Oral Cavity Histology PDF

Histology of oral cavity and pharynx Disease of oral cavity Objective To know the contents of oral cavity. To understand the structure and positions of oral tissues. To understand the general oral histology. To understand oral diseases and their causes.  Oral cavity Oral cavity...

Histology of oral cavity and pharynx Disease of oral cavity Objective To know the contents of oral cavity. To understand the structure and positions of oral tissues. To understand the general oral histology. To understand oral diseases and their causes.  Oral cavity Oral cavity contains:  Hard structures  Soft structures  Hard structures : Enamel, Dentine , Cementum Alveolar bone Jaw bones , Tempromandibular joint. Soft structures: Pulp , Gingiva , Periodontal ligament, Oral mucosa  Sub-mucosa , Salivary glands  Oral cavity cont. Oral cavity Extends from the lips to the oropharyngeal isthmus. The oropharyngeal isthmus: is the junction of mouth and pharynx. Is bounded: 1- Above by the soft palate and the palatoglossal folds 2- Below by the dorsum of the tongue  Oral mucosa  The oral cavity is lined with a mucous membrane,  Which is continuous with the skin near the vermilion border of the lips and with the pharyngeal mucosa in the region of the soft palate.  Oral mucosa cont. It is a moist lining of the oral cavity called oral Mucosa or oral mucous membrane. Has overlying oral epithelium and underlying connective tissue (lamina propria and submucosa) The function of oral mucosa is protection, sensation and secretion. It is continuous with the skin outside the oral cavity.  Oral mucosa cont. Structure of oral mucosa Epithelium Lamina propria Submucosa Oral epithelium forms the surface of the oral mucosa that forms a barrier between the oral environment and the deeper tissues. It is derived from the embryonic ectoderm.  Oral mucosa cont It is stratified squamous epithelium and may or may not be keratinized. beneath the epithelium lies the connective tissue The epithelium of the oral mucosa originates partly from the ECTODERM (lips, vestibule, gingiva, cheeks, palate, floor of the mouth), and partly from the endoderm (tongue). The interface between epithelium and connective tissue is comprised of a layer called basement membrane.  Oral mucosa cont. This interface is irregular and is composed of downward projections of epithelium called rete ridges or rete pegs, And upward projection of connective tissue termed as connective tissue papillae.  Epithelium Epithelium Epithelium of the oral cavity is stratified squamous epithelium. It may be 1. Keratinized 2. Non keratinized Keratinized layer can be para keratinized  Epithelium CONT… Keratinized oral epithelium Most of the oral mucosal surface is lined by non keratinized stratified squamous epithelium; Except gingiva, hard palate and dorsal surface of the tongue where the epithelium is keratinized The keratinized cells have no nuclei and the cytoplasm is displaced by large numbers of keratin filaments Keratinized epithelium is associated with masticatory function.  Epithelium CONT… Keratinized epithelium has four layers. The four layers are: Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Corneum  Epithelium CONT… 1. Stratum Basale The cells of the stratum basale are cuboidal or low columnar And form a single layer resting on the basal lamina Epithelium CONT… The basal lamina is at the interface of the epithelium and lamina propria New cells are generated in basal layer. Basal cells are made up of two populations: i) Serrated- heavily packed with tonofilaments which are adaptations for attachment. ii) Non-serrated – stem cells – slowly dividing cells which serve to protect genetic information of the tissue.  Epithelium CONT… 2. Stratum Spinosum Stratum spinosum is usually several cells thick They shaped like polyhedron with short cytoplasmic processes  Epithelium CONT… The stratum basale and the first layers of stratum spinosum are referred to as stratum germinativum Because, these cells give rise to new epithelial cells Cells are joined by intercellular bridges. Electron microscopy shows that the intercellular bridges are desmosomes and tonofibrils are bundles of tonofilaments.  Epithelium CONT… 3.STRATUM GRANULOSUM Cells of stratum granulosumare flat and are found in layers of three to five cells thick.  Epithelium CONT… This layer contains flatter and wider cells. This layer is named for basophilic keratohyalin granule layer that it contains. Nuclei shows degeneration Flatter & wider nuclei show signs of degeneration & pyknosis.  Epithelium CONT… 4. STRATUM CORNEUM Other name is cornified layer. Is made up of keratinized squamae which are larger and flatter than the granular cells.  Epithelium CONT… All nuclei and ribosomes and mitochondria have disappeared. The cells are densely packed with filaments in this non fibrous interfilamentous matrix protein. These cells are continuously being sloughed and are replaced by epithelial cells  Epithelium CONT… Types of keratinized epithelium Parakeratinized Epithelium :The superficial cells are dead but retain the nucleus Orthokeratinized Epithelium : The nuclei are lost in epithelium  Epithelium CONT…  Non keratinized oral epithelium Non keratinized epithelial cells in the superficial layers do not have keratin filaments in the cytoplasm The surface cells also have nuclei The stratum corneum and stratum granulosum layers are absent This epithelium is associated with lining of the oral cavity  Connective tissue  Connective tissue Connective tissue can be differentiated as Lamina Propria and Submucosa  Connective tissue CONT… Lamina propria Lamina propria is the connective tissue layer immediately below the epithelium It can be divided into papillary layer and the reticular layer Papillary layer forms finger like projections of connective tissue that extend deep in the epithelial layers  Connective tissue CONT… Papillary layer is prominent in masticatory mucosa and reticular layer is prominent in lining mucosa. Lamina prorpria consists of blood vessels and cells like fibroblasts, cells of blood vessels and lymphatics and nerves. Epithelium is avascular, hence its metabolic needs come via the vessels of the lamina propria.  Connective tissue CONT… Submucosa Submucosa lies below the lamina propria and serves as an attachment between lamina propria and bone or skeletal muscle It is found in the cheeks, lips and parts of the palate. It consists of large blood vessels, nerves and lymphatics and its functions are nutrition and defense.  Types of oral mucosa Organization of the Oral Mucosa 3 types according to function: Masticatory Mucosa:25% of total mucosa. Lining Mucosa:60% of total mucosa Specialized Mucosa:15% of total mucosa.  Types of oral mucosa cont.. A. MASTICATORY MUCOSA Free and attached gingiva and hard palate comes in primary contact with food during mastication and is keratinized. B. LINING MUCOSA The lips cheeks, vestibule, floor of the mouth, interior surface of the tongue and soft palate. It does not function in mastication and therefore has little attrition. It is soft, pliable and non-keratinized. SPECIALIZED MUCOSA On the dorsal surface (dorsum) of the tongue. It is covered with cornified epithelial papillae  Type of oral mucosa cont… A) Lining mucosa Lining mucosa covers all soft tissues of the oral cavity except the gingiva, hard palate and the dorsal surface of the tongue e.g Lip is covered by lining mucosa Type of oral mucosa cont… Lip with skin on outer surface and lining mucosa on inner surface.  Type of oral mucosa cont… B) Masticatory mucosa Masticatory mucosa covers the gingiva and hard palate. In edentulous mouth (toothless mouth), masticatory mucosa covers the chewing surface of the dental arches. e.g Gingiva Type of oral mucosa cont  Type of oral mucosa cont… C) Specialized mucosa Specialized oral mucosae is mucosa covering the dorsal surface of the tongue, lingual tonsils, gingival attachment to teeth, vermillion border of the lip.  Lips and cheeks Lips and Cheeks The lips are musculofibrous folds that are connected to the gums by superior and inferior frenula. The median part of the upper lip shows a shallow external groove, the philtrum. The lips consist (from external to internal) chiefly of skin. The three layers forming the skin can be identified in all skin sections.  Lips and cheeks cont… The epithelium forming the surface layer, the epidermis, is usually the darkest layer visible. Sublayers are visible in the epidermis. At the transition from the epidermis to the dermis, staining will become lighter. The lighter stained layer, the dermis, consists of dense irregular connective tissue. The dermis is much thicker than the epidermis.  Lips and cheeks cont… In thick skin, dermal papillae create a very irregular border between epidermis and dermis. The hypodermis is the lightest layer visible and consists mainly of adipose tissue. Dense connective tissue strands may extend from the dermis deep into the hypodermis. Lip is covered by lining mucosa VERMILION BORDER It is the junction between the skin & mucous membrane. The epithelium is thin. A protein eleidin is present, which is more transparent than the protein keratin.  Ectopic sebaceous glands are seen in the vermillion border at the corners of the mouth Or more laterally in the cheeks opposite to the molar teeth. These are called fordyce’s spots  Lips and cheeks cont… Cheek In the cheek the underlying submucosa contains fat cells and small mixed salivary glands  Gingiva Gingiva has keratinized or parakeratinzed epithelium with no submucosal layer. It develops from the union of oral epithelium and reduced enamel epithelium of the developing tooth. Gingiva can be classified as free gingiva, attached gingiva and interdental papilla.  Gingiva cont. A. Free gingiva (or marginal gingiva) It is that part of the oral mucosa that surrounds the necks of the teeth and forms the free margin of the gingival tissue It is differentiated apically from the attached gingival by the free gingival groove The free gingival mucosa is composed of stratified squamous epithelium that may be keratinized, parakeratinzed or sometimes nonkeratinized Gingiva cont… The inner side of it forms the gingival sulcus  Gingiva cont… B. Attached gingiva The attached gingiva lies between the free gingival groove and the alveolar mucosa. The junction of the attached gingiva and the alveolar mucosa is called mucogingival junction In healthy mouth attached gingiva shows stippling (orange peel appearance) which is a characteristic of this type of mucosa  Gingiva cont… C. Interdental papilla Interdental papillae are those parts of gingival tissue that appear in- between teeth apical to the contact points Interdental grooves extend vertically to the depressions between the roots  Gingiva cont. Confirming to the shape of the interproximal contact area is a valley like depression in the interdental papilla called Col. This depression lies in the facial and lingual plane  Gingiva cont... Junctional epithelium Junctional epithelium forms the seal of the gingival epithelium and the tooth. It forms the floor of the gingival sulcus and extends apically to the enamel of the tooth. Disturbances of epithelial attachment results in deepening of the sulcus which is a sign of gingival/periodontal disease.  Gingiva cont… Key point: Junctional epithelium readily regenerates from the sulcular epithelium or oral epithelium if it is damaged or surgically excised Connective tissue normally contains plenty of neutrophils which is different than the normal oral mucosa.  Hard palate Covered by masticatory mucosa Lateral regions of the posterior part contains palatine glands These glands are purely mucous glands The midline of the hard palate is called median raphe, where there is no submucosa. A series of folds appear in the anterior part of the palate called rugae.  Soft palate The soft tissue constituting the back of the roof of the mouth. The soft palate is distinguished from the hard palate at the front of the mouth in that it does not contain bone. Soft palate is covered by lining mucosa.  Tongue The tongue situated in the floor of the mouth, is attached by muscles to the hyoid bone, mandible, styloid processes, and pharynx. The tongue is important in taste, mastication, swallowing, and speech. It is composed chiefly of skeletal muscle, is partly covered by mucous membrane, and presents a tip and margin, dorsum, inferior surface, and root The tip, or apex, usually rests against the incisors and continues on each side into the margin.  Tongue cont… The oral part of the dorsum may show a shallow median groove.  Tongue cont… The mucosa has numerous minute lingual papillae: 1) The filiform papillae, the narrowest and most numerous; Pointed extension of keratinized epithelial cells Not associated with taste buds Primary columnar elevation of lamina propria. Epithelium over papillae – end in tapered points  Tongue cont… 2) Fungiform Papillae with rounded heads and containing taste buds Scattered, single, among filiform papillae Larger & fewer than filiform papillae Narrow stalk, rounded top Not keratinized Has one to several taste buds  Tongue cont… 3. CIRCUMVALLATE PAPILLAE Much larger than any of others About 8-12 located in post region of Tongue, just next to sulcus terminalis Visible with naked eye Lined with taste buds and also opening of serous gland Disease of oral cavity Diseases of the oral cavity divided into 2 groups, those affecting the soft tissues (include salivary glands) & those involving the teeth. Aphthous Ulcers (Canker Sores) Common superficial mucosal ulcerations Up to 40% of the population. Extremely painful Cause : unknown More prevalent within some families Disease of oral cavity CONT… May be associated with celiac disease, inflammatory bowel disease (IBD) and Behcet disease. Disease of oral cavity CONT… Resolve spontaneously in 7 to 10 days but can recur. Location: single or in groups on the nonkeratinised oral mucosa on the soft palate, buccolabialmucosa, floor of the mouth and lateral borders of the tongue Disease of oral cavity CONT… Herpes Simplex Virus Infections Aetiology : – Herpes simplex virus (HSV) type I, – HSV type II (herpes genitalis) Clinical features and pathogenesis: – Primary infection in children 2-4 yrs – Usually asymptomatic, dormant virus in the nerve ganglia & can be reactivated. – Some manifests as acute herpetic gingivostomatitis –generalised vesicles and ulcerations Disease of oral cavity CONT… Causes of reactivation: trauma, allergies, UV light exposure, URTI, pregnancy, menstruation, immune suppression, exposure to extreme temperature – Self healing, resolved within 7-10 days. – antiviral agents are available. Pathology : Gross: Solitary or multiple small (40 years old Risk factors: tobacco use, alcohol abuse, Human papillomavirus types 16 and 18 (oncogenic types) infection Disease of oral cavity CONT… Pathogenesis : chronic alcohol and tobacco users : exposure to carcinogens Disease of oral cavity CONT… Pathology : Gross : raised, firm, pearly plaque or irregular, rough or verrucous mucosal thickening.