The palate (palatum) consists of two parts. Its anterior two thirds have a bony foundation, palatum osseum (the palatine process of the maxilla and the horizontal plate of the palatine bone); this is the hard palate (palatum durum). The posterior third, the soft palate (palatum molle) is a muscular structure with a fibrous foundation. During quiet breathing through the nose it hangs obliquely downward and separates the oral cavity from the pharynx (Fig. 175). A seam, raphe palati, is seen on the midline of the palate. At the anterior end of the raphe is a row of transverse ridges (about six of ihem), plicae palatinae transversum (rudiments of palatine ridges contribut­ing in some animals to the mechanical treatment of the food). The mucous membrane covering the inferior surface of the hard palate adheres closely to the periosteum by means of dense fibrous tissue. The soft palate {palatum molle) is a duplication of the mucous membrane in which muscles are lodged together with a fibrous plate, the palatine aponeu­rosis, as well as glands (Fig. 176). Its anterior margin is attached to the pos­terior edge of the hard palate, while the posterior part of the soft palate (velum palatinum) extends freely downward and to the back and has on the midline a tongue-like projection, the uvula. Laterally, the soft palate is continuous with folds, or arches. The ante-Tior palatoglossal arch (arcus palatoglossus) passes to the lateral surface of the tongue, the posterior palatopharyngeal arch (arcuspalatopharyngeus) stretches for some distance on the lateral wall of the pharynx. A depression forms between the anterior and posterior arches which lodges the palatine tonsil (tonsilla palatina). Each palatine tonsil is an oval-shaped mass of lymphoid tissue. The tonsil occupies the greater inferior part of a triangular depression between the arches (sinus tonsillaris s. fossa tonsillaris). The vertical dimen­sion of the tonsil is 20 to 25 mm, the anteroposterior 15 to 20 mm, and the transverse dimension 12 to 15 mm. The medial surface of the tonsil is covered with epithelium, has an irregular, nodular, contour, and contains crypts (depressions). The lateral surface is covered by a fibrous capsule separating it from the pharyngeal wall. According to recent data, the entire tonsil is invested in a very thin capsule. The nearest important blood vessel in the facial artery which sometimes (when it is tortuous) comes very close to the pharyngeal wall at this level. This must be borne in mind in operation for removal of the tonsils. The internal carotid artery passes at a distance of about 1 cm from the tonsil. The soft palate is composed of the following muscles. M. palatopharyngeus arises from the aponeurosis of the soft palate and from hamulus pterygoideus, descends to the pharynx in the thickness of arcus palatopharyngeus, and is inserted in the posterior margin of the thyroid cartilage and the pharyngeal wall. It pulls the velum pallatinum downwards and the pharynx upwards, in which case the pharynx becomes shorter and presses the soft palate to the posterior pharyngeal wall. M. palatoglossus, arises on the inferior surface of the soft palate, descends in the thickness of arcus palatoglossus and is inserted on the side of the tongue where it is continuous with m. transversus linguae. It lowers velum palatinum and during this movement both palatoglossal arches become tense and the opening of the fauces is narrowed. M. levator veli palatini originates on the inferior surface of the base of the skull and on the inferior surface of the cartilaginous part of the audi­tory tube and passes downwards and medially to the soft palate. It raises velum palatinum. M. tensor veli palatini arises from spina ossis sphenoidalis and from the lateral surface of the membranous part of the auditory tube, descends vertically, its tendon curves around hamulus processus pterygoidei, turns medially almost at a right angle, and is inserted into the aponeurosis of the soft palate. It tenses velum palatinum in the transverse direction. M. uvulae arises from spina nasalis posterior and from the aponeuro­sis of the soft palate and is inserted in the uvula. It shortens the uvula. The uvula is present only in man because it is necessary to create a condition of air-tightness in the oral cavity, which prevents the jaw from hanging in the erect position of the body. The aperture by means of which the oral cavity communicates with the pharynx is called the fauces, s. isthmus faucium. It is bounded on the sides by the palatoglossal arches, above by the soft palate, and below by the back of the tongue. The palate is supplied with nutrients by a. facialis, a. maxillaris, and a. pharyngea ascendens (branches of a. carotis externa). The veins carrying venous blood from the palate drain into v. facialis. The lymph drains into the submandibular and submental nodes. Innervation of the palate is accomplished by plexus pharyngeus formed by the branches of the ninth and tenth pairs of cranial nerves, truncus sympathicus, nn. palatini, and n. nasopalatinus (second division of the trigeminal nerve). N. vagus innervates all the muscles of the soft palate with the exception of m. tensor veli palatini, which is sup­plied by the third division of the trigeminal nerve. Nn. palatini, n. nasopalatinus, and the ninth pair of cranial nerves are mainly concerned with sensory innervation.