Sections Through Mouth and Jaw
The structures illustrated and discussed individually in the preceding pages are shown in these cross sections, one axial, the other coronal, in their mutual topographic relationships. The cheek is formed essentially by the buccinator muscle and its fascia, with the skin and its appendages, including fat, glands, and connective tissue, covering it on the outside and the oral mucosa on the inside.
The continuity of the oral and oropharyngeal wall, as it becomes visible in this cross section, may attain some practical significance in abscess formation and other pathologic processes. One should realize that the buccinator muscle is separated only by the small fascial structure, the pterygomandibular raphe, from the superior pharyngeal constrictor muscle, which constitutes the most substantial component of the oropharyngeal wall. The thin pharyngeal fascia, creating by the looseness of its structure a retropharyngeal space, separates the posterior wall of the pharynx from the vertebral column and prevertebral muscles.
The tonsillar bed, as it lies between the palatoglossal and palatopharyngeal arches, is easier to comprehend in a cross section.
Supplementing the picture of the external aspect of the parotid gland, the cross section demonstrates the thin medial margin of the gland and its relation to the muscles arising from the styloid process (stylohyoid, stylopharyngeus, and styloglossus muscles), the internal jugular vein, and the internal carotid artery. Of further note is the closeness of the most medial part of the parotid gland to the lateral wall of the pharynx and the location within the glandular substance of the retromandibular vein (beginning above the level of the cross section by the confluence of the superficial temporal and maxillary veins), the facial nerve, and the external carotid artery, which latter divides higher up, but still within the gland, into the superficial temporal and maxillary arteries.
The frontal or coronal section of the tongue brings into view the mutual relationships of its muscular components, particularly the lingual septum dividing the tongue into symmetric halves. The lingual artery courses medial to the genioglossus muscle, whereas the main lingual vein, the hypoglossal and lingual nerves, and the duct of the submandibular gland lie lateral to the genioglossus and medial to the mylohyoid muscle. Located inferior and lateral to the latter muscle is the main body of the submandibular gland. Its lateral margin touches the mandible, only separated from it at the level of the section by the facial artery. On the deep surface of the mylohyoid muscle one also finds the posterior end of the sublingual salivary gland in a location that would be occupied by the deep process of the submandibular gland in a section slightly more posteriorly. As the result of the crossings of the lingual nerve and subman- dibular duct, the apparent relationship of these two structures in the cross section would be reversed if one were to obtain a more anterior section.
The mandibular canal harbors the inferior alveolar artery, vein, and nerve. The intermediate tendon of the digastric muscle passes through the fascial loop that anchors it to the hyoid bone.
With the two reflections one from the inferior surface of the tongue across the floor of the mouth to the gum on the inner aspect of the alveolar process of the mandible, the other from the outer surface of this process to the cheek the lining of the oral cavity by the mucous membrane becomes continuous.