英语论文网

es. The floor of the fauces is represented by the dorsum of the posterior portion of the tongue. The tonsils are composed of lymphoid tissue; they are soft and have a red or deep pink papillary surface.
Oropharynx
     Beyond the posterior pillars of the fauces is the oropharynx, that part of the pharynx lying between the nasopharynx and laryngeal pharynx. It extends from the soft palate to the level of the hyoid bone. The oropharyngeal mucosa covers the muscles of the pharynx and often contains accumulations of lymphoid tissue so that the color of the pharyngeal mucosa is pink. with occasional raised reddish areas.
HISTOLOGY OF OBAL MUCOSA
     Oral mucous membrane is essentially similar to skin but lacks the secondary structures or skin appendages. The oral mucosa is composed of a surface stratified squamous epithelium and an underlying connective tissue corium or lamina propria. There is some variation in the structure of oral mucosa in different areas of the mouth, depending upon environment and physiologic processes, but a basic structure of mucosa can be outlined and the variation mentioned.
     The epithelium of oral mucosa is usually thicker than that of skin and has deeper extensions of rete pegs into the underlying connective tissue. The stratified squamous epithelium has three layers. The stratum germinativum or basal layer is immediately adjacent to the connective tissue and represents the germinal layer of the epithelium. The basal cells are cuboidal or columnar with large deeply staining nuclei; they are arranged in a uniform row, one or two cells thick. They are separated from underlying connective tissue by a so-called basement membrane.
     Above the basal layer is the stratum spinosum or prickle-cell layer. This is a relatively wide zone of polyhedral cells with large nuclei. The nuclei stain less intensely than those of the basal layer, and for this reason the basal layer is usually well demarcated from the overlying prickle-cell layer. The individual cells of the stratum spinosum are clearly outlined by cell walls, and the cells are slightly separated and appear to be joined by fine protoplasmic processes, referred to as intercellular bridges. These processes or intercellular fibrils are responsible for the prickle-cell connotation. The cells of the stratum spinosum tend to flatten as they approach the surface layers.
     The stratum granulosum or granular layer lies above the stratum spinosum and is composed of several layers of flattened cells that contain large numbers of deeply staining granules in the cytoplasm. These have been referred to as keratohyalin granules. In skin, a stratum lucidum or thin clear zone often occurs above the stratum granulosum. Howeve this zone is normally absent in oral mucosa.
     The surface zone is the keratinized or cornified layer referred to as the stratum corneum. The stratum corneum is composed of varying amounts of keratin, usually structureless fine layers of eosinophilic material with occasional cell nuclei present or clear spaces representing degenerated nuclei. The depth of the stratum corneum varies considerably in oral mucosa, depending upon the nature of the tissue. Areas of the mouth. that receive little stimulation or traumatic influences either are nonkeratinized or have a very thin stratum corneum. The floor of the mou本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。