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2014-03-27 18:41:11
Digestive system

Digestive system
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  1. Explain the functions of the digestive system:
    • Processes food, extracts the nutrients from it, and eliminates the residue
    • Ingestion: intake
    • Digestion: mechanical, chemical breakdown
    • Absorption
    • Compaction
    • Defecation

    Food for: 1. Fuel- carbohydrates 2 . Raw materials- CHONS 3 . Essential nutrients- vitamins, minerals
  2. Describe the basic process of the digestive system:
    • Motility: mixing, propulsion
    • Secretions: exocrine (digestive juices) and endocrine(hormones)
    • Digestion: mechanical and chemical
    • Absorption:designed to maximize (not regulated)
  3. Distinguish between mechanical and chemical digestion:
    • Mechanical: the physical breakdown of food into smaller particles, exposes more food surface to the action of digestive enzymes
    • Chemical: a series of hydrolysis rxns that break down dietary macromolecules into their monomers,; carried out by digestive enzymes produced by the salivary glands, stomach, pancreas, and small intestine
  4. Put the following tissues in order from the lumen of the GI tract outward.

    longitudinal smooth muscle
    lamina propria
    circular smooth muscle
    • epithelium
    • lamina propria
    • submucosa
    • circular smooth muscle
    • longitudinal smooth muscle
    • serosa
  5. The __________ are used for grinding food, while the __________ puncture and shred food.

    molars, incisors
    incisors, premolars
    molars, canines
    premolars, molars
    canines, incisors
    molars, canines
  6. Peristalsis in the esophagus is initiated by:

    pacemaker cells
    voluntary control
  7. Which of the following helps prevent acid reflux?

    lower esophageal sphincter
    cardiac region of the stomach
    upper esophageal sphincter
    pyloric sphincter
    gastric rugae
    lower esophageal sphincter
  8. Referring to stomach secretions, _______ digests fat and ______ helps to absorb vitamin B12.

    gastric lipase, intrinsic factor
    somatostatin, pepsinogen
    pepsin, HCl
    serotonin, gastrin
    gastric lipase, intrinsic factor
  9. Which of the following organs stores and concentrates bile?

  10. Where does most fat digestion occur?

    large intestine
    small intestine
    small intestine
  11. Which of the following does NOT contribute to the regulation of gastric function?

    stretching of the duodenum
    sight, smell, thought of food
  12. Which of the following organs does NOT contribute to mechanical digestion?

    small intestine
  13. Put the following structures in order as food passes through the digestive system:

    decending colon
    ascending colon
    transverse colon
    • pharynx
    • stomach
    • duodenum
    • jejunem
    • ileum
    • ascending colon
    • transverse colon
    • decending colon
    • rectum
  14. Which of the following is NOT an enzyme that hydrolyzes carbohydrates?

  15. Haustral contractions occur in which of the following organs?

    large intestine
    small intestine
    all of the above
    large intestine
  16. know the products of macomolecule digestion:
    • macromolecues
    • a. carbohydrates
    • b. proteins
    • c. fats

    • absorbable units (products)
    • a. monosaccharides (glucose, fructose, galctose)
    • b. amino acids
    • c. monoglycerides, fatty acids
  17. explain the location and fxn of the membranes of the digestive tract:
    • mesenteries: connective tissue sheets + adipose tissue
    • fxns: holds abdomial viserca in their proper relationship to each other, provide passageway for blood vessels and nerves, contain lymph nodes for immunity, isolates infection
    • lesser omentum: extends from liver to the superior margin of the stomach
    • greater omentum: lager, fatty "apron" from the inferior margin of the stomach, loosely covering the small intestines
  18. describe the structureal and fxn features of the layers of the GI tract:
    • mucosa
    • inner lining of digestive tract
    • epithelium
    • lamina propria - loose connective tissue
    • musclaris mucosae - thin layer, smooth muscle
    • increase surface area for absorption

    • submucosa
    • thick layer of loose conncetive tissue containing blood vessels and lymphatics
    • transport nutrients
    • submucosal nerve plexus - regulates secretions

    • muscularis externa
    • circular smooth muscle - narrowing motions
    • longitudinal smooth muscle - shortening motions
    • myenteric nerve plexus - regulates motility

    • serosa
    • visceral peritoneum (reduces friction)

    *plexuses - regulate, coordinate enteric nervous system (ENS), a subdivison of the ANS
  19. describe the regulation of the digestive tract:
    short (myenteric) reflexes: stretching or chemcial stimulation, myenteric nerve plexus stimulate contactions, such as peristalic contractions of swallowing, completely in the GI tract, separate of CNS

    long (vagovagal) reflexes: autnonmic nerve fibers, sensory signals to brain, and motor commands back to GI tract, PSNS increased activity, and SNS decreased activity

    paracrine secretions: histamine

    hormonal reflex: endocrine gland > capilliaries > target cell, gastrin and secretin
  20. describe the mouth as an accessory organ of the diegestive tract:
    fxns: ingestion, taste and sensory repsonses, mastication, chemical diegestion (starch), swallowing, speech, respiration

    teeth: masticate food, increase surface area of food for absorption, decrease particle size, chewing, mix with saliva for taste

    • incisors: used to bite off a piece of food
    • canies: act to puncture and shred food
    • premolars/molars: crushing and grinding food
  21. describe the salvia and the salivary glands as accessory organs of the diegstive tract:
    • secrete 1.0 to 1.5L of saliva/day
    • under ANS regulation
    • PSNS: stimulates the glands to produce abundant, thin slaiva rich in enzymes
    • SNS: brief, produces less abundant, thicker saliva with more mucus

    fxns: moistens/lubricates (mucus), digest starch (salivary amylase), dissolves food (taste), and antibacterail (lysozyme + IgA)

    parotid glands, submandibular, sublingual glands

    mumps is a parotid inflammation and swelling caused by a virus
  22. describe the pharynx and esophagus as accessory organs of the GI tract:
    • upper esophageal sphincter: closes + allows food bolus to pass down, keeps air out, pharyngeal constirctors muscles - force food downward when swallowing
    • lower esophageal sphincter: relaxes to admit food + protects the esophageal mucosa from teh erosive effects of stomach acid ("heartburn")
  23. describe the process of swallowing:
    • 1. tongue compresses food against palate to form a bolus
    • 2. bolus passes into pharynx. misdirection of bolus is prevented by tongue blocking oral cavity, soft palate blocking nasal cavity, and epiglottis blocking larynx
    • 3. upper esophageal sphincter constricts and blous passes downward
    • 4. peristalisis drives bolus down esophagus. esophagus constricts above bolus and dilates and shortens belown it
    • 5. lower esophageal sphincter relaxes to admit bolus to stomach

    • 2400x/day
    • gravity: how most goes to stomach, 1-2 seconds
    • peristalisis: how large food goes to stomach, 4-8 seconds

    *acid reflux: weak LES, aka "heartburn"
  24. define peristalsis:
    a wave of muscular contraction that pushes the bolus ahead of it, triggered by stretch receptors of the short reflex
  25. describe the fxns of the stomach:
    • food storage organ
    • digestion- mechanically breaks up food, liquifies it, begins chemical diegestion

    • *smooth muscles: lontiguidonal, circular, oblique
    • pyloric sphincter: "gate watcher"; regulates the passage of chyme into the duodenum
  26. describe the histology of the stomach walls, including the fxn of the cells:
    • rugae: mucosa and submucosa are flat, smooth when stomach is full, but as it empites, these layers form longitudinal folds called rugae, allows for digestion and absorption
    • mucous cells: secrete mucus
    • parietal cells: secrete hydrochloric acid and intrinsic factor
    • chief cells: secrete the enzymes gastic lipase and pepsinogen
    • G cells: hormones - gastrin + paracrine messangers (histamine)

    • secretions: 2-3L/day
    • food + gastric secretions = chyme
  27. Know the fxn of HCl as a gastric secretion:
    • HCl has a pH ~ 1
    • stimulated by: PSNS (ACh), histamine, gastrin
    • fnxs: dissolves food/denatrues proteins, kills bacteria - non specific resistanc, activates pepsin and gastric lipase

    indicators: heartburn, ulcers; prilosec - proton pump inhibitor
  28. know the fxn of pepsin as a gastric secretion:
    • inactive proteins called zymogens are converted into active enzymes by the removal of some amino acids
    • pepsinogen (zymogen), HCl removes some amino acids and coverts it to pepsin
    • fxn: digest proteins to shorter peptide chains, which then pass to small intestine
  29. know the fxn of intrinsic factor as a gastric secretion:
    • secreted by parietal cells
    • fxn: essential to the absorption of vitamin B12 by the small intestine (ileum)
    • without B12 hemoglobin cannot be synthesized and pernicious anemia develops
  30. describe the process of gastric motility:
    • arriving food stretches the stomach, activates receptive-relaxation response in which the stomach relaxes to accomodate more food
    • peristalic waves: set by pacemaker cells in stomach of longitudinal layer, deploarization, action potential, then waves
    • 3 waves/min
    • strong wave: increased smooth muscle
    • small wave: about 3 or 4 mL of chyme squirt thru to the dudenum each time
    • neural imput: increased number of action potentials, increased contraction force
  31. describe the digestion and absorption that is occuring in the stomach:
    • mechanical digestion: big peices into small peices
    • chemcial digestion: 15% of protein diegstion by pepsin, 10-15 % of fat digestion by gastric lipase
    • not much absorption, except for some drugs (asprin)
  32. describe the cephalic phase of gastric regulation:
    • the stomach responds to the sight, smell, taste, or thought of food
    • vagus nerve stimulates gastric secretions before food is swallowed
    • thought, sight, smell > PSNS activity (to stomach via vagus) > increased secretions, increased motility
  33. describe the gastric phase of gastric regulation:
    • food in the stomach activates gastric activity
    • increased pH, increased enzymes, increased PSNS (vagus) + ENS
    • ACh (secreted by PSNS), histamine, and gastrin stimulate (increase) gastric secertions and increase motility
    • food stretches the stomach and activates myentertic nerve plexus and vagovagal reflex
  34. describe the intestinal phase of gastric regulation:
    • doudenum responds to arriving chyme, moderates gastric activity
    • stimulators: stretch, amino acids, fats, acid
    • enterogastric reflex: duodenem sends inhibitory signals to teh stomach by way of enteric nervous system
    • intestinal gastrin stimulate the stomach - secretin, cck, enterogastric relex inhibit gastric secretions and motility, while duodenum process chyme. sympathetic nerve fibers suppress gastric activity while vagus (PSNS) stimulation of stomach is inhibited

    • decreased PSNS, increased SNS
    • increase secretin and increase CCK
    • decreace gastric secretion, decrease motiltiy

    • slow stomach emptying of chyme, gives duodenum time to work
    • digest speed: fast - 2-4 hrs toast, carbs//slow 4-6 hrs bacon eggs
  35. describe the liver as a accessory organ to the small intestine:
    • largest gland: 3 lbs
    • fxns: secretes bile, detoxifies blood before leaving GI tract
    • *blood flows to liver via hepatic portal vein
  36. describe the fxn of the gallbladder:
    stores/concentrates bile
  37. describe the secretions of the liver:
    • bile: contains minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids
    • bilirubin: decomposition of hemoglobin, color stool brown
    • bile acids (bile salts): steroids synthesized from cholesterol
    • lecithin: a phospholipid that aid in fat digestion and absorption

    * bile flow: recycled several times, only way to eliminate cholesterol

    about 5% of bile salts are lost in feces
  38. describe the pancreas as an accessory organ to the small intestine:
    • pancreatic duct: runs lengthwise, joins bile duct at hapatopancreatic sphincter
    • hepatopancreatic sphincter: controls the release of both bile and pancreatic juice into the duodenum (sphincter of Oddi)
  39. describe the activation of pancreatic enzymes:
    • pancreatic zymogens (enzyme precursor) trypsinogen, converted to trypsin by enterokinase (secreted by mucosa of small intestine)
    • CCK (cholecystokinin): stimulatory effect on the gallbladder, increases bile flow, stimulation of pancreatic enzyme secretions, positive feedback mechanism on pacrease, gallbladder, negative feedback mechanism on stomach
    • secretin: stimulates an abundate bicarbonate solution
    • HCO3-: flueshes enzymes from pancreas
  40. describe the gross anatomy of the small intestine:
    • 9-12 ft. long, almost all digestion occurs here
    • duodenum: first 10 inches, receives stomach contents, pancreatic juice, and bile, and enzymes take over chemcial digestion
    • jejunum: next 40% of small intestine, thick, muscular, most digestion and absorption occurs here
    • ileum: last 60%, thin, less muscular, less vascular, B12/bile salt absorption
    • ileocecal sphincter: regulates passage of food residue into the large intestine; prevents feces from backing up
  41. describe intestinal secretions:
    • in addition to CCK + secretin, secrete intestinal juice
    • intestinal juice: water, mucus, NaCl, HCO3-
    • 1-2 L secreted/day
    • goblet cells: secrete mucus
    • intesintal cypts (pores): epithelial cells are sloughed off and digested
  42. describe the panacreatic secretions
    • both endocrine and exocrine secretions
    • endocrine: insulin and glucagon secreted into the blood
    • exocrine: carry thur a duct - digestive enzymes into duodenum (lipase, amylase), zymogens (becoming proteases), duct cells secrete sodium bicarbonate, the bicarbonate buffers HCl arriving from the stomach
  43. describe the microscopic anatomy of the small intestine, in particular the strcutures that support absorption:
    • circular folds: promotes more thorough mixing and nutrient absorption
    • villi: finger-like projections, increase surface area 600x(200-300m2), increase absorption efficency
    • microvilli: brush border, increase absorptive surface area, carry out final stages of chemcial digestion, contact digestion - chyme must contact brush border, enzymes are not secreted into lumen
    • lymphatic vessels: absorbe fats/soluble vitamins, absorbed into lymph, "milky" consistancy
  44. describe the digestion and absorption of carbohydrates:
    • most diegstiable carbohydrate is starch
    • first digested into oligosaccharides ( 8 glcuose residues long), then 2nd into disaccharide maltose, finally into glucose, which is absorbed by small intsetine
    • process begins in the mouth: salivary amylase hydrolizes starch inot oligosaccharides
    • pancreatic amylase: chyme mixes with pancreatic amylase, converted to oligosaccharides an maltose
    • complete digestion: chyme contacts brush border, maltase hycroslyzes maltose to glucose, immediately absorbed
  45. describe the digestion and absorption of proeints:
    • Mouth: no digestion
    • stomach: pepsein hydrolyzes certain peptide bonds, breaking them into shorter polypeptides and small amount of free amino acids, about 10-15% of dietary protein digestion
    • pancrease: trypsin and chymotrypsin take over protein digestion by hydrolyzing polypeptied chains into short oligopeptides
    • brush border enzymes: dipeptidase, aminopeptidase take apart one amino acid at a time

    absorption: action by the brush border enzymes, contact digestion, absorbed as amino acids

    *absorptive cells of infacts can take up intact proteins, and release them into the blood, this allows IgA from breastmilk to pass into infants bloodstream and confer passive immunity from mother to infant
  46. describe the digestion of fats:
    • lingual lipase: digests small amount of fat in the mouth
    • gastric lipase: 10-15% of dietary fat digested
    • pancreatic lipase: 85-90% fat digestion, emulsification droplets - contain lecithin and bile acids - attracted to the surface of fat globule, agitation by intestinal segmentation breaks up fat into droplets and coating of lecithin and bile acids keeps it broken up, exposing more surface area for enzymatic action

    products of lipase action: two free fatty acids, and one monoglyceride
  47. describe the absorption of fats:
    • micells: hydrophobic side faces inward, bile phospholipids and cholesterol diffuse into the enter of the micelle, micelle passes down bile duct into duodenum, they absorb fat soluble vitamins, more choesterol, and the FFA and monoglycerides of fat digestion, then absorbed in small intestin
    • within brush border, FFA and monoglycerides are resynthesized into triglycerides, golgi complex forms chylomicrons, they are taken into the lymph, thur lymphatics to blood
  48. describe the absorbtion of vitamins, minerals, and water:
    • fat soluble vitamins: A, D, E - absorbed with other lipids as described in lipid absorption
    • water soluble vitamins: C, B - absorbed by simple diffusion
    • vitamin B12: absorbed only if bound to intrinsic factor
    • minerals: electrolytes, absorbed by simple diffusion, and active transport
    • water: absorbed by osmosis, follwing the absorption of salts and nutrients that create an osmotic gradient
  49. describe in general the seretions and absorptions of the GI tract:
    • fluids: 8 - 9L/day - 85%
    • secretions 7L/day
    • food and drink: 99% absorbed, 1200 mL water, 800g solids per day ingested
    • salivary secretions: 1500 mL
    • gastric secretions: 200 mL
    • bile: 500 mL
    • pancreatic secretion: 6700 mL

    excretion of cells: 17 billion/day, whole epithelium replaced in 5 days (susceptical to cancer drugs)
  50. describe the motility of the small intestine:
    • segmentation: a movement in which stationary ringlike constricitons appear at several places along the intestine and then relax as new constrictions form elsewhere
    • used to churn chyme and bring it into contact with the mucosa for contact digestion and nutrient absorption
    • 12x/min in the duodenum, 8-9x/min in the ileum
    • less frequent distally, slow progression of chyme toward colon, intensity is modified by nervous and hormonal influences
    • migrating motor complex: peristalic wave, become successive and overlapping, milk chyme toward colon over 2 hr period, removes remaining food, limits bacterial infection
    • enhanced segmentation in the ileum relaxs the sphincter, cecum fills with residue, sphincter shuts prevents reflux of cecal contents
  51. describe the gross anatomy of the large intestine:
    • about 4 ft. long, less surface area, no villi, trillions of bacteria (800 species)
    • cecum: ileocecal sphincter
    • appendix: populated with lymphocytes, source of immune cells
    • ascending, transverse, decending colon
    • sigmoid colon: s-shaped
    • rectum: straight
    • internal anal sphincter: smooth muscle
    • external anal sphinctre: skeletal muscle
  52. describe the roles of the large intestine:
    • temporary storage
    • removes water
    • concentrates undigested material (500ml - 150 ml)
    • secretions: mucus (goblet cells)
    • digestion: bacteria digestes cellulocse, absorbable sugars > absorption > sugars from bacterial metabolism > nacl, water vitamins K and B
  53. describe the motility of the large intestine:
    • haustral contractions: occur every 30 mins, churns, mixes the residude promotes water and salt absorption, passes residue distally to another haustral
    • mass movement: occur 1-3 times/day, triggered by the filling of the stomach and duodenum, occur in the transverse and sigmoid colon
  54. describe the defecation reflex including neural control:
    • stimulated by the stretching of the rectum
    • intreinsic defecation: myentereic nerve plexus, stretch singals of plexus in descending and sigmoid colon and rectum, activates peristalic wave that drives feces downward, relaxes internal anal sphincter
    • parasympathetic defecation reflex: stretch singal to spinal cord, motor signal returns by way of pelvic nerve to intensify perilstalsis in decending and sigmoid and rectum, and to relax internal anal sphincter
    • **these are involuntary control, infants and spinal cord injuries

    • voluntary control
    • external anal sphincter: must be voulunarily relaxed, prolonged distortion > reversed peristalis > contents moved backwards until next mass movement
  55. monosaccharides are a product of ____ digestion.

    A. protein
    B. carbohydrate
    C. nucleic acid
    D. lipid
    B. carbohydrate
    (this multiple choice question has been scrambled)
  56. which of the following is NOT consicered an accessory organ/structure of the digestive system:

    A. teeth
    B. salivary glands
    C. liver
    D. spleen
    D. spleen
    (this multiple choice question has been scrambled)
  57. which type of muscle in the GI tract is invlolved in shortening motions, like those that occure during perstalsis?

    A. transverse
    B. oblique
    C. longtiudinal
    D. circular
    C. longtiudinal
    (this multiple choice question has been scrambled)
  58. which of the following is NOT a fxn of saliva?

    A. digest starch
    B. digest protein
    C. moisten/lubricate food
    D. kill bacteria
    B. digest protein
    (this multiple choice question has been scrambled)
  59. in the stomach, ________ binds to vitamin B12 and ____ digests proteins.

    a. pepsin, Hcl
    b. gastric lipase, intrinsic factor
    c. gastrin, trypsin
    d. intrinsic factor; pepsin
    intrinsic factor; pepsin
  60. heartburn can result from a weak:

    A. lower esophageal sphincter
    B. ileocecal sphincter
    C. upper esophageal sphincter
    D. pyloric sphincter
    A. lower esophageal sphincter
    (this multiple choice question has been scrambled)
  61. the sight, smell, and thought of food increases as the secretions and motility of the stomach. This is called the ____ phase of gastric regulation:

    A. modulary
    B. intestinal
    C. oral
    D. cephalic
    E. gastric
    D. cephalic
    (this multiple choice question has been scrambled)
  62. which of the following is FALSE?

    A. CCK and secretin are hormones secreted by the pancrease
    B. the sphincter of Oddi regulates the secretion of bile and pancreatic enzymes into the duodenum
    C. most digestion and absorption occur in the jejunum of the small intestine
    D. the ileum has less muscle and vasculature than the jejunum
    A. CCK and secretin are hormones secreted by the pancrease
    (this multiple choice question has been scrambled)
  63. CCK (cholecystokinin) does all of the following EXCEPT:

    A. decreases gastric activity
    B. stimulates the pancrease to release HCO3-
    C. stimulates the pancreas to release digestive enzymes
    D. stimulates the gall bladder to release bile
    B. stimulates the pancrease to release HCO3-
    (this multiple choice question has been scrambled)
  64. bile is made by the _____, stored in the _____, and aids in the digestion of ______.

    A. pancreas; gall bladder; proteins
    B. liver; gall bladder; fats
    C. pancreas; small intestine; carbohydrates
    D. liver; pancreas; fats
    B. liver; gall bladder; fats
    (this multiple choice question has been scrambled)