May 25, 2026 PDF Available

Topic Overview

MedMentor EDU

ENT Study Notes

ANATOMY OF THE NOSE

Functional & Applied Nasal Anatomy | Rhinology | FESS

For MBBS · NEET-PG · INI-CET · Viva Voce

Based on: Dhingra | Ramalingam | Logan Turner

SECTION 1 | Introduction to Nasal Anatomy

1.1 Importance of Nasal Anatomy

The nose is the first gateway of the respiratory tract. A thorough knowledge of nasal anatomy is essential for:

Clinical examination and diagnosis of nasal disorders
Surgical planning and execution of rhinoplasty, septoplasty, and FESS
Understanding pathophysiology of sinusitis, epistaxis, and nasal polyps
Safe surgical navigation near critical structures — skull base, orbit, carotid artery

1.2 Functional Anatomy of the Nose

The nose serves five major physiological functions:

Respiration — airway for inspired and expired air
Olfaction — smell receptors in olfactory mucosa
Filtration — trapping of particles >5 µm by mucus and cilia
Humidification — inspired air reaches 100% humidity by nasopharynx
Temperature regulation — turbinates warm air to 32–37°C

1.3 Applied Anatomy in ENT Surgery

Epistaxis management — ligation of sphenopalatine artery, anterior ethmoidal artery
FESS (Functional Endoscopic Sinus Surgery) — osteomeatal complex navigation
Septoplasty — septal cartilage and bony framework approach
Rhinoplasty — cartilaginous and bony nasal framework modification
CSF rhinorrhea repair — cribriform plate and ethmoid roof anatomy
Dacryocystorhinostomy — nasolacrimal duct relation to inferior meatus

1.4 Surgical Relevance in Rhinology

EXAM TIP

The nose is divided into EXTERNAL NOSE and NASAL CAVITY. The nasal cavity is further bounded by the nasal septum medially and the lateral nasal wall laterally.

SECTION 2 | External Nose

2.1 Surface Anatomy

The external nose is a pyramidal projection in the centre of the face. Key surface landmarks:

Structure	Description
Root (Radix)	Superior part; junction of nose with forehead
Dorsum	Bridge of nose; from root to tip
Tip (Apex)	Most anterior projecting point
Ala	Lateral wall of nasal vestibule; forms nostril rim
Columella	Skin-covered strip between nares; overlies medial crura
Nares (Nostrils)	Paired oval openings at base of nose

2.1.1 Soft Tissue Triangles of the Nose

Soft triangle (Facet): Junction of ala and columella; no cartilage — prone to notching after surgery
Alar-facial groove: Boundary between ala and cheek; important cosmetic subunit
Columellar-labial angle: Ideally 90–100° in males; 100–110° in females

2.1.2 Cosmetic Subunits of Nose (Burget Classification)

The nose is divided into 9 aesthetic subunits for reconstructive planning:

Tip
Dorsum
Two lateral sidewalls
Two ala
Two soft triangles
Columella

CLINICAL PEARL

If >50% of a subunit is involved in a defect → replace the entire subunit. Important for nasal reconstruction.

2.2 Skin & Soft Tissue Layers

2.2.1 Skin Thickness Variations

Thin skin: Root and dorsum — allows show-through of cartilage
Thick skin: Tip and ala — due to thick sebaceous dermis
Moderate skin: Middle dorsum

EXAM TIP

Tip skin is THICK and sebaceous — this is why rhinoplasty results are less predictable at the tip compared to the dorsum.

2.2.2 SMAS Layer (Superficial Musculoaponeurotic System)

Continuous with SMAS of face
Contains nasal muscles and their interconnections
Important in facelift and rhinoplasty surgery

2.2.3 Fibrofatty Layer

Deep to skin; perichondrium continuous with it
Important plane in closed rhinoplasty approaches

2.3 Osteocartilaginous Framework

2.3.1 Bony Framework

Upper 1/3 of external nose is bony
Nasal bones: Paired; form the bony vault; thicker superiorly, thinner inferiorly
Frontal process of maxilla: Forms lateral bony support
Nasal process of frontal bone: Forms the root of nose
Pyriform aperture: Pear-shaped bony opening of nasal cavity into face

MCQ

The THINNEST part of the nasal bone is at its inferolateral margin — MOST COMMON site of nasal bone fracture.

2.3.2 Cartilaginous Framework

Lower 2/3 of external nose is cartilaginous

Cartilage	Key Features
Upper lateral cartilage (ULC)	Paired; fused to septal cartilage superiorly at keystone area; forms middle vault
Lower lateral cartilage (LLC)	Paired; forms nasal tip; has medial, middle and lateral crura
Septal cartilage	Quadrangular; forms medial support; contributes to anterior septum
Sesamoid cartilages	Small accessory cartilages in alar groove between LLC and ULC

Scroll Area

Junction of caudal ULC and cephalic LLC — overlapping scroll-like anatomy
Important in internal nasal valve function

Keystone Area

Junction of nasal bones, ULC, and septal cartilage
Most important structural point of nose
Disruption → saddling/step deformity of dorsum

HIGH YIELD

The internal nasal valve angle is formed between the ULC and nasal septum — normally 10–15°. Narrowing → nasal obstruction.

2.4 Nasal Tip Support Mechanisms

Tip support is provided by MAJOR and MINOR mechanisms:

Major Tip Support

Size, shape and resilience of LLC (alar cartilage) — PRIMARY support
Attachment of medial crura footplates to caudal septum — scroll ligament
Attachment of caudal ULC to cephalic LLC

Minor Tip Support

Ligamentous attachment of LLC to piriform aperture
Anterior nasal spine
Cartilaginous septal dorsum
Skin and soft tissue envelope
Sesamoid cartilages

VIVA

If all major tip supports are disrupted during rhinoplasty → tip rotation and loss of projection. This is why medial crura-septal suture (tongue-in-groove) is crucial.

2.4.1 Medial Crura Anatomy

Forms central dome of nasal tip
Medial crural footplate: Attached to anterior nasal spine
Intermediate crus: Between medial and lateral crus; forms tip-defining point
Lateral crus: Extends laterally into ala

2.5 Muscles of External Nose

Muscle		Nerve Supply	Action
Procerus		Facial nerve (VII)	Pulls skin of forehead down; horizontal wrinkles at bridge
Nasalis		Facial nerve (VII)	Compressor nasalis narrows nares; dilator nasalis opens nares
Depressor septi		Facial nerve (VII)	Pulls nasal tip downward during smiling
Levator labii superioris alaeque nasi		Facial nerve (VII)	Dilates nares; elevates upper lip
MCQ	All muscles of the external nose are supplied by branches of the FACIAL NERVE (CN VII).

SECTION 3 | Blood Supply of External Nose

3.1 Arterial Supply

3.1.1 External Carotid System

Facial artery → angular artery: Supplies lateral nose and ala
Superior labial artery: Supplies columella and base of septum

3.1.2 Internal Carotid System

Ophthalmic artery → Dorsal nasal artery: Supplies dorsum of nose
Ophthalmic artery → External nasal nerve artery: Supplies nasal tip

3.2 Kiesselbach Plexus (Little's Area)

VERY HIGH YIELD

Kiesselbach plexus / Little's area is the MOST COMMON site of epistaxis in children and young adults.

Location: Anteroinferior part of nasal septum
Arterial anastomosis between 5 vessels:
- Anterior ethmoidal artery (from ophthalmic)
- Sphenopalatine artery (from maxillary)
- Greater palatine artery (from maxillary)
- Superior labial artery (from facial)
- Posterior septal artery

3.3 Woodruff Plexus

Located: Posterior part of inferior meatus — posterolateral nasal wall
Arterial network of sphenopalatine and ascending pharyngeal arteries

EXAM PEARL

Woodruff plexus = Site of POSTERIOR epistaxis (seen in elderly and hypertensives). Requires posterior nasal packing or SPA ligation.

Feature	Kiesselbach Plexus	Woodruff Plexus
Location	Anteroinferior nasal septum	Posterior inferior meatus
Common in	Children and young adults	Elderly, hypertensives
Epistaxis type	Anterior epistaxis	Posterior epistaxis
Management	Pressure, cautery, anterior pack	Posterior pack, SPA ligation

3.4 Venous Drainage

Facial vein: Drains anterior external nose
Ophthalmic vein → Cavernous sinus: Drains superior nose
Pterygoid plexus: Drains posterior nasal region

HIGH YIELD — DANGER AREA OF FACE

The angular vein communicates with the ophthalmic vein → cavernous sinus. Infections of the DANGER AREA of face (upper lip, nose, orbit triangle) can spread intracranially via this route causing cavernous sinus thrombosis.

3.5 Lymphatic Drainage of External Nose

Anterior nose: Submandibular lymph nodes
Posterior nose: Retropharyngeal lymph nodes → Upper deep cervical nodes

3.6 Nerve Supply of External Nose

Nerve	Area Supplied
Infratrochlear nerve (CN V1)	Root and upper lateral wall of nose
External nasal nerve (from anterior ethmoidal)	Tip and ala of nose
Infraorbital nerve (CN V2)	Lower lateral wall and ala
Autonomic (sympathetic + parasympathetic)	Nasal vasculature and glands via vidian nerve

SECTION 4 | Nasal Cavity

4.1 Boundaries of the Nasal Cavity

Wall	Structures
Roof	Nasal bones anteriorly, cribriform plate of ethmoid (olfactory area), body of sphenoid posteriorly
Floor	Hard palate (palatine process of maxilla + horizontal plate of palatine bone)
Medial wall	Nasal septum (described separately)
Lateral wall	Complex wall with turbinates and meatuses (described separately)
Anterior opening	Anterior nares / nostrils
Posterior opening	Choanae — communicate with nasopharynx

4.2 Roof of Nasal Cavity

Parts of the Roof (Anterior to Posterior)

Frontonasal part: Nasal bones and frontal bone — slopes upward
Ethmoidal part: Cribriform plate of ethmoid — horizontal; contains olfactory foramina
Sphenoidal part: Body of sphenoid — slopes downward

Cribriform Plate — CLINICAL IMPORTANCE

Contains multiple foramina for olfactory nerve filaments (fila olfactoria)
Most delicate part of anterior cranial fossa floor
Common site of CSF rhinorrhea after head injury or FESS
Keros classification describes depth of olfactory fossa (see Section 14)

HIGH YIELD

The OLFACTORY FOSSA is bounded by: Medially — nasal septum; Laterally — medial wall of ethmoid (fovea ethmoidalis). Keros Type III fossa (deepest) = HIGHEST RISK during FESS.

4.3 Floor of Nasal Cavity

Formed by: Palatine process of maxilla (anterior 2/3) + Horizontal plate of palatine bone (posterior 1/3)
Floor is concave transversely
Incisive canal (canal of Stenson): At junction of palatal bones — transmits nasopalatine nerve and greater palatine vessels
Relation to oral cavity: Roof of mouth = floor of nose; important in palatal surgery

SECTION 5 | Nasal Septum

5.1 Components of the Nasal Septum

The nasal septum divides the nasal cavity into left and right halves. It has bony and cartilaginous parts:

Component		Type	Position
Quadrangular (septal) cartilage		Cartilaginous	Anterior 2/3; most clinically important
Perpendicular plate of ethmoid		Bony	Posterior superior
Vomer		Bony	Posterior inferior; articulates with nasal crest
Maxillary crest		Bony	Inferoanterior groove for septal cartilage
Palatine crest		Bony	Posteroinferior — continuation of maxillary crest
Nasal crest of maxilla		Bony	Floor level support
MCQ	The VOMER is the bone that forms the posterior inferior portion of the nasal septum. It articulates with the sphenoid superiorly and the hard palate inferiorly.

5.2 Septal Attachments

Superior: Fused to undersurface of nasal bones (medial aspect of ULC at keystone)
Inferior (caudal septum): Attached to anterior nasal spine — MOST IMPORTANT support for nasal tip
Posterior: Articulates with perpendicular plate of ethmoid and vomer
Nasal spine attachment: Strongest inferior fixation of septum

5.2.1 Septal Growth Centres

Septal cartilage is a PRIMARY growth centre of the midface
Septal fractures/injuries in childhood → impaired midface growth
Septoplasty should ideally be deferred until 16–18 years to preserve growth

5.3 Septal Blood Supply

Anterior ethmoidal artery (ophthalmic → internal carotid)
Posterior ethmoidal artery (ophthalmic → internal carotid)
Sphenopalatine artery: MAIN blood supply to posterior septum
Greater palatine artery: Ascending branch to anteroinferior septum
Superior labial artery: Anteroinferior septum
ALL five vessels anastomose at KIESSELBACH PLEXUS (Little's area)

5.4 Septal Deformities

DNS (Deviated Nasal Septum) — Classification

Type	Description
C-shaped	Smooth curve toward one side
S-shaped	Two opposite C-shaped curves
Spur	Sharp bony/cartilaginous projection from septum
Crest	Horizontal ridge at floor — maxillary or palatine crest
Dislocation	Anterior caudal septum dislocates out of septal groove
Combination	Multiple deformities together

5.4.1 Septal Perforation Sites and Causes

Anterior septum (Little's area): Trauma, cauterization, cocaine use, Wegener's granulomatosis
Posterior septum: Syphilis, tuberculosis (less common)
Rim of columella: Post-rhinoplasty

COMMON MCQ

Most common cause of septal perforation = Trauma / nose picking (digital trauma). Most common INFECTIVE cause = Syphilis (posterior septum involvement).

SECTION 6 | Lateral Wall of Nose

6.1 Turbinates (Conchae)

The lateral wall of the nasal cavity contains three or four turbinates (conchae) — bony shelves covered with respiratory mucosa that project into the nasal cavity:

Turbinate	Bone of Origin	Key Features
Inferior turbinate	Separate bone — largest turbinate	Largest; erectile tissue; most important for humidification; hypertrophy causes nasal obstruction
Middle turbinate	Ethmoid bone	Key landmark in FESS; ground lamella divides anterior and posterior ethmoid
Superior turbinate	Ethmoid bone	Small; above it = sphenoethmoidal recess; olfactory mucosa nearby
Supreme turbinate	Ethmoid bone (variable)	Inconstant; when present, above superior turbinate

6.1.1 Histology and Physiology of Turbinates

Covered by pseudostratified ciliated columnar epithelium (respiratory mucosa)
Rich in venous sinusoids — ERECTILE TISSUE
Nasal cycle: Cyclical congestion/decongestion of turbinates; left vs right, alternating every 2–6 hours
Inferior turbinate has the MOST erectile tissue — largest functional role

VIVA FAVOURITE

The nasal cycle is regulated by the HYPOTHALAMUS via autonomic nerves. It occurs in 80% of normal individuals. Detected by pneumotachometry.

6.1.2 Anatomical Variations of Turbinates

Concha bullosa: Pneumatization of middle turbinate — commonest turbinate variation; may cause osteomeatal complex obstruction
Paradoxical middle turbinate: Middle turbinate curves laterally instead of medially → obstructs osteomeatal complex
Secondary middle turbinate: Extra ridge from lateral wall — may be confused with accessory turbinate

6.2 Meatuses of Nose

Meatus		Location	Drainage
Superior meatus		Between superior and middle turbinate	Posterior ethmoidal air cells
Middle meatus		Between middle and inferior turbinate	Frontal sinus, maxillary sinus, anterior and middle ethmoidal cells
Inferior meatus		Between inferior turbinate and floor	Nasolacrimal duct (Hasner's valve)
Sphenoethmoidal recess		Above and behind superior turbinate	Sphenoidal sinus
MCQ FAVOURITE	The NASOLACRIMAL DUCT opens into the INFERIOR MEATUS (Hasner's valve). Obstruction → epiphora. DCR (dacryocystorhinostomy) creates a new opening here.

6.3 Sphenoethmoidal Recess

Located above and posterior to the superior turbinate
Receives the opening of the sphenoidal sinus
Access to sphenoid sinus during surgery uses this recess as landmark

SECTION 7 | Osteomeatal Complex (OMC)

7.1 Introduction

VERY HIGH YIELD

The osteomeatal complex (OMC) is the final common pathway for drainage of the frontal, maxillary, and anterior ethmoidal sinuses. Obstruction of the OMC is the primary cause of CHRONIC RHINOSINUSITIS.

7.2 Components of the OMC

Structure	Description
Uncinate process	Sickle-shaped bony process; medial wall of infundibulum; first structure removed in FESS
Ethmoidal bulla	Largest anterior ethmoidal cell; bulges into middle meatus
Hiatus semilunaris	Crescent-shaped cleft between uncinate process and ethmoidal bulla
Infundibulum	Funnel-shaped space; receives maxillary sinus drainage
Frontal recess	Opening of frontal sinus into middle meatus; bounded by agger nasi cell anteriorly
Ground lamella (Basal lamella)	Basal attachment of middle turbinate; separates anterior from posterior ethmoid

7.3 Fontanelles

Fontanelles: Membranous areas in lateral nasal wall (anterior and posterior fontanelles)
Located between the uncinate process and inferior turbinate
Accessory maxillary sinus ostium may be found here
Clinically: Site for inferior meatal antrostomy in maxillary sinus drainage

7.4 Functional Significance of OMC

Drainage pathway: Frontal → frontal recess → middle meatus; Maxillary → infundibulum → hiatus semilunaris → middle meatus
Mucociliary clearance: Cilia beat toward natural ostia → OMC → nasopharynx
Obstruction sites: Concha bullosa, paradoxical middle turbinate, hypertrophied agger nasi cell, deviated septum compressing OMC

CLINICAL PEARL

FESS targets the OMC to restore normal sinus drainage and ventilation. The goal is NOT to remove all mucosa but to open the drainage pathways.

SECTION 8 | Openings into the Nasal Cavity

8.1 Summary of Sinus Openings

Site of Opening		Structure Draining
Superior meatus		Posterior ethmoidal sinuses
Middle meatus — frontal recess		Frontal sinus
Middle meatus — hiatus semilunaris		Maxillary sinus (natural ostium)
Middle meatus — ethmoidal bulla		Middle ethmoidal cells
Middle meatus (anterior to bulla)		Anterior ethmoidal cells
Inferior meatus		Nasolacrimal duct (Hasner's valve)
Sphenoethmoidal recess		Sphenoidal sinus
MCQ	The maxillary sinus opens HIGH on its medial wall (near the roof of sinus) — this is a DISADVANTAGE as gravity cannot assist drainage. Ciliary action must carry secretions upward to the natural ostium.

8.2 Paranasal Sinus Relations — Clinically Important

Maxillary Sinus Relations

Floor of orbit: Roof of maxillary sinus — infraorbital nerve runs here → risk in Caldwell-Luc surgery
Roots of upper teeth: Molars (2nd molar closest) and premolars adjacent to sinus floor
Dental infections can cause maxillary sinusitis (dentoalveolar route)

Ethmoid Sinus Relations

Lamina papyracea: Thin medial orbital wall — lateral boundary of ethmoid sinus
Breach during FESS → orbital fat herniation, medial rectus injury, orbital haematoma
Optic nerve: Close to posterior ethmoid and sphenoid sinuses

Sphenoid Sinus Relations

Optic nerve (CN II): Superolateral wall; may cause optic nerve dehiscence
Internal carotid artery: Lateral wall; dehiscence reported in 25% of specimens
Cavernous sinus: Lateral wall — route of spread in sphenoid sinusitis
Pituitary gland: Superior wall — trans-sphenoidal hypophysectomy route

VIVA DANGER ZONE

During trans-sphenoidal pituitary surgery, the following are at risk: ICA laterally, optic nerve superolaterally, cavernous sinus laterally, carotid siphon.

SECTION 9 | Mucosa of the Nose

9.1 Respiratory Mucosa

9.1.1 Distribution

Lines majority of nasal cavity — all surfaces except olfactory area and vestibule

9.1.2 Histology

Epithelium: Pseudostratified ciliated columnar epithelium (PSCCE)
Goblet cells: Mucus-secreting unicellular glands embedded in epithelium
Mucous glands: Submucosal serous and mucous tubuloalveolar glands
Basement membrane: Thick; below epithelium
Lamina propria: Loose connective tissue with venous sinusoids

Ciliary Ultrastructure

9+2 microtubule arrangement (9 peripheral doublets + 2 central singlets)
Dynein arms between doublets — ATPase-dependent movement
Ciliary beat frequency: 1000 beats/minute
Beat direction: Posteriorly toward nasopharynx

MCQ

Kartagener syndrome = Primary ciliary dyskinesia (dynein arm defect) → absence of ciliary movement → recurrent sinusitis, bronchiectasis, situs inversus + male infertility.

9.2 Olfactory Mucosa

9.2.1 Location

Located in roof of nasal cavity — olfactory cleft
Area: Approximately 2.5 cm² on each side
Contains receptor cells for smell

9.2.2 Cell Types (Schultze, 1856)

Olfactory receptor cells (bipolar neurons): Unmyelinated axons pass through cribriform plate as olfactory fila
Supporting (sustentacular) cells: Columnar supporting cells
Basal cells: Stem cells; allow regeneration of olfactory receptors

9.2.3 Olfactory Fila

Bundles of unmyelinated olfactory axons
Pass through cribriform foramina to olfactory bulb
Number: Approximately 20 fila on each side
Injury in head trauma → anosmia

9.3 Blood Supply: Mucosal Venous Sinusoids

Mucosal stroma rich in venous sinusoids — especially in inferior turbinate
Rapid filling → nasal congestion; emptying → decongestion
Controlled by sympathetic (vasoconstriction) and parasympathetic (vasodilation) systems

SECTION 10 | Blood Supply of the Nasal Cavity

10.1 Arterial Supply

10.1.1 Internal Carotid System

Ophthalmic artery → Anterior ethmoidal artery (AEA): Supplies anterosuperior nasal cavity, septum, lateral wall
Ophthalmic artery → Posterior ethmoidal artery (PEA): Supplies posterosuperior nasal cavity
AEA enters nose through anterior ethmoidal foramen — 24 mm posterior to lacrimal crest
PEA enters through posterior ethmoidal foramen — 12 mm posterior to AEA

EXAM PEARL

ANTERIOR ETHMOIDAL FORAMEN location: 24 mm behind anterior lacrimal crest. POSTERIOR ETHMOIDAL FORAMEN: 12 mm behind AEA. OPTIC CANAL: 6 mm behind PEF. Rule of thumb: 24-12-6 rule.

10.1.2 External Carotid System

Maxillary artery → Sphenopalatine artery (SPA): MAIN blood supply to nasal cavity
SPA enters nasal cavity through sphenopalatine foramen → lateral nasal artery (lateral wall) + posterior septal artery (septum)
Maxillary artery → Greater palatine artery: Enters via incisive canal → anteroinferior septum
Facial artery → Superior labial artery: Anteroinferior septum and columella

10.2 Sphenopalatine Foramen — Surgical Anatomy

Located at posterior end of middle meatus — medial wall of pterygopalatine fossa
Just posterior to the posterior attachment of middle turbinate
SPA ligation here controls posterior epistaxis — performed endoscopically

SURGICAL TIP

Endoscopic SPA ligation: Middle turbinate reflected → posterior attachment of middle turbinate used as landmark → sphenopalatine foramen identified and SPA clipped.

10.3 Venous Drainage

Anterior nasal cavity → Facial vein → Internal jugular vein
Posterior nasal cavity → Pterygoid plexus → Maxillary vein → IJV
Superior nasal cavity → Ophthalmic vein → Cavernous sinus (DANGER ZONE)

10.4 Lymphatic Drainage

Anterior 1/3 of nasal cavity: Submandibular lymph nodes
Posterior 2/3 of nasal cavity: Retropharyngeal lymph nodes → Upper deep cervical nodes
Olfactory mucosa has no lymphatics — no lymphatic drainage from olfactory region

SECTION 11 | Nerve Supply of the Nasal Cavity

11.1 Sensory Supply

Nerve	Origin	Area Supplied
Olfactory nerve (CN I)	Olfactory bulb	Smell — from olfactory mucosa; passes through cribriform plate
Anterior ethmoidal nerve	CN V1 (ophthalmic)	Anterosuperior septum and lateral wall; external nose tip (as external nasal nerve)
Nasopalatine nerve	CN V2 (maxillary)	Posteroinferior septum; hard palate
Posterior superior nasal nerve	CN V2 via pterygopalatine ganglion	Posterior superior lateral wall
Posterior inferior nasal nerve	CN V2 via greater palatine	Posterior inferior lateral wall
Infraorbital nerve	CN V2	Lateral wall of nasal cavity anteriorly

11.2 Autonomic Supply

11.2.1 Parasympathetic Supply

Origin: Superior salivatory nucleus
Travels via: Facial nerve (CN VII) → GSPN (greater superficial petrosal nerve) → Vidian nerve → Pterygopalatine ganglion → postganglionic fibres to nasal mucosa
Function: Vasodilation of venous sinusoids (congestion), increased mucous secretion

11.2.2 Sympathetic Supply

Origin: T1-T2 lateral horn → cervical sympathetic chain → Superior cervical ganglion
Travels via: Deep petrosal nerve → Vidian nerve → Pterygopalatine ganglion → nasal mucosa
Function: Vasoconstriction of sinusoids (decongestion)

11.2.3 Vidian Nerve (Nerve of Pterygoid Canal)

Formed by: GSPN (parasympathetic) + Deep petrosal nerve (sympathetic)
Passes through vidian canal (pterygoid canal) → pterygopalatine ganglion
Clinical: Vidian neurectomy — surgical treatment for vasomotor rhinitis

11.2.4 Pterygopalatine Ganglion (Meckel Ganglion)

Located in pterygopalatine fossa
Parasympathetic relay ganglion for nasal, palatal, and lacrimal glands
Connections: CN V2, GSPN, deep petrosal nerve, orbital and nasal branches
Block: Sphenopalatine ganglion block — treats cluster headaches and refractory rhinitis

HIGH YIELD

Pterygopalatine ganglion = 'Ganglion of hayfever' — parasympathetic stimulation causes watery nasal discharge (rhinorrhea) and lacrimation. Surgical target in Vidian neurectomy.

SECTION 12 | Embryology of the Nose

12.1 Development of the External Nose

Week 4: Olfactory placodes appear on frontonasal process
Placodes invaginate → olfactory pits
Medial nasal process forms: Philtrum, columella, anterior nasal spine, premaxilla
Lateral nasal process forms: Lateral wall of nose, alae
Fusion failure of medial and lateral nasal processes → cleft lip

12.2 Development of the Nasal Septum

Nasal septum develops from: Medial nasal process (anterior) + nasal capsule (posterior)
Fusion of lateral palatine processes with nasal septum inferiorly → forms hard palate
Failure of palatal fusion → cleft palate

12.3 Development of the Palate

Primary Palate

Formed by medial nasal processes
Premaxillary portion — anterior to incisive foramen
Develops at week 5–6

Secondary Palate

Formed by lateral palatine processes (from maxillary processes)
Posterior to incisive foramen
Palatine processes elevate, meet in midline, and fuse (week 7–8)
Fuse anteriorly with primary palate and posteriorly form soft palate

12.4 Choanal Development

Posterior nasal cavity opens into nasopharynx through choanae
Initially closed by bucconasal membrane → ruptures at week 7
Failure of rupture → choanal atresia (most common at posterior choana)

MCQ

Choanal atresia: Most cases are BONY (90%) and UNILATERAL (60%). Bilateral choanal atresia = neonatal emergency (obligate nasal breathers). COLOBOMA, Heart defect, Atresia choanae, Retarded growth, Genital abnormalities, Ear abnormalities = CHARGE syndrome.

12.5 Developmental Anomalies

Anomaly		Description	Clinical Significance
Choanal atresia		Failure of rupture of bucconasal membrane	Bilateral → respiratory distress at birth; unilateral → unilateral nasal obstruction
Cleft lip		Failure of fusion of medial and lateral nasal processes	Cosmetic and functional; associated with cleft palate
Cleft palate		Failure of palatine process fusion	Speech impairment, feeding difficulties, recurrent OM
Nasal glioma		Ectopic glial tissue in or around nose	Not connected to CSF; does not transilluminate; no increase with Valsalva
Encephalocele		Herniation of brain tissue through skull defect	Connected to CSF; transilluminates; increases with Valsalva/Furstenberg sign
Nasal dermoid		Lined by skin; may have sinus tract to cribriform plate	Risk of meningitis if intracranial extension
IMPORTANT	FURSTENBERG SIGN: Compressing the jugular vein causes the mass to ENLARGE in ENCEPHALOCELE (as CSF communication present) but NOT in nasal glioma.

SECTION 13 | Applied Anatomy

13.1 Epistaxis Anatomy

HIGH YIELD

90% of epistaxis is ANTERIOR from Little's area (Kiesselbach plexus). 10% is POSTERIOR from Woodruff plexus or other posterior vessels (SPA). Posterior epistaxis is more severe and harder to control.

Type	Source	Management
Anterior (90%)	Kiesselbach plexus — Little's area	Digital pressure, cauterization, anterior nasal packing
Posterior (10%)	Woodruff plexus / SPA branches	Posterior nasal packing, endoscopic SPA ligation, angioembolization

13.2 Danger Area of Face

Triangle bounded by: Upper lip (base) and nose to glabella (apex)
Veins in this area: Facial vein → Angular vein → Superior ophthalmic vein → Cavernous sinus
Danger: Facial infections/furuncles squeezed → Septic thrombophlebitis → Cavernous sinus thrombosis
Features of cavernous sinus thrombosis: Proptosis, chemosis, ophthalmoplegia, fever, meningism

13.3 CSF Rhinorrhea Sites

Cribriform plate: Most common site — thin, perforated; damaged in head trauma or FESS
Ethmoid roof (fovea ethmoidalis): Second most common; dehiscent bone during FESS
Sphenoid sinus: Via sphenoid roof; trans-sphenoidal surgery complication
Frontal sinus: Posterior wall fracture

MCQ

CSF rhinorrhea test: Beta-2 transferrin in nasal fluid = GOLD STANDARD confirmatory test. Glucose test is unreliable. Halo/Ring sign on gauze/pillow = traditional bedside test.

13.4 FESS Anatomy

13.4.1 Surgical Landmarks in FESS

Uncinate process: First structure to be removed (uncinectomy) — opens infundibulum
Ethmoidal bulla: Largest anterior ethmoidal cell — removed to expose posterior ethmoid
Lamina papyracea: Medial orbital wall — lateral limit of safe dissection
Skull base (fovea ethmoidalis): Superior limit — avoid going above it
Ground lamella of middle turbinate: Separates anterior from posterior ethmoid
Basal lamella penetration: Access to posterior ethmoid and sphenoid

13.4.2 Danger Areas in FESS

Structure At Risk	Consequence of Injury
Lamina papyracea	Orbital fat herniation, medial rectus damage, orbital haematoma, orbital cellulitis
Skull base / Cribriform plate	CSF leak, meningitis, intracranial entry
Anterior ethmoidal artery	Arterial haemorrhage, orbital haematoma (blind)
Optic nerve (posterior ethmoid/sphenoid)	Blindness
Internal carotid artery (sphenoid)	Life-threatening haemorrhage

13.5 Septoplasty Anatomy

Incision: Hemitransfixion or Killian's incision at caudal septum
Mucoperichondrial flap raised: Between mucosa and perichondrium of cartilage
Key: Preserve 'L-strut' — dorsal and caudal strut of at least 10 mm each for support
Septal support areas to preserve: Keystone area, caudal septum, anterior septal angle

VIVA

L-strut preservation in septoplasty: Minimum 10 mm dorsal and 10 mm caudal strut must be preserved to prevent saddle nose and loss of nasal tip support.

13.6 Lacrimal Drainage Anatomy

Nasolacrimal duct: Drains tears from lacrimal sac → inferior meatus (Hasner's valve)
Hasner's valve: Mucosal fold at terminal end of nasolacrimal duct
Failure to open at birth → congenital nasolacrimal duct obstruction → epiphora in infants
DCR (Dacryocystorhinostomy): Creates surgical opening between lacrimal sac and nasal cavity — window made in lacrimal bone medial to middle turbinate attachment

SECTION 14 | Radiological Anatomy of the Nose

14.1 CT PNS Anatomy

Coronal CT — Key Structures

OMC components: Uncinate process, ethmoidal bulla, hiatus semilunaris, infundibulum — best seen on coronal cuts
Skull base anatomy: Fovea ethmoidalis and cribriform plate depth
Lamina papyracea: Medial orbital wall — look for breach
Turbinates and meatuses: Inferior, middle, superior turbinate relation to meatuses
Septal deviation: Direction, severity, associated spur

14.2 Keros Classification (Depth of Olfactory Fossa)

VERY HIGH YIELD MCQ

Keros classification determines surgical risk during FESS — deeper olfactory fossa = higher risk of intracranial entry.

Keros Type	Depth of Olfactory Fossa	Surgical Risk
Type I	1–3 mm	Lowest risk
Type II	4–7 mm	Moderate risk
Type III	8–16 mm	HIGHEST RISK — cribriform plate forms a deep cleft

14.3 Anatomical Variations on CT PNS

Variant		Description	Clinical Importance
Agger nasi cell		Most anterior ethmoidal cell — anterior to frontal recess	May obstruct frontal sinus drainage
Haller cell (infraorbital cell)		Ethmoidal cell extending below orbital floor, lateral to maxillary ostium	May obstruct maxillary sinus drainage; at risk during FESS
Onodi cell (sphenoethmoidal cell)		Posterior ethmoidal cell extending lateral/superior to sphenoid sinus	Optic nerve and ICA may run through it — HIGH RISK during FESS
Concha bullosa		Pneumatization of middle turbinate	Commonest variant; may obstruct OMC → sinusitis
FAVORITE MCQ	ONODI CELL (sphenoethmoidal cell): The optic nerve and internal carotid artery may pass through it — most DANGEROUS anatomical variant in FESS. Missed on routine CT — must specifically look for it.

SECTION 15 | Master Comparison Tables

15.1 Bones of External Nose

Bone	Contribution
Nasal bones (paired)	Bony vault — upper 1/3 of external nose
Frontal process of maxilla	Lateral nasal wall support
Nasal process of frontal bone	Root of nose

15.2 Cartilages of the Nose

Cartilage	Location	Key Role
Septal (quadrangular)	Anterior nasal septum	Main septal support; tip support
Upper lateral (ULC) x2	Middle vault	Forms internal nasal valve with septum
Lower lateral (LLC) x2	Tip and ala	Tip shape and support
Sesamoid	Between ULC and LLC	Accessory support

15.3 Little's Area vs Woodruff Plexus

Feature	Little's Area / Kiesselbach	Woodruff Plexus
Location	Anteroinferior septum	Posterior inferior meatus
Arteries	5 anastomosing vessels	SPA + ascending pharyngeal
Type of epistaxis	Anterior — commonest (90%)	Posterior — severe (10%)
Age group	Children, young adults	Elderly, hypertensives
Management	Pressure, cautery, anterior pack	Posterior pack / SPA ligation

15.4 Sinus Drainage Pathways

Sinus	Drainage Site	Meatus
Frontal sinus	Frontal recess	Middle meatus
Maxillary sinus	Natural ostium → infundibulum	Middle meatus
Anterior ethmoid	Anterior infundibulum	Middle meatus
Middle ethmoid (bulla)	Direct into middle meatus	Middle meatus
Posterior ethmoid	Superior meatus	Superior meatus
Sphenoid sinus	Sphenoethmoidal recess	Above superior turbinate
Nasolacrimal duct	Inferior meatus	Inferior meatus

15.5 FESS Danger Areas and Consequences

Structure	Risk / Consequence
Lamina papyracea	Orbital fat herniation, medial rectus injury, blindness
Anterior ethmoidal artery	Retraction → orbital haematoma → visual loss
Cribriform plate	CSF leak, meningitis, intracranial injury
Optic nerve	Blindness — specially at Onodi cell
ICA	Catastrophic haemorrhage

15.6 Nasal Glioma vs Encephalocele vs Dermoid

Feature	Nasal Glioma	Encephalocele	Nasal Dermoid
CSF connection	NO	YES	NO (may extend)
Transillumination	No	Yes	No
Furstenberg sign	Negative	POSITIVE	Negative
Increase with Valsalva	No	Yes	No
Contents	Glial tissue	Brain + meninges	Skin, hair, sebaceous
Treatment	Surgical excision	Neurosurgery + ENT	Complete excision with sinus tract

15.7 Keros Classification Summary

Type	Depth	Risk Level
Type I	1–3 mm	Low — short lateral lamella
Type II	4–7 mm	Moderate
Type III	8–16 mm	HIGH — longest lateral lamella; most intracranial entry risk

SECTION 16 | High-Yield Exam Pearls

16.1 Anatomy Must-Know Facts

⭐ ANATOMY PEARLS — MOST COMMON MCQs

External nose: upper 1/3 = bony; lower 2/3 = cartilaginous
Keystone area = junction of nasal bones + ULC + septal cartilage — most important support
Internal nasal valve angle: ULC + septum = 10–15°; narrowing → nasal obstruction
Inferior turbinate = separate bone; middle and superior turbinate = parts of ethmoid
Nasolacrimal duct opens into INFERIOR MEATUS (Hasner valve)
Sphenoidal sinus opens into SPHENOETHMOIDAL RECESS
Uncinate process = FIRST structure removed in FESS
Prussak space equivalent in FESS = OMC obstruction site = most common cause of sinusitis
24-12-6 rule: AEA = 24 mm from lacrimal crest; PEA = 12 mm behind AEA; optic canal = 6 mm behind PEA
SPA = MAIN blood supply to nasal cavity; enters through sphenopalatine foramen
Vidian nerve = GSPN + deep petrosal nerve → pterygopalatine ganglion
Keros type III = deepest olfactory fossa = HIGHEST surgical risk
ONODI CELL = most dangerous anatomical variant in FESS (optic nerve/ICA in wall)

16.2 Embryology Must-Know Facts

⭐ EMBRYOLOGY PEARLS

External nose from: MEDIAL nasal process (philtrum, columella) + LATERAL nasal process (ala, lateral wall)
Nasal septum from medial nasal process + nasal capsule (mesoderm)
Hard palate: Primary palate (premaxilla, week 5-6) + Secondary palate (lateral palatine processes, week 7-8)
Choanal atresia: Failure of rupture of bucconasal membrane; BONY (90%), UNILATERAL (60%)
CHARGE syndrome: Choanal atresia + Coloboma + Heart + Retarded growth + Genital + Ear defects
Furstenberg sign positive in ENCEPHALOCELE; negative in nasal glioma and dermoid
Nasal dermoid may have intracranial extension via cribriform plate → must get MRI before excision

16.3 Physiology Must-Know Facts

⭐ PHYSIOLOGY PEARLS

Nasal cycle: Alternating congestion-decongestion of turbinates; 2–6 hour cycle; regulated by hypothalamus
Ciliary beat frequency: 1000 beats/minute; posteriorly directed
Kartagener syndrome: Dynein arm defect → immotile cilia → sinusitis + bronchiectasis + situs inversus
EAC amplifies 2000–4000 Hz (nasal cavity: humidifies, filters, warms to 32-37°C)
SPA ligation = endoscopic treatment for posterior epistaxis
Anterior epistaxis 90% from Kiesselbach plexus; posterior 10% from Woodruff plexus

16.4 Clinical Pearls

⭐ CLINICAL PEARLS — VIVA FAVOURITES

Septal perforation: anterior = trauma/cocaine/Wegener; posterior = syphilis/TB
Saddle nose deformity: Loss of septal cartilage support (trauma, syphilis, Wegener, cocaine abuse, over-aggressive septoplasty)
L-strut in septoplasty: Preserve ≥10 mm dorsal and ≥10 mm caudal strut
DNS surgery: Septoplasty preferred over SMR (submucous resection) — preserves more cartilage
Myiasis of nose: Most common species = Cochliomyia hominivorax; Tx = manual removal + ivermectin
Rhinoscleroma: Klebsiella rhinoscleromatis; 4 stages = Catarrhal → Atrophic → Granulomatous (Mikulicz cells) → Sclerotic (Russel bodies)
Atrophic rhinitis: Primary (Klebsiella ozaenae) = ozaena; Secondary = post-op, trauma
CSF rhinorrhea best confirmed by BETA-2 TRANSFERRIN electrophoresis

SECTION 17 | Important Diagrams & Figures

17.1 External Nose Diagrams

Image 1 — Surface Anatomy of Nose

Labeled diagram showing: Root, dorsum, tip, ala, columella, nares, alar-facial groove
Cosmetic subunits: 9 subunits outlined on frontal view
Reference: Dhingra — External Nose Chapter; Logan Turner Fig. 1.1

Image 2 — Osteocartilaginous Framework

Lateral view: Nasal bones, frontal process of maxilla, ULC, LLC, septal cartilage
Keystone area highlighted at nasal bone-ULC-septal junction
Internal nasal valve angle marked between ULC and septum
Reference: Cottle diagram of nasal framework

17.2 Nasal Septum Figures

Image 3 — Nasal Septum Anatomy

Medial wall showing: Septal cartilage, perpendicular plate of ethmoid, vomer, maxillary and palatine crests
Blood supply overlay: 5 arteries of Kiesselbach plexus highlighted at Little's area
DNS patterns: C-shaped, S-shaped, spur, crest — labeled

17.3 Lateral Wall & FESS Diagrams

Image 4 — Lateral Wall of Nose

Three turbinates and meatuses labeled: Superior, middle, inferior
Openings into meatuses: nasolacrimal duct (inferior), frontal/maxillary/ethmoid (middle), posterior ethmoid (superior), sphenoid sinus (sphenoethmoidal recess)

Image 5 — Osteomeatal Complex

Coronal view: Uncinate process, ethmoidal bulla, hiatus semilunaris, infundibulum
Drainage arrows from maxillary and frontal sinuses through OMC

Image 6 — Ground Lamella and Frontal Recess

Ground (basal) lamella of middle turbinate separating anterior from posterior ethmoid
Frontal recess with agger nasi cell relationship
Anterior and posterior fontanelles labeled

17.4 Vascular & Nerve Supply Diagrams

Image 7 — Blood Supply of Nose

Sagittal section: AEA and PEA from superior (internal carotid system)
SPA, greater palatine, superior labial (external carotid system) from inferior
Kiesselbach plexus on anteroinferior septum with all 5 vessels meeting
Woodruff plexus on posterior inferior meatus labeled

Image 8 — Vidian Nerve and Pterygopalatine Ganglion

Course: Superior salivatory nucleus → facial nerve → GSPN + deep petrosal nerve → vidian nerve → PTG → nasal branches
Olfactory pathway: Olfactory mucosa → cribriform plate → olfactory bulb → olfactory tract → cortex

17.5 Applied Anatomy Figures

Image 9 — FESS Landmarks on Coronal CT

OMC components highlighted on coronal CT: Uncinate, bulla, infundibulum
Lamina papyracea, skull base (fovea ethmoidalis), cribriform plate depth (Keros classification)

Image 10 — Anatomical Variants

Concha bullosa — pneumatized middle turbinate on CT
Haller cell — infraorbital ethmoidal cell on coronal CT
Onodi cell — posterior ethmoid extending lateral to sphenoid; optic nerve/ICA relation

Image 11 — Embryology of Nose and Palate

Development of medial and lateral nasal processes
Palatal shelf fusion diagram
Choanal development and atresia site

17.6 Histopathology & Microbiology

Image 12 — Respiratory & Olfactory Mucosa

H&E: Respiratory mucosa — pseudostratified ciliated columnar epithelium with goblet cells
H&E: Olfactory mucosa — bipolar receptor cells, supporting cells, basal cells
EM: Ciliary ultrastructure — 9+2 arrangement

Image 13 — Special Histology

Goblet cells: PAS stain showing mucin-filled cells
Venous sinusoid: Erectile tissue in inferior turbinate
Rhinoscleroma: Mikulicz cells (large macrophages with Klebsiella) and Russell bodies (degenerate plasma cells)