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Other features
nerve. A small part of the tongue near the epiglottis is supplied by the
• The tonsil: a mass of lymphatic tissue lying in the tonsillar fossa
internal laryngeal branch of the vagus nerve.
which, like the rest of the lymphatic system, reaches its maximum size
Since the anterior part of the tongue develops from a pair of lingual
at puberty. Lateral to the tonsil is its fibrous capsule and the superior in the chorda tympani. Posterior one third by the glossopharyngeal
constrictor. It is supplied by the tonsillar branch of the facial artery swellings, the nerves and blood vessels of each side of the tongue do not
but the bleeding that occurs after tonsillectomy is usually from the cross the midline (although some lymphatics do) so that a midline inci-
paratonsillar vein. The pharyngeal tonsil (adenoid) has already sion will not do any serious damage. If the motor supply is cut off on
been mentioned and there is also a lingual tonsil lying in the back of one side, the tongue will diverge to the affected side when protruded
the tongue. owing to the action of genioglossus on the sound side.
• The teeth: the deciduous (milk) teeth comprise two incisors, a
canine and two molars; the last occupy the position of the two pre- The nasal cavity
molars of the permanent teeth. The permanent teeth comprise two The boundaries of the nasal cavity include the:
incisors, a canine, two premolars and three molars. The first milk teeth • Nasal septum: perpendicular plate of the ethmoid, vomer and a large
to erupt are usually the lower central incisors at about 6 months and the plate of cartilage.
first permanent teeth are the first molars at about 6 years. • Lateral wall (Fig. 66.2): maxilla, lacrimal, ethmoid with its superior
and middle conchae, perpendicular plate of the palatine, inferior con-
The tongue cha (a separate bone).
The tongue is divided developmentally and anatomically into an an- • Roof: nasal bones, cribriform plate of the ethmoid, body of the
terior two-thirds and a posterior one third, separated by the sulcus sphenoid.
terminalis, a V-shaped groove with the foramen caecum at the apex • Floor: palatal processes of the maxilla and palatine bones.
(Fig. 66.1). The latter is the site of outgrowth of the thyroglossal duct. The spaces beneath the conchae are the meatuses and the region
In front of the sulcus is a row of vallate papillae. Filiform papillae and above the superior meatus is the spheno-ethmoidal recess.
red, flat-topped fungiform papillae can be seen on the more anterior
parts of the tongue. The paranasal sinuses
• The maxillary sinus: inside the body of the maxilla, it opens into the
Muscles (Fig. 65.3) middle meatus. Since the opening is in the upper part of the sinus it does
• Intrinsic muscles: run in three directions, longitudinally, trans- not drain easily.
versely and vertically. • The frontal sinuses: on each side of the midline, just above the
• Hyoglossus: from the greater horn of the hyoid bone. medial part of the orbit. They drain into the middle meatus.
• Genioglossus: from the genial tubercle on the back of the mandible. • The ethmoidal sinuses: in the body of the ethmoid bone and there-
• Styloglossus: from the styloid process. fore deep to the medial wall of the orbit. Drain into the middle and
The latter three muscles blend in with the intrinsic muscles. superior meatuses.
Genioglossus is especially important as it is inserted along the whole • The sphenoidal sinus: inside the body of the sphenoid. Drains into
length of the tongue so that it is used to protrude the tongue. the spheno-ethmoidal recess.

Nerve supply The nasolacrimal duct
• Motor: hypoglossal nerve. Drains tears from the medial angle of the eye. Drains into the inferior
• Sensory: anterior two-thirds by the lingual nerve; taste fibres travel meatus.

The mouth, palate and nose 147