Digestive 1

• Digestive system


  Consists of 2 parts: Alimentary tract or Gastointestinal tract and Accessory organs
• Alimentary tract


  • Oral cavity
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Anus
• Accessory organs


  • Teeth
  • Tongue
  • Salivary glands
  • Liver
  • Biliary tract
  • Pancreas
• Lips


  • Orbicularis oris skeletal muscle and dense connective tissue
  • 3 divisions: Oral side, Skin side, Vermilion border
• Oral side of lips


  Lined by stratified squamous nonkeratinizing epithelium
• Skin side of lips


  • Stratified squamous, keratinizing epithelium
  • Outer portion covered by typical thin skin; has hair follicles, sweat glands, sebaceous glands
• Vermilion border


  • Free edge of the lips
  • Hairless very thin skin, transparent permitting the blood in the capillaries of the dermis to impart to it a red color
  • Highly vascularized
• Oral cavity


  Divided into vestibule and oral cavity proper
• Lined by Oral mucosa


  • Masticatory mucosa
  • Lining mucosa
  • Specialized mucosa
• Masticatory mucosa


  • Found in gums/gingiva, and hard palate
  • Keratinized or parakeratinized stratified squamous epithelium
• Parakeratinized epithelium


  Similar to keratinized epithelium except that the superficial cells do not lose their nuclei and that they are less stain with eosin
• Masticatory mucosa


  • Connective tissue papillae are present in large numbers to provide relative immobility during mastication, friction and shearing stress
• Lining mucosa


  • Stratified squamous, nonkeratinizing
  • Found in lips, cheeks/buccal mucosa, alveolar mucosal surface, floor of the mouth, inferior surface of the tongue, soft palate
• Lining mucosa


  Mobile structures with less connective tissue papillae to allow movement of the underlying muscles
• Specialized mucosa


  • Associated with sensation of taste
  • Found on dorsal surface of the tongue
• Tongue


  • Freely movable organ attached to the floor of the mouth and the hyoid bone
  • Consists of interlacing bundles of skeletal muscles which are oriented in all direction allowing high level of mobility
• Anterior 2/3 of tongue

  Covered by numerous excrescences called lingual papillae (4 types: filiform, fungiform, circumvallate, foliate)
• Filiform papillae


  Most abundant, keratinized, elongated conical in form and slightly curved backwards, no taste buds, mechanical role
• Fungiform papillae


  Have narrow base and slightly flattened, mushroom-shaped, visible with the naked eye, scattered taste buds on dorsal surfaces, lighty keratinized, Less numerous and scattered singly among filiform
• Lingual Papillae (Foliate papilla)


  Poorly developed in adults, best developed in children, parallel ridges and furrows on the sides of the tongue, with taste buds on the sides
• Circumvallate papillae


  Largest, dome-shaped, moat-like invaginations, number only 8-12 and are confined to in front of the sulcus terminalis, epithelium on the free surface is smooth and that on the sides of the papilla contains numerous taste buds
• Taste buds


  Pale ovoid bodies within the lingual epithelium, present on papillae and elsewhere in the dorsal and lateral surface of the tongue, each taste bud contain 50-100 cells
• Taste bud cells


  • Gustatory (taste/neurosecretory/neuroepithelial) cells
  • Supporting/Sustentacular cells
  • Basal cells (stem cells)
• Gustatory cells


  Have long microvilli or apical processes that extends to the taste pore to the free surface, tips of these apical processes are receptors for the sense of taste, arise from the basement membrane and synapse with the CN VII, CN IX, and CN X
• Posterior 1/3 of tongue

  Pharyngeal part or root of tongue, surface shows many bulges due to lingual tonsils and lymphoid nodules, lacks papillae
• Teeth


  • Deciduous or milk teeth: 20
  • Permanent or succidaneous teeth: 32
• Teeth


  • Bilaterally symmetric
  • Parts: Crown, Neck, Root
• Specialized tissues of teeth

  • Enamel
  • Dentin
  • Cementum
• Enamel


  Thin acellular layer that covers the crown of the tooth, produced by ameloblasts, 96-98% calcium hydroxyapatite, hardest substance in the body
• Enamel


  Can be decalcified by organic acids, trapped food products can bring acid-producing bacteria into the enamel surface = DENTAL caries
• Dentin


  Most abundant calcified material in the teeth, covers and protects pulp cavity, produced by odontoblasts, 70% calcium hydroxyapatite

  
• Tooth


  • Soft parts: Pulp cavity, Root canal, Apical foramen, Periodontal ligaments

  
• Hard Palate


  • Above is PSUEDOSTRATIFIED CILIATED COLUMNAR EPITHELIUM
  • Below is STRATIFIED SQUAMOUS EPITHELIUM, KERATINIZED & PARAKERATINIZED EPITHELIUM
• Soft Palate


  • Above is PSUEDOSTRATIFIED CILIATED COLUMNAR EPITHELIUM
  • Below is NON-KERATINIZED SQUAMOUS EPITHELIUM (Lining Mucosa)
• Lining epithelium of tunica mucosa

  • Stratified squamous epithelium
• Structure of the tongue

  • Sharp difference between the anterior 2/3 and the posterior 1/3
• Boundary between the anterior 2/3 and posterior 1/3


  1. Marked by a shallow V-shaped groove, the sulcus terminalis

  2. Apex of sulcus terminalis pointing towards the foramen of Cecum
• Glands of Von-Ebner


  Serous salivary glands
• Glands of Von-Ebner


  • Located adjacent to the moats surrounding the circumvalate and foliate pappilae
• Von Ebner's glands

  Secrete lingual lipase