the digestive system

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139shay
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117618
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the digestive system
Updated:
2011-11-26 19:06:02
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final exam
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the digestive system
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  1. liver
    • - heaviest gland of the body
    • - has right and left lobe
    • - liver is composed of hepatocytes , bile canaliculi , hepatic sinusoids
    • - another job of the liver is to clean out damaged RBCs
  2. hepatocyte are
    • - major functional cells of liver
    • - wide variety of metabolic , secretory , and endocrine functions
    • - secrete bile
  3. bile canaliculi
    • - ducts between hepatocytes that collect bile
    • - collect bile from hepatocytes
    • - bile then passed into bile ductules and then bile ducts
    • - bile ducts merge to form right and left hepatic ducts which unite and exit the liver as common hepatic duct
  4. hepatic sinusoids
    • - highly permeable blood capillaries between row of hepatocytes
    • - receive oxygenated blood from hepatic artery and deoxygenated nutrient-rich blood from hepatic portal vein
  5. common hepatic duct
    joins cystic duct from gallbladder to form common bile duct
  6. liver
    • - portal triad
    • - a bile duct branch of the hepatic artery and branch of the hepatic portal vein
  7. function of ballbladder
    • - store and concentrate bile , produced by the liver until it is needed in the small intestine
    • - absorbs water and ions to concentrate bile up to ten-fold
    • - contraction of smooth muscle fibers eject contents of gallbaldder into cystic duct
  8. blood supply of the liver
    • - liver received blood from the hepatic artery carrying oxygenated blood
    • - hepatic portal vein carry deoxygenated blood with newly absorbed nutrients , drugs , and pssibly microbes and toxins form GI tract

    • - branches of hepatic artery and hepatic portal vein carry blod into liver sinusoids
    • - oxygen , most nutrients , and certain toxic substances are taken up by hepatocytes
    • - products manufactured by hepatocytes and nutrients needed by other cells are secreted back into the blood
    • - sinusoid drains into central vein whic eventually passes into a hepatic vein
  9. role and composition of bile
    • - mostly water , bile salts , cholesterol , lecithin , bile pigments , and several ions
    • - partially excretory product / partially digestive secretion
    • - bile release increases during digestion
    • -
  10. bile salts play role in
    • - emulsification
    • - breakdown of large lipid (fat) globules into a suspension of small lipid globules
    • - aids digestion and absorption of lipids in small intestine
  11. bilirubin
    • - principal bile pigment ( yellow )
    • - derived from heme of recycles RBCs
    • - breakdown product stercobilin gives feces brown color
  12. function of the liver
    • - synthesis and secretion of bile
    • - carbohydrate metabolism
    • - lipid metabolism
    • - protein metabolism
    • - processing fo drugs and hormone
    • - inactivation of toxins
    • - excretion of bilirubin
    • - synthesis of plasma proteins
    • - storage of vitamins and minerals
    • - phagocytosis
    • - activation of vitamin D
  13. small intestine is the primary site of
    • - digestion and absorption of nutrients
    • - large surface area
    • - length 10feet living 21 feet in a cadaver
    • - circular folds ( pilcae ) villi , and microvilli
  14. small intestine has 3 regions
    • 1. duodenum
    • 2. jejunum
    • 3. lleum
  15. mucosa of the small intestine
    • - simple columnar epithelium that contains many types of cells
    • - absorptive cells : digest and absorb nutrients in chyme
    • - goblet cell : secrete mucus
    • - intestinal glands crypts of lieberkuhn : secrete intestinal juice
    • - paneth cells : secrete lysozyme and are capable of phagocytosis destorys bactreria
    • - solitary lymphatic nodules , peyer's pathes ( aggregated lympatic follicles )
  16. submucosa of small intestine
    - dudoenal ( brunner's ) gland
  17. serosa of small intestine
    completely surrounded except for major portion of duodenum
  18. villi of small intestine
    • - fingerlike projections of mucosa
    • - contains arteriole , venule , blood capillary and lacteal in lamina propria
  19. microvilli of small intestine
    • - projections of apical membrane of absorptive cells
    • - brush border : forms a fuzzy line because too small to be seen individually with a light microsocope
    • - brush border : enzymes
  20. intestinal jucie
    • 1-2 liters secreted daily
    • - contains water and mucus , slightly alkaline
    • - provide liquid medium aiding absorption
  21. brush-border enzymes
    • - synthesized by and inserted into plasma membrane of microvilli of absorptive cells
    • - some enzymatic digestion occurs at surface of cells rather than just in lumen
    • - a-dextrinase , maltalse , sucrase, lactase : digest carbohydrates
    • - aminopetidase , dipeptidase : digest proteins
    • - nucleosidases and phosphatases: digest nucleotides
  22. mechanical digestion is governed by
    • - myenteric plexus
    • - segmentaions: localized , mixing contractions , mix chyme and bring it in contact with mucosa for absorption
    • - begins in lower portion of stomach and pushes chyme forward
  23. chyme entering small intestine contains
    • - partially digested carbohydrates , proteins , and lipids
    • - completion of the digestion is a collective effort of pancreatic juice , bile and intestinal juice in the small intestine
  24. carbohydrates
    • - pancreatic amylase
    • - a-dextrinase , sucrase , lactase , maltase in brush border
    • - ends with monosaccharides which can be absorbed
  25. proteins
    • - trypsin
    • - peptidases ( aminopeptidase and dipeptidase ) in brush border
  26. large intestine function
    - complete absorption , produce certain vitamins and form and expel feces
  27. 4 regions of the large intestine
    • cecum
    • colon
    • rectum
    • anal canal
  28. sections of the colon
    • ascending
    • transverse
    • descending
    • sigmoid
  29. opening of anal canal
    • -anus
    • - guarded by internal anal sphincter of smooth muscle = interanl involuntary
    • - and exteranl anal sphincter of skeletal muscle = external voluntary
  30. layers of large intestine
    • - mucosa : simple columnar epithelium with mostly absorptive and goblet cells
    • - arranged in tubular intestinal glands ( crypts of lieberkuhn )
    • - no circular folds or villi
    • - has microvilli on the absorptive cells
    • - muscularis : longitudinal muscle modified to form three bands called teniae coli
    • - forms haustra ( pouches ) which gives puckered appearance to colon
  31. haustral churning
    • - haustra fill up , contract and squeeze contents into next haustrum when distension reaches a certain point
    • - peristalsis : slower than in more proximal portion of tract
    • - mass peristalsis : starts in middle of transeverse colon and quickly drives contents of colon toward rectum
    • - stimulated by food in stomach ( gastrocolic reflex )
  32. final stage of digestion through bacterial action occurs in the colon
    • - no enzymes are secreted
    • - ferment carbohydrates
    • - produce some B vitamins and vitamin K
    • - convert any remaining proteins into simpler substances
    • - release hydrogen , carbon dioxides , and methane gases ( flatus )
  33. decompose bilirubin to stercobilin
    gives feces their brown color
  34. feces formation
    remaining water absorbed along with ions and some vitamins
  35. feces consist of
    • water
    • inorganic salts
    • sloughed off epithelial cells from mucosa of GI tract
    • bacteria
    • products of bacterial decomposition
    • unabsorbed digested materials
    • indigestible parts of food
  36. defecation reflex
    • - empties of rectum
    • - stretch receptors and initialtes defecations reflex
    • - increasing pressure of longitudinal rectal muscles voluntary contractions of diaphragm and abdominal muscles opens internal anal sphincter
    • - if external anal sphincter is voluntarily relaxed defecation occurs and feces are expelled
    • - if external anal sphincter is voluntarily constricted decrecation is postponed
  37. diarrhea
    • - defecation
    • - increase in frequency , volume , and fluid content of feces
    • - caused by increased motility of and decreased absorption by intestines
    • - can result in dehydration and electrolyte imblances
  38. constipaton
    • - defecation
    • -infrequent of difficult defecation
    • - caused by decreased motility of intestines
    • - excessive water absorption occurs and feces become dry and hard
  39. phases of digestion
    • - cephalic phase
    • - gastric phase
    • - intestinal phase
  40. cephalic phase
    • - smell , sight , thought or initial taste of food activated neural centers
    • - sitmulates salivary glands and gastric glands
    • - prepares mouth and stomach for food to be eaten
  41. gastric phase
    • - begin one food reaches the stomach
    • - neural and hormonal mechanisms promote gastric secretions and motility
    • - stretch receptors detect distension
    • - chemoreceptors detect change in pH
    • - activate parasympathetic and enteric neurons and release of gastrin form G cells
    • - gastrin stimulates release of large amounts of gastric juice
    • - HCL lowers pH
  42. intestinal phase
    • - begins when food enters small intestine
    • - slows exit of chyme from stomach
    • - prevents small intestine from being overloaded with more chyme than it can handle
    • - distension of duodeum singnals nervous system to inhibit gastric motility ( enterogastric reflex )
    • - stimulates flow of bile and pancreatic juice
    • - mediated by two hormones secreted by small intestine
    • - cholecystokinin ( CCK )
    • - secretin
  43. lipids
    • - emulsification by bile salts increases surface area
    • - bile salts are amphipathic , they have both hydrophobic and hydrophilic regions
    • - break large lipid globules down into serveral small lipid globules
    • - gallbladder
  44. pancreatic lipase most important in
    triglyceride digestion
  45. ncleic acids
    - ribonuclease and dexoyribonuclease in pancreatic juice
  46. aborption passage of
    - passage of digested nutrients for GI tract through absorptive epithelial cells of mucosa and into blood or lymph
  47. absorption occurs via
    • . diffusion
    • . facilitated diffusion
    • . osmosis
    • . active transport
  48. majoraity of proteins are
    digested and absorbed
  49. all dietary lipids absorbed by
    - simple diffuison
  50. chylomicrons are broken down by
    liver and adipose cells for storage of triglycerides
  51. electrolytes
    - compounds that separate into ions in water and conduct electricity , has a charge
  52. fat soluble vitamins
    • A
    • D
    • E
    • K
    • - absorbed by simple diffusion and transported with lipids in micelles
  53. water soluble vitamins
    • B
    • C
    • - absorbed by simple diffusion
  54. water
    • - comes from ingestion
    • - GI secretions
    • - most absorbed in small intestine , some in the large intestine
    • - only 100ml excreted in feces
    • - all water absorption occurs by osmosis
  55. metabolism
    - is all the chemical reactions that occur in the body

    - metabolic reactoins harvest chemical energy from consumed nutrients to contribute to the body's growth , repair , and normal functioning
  56. food molecules absorbed by GI tract have three fates
    1. supply energy for sustaining life processes: active transport , DNA replication , protein synthesis , muscle contraction, maintenance of body temperature , mitosis

    2. building blocks for synthesis of more complex structural or functional molecules : muscle proteins , hormones , enzymes

    3. stored for future use : glycogen and triglycerides
  57. catabolism
    - break down complex molecules
  58. exergonic
    produce more energy than comsumed the of the energy is coverted into heat
  59. anabolism
    combine simple molecules into complex ones
  60. endergonic
    comsume more energy than they produce
  61. adenosine triphosphate (ATP)
    • - links anabolic and catobolic reactions for energy balance
    • - fuels chemical reactions
    • - energy currency
  62. oxidation
    • - removal of electrons from a compound
    • - decreases in potential energy
    • - liberated hydrogen atom transfereed immediately by coenzymes to another compound
  63. coenzymes
    • - nicotinamide adenine dinucleotide
    • - flavin adenine dinucleotide
  64. both carry and transfer molecules
  65. dehydrogenation
    removal of hydrogen atoms
  66. phopshorylation
    - addition of a phosphate group increases the potential energy for a molecule
  67. carbohydrate metabolism
    • - fate of glucose depends on needs of body cells
    • - ATP production or synthesis of amino acids , glycogen or triglycerides
    • - insulin causes insertion of more of these transporters in plasma membrane , increasing rate of entry into cells
    • - glucose is phosphorylated after entering a cell and beomes trapped with in cell
  68. oxidation of glucose to produce ATP involves four sets of reactions
    • 1. glycolysis
    • 2. formations of acetyl coenzyme A
    • 3. krebs cycle
    • 4. electron transport chain

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