Publisher Summary

This chapter illustrates the anatomic section of frontal head. This is the most anterior coronal section. It shows the nasal bones above and, below them, the upper half of the nasal fossa formed by the frontal processes of the maxilla. It also shows the premaxilla. The upper portion of the bony nasal septum formed by the perpendicular plate of the ethmoid is seen in this section. The lower half of the bony septum in this section is cartilaginous. The upper half of the nasal fossa is formed by the nasal bones and the frontal processes of the maxilla; the lower half is formed by the body of the maxilla. The most anterior section of the inferior turbinate bones and the premaxilla are seen. In the midline on the inferior surface of the premaxilla is the incisive foramen. The inferior part of the nasal septum is formed by the incisive crest, the most anterior part of the nasal crest of the maxilla. The nasal crest forms the most inferior portion of the bony nasal septum. The anterior border of the vomer articulates with the incisive crest. In all sections posterior to this one, the inferior portion of the bony nasal septum is formed by the vomer. The supraorbital nerve is a branch of the frontal nerve, which is a branch of the ophthalmic nerve. It is a sensory nerve that innervates the upper eyelid, the scalp of the frontal region, and the parietal region almost as far as the lambdoid suture.

Fig. 1

Anatomic Section

This is the most anterior coronal section. It shows the nasal bones above and, below them, the upper half of the nasal fossa formed by the frontal processes of the maxilla. It also shows the premaxilla. The upper portion of the bony nasal septum formed by the perpendicular plate of the ethmoid is seen. The lower half of the bony septum in this section is cartilaginous.

Tomogram

The anatomic section is very far anterior. Only a small portion of the nose and the most anterior part of the soft tissue of the face are actually in this section. On the other hand, the tomogram appears quite complex. The only structures in focus are the bony nasal septum formed by the perpendicular plate of the ethmoid, the nasal bones, the frontal processes of the maxilla forming the upper half of the nasal fossa, and the premaxilla. All the other shadows seen in this tomogram are parasite shadows derived from structures outside the plane of focus. The same number of out-of-focus parasite shadows are present on every tomographic section. However, it is only when few structures are actually in focus that these out-of-focus parasite shadows become so obvious. When many structures are in focus, the parasite shadows are less obvious.

Anatomic Section

Almost the entire nasal fossa is demonstrated. The upper half of the nasal fossa is formed by the nasal bones and the frontal processes of the maxilla; the lower half is formed by the body of the maxilla. The most anterior section of the inferior turbinate bones and the premaxilla are seen. In the midline on the inferior surface of the premaxilla is the incisive foramen. The incisive foramen is formed by the conjunction of the incisive canals. The incisive canals arise on each side of the nasal septum at the junction of the premaxilla and postmaxilla. The incisive canals and incisive foramen transmit the terminations of the sphenopalatine arteries which anastomose with the terminal branches of the greater palatine artery. They also transmit the terminal branches of the nasopalatine nerve. The sphenopalatine artery is the terminal branch of the internal maxillary artery. It passes into the nose through the sphenopalatine foramen, passing to the septum and running forward and downward on the vomer to the incisive foramen. The greater palatine artery, a branch of the descending palatine artery, originates on the inferior surface of the palate at the greater palatine foramen and runs forward to the incisive foramen. The nasopalatine nerve is derived from the sensory branches of the sphenopalatine nerve, a branch of the maxillary nerve. The fibers forming the nasopalatine nerve pass medial through the sphenopalatine foramen and follow the same course as the sphenopalatine artery. Above the nose is the most anterior section of the frontal bone.

Tomogram

The tomographic section appears much more complex than the anatomic section to which it corresponds. Again, this is because of parasite shadows. The nasal fossa and the upper half of the nasal septum, the bony portion, are clearly in focus. The incisive foramen is seen below in the premaxilla.

Anatomic Section

The incisive foramen is at the midline; to each side and above are the incisive canals. The inferior part of the nasal septum is formed by the incisive crest, the most anterior part of the nasal crest of the maxilla. The nasal crest forms the most inferior portion of the bony nasal septum. The anterior border of the vomer articulates with the incisive crest. In all sections posterior to this one, the inferior portion of the bony nasal septum is formed by the vomer. Superior to the incisive crest is the cartilaginous nasal septum, and superior to that, the perpendicular plate of the ethmoid. The roof of the nasal fossa is formed by the nasal bone. That portion of the nasal fossa inferior and lateral to the inferior turbinate is the inferior nasal meatus. In the frontal bone, the most anterior section of the frontal sinuses is seen. The articulation between the frontal bone and the frontal process of the maxilla forms the frontomaxillary suture. The supraorbital notch transmits the supraorbital artery and nerve. The supraorbital artery arises from the ophthalmic artery in the orbit. It supplies the periosteum in the roof of the orbit, the lateral palpebral and superior rectus muscles, the frontal diploë and the frontal sinuses, the pulley of the superior oblique muscle, and the upper eyelid. The supraorbital nerve is a branch of the frontal nerve, which is a branch of the ophthalmic nerve. It is a sensory nerve that innervates the upper eyelid, the scalp of the frontal region, and the parietal region almost as far as the lambdoid suture.

Tomogram

The frontal processes of the maxillae, the nasal bones, the nasal septum including the incisive crest and the perpendicular plate of the ethmoid, and the root of the attachment of the inferior turbinate are seen. Very faintly seen is the incisive canal.

Anatomic Section

The bony nasal septum is still incomplete. Its inferior portion is formed by the vomer, and its superior portion by the perpendicular plate of the ethmoid. On the lateral wall of the nasal fossa just inferior to its roof is a ridgelike elevation, the agger nasi. The left agger nasi is pneumatized by a frontoethmoid air cell. Inferior to the agger nasi and anterior to the middle turbinate is the nasal atrium, which frequently encroaches upon the lumen of the maxillary sinus by causing the nasal or medial wall of the sinus to be convex laterally. The narrow...