bsci202 lab practical 3 - digestive system

• what are the functions of the digestive system?

  mechanical digestion: food breakdown by physical forces; prepares food for further degradation by enzymes

  chemical digestion: enzymes breakdown food molecules into their building blocks
• what are carbohydrates broken down into?

  simple sugars by the enzymes such as amylase, lactase, fructase
• what are proteins broken down into?

  amino acids by proteases such as trypsin
• what are fats broken down into?

  fatty acids and glycerol alcohols by lipases
• what are the organs of the alimentary canal?

  mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus
• what are the accessory organs of the digestive system?

  salivary glands, teeth, pancreas, liver, gallbladder
• what is the function of the mouth?


  mechanical processing, moistening, mixing with saliva
• what is the function of the pharynx?

  muscles propel materials into esophagus
• what is the function of the esophagus?

  transport materials to the stomach
• what is the function of the stomach?

  chemical breakdown of materials via acid and enzymes; mechanical processing through muscular contractions
• what is the function of the small intestine?

  enzymatic digestion and absorption of water, organic substrates, vitamins, and ions
• what is the function of the large intestine?

  dehydration and compaction of indigestible materials in preparation for elimination
• what is the function of the salivary glands?

  secretion of lubricating fluid containing enzymes that break down carbohydrates
• what is the function of teeth?

  mechanical processing
• what is the function of the pancreas?

  exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones
• what is the function of the gallbladder?


  storage and concentration of bile
• what is the function of the liver?


  secretion of bile (important for lipid digestion), storage of nutrients, many other vital functions
• what is the difference between segmentation and peristalsis?

  segmentation: churns and fragments a bolus

  peristalsis: causes waves that move a bolus
• what is the innermost layer of the alimentary canal?

  musosa

  • surface epithelium
  • small amount of connective tissue (lamina propia)
  • muscularis mucosau
• what is the submucosa?

  just beneath the mucosa

  • soft connective tissue with blood vessels, nerve endings, and lymphatics
• what is the muscularis externa?


  composed of two layers of smooth muscle

  • circular layer
  • longitudinal layer
• what is the serosa?

  the outermost layer of the wall contains fluid-producing cells, consists of the:

  • visceral peritoneum
  • parietal peritoneum
• what is saliva and its function?

  mixture of mucus and serous fluid; helps form a food bolus
• what is the process of deglutition?

  1. buccal phase: upper esophageal sphincter is closed; tongue presses against hard palate, forcing food bolus into oropharynx
  2. pharyngeal-esophageal phase: tongue blocks off mouth; upper esophageal sphincter relaxes, allowing food to enter esophagus
  3. constrictor muscles of pharynx contract, forcing food into esophagus inferiorly
• what are the 3 regions of the tooth?

  crown, neck, root
• what is the crown of the tooth?

  exposed part; consists of

  1. enamel: hardest substance in the body
  2. dentin: forms bulk of tooth
  3. pulp cavity: contains connective tissue, blood vessels, nerve fibers
• what is the neck of the tooth?

  region in contact with the gum; connects crown to root
• what is the root of the tooth?

  cementum: covers outer surface and attaches the tooth to the periodontal membrane
• what are the enzymes involved in food breakdown in the stomach?

  protein-digesting enzymes

  • pepsin
  • rennin
• what are the components of the muscular tube in the small intestine?

  cuodenum, iejunum, ileum
• what is the ileocecal shpinter?

  transition between small and large intestine
• what are the structures of the small intestine that increase surface area?

  microvilli, villi, circular folds
• what is the endocrine functions of the pancreas?

  secretion of insulin and glucagon