Oral, Nasal and Pharyngeal Structure and Function

Question 1

Describe the skeleton of the external nose

Answer 1

From superior to inferior, the bones and cartilage that comprise the nasal skeleton include the:

1. Frontal bone
2. Nasal bones (paired)
3. Septal cartilage
4. Alar cartilages (paired)
5. Maxilla (frontal process)

(insert image from notes)

Question 2

Describe the skeleton and boundaries of the nasal cavity

Answer 2

Lateral wall of the nasal cavity:

• Alar cartilage
• Lateral cartilage
• Nasal bone
• Ethmoidal bone
• Sphenoidal bone
• Palatine bone
• Maxilla

Medial wall of the nasal cavity

• Alar cartilage
• Septal cartilage
• Cribiform plate of ethmoid bone
• Vomer bone
• Maxilla

(insert images from notes)

Question 3

Discuss the implcations of the ethmoid bone becoming endangered during severe breaks of the nose

Answer 3

The ethmoid bone is very close in proximity to the brain; severe breaks of the nose can endager the brain and meninges directly opposed to the bone.

Particular complications include:

1. Infection of the brain
2. Bleeding of/into the meninges
3. Rhinorrhea (leakage of CSF into the nose)

Question 4

Discuss the structures and features of the medial wall of the nasal cavity

Answer 4

Features of the medial wall include:

1. Vestibule
   * skin and hair at the entrance of the nasal cavity
2. Highly vascular mucous membrane

• lines the all of the nasal cavity except the vestibule (which is skin and hair)
• mucous humidifies and traps foreign particles
• most nose bleeds occur as a result of damage to this highly vascular surface

3. Olfactory area

• situated at the superior border of the cavity
• lined by olfactory epithelium that contains afferent sensory nerves of the olfactory cranial nerve

4. Respiratory area
   * comprised of ciliated respiratory epithelium that facilitate the process of expectoration (muco-cliary elevator)
5. Nasal septum
   * wall that divides the left and right nasal cavities.

Question 5

Describe the features of the lateral wall of the nasal cavity

Answer 5

Features of the lateral nasal cavity wall include:

1. Turbinate Bones

• thin, folded bones that project into the nasal cavity from the lateral -> producing concha
  
  • ​superior, middle and inferior conchae
• lined by highly vascular mucosal membrane
• produce turbulance to warm and humidify incoming air before passing to the lower airways
• inflammation of the concha causes congestion and blockage of the nose

2. Vestibule
   * skin and hair around the entry to the nasal cavity

Question 6

What are the **meatuses **of the nasal cavity?

What are paranasal sinuses?

Answer 6

The meatuses of the nasal cavity represent the space between the conchi and the lateral nasal cavity wall.

The meastuses have communications to other areas - namely the paranasal sinuses.

The paranasal sinuses develop as outpouchings of the nasal cavity -> carrying respiratory epithelium with them ( thus have sensory functions) that is relevant to sinus pathologies.

Question 7

What are the four main paranasal sinuses?

Describe any important structures or functions of them.

What are their innervations?

Answer 7

The main paranasal sinuses are the:

• Frontal sinus
• Ethmoid sinus
• Sphenoid sinus
• Maxillary sinus

The maxillary sinus is important in pathology due to the relative position of the opening (from the middle meatus) into the sinus being positioned superiorly.

• Often drainage of nasal fluid into the maxillary sinus
• Difficult to drain the maxillary sinus to clear it due to gravity - medical intervention in the form of aspiration required in certain cases

The other sinuses are less problematic as they more readily drain with gravity.

The frontal, ethmoid and sphenoid sinuses recieive innervation from the V1 branch of the trigeminal nerve

The maxillary sinus recieves innervation from the V2 branch of the trigeminal nerve.

Question 8

Where does the nasolacrimal duct enter the nasal cavity?

Answer 8

The oriface of the nasolacrimal duct is positioned within the inferior meatus of nasal cavity.

The nasolacrimal duct connects the lacrimal gland (superior to the orbit) to the nasal cavity.

The purpose of this duct is to remove excess tear production (when someone is crying they tend to get a runny nose)

Question 9

Describe the arterial supply of the nasal cavity!

Answer 9

The blood supply of the nasal cavity can be divided into quadrants (where both the lateral and septal walls of the nasal cavity - except the anterior quadrant)

Posterior Quadrant = Sphenopalatine artery

Superior Quadrant = Anterior + Posterior Ethmoidal Arteries

Inferior Quadrant = Greater Palantine Artery

Anterior Quadrant = where the lateral and septal wall of the nasal cavity have different arterial supplies:

• Septal wall: Superior labial arteries
• Lateral wall: Lateral nasal branches of the facial artery

Question 10

Discuss the nerve supply of the nasal cavity

Answer 10

The nerve supply of the nasal cavity is divided into two halves:

Anterosuperior half: Branches of ethmoidal nerves (V1)

Posteroinferior half:

Lateral Wall: Branches of greater and lesser palatine nerves (V2)

Septal Wall: Nasopalantine nerve (V2)

Question 11

Describe the structure of the pharynx

Answer 11

The pharynx is the continuation of the nasal and oral cavities to the larynx.

The pharynx spans from the inferior border of the skull to the C6/Lower border of the cricoid cartilage.

There are three sub-regions of the larynx:

Nasopharynx, Oropharynx and Laryngopharynx

The posterior border of the larynx is formed by a series or sling of constrictor muscles to close off the pharynx. These constrictor muslces contract sequentially on swallowing to propell contents. These constrictor muscles meet their paired contralateral equivalent in the midline Median of Raphe.

The constrictor muscles include: Superior, Middle and Inferior Constrictor Muscles

Question 12

Describe structures present in the nasopharynx

Answer 12

Superficially:

• Opening of the auditory tube
  
  • ​Communicates with the middle ear - facilitates the equalisation of pressure in the middle ear so as too not damage the tympanic membrane
• Tubal elevation (structural protruberance around opening of the auditory tube)
• Pharyngeal tonsil
  
  • ​Aggregations of lymphoid tissue susceptible to inflammation
• **Salpingopharyngeal fold **
• Uvula

Deep:

• Cartilagenous Auditory Tube
• Salpingopharyngeus Muscle
  
  • ​a muscle contracted to alter the area around the auditory tube - this can unblock any occlusions in the auditory tube so that middle ear equalisation can be achieved.

Question 13

What structures contribute to the formation of the roof of the mouth?

Answer 13

From anterior to posterior:

1. Alveolar arches
2. Palatine process of maxilla
3. Horizontal process of palatine bone
4. Soft palate
5. Uvula

Question 14

What structures contribute to the floor of the mouth?

Answer 14

The mylohyoid muscle is a diaphragmatic muscle that forms the diaphragm that is the floor of the mouth.

This floor provides points of attachment for a number of other muscles - particularly muscles of the tongue and the digastric muscle

The geniohyoid muscle lies on top/superior to the mylohyoid muscle (floor) - it spans from the hyoid bone to the mandible

Question 15

Describe the surface anatomy of the tongue

Answer 15

The tongue can be divided into an anterior 2/3rd that sits within the oral cavity and posterior 1/3rd that sits in the oropharynx cavity.

The sulcus terminalis is a ‘v-shaped’ depression at the interfact between the anterior and posterior parts of the tongue. It also demarcates the beginning of the lingual tonsils posterior to it beneath the surface mucosa.

At the apex of the sulcus terminalis is the foramen caecum. This is a reminant of the duct of the thyroid gland. The thyroid gland develops as a diverticulum that invaginated/outpouched from the tongue. The foramen caecum is where this diverticulum closes off.

Papillae are small groove in the mucosa that increase the surface area of the tongue to facilitate better taste and secretion. There are three types of papillae on the surface of the tongue:

1. Fungiform papillae

• round and small in shape, they occupy the majority of the anterior 2/3 of the tongue

2. Foliate Papillae

• linear grooves positioned laterally on the tongue at the interface between anterior and posterior tongue

3. Valate papillae

• 8 to 12 vallate papillae in a single V-shaped line immediately anterior to the terminal sulcus of the tongue - these are the largest papillae

The tongue also gives rise to the palatoglossal arch ( anterior arch formed by mucosa overlying the palatoglossal muscle) and palatopharyngeal arch (posterior arch formed by mucosa overlying palatopharyngeus muscle)

Question 16

Discuss the position, function and innervation of the extrinsic muscles of the tongue!

Answer 16

The extrinsic muscles of the tongue are responsible for altering the position of the tongue.

Each of the muscles are in pairs (L&R)

Genioglosis = protrudes the tongue forward

• deficiencies lead to a deviated tongue towards the side of deficiency

Styolglossus = retracts the tongue

Palatoglossus = elevates the tongue

Hyoglossus = depresses the tongue

All of the extrinsic muscles of the tongue are innervated by hypoglossal nerve** (CN XII) - except for palatoglossus which is supplied by the pharyngeal branch of **vagus nerve.

Question 17

What is the function of the internal muscles of the tongue and what innervates them?

Answer 17

The intrinsic muscles of the tongue are responsible for altering the shape fo the tongue

They are innervated by the hypoglossal nerve (CN XII)

Question 18

Discuss the sensory innervation of the tongue

Answer 18

Anterior 2/3

• General sensory = CN V / Trigeminal Nerve - lingual branch of mandibular division
• Special sensory = **CN VII / Facial Nerve **- chorda tympani branch

Posterior 1/3

• General sensory = Glossopharyngeal Nerve
• Special Sensory = Glossopharyngeal Nerve

Question 19

Discuss the arrangement of teeth within the oral cavity.

Discuss the sensory innervation of teeth and related pathology

Answer 19

There are 16 teeth arranged within each alveolar arch (maxilla and mandibular arches)

• 4x incisors
• 2x canine
• 4x premolars
• 6x molars

Teeth of the maxillary alveolar arch is innervated by the superior alveolar nerve (trigeminal maxillary nerve)

• Upper teeth will commonly refer pain to other V2 structures such as the maxillary sinuses and vice versa.

Teeth of the mandibular alveolar arch are innervated by the inferior alveolar nerve (mandibular division of trigeminal nerve)

• Lower teeth wil commonly refer pain to V3 structures such as the middle ear and vice versa.

Wisdom teeth (3rd molars) are the last teeth to erupt at around 18 y.o

Question 20

Explain the structure and function of the salivary glands of the face.

Answer 20

The salivary glands include:

Parotid Gland

• Large, superficial gland overlying the ramus of the mandible & anterior to sternocleidomastoid.
• Gives parotid duct that passes anteriorly over the masseter muscle before penetrating buccinator muscle to enter oral cavity. Enters oral cavity in the vestibule (space between lip and gum) adjacent to the second molar.

Submandibular gland

• Has two parts: internal and external (to the oral cavity)
• Two parts are divided by the mylohyoid muscle forming the oral cavity floor
• The two parts are continuous by wrapping around the free edge of mylohyoid muscle laterally.
• Submandibular duct passes forward to open on the summit of a small sublingual papillae beside the base of the frenulum of the tongue

Sublingual Gland

• smallest salivatory glands
• sit laterally to the tongue in the oral cavity
• have direct openings to the mucosa of the mouth

Question 21

What other structures of note are present in the floor of the mouth?

Answer 21

A dense network of lingual arteries and veins provide well developed vasculature - important in sublingual drug absorption that is rapid (e.g. GTN)

The hyoglossus muscle takes insertion from the floor of the mouth

Lingual nerve travels alongside the floor of the mouth.

The hypoglossal nerve runs along the floor of the mouth.

Question 22

What are the boundaries of the oropharynx?

Answer 22

All structures posterior to the alveolar arches are considered part of the oropharynx

Question 23

What structures are located within the oropharynx?

Answer 23

Strucutres include:

• Palatoglossal arch (anterior arch)
  
  • mucosa overlying the palatoglossal muslce
• Palatopharyngeal arch (posterior arch)
  
  • mucosa overlying the palatopharyngeal muscle
• Palatine tonsil
  
  • located between the two oropharynx arches
  • can become chronically inflammed and are generally removed
  • thought to play a role in priming the immune system early in development
• Uvula
  
  • posterior apex of the soft palate that contributes to sealing off the nasal cavity during swallowing, coughing and sucking.
• Epiglottis
• Superior constrictor
  
  • underlying constrictor muscle enclosing the posterior aspect of the oropharynx

Question 24

What structures contribute to the soft palate?

What is the purpose of the soft palate?

Answer 24

The soft palate is important in sealing either the nasal or oral cavities off from the pharynx during specific actions:

It seals the nasal cavity during swallowing, coughing and sucking

Seals the oral cavity to allow unimpeded breathing during chewing

View the image attached to view the structures associated

Question 25

What are the five muscles involved in the movement and support of the soft palate?

Answer 25

1. Tensor veli palatini 2. Levator veli palatini 3. Musculus uvulae 4. Palatoglossus 5. Palatopharyngeus All of the muscles are innervated by the pharygeal branch of the **Vagus Nerve (CN X)** except for **tensor veli palatinni (CN V)**

Question 26

What is meant by Waldeyer's Ring?

Answer 26

Waldeyer's Ring refers to the incomplete ring of lymphoid tissue that is organised around the oro- and naso-pharynx. It includes the pharyngeal, tubal, palatine and lingual lymphoid tissues

Question 27

Describe the boundaries of the larynx

Answer 27

The larynx is a series of cartilages at the rostral aspect of the airways; superior to the trachea. Its boundaries extend from the epiglottis to the inferior border fo the cricoid cartilage (or C6)

Question 28

Provide an overview of the laryngeal skeleton

Answer 28

**Hyoid bone** provides attachment to inferior strucutres; ensuring continuity with the head/skull/oral cavity. Connected to thyroid cartilage inferiorly via the **thyrohoid membrane** **Thyroid cartilage** contains the vocal ligaments and is open posteriorly. It articulates inferiorly via **cricothyroid ligament/membrane** from its inferior horn to the **cricoid cartilage below.** **Cricoid cartilage** is closed posteriorly and deficient anteriorly. It gives rise to the arytenoid cartilages that take attachment from the vocal cords. The **epiglottis** originates from the internal angle of the thyroid cartilage and projects upwards posterior to the tongue. Boluses of food push the epiglottis down to prevent food from entering the airways - deflecting it into the oesophagus

Question 29

Describe the cricoid and arytenoid arches

Answer 29

A pair of **arytenoid cartilages** articulate with the posterior aspect of the cricoid cartilage. These arytenoid cartilages are mobile - they 1) **swivel** and can 2) **slide closer or further away from one-another.** The arytenoid cartilages have two types of processes on them for attachment: **vocal processes**: vocal ligaments attach to these processes to induce phonation **muscular processes**: intrinsic muscles of the larynx attach to these muscular processes in order to rotate and swivel the arytenoid cartilages to alter phonation.

Question 30

Discuss the structures of the vocal ligament

Answer 30

The **vocal ligament** takes origin from the internal surface of the anterior **thyroid cartilage** and insert on the vocal processes of the **arytenoid cartilages.** A mucosal layer encapsulates the ligaments known as a vocal fold; and it is continuous with the mucosa that overlies the cartilages and bones of the larynx and respiratory system. There is a **true vocal fold **which is the vocal ligament fold involved in phonation; but also a **false vestibular fold **that has no role in phonation but protects the true vocal fold. The **true vocal fold **is located inferior to the false vocal cord. Vocal ligaments need to be **adducted for phonation **and **abbducted for inhalation/breathing. ** Intrinsic muscles of the larynx alter the position of the vocal ligaments

Question 31

What are the intrinsic muscles of the larynx? What are their effects on the vocal cords?

Answer 31

See the images attached

Question 32

Outline the nerve supply of the larynx!

Answer 32

The **superior laryngeal nerve **splits into the **internal laryngeal nerve **and **external laryngeal nerve.** The **internal laryngeal nerve **provides sensory innervation to the mucosa of the larynx above the vocal fold The **external laryngeal nerve** provides motor innervation to the **cricothyroid muscle** * Deficiencies to the cricothyroid muscle innervation results in an inability to relax the vocal cords -\> high pitched phonation results The **recurrent laryngeal nerve** provides the terminal **inferior laryngeal branch **that innervates **all intrinsic muscles** of the larynx _except for cricothyroid muscle_ and sensation of mucosa below the vocal fold * Damage to this nerve causes the vocal cord to sit in a halfway position on the affected side. * **Vibration is poor** as a result * presents as **hoarse voice** * **stridor noticable** -\> difficulty of speaking as it relates to the need of forcing a lot more air past the wider vocal cords to produce sound.

Question 33

Outline the blood supply to the larynx

Answer 33

Blood supply is provided to the larynx from both above and below. The superior and inferior laryngeal arteries supply the majority of blood to the larynx The **superior laryngeal artery** originates from the superior thyroid branch of the external carotid artery and enters the larynx with the i**nternal branch of the superior laryngeal nerve** through the lateral aperture of the **thyrohyoid membrane.** The **inferior laryngeal artery** originates from the inferior thyroid branch **Superior and inferior laryngeal veins** drain the larynx and share the same course as the arteries

Question 34

Where is the best place to perform an emergency airway?

Answer 34

Emergency tracheotomies are best performed by perforating the **cricothyroid membrane**. Ensure to angle the perforation downwards to ensure the vocal cords aren't endangered superiorly. It is favoured over a tracheotomy due to the large network of blood vessels and nerves around the trachea -\> comparatively, there are less strunctures in endangerment with a cricothyroid membrane puncture.

Question 35

When intubating a patient, what considerations are important in best executing the procedure?

Answer 35

It is important to consider the winding path of the airways when intubating for artificial ventilation. Hyperextending the head allows for the straightening of the pathway.

Question 36

Describe the structures of the laryngopharynx

Answer 36

**Aryepiglottic folds** * defines lateral boundaries of the laryngeal inlet * are a pair of mucosal folds that run anteriorly from the arytenoid cartilages posteriorly to the epiglottis anteriorly **Piriform recesses** * located on each side of the laryngeal inlet * channels responsible for directing fluid around the laryngeal inlet because the force of fluid isn't enough to close the epiglottis **Epiglottis** * prevents food entering the airways by closing over the laryngeal inlet. **Oesophagus & Trachea** **NOTE: The thyroid cartilage, along with the entire larynx, is elevated upon swallowing to close a tight seal in conjuction with the epiglottis to prevent food entrance into laryngeal inlet. **

Question 37

Describe the sensory nerve supply to the pharynx

Answer 37

The majority of the sensory supply to the pharynx is via the **glossopharyngeal nerve** There is some sensation from the trigeminal (nasopharynx) and vagus (pharngolarynx) The **glossopharyngeal nerve** is the affernt pathway of the gag reflex

Question 38

Outline the motor supply to the pharynx How do these muscles contribute to a diagnostic reflex?

Answer 38

See the attached image Note: all muscles are supplied by the vagus nerve (except stylopharygeus which receives innervation from CN IX)

Question 39

What are the complex steps involved in swallowing / deglutition

Answer 39

1. Bolus shaped and pushed by tongue to palate 2. Soft palate descends and palatal arches are approximated to grip the food bolus and push it into the oropharynx. 3. Soft palate elevates and seals off the nasal cavity 4. Larynx and pharynx elevate to bring bolus closer to oesophagus ( + seal off laryngeal inlet) 5. Bolus is pushed down the oropharynx and over the epiglottis 6. Bolus forced down larygopharynx and into oesophagus 7. Larynx depressed to return to normal position - via elastic recoil