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I now have excellent diagrams and comprehensive textbook content to deliver a full, well-illustrated answer on the nasal cavity.

Nasal Cavity - Anatomy

Overview

The nasal cavity is the most superior part of the respiratory tract. It extends from the external nares (nostrils) anteriorly to the posterior choanae, where it becomes continuous with the nasopharynx. The nasal septum divides it into right and left halves. Each half has four walls: floor, roof, lateral wall, and medial wall (septum).

Diagrams

Sagittal section - nose and nasal cavities:

Nose and Nasal Cavities - sagittal section showing conchae, sinuses and nasopharynx

From the SEER Training Atlas - sagittal section showing the three nasal conchae, frontal and sphenoidal sinuses, and nasopharynx.

Lateral nasal wall - bony structure, mucosal appearance, and neurovascular supply (Color Atlas of Human Anatomy):

Lateral nasal wall showing bony structure (A), mucosal appearance (B), and arteries and nerves (C)

Fig. 3.3 - Color Atlas of Human Anatomy, Vol. 2. (A) Bony lateral wall with conchae labeled 4 (superior), 5 (middle), 6 (inferior), with maxilla (1), sphenoethmoidal recess (8), sphenopalatine notch (9). (B) Mucosal appearance with vestibule (10) and conchae. (C) Arterial (red) and nerve (yellow) supply.

Paranasal sinuses (anterior, lateral, and transverse views):

Paranasal sinuses - frontal, ethmoidal, maxillary and sphenoidal in three projections

Fig. 3.5 - Color Atlas of Human Anatomy, Vol. 2. Frontal sinuses (orange), ethmoidal cells (green), sphenoidal sinuses (blue), maxillary sinuses (purple).

Boundaries

Wall	Components
Floor	Palatine process of maxilla (anterior 3/4) + horizontal plate of palatine bone (posterior 1/4)
Roof	Nasal bones + nasal part of frontal bone (anterior), cribriform plate of ethmoid (central/superior), body of sphenoid (posterior)
Lateral wall	Maxilla (anterior), perpendicular plate of palatine bone (posterior), ethmoid (superior)
Medial wall (septum)	Perpendicular plate of ethmoid (upper bony), vomer (lower bony), septal cartilage (anterior)

Lateral Wall - Conchae and Meatuses

Three curved bony shelves project from the lateral wall:

Superior nasal concha - part of the ethmoid; smallest
Middle nasal concha - part of the ethmoid
Inferior nasal concha - a separate independent bone

Each concha overhangs a meatus (passage) of the same name. The meatuses are the key drainage routes:

Meatus	What drains into it
Superior nasal meatus	Posterior ethmoidal cells (1-2 openings)
Sphenoethmoidal recess (above superior concha)	Sphenoidal sinus
Middle nasal meatus	Frontal sinus, maxillary sinus, anterior and middle ethmoidal cells; contains the hiatus semilunaris (curved crevice) bounded by the uncinate process and ethmoidal bulla
Inferior nasal meatus	Opening of the nasolacrimal duct

The function of the conchae is to increase surface area so that inspired air is warmed, humidified, and filtered more effectively.

Nasal Septum (Medial Wall)

The septum has three parts:

Bony part (posterior/inferior): Perpendicular plate of ethmoid (upper) + vomer (lower)
Cartilaginous part: Septal (quadrangular) cartilage
Membranous part: Soft tissue at the anterior tip

The free posterior margin of the vomer forms the medial boundary of each choana.

Mucosal Regions (3 types of epithelium)

Region	Epithelium	Location
Nasal vestibule	Stratified keratinized squamous epithelium (skin)	Within the nostrils, bounded posteriorly by the limen nasi
Respiratory region	Pseudostratified ciliated columnar epithelium with mixed nasal glands	Remainder of nasal cavity (majority)
Olfactory region	Olfactory neuroepithelium	Superior septum, superior turbinate, and upper aspect of middle turbinate

Blood Supply

The nasal cavity has a dual arterial supply:

External carotid artery system (via maxillary artery):

Sphenopalatine artery - main supply to the posterior and inferior lateral nasal wall; also supplies the septum

Internal carotid artery system (via ophthalmic artery):

Anterior ethmoidal artery - anterior and superior lateral wall + superior septum
Posterior ethmoidal artery - posterior superior lateral wall

Kiesselbach's area (Little's area): A 1.5-mm zone of rich capillary anastomosis at the anteroinferior part of the nasal septum (junction of vestibule and nasal cavity). This is the most common site of epistaxis (nosebleeds). It receives contributions from the sphenopalatine, greater palatine, superior labial, and anterior ethmoidal arteries.

Nerve Supply

Sensory innervation (branches of the trigeminal nerve, CN V):

Anterior/superior nasal mucosa: Ophthalmic division (CN V1) - anterior and posterior ethmoidal nerves
Posterior/inferior nasal mucosa: Maxillary division (CN V2) - via the sphenopalatine ganglion

Autonomic innervation:

Parasympathetic (secretomotor - regulates nasal secretions): Preganglionic fibers travel via the greater superficial petrosal nerve → Vidian nerve → synapse in sphenopalatine ganglion → postganglionic fibers to nasal mucosa
Sympathetic (vasoconstriction - regulates turbinate congestion): Postganglionic fibers from the deep petrosal nerve → Vidian nerve → pass through sphenopalatine ganglion (without synapsing) → nasal mucosa

Olfactory (CN I):

Olfactory nerve fibers from the olfactory neuroepithelium pass through the cribriform plate of the ethmoid to synapse in the olfactory bulb.

Clinical Notes

Epistaxis (nosebleeds): Most commonly occur at Kiesselbach's area on the anteroinferior septum. Posterior bleeds arise from the sphenopalatine artery and are more severe.
Sinusitis: Infections spread from nasal mucosa into the paranasal sinuses through their drainage openings. Obstruction of the osteomeatal complex (middle meatus area) is the most common anatomical bottleneck causing recurrent sinusitis.
Septal deviation: A deviated nasal septum is a common anatomical variant that can obstruct airflow, contribute to sinusitis, and affect the nasal cycle.
Concha bullosa: Pneumatisation (air cell formation) within the middle turbinate - a common variant that can obstruct the middle meatus.
Sphenoidal sinus access: Because the roof of the nasal cavity slopes downward anteroposteriorly, surgical dissection progressing posteriorly (during endoscopic sinus surgery) approaches the skull base, which must be recognized to avoid intracranial injury.
Pituitary surgery: The sphenoidal sinus, lying immediately posterior to the nasal cavity, provides the endoscopic transsphenoidal route for pituitary gland surgery.

Sources: Color Atlas of Human Anatomy, Vol. 2 (Internal Organs), p. 174-177; Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 1; Cummings Otolaryngology Head and Neck Surgery.

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