INTRODUCTION TO ORAL MUCOUS MEMBRANE - DR. DEEPTHI K

It is the moist lining of the oral cavity .Oral cavity consist of 2 components-Covering epithelium
Underlying connective tissue.

1. Oral mucous membrane Prof.Dr . Deepthi K Dept.of Oral & Maxillofacial Pathology Sree Anjaneya Institute of Dental Sciences - Calicut

2. Contents Introduction Classification Functions Comparison of skin with OMM Structural arrangement of OMM Keratinized epithelium Nonkeratinized epithelium Keratosis Nonkeratinocytes Epithelium connective tissue interface Lamina propria Submucosa

3. Mucous membrane

4. Introduction - OMM

5. Boundaries of oral cavity Anteriorly - Continuous with skin of the lip through vermilion border Posteriorly – Continuous with mucosa of pharynx

6. Classifications of oral mucosa

7. Based on function Masticatory mucosa (25%): gingiva and hard palate Lining or reflecting mucosa (60%): lip, cheek, vestibular fornix, alveolar mucosa, floor of the mouth and soft palate Specialized mucosa (15%): dorsum of tongue and taste buds Other 2 areas with slightly different structure – Dentogingival junction & Vermilion border of lip

8. Based on type of keratinization

9. Functions of oral mucosa Defence Act as a barrier for entry of microorganisms Impermeable to bacterial toxins Secretes antibodies Lubrication Through secretion of saliva Prevents mucosa from drying and cracking Helps in speech, mastication, swallowing and perception of taste Sensory OM is sensitive to touch, pressure, pain and temperature Dorsum of tongue – taste sensation Protection Protects deeper tissues from mechanical forces from mastication and food stuff Thermal regulation Seen in dogs

10. Comparison of skin with oral mucosa   Skin Oral mucosa Layers Epidermis & dermis Epithelium & lamina propria Type of keratinization Always orthokeratinized Non keratinized or keratinized (ortho/para) Stratum lucidum Present Absent Hair follicles, sebaceous and sweat glands Present Absent Salivary glands Absent Present

11. Structural arrangement of oral mucosa

12. Epithelium

13. 2 types of cell populations based on function: Progenitor population – is to divide and provide new cells Maturing population – continually differentiate or mature to form a protective surface layer

14. Progenitor cells Situated in the basal layer in thin epithelia (e.g., the floor of the mouth) and in the lower two to three cell layers in thicker epithelia (cheeks and palate). Dividing cells tend to occur in clusters that are more abundant at the bottom of epithelial ridges than at the top. Progenitor cells are of two distinct subpopulations; A small population of progenitor cells cycles slowly and is considered to represent stem cells, the function of which is to produce basal cells and retain the proliferative potential of the tissue. The larger portion of the progenitor compartment is composed of amplifying cells, the function of which is to increase the number of cells available for subsequent maturation.

15. Maturating cells After cell division, each daughter cell recycles in the progenitor population or enters the maturing compartment.

16. The time taken for a cell to divide and pass through the entire epithelium is termed as turnover time of the epithelium

17. Epithelial maturation Maturation in the oral cavity follows two main patterns: Keratinization Orthokeratinization Parakeratinization Nonkeratinization

18. Keratinized epithelium

19. Layers of keratinized epithelium

20. Basal layer/Stratum basale The basal layer or stratum basale is a layer (single layer) of cuboidal or columnar cells adjacent to the basal lamina. Made up of cells that synthesize DNA and undergo mitosis. They become determined once they leave basal layer. Basal cells containing tonofilaments which course toward and attached to attachment plaques.

21. Prickle cell layer Above the basal layer are several rows of larger elliptical or polyhedral cells known as the prickle cell layer or stratum spinosum. This term arises from the appearance of the cells in histologic preparation; they typically shrink away from each other, remaining in contact only at points known as intercellular bridges or desmosomes. This alignment gives the cells a spiny or prickle-like profile. Tonofilaments seen as bundles attached to the attachment plaques. Lamellar granule known as keratinosome/Odland body is seen associated with upper spinous layer.

22. Odland bodies/Keratinosome/membrane coating granules

23. Stratum germinativum

24. Stratum granulosum/granular layer This layer consists of larger flattened and wider cells containing small granules that stain intensely with acid dyes such as hematoxylin (i.e., they are basophilic), and the granules are called keratohyalin granules Nuclei shows signs of degeneration and pyknosis and this layer shows less protein synthesis compared to spinous cells Cell surfaces become more regular and more closely adapted to adjacent cell surfaces Tonfilaments are more dense and seen associated with Keratohyaline granules and Odland bodies

25. Keratinized layer or stratum corneum The surface layer is composed of flat (squamous) cells, termed squames that stain bright pink with the histologic dye eosin (i.e., they appear eosinophilic) and do not contain any nuclei or other cell organelles such as ribosomes and mitochondria. This pattern of keratinization is termed as ORTHOKERATINIZATION

26. The masticatory mucosa, parts of the hard palate and much of the gingiva, can show a variation of keratinization, known as PARAKERATINIZATION In parakeratinized epithelium the surface layer stains for keratin but shrunken (or pyknotic) nuclei are retained in many or allof the squames .

27. The cells of the keratinized layer become dehydrated and flattened and assume the form of hexagonal disks called squames Squames are lost (by the process of desquamation) and are replaced by cells from the underlying layers

28. Functional characteristics of keratinization

29. Areas of keratinized mucosa

30. Nonkeratinized epithelium

31. Layers of nonkeratinized epithelium

32. Basal layer/Stratum basale Single layer of cuboidal or columnar cells adjacent to the basal lamina Made up of cells that synthesize DNA and undergo mitosis. They become determined once they leave basal layer Similar to keratinized epithelial cells

33. Intermediate layer/Stratum intermedium Larger than cells of stratum spinosum Intercellular spaces are not obvious or distended, hence no prickly appearance Contain intermediate keratin filaments which are sparsely distributed within the cells A granular layer is not present, and the cells of the superficial layer contain nuclei that are often plump A slight increase in cell size occurs in the intermediate cell layer, as well as an accumulation of glycogen in cells of the surface layer

34. Superficial layer/Stratum superficiale Contains nucleated (plump) cells, less number of tonofilaments and lacks keratohyaline granules. The surface layer of nonkeratinized epithelium thus consists of cells filled with loosely arranged filaments that are not dehydrated. They thus can form a surface that is flexible and tolerant of compression and distention.

35. Areas of nonkeratinized mucosa

36. keratosis/parakeratosis Keratinization happening in normally nonkeratinized tissue

37. Keratinized Nonkeratinized Features Layer Features Layer Cuboidal or columnar cells containing bundles of tonofibrils and other cell organelles; site of most cell divisions. Basal Cuboidal or columnar cells containing separate tonofilaments and other cell organelles; site of most cell divisions. Basal Larger ovoid cells containing conspicuous tonofibril bundles; membrane-coating granules appear in upper part of this layer. Prickle/spinosum Larger ovoid cells containing dispersed tonofilaments; membrane-coating granules appear in upper part of layer; filaments become numerous. Prickle/spinosum Flattened cells containing conspicuous keratohyaline granules associated with tonofibrils ; membrane-coating granules fuse with cell membrane in upper part; internal membrane thickening also occurs. Granular Slightly flattened cells containing many dispersed tonofilaments and glycogen. Intermediate Extremely flattened and dehydrated cells in which all organelles have been lost; cells filled only with packed fibrillar material; when pyknotic nuclei are retained, parakeratinization occurs. Keratinized Slightly flattened cells with dispersed filaments and glycogen; fewer organelles are present, but nuclei persist. Superficial

38. Nonkeratinocytes in oral epithelium

39. Cell Type Level in Epithelium Ultrastructural Features Function Melanocyte Basal Dendritic; no desmosomes or tonofilaments;premelanosomes and melanosomes present Synthesis of melanin pigment granules (melanosomes) and transfer to surrounding keratinocytes Langerhans Cell Predominantly Suprabasal Dendritic; no desmosomes or tonofilaments; characteristic Langerhans granule Antigen trapping and Processing Merkel cell Basal Nondendritic; sparse desmosomes and tonofilaments; characteristic electron-dense vesicles and associated nerve axon Tactile sensory cell Lymphocyte Variable Large circular nucleus; scant cytoplasm with few organelles; no desmosomes or tonofilaments Associated with the inflammatory response in oral mucosa

40. Epithelium and connective tissue interface Is an undulating interface at which papillae of the connective tissue interdigitate with the epithelial ridges The interface consists of connective tissue ridges, conical papillae, or both, projecting into the epithelium. This arrangement makes the surface area of the interface larger and may provide better attachment, enabling forces applied at the surface of the epithelium to be dispersed over a greater area of connective tissue.

41. Epithelium Basement membrane Components in the structure of OMM – Light microscopic Lamina propria/connective tissue Submucosa

42. Basement membrane Interface between epithelium and connective tissue seen under Light microscope Appears thick and includes reticular fibers 1 to 4µm wide and cell free Stains with periodic acid – Schiff method as it contains neutral mucopolysaccharides (glycosaminoglycans)

43. Basal lamina Ultrastructurally (under electron microscope) basement membrane is called basal lamina Under higher magnification it is a complex structure consisting of lamina and fibers

44. Epithelium Lamina lucida Lamina densa Lamina propria/connective tissue Submucosa Structure of basal lamina (under electron microscope)

45. Keratinized areas

46. Structure of basal lamina – 2 layers

47. Functions of basement membrane/basal lamina Promotes epithelial cell growth and differentiation Promote peripheral nerve regeneration and growth Prevent metastasis

48. Lamina propria

49. Contents of lamina propria Cells The lamina propria contains several different cells: fibroblasts, macrophages, mast cells, and inflammatory cells. Fibers and ground substance The intercellular matrix of the lamina propria consists of two major types of fibers , collagen and elastin, ground substance composed of glycosaminoglycans, and serum-derived proteins Blood vessels and nerves

50. Submucosa Consist of connective tissue of varying thickness and density. It attaches the mucous membrane to the underlying structures. Glands, blood vessels, nerves and adipose tissues are present in this layer.

51. Structural variations Thickness of epithelium Degree of keratinization Complexity of epi-CT interface Composition of lamina propria Presence or absence of submucosa

52. Masticatory mucosa Gingiva Hard palate Lining or reflecting mucosa Inside of lip Cheek Alveolar mucosa Floor of the mouth Soft palate Specialized mucosa Dorsum of tongue Taste buds

53. Lining mucosa Masticatory mucosa

54. Lining mucosa Masticatory mucosa Epithelium Thicker Moderately thick Interface Smooth with slender CT papillae Convoluted with numerous elongated CT papillae Lamina propria Thin with few CT fibers Thick with dense net work of fibers Submucosa Loose & elastic Absent

55. HARD PALATE

56. Incisive papilla Contains oral parts of vestigial nasopalatine ducts

57. Palatine Rugae Ridges of OMM Composed of CT core Are permanent and unique for individuals & thus can be used as identification for forensic purposes

58. Histology Epithelium : Keratinised , immobile & Str cornium shows Stacking- ordered pile Lamina Propria : Thick & long papillae Submucosa : Absent in midpalatine raphe & gingival region Mucoperiosteum in regions where submucosa is absent

59. Zones of hard palate Gingival region: adjacent to teeth Palatine raphe Anterolateral area: fatty zone Posteriolateral area: glandular zone

60. GINGIVA

61. Color: Coral pink ( blonds) Related to complexion & Race Vascular supply Thickness of epithelium Degree of keratinization Presence of pigment containing cells

62. Texture Free gingival surface is smooth Attached gingival surface is pitted giving orange- peel appearance called stippling (elevations & shallow depressions in between the epithelium) Depressions correspond to centre of heavier epithelial ridges F unctional adaptation to mechanical injuries *** Loss of stippling is seen in oedema due to gingival inflammation

63. Parts of gingiva Free gingiva Attached gingiva Interdental papilla

64. Free gingival groove Dividing line between free gingiva and attached gingiva Runs parallel to the margin of gingiva 0.5-1mm below Mucogingival junction Junction between attached gingiva &alveolar mucosa I s 3-5mm below the crest of alveolar bone

65. Interdental grooves Depression seen on gingival surface between two teeth corresponding to depression on alveolar process between eminences of sockets

66. Gingival Sulcus

67. Types of gingival epithelium GIngiva - Keratinized Sulcular epithelium Junctional epithelium Nonkeratinized No rete ridges

68. Gingival sulcus/gingival crevice Space between inner aspect of gingiva and tooth Lined by sulcular epithelium Depth of gingival sulcus 0.5 - 3 mm, average of 1.8 mm When the sulcus is deepened (>3mm) due to inflammation: periodontal pocket

69. Crevicular fluid Present in the sulcus Contains: a mixture of desquamated epithelial cells & inflammatory cells Function: mechanical cleaning

70. Interdental papilla Part of gingiva fills the space between two adjacent teeth Anterior tooth Posterior tooth Triangular – when viewed from front Pyramidal in three dimensional Tent shaped with two peaks ( oral and vestibular part) & a valley like depression in centre Interdental papilla

71. Gingival col

72. Epithelium : keratinised & non keratinised areas Rete pegs: long, slender and numerous LP : dense, avascular, containing gingival fibers , inflammatory cells subjacent to the sulcus Submucosa : absent Mucoperiosteum present

73. Epithelium Rete ridges Lamina propria

74. Gingival fibers Gingival fibers of the PDL enter into lamina propria and attach gingiva firmly to tooth. Collagen fibers in the lamina propria of gingiva are arranged in various groups Dentoginigval – from cervical cementum to lamina propria of gingiva, are most numerous Alveologingival – arises from alveolar crest to lamina propria of gingiva Circular – circle the tooth and interlace with other fibers Dentoperiosteal – cementum to periosteum of alveolar crest Transseptal fibers – accessory fibers , travel interproximally between adjacent tooth

75. Alveolar Mucosa

76. LIP Skin on outer surface vermillion zone labial mucosa on its inner surface Striated muscles in their core

77. Vermillion Zone

78. Vermillion Zone (Red Zone)

79. Vermillion border Line separating vermillion zone from skin of lip Cupid’s bow Commissure Cupid’s bow

80. Intermediate Zone Between vermillion zone & labial mucosa In infants: suckling pad

81. Soft Palate

82. Buccal Mucosa

83. Linea Alba

84. Fordyce granules

85. Floor of Mouth Thin epithelium & highly vascular LP

86. Tongue The anterior 2/3- body or papillary portion T he posterior 1/3 – base or lymphatic portion

87. Filiform papilla (thread shaped)

88. Numerous Covering dorsum of anterior third of tongue Cone shaped giving velvet like appearance Keratinized No taste buds

89. Fungiform

90. Fungiform papillae Mushroom shaped Round and reddish Covered by thin epithelium- Keratinised or nonkeratinised Rich capillary net work in LP Contain 1-3 taste buds on their dorsal surface

91. Circumvallate

92. Foliate papillae ( leaf like) parallel ridges alternate with deep grooves 1-3 taste buds are present in the lateral walls of the ridges

93. Unique sense organs that contain the chemical sense for taste

94. Dento - gingival junction Junction between gingiva & tooth Extents from CEJ to Bottom of gingival sulcus 0.3 to 2mm Junctional attaches the gingiva to tooth

95. Junctional epithelium or primary attachment epithelium Surrounds the tooth like a color Resembles REE Non keratinised No rete ridges Consists of Str Germinativum & Str Spinosum

96. Tapers in the apical direction (thick coronally & thin apically) High turn over rate (5-6days ) (regenerates readily) Highly permeable & permits easy flow of crevicular fluid) (route for passage of bacterial products from sulcus to connective tissue) Point of least resistance

97. Has two basal lamina 1. Internal basal lamina in contact with the tooth ( hemi desmosomal attachment) 2. External basal lamina in contact with the lamina propria of gingiva

98. Development of Primary attachment epithelium

99. Active & passive eruption Active eruption : Actual movement of tooth towards the occlusal plane Passive eruption : Separation of primary attachment epithelium from the enamel

100. Primary

101. Stages in passive eruption

102. AE on enamel Apical end of AE on CEJ Bottom of gingival sulcus on enamel surface Clinical crown shorter than anatomic crown In primary & In permanent up to 30yrs AE partly on enamel & cementum Apical end of AE end on cementum Bottom of gingival sulcus on enamel Up to 40 yrs

103. AE completely on cementum Bottom of gingival sulcus at CEJ AE & bottom of gingival sulcus on cementum