Tiêu đề Oral Mucosa new 2024 (1).pdf ✅

1 Mucous Membrane Classification of Mucous membrane Keratinized (masticatory) mucosa Non keratinized (lining) Mucosa Specialized mucosa Gingiva + Hard palate Firmly Loosely Dorsal surface of the tongue Soft palate + lip + check + ventral surface of the tongue Floor of the mouth + Vestibule + Alveolar mucosa Keratinized Mucosa Non Keratinized Mucosa Epithelium Thin Thick Basement membrane Severely undulated Slightly undulated Rete pegs Tall + Numerous + Irregular + Slender Usually not found but if found : Short + Few + Broad + Regular Papillary layer Tall If found : very short Reticular layer Always present Always present Submucosa Not found except in hard palate Found Intercellular spaces Large Small Intercellular bridges (desmosomes) Large Small Odland bodies (Keratinosomes) Internally lamellated Rounded + Amorphous core Keratohyaline granules Present Rarely found Mitosis Slow rate High rate Tonofilaments Arranged in bundles Dispersed Keratin layer Found Not found Fillagerin protein Found Not found
2  Mucosa = Epithelium + Lamina propria  Keratinized epithelium consists of 4 layers : 1-Basal (stratum basale) 2- Spinous or prickle (stratum spinosum) 3- Granular (stratum granulosum) 4- Cornified (stratum cornium) a. Basal Cell layer (stratum Basale). -single layer of high cuboidal cells resting on the basement membrane and attaches to it by hemidesmosome . -The basal cells are protein forming cells , so they have large numbers of mitochondria , ribosomes, RER and golgi bodies -They undergo mitosis to provide new cells -These cells are the least differentiated cells of oral epithelium. b-The prickle cell layer (Stratum Spinosum) -several layers of polyhedral cells superficial to the basal cells, These cells are larger than the basal cells. -joined by wide intercellular spaces and have large intercellular bridges which gives the cells a prickly appearance -The prickle cells are the most active in protein synthesis - In the upper cells of the prickle cell layer and in the lower granular cell layers there are membrane bound granules called the Odland Bodies or Keratinosome -It may originate from the Golgi system. Role of Odland bodies:- Elongated and lamellated shape -These structures are responsible for the thickening of the cell membrane which occurs during Keratinization. -May form an intercellular agglutinating material . c-The granular cell layer (stratum granulosum) - Lies above the prickle cell layer and is made up of 2 or 3 layers. - Its cells are larger than the prickle cells . -Cells contain basophilic granules called keratohyaline granules which will form the proteinous matrix in which the tonofilaments are embedded -The granular cells also contain odland bodies or keratinosome . - They are the least active in protein synthesis. A-Keratinized epithelium
3 d-The cornified layer (stratum cornium): It is the superficial layer Histologically they appear amorphous and acidophilic . These cells are characterized by loss of all organelles and keratohyaline granules contains Fillagerin protein + Tonofilaments There are 2 types of keratin :- a) Orthokeratin : keratin devoid of any nucleai b) Parakeratin : keratin contains pyknotic shrunken nucleai and few organelles . ----------------------------------------------------------------------------------------------------------------------------------------------- N.B *The epithelial cells are attached to each others by demosomes and to the basement membrane by hemidemosomes -The desmosomes are type of cell junction between the adjacent epithelial cells and consist of:_ 1. thickening of adjacent cell membrane 2. a pair of attachment plaques 3. extra cellular structure 4. bundles of tonofilaments inserted into the attachement plaque , these tonofilaments either terminate around the attachement plaque but never penetrate the cell membrane. - The hemi-desmosomes is the type of junction between the epithelial cells and the basement membrane and consist of :- 1. thickening of one cell membrane 2. a single attachment plaque, 3. tonofilaments, 4. extracellular structure 1. Stratum Basal (Basal cell layer ) :Similar to that of the Keratinized type. 2. Stratum Intermedium -Formed of large polyhedral cells with short intercellular bridges and small intercellular spaces. -The cells do not have prickly appearance. -There are Odland bodies with rounded shape and amorphous core . - Keratohyaline granules are rarely 3. Superficial cell layer (Stratum Superficial). -It consists of nucleated flat cells which ultimately desquamate as the cornified layer.
4 These cells are called Keratinocytes and have the following criteria : a- Always attached to each other by one or more type of cellular junctions especially demosomes. b- The cytoplasm of these cells is stained with ordinary stain as H & E. c- Their cytoplasm contains characteristic tonofilaments (fibrous protein called keratin )  in addition to the normal keratinocytes, there are non keratinocytes that make up about 10% of cell population (clear cells ) Criteria of Non Keratinocytes :Melanocyte, Langerhans cell, Merkel ‘s cell and Inflammatory cells.** a- They do not attach to each other or to the epithelial cells except Merkel’s cells. b- The cytoplasm of these cells does not stain by H & E and show clear halo around nuclei . c- Their cytoplasm does not contain tonofilaments except Merkel’s cells 1- Pigment cell (Melanocyte) 2- Langerhan’s cell 3- Merkel’s cell Shape Large body with long slender and branched process + contain melanin granules (melanosomes) Similar in shape. Contain granules (Birbeck granules) They do not have long processes. Contain small membrane bounded granules Dendrites Dendritic Dendritic Not denteritic Location Basal and parabasal layers Mainly in attached gingiva High level cell and may be found at lower levels Basally in epithelium Stain by H&E Not stained so called ( Clear dendritic cell ) Not stained so called ( Clear dendritic cell ) Not stained so called ( Clear but not dendritic cell Special stain DOPA reaction Gold chloride PAS positive Origin Neural crest cell Bone marrow Neural crest cells Cell junction No tonofilaments. No desmosomes No tonofilaments. No desmosomes -Little tonofilaments. -Little desmosomes. Associated with the nerve cell Function Pigmentation. If melanosomes engulfed by epithelial cell called (Melanophore) or by C.T. cell (Melanophage) Immunologic function: Processing and presenting antigen to T lymphocyte Responding to touch. Inflamatory cell : transient cell found only in case of inflammation Basement membrane (basal lamina) - The junction between the epithelium and lamina propria is undulated due to interdigitation of connective tissue papillae with the epithelial rete pegs . - It is structureless band in H and E staining and called basement membrane . - Under EM this region is called basal lamina . it consists of : 1- lamina lucida: A Clear zone about 45 nm wide 2- Lamina densa :A layer of finely granular or filamentous material about 50nm thick 3- Lamina fibroreticularis :- Small loops of fibers called anchoring fibers are inserted into the lamina densa . collagen fibrils run through these loops and interlocked with the lamna densa to form a flexible attachement. Some components of lamina fibroreticularis are produced by connective tissue cells .