Digestive System

• Digestive Tract


  oral cavity, esophagus, stomach, small and large intestine, and anus
• Associated organs


  salivary glands, liver, pancreas, gallbladder
• Alimentary canal

  function is to obtain from ingested food the molecules necessary for the maintenance growth, and energy needs of the body
• Ingestion

  introduction of food and liquid into the oral cavity
• Mastication

  chewing, divides solid food into digestible pieces
• Motility

  muscular movements of material through the tract
• Secretion

  lubricating and protective mucus, digestive enzymes, acidic and alkaline fluids and bile
• hormone release


  local control of motility and secretion
• Chemical digestion


  enzymatic degradation of large macromolecules
• Absorption 


  small molecules and water into blood and lymph
• Elimination


  indigestible, unabsorbed, components of food
• Muscosa


  consists of an epithelial lining, an underlying lamina propia
• Mucosa


  a thin layer of smooth muscle called the muscularis mucosae
• Submucosa


  denser connective tissue with larger and lymph vessels
• Submucosa


  submucosal (Meissner) plexus of autonomic nerves
• Muscularis

  composed of smooth muscle cells organized as two or more sublayers
• Serosa


  outermost layer, thin layer of loose connective tissue, rich in blood vessels, lymphatics and adipose tissue, simple squamous covering epithelium or mesothelium
• Serosa

  continuous with the mesenteries
• Mesenteries

  thin membranes covered by mesothelium on both sides that support the intestine
• Peritoneum


  a serous membrane that lines the peritoneal cavity
• Keratinized epithelium of oral cavity

  masticatory mucosa gingiva (gums) and hard palate
• Nonkeratinized squamous epithelium of oral cavity


  lining mucosa over the soft palate, cheeks, floor of the mouth, and the pharynx, the posterior region of the oral cavity leading to the esophagus
• Internal mucous surface of lips

  a thick, non-keratinized epithelium and many minor labial salivary glands
• red vermillion zone of each lip


  covered by very thin keratinized stratified squamous epithelium and is transitional between the oral mucosa and skin
• outer surface of lips


  thin skin, consisting of epidermal and dermal layers, sweat glands, and many hair follicles with sebaceous glands
• tongue


  a mass of straited muscle covered by mucosa, which manipulates ingested material during mastication and swallowin
• Filiform papillae


  very numerous, elongated conical shape, heavily keratinized which gives gray or whitish appearance, provide a rough surface that facilitates movement of food during chewing
• fungiform papillae

  less numerous, lightly keratinized, interspersed among filiform papillae, mushroom-shaped with well-vascularized and innervated cores of lamina propia
• foliate papillae


  consist of several parallel ridges on each side of the tongue, anterior to the sulcus terminalis, but are rudimentary in humans, especially older individuals
• Vallate (or circumvallate) papillae

  the largest papillae, ducts of several small, serous salivary glands empty into the deep, moat like groove surrounding each vallate papilla
• Taste buds


  ovoid structures, stratified epithelium, sample the general chemical composition of ingested material, gustatory (taste) cells
• Enamel

  hard, thin, translucent layer of cellular mineralized tissue that covers the crown of the tooth
• dentin

  most abundant dental tissue, unique tubular structure and biochemical composition support the more rigid enamel and cementum overlying the surface of the tooth
• Cementum

  thin, pale-yellowish layer of bone like calcified tissue covering the dentin of the root of the teeth
• Esophagus

  a muscular tube, which transports swallowed material from the pharynx to the stomach
• mucosa of esophagus

  non-keratinized squamous epithelium
• submucosa of esophagus

  esophageal glands, esophageal cardiac glands
• mucosa of stomach

  simple columnar epithelium that invaginates deeply into lamina propia
• fundric glands (gastic glands)

  present throughout the entire gastric mucosa, simple, branched, tubular glands that extend from the bottom of the gastric pits to the muscularis mucosae
• Isthmus


  a short segment located between the gastric pit and the gland below