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Parotid gland

The parotid gland is the largest of the salivary glands, which include the also-paired submandibular and sublingual glands and numerous small glands in the tongue, lips, cheeks, and palate. Their combined secretion is termed saliva. The parotid, a serous compound tubulo-alveolar gland, is yellowish, lobulated, and irregular in shape. It occupies the interval between the sternomastoid muscle and the mandible.

The parotid gland lies inferior to the zygomatic arch, anteroinferior to the external acoustic meatus, anterior to the mastoid process, and posterior to the ramus of the mandible.

Innervation of parotid gland.

Preganglionic parasympathetic secretomotor fibers (from the glossopharyngeal, tympanic, and lesser petrosal nerves) synapse in the otic ganglion. Postganglionic fibers travel with the auriculotemporal nerve and so reach the gland. Cranial nerves VII and IX communicate, so that secretory fibers to each of the three major salivary glands may travel in both the facial and glossopharyngeal nerves. The sympathetic supply to the salivary glands includes vasomotor fibers.

Parotid duct.

The parotid duct, emerging under cover of the lateral surface, runs anteriorward on the masseter and turns medially to pierce the buccinator. The branching of the duct can be examined radiographically after injection of a radio-opaque medium. The parotid duct, which is palpable, opens into the oral cavity on the parotid papilla opposite the upper second molar tooth

70. The oral cavity: Vestibule, proper oral cavity. The structure of the walls: lips, cheeks, soft palate, blood supply and innervations. The oral cavity is divided into outer, smaller portion, the vestibule, and inner larger part, the oral cavity proper. Vestibule- vest of the mouth is a narrow space boundared externally by the lips and cheeks and internally by the teeth and gums. Numerous labial and buccial glands situated in the submucosa of the lips and cheeks open into the vestibule. 4-5 molar glands situated in buccopharingeal fascia also open into the vestibule. Except the teeth the entire vestibule is lined by mucous membrane. Lips- the lips are fleshy folds lined externally by skin and internally by mucous memb. Each lips is composed of a skin, superficial fascia, the orbicularis oris muscle, the submucosa. The lips bound the oral fissure. They meet laterally at the angles of the mouth. Inner surface is supported by the frenulum. Cheeks(Buccae)- are fleshy flaps, forming a large part of each side of face. They are continuous in front with the lips and junction is indicated by the nasolabial sulcus. Each cheek is composed of: skin, superficial fascia containing some fascial muscles, the parotid duct, mucous molar glands, vessel and nerves,, buccinators covers by buccofaringeal fascia and pierced by parotid duct. Submucosa with mucous glands and mucous membrane. The buccial pad is best developed in infants. Proper oral cavity-It is boundered by the teeth, the gums,, alveolar archs of the jaws. The roof is formed by the hard and soft palate. The roof is occupied by the tongue posteriorly and presents sublingual region anteriorly below the tip of the tongue. Post region communicates with the pharynx through the oropharyngeal isthmus which is bounded superiorly by the soft palate, inf by the tongue, and in each side by the palatoglossal arches. Soft palate- it is a movable, muscular fold, suspended from the post border of the hard palate. The soft palate has 2 surfaces ant-concave and post-convex. S.P-separates the nasopharynx from the oropharynx and often looked upon as traffic controller at the cross roads between the food and air passages. Numerous mucous glandsand some taste buds situated in S.F. Nerve supply-motor nerves-all muscles of he soft palate except the tensor palate are supplied by the pharyngeal plexus. It is derived from accessory nerve. General sensory nerves- are derived from the middle and post palatine nerves, which are branch of maxillary nerve and glossopharyn nerve.Special sensory n-carry taste sensations from the oral surface are contained in the lesser plalatine nerves. Secretomotor n-derived from sup salivatory nucleus through greater petrosal nerve. Blood supply: Arteries- Greater palatine branch of maxillary art, ascending palate branch of facial art and palatine branch of ascending pharyngeal art. Veins: They pass to the pterygoid and tonsillar plexus of veins.

71. Teeth(milk and permanent)structure, time of eruption, blood and nerve supply, lymphatic drainage. Lateral ventricles of the brain^ walls, communications, choroids plexus of ventricles. The teeth form a part of masticatory apparatus and are fixed to the jaws. The teeth of th e 1-st set are known as milk, or deciduous teeth, and second set as permanent teet The milk are 20 in number. In each half of each jaw there are 2 incisors, 1 canine, and 2 molars. He permanent are 32 in number, and consist of 2 incisirs, 1 canine, 2 premolars, 3 molars ineach half of each jaws. Parts: each of t has 3 parts: a crown, projecting above the gum, a neck, between the crown and root and surrounded by the gum. Structure-each t. composed of:the pulp in the center, the dentine surrounding the pulp, and an enamel covering the projecting part of dentne of crown, cementum surrounding the embedded part of the dentine, and the periodontal membrane.The incisor, canines and premolars have single roots, with the execption of the 1-st upper premolar which has a bifid root. The upper molars has 3 roots. Eruption of teeth-milk begin to erupt at about the 6 month and have erupted by the end of the second year. The approximate ages of eruption: lower central incisors-6month, upper central inc-7month, lateral inc-8-9month, 1-st molar-1year, canines-18 month, 2-nd molar-2 years. Permanent-1-st molar-about 6 years, med inc-7year, later-8, 1-st premolar-9, seond-10, canines-11, 2-nd molar-12 and 3-rd molar-17-25 or even later. Nerve supply-the pulp and periodontal membrane have the same nerve supply which is different from that of the overlying gum. The upper teeth are supplied by the post sup alveolar, middle sup alveolar, and ant sup alveolar nerves. The lower teeth are supplied by the inf aveolar nerve. Lymphatic: drain into the upper deep cervical and retropharyngeal lymph nodes. Lateral ventricle- the ateral ventricles are 2 irregular cavities situated one in teach cerebral hemisohere. Each lat.ventricle communicates with the third ventricle through an interventricular foramen. Each lateral ventricle cosist of central part, three horns(ant post inf). Central part-extends from the interventricular foramen to the selenium of the corpus callosum. Ant horn-lies in front of the interventricular foramen and extends into the frontal lobe. It is directed forwards, laterally, and downwards, and it is triangular on cross section. Post horn- lies behind the splenium of the corpus callosum and extends into the occipital lobe. It is variable in size and may be absent. It is directed backward and medially.

72. The tongue: structure, functions, blood and nerve supply and lymph drainage. The tongue is the muscular organ situated in the floor of the mouth. It is associated with the functions of taste, speech, mastication, and deglutition. It has an oral part that lies in the mouth and pharyngeal part that lies in the pharynx. The oral and pharyngeal parts separated by a V-shaped sulcus, the sulcus terminalis. Tong has root, tip, body, which has a curved upper surface or dorsum,and an inf surface. The root is attached to the mandible above and the hyoid bone below. The tip of tongue forms the ant free end which lies behind the upper incisor teeth. The sup.surfse of the oral part show a median furrow and is covered with papillae which make it rough. Inf-covered with smooth mucous membrane.Papillae of tongue-1-papilla valate- 8-12 in number, situated infront of sulcus terminals. 2-papilla fungiforme-are numerous near the tip and margins of the tongue. 3-papillae filiforme- cover dorsum of the tongue and give t belvete. Arterial supply – it is chiefly derived frm the lingual artery a branch of the externalcarotid art. The root of the tongue is also supplied by the tonsillar and ascending pharyngeal rteries. Venous drainage -2 venae comites accompany the lingua art. And one vena comitans accompanies the hypoglossal nerve. The deep lingual vein is the largest and principal vein of tongur. These veins unite at the post.border of the hyoglossus to form the lingual vein or in the internal jugulat vein. Nerve Supply –motor nerves-all the intrinsic and extrinsic muscles except the palatoglossus are supplied by the hypoglossal nerve. Sensory nerves-the lingual nerve is the nerve of general sensation and the chorda tympani is the nerve of tastefor the ant. 2/3 f tongue. The glossopharyngeal n-is for booth general sensation and tase for post 1/3 of tongue. The post most supplied by n.vagus. Lymph - the tip of tongue drains bilaterally to the submental nodes. The right and left halves drain submandibular nodes, the post 1/3 by jugulo-o,ohyoid nodes.

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