HTHS Mod 18

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  1. digestive system
    • the body's mechanism for
    • processing and absorbing nutrients; breakdown of food into molecules small enough to enter cells
  2. What all is included in digestive system
    • GI tract & Associated organs:
    • teeth
    • tongue
    • salivary glands
    • liver
    • gallbladder
    • pancreas
  3. Digestive system functions
    • Ingestion - take in food
    • Secretion - release substances that will help the breakdown & absorption of nutrients
    • Mixing and propulsion - ensuring chemicals & food are mixed to promote breakdown, keeping things moving along
    • Digestion - breaking down of foods
    • Absorption - transferring nutrients from GI tract to bloodstream
    • Defecation - removing waste from body
    • **"I Said Make Pizza; Don't Ask Dad"
  4. Another name for the GI tract
    Alimentary tract
  5. Layers of GI tract
    • Four layers: (deep to superficial)
    • mucosa
    • submucosa
    • muscularis
    • serosa
    • basically the same throughout
    • Always a lumen (open in center, duh)Outside covered in serous membrane
  6. mucosa
    • deepest layer of GI tract; lines the lumen
    • Has 3 sublayers: (order from lumen out...)
    • epithelium
    • lamina propria
    • muscularis mucosae
  7. epithelium in mucosa
    • TWO TYPES:
    • Oral cavity and esophagus have stratified squamous epithelium (think of tortilla chips)

    Stomach and intestines have simple columnar epithelium
  8. lamina propria
    • intermediate layer of mucosa
    • layer of areolar connective tissue w blood and lymphatic vessels to pick up material absorbed by the epithelium
  9. muscularis mucosae
    • outermost layer of mucosa
    • a thin muscle layer that makes the inside of the GI tract all crinkly and folded
  10. submucosa
    • 2nd layer of the GI tract (from lumen out)
    • comprised of areolar connective tissue
    • contains blood, lymphatic vessels, and submucosal plexus of the enteric nervous system
  11. muscularis
    • 3rd layer of GI tract (from lumen out)
    • IN mouth & pharynx: striated (voluntary) muscle to control swallowing
    • Rest Of GI tract: smooth (involuntary) muscle, usually in 2 layers, keeps materials moving through peristalsis
  12. 2 layers of the muscularis
    • circular muscle and longitudinal muscle
    • help facilitate the movement of food (peristalsis)
  13. muscularis externa
    another name for muscularis; to distinguish it from the thinner, weaker muscle layer of the muscularis mucosae
  14. peristalsis
    • movement of food through GI tract
    • caused by circular and longitudinal muscles in muscularis layer
  15. serosa
    • most superficial layer of the GI tract
    • made up of areolar connective tissue covered by simple squamous epithelium
  16. In the abdominal cavity, what is the serosa layer called
    • visceral peritoneum
    • cause it forms the "guts" side of the peritoneal cavity
    • weakest area: arteries, vessels, lymph & nerves entering GI tract
  17. components of the oral cavity
    • teeth
    • tongue
    • uvula
    • pharynx
    • hard palate - posterior to upper incisors
    • soft palate - posterior to hard palate
    • palatine tonsils
  18. borders of oral cavity
    • Superior border: hard & soft palates
    • Lateral border: buccal surface (cheeks) - side of teeth facing the cheek
    • Inferior border: lingual surface (tongue)
  19. how is oral cavity divided
    • 4 quadrants:
    • R & L maxillary quadrant (division down midline - duh)

    R & L mandibular quadrant
  20. buccal
    directional term: surface of tooth toward cheek
  21. lingual
    directional term: surface of tooth toward the tongue
  22. occlusal
    directional term:for teeth, towards the surface where they meet other teeth (regarding chewing)
  23. mesial
    directional term: refers to individual tooth - surface closest to midline (forward)
  24. Distal
    directional term: refers to individual tooth - surface furthest away, or most posterior, from midline
  25. Four shapes of teeth that are used as part of full names of teeth
    • incisors - sharp, cutting teeth
    • cuspid (canine) teeth
    • premolars - bicuspids (same thing)
    • molars -very back
  26. # of each type of tooth
    • In each quadrant:
    • Molars: 3
    • Premolars (bicuspid's): 2
    • cuspid: 1
    • Incisors: 2
  27. numbering of teeth
    • 32 teeth in human mouth: 8 upper right, 8 upper left, 8 lower right, 8 lower left
    • # starts w most distal maxillary molar on pt's right side, travels around upper jaw to most distal maxillary molar on pt's left side (#16).
    • Then drops down to the mandibular set @ the most distal right, rotating around to left
  28. Naming of teeth
    • STARTING AT TOOTH #1: (in pt's upper right quadrant, most distal toot)
    • 3rd molar (or wisdom tooth)
    • 2nd molar (12 yr molar)
    • 1st molar (6 yr molar)
    • 2nd bicuspid (2nd premolar)
    • 1st bicuspid (1st premolar)
    • cuspid (canine)
    • lateral incisor
    • central incisor 
    • central incisor... etc
  29. deciduous teeth
    • "baby teeth" - Children have only 20
    • typically teeth start to erupt about 6 months
    • Designating by letters (A-T), following same pattern as # teeth 
    • Starts w 2nd molar (A), 1st molar (B), NO PREMOLAR, Canine (C), Lateral incisor (D), and Central incisor (E)
  30. Crown
    visible part of the tooth above the gum line
  31. neck
    • inferior to crown
    • the part of the tooth just below the gumline
  32. root
    the part that attaches the tooth to the periodontal ligaments and then to the jaw bone (maxilla or mandible)
  33. enamel
    • outer part of tooth, forming the occlusal surface & contacts btwn teeth
    • stops in neck
    • made up of minerals calcium phosphate and calcium carbonate
    • harder than bone, cause almost all mineral w little organic matrix
  34. dentin
    • found below the enamel & cementum
    • forms the bulk of the tooth
    • surrounds entire pulp chamber & root canal to apical foramen
    • also harder than bone, but not as hard as enamel
    • contains dentinal tubules
  35. dentinal tubules
    • Have fluid within
    • normally, the enamel covers dentin and keeps fluid from moving.
    • When dentin is exposed, fluid can move (as if dentinal tubules are tiny drinking straws) & the nerves of the root send pain signals to brain
  36. cementum
    • kinda like a continuum of the enamel..
    • covers the dentin of the root
    • also acts as attachement for periodontal ligament
  37. periodontal ligaments
    • dense fibrous connective tissue
    • connects the root to the jawbone
    • have proprioception (pressure receptive nerves) that are resistant to anesthesia
    • This is why we can feel pressure w dental work even when pain fibers are quiet
  38. pulp cavity
    • a chamber formed by dentin w 1 to 3 outlets (for teeth roots)
    • encloses pain fibers and blood vessels
  39. apical foramina
    • outlets in the dentin for each tooth root
    • # varies depending on which tooth ( how many roots it has - 1 to 3)
    • allows blood supply and nerves into tooth
  40. What CN carries the pain signals of the nerve fibers found in the pulp cavity
    • CNV - trigeminal nerve
    • **You would NOT give that nerve a "high 5"
  41. tongue
    • a skeletal muscle that's covered w mucous membrane
    • also has function as taste organ
  42. filiform papillae
    • look like little threads, covers most of tongue surface
    • are non-taste structures that give the tongue a rough texture
    • "fills" in everywhere
  43. taste buds
    • clusters of gustatory receptor cells along w supporting cells (which are clustered in each taste bud)
    • Individual taste buds scattered over the surface of the oral cavity - on tongue, but also on lips, palate, and oropharynx
    • found in 3 groupings
  44. 3 types of gustatory receptor cells
    • "taste buds"
    • Fungiform papillae
    • Foliate papillae
    • Vallate (circumvallate) papillae
    • **Think of a tree. The Fungiform papillae is like the soil & trunk of the tree (@ front part of tongue) The Vallate can be thought of as branches (make V shape on tongue). The Foliate papillae are leaf shaped (foliate ~ foliage) perfect for the leaves at back of tongue
  45. fungiform papillae
    • type of tastebud
    • look like little mushrooms
    • on anterior section
  46. foliate papillae
    • type of taste bud
    • are leaf-shaped papillae found along the lateral surface of the posterior tongue
  47. Circumvallate papillae
    • also called vallate - latin for "surrounded by a wall"
    • form a V-shaped row along posterior tongue
    • usually 7 - 12 of these
  48. lingual glands
    • a set of glands on the tongue
    • secretes mucus plus lingual lipase
  49. lingual lipase
    • an enzyme that's secreted w mucus from lingual glands
    • helps break down fatty food in mouth
  50. saliva
    • secreted by specialized glands in the face (salivary glands)
    • 95% water, rest is mucus and enzymes
    • Plays important accessory role in digestion: ensuring food is pre-digested and soft before swallowed
    • also defends GI tract from microbial invaders
  51. What does saliva do?
    • Moistens: food + saliva = bolus
    • Softens
    • Lubricates oral cavity & food
    • Initiates digestion
    • Facilitates taste
    • Cleanses oral cavity and teeth
    • Bactericidal - protects GI tract
  52. 3 major salivary glands: locations & ducts
    • Parotid gland: largest gland, inferior & anterior to ears, parotid duct
    • Sublingual gland: beneath tongue, lesser sublingual ducts
    • Submandibular gland: floor of mouth, medial and inferior to mandible, submandibular ducts
    • *duct names copy gland name - except sublingual gland = lesser sublingual ducts
  53. 4 minor salivary glands
    labial, buccal, palatal, lingual
  54. acini
    • cell grouping in salivary glands
    • 2 types: 
    • mucous acini - makes mucus
    • serous acini - makes enzymes in watery fluid
  55. Enzymes in saliva:
    • Lysozyme: breaks down invading microbes = defense
    • IgA: (immunoglobulin) = defense
    • Salivary amylase: begins the breakdown of starchy foods into sugars (which is why starchy foods taste sweet, even if they have low sugar. This enzyme releases that sugar)
  56. Differences in secretion btwn the 3 main salivary glands
    • From watery to mucus-y = 
    • Parotid gland: has more serous acini=water + enzymes
    • Submandibular gland: has both serous and mucous acini= water+mucus+enzymes
    • Sublingual gland: mostly mucous acini= mucus w few enzymes
  57. deglutition
    • swallowing
    • Goal: move food from oral cavity to stomach
    • the beginning of bowel motility
  58. dysphasia
    • difficultly swallowing
    • issue btwn oral cavity and stomach
    • Associated w neurological disorders - pts encouraged to eat more gelatin-like food to allow epiglottis time to block trachea
  59. esophagus
    • muscular tube located in mediastinum of thorax; moves food from pharynx to stomach
    • Where we first encounter the general structure of the gut tube (recall 4 layers)
    • Doesn't have absorptive surface
    • 2 layers in muscularis
    • made of nonkeratinized stratified squamous epithelium
  60. 2 layers in muscularis of esophagus
    • circular layer: closes off the lumen when contracted
    • longitudinal layer: contracts in waves (peristalsis) to move things along
  61. Esophageal sphincters
    • Upper esophageal sphincter btwn pharynx and esophagus
    • Lower esophageal sphincter btwn esophagus and stomach
  62. esophagus control of deglutition
    • Voluntary: upper esophageal sphincter and superior 1/3 is striated muscle
    • Involuntary: lower 2/3 of esophagus and lower esophageal sphincter is smooth muscle
  63. epiglottis
    • an elastic flap that:
    • covers the esophagus when breathing
    • covers trachea when swallowing
    • made of nonkeratinized stratified squamous epithelium
  64. peristalsis
    the process that moves the bolus, later chyme, then feces, in the GI tract
  65. bolus
    "clod" of food
  66. 3 stages of swallowing
    • voluntary - controlled consciously
    • pharyngeal - involuntary
    • esophageal - involuntary
  67. pharyngeal stage of deglutition
    • bolus of food is in the oro- and laryngopharynx
    • food and water are kept out of the trachea:
    • soft palate & uvula move upward to close nasopharynx
    • epiglottis closes trachea keeping food out of airway
    • After which the receptors in the medulla/pons trigger deglutition; larynx moves superiorly in order to contact epiglottis (which moved inferior, closes trachea)
  68. esophageal stage of deglutition
    • the upper esophageal sphincter opens
    • peristalsis moves bolus through esophagus, through lower sphincter
  69. cardiac sphincter
    • another name for lower esophageal sphincter
    • the sphincter food and liquid pass through when they leave the esophagus and enter the stomach
  70. 5 regions of the stomach + 2 curves
    • Regions:
    • Cardia
    • fundus
    • body
    • pyloric antrum
    • pyloric canal
    • Curves:
    • greater and lesser curvature
  71. cardia
    the point at which the esophagus crosses the diaphragm to become the stomach
  72. fundus
    the top/superior part of the stomach
  73. largest portion, or region, of stomach
    the "body"
  74. pylorus
    • the narrowing part of the stomach nearest the small intestine
    • The pyloric antrum transitions to the pyloric canal
  75. pyloric sphincter
    • at end of pyloric canal
    • represents the end of the stomach contents
    • opens into duodenum
  76. GERD
    • Gastroesophageal Reflux
    • happens when the lower esophageal sphincter fails to tightly close
    • can be caused by increased abdominal pressure, as in obesity
  77. duodenum
    the initial segment of the small intestine
  78. histology of stomach
    • like of part of GI tract, stomach follow basic plan
    • the mucosa layer is specialized for digestion = gastic pits
    • Lumen is predominated by epithelial cells & surface mucous cells
  79. gastric pits
    • specialized depressions in the stomach, lined w simple columnar epithelium
    • gastric glands
  80. gastric glands
    • collective term for glandular (secretory)cells
    • higher in concentration in the bottom half of gastric pit
  81. surface mucous cells
    • cells which make & secrete mucus in the stomach (duh)
    • is an essential part of stomach lining
    • protects the cells on the surface from being damaged by acid and enzymes secreted by the stomach
  82. abluminal
    the luminal surface in the stomach
  83. Cells of the gastric gland
    • in the mucosa layer:
    • Mucous neck cells
    • Parietal cells
    • Chief Cells
    • G cells
  84. mucous neck cells
    • -In the "neck" of the gastric gland (mucous layer of stomach)
    • secrete protective mucus
  85. parietal cells
    • -of the gastric gland (mucous layer of stomach)
    • 2 essential roles:
    • They have specialized protein pumps that dump H+ and Cl- ions into the lumen, making HCL- stomach acid
    • They secrete intrinsic factor
  86. intrinsic factor
    • secreted by the parietal cells (in the gastric gland -mucosa layer of stomach)
    • a glycoprotein that helps cells of intestinal ileum absorb of Vit B12 from the diet
    • *B12 is needed for erythropoiesis
  87. pernicious anemia
    • results from decreased production of intrinsic factor
    • is abnormal red blood cells
    • (too large & low in #)
    • can also result from folic acid deficiency
    • *issue isn't that they don't have Vit B12, it's that they don't have the intrinsic factor, which doesn't allow them to absorb the vitamin through the intrinsic factor receptors in the jejunum
  88. chief cells
    • -of the gastric gland (mucosa layer)
    • secrete the enzymes pepsinogen and lipase:
    • HCl converts Pepsinogen to pepsin to break down proteins
    • Lipase breaks down triglycerides (fats & oils)
  89. G cells
    • example of enteroendocrine cells
    • secrete the hormone gastrin which promotes the secretion of gastric juices
  90. enteroendocrine cells
    a kind of hormonal system in the GI tract
  91. muscularis layer of the stomach
    • thick muscle layer, but unique:
    • has an "extra" layer → oblique muscle layer
  92. oblique muscle layer
    • an "extra" layer of muscle in the thick muscularis
    • fibers run diagonally
    • aids in stomach's ability to "churn" substances and speed digestion
  93. Explain how stomach acid is secreted
    • Secreted by parietal cells
    • HCl aids in digestion & protects from invaders
    • Hand Cl- are both released by the parietal cell, and bond to make stomach acid
  94. How is the H+ ion formed to be expelled from the parietal cell of the stomach
    • Water + CO2 enter the parietal cell
    • With the help of the enzyme carbonic anhydrase, the bond and form carbonic acid (H2CO3)
    • Because it's an acid, it dissociates into a H+ and a bicarbonate ion ( HCO3-)
    • The H+ is then pumped out of the parietal cell by an active transport pump using ATP. So H+ is traded (pumped out) for a K+ (pumped in)
    • H+ can now bond to Cl & make stomach acid
  95. carbonic anhydrase
    • found within parietal cells
    • the enzyme that turns carbon dioxide and water in the stomach into carbonic acid (H2CO3)
  96. How is the Cl- ion formed & expelled from the parietal cell of the stomach?
    • Recall the process which made the Hion + bicarbonate ion 
    • An antiporter allows the remaining bicarbonate ion (HCO3-) to by dumped into bloodstream (recall it carries RBC)
    • BUT when the HCO3- leaves parietal cell, Cl- is brought into the parietal cell (from interstitial fluid).
    • Since Cl- is at lower concentration OUTSIDE cell, Cl- flows down concentration gradient, exists parietal cell and bonds with the H+ (that also left the parietal cell)
  97. What can cause the stomach to ulcerate
    Disease causing an increase in secretion of stomach acid, or more commonly decrease the secretion of protective materials (such as mucus from surface mucous cells and mucous neck cells)
  98. gastric ulcers
    • results from the disruption of the secretion of protective mucus
    • The bacteria Helicobacter pylori will cause a disruption in the secretion of mucus
  99. duodenal ulcers
    results from failure of the pancreas to make bicarbonate
  100. Types of regulation of HCl release
    • (stomach acid)
    • Several neurotransmitters/hormones upregulate HCl secretion (promote secretion):
    • Acetylcholine released from parasympathetic stimulation of Vagus nerve CN10
    • Gastrin (a hormone) from G cells of stomach
    • Histamine from mast cells in the lamina propria (via H2 receptors)
    • *mast cells are activated by any inflammatory process. So chronic inflammation may lead to gastric ulcers
  101. cimetidine
    • Trade name is Tagamet
    • A medication used for ulcer relief which acts to block the H2 subtype of histamine receptors, thereby decreasing acid secretion
  102. PPI's
    • Proton-Pump inhibitors - a class of drugs used to reduce the secretion of H+Cl- in parietal cells by inhibiting the proton pump (H+/K+ATPase)
    • can also reduce symptoms of GERD (Gastroesophageal reflux disease)
    • Examples: 
    • Omeprazole (prilosec)
    • Lansoprazole (prevacid)
    • Esomeprazole (nexium)
  103. 3 regions of the small intestine
    • From stomach to large intestine:
    • duodenum
    • jejunum
    • ileum
  104. Folds in small intestine
    • recall that we need alot of surface space for absorption without taking up alot of volume. 
    • Solution is "folds" 
    • So there are 3 sizes:
    • BIG macroscopic folds
    • MEDIUM microscopic folds
    • SMALL microscopic folds
  105. plicae circularis
    • "circular folds" w/in mucosa layer
    • lines the lumen, making it wrinkly
    • creates more surface area for absorption
    • THESE ARE THE "BIG" FOLDS, able to see with naked eye
  106. villi
    • "shaggy" finger-like projections on the luminal (mucosa) surface of the small intestine
    • Covered by simple columnar epithelium cells, "specialized" for absorption 
    • Within the villi is lamina propria, which contains lacteals and circulatory vessels
    • A single extension is called a villus, many together are called villi
  107. Describe the specialized epithelium that covers the villi in the mucosa layer of the small intestine
    • Is specialized simple columnar epithelium, which covers the villi
    • The shape of the epithelial cells allows them to absorb water and nutrients on luminal surface, process the nutrients necessary, and drop those substances into capillary bed in lamina propria
    • *the epithelial cells are layered with microvilli
  108. microvilli
    • are a smaller version of villi
    • cover the villi's epithelial cells, giving it a velvety look
    • *because it has the velvety look, or like brush bristles, is referred to as the "brush border"
    • again, increases surface area
  109. lacteal
    • a small lymph vessel in the lamina propria of the villi in small intestine
    • carries lipids (within chylomicrons) sent from the absorptive epithelium
    • eventually drain into thoracic duct and releases lipids into bloodstream at Left jugular/subclavian junction
  110. myenteric plexi
    • lies btwn the circular and longitudinal layers of the muscularis
    • clusters of neurons that control the autonomic movements of the intestines (they generate peristaltic waves)
  111. Specialized cells that line the villi
    • Goblet cells
    • Paneth cells
    • Enteroendocrine cells
  112. Paneth cells
    • enzyme-secreting cell of villus in the small intestine
    • secrete lysozyme
    • also capable of phagocytosis
    • protection = can think of the enzymes as antibacterial
    • **Think Panther... crouches n stocks it's pray (its near bottom n btwn villi)
  113. enteroendocrine cells
    • line the villus in the small intestine
    • secrete various hormones to either speed up or slow down the digestive process:
    • secretin from S cells
    • CCK (cholecystokinin) from CCK cells
    • GIP (glucose-dependent insulinotropic peptide) from K cells
  114. 3 main classes of ingredients (in food)
    • Carbohydrates: including monosaccharides (simple sugars), disaccharides (ex: sucrose) and polysaccharides (starches)
    • Fats/Lipids
    • Proteins: polymers of amino acids
    • **Each substance has a different route from gut lumen to bloodstream
  115. What's the basic path of an absorbed molecule in the intestinal tract
    • From lumen, passes through the cell membrane of an absorptive cell
    • From absorptive cell, it diffuses to the blood capillary of a villus, and enters bloodstream
  116. Recall facilitated diffusion
    • Recall only water and gases move by simple diffusion across cell (no assistance)
    • Larger &  charged molecules have to be "escorted"; even if concentration is higher outside than inside
    • Facilitated diffusion simply involves protein channels or carriers (in membrane) to facilitate the diffusion of substances
    • Don't think it uses energy, it uses the concentration gradient
    • the protein just changes shape once it's molecule comes inside, to spit it where it needs to go
  117. Recall the symport system
    • Is a type of secondary active transport (meaning it requires energy to work)
    • A molecule and an ion move in the same direction to drive the pump. 
    • In example with Na+ and glucose (for intestinal cells), the Na+ would move down it's concentration gradient into the cell, and drag glucose w it.
  118. Where does the energy come from for the symport system
    • Doesn't use ATP - uses concentration
    • *The energy used is best explained this way: Think of a damn. On one side is a large body of water. Therefore, a large amount of stored energy. 
    • Since the sodium is highest in concentration outside the cell, it can be compared to the large body of water that's been damned up.
  119. Explain the difference in the movement of glucose btwn body cells and intestinal cells
    • For almost all cells (where we also use insulin), glucose moves across the cell membrane via facilitated diffusion. (it has it's own transporter protein in membrane) It works by glucose concentration being low inside the cell, and high outside. 
    • FOR INTESTINAL CELLS concentrations are switch and works by the symport system. They concentrate glucose in their cytoplasm before dumping it into the bloodstream
  120. What molecule, besides glucose, in the intestinal cells is transported via the symport system
    amino acids
  121. amylases
    • enzyme secreted by pancreas which breaks down starches into monosaccharides
    • *Disaccharides are broken into 2 monosaccharides
    • *Also found in salivary secretions
  122. sucrase
    • an enzyme found in the brush border of small intestine
    • breaks sucrose (a disaccharide) into glucose and fructose (monosaccarides)
  123. Explain the absorption of sugars into INTESTINAL CELLS from the lumen
    • Only monosaccharides absorbed are glucose, galactose, and fructose
    • Glucose and galactose are at higher concentrations INSIDE intestinal cell than in lumen ⇉ carried into cell via symport system
    • Fructose is always in higher concentration in lumen then inside cell ⇉ enters intestinal cell via facilitated diffusion
  124. Explain how sugars go from intestinal cells into BLOODSTREAM
    • Once inside the cell, sugars (glucose, galactose and fructose) diffuse via their concentration gradient:
    • From areas of higher concentration (inside absorptive cells of intestine) to lower concentration (bloodstream) by facilitated diffusion
  125. Describe how proteins are absorbed into INTESTINAL cells
    • By active transport (symport system)
    • Proteins are polymers of amino acids. Therefore, enzymes break the proteins into fragments of 1, 2 or 3 amino acids in length.
    • Amino acids (1 molecules) are pumped into absorption cell via Na+ driven symport (just like glucose)
    • Di- and tripeptides (2 & 3 amino acids) are brought in using a similar H+ driven symport
  126. How do amino acids, di & tripeptides get to bloodstream from intestinal cell
    via simple diffusion (w/o aid)
  127. What molecules can pass cell membrane w/o help
    anything small, neutrally charged, lipid-soluble
  128. Explain absorption of lipids (fats)
    • No problem getting into absorptive cell (small, neutral charge, and lipid-soluble)
    • Small-chain fatty acids are small enuf to move across the intestinal cell membrane & into the bloodstream by simple diffusion
    • BUT the other lipids form micelles in the gut lumen and are too large and too water-insoluble to move as easy as small-chain fatty acids
  129. micelles
    • In a water-based solution, the particles resulting from emulsified lipid
    • consist of long-chain fatty acids and monoglycerides
  130. Explain how the larger lipids get absorbed
    • Recall the larger lipids are too big and too water-insoluble- AND they are micelles in the lumen
    • Via simple diffusion, they (micelles) enter the intestinal cell
    • The cell then breaks down the micelles and form triglycerides
    • The triglycerides are then packed into chylomicrons~ (since fats don't want to be in the bloodstream cause their hydrophobic) & pushed out basolateral surface to be dumped into the lacteal
  131. chylomicrons
    • "packages" or "suitcases" of triglycerides within the intestinal cell 
    • are pushed out the basolateral surface of the absorptive cell and into the lacteal (small lymph vessel) within the villus
    • Carried into blood stream via lacteals, where lipids can associate w lipoproteins (HDL - high density lipoproteins, or LDL, or VLDL - very low...)
  132. recall lipoproteins
    • lipid-carrying proteins of the bloodstream
    • synthesized by the liver
  133. Why does lipids go into the lymphatic lacteals instead of into the bloodstream like everything else.
    • Once the triglycerides are packaged into the chylomicrons (the water-soluble, lipid suitcases), they are too big to get into the capillaries. 
    • Need another way to transport them
    • Lacteals are a bit more permeable and will allow a bigger molecule in
  134. So where does all this "stuff" go that diffuses into the blood capillaries and lacteals of the villi?
    • All the molecules, EXCEPT LIPIDS, enter the hepatic portal circulation (vein)
    • Lipids (as chylomicrons) are in the lymphatic drainage, which drains into the thoracic duct and enters bloodstream via left subclavian vein
  135. vitamins
    • chemical cofactors the work to help speed up essential chemical reactions in cells by lowering the activation energy of chemical reactions
    • 2 major categories: fat-soluble and water-soluble
  136. Vitamins vs enzymes
    • they both help speed up chemical reactions by lowering the activation energy of chemical reactions
    • BUT enzymes are proteins; vitamins are non-protein catalysts
  137. Water-soluble vitamins
    • include vit.'s B, C, niacin, biotin, and folic acid. They are absorbed directly by stomach and intestines (through diet)
    • Vitamin B12, however, is absorbed with the help of intrinsic factor, which is secreted by parietal cells of stomach
    • **Forget deNi-ing Crying Bawl Baby (and you want to drown the bitch)
  138. Explain the intrinsic factor
    • Vit B12 is one of the biggest vitamins. 
    • Has to hook to intrinsic factor, which forms a VitB12/intrinsic factor complex
    • This complex goes down to the jejunum where there are receptors for this complex that help us then absorb the B12
  139. Fat-soluble vitamin
    • means they have to be absorbed with fat
    • Includes A, E, D and K
    • Vit K can by synthesized by bacteria in large intestine (when the diet is low in Vit K)
    • aids in blood clotting
    • **Everyone's Addicted 2 Krispy-cream Donuts
  140. Purpose of large intestine
    • as most substances are absorbed in the small intestine, the final liter of fluids is absorbed here.
    • As it moves, watery substance becomes more solid
    • *the faster something moves through the intestines, the less is absorbed = diarrhea
    • *the longer it takes (the slower the movements of the intestines) the more liquid is absorbed = constipation
  141. Large intestine (regions)
    • begins where the ileum (final portion of small intestine) has an outlet (through ileocecal sphincter) into the cecum
    • It then continues upward as the ascending colon, crosses from right to left as the transverse colon, and drops down the left flank as the descending colon
    • At this point it makes an S-shaped curve called the sigmoid colon
    • There, a straight down segment called the rectum attaches to anal canal, leading to the anus
  142. cecum
    • the "pouch" of the large intestine that receives contents from small intestine, through the ileocecal sphincter
    • Ex of bad design as it tends to catch objects that have passed into large intestine
    • Has an extension = vermiform appendix
  143. vermiform appendix
    • simply the appendix
    • "end" of the cecum ~ a small worm-like hole that often becomes inflamed (appendicitis)
    • *Has been proposed it acts as a reservoir for "friendly" gut bacteria so their colonies can be replaced after antibiotic treatment
  144. peritonitis
    • a medical emergency
    • results from a burst appendix, which dumps the bacteria-laden intestinal contents into the peritoneal cavity
  145. ileocecal sphincter
    the "valve" which allows material to pass from ileum of small intestine to cecum of large intestine
  146. histology of large intestine
    • follows "standard" GI tract pattern 
    • the absorptive surface is limited to absorption of (mostly) water
    • No plicae, no villi - so doesn't have all the folds like small intestine
    • like small intestine, has a velvety appearance ONLY cause the absorptive cells have microvilli on surface
    • there are also openings for intestinal glands
  147. crypts of Lieberkühn
    intestinal glands
  148. cells types of the large intestine
    • only 2 cell types present:
    • goblet cells & water-absorbing absorptive cells
    • *it is the absorptive cells that have microvilli
    • NO enzyme-secreting cells: digestion carried out by bacteria; some B and K made by bacteria
    • NO enteroendocrine cells
    • **Go Asshole
  149. Describe 2 sphincters in anus
    • Internal anal sphincter: involuntary = autonomic motor, smooth muscle
    • External anal sphincter: voluntary= somatic motor, skeletal muscle
  150. elimination
    the removal of wastes from the body by expelling material from the anus
  151. defecation reflex
    • a mixture of autonomic and voluntary motor control
    • triggered by distension (enlargement) of the rectum
    • Activation of stretch receptors in the wall of the rectum lead to internal anal sphincter relaxation (involuntary)
    • This can be overridden (we hope) by the external anal sphincter, which is controlled by the cortex of the brain (voluntary)
  152. Valsalva maneuver
    • increases intra-abdominal and intrathoracic pressure = increases recital pressure
    • The pt tries to exhale against a closed nose and mouth while bearing down (as in a bowel movement or popping ears)
    • Because of increase in pressure, causes characteristic changes in BP and HR

  153. Why would the valsalva maneuver cause changes in BP & HR?
    • Because of increase in pressure, HR says pressure is too high, so heart rate decreases
    • When pt exhales, pressure is released. HR says pressure is too low, so HR speeds up.
    • So characteristic drop and then speeding up of HR
    • Can be used to diagnose heart disease, also correct A-Fib in some cases
  154. Phase I of Valsalva maneuver
    straining produces an increase in systolic arterial pressure (transient)
  155. Phase II of Valsalva maneuver
    • continued straining decreases arterial pressure, increases HR)
    • (tachycardia due to increased sympathetic response of carotid sinus reflex)
  156. Phase III of Valsalva maneuver
    as the strain is released, sudden drop arterial pressure, heart increases to maximum
  157. Phase IV of Valsalva maneuver
    heart rate drops, and bradycardia "overshoots" before a return to normal heart rate and blood pressure
  158. liver
    • tied w brain for "second largest organ"
    • Is a detoxification and energy storage organ
    • produces bile
    • receives blood from digestive organs 
    • divided into four lobes: larger R & smaller L lobes visible from anterior, Caudate & Quadrate lobes only seen when looking from posterior or inferior
  159. How is the liver held in place?
    • three strips of connective tissue (ligaments):
    • falciform ligament (Latin: sickle-shaped) - main one extending down from diaphragm
    • coronary ligament - on posterior side
    • round ligament - on anterior side
    • *The first two (falciform & coronary) attach to diaphragm, which keeps liver in position in superior part of ab cavity n mostly to right side of body
  160. What other neighboring organs work together with the liver?
    the pancreas and duodenum
  161. Explain livers dual blood supply
    • Oxygenated blood from heart via hepatic artery
    • Deoxygenated blood w absorbed nutrients from digestive organs via hepatic portal veins
  162. proper hepatic artery
    • also referred to as hepatic artery
    • supplies the cells of the liver with oxygen
    • Blood from left ventricle of heart ⇉ aorta ⇉ abdominal aorta ⇉ hepatic artery
  163. hepatic portal vein
    • delivers blood to the liver from stomach and intestines to process: detoxify and energy storage
    • This blood is glucose-rich but oxygen poor
  164. hepatic veins
    takes the venous drainage (blood minus toxins plus proteins) of the liver to the inferior vena cava ⇉ on to the right atrium of heart
  165. liver lobule
    • "hepatic lobule"
    • a six-sided (hexagon) 'plate' - histological unit of the liver
    • *was once thought to be the functional unit of the liver until recently
    • Have a hepatic triad on 3 corners (every other point, so evenly spaced around six points)
  166. hepatic (liver) sinusoids
    • basically spaces - or incomplete capillaries
    • gives a high rate of permeability
    • Hepatocytes are located along these "spaces", also where the kupffer cells are
    • *synonymous to the many capillaries we have in other places of body
  167. Describe blood flow through liver
    • Orich blood from hepatic artery and nutrient-rich, deoxygenated blood from hepatic portal vein is dumped into the liver sinusoids
    • Then through the central vein ⇉ hepatic vein ⇉ inferior vena cava ⇉ right atrium of heart
  168. Two main types of cells in liver
    • Hepatocytes
    • Kupffer cells
  169. Hepatocytes
    • One of two main cell types in liver
    • inactivate toxins, produce bile, and also produce a variety of blood proteins
    • Play a role in metabolism of carbs, lipids, and proteins
  170. Kupffer cells
    • just a special name for a type of macrophage found in liver
    • they destroy aged red blood cells and any invaders that reach the liver from intestinal drainage
  171. So describe what exactly happens in each hepatic lobule
    • Starting at the hepatic triad, blood from both hepatic portal vein and hepatic artery flow into the liver sinusoids
    • Hepatocytes take in nutrients and do their job
    • Any waste products from this (which is bile) is sent to the bile duct via bile canaliculi
    • Kupffer cells also found in sinusoids destroy bad guys
    • This all works from outside border to center of lobule, where the central vein is located, which drains into hepatic vein
  172. Which organs work together to activate Vit D from it's precursor forms?
    skin, liver, and kidneys
  173. bile
    • produced by hepatocytes in liver
    • a greenish liquid substance which is stored in the gallbladder (if you have one)
    • When released in the GI tract, helps to emulsify fats so they can be transported across intestinal cell and dumped into lacteal in center of villus
  174. Bile canaliculi
    the tiny vessels that bile (produced & secreted by the hepatocytes ) travel through, then into bile duct
  175. hepatic triad
    • a collective term referring to the branches of bile ducts, hepatic artery, and hepatic portal vein, as they generally run together as three vessels
    • 3 found on each liver lobules (evenly spaced, every other point on 6 sided lobule)
  176. hepatic acinus
    • current thinking points to this as actual functional unit of the liver
    • Consists of two 1/6 slices of the lobule working together
  177. Flow of bile starting from production
    • Bile produced by hepatocytes in liver:
    • Travels via bile canaliculi to:
    • bile duct (as part of portal triad) in liver
    • *The bile ducts on right side then enter right hepatic duct; bile ducts from left side enter left hepatic duct 
    • These feed into the common hepatic duct;
    • branching from that is the cystic duct, which leads to gallbladder
  178. How is bile released from gallbladder
    • When GI tract signals presence of fats in meal, autonomic muscle of gallbladder squeezes gallbladder, releasing stored bile
    • Bile flows back down cystic duct , which is joined by the common hepatic duct, forming the common bile duct 
    • That flows into hepatopancreatic ampulla
    • This mixture is then released into the duodenum
  179. hepatopancreatic ampulla
    a mixing chamber where common bile duct joins pancreatic duct
  180. sphincter of the hepatopancreatic ampulla
    • the "valve" btwn the hepatopancreatic ampulla and duodenum
    • Old name was sphincter of Oddi
  181. biliverdin
    What the iron molecule is called after it is ripped from heme molecule (from RBC recycling)
  182. Explain how heme is made into bilirubin
    • Recall heme is an oxygen carrier in hemoglobin
    • As RBC only live about 120 days, heme is constantly broken down.
    • The spleen uses an enzyme to convert heme to biliverdin, which then spontaneously converts to bilirubin
    • *Bilirubin made this way is referred to as "unconjugated"
  183. heme oxygenase
    the enzyme used by the spleen (and other cells, if needed) to convert heme to biliverdin
  184. What is meant by "unconjugated" bilirubin
    • bilirubin that hasn't made it to the liver yet
    • means it's insoluble in blood
    • it gloms onto the blood protein albumin and is carried to the liver
    • *once it's in the liver, albumin leaves the molecule, it can leave and is now referred to as conjugated bilirubin
  185. glucuronic acid
    • a small molecule
    • what happens to "unconjugated" bilirubin when it gets to the liver
    • In the liver it is conjugated into this, making it water-soluble
    • In this form, it makes up a major portion of bile
  186. What produces can be created from conjugated bilirubin?
    • Urobilinogen
    • Stercobilin
  187. urobilinogen
    • one product which conjugated bilirubin can be converted to
    • in this form, it travels in the blood circulation:
    • A small amount is processed in kidneys, giving urine it's yellow color
    • **urobilinogen - urine
  188. Stercobilin
    • Formed when conjugated bilirubin in bile is released into the intestines
    • has a brown color, which gives feces it's brown color
  189. What happens if bile becomes obstructed
    • It is no longer released in normal quantities through the hepatopancreatic sphincter
    • In this case, little or no conjugated bilirubin is converted to stercobilin - feces w be pale
    • At the same time, urobilinogen accumulated in urine, giving it darker than normal color
  190. In what ways can the liver become incapacitated
    • hepatitis (results from a virus)
    • drug or alcohol abuse
  191. jaundice
    • happens in newborns when the liver switches from making red blood cells to digestive roles; and changeover does not occur smoothly
    • Bilirubin can't be conjugated, & skin n eyes become yellowish
    • yellow color from accumulation of unconjugated bilirubin
  192. Pancreas
    • Can be thought of as 2 organs in one, w 2 functions:
    • Endocrine pancreas - inner part (islets)
    • Exocrine pancreas - digestive (acini); the outer part of the pancreatic structure
  193. Recall difference btwn exocrine and endocrine
    • Exocrine means secreting externally
    • endocrine means secreting internally
    • *in this module, exocrine will refer to the "outside" meaning the lumen of the GI tract
  194. recall pancreatic islets
    • where the cells of the endocrine pancreas live
    • in the middle of the pancreatic structure
  195. Recall cells of the pancreatic islet & their endocrine products
    • Alpha cells - glucagon
    • Beta cells - insulin
    • Delta cells - somatostatin
    • F cells (also called PP cells) - pancreatic polypeptide
    • Epsilon cells - ghrelin
  196. Summarize enzymes secreted by pancreas
    • Amylase (4 starches)
    • Trypsin, chymotrypsin, elastase - for proteins
    • Carboxypeptidase - amino acid at carboxyl end of proteins
  197. Ghrelin
    • product of epsilon cells in pancreas
    • seems to have effect of stimulating appetite:
    • increase in ghrelin increase appetite
    • Mice that are genetically alter to interfere w this system are not only skinny, but live longer
  198. acini
    • -of the pancreas
    • makes up most of the pancreas
    • secrete pancreatic juice which:
    • helps neutralize stomach acid
    • inactivate pepsin released from stomach
    • supply necessary enzymes for digesting food in small intestine
  199. Where is the pancreatic juices released?
    They meet up with the fat-emulsifying bile in the hepatopancreatic ampulla & are released into the duodenum on demand
  200. sodium bicarbonate
    • NaHCO3
    • "baking soda"
    • released from pancreas
    • buffers stomach acid
  201. amylase
    • released from pancreas
    • is a starch-digesting enzyme
  202. What protein-digesting enzymes are in pancreatic juice
    • Trypsin
    • Chymotrypsin
    • Carboxypeptidase
    • elastase
    • break down proteins into amino acids
  203. What enzymes in pancreatic juice break down nucleic acids?
    • nucleic acids = RNA & DNA
    • Ribonuclease and deoxyribonuclease
  204. Three phases of digestion
    • cephalic phase
    • gastric phase
    • intestinal phase
  205. Describe cephalic phase of digestion
    • is the "head" phase
    • stimulus: smell, taste, sight or thought of food
    • Action: brain prepares body for meal
    • Result: CN 7 & 9 stimulate salivation; CN 10 stimulates stomach acid secretion (by releasing acetylcholine on parietal cells, releasing acid)
  206. Describe gastric phase of digestion
    • Stimulus: stomach wall stretches or food causes stomach pH increase
    • Action: gastric motility and secretion of stomach acid is stimulated
    • Result: stomach empties into duodenum as food is digested
    • Hormonally regulated by gastrin secreted from G cells
  207. Describe intestinal phase of digestion
    • Stimulus: Chyme is in duodenum & stretches the walls
    • Action: this activated the enterogastric reflex
    • Result:
    • Stretch receptors in duodenal wall signal medulla
    • Medulla shuts down vagus nerve (inhibiting ACh release from CN X)
    • This decreases gastric motility & closes pyloric sphincter
    • Hormonally regulated by CCK (cholecystokinin) and secretin, both released from duodenum
  208. gastrin: what is it, what makes it, what organ does it act on, and what action
    • a hormone made by G cells of stomach
    • Acts on the stomach
    • Promotes secretion of gastric juices
  209. cholecystokinin: what is it, what makes it, what organ does it act on, and what action
    • hormone made by enteroendocrine cells of small intestine
    • Acts on:
    • gallbladder - ejection of bile
    • pancreas - more pancreatic juice
    • opening of sphincter of hepatopancreatic ampulla
    • Brain: feel full
  210. secretin: what is it, what makes it, what organ does it act on, and what action
    • a hormone made by enteroendocrine cells ("S cells) of duodenum
    • Acts on pancreas
    • Action: more bicarb in pancreatic juice
  211. glucose-dependent insulinotropic peptide- what is it, what makes it, what organ does it act on, and what action
    • GIP - gastric inhibitory polypeptide
    • hormone made by enteroendocrine cells (K cells) of the duodenum
    • Acts on the pancreas
    • Action: increases insulin secretion
  212. histamine: what is it, what makes it, what organ does it act on, and what action
    • hormone made by mast cells of lamina propria
    • Acts on parietal cells of stomach
    • Action: increases acid secretion
  213. somatostatin:  what is it, what makes it, what organ does it act on, and what action
    • hormone made by the hypothalamus
    • Acts on: many digestive organs
    • Action:
    • decreases exocrine pancreas & many hormones
    • slows gastric emptying
  214. motilin: what is it, what makes it, what organ does it act on, and what action
    • hormone made by enteroendocrine cells (M cells) of duodenum & jejunum
    • Action: increases migrating myoelectric complex
    • increases pepsin
    • increases bowel motility
  215. Peristalsis
    • a "traveling wave" of contraction in the gut
    • similar to a milking action, which a ring of gut squeezing while an adjacent ring relaxes.
    • This forces the material from contracted into relaxed portion of gut
    • By coordinating peristalsis, the GI tract keeps things moving
  216. mass movement
    the process by which the GI tract keeps things moving from mouth to anus via peristaltic action
  217. segmentation
    the alternating contraction and relaxation involved in peristalsis
  218. How is peristalsis controlled?
    • by rhythmic circuits in the enteric nervous system (autonomic nervous system of GI tract)
    • Has a myenteric plexus and submucosal plexus; both receive sensory info from GI tract
  219. myenteric plexus
    • part of the enteric nervous system
    • controls the motor neurons innervating the longitudinal and circular muscle layers of the muscularis
    • Also sends axons to submucosal plexus
  220. submucosal plexus
    • part of the enteric nervous system
    • where motor neurons innervate the small, weak muscles that give the mucosal epithelium it's wrinkles
  221. migrating myoelectric complex
    • refers to the waves of electrical activity in the GI tract that appear to move forward (through tract)
    • Observed by the electrical activity along the length of the bowel wall during peristalsis
  222. What is the total daily input of water in the GI tract & what is it divided between
    • Ingestion (water and food) = 2.3 L
    • Secretions = 6.0 L
    • Total daily input = 9.3 L
  223. Of the 9.3 L of water in GI tract, where (and in what amounts) is it absorbed
    • The small intestine absorbs most, at 8.3 L
    • Thus, 1 L per day passes ileocecal valve
    • The large intestine absorbs 0.9 liters, making the feces solid
    • The remaining 100 ml is used to keep feces moist in able to be passed easily
  224. diarrhea
    • results if the intestines fail to absorb water
    • more liquid than normal is excreted, along with relatively small amounts of feces
  225. constipation
    • results if the intestines absorb too much water
    • making stools hard and difficult to pass
  226. Explain use of laxatives
    • They act by increasing GI motility
    • Increased motility means faster transit time from mouth to anus and therefore less absorption of water and nutrients
  227. What 3 factors can increase bowel motility
    • *in extreme cases pushing the balance of the GI tract toward diarrhea
    • Chyme volume
    • Chemical composition
    • Osmolarity
  228. How does chyme volume effect bowel motility
    an increase in chyme volume increases motility
  229. How does chemical composition of food effect bowel motility
    Chemicals that increase electrical activity, for example by activating sensory nerves of the GI epithelium, increase motility
  230. How does osmolarity effect bowel motility
    • If non-absorbable chemicals (such as those found in sugar-free candies or some laxatives) are higher than 300 mOsm/kg (blood tonicity), water is "drawn" into the lumen
    • thus, increasing bowel motility
  231. Name the categories of digestion:
    • Mechanical digestion (mixing and tearing forces)  Begins in the mouth by chewing our food. All along GI tract, peristalsis aid in mechanical digestion
    • Chemical digestion - chemicals and enzymes action of food. Also begins by putting food in mouth.
    • *Each digestive organ participates in both types of digestion
  232. Describe how each digestive organ aids in process of mechanical digestion
    • Oral cavity: chews food; tongue, checks move food, swallowing mixes food
    • Esophagus: peristalsis mixes food
    • Stomach: contractions of stomach and rugae help in mixing food
    • Small intestine: Plicae circulares and peristalsis mixes food
    • Large intestine: Haustra and peristalsis mix food
  233. Describe how each digestive organ aids in the process of chemical digestion:
    • Oral cavity: salivary glands secrete enzymes to break down starches n fats
    • Esophagus: None
    • Stomach: HCl breaks down food, Pepsin breaks down proteins, Gastric lipase breaks down fats
    • Small intestine: Pancreas secrets Bicarb to neutralize acid + enzymes to break food; bile salts emulsify fats; + wide variety of enzymes
    • Large intestine: beneficial bacteria make Vit K, digest cellulose (fiber), make methane
  234. brush border
    • region of small intestine which contain enzymes
    • Called such because under a microscope it appears "bushy". This is from proteins (enzymes) which coat the microvilli, giving the fuzzy appearance
  235. Enzymes found in brush border
    • Maltase, sucrase, lactase - maltose, sucrose, lactose
    • Amino peptidase - amino acid at amino end of proteins
    • Nucleosidases and phosphatases - for nucleotides
  236. Recall solution
    • mixture where to components (liquid and solid; or liquid and liquid) disperse into individual molecules
    • Recall solvent is the one that predominates; the lesser constituent is the solute (it solutes and obeys the solvent, who's solving problems)
  237. Recall colloid
    • a solution with large solid particles, large enuf to reflect light
    • Particles stay dispersed over time
    • *think of negative ions in a glass, continually repelling each other, always moving.
  238. Recall suspension
    Similar to colloid, by has even larger particals which will settle to bottom of container given time - like muddy water
  239. emulsion
    • a colloid where all components are liquid
    • particles not visible to naked eye
    • Ex: milk is an emulsion and solution: large proteins and fat droplets are in a liquid colloidal suspension (emulsion); sugars are dissoved in solution
  240. chyme
    • an emulsion
    • the mixture of nutrients and GI secretions
Card Set
HTHS Mod 18
Digestive system
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