Nasopharynx SB Anatomy

8/10/2019 Nasopharynx SB Anatomy

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GENERAL DESCRIPTION OF THE

NASOPHARYNX

The nasopharynx (post-nasal space) is the part of the pharynx posterior to the nasal cavities and above the level of

the junction of the hard and soft palate. The nasopharynx has a roof, floor and walls on its posterior and lateral sides.

The roof and posterior wall merge smoothly and are formed by the mucoperiosteum which lies on the body of the

sphenoid, the basisphenoid and the basiocciput. Inferior to the pharyngeal tubercle, mucosa covers the pharyngobasilar fascia

which lies anterior to the basiocciput, arch of the atlas and body of the axis.

The floor of the nasopharynx is formed anteriorly by the superior surface of the soft palate which is continuouswith the floor of the nasal cavities. Posteriorly, the floor is deficient where the nasopharynx communicates inferiorly with

the oropharynx through the pharyngeal isthmus.

The main feature of the lateral wall is the tubal elevation (torus tubarius, Eustachian cushion) an inverted T -

shaped mucosa-covered prominence created by the pharyngeal projection of the auditory tube (Eustachian tube,

pharyngotympanic tube) (Figure 160.1). Posterior to the tubal elevation is the lateral pharyngeal recess (fossa of

Rosenmiiller) which is formed by the projection of the tubal cartilage into the pharynx. The lateral wall begins at the choana

(posterior nasal aperture), and is formed by mucosa overlying the medial pterygoid plate, the tensor and levator palati

muscles, the tubal elevation and the superior constrictor muscle. The pharyngeal opening of the auditory tube

(pharyngotympanic tube ostium, Eustachian tube opening or orifice) is approximately 1 cm behind the posterior end of the

inferior turbinate. The salpingopharyngeal mucosal fold extends inferiorly from the posterior part of the tubal elevation and

is raised by the salpingopharyngeus muscle. The salpingopalatine mucosal fold extends anteriorly from the anterior part of

the tubal elevation to the superior surface of the palate. The levator palati muscle raises a bulge in the floor of the pharyngeal

opening of the auditory tube.

The nasopharynx communicates anteriorly with the nasal cavities through the choanae, inferiorly with theoropharynx through the pharyngeal isthmus and laterally with the middle ears through the auditory tubes.

LAYERS OF THE NASOPHARYNGEAL WALL

The wall of the nasopharynx consists of four layers. The mucosa of the nasopharyngeal is continuous with that

lining the nasal cavities, the auditory tubes and the oropharynx. The junction between the ectoderm-derived nasal cavity

mucosa and the endoderm-derived nasopharyngeal mucosa varies in its position posterior to the choanae. There are three

types of epithelium in the nasopharynx: columnar, pseudo stratified, ciliated 'respiratory-type' epithelium with goblet cells

and seromucinous glands is found in the region of the choanae, on the roof and upper portion of the posterior wall;

nonkeratinizing, stratified squamous epithelium is found on the lower half of the lateral and posterior walls and is continuous

with that in the oropharynx; an intermediate epithelium of columnar cells with short microvilli instead of cilia lies between

these two zones. A vascular connective tissue layer, the lamina propria, lies immediately beneath the epithelium and contains

mucosa-associated lymphoid tissue and serous and mucous glands.

Lymphoid nodules - the nasopharyngeal tonsil or adenoids - aggregate on the posterior wall of the nasopharynx.

Together with the palatine tonsil and lingual tonsil, they constitute the major part of Waldeyer's ring or nasal-associatedlymphoid tissue and belong to the mucosa-associated lymphoid tissue system. Lymphoid tissue found on the rim of the tubal

elevation, the tubal tonsil (Gerlach's tonsil) and lymphoid nodules that may be present submucosally throughout the

nasopharynx also contribute to Waldeyer's ring.

The submucosa is a strong fibrous layer that lies between the mucosa and muscular layer of the pharynx, and forms

the epimysial covering of the constrictor muscles on their internal surface. The submucosa continues superiorly as the

aponeurosis of the superior constrictor muscle, the pharyngobasilar fascia, and attaches the pharynx to the skull base.

The muscular layer consists of an outer circular muscle layer that is made up of the superior, middle and inferior

constrictors, and an inner longitudinal muscle layer that is formed by the stylopharyngeus, salpingopharyngeus and

palatopharyngeus muscles.

The adventitia is the buccopharyngeal fascia which is a loose connective tissue layer that covers the external surface

of the muscles as their external epimysium and blends with the surrounding fascia.

FASCIAL RELATIONS OF THE NASOPHARYNX

Fascial layers divide the neck into fascial spaces, each of which contains distinct anatomical structures and providespotential pathways for the spread of tumours and infection. The use of cross-sectional imaging of the neck has led to insights

into head and neck anatomy and pathology. Interpretation of these images can precisely locate a lesion, evaluate tumours

and assess the extent of infiltration or infections.

Cervical fascial layers

The fascial layers of the neck, which facilitate movement between neck structures, are divided into the superficial

cervical fascia and the deep cervical fascia.

The superficial cervical fascia is a thin layer of subcutaneous connective tissue that lies between the dermis and

the deep cervical fascia and envelops the platysma and muscles of facial expression.


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The deep cervical fascia consists of the superficial, middle and deep layers.

The superficial layer of deep cervical fascia (investing layer) envelops the sternocleidomastoid and trapezius

muscles and the parotid and submandibular glands. It contributes to the formation of the carotid sheath.

The middle layer of deep cervical fascia (visceral layer) is a thin layer of loose areolar fascia that splits to enclose

the pharynx, oesophagus, larynx, trachea and thyroid gland. It extends from the skull base to the upper mediastinum and

contributes to the formation of the carotid sheath.

A portion of the middle layer of deep cervical fascia that is related to and encloses the pharynx, called the

buccopharYugeal fascia, covers the external surface of the buccinator and superior constrictor muscles. Both these musclesarise from the pterygomandibular raphe and allow the pharynx to move freely, relative to neighbouring structures such as

the carotid sheath and vertebrae. Below the level of the pharynx it is called the visceral fascia.

The deep layer of the deep cervical fascia (prevertebral fascia) comprises of two layers. The prevertebral layer

extends from the base of skull to the coccyx and surrounds the vertebrae and spinal muscles. The alar layer, an anterior

subdivision of the prevertebral fascia, stretches between the transverse processes of the vertebrae and extends from the skull

base to the level of T2 where it fuses with the posterior aspect of the visceral fascia. The deep layer blends with and

contributes to the formation of the carotid sheath

Cervical fascial spaces

The deep fascial spaces are divided into midline spaces and paired lateral spaces. The midline spaces consist of the

pharyngeal mucosal, retropharyngeal and prevertebral spaces, and paired lateral spaces of the parapharyngeal, carotid,

masticator and parotid spaces (Figure 160.3).

The pharyngeal mucosal space (visceral space) encloses the pharynx and is composed of mucosa, submucosa and

pharyngeal constrictors. The buccopharyngeal fascia surrounds most of the space laterally and posteriorly. Superiorly, wherethe muscle is deficient - the sinus of Morgagni - the buccopharyngeal fascia fuses with the pharyngobasilar fascia to form

one layer attaching the pharynx to the skull base.

The retropharyngeal space lies between the buccopharyngeal (visceral) fascia anteriorly and the prevertebral fascia

posteriorly. It lies below the skull base, behind the pharyngeal mucosal space, medial to the carotid spaces and anterior to

the prevertebral space. Anterior to the cervical vertebrae the prevertebral fascia splits into two layers. The anterior

subdivision, the alar fascia, divides the retropharyngeal space into anterior and posterior compartments.

The anterior compartment - the space bordered anteriorly by the buccopharyngeal fascia (middle layer of deep

cervical fascia, visceral layer) and posteriorly by the alar fascia (the anterior layer of the deep layer of deep cervical fascia)

- is the true retropharyngeal space, since it exists between two different layers of deep cervical fascia (an interfascial space).

The retropharyngeal space extends from the skull base to the level of T2, where the alar fascia fuses anteriorly with the

visceral fascia; this space allows movement of the pharynx and larynx during swallowing. The posterior compartment of the

retropharyngeal space is bordered anteriorly by the alar layer of fascia and posteriorly by the prevertebral layer of fascia; it

is, therefore, a space lying within a fascial layer (an intrafascial space). The posterior compartment extends from the skull

base to the diaphragm. These spaces provide pathways for the spread of infection from the neck into the chest. A medianraphe divides the retropharyngeal space into two halves.

The prevertebral space lies posterior to the prevertebral fascia and extends from the skull base to the coccyx.

The parapharyngeal space is the fibrofatty space that lies lateral to the nasopharynx. This space, shaped similarly

to an inverted pyramid, extends from a small area on the temporal bone near the foramen lacerum to the greater cornu of the

hyoid bone. The medial border of the parapharyngeal space is formed by the buccopharyngeal fascia on the external surface

of the superior constrictor, and at a slightly lower level by the fascia on the lateral surface of the tensor and levator palate

muscles. The medial pterygoid muscle, the ramus of the mandible and the deep lobe of the parotid form the lateral border of

the parapharyngeal space. The carotid sheath forms its posterior border. The anterior portion of the parapharyngeal space

lies between the levator and tensor palati medially and the medial pterygoid laterally. A layer of fascia that extends from the

medial pterygoid plate and tensor palati to the spine of the sphenoid and the styloid process loosely divides the

parapharyngeal space anterolaterally (prestyloid parapharyngeal space) from the carotid space posteromedially (poststyloid

parapharyngeal space). The parapharyngeal space is important because of its central location and its relationship to other

spaces in the neck: the pharyngeal mucosal space is medial; the masticator space, anterolateral; the parotid space, lateral;

the carotid space, posterior; and the retropharygeal space, posteromedial.The carotid space (carotid sheath, poststyloid parapharyngeal space) is an enclosed fascial space that extends from

the jugular foramen to the aortic arch. Its medial relation is the lateral aspect of the lateral pharyngeal recess, and is separated

from the lumen of the nasopharynx by the superior constrictor muscle and pharyngobasilar fascia. It lies lateral to the

prevertebral space and the retropharyngeal space, posterior to the parapharyngeal space, and posteromedial to the fascia that

joins the styloid process and muscles to the tensor palati and medial pterygoid plate. Fascia from all three layers of the deep

cervical fascia condense to form the carotid sheath.

The masticator space is bound on all sides by the superficial layer of the deep cervical fascia. It contains the muscles

of mastication - the medial and lateral pterygoids, the masseter and the temporalis. It also contains the ramus of the mandible


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and the mandibular division of the trigeminal nerve. The superomedial portion of the masticator space adjacent to the skull

base is in the infratemporal fossa.

The parotid space lies lateral to the parapharyngeal space, anterior to the carotid space and posterior to the

masticator space. It is bound on all sides by the superficial layer of deep cervical fascia. The masticator and parotid spaces

occupy the infratemporal fossa (Table 160.1).

Fascial space ContentsParapharyngeal Fat, arteries, veins, trigeminal nerve, salivary gland rests,

lymph nodes

Pharyngeal mucosal Mucosa, lymphoid tissue, muscles of the pharynx, minor

salivary glands

Masticator Mandible, muscles, trigeminal nerve

Parotid Parotid gland, facial nerve, lymph

nodes, arteries, veins

Carotid Carotid artery, internal jugular vein, cranial nerves IX-XII,

lymph nodes, sympathetic fibres

Retropharyngeal Fat, lymph nodes

Prevertebral Vertebrae and prevertebral muscles

BONES OF THE NASOPHARYNX

In the midline, the nasopharynx is bounded by the palatine, vomer, sphenoid and occipital bones and by the atlas.

Laterally are the pterygoid processes, sphenoid, temporal and occipital bones.

The choanae are formed by the vomer medially, the body of the sphenoid superiorly, the medial pterygoid plate

laterally and the horizontal plate of the palatine bone inferiorly.

The petrous portion of the temporal bone lies between the greater wing of the sphenoid and the basilar part of the

occipital bone. The levator palati and the cartilaginous portion of the auditory tube attach themselves to the petrous apex.

Posterior to their attachment is the carotid canal and the jugular fossa.The basiocciput, the basilar part of the occipital bone, with the pharyngeal tubercle on its inferior surface, is the

quadrilateral portion of the occipital bone anterior to the foramen magnum. The longus capitis inserts on either side of the

midline of the basiocciput; posterolateral to the insertion lies the rectus capitis. The hypoglossal canal, with the hypoglossal

nerve and the meningeal branch of the ascending pharyngeal artery, is at the anterior base of each occipital condyle.

The sphenoid bone lies anterior to the occipital and temporal bones, and has a body, two greater wings, two lesser

wings and two pterygoid processes. In the midline, the anterior surface of the body articulates with the perpendicular plate

of the ethmoid, and the rostrum of the inferior surface of the body articulates with the alae of the vomer. The posterior

portion of the bodythe basisphenoid - articulates with the basilar part of the occipital bone, the basiocciput, and together

form the clivus. The lateral surface of the greater wing contributes to the infratemporal fossa and gives rise to the attachmen't

of the superior head of the lateral pterygoid muscle.

The pterygoid process of the sphenoid is a perpendicular process that arises from the junction of the body and

greater wing. Each process has a medial and lateral plate that are fused anteriorly, creating the pterygoid fossa. The fossa

contains the medial pterygoid and tensor palati muscles. Cranial to the pterygoid fossa lies the scaphoid fossa which gives

rise to the tensor palati. The anterior surface of the pterygoid process forms the posterior wall of the pterygopalatine fossa.The lateral surface of the lateral pterygoid plate forms the medial wall of the infratemporal fossa and gives rise to

the inferior head of the lateral pterygoid muscle; the medial surface gives rise to the medial pterygoid muscle. At the base

of the lateral pterygoid plate are the foramen ovale (mandibular nerve, accessory meningeal artery) and the foramen spino

sum (middle meningeal vessels).

The medial pterygoid plate articulates with the vertical part of the palatine bone anteriorly and has the pterygoid

hamulus at the lower end, around which the tendon of tensor palati hooks. At the base of the medial pterygoid plate lies the

foramen lacerum, bounded by the sphenoid, petrous portion of the temporal bone and basilar portion of the occipital bone.

The internal carotid artery runs across the cranial aspect of the foramen; lateral to the foramen lies a groove for the auditory

tube. The vertical part of the palatine bone lies between the maxilla and the pterygoid process and forms the posterior part


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of the lateral wall of the nasal cavity. It has a medial nasal surface, which articulates with the inferior and middle turbinates,

and a lateral maxillary surface that faces the pterygopalatine fossa. The posterior free margin of its horizontal part is attached

to the palatine aponeurosis of the tensor palati muscle.

Between the lateral pterygoid plate and the maxilla lies the pterygomaxillary fissure that leads to the pterygopa-

1atine fossa. This small fat-filled triangular space, which lies between the pterygoid process posterolaterally, the maxilla

anterolaterally and palatine bone medially, contains the maxillary nerve, sphenopalatine (pterygopalatine) ganglion and the

terminal branches of the maxillary artery. The pterygopalatine fossa communicates with the choana, the scaphoid fossa, the

nasal cavity, the hard palate, the middle cranial fossa and the orbit.The atlas lacks a body; two lateral masses are connected to each other by anterior and posterior arches. The anterior

margin of the foramen magnum is connected to the upper border of the anterior arch of the atlas by the anterior atlanto-

occipital ligament. Posterior to the anterior arch lies the odontoid process of the axis.

The dens or odontoid, a superior projection of the body of the axis, articulates with the anterior arch of the atlas.

The anterior arch of the atlas is connected to the body of the axis by the anterior atlantoaxial ligament. The ligament is

thickened medially as the superior continuation of the anterior longitudinal ligament of the spine.

MUSCLES OF THE NASOPHARYNX

Pharyngeal musclesThe superior constrictor is a quadrilateral muscle that arises from the lower part of the posterior margin of the

medial pterygoid plate, the hamulus, the pterygomandibular raphe or ligament, the posterior end of the mylohyoid line of

the mandible and the side of the tongue. The fibres of the muscle pass backwards and insert into the median pharyngealraphe, which, in turn, is anchored to the pharyngeal tubercle or spine on the basilar part of the occipital bone by an

aponeurosis. The fibres of the superior constrictor do not reach the skull base but are attached to it by an aponeurosis. The

superior constrictor is a sphincter that prevents reflux into the nasopharynx, and has a peristaltic function during swallowing.

The pharyngobasilar fascia, which lies in the gap between the superior constrictor and the skull base, the sinus of

Morgagni, fuses with the buccopharyngeal fascia to form a single layer of fascia. The auditory tube passes through this gap.

The pharyngobasilar fascia is attached to the pharyngeal tubercle, the basiocciput, the petrous temporal bone medial to the

carotid canal and to the posterior border of the medial pterygoid plate (Figure

160.4).

The palatopharyngeal (velopharyngeal) sphincter is a band of mainly superior constrictor muscle fibres, with some

palatopharyngeus fibres, that arises from the upper surface of the palatine aponeurosis, passes lateral to the levator palati

and blends posteriorly with fibres from the opposite side. The band ridges the pharyngeal wall as Passavant's ridge, which

can be seen when the soft palate is elevated.

The salpingopharyngeus arises from the posterior region of the pharyngeal projection of the auditory tube and

passes inferiorly to blend with the palatopharyngeus and inferior constrictor. It elevates the upper lateral wall of the pharynx.

Prevertebral muscles

The longus capitis arises from the transverse processes of the cervical vertebrae and inserts into the inferior

surface of the basilar part of the occipital bone. It separates the nasopharynx from the lower clivus and vertebrae.

Palatal muscles

The levator palati muscle is situated lateral to the choana, and arises within the pharynx from the inferior surface

of the petrous part of the temporal bone and by a few fibres from the medial lamina of the auditory tube cartilage. It is medial

to the pharyngobasilar fascia. It passes above the upper concave margin of the superior constrictor and then below the floor

of the pharyngeal opening of the auditory tube and is inserted into the palatine aponeurosis. It opens the pharyngeal orifice

of the auditory tube and elevates the soft palate during swallowing.

The tensor palati muscle is situated lateral to the auditory tube and the levator palati. It arises from the scaphoid

fossa at the base of the medial pterygoid plate, the lateral lamina of the auditory tube cartilage and thespine of the sphenoid.

It is lateral to the pharyngobasilar fascia (Figure 160.5). It descends vertically between the medial pterygoid plate and themedial pterygoid muscle and ends as a tendon that hooks around the pterygoid hamulus. The tendon turns medially and

inserts into the palatine aponeurosis. It actively opens the auditory tube and tenses the soft palate during swallowing.

The uvular muscles, intrinsic muscles of the soft palate, arise from the posterior nasal spine of the palatine bones

and the palatine aponeurosis, and insert into the uvula. They stiffen the soft palate.

The palatoglossus arises from the soft palate aponeurosis and passes in front of the palatine tonsil to insert into the

lateral side of the tongue. It acts as a constrictor of the fauces.

The palatopharyngeus arises from the soft palate aponeurosis and the posterior border of hard palate and passes

behind the palatine tonsil to blend with the stylopharyngeus and pharyngeal constrictors. It elevates the pharynx during

swallowing (Figure 160.6).


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Masticator muscles

The lateral pterygoid muscle arises as two heads, one from the greater wing of the sphenoid and the other from the

lateral surface of the lateral pterygoid plate. The fibres pass horizontally backwards and insert into the neck of the mandibular

condyle. It opens the mouth and protrudes the mandible.

The medial pterygoid muscle arises in the pterygoid fossa from the medial surface of the lateral pterygoid plate

and maxillary tuberosity. The fibres pass inferiorly backwards and insert into the medial surface of the ramus and the angle

of the mandible. It closes the mouth.

The auditory tube

The auditory tube runs anteriorly and inferiorly from its bony part in the petrous portion of the temporal bone to

the nasopharynx. The longer cartilaginous part is medial to the foramen ovale and spinosum (which lie in line with the lateral

pterygoid plate), lateral to the foramen lacerum and, more posteriorly, lateral to the carotid canal. The tensor palati separates

the auditory tube from the mandibular nerve. The auditory tube opens near the root of the medial pterygoid plate anterior to

the foramen ovale.

BLOOD VESSELS OF THE NASOPHARYNX

Arteries

The ascending palatine artery, a branch of the facial artery, ascends towards the skull base on the external surface

of the pharynx and then winds medially over the upper border of the superior constrictor muscle. It supplies the levator

palati, the soft palate, the superior constrictor and the auditory tube, and anastomoses with other arteries supplying the

nasopharynx.

The ascending pharyngeal artery, a branch of the external carotid artery, ascends vertically between the carotidsheath and the pharynx to the skull base. It gives off a number of perforators to the superior constrictor muscle, supplying

the lateral and posterior pharyngeal wall above the level of the palate.

The ascending cervical artery arises from the thyrocervical trunk or from the inferior thyroid artery. It winds

upwards behind the carotid sheath and anastomoses with the ascending pharyngeal artery.

The maxillary artery is the larger terminal branch of the external carotid artery. It travels through the substance of

the parotid gland, passes between the ramus of the mandible and the sphenomandibular ligament, passes either deep or

superficial to the lateral pterygoid muscle and enters the pterygopalatine fossa.

The maxillary artery is divided into three parts: mandibular, pterygoid and pterygopalatine. The mandibular part

gives rise to the middle meningeal branch which passes through the foramen spinosum to supply the dura. The pterygoid

part gives rise to pterygoid branches which supply the pterygoid muscles and tensor palati. The pterygopalatine part gives

off four branches in the pterygopalatine fossa: the descending palatine artery that gives rise to the greater and lesser palatine

branches which supply the palate; the artery of the pterygoid canal that supplies the upper pharynx and auditory tube; the

pharyngeal artery that supplies the upper pharynx and auditory tube; and the sphenopalatine artery that supplies the posterior

portion of the nasal cavity.

Veins

A submucosal plexus of veins communicates with an external pharyngeal plexus of veins. Veins corresponding to

all branches of the maxillary artery then drain into the pterygoid plexus, which has deep and superficial components that

communicate with each other. The pterygoid plexus receives tributaries from foramina of the skull base, the masseter and

pterygoid muscles, the pterygopalatine fossa and the cavernous sinus. The main drainage of the pterygoid plexus is into the

internal jugular vein via the maxillary, retromandibular and common facial veins.

LYMPHATICS OF THE NASOPHARYNX

The retropharyngeal space contains two groups of lymph nodes: medial retropharyngeal lymph nodes, which are

often absent in adults, and larger, more constant, lateral retropharyngeal lymph nodes. The lateral group is known as the

nodes of Rouviere.

The first echelon nodes that usually drain the nasopharynx are the retropharyngeal nodes. Lymph from the lateral

wall of the nasopharynx drains either to the lateral retropharyngeal nodes or directly to upper jugular (level lIb) lymph nodes.Lymph from the roof and posterior wall of the nasopharynx usually drains to lateral retropharyngeallymph nodes, but may

occasionally drain directly to upper jugular (level lIb) lymph nodes.

The lymphatic drainage of the nasopharynx is often bilateral, draining to both sides of the neck. Lateral

retropharyngeal lymph nodes usually drain into upper jugular ( especially level lIb) and posterior triangle (especially level

Va) lymph nodes, but may occasionally drain directly into mid-jugular lymph nodes (level IlI),zs The retropharyngeal nodes

also drain lymph from the posterior nasal cavity, the posterior oropharyngeal wall, the soft palate, the pharyngeal tonsil, the

auditory tube and middle ear.


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All lymph from the head and neck eventually drains into the upper, middle and lower jugular groups of deep

cervical lymph nodes. Efferent vessels from these lymph nodes drain into a (lymphatic) jugular trunk, which on the right

joins the junction of the subclavian and internal jugular veins, and on the left joins the thoracic duct.

NERVES OF THE NASOPHARYNX

The motor, sensory and autonomic nerve supply of the pharynx is from the pharyngeal plexus, which is formed

from branches of the glossopharyngeal and vagus nerves and the sympathetic chain. The pharyngeal plexus lies medial to

the buccopharyngeal fascia on the external surface of the constrictor muscles.The pharyngeal plexus supplies motor innervation to all muscles of the pharynx, apart from the stylopharyngeus,

which is supplied by the muscular branch of the glossopharyngeal nerve, and to all muscles of the soft palate except the

tensor palati. The mandibular branch of the trigeminal nerve supplies the tensor palati and lateral and medial pterygoids.

The anterior rami of CI-C3 supplies motor innervation to the longus capitis.

Sensory innervation is from the nasopharyngeal branches of the pharyngeal plexus, pharyngeal branches of the

maxillary nerve and pharyngeal branches of the glossopharyngeal nerve.

Nasopharynx SB Anatomy

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