Nasal Cavity

Nasal Cavity and Paranasal Sinuses

I. Nasal Cavity

• Opens on the face through the anterior nasal apertures (nares, or nostrils) and communicates with the nasopharynx through a posterior opening, the choanae.
• Has a slight dilatation inside the aperture of each nostril, the vestibule , which is lined largely with skin containing hair, sebaceous glands, and sweat glands.

A. Roof

• Is formed by the nasal, frontal, ethmoid (cribriform plate) , and sphenoid (body) bones. The cribriform plate transmits the olfactory nerves.

B. Floor

• Is formed by the palatine process of the maxilla and the horizontal plate of the palatine bone.
• Contains the incisive foramen , which transmits the nasopalatine nerve and terminal branches of the sphenopalatine artery.

C. Medial wall (nasal septum)

• Is formed primarily by the perpendicular plate of the ethmoid bone, vomer, and septal cartilage.
• Is also formed by processes of the palatine, maxillary, frontal, sphenoid, and nasal bones.

D. Lateral wall

• Is formed by the superior and middle conchae of the ethmoid bone and the inferior concha.
• Is also formed by the nasal bone, frontal process and nasal surface of the maxilla, lacrimal bone,
• perpendicular plate of the palatine bone, and medial pterygoid plate of the sphenoid bone.
• Contains the following structures and their openings:

• Sphenoethmoidal recess : opening of the sphenoid sinus.
• Superior meatus : opening of the posterior ethmoidal air cells.
• Middle meatus : opening of the frontal sinus into the infundibulum, openings of the middle
• ethmoidal air cells on the ethmoidal bulla , and openings of the anterior ethmoidal air cells and maxillary sinus in the hiatus semilunaris.
• Inferior meatus : opening of the nasolacrimal duct.
• Sphenopalatine foramen : opening into the pterygopalatine fossa; transmits the sphenopalatine artery and nasopalatine nerve.

II. Subdivisions and Mucous Membranes

A. Vestibule

• Is the dilated part inside the nostril that is bound by the alar cartilages and lined by skin with hairs.

B. Respiratory region

• Consists of the lower two thirds of the nasal cavity.
• Warms, moistens, and cleans incoming air with its mucous membrane.

C. Olfactory region

• Consists of the superior nasal concha and the upper one third of the nasal septum.
• Is innervated by olfactory nerves, which convey the sense of smell from the olfactory cells and enter the cranial cavity through the cribriform plate of the ethmoid bone to end in the olfactory bulb.

III. Blood Supply to the Nasal Cavity

• Occurs via the following routes:
  

• The lateral nasal branches of the anterior and posterior ethmoidal arteries of the ophthalmic artery.
• The posterior lateral nasal and posterior septal branches of the sphenopalatine artery of the maxillary artery.
• The greater palatine branch (its terminal branch reaches the lower part of the nasal septum through the incisive canal) of the descending palatine artery of the maxillary artery.
• The septal branch of the superior labial artery of the facial artery and the lateral nasal branch of the facial artery.

IV. Nerve Supply to the Nasal Cavity

• A. SVA (smell) sensation is supplied by the olfactory nerves for the olfactory area.
• B. GSA sensation is supplied by the anterior ethmoidal branch of the ophthalmic nerve; the nasopalatine, posterior-superior, and posterior-inferior lateral nasal branches of the maxillary nerve via the pterygopalatine ganglion; and the anterior-superior alveolar branch of the infraorbital nerve.

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