Oral Mucosa: Lecture Notes (2021) - University of Ghana

ORAL MUCOSA Development, Gross Anatomy, Function and Histology of the Oral Mucosa Nanci, 2018 Wiki-minor, 2019 Dr. Paul M. Matondo DMD, MGCS (Orthodontics), MPhil (H. Anatomy) Department of Oral Biology University of Ghana De...

ORAL MUCOSA Development, Gross Anatomy, Function and Histology of the Oral Mucosa Nanci, 2018 Wiki-minor, 2019 Dr. Paul M. Matondo DMD, MGCS (Orthodontics), MPhil (H. Anatomy) Department of Oral Biology University of Ghana Dental School College of Health Sciences University of Ghana, Korle-bu  General Presentation FIGURE 1. Anatomic locations occupied by the three main types of mucosa in the oral cavity. (From Nanci A, : Ten Cate's Oral Histology, ed 9, St Louis, 2018, Elsevier) 2  Definition Mucous membrane - used to describe the moist lining of the gastrointestinal tract (GIT), nasal passages, and other cavities that communicate with the exterior. In the oral cavity this lining is called the oral mucous membrane or oral mucosa. 3  Oral mucosa Very resilient tissue. Subject to a host of intrinsic and external environmental stimuli, irritants, and stressors, both physiologic and potentially pathological in nature. 4  Oral mucosa Among the mechanisms that ensure preservation and optimal function of the oral mucous membrane as a whole are; (1) the microstructure of the oral surface epithelium; (2) the intricate apparatus that attaches the naturally avascular epithelium to the underlying stromal tissues that provide it with critical vascular, neural, nutritional, and immunological support; 5  Oral mucosa (3) the mechanical strength provided by a supportive extracellular matrix; and (4) secretions from both the major salivary glands and, in particular, a multitude of submucosal minor salivary glands that serve to lubricate the oral surface, contribute to the digestive process, facilitate speech and taste sensation, and take part in various other functions essential to homeostasis. 6  Oral mucosa A - Alveolar mucosa, presence of loose C submucosa which A allows for wide D E degrees of movement. C - The mucogingival F line demarcates the boundary between the attached gingiva D and the alveolar mucosa. E - Free gingiva. F - Interdental papilla. FIGURE 2. Anterior view of dental arches in occlusion: Gingival tissues and alveolar mucosa. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Own work) 7  Oral mucosa On the palatal surface of the maxillary teeth, there is no alveolar mucosa. Here the attached gingiva merges with the palatal mucosa. FIGURE 3. Occlusal view of a maxillary arch: Teeth, gingival tissues and palatal mucosa. (From Dr. P. M. Matondo, University of Ghana Dental School, Accra, Own work) 8  A - Palatoglossal fold. B – Palatopharyngeal A fold. B A+B = Tonsillar pillars. *= Lymphoid tissue. FIGURE 4. Anterior view of the oropharynx: Posterior wall, folds. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 9  The dorsal surface of the tongue is covered by specialized mucosa. The roughness of the surface is attributable to the abundant, small hair-like filiform papillae that cover much of the anterior two- thirds of the tongue, and lack taste buds. FIGURE 5. Dorsal surface of the tongue. (From Mesher A L: Junqueira’s Basic Histology, Ed 13, accessmedicine.com ) 10  Non keratinized lateral ventral surface of tongue. FIGURE 6. Ventral surface of the tongue. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 11  Location The oral mucosa is continuous with the skin at the lips anteriorly and with the GIT (gut) posteriorly at the pharynx. Thus the mucous membrane shows some properties of each. The skin, oral mucosa and intestinal lining; all consist of a covering epithelium and an underlying connective tissue. 12  Oral cavity Oral vestibule Oral cavity proper From the alveolar rigges to the Bounded by labial and buccal palatoglossal folds mucosa externally and maxillary Superiorly by the hard and soft and mandibular alveolar ridges palates internally The floor of the mouth inferiorly the alveolar processes laterally 13  Functions 1. Protection - the oral mucosa shows a number of adaptations of the epithelium and the connective tissue to withstand external insults. 2. Sensation - receptors respond to temperature, touch and pain. Taste receptors found only on tongue. Reflexes such as swallowing , gagging retching and salivating are also initiated by receptors in the oral mucosa. 14  Functions 3. Secretion - saliva, many minor salivary glands present in oral mucosa. Presence of sebaceous glands whose secretions are insignificant. 4. Thermal regulation ( important in some animals) 15 FIGURE 7. Sebaceous glands in the mucosa of the cheek. Clinical appearance: clusters of yellowish spots called Fordyce's granules. (From Nanci A, : Ten Cate's Oral Histology, ed 9, St Louis, 2018, Elsevier) 16  Development Develops by fusion of the embryonic stomatodeum with the foregut after rupture of the buccopharyngeal membrane after 26 days of gestation. Comes to be lined by epithelium derived from ectoderm and endoderm 17  Development Fusion of stomatodeum with foregut after rupture of the buccopharyngeal membrane FIGURE 8. Sagittal section through a 4-week-old embryo showing the stomatodeum. (From Nanci A, : Ten Cate's Oral Histology, ed 9, St Louis, 2018, Elsevier) 18  Development The structures that develop in the branchial arches, for example: tongue, epiglottis, and pharynx are covered by epithelium derived from endoderm, whereas the epithelium covering the palate, cheeks, and gingivae is of ectodermal origin. 19  Landmarks 5-6 weeks: single layer of cells lining the primitive oral cavity forms two cell layers. 10-14 weeks: seperation of cells covering the cheek area and the alveolar mucosa and thus forming the oral vestibule 20  Landmarks 8-11 weeks: elevation and closing of the palatal shelves. Future morphology of adult oral cavity apparent. 21  Organization Three (3) main types of oral mucosa are recognized: a. Masticatory-25% b. Lining mucosa-60% c. Specialized-15% 22  Features of oral mucosa (compared to skin) More deeply coloured Moistness of surface Absence of appendages Sebaceous glands are present in the upper lip and buccal mucosa in about ¾ of adults (Fordyce spots or granules) Smooth surface Presence of papillae on dorsum of tongue 23 24  Variations in oral mucosa Lining mucosa of lips and cheeks soft and pliable Gingiva and palate covered by firm immobile layer 25  Clinical implications Fluid like LA can be introduced without pain into the lining mucosa Lining mucosa gapes when surgically incised and may require suturing, but masticatory mucosa does not 26  The General Structure of the Oral Mucosa The entire oral mucosal surface is lined by stratified (layered) squamous (scale-like) epithelium, an avascular, highly organized, and semipermeable ectodermal tissue. This tissue varies in thickness and surface keratinization according to its location in the mouth and the functional demands of that location. 27  The General Structure of the Oral Mucosa An underlying connective tissue layer called the lamina propria( epithelium and dermis in skin), 28  The General Structure of the Oral Mucosa Oral stratified squamous epithelium replenishes itself relatively frequently. The roughly 14 to 21 days of epithelial turnover time is necessarily rapid because of the considerable challenges oral mucosa is subjected to, functional and otherwise, throughout the waking hours and during sleep. 29  Representation of Stratified Squamous Epithelium FIGURE 9. Schematic illustration of Oral mucosa: Epithelium and Lamina propria. 30 (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) The basal-most portion of stratified squamous epithelium is arranged in undulating projections termed rete pegs. The rete pegs are part of the mechanism of attachment of the squamous epithelium to the basement membrane, which separates it from several layers of underlying stromal connective tissue 31  Histology In many regions of the oral cavity, there may be presence of a third layer, the submucosa, found between the lamina propria and the underlying bone or muscle. In regions such as the gingiva and parts of the hard palate, oral mucosa is attached directly to the periosteum of underlying bone with no intervening submucosa (mucoperiosteum). 32  Histology The minor salivary glands are situated in the submucosa. Sebaceous glands, if present, lie in the lamina propria. 33  Basic morphology of oral mucosa In all regions of the mouth two distinct regions are recognized A- Stratified squamous epithelium that is keratinized in some areas. B- Lamina propria, which is a connective tissue is found beneath the epithelium. C-The submucosa is only present in some areas and consists of looser connective tissue containing fat deposits and glands. Larger nerves and blood vessels run in the submucosa. Bone FIGURE 10. Histological section of the oral Mucosa: Main tissue components. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 34  Epithelium of Oral Mucosa Three (3) types of stratified squamous epithelium are found: nonkeratinized, orthokeratinized and parakeratinized. Nonkeratinized epithelium is associated with lining mucosa. Orthokeratinized and parakeratinized are associated with masticatory mucosa 35  The epithelium of the oral mucosa A- Stratum germinativum (or D stratum basale). Contains C progenitor cells (stem cells). Mitosis only occurs in this area. Daughter cells pass B the surface and during toward AAA of maturation the process take on the appearance A characteristic of the various layers. Single layer FIGURE 11. Histological section of the oral epithelium: A - Stratum germinativum (stratum basale). (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 36  The epithelium of the oral mucosa D spinosum (prickle B - Stratum C Consists of round or layer). oval cells several layers thick. Cells show first stages of B B maturation. Contain granules (odland A bodies) which are rich in phospholipids FIGURE 11. Histological section of the oral epithelium: B - Stratum spinosum (prickle layer). (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 37  The epithelium of the oral mucosa C- Stratum granulosum D layer). Cells here (granular C C show a further increase in maturation compared with the two lower layers. Cells B large numbers of contain smallAgranules called keratohyaline granules. FIGURE 11. Histological section of the oral epithelium: C - Stratum granulosum (granular layer). (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 38  The epithelium of the oral mucosa D D - Stratum corneum. D Void of all organelles. Cells are filled entirely with closely packed tonofilaments. Provides the mechanical protective function to the mucosa. Contains keratinized and non keratinized epithelial cells FIGURE 11. Histological section of the oral epithelium: D - Stratum corneum. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 39  The epithelium of the oral mucosa D C B A FIGURE 11. Histological section of the oral epithelium: A – B – C – D (Recall) (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 40  The epithelium of the oral mucosa The non keratinocytes make up 10% D of the cells in the oral epithelium and include melanocytes, langerhans cells and merkel cells. All lack the tonofilaments and desmosomes, characteristic of keratinocytes (except for merkel cells). 41  Maturation in the oral mucosa Maturation in the oral cavity follows two (2) main patterns: keratinization and non keratinization Keratinized zone: the epithelial surface of the hard palate , gingiva and dorsum of tongue. Non keratinized zone: epithelial surface of the lips, buccal mucosa, soft palate, underside of tongue and floor of mouth. 42 Features of maturation of keratinized and non keratinized epithelium keratinized non keratinized Features Cell layer Features Columnar and cuboidal Basal same, contain seperate Contain bundles of tonofibrils tonofibrils Larger ovoid cells. Bundles of prickle same, tonof`s dispersed tonofibrils layer flattened cells ,keratohyaline Granular slightly flattened cells granules glycogen Extremely flattened and dehy- keratinized slightly flattened cells Drated cells. No organelles fewer organelles 43  Hyperkeratosis Hyperkeratosis of oral epithelium that normally is keratinized represents a physiologic response of the epithelium to chronic irritation, similar to that occuring in callous formation on the palms and soles. Hyperkeratosis of nonkeratinized oral epithelium may be physiologic but can also be associated with abnormal cellular changes that eventually lead to cancer of the squamous epithelium. 44  Cells of the epithelium Make up about 10% of the cell population, collectively known as non-keratinocytes. All, except merkel cells, have no desmosomes. 45 Cell type Level in epithelium Function Melanocyte basal synthesis of melanin pigment granules and transfer to surrounding keratinocytes Langerhans cells predominantly suprabasal antigen trapping and processing Merkel cell basal tactile sensory cell Lymphocyte variable associated with the inflammatory response in the oral mucosa 46  Pigmentation of oral mucosa The colour of the oral mucosa is the net result of a number of factors one of which is pigmentation. Two (2) types of pigmentation: exogenous and endogenous. Exogenous is caused by foreign material introduced into the body locally or systematically. Endogenous pigmentation arises from normal physiologic processes. 47  Pigmentation of oral mucosa Endogenous pigments most commonly contributing to the colour of the oral mucosa are melanin and haemoglobin. Melanocytes arise from the neural crest ectoderm and enter the epithelium at about 11 weeks of gestation. Lightly and dark skinned individuals have the same number of melanocytes. 48  Junction of the epithelium and lamina propria Undulating interface; papillae of connective tissue intedigitate with the epithelial ridges. Interface consists of connective tissue ridges, conical papillae or both projecting into the epithelium. 49  Junction of the epithelium and lamina propria The interface enables forces applied at the surface of the epithelium to be dispersed over a greater area of connective tissue. Masticatory mucosa has more papillae than lining mucosa. 50  Junction of the epithelium and lamina propria Junction presents a major interface for metabolic exchanges between the epithelium and connective tissue, for the epithelium has no blood vessels. Presence of basal lamina. 51  Junction of the epithelium and lamina propria Connective tissue ridges, conical papillae or both projecting into the epithelium. FIGURE 12. Junction of the epithelium and lamina propria. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 52  Junction of the epithelium and lamina propria FIGURE 13. Basal lamina: ultrastructure as seen under electron microscope (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011 ) 53  Junction of the epithelium and lamina propria FIGURE 14. Schematic presentation of junction between epithelium and connective tissue. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 54  Junction of the epithelium and lamina propria Several genetic defects and autoimmune diseases cause defects in the basal lamina, for example: pemphigoid – seperation of epithelium from the connective tissue occurs at the level of the lamina lucida. 55  Lamina propria It is the connective tissue supporting the oral epithelium. It consists of two layers: 1. A superficial, papillary layer in which the collagen fibres are thin and loosely arranged. 2. Deep, reticular layer dominated by thick parallel bundles of collagen fibres. 56  Lamina Propria The lamina propria is divided into a superficial (papillary) segment and a deeper (reticular) segment. Inferior to the lamina propria lies the submucosa. P - papillary layer R - reticular layer sm - submucosa msg - minor salivary glands FIGURE 15. Lamina Propria: histological section, two layers. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 57 Cell type morphologic function distribution characteristic Fibroblast stellate or secretion of fibers throughout elongated and ground substance Histiocyte spindle shaped resident precursor throughout or stellate of functional macrophage Macrophage round phagocytosis including areas of chronic antigen processing inflammation Mast cell round or oval secretion of inflammatory throughout , mediators and vasoactive often subepith agents Polymorphonuclear Leukocyte(neutrophil) round phgocytosis and cell killing areas of acute inflammation 58 Cell type morphology function distribution Lymphocyte round humoral or cell mediated areas of acute response and chronic inflam Plasma cell cartwheel nucleus synthesis of immunoglobulins areas of chro nic inflamm Endothelial cell lining of blood and lining vascular lymphatic channels channelsn through out lamina propria 59  Fibers and ground substance of the lamina propria Consists of two major types of fibers, collagen and elastin. Collagen is primarily of type I and type III, with types IV and VII occuring in the basal lamina. Type V may be present in inflamed tissue. 60 Blood supply Revise 61  Nerve supply Densely innervated so that it can monitor all substances entering. A rich innervation serves to initiate and maintain a variety of voluntary and reflexive activities involved in mastication, salivation, swallowing , gagging and speaking. 62  Innervation Efferent supply Afferent supply Autonomic, supplies Fibers of the facial (VII), the blood vessels and glossopharyngeal (IX) minor salivary glands. and vagus (X) nerves. Arise mainly from the 2nd and 3rd divisions of the trigeminal nerve. 63  Innervation Free nerve endings are found in the lamina propria and within the epithelium, where they are frequently associated with merkels cells. Sensory nerve networks are more developed in the oral mucosa lining anterior than in the posterior regions of the mouth. 64  Innervation Temperature reception is more acute ► in the vermillion border of the lip, ► at the tip of the tongue and, ►on the anterior hard palate… than ► in more posterior regions of the oral cavity. 65  Taste bud Specialized receptor that occurs only in the oral cavity and pharynx. Found mainly in the fungiform, foliate, and circumvallate papillae of the tongue. Histologically, barrel-shaped structure composed of 30-80 spindle-shaped cells. 66  Taste bud The cells of the taste bud are divided into three types: light (type I), dark (type II), and intermediate (type III). Type I cells are the most common representing about half all cells of the taste bud. 67  Variations in the oral mucosa Masticatory. Lining. Specialized. 68  Lining mucosa Located at: the soft palate, ventral surface of tongue, floor of mouth, alveolar mucosa, labial and buccal mucosa, vermillion zone of lips and intermediate zone of lips. 69  The mucosa of the soft palate A - Non keratinized lining mucosa B - Broad submucosa containing many small mucous glands C - Palatal muscles D - The nasal surface of the soft palate FIGURE 16. Soft palate mucosa: main components. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 70  The buccal mucosa A - Fibers of the buccinator muscle. B – Epithelium. C - Lamina propria. D - Submucosa with minor salivary glands. FIGURE 17. Buccal mucosa : main components. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 71  The alveolar mucosa A - Thin non keratinized epithelium. B - Lamina propria. C - Underlying blood vessels near the surface submucosa made up of thick elastic fibers attaching it to periosteum of alveolar process. FIGURE 18. Alveolar mucosa: main components. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 72  Masticatory mucosa Found in the gingiva, hard palate. Absence of submucosa. Lamina propria bound directly to bone A. FIGURE 19. Masticatory mucosa: main components. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 73  The hard palate A - Oral cavity. B - Palatal process of maxilla. No submucosa in most of the central area. However in the attached gingiva, where the palate joins the alveolus, a submucosa C is present and contains the main neuromuscular bundle D. The nasal surface of the hard palate is lined by a respiratory mucosa. FIGURE 20. Hard palate mucosa: main components. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 74  Specialized mucosa Dorsal surface of tongue, although it is covered by what is functionally a masticatory mucosa, it is also a highly extensible lining and in addition has different types of lingual papillae. The mucous membrane of the tongue is composed of two parts, with different embryonic origins and is divided by the sulcus terminalis. 75  Specialized mucosa Anterior 2/3 derived from 1st pharyngeal arch known as the body. The posterior 1/3 is derived from the 3rd pharyngeal arch and is known as the base. 76  Specialized mucosa FIGURE 21. Dorsum of the tongue: body and base (root). (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 77  The tongue and floor of the mouth A - Ventral surface of the tongue. B - Floor of the mouth. The submucosa is extensive on the floor of the mouth but indistinct on the ventral surface of the tongue where the mucosa binds down to the tongue muscles C. FIGURE 22. Ventral Surface of tongue and floor of mouth. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 78  The tongue and floor of the mouth The mucosa typically of lining type on the ventral surface and the floor of the mouth. The lingual surface on the dorsum of the tongue is a masticatory mucosa that is specialized to fulfill sensory as well as mechanical functions. 79 The tongue and floor of the mouth The anterior two-thirds of the tongue is covered with numerous papillae which can be classified into four types: Filiform, fungiform, foliate and circumvallate papillae. The posterior one –third of the tongue is studded with small lymphatic nodules (or follicles). 80  Mucocutaneous junction Where the skin is continuous with the oral mucosa. A transitional region where appendages are absent except for a few sebaceous glands. The epithelium of this region is keratinized but thin with long connective tissue papillae containing capillary loops. This arrangement brings the blood close to the surface and accounts for the strong red colouration in this region called the vermillion zone of the lip. 81  Vermillion zone Lacks salivary glands and contains few sebaceous glands, thus tends to dry out often becoming cracked and sore (harmattan ). 82  Vermillion zone FIGURE 23. Sagital section of the lower lip: Vermillion zone. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 83  The lip and cheek Vermilion zone The lip and cheek are part of Outer Inner the muscles of surface surface Minor facial expression. Striated salivary muscles glands Oral skin mucosa FIGURE 24. Sagital section of the lower lip: Vermillion zone. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 84  The gingival sulcus In clinically healthy mouths the sulcus is 0.5-2.0mm deep. Sulci greater than 3mm are generally accepted as diseased and are described as periodontal pockets A - Epithelium of attached gingiva. B - Epithelium of free gingiva. C - Epithelium of gingival sulcus. D - Junctional epithelium. FIGURE 25. Gingival sulcus: attached and free gingiga. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 85  The junctional epithelium Enamel Also known as attached epitheium. It is an epithelial collar which surrounds the tooth and extends from the region of the cemento- enamel junction to the bottom of the gingival sulcus. A - Epithelium of attached gingiva. B - Epithelium of free gingiva. C - Epithelium of gingival sulcus. D - Junctional epithelium. FIGURE 26. Junctional epithelium. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 86  The junctional epithelium Enamel Consists of two cells layers: stratum germinativum and stratum spinosum. A - Epithelium of attached gingiva. B - Epithelium of free gingiva. C - Epithelium of gingival sulcus. D - Junctional epithelium. FIGURE 26. Junctional epithelium. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 87  Junctional epithelium Derived from the reduced enamel epithelium of the tooth germ. One of the remarkable properties of the junctional epithelium is that it readily regenerates from the adjacent oral sulcular or oral epithelium if it is damaged or surgically excised. 88  Attachment of junctional epithelium to the tooth The cells of the junctional epithelium immediately adjacent to the tooth attach themselves to the tooth by hemidesmosomes within the cells and basal lamina produced by the cell. FIGURE 27. Attachment of junctional epithelium to the tooth. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 89  Attachment of junctional epithelium to the tooth The combination of the hemidesmosomes and basal lamina is known as the attachment apparatus or epithelial attachment. FIGURE 27. Attachment of junctional epithelium to the tooth. (From Dr. K. G. Amoah, University of Ghana Dental School, Accra, Oral Mucosa, Oral Biology Lecture Notes, 2011) 90 THANK YOU !!!