Session 7: The Nose and Paranasal Sinuses

Question 1

Describe the multiple functions of the nose. What is respiratory epithelium?

Answer 1

The nose has multiple functions. It is an organ of olfaction (smell), the uppermost part of the respiratory tract and plays an important role in speech.

[*] The nose, nasal cavities and the paranasal sinuses constitute the upper part of the respiratory system superior to the hard palate.

• Inferiorly, the hard palate, made up of the palatine and maxillary bones, separates the nasal and oral cavities.

[*] Each nasal cavity comprises an area of olfaction (smelling) and an area of respiratory function (breathing).

[*] Other functions of the nose and nasal cavities include filtration of dust and humidification of inspired air.

[*] The nasal cavities receive secretions from the paranasal sinuses and the nasolacrimal ducts – drain and eliminate paranasal sinus and nasolacrimal duct secretions.

[*] The nasal cavities and the paranasal sinuses are lined by respiratory epithelium – **pseudostratified columnar ciliated. **

Apart from the olfactory region - Olfactory epithelium (with non-motile cilia in the lamina propria etc), olfactory nerves and olfactory bulb

Question 2

Describe how the nasal cavities open into the nasopharynx

Answer 2

[*] The nasal cavities open into the nasopharynx (at inferior meatus) that contains the opening of the Eustachian tube.

[*] The nasopharynx has a ring of lymphoid tissue (adenoids – nasopharyngeal tonsils) that may be particularly large in children.

Question 3

Describe the external nose including its skeleton

Answer 3

[*] The external nose is the visible portion that projects from the face. It has both bony and (predominantly) cartilaginous components and provides the opening into the nasal cavity. The nostrils are bounded laterally by alae and the skin covering the nose extends upwards into the vestibule.

• The limen nasi is a ridge marking the boundary between the nasal cavity proper and the vestibule of the nose.
• Large hairs provide mechanical impedance to any inhaled particulates into nasal cavity.

[*] The skeleton of the external nose comprises bony and cartilaginous parts

• The bony part consists of nasal bones, frontal processes of the maxillae, nasal part of the frontal bone (and its nasal spine) and the bony nasal septum
• The cartilaginous part consist of 5 cartilages (2 lateral, 2 alar and a septal cartilage)

Question 4

Describe the floor and roof of the nasal cavity

Answer 4

• Each nasal cavity extends between the anterior nasal aperture (naris, nares pl.) and posterior nasal aperture (choana, choanae pl.).
• The cavity opens into the nasopharynx
• The roof of the cavity is formed by the cribriform plate of the ethmoid bone
• The floor is formed by the palatal shelf (palatine process) of the maxilla and the horizontal process of palatine bone

Question 5

Describe the medial and lateral walls of the nasal cavity

Answer 5

• Medial wall: nasal septum (the main components of which are the perpendicular plate of the ethmoid, vomer, septal cartilage and the nasal crests of the maxillary and palatine bones).
• The lateral wall of the nasal cavity has three projections (turbinates or conchae) that divide the cavity into four passages within the cavity (one unpaired – the sphenoethmoidal recess - and three paired). The conchae curve inferomedially, hanging like short curtains from the lateral wall of the nasal cavity. The conchae are scroll-like structures that offer a vast surface area for heat exchange and create turbulence in the nasal cavity.

Question 6

What bones are the conchae derived from?

Answer 6

The inferior concha is the longest and broadest and is formed by an independent bone (the Inferior Concha).

The middle and superior conchae are the **medial processes of the Ethmoid Bone. **

Question 7

Describe the mucosal lining of the nasal cavity

Answer 7

The mucous membrane lining the turbinates is highly vascular, for the purpose of humidifying the inspired air. It is continuous with areas (paranasal sinuses) draining into the cavity. The nasal cavity is completely lined with this mucosal lining apart from the vestibule.

Question 8

Describe the Sphenoethmoid Recess

Answer 8

The area between the superior turbinate and the cribriform plate of the ethmoid bone is called the sphenoethmoid recess.

• The lining epithelium of the mucous membrane in this region is modified for the purpose of olfaction; axonal processes of the olfactory cells pass through the cribriform plate and penetrate the meninges before entering the olfactory bulb.
• Each of the paired sphenoidal sinuses (or sometimes a person only has one) open into the roof of the nasal cavity via apertures on the posterior wall of the sphenoethmoidal recess, directly above the choana.
• Openings: Cribiform plate (where olfactory nerve runs), sphenopalatine foramine, incisive foramen, foramen cecum (nasal veins to superior sagittal sinus in some individuals run here)

Question 9

Describe the Superior Meatus

Answer 9

The area, which lies between the superior and middle turbinate, is called the superior meatus; the posterior ethmoidal air sinuses (cells) open into this area via one or more openings.

Question 10

Describe the Middle Meatus

Answer 10

The middle meatus, lying between the middle and inferior turbinate has the opening of the frontal air sinus anteriorly and the opening of the maxillary air sinus posteriorly.

Both these openings lie at either end of a crescenteric groove, the semilunar hiatus.

The anterior ethmoidal air sinuses (cells) also open into the middle meatus.

Question 11

Describe the Inferior Meatus

Answer 11

The inferior meatus, lying underneath the inferior turbinate, is a horizontal passage containing the opening of the nasolacrimal duct that drains tears from the orbit.

Question 12

Describe the Nasal Septum

Answer 12

• The anterior portion of the nasal septum is cartilaginous
• The central portion is formed by the perpendicular plate of the ethmoid bone
• The posterior portion is formed by the vomer bone

Question 13

Describe the blood supply to the nasal cavity and where an epitaxis occurs

Answer 13

The arterial blood supply to the medial and lateral wall of the nasal cavity is very rich.

• Branches of the Ophthalmic Artery (branch of the internal carotid artery) and Branches of the Maxillary and Facial arteries (branches of the external carotid artery) are involved.
• Facial Artery => Branch Superior Labial Artery
• Maxillary Artery => Sphenopalatine artery and Greater palatine artery
• Opthalmic Artery => Anterior ethmoidal artery and posterior ethmoidal artery

The anterior part of the nasal septum has an area (Kiesselbach or Little’s area) that is rich in capillaries where all the arteries supplying the septum anastomose.
It is in this area where profuse bleeding occurs during “nose bleeds’.

• • Rupture of blood vessels leads to spurting blood

Question 14

Describe the venous drainage to the nasal cavity

Answer 14

A rich submucosal venous plexus, deep to the nasal mucosa, drains into the

• Cavernous Sinus
• Facial Vein
• Pterygoid plexus

Question 15

Describe the innervation of the nose and nasal mucosa

Answer 15

Special Sensory (smell)

• • Olfactory nerve (CN I)

General Sensory – Posteroinferior Nasal Mucosa

• Maxillary Division of the Trigeminal Nerve (V2)
• Greater palatine nerve branch of maxillary nerve => supplies lateral wall
• Nasopalatine Nerve branch of maxillary nerve => supplies septum

General Sensory – Anterosuperior Nasal Mucosa

• Ophthalmic Division of the Trigeminal Nerve (CN V1)
• Anterior and Posterior Ethmoidal Nerves (branches of the nasociliary nerve which is a branch of the ophthalmic nerve)

General Sensory – External Nose

• External Nasal Nose (CN V1)
• Infraorbital Nerve (CN V2)

Question 16

Compare the epithelium of the respiratory region with the olfactory region

Answer 16

• Respiratory Region: pseudostratified columnar ciliated with goblet cells
• Olfactory Region: olfactory cells with olfactory receptors – non-motile cilia in the lamina propria. The olfactory cells are bipolar neurons which congregate to form the olfactory nerves which terminate at the olfactory bulb. The apical poles of these neurons are covered with non-motile cilia, with the plasma membrane containing odorant-binding proteins acting as olfactory receptors. The incoming odorants are made soluble by the serous secretion from Bowman’s glands, located in the lamina propria of the mucosa.

Question 17

Describe important anatomica relationships of the nasal cavity

Answer 17

[*] Relationship to the cranial cavity vis-à-vis fractures of the cribriform plate, CSF, rhinorrhoea (nasal discharge), anosmia

[*] Paranasal sinuses and sites opening into the nasal cavity, spread of infection from nose, special consideration of the maxillary sinus (poor natural drainage, fractures of the orbital floor; surgical approach to the pituitary gland via nose and sphenoid sinus)

[*] Relationship to the nasopharynx and oral cavity spread of infection from nose to pharynx and middle ear.

N.B: Changing proportions of the face and characteristics of the voice related to expansion of the nasal cavity and paranasal sinuses.

Question 18

Describe the Ethmoid Bone in detail

Answer 18

[*] The crista galli is a median ridge of bone that projects from the cribiform plate of the ethmoid bone.

[*] The falx cerebri is a strong fold of dura mater that descends vertically in the longitudinal fissure between the cerebral hemispheres. It is narrow in front, where it is attached to the crista galli of the ethmoid; and broad behind, where it is connected with the upper surface of the tentorium cerebelli.

[*] Olfactory bulbs lie on either side of the crista galli on top of the cribiform plate. This is how olfactory nerve fibres enter the cranial cavity.

[*] The nasal cavity is connected to the anterior cranial fossa through the cribiform plate – potential route for spread of infection.

Question 19

Describe the foramen in the nasal cavity

Answer 19

• The sphenopalatine foramen is a foramen in the skull that connects the nasal with the pterygopalatine fossa. It transmits the sphenopalatine artery and vein and the posterior superior lateral nasal nerve and nasopalatine nerves.
• The incisive foramen, aka the anterior palatine foramen, is a funnel-shaped opening in the bone of the oral hard palate immediately behind the incisor teeth. It is continuous with the incisive canal, this foramen or group of foramina are located posterior to the central incisor teeth in the incisive fossa of the maxilla. The incisive foramen receives the nasopalatine nerves from the floor of the nasal cavity along with the sphenopalatine artery, supplying the oral mucosa covering the hard palate of the mouth.
• Foramen cecum may not be present in some individuals.

Question 20

What are the paranasal sinuses and their possible functions?

Answer 20

• Paranasal sinuses (frontal, ethmoidal, sphenoidal and maxillary) are air-filled extensions (out-pocketings) of the nasal cavity into the cranial bones – frontal, ethmoid, sphenoid and maxilla, draining into the nasal cavity via narrow ducts.
• They are named according to the bones in which they’re located.
• They may contribute to conditioning of inspired air (reservoir of humidified and inspired air) and reduce weight of skull (probably marginal contribution)

Question 21

Describe the Frontal Sinuses

Answer 21

[*] The Right and Left Frontal Sinuses are between the outer and inner tables of the frontal bone, posterior to the superciliary arches and the root of the nose.

[*] They are usually detectable in children by 7 years of age (not present at birth). Variable in size

[*] They each drain through a Frontonasal Duct into the ethmoidal infundibulum (effectively the duct travels through the ethmoid bone), which opens into the semilunar hiatus of the Middle Nasal Recess.

[*] The frontal sinuses are innervated by branches of the supra-orbital nerves (CN V1).

Question 22

Describe the Ethmoidal Sinuses

Answer 22

[*] The Ethmoidal cells (sinuses) are small invaginations of the mucous membrane of the middle and superior nasal recesses into the Ethmoid bone. The small cavities are located in the lateral mass of the ethmoid bone between the nasal cavity and the orbit.

[*] The Ethmoidal cells usually are not visible in plain radiographs before 2 years of age.

[*] The Anterior Ethmoidal Cells drain directly or indirectly into the middle nasal recess through the ethmoidal infundibulum.

[*] The Middle Ethmoidal Cells open directly into the middle nasal recess (meatus)

[*] The Posterior Ethmoidal Cells, which form the ethmoidal bulla, open directly into the superior nasal recess (meatus). NB: the superior meatus is the smallest of the passageways within the nasal cavity.

[*] The ethmoidal sinuses are supplied by the anterior and posterior ethmoidal branches of the nasociliary nerves (CN V1)

Question 23

Describe the Sphenoidal Sinuses

Answer 23

[*] The Sphenoidal Sinuses are located in the body of the sphenoid (unevenly divided by a bony septum) and may extend into the wings of the bone (in elderly people).

[*] The body of the sphenoid is fragile (because of the sinuses), and only thin plates of bone separate the sinuses from several important structures (optic nerves and chiasm, the pituitary gland, internal carotid arteries and cavernous sinuses). Related to:

• Pituitary fossa (pituitary glands lies in the sella turcica in the sphenoid bone), belongs to middle cranial fossa
• Cavernous sinus and ICA
• Posterior cranial fossa and pons
• (Effectively forms) roof of nasopharynx

[*] The posterior ethmoidal artery and nerve supply the sphenoidal sinuses.

[*] They are small at birth, enlarging after puberty

[*] They drain directly into the Sphenoethmoidal Recess

Question 24

Describe the Maxillary Sinuses§

Answer 24

Of all the paranasal sinuses, the maxillary sinus is the largest and occupies almost the whole of the maxilla. Because of the superior location of this opening, it is impossible for the sinus to drain when the head is erect until the sinus is full.

[*] They drain by one or more openings, the Maxillary Ostium (ostia), into the middle nasal recess by way of the semilunar hiatus.

[*] Roof = floor of orbit

[*] Floor = alveolar part maxilla. The roots of the maxillary teeth, particularly the first two molars, often produce conical elevations in the floor of the maxillary sinus.

[*] Poteriorly = Pterygopalatine and infratemporal fossae

[*] Present at birth, enlarging from about 8 years

[*] The arterial supply of the maxillary sinus is mainly from superior alveolar branches of the maxillary artery; however branches of the greater palatine artery supply the floor of the sinus.

[*] Innervation of the maxillary sinus mucosa is from the anterior, middle and posterior superior alveolar nerves, branches of CN V2

Question 25

Summarise where all the sinuses drain into. What epithelium do they have?

Answer 25

Question 26

Describe Nasal fractures including their complications

Answer 26

Nasal Fractures: nasal fractures are the most common facial fracture, as the nose is an exposed organ – particularly when lateral force is applied e.g. by someone’s elbow. [\*] History of force to the face e.g. falling, punch [\*] Deformity [\*] Complications include **septal haematoma** (a large collection of blood within the **cartilaginous septum** – separates the septum from the perichondrium. As the septum is avascular and reliant for all its nutrients and oxygen from the perichondrium, an untreated septal haematoma may lead to **necrosis of the septum**. Immediate drainage is necessary. Failure to recognise septal haematomas or to treat in a timely fashion can cause a **saddle nose deformity. **

Question 27

Describe Epistaxis

Answer 27

[\*] Associated with **respiratory infections** and **hypertension** [\*] Nosebleeds are common and in some people these can occur frequently for various reasons, ranging from benign, disorders of the clotting system of blood, disorders of the cardiovascular system etc. [\*] Cause can be either local or systemic [\*] **Anterior bleeds** account for 90% of epistaxis. The **Sphenopalatine Artery** (traverses through the sphenopalatine foramen, branch of the maxillary artery) causes posterior bleeds. [\*] In most cases, the cause is **trauma**, and the bleeding is from an area in the **anterior third** of the nose (**Kiesselbach area**). [\*] The spurting of blood from the nose results from rupture of arteries. [\*] **Mild epistaxis** may also result from nose-picking, which tears **veins** in the **vestibule** of the nose.

Question 28

How may a direct blow on the nose lead to anosmia?

Answer 28

A direct blow on the nose may result in fracture of the cribriform plate of the ethmoid bone resulting in the **tearing of overlying meninges and leakage of cerebrospinal fluid** into the nasal cavity (rhinorrhoea) [\*] **Tearing of axons of the olfactory cells** that may occur following a **fracture of the cribriform plate** of the ethmoid bone in head injuries results in **anosmia**.

Question 29

Describe the consequences of a deviated nasal septum

Answer 29

Due to injuries (e.g. birth injury, fist fights), the nasal septum can be deflected, sometimes so severely that the **nasal septum** is in **contact** with the **lateral wall** of the **nasal cavity** and often **obstructs breathing** or **exacerbates snoring**. Nasal obstruction that may require surgical correction [\*] A deformed or deviated nasal septum may affect nasal breathing. In such cases, the **cartilaginous portion can be removed** (submucous resection – SMR) in part or whole to alleviate the problem. [\*] A saddle nose deformity could occur due to **nasal septum necrosis. **

Question 30

What is meant by Sinusitis and Rhinitis? What is considered an acute infection, what is considered a chronic infection?

Answer 30

The nasal cavity can be involved in infections that can involve the sinuses; these conditions are rhinitis and sinusitis. [\*] Infections from the nasal cavity may spread into the sinuses causing inflammation of the mucosa (sinusitis) and local pain. * Acute: 7 to 30 days * Sub-acute: 4 to 12 weeks * Chronic: \>90 days * Infection **Viral with secondary bacterial infection** (a vicious cycle is created as overproduction of mucus and oedema =\> **obstruction** =\> secondary infection) * Streptococcus pneumoniae * Haemophillus influenzae Sometimes **several sinuses are inflamed** (**pansinusitis**) and the **swelling of the mucosa** may block one or more openings of the sinuses into the nasal cavities.

Question 31

Why might infections of the ethmoidal sinuses lead to visual disorders?

Answer 31

Infections in the air cells of the ethmoidal sinuses may break through the **medial wall of the orbit** and cause visual disorders because of the proximity of the in particular **posterior ethmoidal air cells to the optic canal**, which transmits the **optic nerve** (2nd cranial nerve) and the **ophthalmic artery**. Infection may also affect the dural sheath of the optic nerve (**optic neuritis** – inflammation of optic nerve). * Could lead to visual disorders

Question 32

What are the causes of Rhinitis? How may infections spread?

Answer 32

[\*] Rhinitis: inflammation of the nasal mucosa, leading to swelling and increased volume of secretion. Causes include Infective (Viral) * Adenovirus * Rhinovirus * Respiratory Syncytial Virus (RSV) Allergic e.g. hay fever Nasal polyps Swelling of the mucosa occurs readily because of its **vascularity and glandular nature. *(The nasal mucosa is frequently the site of inflammatory reactions to allergens and respiratory infections. The mucosa becomes swollen and inflamed (rhinitis) because of its vascularity and abundance of mucosal glands.) *** Infections of the nasal cavities may spread to the **anterior cranial fossa** through the **cribriform plate**, **nasopharynx** and **retropharyngal soft tissues**, **middle ear** through the pharyngotympanci tube (**auditory tube**), which connects the **tympanic membrane and nasopharynx, paranasal sinuses, lacrimal apparatus and conjunctiva.**

Question 33

Why is the Maxillary Sinus the most commonly affected of all the sinuses?

Answer 33

[\*] The maxillary sinus is most commonly affected. It is thought that this is because of the location of its **opening high (superior) on the medial wall** of the maxilla. The ostia are also commonly **small**. * When the mucus membrane of the sinus is congested, the maxillary ostia are often obstructed. * Impossible for sinuses to drain when the head is erect until they are full * Because the ostia of the right and left sinuses lie on the medial sides (are directed towards each other), when lying on one’s side, only the **upper sinus** (e.g. the right sinus if lying on the left side) drains. * A cold or allergy involving both sinuses can result in nights of rolling from side-to-side in an attempt to keep the sinuses drained. A maxillary sinus can be cannulated and drained by passing a cannula from the nares through the maxillary ostium into the sinus. * [\*] The **roots** of maxillary teeth, particularly the f**irst two/three molars**, often project into the floor of the maxillary sinus. On occasions the root of a tooth may **perforate the bone** and lie just **beneath the mucous membrane** (root has been driven superiorly into the maxillary sinus). Fracture of the root during tooth extraction may lead to serious problems due to a creation of a communication (**fistula)** between the oral cavity and sinus. Infection may occur. [\*] Because the **superior alveolar nerves** (branches of the maxillary nerve CN V2) supply both the **maxillary teeth and the mucous membrane of the maxillary sinuses**, inflammation of the mucosa of the sinus is frequently accompanied by sensation of toothache in the molar teeth.

Question 34

Describe Benign and Malignant masses in the external cavity

Answer 34

[\*] Benign conditions include **polypi** which originate from the **sinuses** or conditions like **foreign bodies and rhioliths** (stone formation). [\*] The cavity can also harbour **tumours** and invasive infections like **fungal infections.** [\*] Due to close anatomical pathways, spread to cranial cavity can also occur. **Nasal Polyps** [\*] Grow close to the ostiomeatal complex of the Nasopharynx [\*] Linked to chronic rhinosinusitis Due to irritation of the mucosal epithelium inflammation leading to oedema. Histologically **marked thickening** of the epithelium can be seen as well as **eosinophilic infiltrates ** (inflammatory cell component) [\*] Prevalence of ~2-4% [\*] Nasal obstruction - Snoring / Sleep obstructive apnoea

Question 35

How may infections spread in the nasal cavity?

Answer 35

Infections of the nasal cavity may spread to the **anterior cranial fossa** through the **cribriform plate** of the **ethmoid bone**. Infections may also spread into the **paranasal sinuses** via their openings into the cavity, and to the **lacrimal apparatus** and **conjunctiva** via the opening of the **nasolacrimal duct**. The middle ear may become infected via the **Eustachian tubes.** The nasal cavity is also closely related to the **nasopharynx** and tumours, masses or adenoids can spread the diseases to the ears through Eustachian tubes. [\*] Eustachian tube dysfunction [\*] Nasopharyngeal carcinoma

Question 36

What supplies secretomotor function to the glands of the nasal mucosa?

Answer 36

The facial nerve!