Digestive chapter 26

• Digestive system


  Ingests, mixes, transports and breaks down food; absorbs digested nutrients and expels wastes
• Bolus


  Food mixed with saliva
• Chyme


  Stomach converts bolus into
• Organs of the digestive system


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


  • Teeth
  • Tongue
  • Salivary glands
  • Liver
  • Gallbladder
  • Pancreas
• Digestive system functions


  • Ingestion
  • Motility
  • Secretion
  • Digestion
  • Absorption
  • Elimination of wastes
• Ingestion


  Introduction of materials into the mouth
• Motility


  Voluntary and involuntary contractions that mix and move materials through GI tract
• Peristalsis


  Ripple-like wave of muscular contraction that forces material to move further along the GI tract
• Mixing


  Churning movements in small intestine that disperse ingested materials and combine them with digestive secretions
• Secretion


  Release of mucin or fluids such as acid, bile, or digestive enzymes
• Digestion


  • Mechanical digestion
  • Chemical digestion
• Absorption


  Movement of molecules across GI tract epithelium and into the blood or lymph
• Elimination


  Defecation of indigestible waste products
• Oral cavity


  Lined by nonkeratinized stratified squamous epithelium
• Regions of oral cavity


  • Vestibule
  • Oral cavity proper
• Cheeks


  • Form the lateral walls of the oral cavity and are comprised mainly of the buccinator muscles
• Gingiva


  • Cover the alveolar processes of the teeth
• Labial frenulum


  • Thin, midline mucosa fold that attaches the internal surfaces of the lips to the gingivae
• Hard palate


  • Anterior two-thirds of the palate, formed by palatine processes of maxillae bones and palatine bones
• Soft palate


  • Posterior one-third of the palate, muscular
• Uvula


  • Extends posteriorly from soft palate, elevates during swallowing and closes off the posterior entrance to the nasopharynx
• Palatine tonsils


  • Housed between the two arches that represent the opening from the oral cavity to the oropharynx
• Tongue


  • Made mostly of skeletal muscle, manipulates and mixes ingested materials, helps compress them into a bolus, and assists in swallowing
• Lingual frenulum


  • Thin, midline mucous membrane that attaches the inferior surface of the tongue to the floor of the mouth
• Lingual tonsils


  • Located on the posteroinferior surface of the tongue
• Saliva


  Moistens ingested materials, moistens/cleanses/lubricates oral structures, begins chemical digestion of carbohydrates with amylase, has antibacterial action, dissolves food to stimulate taste receptors
• Salivary glands


  • Parotid glands
  • Submandibular glands
  • Sublingual glands
• Parotid salivary glands


  • Largest salivary glands, located anterior and inferior to the ear, secrete 25-30% of total saliva
• Submandibular salivary glands


  • Reside inferior to the body of the mandible, produce majority (60-70%) of saliva
• Sublingual salivary glands


  • Inferior to the tongue, contain multiple tiny ducts that open onto the inferior surface of the oral cavity, contribute 3-5% of total saliva
• Dentition


  Collectively known as the teeth
• Tooth structure


  • Exposed crown, constricted neck, one or more roots that fit into dental alveoli (sockets) and are connected to jaw bone with periodontal ligaments
• Tooth composition


  • Crown formed by tough enamel, dentin forms primary mass, pulp cavity contains connective tissue pulp, root canal continuous with pulp cavity
• Tooth types


  • Incisors
  • Canines
  • Premolars
  • Molars
• Deciduous teeth


  20 teeth that erupt between 6-30 months
• Permanent teeth


  32 teeth that replace the deciduous teeth
• Pharynx


  • Oropharynx and laryngopharynx have nonkeratinized stratified squamous lining, superior/middle/inferior pharyngeal constrictors within its wall participate in swallowing, innervated by CN X, supplied by branches of external carotid arteries, drained by internal jugular veins
• Peritoneum


  Moist serous membrane lining the abdominopelvic cavity, parietal peritoneum lines the body wall, visceral peritoneum covers internal organs
• Peritoneal organs


  • Intraperitoneal organs (completely surrounded by visceral peritoneum)
  • Retroperitoneal organs (only covered on anterolateral surfaces)