The Nasal Mucosa

• Mucosa lines the entire nasal cavities except for the vestibule of the nose.
• The nasal mucosa is firmly bound to the periosteum and perichondrium of the supporting structures of the nose.
• It is continuous with the adjoining cavities to which the nasal cavity communicates (e.g., the nasopharynx and paranasal sinuses).

• The inferior 2/3 of the nasal mucosa is called the respiratory area and air passing over this is warmed and moistened before it passes into the lungs.
• The superior 1/3 is called the olfactory area.

The Olfactory Area of Nasal Mucosa

• This area contains the peripheral organ of smell.
• Sniffing draws air into this area
• Olfactory receptor cells (from the olfactory nerve, CN I, are located in the mucosa of this area in the nose.

Nerves to the Respiratory Area of Nasal Mucosa

• The inferior 2/3 of the nasal mucosa are supplied chiefly by the trigeminal nerve (CN V).

• The mucous membrane of the nasal septum is supplied chiefly by the nasopalatine nerve, a branch of the maxillary nerve (CN V²).
• Its anterior portion is supplied by the anterior ethmoidal nerve (a branch of the nasociliary nerve) which is derived from the ophthalmic nerve (CN V¹).

• The lateral walls of the nasal cavity are supplied by branches of the maxillary nerve (CN V²); the greater palatine nerve, and the anterior ethmoidal nerve.

Arteries of the Nasal Mucosa

• The blood supply of the mucosa of the nasal septum is derived mainly from the maxillary artery.

• The sphenopalatine artery, a branch of the maxillary, supplies most of the blood of the nasal mucosa.
• It enters by the sphenopalatine foramen and sends branches to the posterior regions of the lateral wall and to the nasal septum.

• The greater palatine artery, also a branch of the maxillary, passes through the incisive foramen to supply the nasal septum.

• The anterior and posterior ethmoidal arteries, branches of the ophthalmic artery, supply the anterosuperior part of the mucosa of the lateral wall of the nasal cavity and nasal septum.

• Three branches of the facial artery (superior labial, ascending palatine, and lateral nasal) also supply the anterior parts of the nasal mucosa.

Veins of the Nasal Mucosa

• The veins of the nasal mucosa form a venous network of plexus in the connective tissue of the nasal mucosa.
• Some of the veins open into the sphenopalatine vein and drain to the pterygoid plexus.
• Others join the facial and infraorbital veins.
• Some empty into the ophthalmic veins and drain into the cavernous sinus.

The Frontalis Muscle

• The frontalis muscle is part of the scalp muscle called the occipitalfrontalis.
• The frontalis elevates the forehead, giving the face a surprised look, and produces transverse wrinkles in the forehead when one frowns.

->The sides and base of the skull are formed partly by these bones.
->Each bone consists of four morphologically distinct parts that fuse during development (squamous, petromastoid, and tympanic parts and the styloid process).
->The flat squamous part is external to the lateral surface of the temporal lobe of the brain.
->The petromastoid part encloses the internal ear and mastoid cells and forms part of the base of the skull.
->The tympanic part contains the bony passage from the auricle (external ear), called the external acoustic meatus. The petromastoid part also forms a portion of the bony wall of the tympanic cavity (middle ear). The meatus and tympanic cavity are concerned with the transmission of sound waves.
->The slender, pointed styloid process of the temporal bone gives attachment to certain ligaments and muscles (e.g., the stylohyoid muscle that elevates the hyoid bone).
->The temporal bone articulates at sutures with the parietal, occipital, sphenoid, and zygomatic bones.
->The zygomatic process of the temporal bone unites with the temporal process of the zygomatic bone to form the zygomatic arch. The zygomatic arches form the widest part of the face.
->The head of the mandible articulates with the mandibular fossa on the inferior surface of the zygomatic process of the temporal bone.
->Anterior to the mandibular fossa is the articular tubercle.
->Because the zygomatic arches are the widest parts of the face and are such prominent facial features, they are commonly fractured and depressed. A fracture of the temporal process of the zygomatic bone would likely involve the lateral wall of the orbit and could injure the eye.

The Paranasal Sinuses

• These sinuses are air-filled extensions of the respiratory part of the nasal cavity.
• They are in the following bones, frontal, ethmoid, sphenoid and the maxilla.

The Frontal Sinuses

• These are located between the outer and inner tables of the frontal bone, posterior to the superciliary arches.

The Ethmoidal Sinuses

• These comprise of several small cavities, called ethmoidal air cells, within the ethmoidal labyrinth (G. labyrinthos, a maze) of the lateral mass of the ethmoid bone.

The Sphenoidal Sinuses

• These occupy a variable amount in the body of the sphenoid bone and may extend into the wings.

The Maxillary Sinuses

• These are the largest pair of paranasal sinuses.
• They are pyramidal-shaped cavities that may occupy the entire bodies of the maxillae.

The Lateral Wall of the Orbit

• This wall is thick, particularly its posterior part, which separates the orbit from the middle cranial fossa.
• The lateral wall is formed by the frontal process of the zygomatic bone and the greater wing of the sphenoid bone.

• Anteriorly, the lateral wall lies between the orbit and the temporal fossa.

• The lateral wall is partially separated from the roof by the superior orbital fissure.

• Bones begin to form during the eighth week of embryomic life in the fibrous membranes (intramembranous ossification) and hyaline cartilage (endochondral ossification)