HEAD AND NECK
Dental pantomography The dental pantomogram (see Fig. 1. 15) gives a panoramic image of both dental arches, as well as the mandible, temporomandibular joints and lower maxilla. This study is obtained using special equipment that moves around the patient's face as the radiograph is being taken, mapping out the lower face and jaw in a straight line. Arthrography Arthrography of the temporomandibular joint may also be performed where radio-opaque contrast is injected directly into the synovial spaces under radiographic control. Contrast should not pass from one synovial compartment to the other. THE ORAL CAVITY AND SALIVARY GLANDS The oral cavity (Fig. 1. 20) This forms a passage from the lips to the oropharynx. It is largely filled by the tongue and teeth and is lined by a mucous membrane. The parotid gland opens on to its lateral wall, and the submandibular and sublingual glands open on to its floor. The roof is formed by the hard palate anteriorly and the soft palate posteriorly. The soft palate is a
Fig. 1. 20 Floor of mouth: coronal section.
mobile flap that hangs posteroinferiorly at rest, separating the oro- from the nasopharynx. Two muscles insert into it from the lateral wall of the pharynx - the levator and the tensor veli palatini. These elevate the soft palate during swallowing to prevent reflux into the nose. The uvula hangs from the middle of the soft palate, and two pairs of muscles, the palatoglossus and the palatopharyngeus, run from its base to the tongue and pharynx. These muscles and their overlying mucosa form the anterior and posterior fauces, in whose concavity the palatine tonsils lie. The muscles of the tongue form two groups. The intrinsic group are arranged in various planes and alter the shape of the tongue. The extrinsic group are paired muscles that move the tongue and have attachments outside it. The genioglossus arises from the inner surface of the symphysis menti and fans out to form the ventral surface of the tongue. Its inferior fibres form a tendon that attaches to the hyoid bone. The hyoglossus and chondroglossus are thin sheets of muscle that arise from the hyoid bone and insert into the side of the tongue. The styloglossus passes from the styloid process to the side of the tongue. A median raphe divides the tongue into two halves. The floor of the mouth is formed by other muscles that also support the tongue. The most important is the mylohyoid muscle, which is slung from the mylohyoid line on the inner surface of the mandible to the hyoid bone on either side.
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