Subject: Oral Biology Chapter: Oral Mucous Membrane Topic: Subdivisions of ; Keratinized Areas Teacher: Dr. Munawar Aziz Khattak Date: 07-05-2020 LECTURE VI

2 Learning Objective

• At the end of this lecture, the students will be able to know about the;  Oral Mucous Membrane  Subdivisions of Oral Mucosa  Keratinized Areas

3 SUBDIVISIONS OF ORAL MUCOSA

• Keratinized areas  Masticatory mucosa  Vermilion zone of • Nonkeratinized areas  Lining mucosa • Specialized mucosa Keratinized Areas

Masticatory Mucosa • Keratinized • Gingiva and the hard Similarities • Thickness and keratinization of epithelium • Thickness, density, and firmness of lamina propria • Being immovably attached Differences • In their submucosa

• The mucous membrane is immovable • It is pink Hard Palate Cont’d…

Epithelium • Uniform in form • Well-keratinized surface  Cells of the stratum corneum exhibit stacking  The pedicles  The increase in number and length of desmosomes  The density of the tonofilaments  The complementary grooves and ridges (highly folded interface) Hard Palate Cont’d… Hard Palate Cont’d… Lamina propria • A layer of dense connective tissue • Thicker in the anterior than in the posterior parts • Numerous long papillae Submucosa • Various regions in the hard palate differ Zones of the Hard Palate 1. Gingival region 2. Palatine raphe 3. Anterolateral area or fatty zone 4. Posterolateral area or glandular zone Hard Palate Cont’d… Hard Palate Cont’d…

1. Gingival Region (Zone) 2. Palatine Raphe

• The Palatine gingiva • The Median area • Adjacent to the teeth • Extending from the • Epithelium incisive or palatine papilla posteriorly • Lamina propria • Epithelium • No submucosa • Lamina propria • Periosteum • No submucosa • Periosteum Hard Palate Cont’d…

3. Fatty Zone 4. Glandular Zone

• Anterolateral • Posterolateral • Between the palatine • Between the palatine gingiva and palatine gingiva and palatine raphe raphe • Filled with adipose tissue • Filled with glands • Act as a cushion • Act as a cushion • Epithelium • Epithelium • Lamina propria • Lamina Propria Hard Palate Cont’d… Hard Palate Cont’d…

3. Fatty Zone 4. Glandular Zone

• Submucosa - Bands of • Submucosa - Bands of dense fibrous connective dense fibrous connective tissue, arranged at right tissue, arranged at right angles to the surface angles to the surface • Periosteum • Periosteum • Distance between lamina • Distance between lamina propria and periosteum is propria and periosteum is smaller larger • Wedge shaped area • Wedge shaped area (anterior palatine vessels (anterior palatine vessels and nerves run) - smaller and nerves run) - larger Hard Palate Cont’d…

• Palatine papilla • Formed of dense connective tissue • Contains the oral parts of the vestigial nasopalatine ducts • Blind ducts of varying length • Lined by simple or pseudostratified columnar epithelium • Rich in goblet cells • Small mucous glands open into the lumen of the ducts • Sometimes become cystic in humans • Surrounded by small, irregular islands of hyaline cartilage Palatine Rugae • Transverse palatine ridges • Irregular and often asymmetric in humans, • Ridges of mucous membrane • Extending laterally from the incisive papilla and the anterior part of the raphe • Core is made of a dense connective tissue layer with fine interwoven fibers Epithelial Pearls • In the midline, especially in the region of the incisive papilla • Found in the lamina propria • Consist of concentrically arranged epithelial cells that are frequently keratinized • Remnants of the epithelium formed in the line of fusion between the palatine processes GINGIVA Gingiva Cont’d…

• Extends from the dentogingival junction to the alveolar mucosa • Subject to the friction and pressure of mastication Boundaries: • On outer surface of Upper / Lower Jaw • On Inner surface of Lingual / Palatal Jaw Color: • Normally pink (sometimes a grayish tint)  Partly on the surface (keratinized or not) and thickness  Partly on pigmentation (melanin, brown-black) ANATOMIC DIVISIONS OF GINGIVA Gingiva Cont’d… Gingiva Cont’d… Free Gingiva • Free gingival groove (0.5 to 1.5 mm) Attached gingiva • Width 4–6 mm, shows • is 3–5 mm below the alveolar crest • From oral or vestibular aspect - triangular • Three-dimensional view – Pyramid (Anterior teeth), Tent (Posterior teeth)  Col • Interdental grooves EPITHELIUM

• Stratified squamous epithelium  Parakeratinized - 75% population  Orthokeratinized – 15 % population  Non keratinized – 10% population LAMINA PROPRIA Gingiva Cont’d… Gingiva Cont’d… Gingiva • A dense connective tissue - coarse collagen bundles • Papillae are long, slender, and numerous • Contains only few elastic fibers (oxytalan fibers) • Mucoperiosteum • Does not contain large vessels • Lymphocytes, plasma cells, and macrophages Alveolar mucosa • Fine collagen bundles • Papillae are quite low • Contains numerous elastic fibers Collagen Fibers of the Gingiva Gingiva Cont’d… Gingiva Cont’d…

• Gingival ligament • Support free gingiva • Bind attached gingiva to the alveolar bone and tooth • Link one tooth with the other • Groups of A. Dentogingival B. Longitudinal C. Circular D. Alveologingival E. Dentoperiosteal F. Transseptal G. Semicircular H. Transgingival I. Interdental J. Vertical Why lamina propria of gingiva differs from other regions?

• Arrangement of collagen fibers • Composition of matrix  Contains less of type III collagen, more of hyaluronan  Has a lower turnover rate • Response of its matrix to certain stimuli  Release more prostaglandin in response to histamine • Nature of the fibroblast  Has less contractile protein  Lacks alkaline phosphatase BLOOD AND NERVE SUPPLY Gingiva Cont’d… Blood Supply • Derived chiefly from the branches of the alveolar arteries • These branches anastomose with branches of the lingual, buccal, mental, and palatine arteries • Supply Interdental papilla and the adjacent areas of the buccal and lingual gingiva Lymphatic Drainage • Submental and submandibular lymph nodes Nerve Supply • Meissner or Krause corpuscles, end bulbs, loops, or fine fibers that enter the epithelium as “ultraterminal” fibers VERMILION (RED) ZONE Vermilion Zone Cont’d…

• The transitional zone between the skin of the lip and the mucous membrane of the lip • The line that separates the skin from the vermilion zone is termed the • Found only in humans Skin on the outer surface of the lip • Covered by a moderately thick, keratinized epithelium with a rather thick stratum corneum • The papillae of the connective tissue are few and short • Many sebaceous glands are found in connection with the hair follicles • Sweat glands occur between them Vermilion Zone Cont’d… Vermilion (Red) Zone • A thicker but mildly keratinized epithelium • Numerous, densely arranged, long papillae of the lamina propria, reaching deep into the epithelium  Carry large capillary loops close to the surface  Blood is visible through the thin parts of the translucent epithelium and gives the red color to the • The keratinization decreases towards the lip, but the thickness of the epithelium increases • The inner aspect of the lip is the thicker nonkeratinized labial mucosa • No glands For Questions & Queries: [email protected]

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