ch 23

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ch 23
2014-06-17 03:09:17

digestive system
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  1. what are the two groups of organs for the digestive system
    alimentary canal (GI tract) and accessory digestive organs
  2. alimentary canal organs
    • mouth to anus
    • digests food nad absorbs fragments
    • mouth, pharynx, esophagus, stomach, small intestine, and large intestine
  3. accessory digestive organs
    • teeth, tongue, gallbladder
    • digestive glands: salivary, liver, pancreas
  4. what are the 6 essential activities
    • ingestion
    • propulsion
    • mechanical breakdown
    • digestion
    • absorption
    • defecation
  5. mechanoreceptors and chemoreceptors
    • respond to stretch, changes i osmolarity and pH, and presence of substrate and end products of digestion.
    • initiate reflexes that activate or inhibit digestie glands, stimulate smooth muscle to mix and move lumen contents
  6. intrinsic and extrinsic controls
    • short reflexes: enteric neve plexuses respond to stimuli in GI tract
    • long reflexes: respond to stimuli inside of outside GI tract; involve CNS centers and autonomic nerves
    • hormones from cells in stomach and small intestine stimulate target cells in same or different organs to secrete or contract
  7. peritoneum
    • serous membrane of abdominal cavity
    • visceral and parietal
  8. visceral peitoneum
    on external surface of most digestive organs
  9. parietal peritoneum
    lines body wall
  10. peritoneal cavity
    • between two peritoneums
    • fluid lubricates mobile organs
  11. mesentery
    • double layer of peritoneum
    • routes for blood vessels, lymphatics, and nerves
    • holds organs in place; stores fat
  12. retorperitoneal organs
    posteiror to peritoneum
  13. intraperitoneal organs
    surrouned by peritoneum
  14. hepatic portal circulation
    • drains nutrient rich blood form digestive organs
    • deliver it to the liver for processing
  15. four basic layers of the alimentary canal
    • mucosa
    • submucosa
    • musclaris externa
    • serosa
  16. mucosa
    • lines lumen
    • secrets mucus, digestive enzymes and hormones
    • absorbs end products od digestion
    • protects against infectious disease
    • 3 sublayers: epithelium, lamina propria and muscularis mucosae
  17. mucosa
    • lamina propria
    • loose areolar connective tissue
    • capillaries for nourishment and absorption
    • lymphoid follicles defend against microorganisms
  18. submucosa
    • areolar connective tissue
    • blood and lymphatic vessels lymphoid follicles and submucosal nerve plexus
  19. musclaris externa
    • responsible for segmentation and peristalsis
    • inner circular and outer longitudinal layers
  20. serosa
    • visceral peritoneum
    • areolar connective tissue covered with mesothelium in most organs
    • replaced by fibrous adventitia in esophagus
    • retroperitoneal organs have both an adentitia and serosa
  21. submucosal nerve plexus
    regulates glands and smooth muscle in the mucosa
  22. myenteric nerve plexus
    controls GI tract motility
  23. enteric nervous system
    • linked to CNS via afferent visceral fibers
    • long ANS fibers synapse with enteric plexuses: symphathetic impulses inhibit digestive activites and parasympathetic impulses stimulate digestive activities
  24. oral cavity
    • bounded by lips, cheeks, palate, and tongue
    • oral orifice is anterior opening
    • lined with stratified squamous epithelium
  25. vestibule
    recess internal to lips and cheeks, external to teeth and gums
  26. oral cavity
    proper lies within teeth and gums
  27. labial frenulum
    median attachment of each lip to gum
  28. tongue
    • skeletal muscle
    • functions: repositioning and mixing food during chewing, formation of bolus, initiation of swallowing, speech, taste
    • intrinsic muscles change shape of tongue
    • extrinsic muscles alter tongues position
    • lingual frenulum: attachment to floor of mouth
  29. filiform
    whitish, give the tongue roughness and provide friction; do not contain taste buds
  30. fungiform
    • reddish, scattered over tongue
    • contain taste buds
  31. circumvallate
    V sahped row in back of tongue; contain taste buds
  32. foliate
    on lateral aspects of posterior tongue; contain taste buds that function primarily in infants and children
  33. extrinsic salivary glands
    • parotid
    • submanibular
    • sublingual
    • produce most saliva
  34. functions of saliva
    • cleanses mouth
    • dissolves food chemicals for taste
    • moistens food
    • compacts into bolus
    • begins breakdown of starch with enzymes
  35. parotid gland
    • anterior to ear; external to masseter muscle
    • parotid duct opens into vestibule next to second upper molar
  36. submandibular gland
    • medial to body of mandible¬†
    • duct opens at base of lingual frenulum
  37. sublingual gland
    • anterior to submandibular gland under tongue
    • opens via 10-12 ducts into floor of mouth
  38. two types of secretory cells of salivary glands
    • serous cells: watery, enzymes, ion, bit of mucin
    • mucous cells: mucus
  39. what kind of tissue lines the pharynx
    • stratified squamous epithelium lining;
    • produces mucus
  40. esophagus
    • flat muscular tube from laryngopharynx to stomach
    • pieces diaphragm at esophageal hiatus
    • joins stomach at cardial orifice
    • gastoesophageal sphincter
  41. heartburn
    • stomach acid regurgitates into esophagus
    • likely with excess food drink, extreme obesity, pregnancy, running
    • also with hiatal hernia(structural abnormality)
  42. digestive processes of the mouth
    • ingestion
    • mechanical digestion (chewing)
    • propulsion
    • deglutition (swallowing)
    • chemical digestion (salivary amylase and lingual lipase)
    • no absorption, except for few drugs
  43. mastication
    • cheeks and closed lips hold food between teeth
    • tongue mixes food with saliva and compacts food into bolus
    • teeth cut and grind
    • partly voluntary
    • partly reflexive
  44. deglutition
    • involves tongue, soft palate, pharynx, esophagus
    • requires coordination of 22 muscle groups
    • buccal phase: voluntary contraction of tongue
    • pharyngeal esophageal phase: involuntary, primarily vagus nerve; control center in the medulla and lower pons
  45. what is the bolus called in the stomach
  46. cardial part of the stomach
    surrounds cardial orifice
  47. fundus part of the stomach
    dome shaped region beneath diaphragm
  48. body of the stomach
  49. pyloric valve
    sphincter that controls stomach emptying
  50. how many tunics does the stomach have
  51. muscarlis externa of stomach
    • three layers of smooth muscle
    • inne oblique layer alows tomach to churn, mix and move and physically break down food
  52. gastric gland cell types
    • mucous neck cells: secrete thin, acidic, mucus of unknown function
    • parietal cells
    • chief cell
    • enteroendocrine cells
  53. which gastric glands produce the most juice
    fundus and body
  54. parietal cell secretions
    • hydrochloric acid: denatures protein, activates pepsin, breaks down plant cell walls, kills many bacteria
    • intrinsic factor: glycoprotein required for absorption of vitamin B12 in small intestine
  55. chief cell secretions
    • pepsinogen: inactive enzyme; activated to pepsin by HCl and by pepsin itself
    • lipases: digest 15% of lipids
  56. enteroendocrine cells secretions
    • secrete chemical messengers into lamina propria
    • act as paracrines: serotonin and histamine
    • hormones: somatostatin and gastrin
  57. mucosal barrier of the stomach
    • protection
    • thick layer of bicarbonate rich mucus
    • tight junctions between epithelial cells
    • damaged epithelial cells quickly replaced by division of stem cells
  58. peptic or gastric ulcers
    • erosions of stomach wall
    • most caused by helicobacter pylori bacteria
    • some NSAIDS
  59. digestive processes in the stomach
    • physical digestion
    • denaturation of proteins by HCl
    • enzymatic digestion of proteins by pepsin
    • lingual lipase digests some triglycerides before digested as any other protein
    • delivers chyme to small intestine
    • lipid soluable alcohold and aspirin absorbed into blood
    • only stomach function essential to life:secretes intrinsic factor for vitamin B12 absorption
  60. three phase of gastric secretions
    • cephalic phase: conditioned reflex triggered by aroma, taste, sight, thought
    • gastric phase: lasts 3-4 hours, stimulated by distenion, peptides, low acidity, gastrin, enteroendocrine G cells stimualted by caffeine, peptides rising pH >gastrin
    • intestinal phase: stimulatory component, partially digested food enters smell intestine, brief intestinal gastrin release
  61. enterogastric reflex: three reflexes act to
    • inhibit vagal nuclei in medulla
    • inhibit local reflexes
    • activate sympathetic fibers > tightening of pyloric sphincter > no more food entry to small intestine
    • decreased gastric activity > protects small intestine from excessive acidity
  62. how much food can the stomach hold
    1.5 liters
  63. peristaltic waves move toward pylorus at what rate
    3 per minute
  64. how much chyme can the duodenum hold
    3 ml, or else it is forced back into the stomach
  65. chyme entering duodenum
    • receptors respond tos tretch and chemical signals
    • enterogastric reflex and enterogastrones inhibit gastric secrtion and duodenal filling
    • carb-rich chyme moves quickly through duodenum
    • fatty chyme remains in duodenum for 6 hours or more
  66. emesis
  67. what are the subdivisions of the small intestine
    • duodenum
    • jejunum
    • ileum
  68. small intestine
    • major organ of digestion and absorption
    • 2-4 m long; fro mpyloric sphincter to ileocecal valve
  69. duodenum
    • cures around head of pancreas
    • bile duct from liver and main pancreatic duct join at hepatopancreatic ampulla, enter duodenum at major duodenal papilla, entry controlled by hepatopancreatic sphincter
  70. jejunum
    • extends from duodenum to ileum
    • about 2.5 m long
  71. iluem
    • joins large intestine at ileocecal valve
    • about 3.6 lm ong
  72. structural modification of small intestine
    • increase surface area of proximal part for nutrient absorption
    • circular folds
    • villi
    • microvilli
  73. enteroendocrine cells release
  74. intraepithelial lymphocytes
    release cytokines that kill infected cells
  75. paneth cells
    secrete antimicrobial agents (defensins and lysozyme)
  76. intestinal juice
    • 1-2 liters secreted daily in response to distention or irritation of mucosa
    • slightly alkaline
    • largely water, enzyme poor
    • facilitates transport and absorption of nutrients
  77. liver
    • many functions; bile production
    • largest gland in body
    • four lobes: right, left, caudate, quadrate
  78. bile
    fat emulsifier
  79. gallbladder
    chief function is bile storage
  80. falciform ligament
    • separates larger right and smaller left lobes of liver
    • suspends liver form diaphragm and anterior abdominal wall
  81. round liagment
    remnant of fetal umbilical vein along free edge of ligamentiform ligament
  82. bile ducts
    • common hepatic duct: leaves liver
    • cystic duct: connects to gallbladder
    • bile duct: formed by union of common hepatic and cystic ducts
  83. liver lobules
    • hexagonal structural and functional units
    • composed of plates of hepatocytes (liver cells) filter and process nutrient rich blood
    • central vein in longitudinal axis
  84. liver sinusoids
    leaky capillaries between hepatic plates
  85. hepatocytes
    • increased rough and smooth ER, golgi, peroxisomes, mitochondria
    • functions: process bloodborne nutrients, store fat soluable vitamins, perform detoxification, produce 900 ml of bile per day
  86. bile salts
    cholesterol derivatives that function in fat emulsification and absorption
  87. bilirubin
    • pigment formed from heme
    • in bile
  88. gallstones
    • high cholesterol
    • too few bile salts
  89. pancrease
    • endocrine function: secrete insulin and glucagon
    • exocrine function: secrete pancreatic juice to duodenum via pancreatic duct
  90. pancreatic juice
    • 1200-1500 ml/day
    • watery alkaline solution neutralizes chyme
    • electrolytes
    • enzymes: amylase, lipases, nucleases secreted in active form but require ions or bile for optimal activity
    • protease secreted in inactive form
  91. CCK
    induces secretion of enzyme rich pancreatic juice by acini
  92. scretin
    causes secretion of bicarbonate rich pancreatic juice by duct cells
  93. vagal stimulation
    causes release of pancreatic juice
  94. digestion in small intestine
    • chyme from stomach contains partially digested carbs and proteins and undigested fats
    • 3-6 hours in small intestine, most water absorbed, all nutrients absorbed
    • small intestin, like sotmach, no role in ingestion or defecation
  95. requirements for digestion and absorption in the small intestines
    • slow delivery of acidic hypertonic chyme
    • dlivery of bile, enzymes and bicrbonate ions form liver and pancreas
    • mixing
  96. segementation
    • most common motion of small intestine
    • initiated by intrinsic pacemaker cells
    • mixes and move contents toward ileocecal valve
    • intensity altered by long and short reflexes; hormones
    • wanes in late intestinal phase
  97. peristalsis
    • initiated by rise in hormone motilin in late intestinal phase, every 90-120 minutes
    • each wave starts distal to previous
    • meal remnants, bacteria, and debris moved to large intestine
    • from duodenum to ileum it takes 2 hours
  98. ileocecal sphincter
    relaxes admits chyme into large intestine when gastroileal reflex enhances force of sementation in ileum
  99. unique features of the large intestines
    • teniae coli: three bands of longitudinal smooth muscle in muscularis
    • haustra: pocketlike sacs caused by tone of teniae coli
    • epiploic appendages: fat-filled pouches of visceral peritoneum
  100. regions of the large intestines
    • cecum
    • appendix
    • colon
    • rectum
    • anal canal
  101. cecum
    first part of large intestine
  102. appendix
    • masses of lymphoid tissue
    • part of MALT immune system
    • bacterial storehouse
  103. colon
    • retroperitoneal except for transverse and sigmoid regions
    • ascending colon
    • transcerse colon
    • descending colon
    • sigmoid colon
  104. rectum
    three rectal valves stop feces from being passed with glass
  105. anal canal
    • last segment of large intestine
    • opens to body exterior at anus
  106. internal anal sphincter
    smooth muscle
  107. external anal sphincter
    skeletal muscle
  108. digestive processes in the large intestines
    • residue remains in large intestine 12-24 hours
    • no food breakdown except by enteric bacteria
    • vitamins, water and electrolytes reclaimed
    • major functions: propulsion of feces to anus, defecation
    • colon not essential for life
  109. haustral contractions
    • slow segmenting movements
    • haustra sequentially contract in response to distention
  110. gastrocolic reflex
    • initiated by present of foo din stomach
    • activates three to four slow powerful peristaltic waves per day in colon
  111. diverticulosis
    • commonly in sigmoid colon
    • usually over 70 ppl gt affected
  112. diverticulitis
    • inflamed diverticula; may rupture and leak into peritoneal cavity
    • could be life threatening
  113. irritable bowl syndrome
    • functional GI disorder
    • recurring abdominal pain, stool changes, bloating, flatulence, nausea, depression
    • stress common precipitating factor
  114. defecation
    • mass movements force feces toward rectum
    • distension initiates spinal defecation reflex
    • parasympathetic signals stimualte contraction of sigmoid colon and rectum, relax internal sphincter
    • conscious control allows relaxation of external anal sphincter
  115. chemical digestion
    • digestion: catabolic macromolecules>monomers small enough for absorption
    • enzymes: intrinsic and accessory gland enzymes break down food
    • hydrolysis: water is added to break bonds
  116. digestion of proteins
    • source is dietary, digestive enzymes, mucosal cells; digested to amino acid monomers
    • begins with pepsin in stomach¬†
    • pancreatic proteases: trypsin, chymotrypsin, carboxypeptidase
    • brush border enzymes: aminopeptidases, carboxypeptidases, and dipeptidases
  117. digestion of lipids
    • pretreatment: emulsification by bile salts
    • enzymes : pancreatic lipases
    • absorption of glycerol and short chain fatty acids: absorbed into the capillary blood in villi, transported via the hepatic portal vein
  118. absorption of protein
    • amino acids transported by severl types of carriers
    • dipeptides and tripeptides actively absorbed by H+ dependent cotransport; digested to amino acids within epithelial cells
    • enter capillary blood by diffusion
  119. absorption of nucleic acids
    active transport across epithelium to bloodstream
  120. absorption of vitamins in small intestines
    • fat soluable vitamins ADEK diffused into absorptive cells
    • water soluble vitamins C B absorbed by diffusion or by passive or active transporters
    • vitamin B12 binds with intrinsic factor and is absorbed by endocytosis
  121. absorption of vitamins in large intestine
    K B vitamins from bacterial metabolism are absorbed
  122. absorption of electrolytes
    • most ions actively along length of small intestine
    • iron and calcium are absorbed in duodenum
    • Na coupled with active absorption of glucose and amino acids
    • Cl transported actively
    • K diffuses in response to osmotic gradients; lost if poor water absorption
    • usually amount in intestine is amount absorbed
  123. absorption of water
    9 liters water, most from GI tract secretions, enter small intestine. 95% absorbed in the small intestine by osmosis, most of rest absorbed in large intestine