Nasal and oral cavity

Where are the 2 nasal cavities ?

In the uppermost part of the respiratory tract and contain the olfactory receptors

What are the nasal cavities ?

An elongated wedged shaped with a larger inferior base and a narrow superior apex

What are the anterior apertures ?

The nares —> open into the inferior surface of the nose

What are the posterior apertures ?

The choanae —> open into nasopharynx

Describe the lateral wall of the nasal cavity

1. 3 curved shelves of bone (conchae) which are one above the other and project medially and inferior across the nasal cavity

2. Anterior, medial and posterior margin of conchae are free

3. The conchae divide each nasal cavity into 4 air channels

What are the 4 air channels ?

1. Inferior nasal meatus between inferior concha and nasal floor

2. Middle nasal meatus between the inferior and middle concha

3. Superior nasal meatus between the middle and superior concha

4. Spheno-ethmoidal recess between the superior concha and the nasal roof

Where are the openings of the paranasal sinus?

On the lateral wall and roof of the nasal cavities

—> they are extensions of the nasal cavity that erode into the surrounding bens during childhood and early adulthood

—> The lateral wall also contains the opening of the nasolacrimal duct which drains tears from the eye not the nasal cavity

What is the nasal vestibule ?

It is a small dilated space just internal to the naris that is lined by skin and contains hair follicles

What is the respiratory region?

The largest part of the nasal cavity, it has a rich neuromuscular supply and is lined by respiratory endothelium composed mainly of ciliated and mucous cells

Where is the olfactory region?

It is small, at the apex of each nasal cavity and is lined by olfactory epithelium and contain the olfactory receptors

What do the nasal cavities also do?

They adjust the temperature and humidity of respired air by the action of a rich blood supply and trap and remove particular matter from the airway by filtering air through hair in the vestibule and by capturing foreign material in abundant mucus, the mucus is normally moved posteriorly by cilia on epithelial cells in the nasal cavities and is swallowed

What does the ethmoid bone contribute to ?

The roof, lateral wall and medial wall of both nasal cavities and contain ethmoids cells (ethmoidal sinuses).

Cuboidal overall shaped and is composed of 2 rectangular boxes shaped ethmoidal labyrinths one on each side

By what are the ethmoidal labyrinths united?

By the cribiform plate in the midline by a perforated sheet of bone

What are sheet of bone can we find in a median sagittal plane ?

The perpendicular plate, if descends from the cribiform plate to form part of the nasal septum

By what are the ethmoidal labyrinth composed?

By 2 delicate sheets of bone which sandwich the ethmoids cells

Where is the cribiform plate in the nasal cavity ?

At the apex of the nasal cavities and fill the ethnical notch in the frontal bone and separates the nasal cavitY below from the cranial cavity above

Through which do olfactory nerves and fibers pass?

Through small perforations in the bone

What is the crista galli?

It is a large triangular process at the midline on the superior surface of the cribiform plate anchors a fold of dura mater in the cranial

What does the perpendicular plate of the ethmoid bone form ?

Forms the upper part of the medial nasal septum

Describe the bony parts of the external nose

• Nasal bones are part of the maxillae and frontal bones provide support

• Anteriorly and on each side support is provided by lateral processes of the septal cartilage, major alar, 3-4 minor alar cartilages and a single septal cartilage in the midline that forms the anterior nasal septum

How many paranasal sinuses are there?

4 - named according to the bone in which it is found, they develop as outgrowths from the nasal cavities and erode into the surrounding bones

What are the 4 paranasal sinuses?

Ethmoidal cells, sphenoid, maxillary and frontal sinuses

Describe the frontal sinus

• one on each side

• most superior one

• triangular in shape

• part of the frontal bone under the forehead

• the base of each is oriented vertically in the bone at the midline above the bridge of the nose and the apex is laterally one third of the way along the upper margin of the orbit

  —> each one drains onto the lateral wall of the middle meatus via the frontonasal duct

Describe the frontonasal duct

Penetrates the ethmoidal labyrinth and continues as the ethmoidal infundibulum at the frontal end of the semilunar hiatus

Describe the ethmoidal cells

• On each side

• fill the ethmoidal labyrinth

• each cluster of cells is separated from the orbit by the thin orbital plate of the ethmoidal labyrinth and from the nasal cavity by the medial wall of the ethmoidal labyrinth

• Formed by a variable number of individual air chambers which are divided into anterior, middle and posterior ethmoidal cells based on the location of their apertures on the lateral wall of the nasal cavity

Describe the maxillary sinus

• one on each side

• largest of the paranasal sinuses

• completely fils the bodies of the maxillae

• pyramidal shape

• with the apex directed laterally and

• the base deep to the lateral wall of the adjacent nasal cavity

• medial wall is formed by the maxilla and by parts of the inferior concha and palatine bone that overlie the maxillary hiatus

Describe the sphenoidal sinus

• one on either side within the body of the sphenoid

• open into the roof of the nasal cavity via apertures on the posterior wall

• are high on the anterior walls of the sphenoidal sinuses, are related

1. Above to the cranial cavity (pituitary gland and to the optic chiasm)

2. Laterally to the cranial cavity particularly to the cavernous sinuses

3. Below and in front to the nasal cavities

Describe the medial wall of the nose

• mucosa covered surface of the thin nasal septum

• is oriented vertically in the medial sagittal plane and separates the right and left nasal cavities

What does the nasal septum consist of ?

1. Anteriorly the septal nasal cartilage

2. Posteriorly the vomer and the perpendicular plate of the ethmoid bone

3. Contributions by the nasal bones where they meet tin the midline and the nasal spine of the frontal bone

4. Contributions by the nasal crests of the maxillary and palatine bones rostrum of the sphenoid bone and the incisor crest of the maxilla

What does the floor of the nose consist of ?

Smooth, concave and much wider than the roof

• Consist of:

1. Soft tissue of the external nose

2. Upper surface of the palatine process of the maxilla and the horizontal plate of the palatine bone which h together form the hard palate

—> the naris open anteriorly into the floor and the superior aperture of the incisive canal is deep to the mucosa immediately lateral to the septum near the front of the hard palate

Describe the roof of the nose

• Narrow and highest in central region where it is formed by the cribiform plate

• Anteriorly to the cribiform plate the roof slopes inferiorly to the nares and is formed by:

1. Nasal spine of the frontal bone and the nasal bones

2. Lateral processes of the septal cartilage and major alar cartilages of the external nose

• Posteriorly the roof of each cavity slopes inferiorly to the chin and is formed by:

1. Anterior surface of the sphenoid

2. Ala of the vomer and adjacent sphenoidal processes of the palatine bone

3. The vaginal process of the medial plate of the pterygoid process

By what is the roof perforated?

Superiorly by openings in the cribiform plate and anteriorly to these by a separate foramen for the anterior ethmoidal nerve and vessels

Describe the lateral wall of the nose (bones)

• Complex and is formed by bone, cartilage and soft tissue

• Bony support comes from: ethmoidal labyrinth and uncinate process, perpendicular plate of palatine bone, medial plate of pterygoid process of the sphenoid, medial surfaces of the lacrimal bones and maxillae and inferior concha bone

Describe the lateral wall of the external nose

• Supported by cartilage and by soft tissue

• The surface is irregular in contour and is interrupted by the 3 nasal conchae

What do the 3 nasal conchae do ?

They separate into 4 air channels:

1. Inferior

2. Middle

3. Superior meatus

4. A spheno-ethmoidal recess

Describe the medial wall of the middle meatus

• Elevates to form the dome shaped ethmoidal bulla

• that is formed by the underlying middle ethmoidal cells which expand the medial wall of the ethmoidal labyrinth

Where is the semilunar hiatus and by what is it formed?

Inferior to the ethmoidal bulla

Formed by the mucosa covering the lateral wall as it spans a defect in the bony wall between the ethmoidal bulla above and the uncinate process below

What does the semilunar hiatus form?

The anterior end of it forms a channel (ethmoidal infundibulum) which curves upward and continues as the front-nasal duct through the anterior part of the ethmoidal labyrinth to open into the frontal sinus

—> The nasolacrimal duct and most of the paranasal sinuses open onto the lateral wall of the nasal cavity

What are the nares ?

• Oval apertures on the inferior aspect of the external nose

• Anterior openings of the nasal cavities

• Held open by the surrounding alar cartilage and septal cartilage and by the inferior nasal spine and adjacent margins of the maxillae

• Always open and can be widened further by the action of the related muscles of facial expression

What are choanae?

• Oval shaped openings between the nasal cavities and the nasopharynx

• Rigid openings completely surrounded by bone and their margins are formed:

1. Inferiorly by the posterior border of the horizontal plate of the palatine bones

2. Laterally by the posterior margin of the medal plate of the pterygoid process

3. Medially by the posterior border of the vomer

Roof:

1. Anteriorly by the ala of the vomer and the vaginal process of the medial plate of the pterygoid process

2. Posteriorly by the body of the sphenoid

Describe the cribiform plate

• Fibers of the olfactory nerve exit the nasal cavity and enter the cranial cavity through perforations in the cribiform plate

• Small foramina between cribiform plate and surrounding bone allow the anterior ethmoidal nerve a branch of the ophthalmic nerve and accompany gin vessels to pass from the orbit into the cranial cavity and then dow into the nasal cavity

Describe he sphenopalatine foramen

• Posterolateral wall of superior nasa meatus

• Superior to the attachment of the posterior end of the middle nasal concha and is formed by the sphenopalatine notch in the palatine bone

• Route of communication between the nasal cavity and the pterygopalatine fossa

What are major structures through the sphenopalatine foramen ?

1. Sphenopalatine branch of the maxillary artery

2. Nasopalatine branch of the maxillary nerve

3. Superior nasal branches of the maxillary nerve

Describe the incisive canal

• In the floor

• Lateral to the nasal septum and just posterosuperior to the root of the central incisor in the maxilla

• 2 canals one on each side both open up into the single unpaired incisive fossa in the roof of the oral cavity

What does the incisive canal transmit ?

1. The nasopalatine nerve from the nasal cavity into the oral cavity

2. The terminal end of the greater palatine artery from the oral cavity into the nasal cavity

Describe the small foramina in the lateral wall

Internal nasal branches of the infra orbital nerve of the maxillary nerve and alar branches of the nasal artery from the facial artery loop around the margin of the naris to gain entry to the lateral wall of the nasal cavity from the face.

Inferior nasal branches from the greater palatine branch of the maxillary nerve enter the lateral wall of the nasal cavity from the palatine canal by passing through small foramina on the lateral wall

What vessels originating from the external carotid artery supply the nose?

Sphenopalatine, greater palatine, superior labial and lateral nasal artery

What vessels originating from the internal carotid artery supply the nose?

Anterior and posterior ethmoidal arteries

What are the veins of the nose?

Veins that pass with branches that ultimately originate from the maxillary artery drain into the pterygoid plexus of veins in the infratemporal fossa, veins from the anterior regions of the nasal cavities join the facial vein

What do parasympathetic fibers innervate?

Secretomotor innervation of mucous glands in the nasal cavities and paranasal sinus

—> The fibers are from the facial nerve which mainly joins branches of the maxillary nerve in the pterygopalatine fossa

From what is the olfactory nerve composed ?

Composed of axons from receptors in the olfactory epithelium at the top of each nasal cavity

What are branches from the ophthalmic nerve ?

1. Anterior and posterior ethmoidal nerves —> originate from the nasociliary nerve in the orbit

Describe the anterior ethmoidal nerve

• Travels with the anterior ethmoidal artery

• Supplies the adjacent ethmoidal cells and frontal sinus and then enters the cranial cavity immediately lateral and superior to the cribiform plate

Describe the posterior ethmoidal nerve

• Supplies the mucosa of the ethmoidal cells and sphenoidal sinus and normally does not extend into the nasal cavity itself

Describe branches from the maxillary nerve

• Many branches that originate in the pterygopalatine fossa and these are

1. Posterior, superior, lateral, inferior nasal nerves

2. Nasopalatine nerve

Describe parasympathetic innervation

• Preganglionic parasympathetic fibers carried in the greater petrosal branch of the facial nerve

• These fibers enter the pterygopalatine fossa and synapse in the pterygopalatine ganglion

• These fibers then join branches of the maxillary nerve to leave the fossa and ultimately reach target glands

Describe sympathetic innervation

• Involved in regulating blood flow in the nasal mucosa

• From spinal cord level T1

• Preganglionic sympathetic fibers enter the sympathetic trunk and ascend to synapse in the superior cervical sympathetic ganglion

• Postganglionic sympathetic fibers pass onto the internal carotid artery enter the cranial cavity and then leaves the internal carotid to from the deep petrosal nerve

• This joins the greater petrosal nerve of the facial nerve and enter the pterygopalatine fossa

• Follow branches of the maxillary nerve into the nasal cavity

Describe the lymphatics of the nose

Lymph from the anterior regions of the nasal cavities, drains forward onto the face by passing around the margins of the nares

—> these ultimately connect with the submandibular nodes

Lymph from the posterior regions of the nasal cavity and the paranasal sinuses drains into the upper deep cervical nodes, some of this lymph passesfirts through the retropharyngeal nodes

Where is the oral cavity ?

Inferior to the nasal cavity

What does the roof of the oral cavity consist of ?

The hard palate and soft palate

• Mainly formed of soft tissue which includes a muscular diaphragm and the tongue

What do the lateral walls of the oral cavity consist of ?

• Cheeks

• Muscular and merge anteriorly with the lips surrounding the oral fissure

Describe the posterior aperture of the oral fissure

• Is the oropharyngeal isthmus

• Opens into the oral part of the pharynx

• Separated into 2 regions by the upper and lower dental arches consisting of the teeth and alveolar bone that supports them

1. Outer oral vestibule

2. Inner oral cavity

Describe the outer oral vestibule

• Horseshoe shaped

• Between the dental arches and the deep surfaces of the cheeks and lips

• Oral fissure opens into it and can be opened and closed by muscles of facial expression and by movements of the lower jaw

Describe the inner oral cavity

• Proper is enclosed by the dental arches

The degree of separation between the upper and lower dental arches is established by what ?

By elevating or depressing the lower jaw (mandible) at temporomandibular joint

Describe the oropharyngeal isthmus

• At the back of the oral cavity proper

• Can be opened and closed by surrounding soft tissues which include soft palate and tongue

What are the functions of the oral cavity ?

1. Inlet for digestive system involved with the initial processing of food, which is aided by secretions from salivary gland

2. Manipulates sounds produced by the larynx and one outcome of this speech

3. Can be used for breathing because it opens into the pharynx which is a common pathway for food and air

To what does the maxilla contribute ?

To the roof of the oral cavity

—> parts involved are alveolar and palatine processes

Describe the palatine process of the maxillae

• Horizontal shelf that projects for the medial surface of the maxilla

• originates superior to the medial aspect of the alveolar and extends to the midline where it is joined at a suture with the palatine process from the anterior 2/3 of the hard palate

• We find a small single fossa just behind the incisor teeth

• 2 incisor canals extend posterosuperiorly from the roof of this fossa to open onto the floor of the nasal cavity

—> The canal and fossae allow passage of the greater palatine vessels and the nasopalatine nerves

To what do the palatine bones contribute ?

The parts of the L-shaped bone contribute to the roof of the oral cavity are the horizontal plate and the pyramidal process

Where is the horizontal plate of the palatine bone?

Projects medially from the inferior aspect of the palatine bone and is joined superiorly by sutures to its partner in the midline and on the same side with the palatine process of the maxilla anteriorly

—> A single posterior nasal spine is formed at the midline where the 2 horizontal plates join and project backward from the margin of the hard palate

Posterior margin of the horizontal plates and the posterior nasal spine are associated with attachments of the soft palate

Pyramidal process projects posteriorly and fills the space between the inferior ends of the medial and lateral plates of the pterygoid process of the sphenoid

Describe the role of the sphenoid bone

• The pterygoid processes and spines are associated with structures related to the soft palate which forms part of the roof of the oral cavity

Describe the pterygoid process of the sphenoid bone

• Descends one on each side from the lateral aspect of the body of the sphenoid each process has a medial and lateral plate

• These two vertically oriented plates project from the posterior aspect of the process

• The v-shaped gap that occurs inferiorly between the 2 plates is filled by the pyramidal process of the palatine bone

What do we also find on the sphenoid bone ?

Hook-shaped structure - pterygoid hamulus

• Behind the alveolar arch and inferior to the posterior margin of the hard palate

What is the pterygoid hamulus ?

1. A pulley for one of the muscles of the soft palate

2. The attachment site for the upper end of the pterygomandibular raphe, which is attached below to the mandible and joins together the superior constrictor of the pharynx and the buccinator muscle of the cheek

What do we find on the pterygoid process ?

A small canoe-shaped fossa (scaphoid fossa)

—> this is for the attachment of one of the muscles of the soft palate

What are the spines of the sphenoid?

Vertical projections from the inferior surface of the greater wings of the sphenoid

• Each one is immediately posteromedial to the foramen spinosum

• The medial aspect of the spine provides attachment for the most lateral part of the tensor veli palatini muscle of the soft palate

What parts of the temporal bone are important ?

The styloid process and the inferior aspect of the petrous party of the temporal bone

• Provide attachment for the muscles associated with the tongue and soft palate

Describe the styloid process

• Projects anteroinferiorly from the underside of the temporal bone

• Points towards the lesser horn of the hyoid bone to which it is attached by the stylohyoid ligament

• The root of the styloid process is anterior to the stylomastoid foramen and lateral to the jugular foramen

• The styloglossus muscle of the tongue attaches to the anterolateral surface of the styloid process

• The inferior part of the temporal bone has a triangular roughened area immediately anteromedial to the opening of the carotid canal —> levator veli palatini attached here

What is the pharyngotympanic tube ?

Its trumpet shaped cartilaginous part is in the groove between the anterior margin of the petrous part of the temporal bone and the posterior margin of the greater wing of the sphenoid bone

• Medial and lateral wall formed mainly by cartilage by cartilage whereas the more inferolateral wall is fibrous and is known as the membranous lamina

What can we find on the internal part of the mandible ?

2 pair of small spines, one pair immediately above the other pair

1. Superior mental spine

2. Inferior mental spine

What are the spines useful for ?

Attachment sites for a pair of muscles that pass into the tongue and a part of muscles thqt connects the mandible to the hyoid bone W

Where is the mylohyoid line?

Extending from the midline and originating inferior to the mental spine

• Raised line or ridge

• Runs posteriorly and superiorly along the internal surface of each side of the body of the mandible to end just below the level of the last moral tooth

Where is the sublingual fossa ?

Above the anterior one third off the mylohyoid line

• Shallow depression

Where is the submandibular fossa ?

Below the posterior 2/3 of the mylohyoid line

• Depression

• Between the last molar of the mylohyoid line is a shallow groove for the lingual nerve

Where is the retromolar triangle ?

Posterior to the last molar tooth on the medial upper surface of the body of the mandible

• Small triangular depression

• The pterygomandibular raphe attaches just medial to the apex of this triangle and extends from here to the tip of the pterygoid hamulus above

What does the mandibular foramen transmit ?

The inferior alveolar nerve and vessels

Where is the hyoid bone ?

between the larynx and mandible

• small U shaped bone

• has an anterior border of the hyoid bone and 2 larger greater horns one on each side (project posterior and superiorly from the body)

• 2 small conical lesser horns on the superior surface where the greater horns join with the body

Where does the stylohyoid ligament attach to?

To the apices of the lesser horns

Why is the hyoid bone important ?

• Connects the floor of the oral cavity in front with the pharynx behind and larynx below

What is the muscular diaphragm ?

It fills the U-shaped gap between the left and right sides of the body of the mandible and is composed of the paired mylohyoid muscles

Where are the geniohyoid muscles ?

Above the diaphragm which run from the mandible in front of the hyoid bone behind

Where is the tongue ?

Superior to the geniohyoid muscle

What is the tongue and what does it form ?

• Muscular structure

• Forms part of the floor and part of the anterior wall of the oropharynx

• Anterior part is in the oral cavity and triangular in shape with a blunt apex of tongue

• Apex is directed anteriorly and sits immediately behind the incisor teeth

• The roof is attached to the mandible and the hyoid bone

• Superior surface of the oral or anterior 2/3 of tongue is oriented in the horizontal plane

• The pharyngeal surface or 1/3 of the tongue curves inferiorly and become oriented more in a vertical plane

By what are the surfaces of the tongue separated ?

By a V-shaped terminal sulcus of tongue

• This sulcus formed the inferior margin of the oropharyngeal isthmus between the oral and pharyngeal cavities

What can we find at the apex of the v-shaped sulcus ?

A small depression - foramen cecum of tongue

• Marks the site in the embryo where the epithelium invaginated to form the thyroid gland

Describe the filiform papillae

• Small cone shaped projections of the mucosa that end in one or more points

Describe the fungiform papillae

• Rounder in shape and larger than filiform ones

• Concentrated along the margins of the tongue

Describe the vallate papillae

• Largest ones

• blunt ended cylindrical papillae invaginations in the tongue surface

• only about 8-12 ones in a single V-shaped line immediately anterior to the terminal sulcus of tongue

What do the papillae do?

They increase the area of contact between the surface of the tongue and the contents of the oral cavity

—> All except the filiform papillae have taste buds on their surfaces