located just lateral to the palatine tonsil and just medial to the superior constrictor m. If the abscess broke through the superior constrictor m., it would enter the lateral pharyngeal space, and from there could spread into the retropharyngeal space.

with fold over internal laryngeal n. Choanae NASOPHARYNX Soft palate OROPHARYNX Root of tongue Orient: The POST. WALL OF THE PHARYNX HAS BEEN SPLIT IN THE MIDLINE AND REFLECTED LATERALLY. The relationships of the three parts of the pharynx to each other and to the cavities with which the pharynx communicates are well displayed. Note the choanae for communication with the nasal cavity and the aditus (inlet) of the larynx (bounded on either side by the aryepiglottic folds). On either side of the aditus is a blind cul-de-sac, the piriform recess. These recesses act as lateral food channels during swallowing. Just deep to the mucosa of the recess is the internal laryngeal n. This is a very imp. sensory nerve to the upper part of the larynx. It can be damaged when trying to extract a sharp fish bone, etc. which has become lodged in the piriform recess. Epiglottis Aryepiglottic fold LARYNGOPHARYNX Piriform recess with fold over internal laryngeal n.

NERVES DEEP TO MUCOSA OF PIRIFORM RECESS Internal laryngeal n. Recurrent laryngeal n. With the mucosa removed, note the internal laryngeal n. in the region of the piriform recess.

WALDEYER’S RING Orient: The pharynx is characterized by a ring of lymphatic tissue (Waldeyer's ring): superiorly the (naso)pharyngeal tonsil, inferiorly the lingual tonsil and laterally the two palatine tonsils. The function of this ring is to produce antibodies to ingested and inspired bacteria.

WALL OF PHARYNX Mucous membrane Pharyngobasilar fascia Muscle layer Buccopharyngeal fascia 1. The WALL OF THE PHARYNX consists of FOUR LAYERS: 1) MUCOSA (innermost) 2) PHARYNGOBASILAR FASCIA (esp. thick near the base of the skull) 3) MUSCULAR (with inner longitudinal and outer circular parts) and 4) BUCCOPHARYNGEAL FASCIA (outermost). I will concentrate on the muscular layer.

MUSCLES OF PHARYNX

THREE PHARYNGEAL CONSTRICTOR MUSCLES Superior constrictor Pterygomandibular raphe Middle constrictor Inferior constrictor The OUTER LAYER OF PHARYNGEAL MUSCLES is composed of the THREE CONSTRICTORS. The fibers of the constrictors are circularly arranged with the inf. constrictor overlapping the mid. constrictor, and the mid. constrictor overlapping the sup. constrictor (like three stacked flower pots). The constrictors take their origin from bones and cartilages anteriorly and sweep back to a common insertion into a median raphe posteriorly. Thus, they contribute to the lat. and post. walls of the pharynx but not to the ant. wall. Esophagus

Pterygomandibular raphe Superior pharyngeal constrictor m. Middle pharyngeal constrictor m. The SUP. CONSTRICTOR M. originates from the pterygomandibular raphe and the bone at either end of the raphe (ie, the pterygoid hamulus and the post. end of the mylohyoid line of the mandible). The raphe also serves for part of the origin of the buccinator m. 2. The MID. CONSTRICTOR M. originates from the hyoid bone and the lower end of the stylohyoid lig.  3. The INF. CONSTRICTOR M. has two parts: 1) THYROPHARYNGEUS (originates from thyroid cartilage) and 2) CRICOPHARYNGEUS (originates from cricoid cartilage). The cricopharyngeus acts as a sphincter to prevent air from entering the esophagus (causing "gas"). Clinically the cricopharyngeus is imp. because it may undergo spasm leading to obstruction of the food channel. As a result an outpocketing of the pharyngeal wall (HYPOPHARYNGEAL DIVERTICULUM) may develop. Such a diverticulum may become so large that it may interfere with the nutrition of the individual and have to be treated surgically! All three constrictor muscles insert into a midline raphe in the posterior wall of the pharynx. Hyoid bone Inferior pharyngeal constrictor m. Zone of sparse muscle fibers Thyroid cartilage Cricopharyngeus m. (part of inferior constrictor m.) Cricoid cartilage

pharyngotympanic tube Styloid process Cartilaginous part of pharyngotympanic tube Styloid process Stylopharyngeus m. Salpingopharyngeus m. Palatopharyngeus m. Pharyngobasilar fascia Pharyngeal raphe Stylopharyngeus m. Superior constrictor m. Orient: Posterior wall of pharynx split in midline and reflected laterally on one side. The INNER LONGITUDINAL LAYER OF PHARYNGEAL MUSCLES is composed of the stylopharyngeus, palatopharyngeus and salpingopharyngeus. The STYLOPHARYNGEUS descends from the styloid pr. and passes between the sup. and mid. constrictor mm. (useful relationship for identifying the constrictor mm. in lab). The PALATOPHARYNGEUS descends from the palate. The stylo- and palatopharyngeus blend inferiorly and have a common insertion into the thyroid cartilage and wall of the pharynx. The SALPINGOPHARYNGEUS is a tiny muscle which descends from the cartilage of the auditory tube ("salpinx" means tube) and blends with the palatopharyngeus.   Middle constrictor m. Longitudinal pharyngeal mm. Inferior constrictor m. Posterior border of thyroid cartilage lamina Cricopharyngeus m.

(Mechanism of Swallowing) Tensor palati m. Levator palati m. Salpingopharyngeus m. Passavant’s ridge Superior constrictor m. Palatopharyngeus m. Stylopharyngeus m. Mylohyoid m. Middle constrictor m. Optional (Can discuss or students could study this slide on their own). Orient: Median section. SWALLOWING (DEGLUTITION) can be described in three stages. In the FIRST STAGE, which is voluntary and occurs in the mouth, the bolus of food is pushed back into the oropharynx by the tongue and mylohyoid mm. The SECOND STAGE is involuntary and occurs in the pharynx. This is a rapid and complex stage. The respiratory passage is closed off both below (at the laryngeal inlet) and above (at the pharyngeal isthmus). The pharyngeal isthmus is closed by pulling the soft palate against the post. pharyngeal wall. The tensor and levator palati mm. move the soft palate while the uppermost fibers of the palatopharyngeus m. (Passavant's ridge) pull the pharyngeal wall forward. The pharynx is then elevated by the three longitudinal muscles (stylo-, palato- and salpingopharyngeus) to receive the bolus. This is followed by the serial contraction of the three constrictors which push the bolus toward the esophagus. The THIRD STAGE occurs in the esophagus. It is also involuntary and occurs rapidly. Peristaltic action of the esophageal musculature forces the bolus inferiorly toward the stomach. Optional: The origin of the mid. constrictor from the hyoid bone and stylohyoid lig. is well illustrated.   Inferior constrictor m. Cricopharyngeus m. Circular esophageal m.

FOUR GAPS IN THE PHARYNGEAL MUSCULATURE Levator palati Superior constrictor Stylopharyngeus & IX Middle constrictor Internal laryngeal n. & superior laryngeal a. Various structures pass through gaps in the pharyngeal musculature: 1. Levator palati m. passes through the gap between the base of the skull and the sup. constrictor m. 2. Stylopharyngeus m. and IX pass through the gap between the sup. and mid. constrictor mm. 3. Int. laryngeal n. and sup. laryngeal a. pass through the gap between the mid. and inf. constrictor mm. 4. Rec. laryngeal n. and inf. laryngeal a. pass deep to the inferior border of the inf. constrictor m. Inferior constrictor Recurrent laryngeal n. & inferior laryngeal a.

NERVES OF PHARYNX

MOTOR INNERVATION OF PHARYNX Glossopharyngeal n. (to stylopharyngeus) Pharyngeal branch of X (to other pharyngeal mm.) X The MOTOR INNERVATION TO THE PHARYNGEAL MUSCLES is via IX and X. The STYLOPHARYNGEUS (shown but not labelled) is innervated by a small twig from the glossopharyngeal n. (IX). Note how IX "winds around" the stylopharyngeus on its way to the tongue. ALL OF THE OTHER PHARYNGEAL MM. receive their innervation from the pharyngeal br. of X. (In both cases the functional component is SVE).

(Medial view) Trigeminal (V2) via pharyngeal branch of pterygopalatine ganglion Glossopharyngeal (IX) via pharyngeal plexus via tonsillar branches taste plus general sensation via lingual branches The SENSORY INNERVATION OF THE PHARYNX is via three cranial nerves. ABOVE THE ORIFICE OF THE AUDITORY TUBE the nerve supply is V2 (GSA). BETWEEN THE AUDITORY TUBE AND LARYNGEAL INLET the innervation is by IX (GVA). BELOW THE LARYNGEAL INLET the innervation is by X (also GVA). There may be some overlap in the regions supplied. The GAG REFLEX is elicited when the posterior wall of the oropharynx is touched (eg, with a toothbrush). This causes elevation of the soft palate and movement of the tongue. The afferent limb of the reflex is IX (and perhaps X); the efferent limb involves X and XII.   Vagus (X) via internal laryngeal n. Trigeminal n. (V) Glossopharyngeal n. (IX) Vagus n. (X) Facial n. (VII)

PHARYNGEAL PLEXUS OF NERVES Pharyngeal br. of IX (GVA) Pharyngeal br. of X (SVE) The PHARYNGEAL PLEXUS OF NERVES is a network of fibers located primarily on the mid. constrictor m. It receives contributions from three sources: 1) pharyngeal br. of IX (GVA, sensory to mucosa of pharynx) 2) pharyngeal br. of X (SVE, motor to most of the pharyngeal muscles) and 3) pharyngeal br. of sup. cervical sympathetic ganglion (not shown)(GVE, vasomotor).  

BLOOD SUPPLY & LYMPHATICS OF PHARYNX

ARTERIAL SUPPLY TO PHARYNX Ascending pharyngeal a. Superior constrictor m. Ascending pharyngeal a. The ARTERIAL SUPPLY TO THE PHARYNX is from the ascending pharyngeal a. and the sup. and inf. thyroid aa. Superior thyroid a. Inferior thyroid a.

VENOUS DRAINAGE OF PHARYNX The PHARYNGEAL PLEXUS OF VV. lies on the post. wall of the pharynx. This plexus drains into the IJV.

Retropharyngeal nodes Jugulodigastric node Superior deep cervical nodes LYMPHATIC DRAINAGE OF THE PHARYNX is to the retropharyngeal and sup. deep cervical nodes. The jugulodigastric node (the uppermost deep cervical node) receives most of the lymph from the palatine tonsil and is therefore sometimes referred to as the tonsillar node.

RELATIONSHIPS OF PHARYNX

NEUROVASCULAR RELATIONSHIPS XI IX XII Sympathetic trunk Com. & int. carotid aa., IJV, X 1. The last four cranial nerves and the sympathetic trunk are related to the pharynx. 2. IX winds around stylopharyangeus m. X descends in carotid sheath (look also for sup. laryngeal br. of X) XI passes into deep surface of SCM. XII curves inferiorly and anteriorly toward tongue, crossing lateral to both carotid aa. (Note that XII is closely bound to X at skull base and at first appears to be a branch of X). 3. Sympathetic trunk has been pulled medially in this slide. It lies just posterior to carotid sheath.

CRANIOVERTEBRAL JOINTS

AXIS (C2): POSTEROSUPERIOR VIEW Ant. tubercle Facet for dens Ant. arch Lateral mass Transverse pr. Tubercle for transverse lig. Transverse foramen Post. arch Sup. facet for occipital condyle Post. tubercle Groove for vertebral a. ATLAS (C1): SUPERIOR VIEW Dens Post. facet for transverse lig. Sup. facet for atlas Atlas: a. Atlas is essentially a ring of bone, consisting of two lateral masses connected by ant. and post. arches. b. Transverse processes project further laterally than other cervical vertebrae (giving mechanical advantage to muscles that attach to it (eg., inf. oblique). Transverse foramen for passage of vertebral a. c. Ant. tubercle is for attachment of ant. longitudinal lig. and upper end of longus colli m. d. Atlas has no spine, just a post. tubercle on post. arch. e. Post. arch has groove for vertebral a. f. Lateral masses have concave, kidney-shaped facets superiorly for reception of the occipital condyles. g. Each lateral mass also has a tubercle for attachment of the transverse ligament of the atlas which runs from one lateral mass to the other. h. Anterior arch has a facet on its posterior aspect for articulation w/ the dens. 2. Axis a. Strongest of cervical vetebrae. b. Has two large, flat bearing surfaces, superior articular facets, for articulation w/the atlas above. c. Dens (odontoid process) represents body of atlas and projects superiorly to articulate with the ant. arch of the atlas. Dens also has a facet on its posterior aspect for the transverse lig. of the atlas. d. Spinous process of axis is large and bifid. Body Interarticular part Transverse pr. Inf. articular pr. Spinous pr. AXIS (C2): POSTEROSUPERIOR VIEW

Atlas and Axis (superior view) Dens Facet for occipital condyle C1 C2 transverse ligament C3 The joints between the sup. articular facets of the atlas and the occipital condyles are the ATLANTOOCCIPITAL (AO) JOINTS. Together the two joints act as an ELLIPSOID JOINT. They permit flexion and extension of the head, as well as lateral flexion (bending to the side). There are three ATLANTOAXIAL (AA) JOINTS. The TWO LAT. AA JOINTS are between the inf. articular facets of the atlas and the sup. articular facets of the axis. These are GLIDING JOINTS. The MEDIAN AA JOINT is a PIVOT JOINT. It is formed by the articulation between the dens and the ant. arch of the atlas, and between the dens and the transverse lig. of the atlas . When one rotates the head from side to side (eg, shaking the head "no"), the skull + atlas rotate together around a central stationary pivot --- the dens. C4 Lateral atlanto-axial joints (gliding) Median atlanto-axial joint (pivot) Atlanto-occipital Joints (Ellipsoid) Allow flexion/extension of head (nodding “yes”) Allow lateral flexion of head

ROTATION OF THE HEAD OCCURS AT THE ATLANTO-AXIAL JOINTS

Spinous processes and parts of vertebral arches removed: posterior view Basilar part of occipital bone Tectorial membrane Capsule of AO joint Deeper (accessory part) of tectorial membrane Atlas (C1) Posterior longitudinal ligament Capsule of lateral AA joint Alar ligaments Axis (C2) Capsule of zygopophysial joint (C2-C3) Left side of plate The POST. LONGITUDINAL LIG. runs along the post. surfaces of the vertebral bodies within the vertebral canal. Its upward continuation (above the axis) is the TECTORIAL MEMBRANE. Right side of plate Deep to the tectorial membrane are some imp. ligaments related to the median AA joint. The thick TRANSVERSE LIG. OF THE ATLAS holds the dens against the ant. arch of the atlas. The SUP. & INF. LONGITUDINAL FIBERS pass to the ant. margin of the f. magnum and the body of the axis (resp.). The transverse lig. + the sup. and inf. longitudinal fibers form the CRUCIFORM LIG. The strong ALAR LIGS. pass superolaterally from the dens to the med. aspects of the occipital condyles. Atlas (C1) Superior longitudinal band CRUCIATE LIGAMENT Transverse ligament of atlas Axis(C2) Inferior longitudinal band Deeper (accessory part) of tectorial membrane Principal part of tectorial membrane removed: posterior view

Apical ligament of dens Atlas (C1) Apical ligament of dens Alar ligament Facet of dens (for transverse lig.) Anterior tubercle of atlas Alar ligament Synovial cavities Axis (C2) Dens ON THE LEFT SIDE OF THE PLATE note the ALAR LIGS. These ligs. are also known as "check ligs." because they function to check (restrict) the amount of rotation at the median AA joint. Rupture of an alar ligament results in an increase of ~ 30% in the range of movement to the contralateral side (COA, 5th ed., p.510) ON THE RIGHT SIDE OF THE PLATE note the TRANSVERSE LIG. OF THE ATLAS. Along with the ant. arch of the atlas, the transverse lig. forms a fibrous/bony ring surrounding the dens of the axis. This ring rotates around the dens forming a pivot joint. By keeping the dens against the ant. arch of the atlas, the transverse lig. prevents the dens from post. displacement which could damage the spinal cord. Cruciate ligament removed: posterior view Transverse ligament of atlas Median atlantoaxial joint: superior view

CLINICAL CORRELATIONS

FRACTURE & DISLOCATION OF THE ATLAS (JEFFERSON OR BURST FRACTURE) (On left) Note that the lateral masses are wedge-shaped, with the thick sides of the wedges directed laterally. Thus, vertical compressive forces (as would result from striking the bottom of a pool in a diving accident) tend to drive the lateral masses laterally (arrows), fracturing one or both of the bony arches of the atlas. If the force is great enough, the transverse ligament of the atlas will also rupture. This type of fracture is called a Jefferson (or burst) fracture. 2. Coronal section (on right) showing direction of vertical compressive forces and lateral movement of the lateral masses of the atlas resulting in a Jefferson fracture.

FRACTURE & DISLOCATION OF THE ATLAS (JEFFERSON OR BURST FRACTURE) Note the fractures of both the anterior and posterior arches of the atlas, and the lateral displacement of the lateral masses. 2. A Jefferson fracture in itself does not necessarily result in spinal cord injury, b/c the dimensions of the bony ring actually increase. Spinal cord injury is more likely, however, if the transverse ligament is also ruptured.

PREVERTEBRAL MUSCLES

Rectus capitis anterior m. Basilar part of occipital bone Longus capitis m. (cut) Occipital condyle Jugular process of occipital bone Rectus capitis anterior m. Rectus capitis lateralis m. Transverse process of atlas Longus capitis m. Longus colli m. Students should study this slide on their own 1. O ,I, F of prevertebral mm. a. Longus colli m. O – upper thoracic and lower cervical vertebrae I - cervical vertebrae (more superiorly) (reaches as high as the ant. tubercle of the atlas) F – flexes neck b. Longus capitis m. O – ant. tubercles of transverse prs. of C3 – C6 I - basilar part of occipital bone F – flexes head c. Rectus capitis anterior O – lateral mass of atlas d. Rectus capitis lateralis O - transverse process of atlas I - jugular process of occipital bone All of the prevertebral muscles are innervated by the ventral rami of cervical nerves.

CERVICAL PART OF SYMPATHETIC TRUNK

Superior cervical ganglion Internal carotid n. Superior cervical ganglion External carotid a. & plexus Gray rami communicantes Students should review this material on their own The CERVICAL PART OF THE SYMPATHETIC TRUNK consists of three (sometimes four) ganglia and the longitudinal fibers interconnecting them. This part of the trunk lies post. to the carotid sheath and ant. to the prevertebral mm. (shown but not labelled). The trunk consists largely of ascending presynaptic fibers, the somata of which lie in the lateral horn of the upper thoracic part of the spinal cord. Synapse occurs in either the sup., mid. or inf. cervical ganglia (sometimes there is a fourth ganglion, the vertebral, between the mid. and inf. ganglia). The inf. ganglion is usually (82%) fused with the first thoracic ganglion to form the cervicothoracic (stellate or star-shaped) ganglion. The ansa subclavia is a nerve which loops around the subclavian a. on each side. It connects the inf. cervical (or stellate) ganglion with the vertebral ganglion (as shown here) or the mid. cervical ganglion. Postsynaptic fibers reach structures in the head and neck by several routes including 1) gray rami communicantes to the cervical spinal nerves and 2) traveling along arteries. A GRAY RAMUS COMMUNICANS passes to each cervical spinal nerve. This is true even though there are only three or four cervical ganglia but eight cervical nerves. (The presence of only three or four ganglia is due to the embryonic fusion of separate primordia). The gray rami joining C1-C4 arise from the sup. ganglion and are distributed in part via the cervical plexus to smooth muscle and glands in the skin. 3. TRAVELING ALONG THE INT. & EXT. CAROTID AA. & THE VERTEBRAL A. ARE PLEXUSES OF POSTSYNAPTIC SYMPATHETIC FIBERS. These plexuses use the arteries as "vehicles" to reach involuntary structures (smooth m. and gls.) in the head and neck. In addition the plexuses supply the arteries themselves (vasomotor). Middle cervical ganglion Vertebral ganglion Vertebral a. & plexus Cervicothoracic (stellate) ganglion Ansa subclavia

HORNER’S SYNDROME Int. carotid a. & plexus SYMPTOMS: 1. MIOSIS (PARALYSIS OF DILATOR PUPILLAE M.) 2. PTOSIS (PARALYSIS OF SUPERIOR TARSAL M.) 3. REDNESS & INCREASED TEMPERATURE OF SKIN (VASODILATION) 4. ANHIDROSIS (SWEAT GLS. CAN’T SECRETE) Sup. cervical ganglion Students should review this material on their own HORNER'S SYNDROME is a series of signs which occur following a lesion to the cervical part of the sympathetic trunk. These signs include 1) miosis (pupillary constriction) 2) ptosis (drooping upper eyelid) 3) anhidrosis (no sweating) and 4) vasodilation (flushing of facial skin). These signs occur on the same side as the lesion. Sympathetic trunk Facial a. & plexus Ext. carotid a. & plexus

LAB PREVIEW

1. REMOVE ALL MUSCULATURE FROM OCCIPITAL BONE & POSTERIOR ARCH OF ATLAS.

2. REMOVE WEDGE OF OCCIPITAL BONE

3. REMOVE POST. ARCH OF ATLAS, TRANSECT & REMOVE CERVICAL SPINAL CORD & ASSOCIATED MENINGES. 4. CUT & REFLECT TECTORIAL MEMBRANE INFERIORLY. 5. CUT ALAR LIGS. & SUP. LONGITUDINAL BAND. 6. DISARTICULATE AO JOINTS W/ HAMMER & CHISEL. Spinous processes and parts of vertebral arches removed: posterior view Basilar part of occipital bone Tectorial membrane Capsule of AO joint Deeper (accessory part) of tectorial membrane Atlas (C1) Posterior longitudinal ligament Capsule of lateral AA joint Alar ligaments Axis (C2) Capsule of zygopophysial joint (C2-C3) Atlas (C1) Superior longitudinal band CRUCIATE LIGAMENT Transverse ligament of atlas Axis(C2) Inferior longitudinal band Deeper (accessory part) of tectorial membrane Principal part of tectorial membrane removed: posterior view

7. CUT PREVERTEBRAL MUSCLES THAT INSERT INTO SKULL.

8. WORK YOUR HANDS INTO RETROPHARYNGEAL SPACE, AND PULL CERVICAL VISCERA AND HEAD FORWARD AWAY FROM VERTEBRAL COLUMN.

END OF LECTURE