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Dr.Hameda abdulmahdi 2nd stage College of Medicine /Dep. of anatomy & histology Oral Cavity The oral cavity is lined with stratified squamous epithelium, which may be keratinized, partially keratinized,or nonkeratinized depending on the location masticatory mucosa is the keratinized cell layers resist damage from abrasion and are best developed on the gingiva (gum) and hard palate. The lamina propria in these regions rests directly on the periosteum of underlying bone. lining mucosa is Nonkeratinized squamous epithelium predominates in the over the soft palate, cheeks, the floor of the mouth, and the pharynx,the posterior region of the oral cavity leading to the esophagus. Lining mucosa overlies a thick submucosa containing many minor salivary glands, which secrete continuously to keep the mucosal surface wet, and diffuse lymphoid tissue. Throughout the oral cavity, the epithelium contains transient antigenpresenting cells and rich sensory innervation. The lips The central core of the lip contains the orbicularis oris (skeletal) muscle, which is innervated by the facial nerve , and contributes to lip movement and facial expressions. The Lips are divided into the three regions: A. external (skin) region It is covered by keratinized stratified squamous epithelium. The sebaceous glands in the dermis are associated with hair follicles, and sweat glands are present. The skin of the lip is like thin skin and can be divided into epidermis and dermis. B. The vermilion zone of the lip is covered by parakeratinized stratified squamous epithelium. Sebaceous glands (Fordyce granules or spots) may be found in the connective tissue and are not associated with hair follicles. These glands have ducts that release their oily product directly onto the surface of the lip. The vermilion zone appears red because of many blood vessels near the surface of the thin and translucent epithelium . This region can become thick and forms the sucking pad in infants. C. Internal region (labial mucosa) of the lip is an example of lining mucosa, which is covered by nonkeratinized stratified squamous epithelium and contains many elastic fibers; it is very flexible and can be stretched. Its submucosa layer contains many minor salivary glands (mucous glands). The minor salivary glands in the lips are often called labial glands. 1 Dr.Hameda abdulmahdi 2nd stage College of Medicine /Dep. of anatomy & histology The palate It is divided into an anterior hard palate (possessing a bony shelf in its core) and a posterior soft palate (possessing skeletal muscle in its core). The palate separates the nasal cavity from the oral cavity. Therefore, the palate has a nasal aspect and an oral aspect. The entire nasal aspect of the palate (with the exception of the uvula) is lined by pseudostratified ciliated columnar epithelium (respiratory epithelium). 1. The hard palate is lined on its oral aspect by stratified squamous parakeratinized to stratified squamous keratinized epithelium (masticatory mucosa). it contains adipose tissue anteriorly and minor mucous salivary glands posteriorly in the oral aspect of its connective tissue, the lamina propria in these regions rests directly on the periosteum of underlying bone. 2. The soft palate is lined on its oral aspect by stratified squamous nonkeratinized epithelium(lining mucosa). It contains minor mucous salivary glands in the oral aspect of its connective tissue. Tongue The tongue is divided into an anterior two-thirds(papillary area) and a posterior one-third(tonsillar area) by the V-shaped sulcus terminalis, whose apex ends in the foramen cecum(Fig,2). Its dorsal surface is covered by specialized mucosa stratified squamous parakeratinized to keratinized epithelium, whereas its ventral surface is covered by stratified squamous nonkeratinized epithelium. Both epithelial surfaces are underlain by a lamina propria and submucosa of dense irregular collagenous connective tissue. The tongue possesses a core of skeletal muscle, which forms the bulk of the tongue. They are four types of lingual papilla(Fig,3). 1. Filiform papillae are the smallest and most numerous of the four types of papillae. They cover almost the entire superior surface of the anterior two thirds of the tongue and are packed in rows that parallel the sulcus terminalis. Each of the papillae appears cone shaped with some branching processes. Connective tissue forms the central core of each papilla. Filiform papillae have no taste buds and extend from the nonkeratinized stratified squamous epithelium. The surface of the papilla is keratinized and is exposed to a great deal of abrasion . 2 Dr.Hameda abdulmahdi 2nd stage College of Medicine /Dep. of anatomy & histology 2. Fungiform papillae are less numerous than the filiform papillae. They are mushroom shaped and are scattered among the filiform papillae .Fungiform papillae are located at the tip and on the two lateral edges of the tongue. They are more numerous near the tip of the tongue. Taste buds are found on the apical surfaces of fungiform papillae. 3. Circumvallate papillae are large and round with a flat topped cylindrical structure. There are about 10 to 14 papillae arranged in a row along the sulcus terminalis. Each papilla is surrounded by a deep groove (moat), which forms a valley around the papilla. Taste buds are found in the lateral walls of each papilla . 4. Foliate papillae are leaf like folds with flat tops and have deep clefts between the papillae. They are located on the posterior lateral surface of the tongue. They are more prominent in some animals (such as rabbits) than in humans. Foliate papillae contain taste buds in the lateral walls of the papillae. (Figure 2): Surface of the tongue on the region close to its V-shaped boundary, between the anterior and posterior portions. Note the lymphoid nodules (lingual tonsil), glands, and papillae. 3