Digestive system I Histology

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Digestive system I:

Digestive system I Dr Pankaj Maheria

Oral cavity:

Oral cavity

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Oral cavity first part of digestive system. Food is broken down into small pieces by teeth Moistened and lubricate by saliva which secreted by three pair of major salivary gland and minor salivary glands present in the oral mucosa. Two part: Vestibule Oral cavity proper Line by moist oral mucosa membrane or oral mucosa

Oral mucosa :

Oral mucosa Covering epithelium and underlying connective tissue. No muscularis mucosa. Lamina propria: Major blood vessels ,adipose tissue and glandular tissue often referred as submucosa . Gland Fordyce’ s spots Division of mucosa Masticatory mucosa Lining mucosa Specialized mucosa

Masticatory mucosa :

Masticatory mucosa Location : Area associated with mechanical trauma during mastication of food e.g. gingiva and mucosa over hard palate. Firm and immobile Attached to periosteum of underlying bone forming mucoperisteum Stratified squamous epithelium of masticatory mucosa Moderately thick and frequently parakeratinized

Lining mucosa :

Lining mucosa Soft and pliable Inner surface of lip , cheeck ,soft palate , floor of mouth and ventral surface of tongue. Epithelium : Thicker than that of masticatory mucosa. Nonkeratinized Basal surface: largely smooth and occasionally indented slender connective palillae . Lamian propria Thick Irregularly arranged collagen and elastic fibres . Submucosa : thick containing glandular tissue

Specialized mucosa:

Specialized mucosa Dorsum of tongue Functionally a masticatory mucosa Test buds

Lip :

Lip Fleshy mucocutaneous flaps forming the boundaries of oral fissure. Two : Upper Lower

Lip :

Lip Externally : Dry hairy skin Internally Wet mucous membrane Middle : Circularly arranged skeletal muscle

Lip :

Lip Red line or vermilion border Labial epithelium: Very thick Deep vascular papillae of lamina propria. Submucosa : Large labial glands

Gingiva :

Gingiva Masticatory oral mucosa surround the neck of tooth and common known as gum. Two part Free gingiva Attached gingiva Gingival sulcus or gingival crevice

Gingiva :

Gingiva Oral part of gingiva: A thick stratified squamous oral gingival epithelium , which become continus with sacular epithelium at the free gingival margin (Gingival crest) Sulcular epithelium : Thin Lack of epithelial ridges Smooth interface with lamina propria Frequently infiltrated by lymphocytes and plasma cells Junctional epithelium

Tooth :

Tooth Ingested food is masticated by the teeth Anchored to sockets of the alveolar processes of maxilla and mandible. Two set of teeth Deciduous or milk teeth (10 in each jaw) Permanent teeth (16 in each jaw) Both sets have similar histological strcutres

Tooth :

Tooth Part Crown Root Neck Pulp cavity or root canal

Tooth :

Tooth Type of tissue Hard part : dentine,enamel and cementum Soft part: dentinal pulp and periodontal ligament

Hard part : Dentine :

Hard part : Dentine Main bulk of the tooth surrounding pulp cavity and root canal Composition Organic 20% Inorganic 80% Formed by odontoblasts that line up pulp cavity, cells are mesodermal in origin Dentinal tubules

Hard part : Enamel :

Hard part : Enamel Hardest substance of body 99.5% inorganic salts Dentine of crown Formed by: Ameloblasts Enamel rods or prisms

Hard part : Cementum :

Hard part : Cementum Dentine of root. Structurally cementum similar to bone Formation: Cementoblats which later become cementocytes Laid continuously throughout life

Soft tissues : Dentinal pulp :

Soft tissues : Dentinal pulp Pulp cavity and root canal Made of loose aeolar CT containing neurovascular structure Apical foramen Covering A layer of odontoblasts

Periodontal ligaments:

Periodontal ligaments Fixes the root tooth to alveolar socket Compositions : Dense fibrous CT whose fibres are arranged in such a way as to avoid transmission of pressure directly to bone during mastication.

tongue:

tongue

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Muscular organ made of skeletal muscle covered by mucous membrane. Mucous membrane: stratified squamous epithelium which may show keratinization at places (specially at the tip of filiform palillae )

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Lamina propria Lingual gland Three type: Anterior lingual gland (mixed seromucous ) – at tip von Ebner’s glands (Serous) – related to vallate and foliate papillae Posterior lingual gland (mucous) – related to lingual tonsil. Duct open in central crpty so chance of tonsillitis is nil.

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Mucous membrane: Dorsal surface: rough due to lingual papillae and tonsil Ventral surface: smooth and slippery Sulcus terminalis Two part Oral , contain lingual papillae Pharyngeal , contain lingual tonsil

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Filiform Fungiform Circumvallate Foliate Diagram Distrubution Anterior two third ( morhirde at tip) Anterior two (among filiform ) In front of and parallel to the sulcus terminalis Posterior part of lateral margin Shape Conical with tip pinting toward pharynx Knob like with rounded top like a mashroom Inverted truncated cone with a flat top surrounded by a circular sulcus Cylindrical Secondary connective tissue papillae On all surface On all surface Only on top Mainly on top Taste bud Absent Few on top Many on lateral surface Many on lateral surface Glandular association Absent Present serous Present serous – van Ebner’s gland Present – serous

Taste buds:

Taste buds Present in epithelium of fungiform , circumvallate and foliate papillae of tongue, epiglosttis , soft palate and oropharynx . Appearance: Oval pale staining bodies embedded with the full thickness of the stratified squamous epithelium Extend from base to surface

Taste buds:

Taste buds Elongated spindle shaped cells arranged perpendicular to surface of epithelium Taste pore Free end :- microvilli (taste hairs) Type of cells : Taste or gustatory cells Sustentacular cells Basal or stem cells

Taste buds:

Taste buds Taste or gustatory cells (type II cells): Lightly stain Elongated cells Microvilli at apical ends. Unmyelinated nerve fibres

Taste buds:

Taste buds Sustentacular or supportive cells (type I cells) Darkly stain Elongated Microvillus at top Support the taste cells and also secret dense amorphous substance.

Taste buds:

Taste buds Basal cells or stem cells Small pyramidal cells Do not reach to top Give rise to taste and Sustentacular cells

Posterior third of tongue:

Posterior third of tongue

Salivary glands :

Salivary glands

PowerPoint Presentation:

Major salivary glands Three pairs Saliva secretion 600 – 1500 ml/ day which convey by to oral cavity by ducts Minor salivary glands Percentage of saliva: Parotid 20%, submandibular 70%, sublingual 5%, and minor glands 5% Function: Lubrication of oral cavity To initiate digestion of carbohydrates To cleanse the teeth.

Salivary secretory unit:

Salivary secretory unit

structure:

structure Striated duct intralobar in position Lined by low columnar epithelium Stained deeply with eosin. Characteristic feature of ion transporting cells Basal enfolding of plasma membrane Longitudinal orientation of mitochondria b/w enfolding

Difference b/w serous and mucous acini:

Difference b/w serous and mucous acini Serous Mucous Diagram Consistency for secretion Thin watery Thick viscous Nature of secretory granules Zymogen granules Mucigen droplets Shape n position of nucleus Round, central Flat, peripheral Size of lumen Small Large Appearance of cell boundaries Indistinct Distinct Staining with H&E Darkly stain Lightly stain Function Enzyme action protection n lubrication Example Parotid gland Sublingula

Comparison of gland:

Comparison of gland Parotid Gland Sublingual Gland Submandibular Gland

Clinical considerations::

Clinical considerations: Dry mouth ( xerostomia ): The dental term " xerostomia " means dryness of the mouth due to a decreased function of the salivary glands.

Effects of xerostomia::

Effects of xerostomia: 1-Dryness of the oral tissues, thus become more susceptible to infections. 2-Difficulty and pain in swallowing, eating and speech. 3-Increased incidence of dental caries especially cervically.

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Angular cheilitis Mumps Mucocele

Group for quiz.....:

Group for quiz..... Group no Roll no Group no Roll no 1 1 - 8 11 76-83 2 9-15 12 84-90 3 16- 22 13 91-98 4 23-30 14 99-105 5 31-38 15 106-112 6 39-45 16 113-120 7 46-53 17 121-128 8 54-60 18 129-135 9 61-68 19 136-143 10 69-75 20 144-150

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GOOD LUCK

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