د . سيف (م 9) Human Anatomy

The Nasal Cavity The nasal cavity consists of right and left halves that are separated by a nasal septum. The cavity opens, anteriorly, on the front of the skull through the anterior nasal aperture; and, posteriorly, on the base of the skull just above the posterior edge of the bony palate, through the right and left posterior nasal apertures.

Boundaries of the nasal cavity: ≡ The lateral wall is formed by meeting of several bones. The bones taking part in forming it are (a) the medial surface of the maxilla, (b) the palatine bone; (c) the lacrimal bone; (d) the inferior nasal concha; and (e) the ethmoid bone. ≡ The floor of the nasal cavity is formed anteriorly by the palatine process of the maxilla, and posteriorly by the horizontal plate of the palatine bone.

≡ The roof of the nasal cavity is formed by several bones ≡ The roof of the nasal cavity is formed by several bones. From front to back these are parts of the nasal bone, the frontal bone, the cribriform plate of the ethmoid and the anterior surface of the body of the sphenoid bone. ≡ The medial wall or nasal septum is formed in its upper part by the perpendicular plate of the ethmoid bone, and its lower part by the vomer. Anteriorly, there is a gap in the septum that is filled in by cartilage.

Lateral wall of the nasal cavity

medial wall of the nasal cavity

Nasal Conchae Projecting out of the lateral walls of the nasal cavity are curved shelves of bone. They are called conchae (or turbinates). The are three conchae – inferior, middle and superior. They project into the nasal cavity, creating four pathways for the air to flow. These pathways are called meatuses: -Inferior meatus: Lies between the inferior concha and floor of the nasal cavity. -Middle meatus: Lies between the inferior and middle concha. -Superior meatus: Lies between the middle and superior concha. -Spheno-ethmoidal recess: Lies superiorly and posteriorly to the superior concha.

Paranasal Sinuses Paired air spaces in certain bones of the skull are called paranasal sinuses. These sinuses are named according to the bones in which they are found; thus, there are the maxillary, frontal, sphenoidal, and ethmoidal sinuses. Each sinus communicates via drainage ducts within the nasal cavity on its own side. ### Paranasal sinuses may help to warm and moisten the inspired air. These sinuses are responsible for some sound resonance. The most important function is to decrease the weight of the skull while providing structural strength.

A. FRONTAL SINUSES 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. Frontal sinuses are usually detectable in children by 7 years of age. The right and left sinuses each drain through a frontonasal duct into the ethmoidal infundibulum, which opens into the semilunar hiatus of the middle nasal meatus. ***The frontal sinuses are innervated by branches of the supra-orbital nerves (CN V1).

B. ETHMOIDAL CELLS The ethmoidal cells (sinuses) are small invaginations of the mucous membrane of the middle and superior nasal meatus into the ethmoid bone between the nasal cavity and the orbit. The anterior ethmoidal cells drain into the middle meatus through the ethmoidal infundibulum. The middle ethmoidal cells open directly into the middle meatus on or above the bulla ethmoidalis. The posterior ethmoidal cells open directly into the superior meatus. ***The ethmoidal cells are supplied by the anterior and posterior ethmoidal branches of the nasociliary nerves (CN V1).

C. SPHENOIDAL SINUSES The sphenoidal sinuses are located in the body of the sphenoid, but they may extend into the wings of sphenoid. They are unevenly divided and separated by a bony septum. This sinus opens above the superior concha within sphenoethmoidal recess. ***The mucous membrane receives sensory innervation by the posterior ethmoidal nerve (branch of the ophthalmic nerve).

D. MAXILLARY SINUSES The maxillary sinuses are the largest of the paranasal sinuses. They occupy the bodies of the maxillae. Each maxillary sinus drains by one or more openings into the middle meatus of the nasal cavity by way of the semilunar hiatus. ***Innervation of the maxillary sinus is from the anterior, middle, and posterior superior alveolar nerves, which are branches of the maxillary nerve.

Other Apertures in the Nasal Cavity In addition to the anterior and posterior nasal apertures, and the openings of the paranasal sinuses, we see the following openings in the nasal cavity. a. The nasolacrimal canal opens into the inferior meatus. The upper end of this canal is seen in the orbit. b. The sphenopalatine foramen opens behind the superior meatus, just above the posterior end of the middle concha c. The nasal cavity communicates with the anterior cranial fossa through numerous apertures in the cribriform plate of the ethmoid bone. d. In the anterior part of the floor of the nasal cavity there is a funnel shaped opening that leads into the incisive canals that open on the lower surface of the palate.

Innervation of the nose: ☻ General sensation: 1. maxillary nerve, by way of the nasopalatine nerve to the nasal septum. posterior superior lateral nasal and inferior lateral nasal branches of the greater palatine nerve to the lateral wall. 2. ophthalmic nerve by way of the anterior and posterior ethmoidal nerves, branches of the nasociliary nerve.

3. Most of the external nose (dorsum and apex) is also supplied by CN V1 (via the infratrochlear nerve and the external nasal branch of the anterior ethmoidal nerve), but the alae of the nose are supplied by the nasal branches of the infra-orbital nerve (CN V2). ☻ Special sensation The olfactory nerves, concerned with smell, arise from cells in the olfactory epithelium in the superior part of the lateral and septal walls of the nasal cavity. The central processes of these cells (forming the olfactory nerve) pass through the cribriform plate and end in the olfactory bulb, the rostral expansion of the olfactory tract.