Oral Histology

Home , Hard palate, Incisive papilla, Interdental papilla, Palate, Palatine raphe, Stippling (dentistry)

Oral Histology

Lec.14 Dr. Nada AL-Ghaban Types of oral mucous membrane 1-Masticatory mucosa

During mastication, parts of oral mucosa are subjected to forces & pressure like in Gingiva and Hard Palate GINGIVA Is a masticatory mucosa and covers the alveolar process of the jaw and surrounds the neck of the teeth. The gingiva extends from the dentogingival junction to the alveolar mucosa. The stratified squamous epithelium may be keratinized or nonkeratinized but most often it is parakeratinized. TYPES OF GINGIVA:-The gingiva is divided into three types: A)Free or unattached or marginal gingival B) Attached gingiva. C) Interdental papilla A) Free or unattached 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 inner side of it forms the gingival sulcus. 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. C) Interdental Papillae :

Part which extends between two teeth up to the contact point is called interdental papillae. It has a ‘facial side’ and a ‘lingual side’ . It’s margins are concave. Due to inflammation, interdental papillae looses it’s concavity COL : Connecting facial and lingual side of the interdental papilla (on proximal side) is an epithelial structure called COL. It’s concave shape means, gingiva is healthy. It becomes dome shaped, in gingival recession and inflammation. It is covered by non keratinized stratified epithelium. Gingival fibers :- Collagen fibers arranged in strong bundles that bind attached gingiva to the alveolar bone & tooth. They arise from the cervical area of cementum and from the outer surface of alveolar process (gingival group of p.d.l. fibers which are previously discussed in PDL lecture)which are divided into the following groups: 1- Dentogingival:Its fibers run from cervical cementum to lamina properia of gingiva 2-Dentoperiosteal :-Its fibers run from cementum to periosteum 3-Alveologingival:-Its fibers run from alveolar crest bone to lamina properia of gingiva 4-Circular: this small fibers run in circular arrangement around the tooth 5-Transseptal :the fibers run from cervical cementum of one tooth to cementum of adjacent tooth. MICROSCOPIC FEATURES OF GINGIVA Gingiva is made up of epithelium and connective tissue. The gingival epithelium can be studied under three headings:- Outer or oral epithelium(keratinized or parakeratinised ) , Sulcular epithelium & Junctional epithelium(non keratinised ). Oral epithelium: Faces the oral cavity, which covers the free and attached gingiva, its either keratinized or parakeratininized stratified squamous epith. The epith. ridges are long , slender-like and numerous, lacks separating submucosa

2 layer so its immovably attached to bone and teeth by coarse collagen fibers and has no glands. Sulcular epithelium : Faces the tooth without contacting it. Thin non-keratinised stratified squamous epithelium (no granulosum and corneum layers), extends from the coronal end of the junctional epithelium to the crest of the gingival margin. Acts as a semi-permeable membrane. Junctional epithelium : Provides contact between gingiva & tooth. Stratified squamous non-keratinised epithelium. 3-4 cells thick in early life, increasing to 10-20 later. Derived from the reduced enamel epithelium . Attachment to tooth by inner basal lamina . Attachment to gingival connective tissue by outer basal lamina. Hard palate :- The m.m. of the hard palate is fixed tightly to the underlying periosteum ,so its immovable. Its color is pink. In the palate there are grooves and ridges, all appeared to be adaptation to resist the force of mastication. The epith. is uniform in character throughout the hard palate, with a rather thick, firm and stratified squamous keratinized or parakeiratinized with numerous long papillae. The lamina properia is thicker in the anterior than in the posterior parts of the hard palate. Various regions in the hard palate differ because of the varying structure of the submucous layer, so the following zones can be distinguished: 1-Palatine gingiva: Adjacent directly to the teeth which is similar to the previously described gingiva but mucogingival junction is not present. 2- Median palatine raphe: Extends from the incisive papilla posteriorly. In median palatine raphe, it is difficult to differentiate between lamina propria & submucosa. Radiating from this raphe, transverse folds called palatine rugea which is formed of dense C.T. covered by epithelium.

3- The anterolateral area (fatty zone) :This area present between the raphe & the gingiva anteriorly. Its lamina propria is fixed to periosteum by bands of fibrous C.T. dividing the submucosa into compartments containing fat cells. 4- The postero-lateral area (glandular zone) : Present posterior to the fatty zone. The submucosa contains pure mucous glands. The fatty and glandular zones act as cushion. The C. T. of hard palate is thick anteriorly than posteriorly. Submucosa are present in Fatty zone and Glandular zone. Epitheial rete pegs are tall & numerous Mucosa 2-Lining Mucosa: Present in areas not subjected to high levels of friction but is mobile & distensible Firmly attached to underlying muscles like Soft Palate , Lip , Cheek , Ventral Surface of tongue. Loosely attached to underlying structures as bone, fascia or muscle like Floor of mouth , Vestibule and Alveolar Mucosa. 1-Alveolar mucosa: Its red, shiny and covering the alveolar bone separating from attached gingiva by mucogingival junction(Figure-3) . Its movable (loosely attached to periosteum by a loose well-defined sub mucosa contain mucous minor salivary glands. The epith.is thin, stratified squamous non keratinized and the papillae are low and often entirely missing. 2-Lip : We can recognize 3 parts of lip: Oral Mucosa of the lip covered by non keratinized stratified squamous epithelium .Minor salivary glands are present in the sub mucosa and fibers of orbicularis oris muscle are noted also. Vermillion zone of the lip is very thin keratinized epithelium that contains no adnexal skin structures (can contain sebaceous glands).

What gives the vermillion zone the red color?  Epithelium is thin  Epithelium contains eleidin, which is transparent semi-fluid clear substance present in the lamina lucida of the skin epithelium .  Blood vessels are present near the surface eleidin. 3-Soft palate: The mucous membrane on the oral surface of the soft palate is highly vascularized and reddish in color, noticeably differing from the pale color of the hard palate. The papillae of the connective tissue are few and short. The stratified squamous epithelium is nonkeratinized. The lamina propria shows a distinct layer of elastic fibers separating it from the submucosa. The latter is relatively loose and contains an almost continuous layer of mucous minor salivary glands.: 3-Specialized mucosa:

Dorsal surface of the tongue is rough and irregular divided into anterior ⅔ or body of the tongue and posterior ⅓ or base of the tongue by V-shaped lined called terminal sulcus. The body and the base of the tongue differ widely in the structure of the m.m. The anterior part can be termed as papillary and the posterior part the lymphatic portion. On the anterior part are found numerous papillae which are:

1-Filiform papillae: Makes up majority of the papillae and covers the anterior part of the tongue. They appear as slender, threadlike keratinized projections. These papillae facilitate mastication (by compressing and breaking food when tongue is apposed to the hard palate) and movement of the food on the surface of the tongue. The papillae is directed towards the throat and assist in movement of food towards

5 that direction. The covering epith. is keratinized, these papillae does not contain taste buds. 2-Fungiform papillae: Interspersed between the filiform are the isolated mushroom-shaped or fungiform papillae , which are round reddish prominences. Their color is derived from a rich capillary network visible through the relatively thin epith. Fungiform papillae contain a few taste buds

3-Circumvallate papillae: 8-10 vallate papillae in front of the V-shaped sulcus between the body and the base of the tongue connected to the substances of the tongue is at their narrow base, its free surface shows numerous secondary papillae that are covered by a thin, smooth epith. On the lateral surface of the papillae the epith. contains numerous taste buds.

4-Foliate Papilla: (Leaf-like). Present on the lateral margins of the posterior tongue.Consist of 4 to 11 parallel ridges that alternate with deep grooves in the mucosa and a few taste buds are present in the epithelium. They contain serous glands underlying the taste buds which cleanse the grooves.

Taste Buds:

Unique sense organs that contain the chemical sense for taste. Microscopically visible barrel-shaped bodies found in the oral epithelium.Usually associated with papillae of the tongue (circumvallate, foliate and fungiform). Also seen in soft palate, epiglottis, larynx, and pharynx.Referred to as neuroepithelial structures. But most correctly referred as epithelial cells closely associated with clib-shaped sensory nerve endings. These nerves arise from the chorda tympani in anterior tongue and glossopharyngeal in posterior tongue and come to lie among the taste cells. Each taste bud has 10 -14 cells. Majority are taste cells with elongated microvilli that project into the taste pore. (Epiglottis and larynx – Vagus nerve).

4 taste sensations: Sweet, salty, sour and bitter Sweet and salt: anterior tongue Sour: lateral tongue Bitter: region of circumvallate papillae. AGE CHANGES IN ORAL MUCOSA 1-Oral mucosa of an elderly patient has a smoother and dryer surface than younger patient, due to dry therapy or any systemic diseases. • 2- Epithelium appears thinner histologically. • 3-Flattening of epithelial ridges. 4-Reduction in no. of filiform papillae. 5- Langerhan’s cells become fewer with age, leading to decrease in cell mediated immunity. 6-Decrease in cellularity occurs in lamina propria with increase in collagen. 7- Sebaceous (Fordyce’s spots) glands of lips and cheeks increase with age. 8-Elderly post menopausal women, have symptoms such as dryness of mouth, burning sensations and abnormal taste.

Mucogingival junction between A(attached gingiva) and B(alveolar mucosa).C and E represent reticular and papillary portions of lamina properia respectively and D (epith.ridge).

Hard palate zones

Part-1 Part-2 Part-1 show Parakeratinized epithelium of gingiva, A: Connective tissue papilla, B: Rete pegs, and the presence of nuclei (*) in the stratum cornium. Part-2 show stippling of gingiva which can be observed clinically as little depressions on the surface – “orange peel”