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GI Tract Flashcards

1
Q

describe filliform papillae

A
  • small and conical
  • most numerous
    • entire dorsal surface
  • involved in mechanical function
    • highly keratinized stratified squamous epi.
    • no taste buds
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2
Q
A

filliform papillae

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3
Q
A

filliform papillae

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4
Q

describe fungiform papillae

A
  • mushroom shaped
  • prominent on tip of tongue
  • stratified squamous epithelium (usually non-keratinized)
  • taste buds in the epithelium on dorsal surface
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5
Q
A

fungiform papillae

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6
Q
A

arrows = fungiform papillae

in between arrows = filliform papillae

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7
Q

describe foliate papillae

A
  • found on the lateral edges of tongue
  • parallel rows separated by deep clefts
  • taste buds
  • rudimentary in humans
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8
Q
A
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9
Q

describe circumvallate papillae

A
  • large and dome shaped
  • located anterior to sulcus terminalis
    • only 8-12
  • surrounded by a moat-like invagination
    • receives ducts of Von Ebner’s glands
      • serous secretion
  • many taste buds in epi. of lateral surface
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10
Q
A
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11
Q

describe taste buds and the types of cells

A
  • extend through entire thickness of epi.
  • taste pore
  • 3 types of cells:
    • neuroepithelial cells
      • sensory cells
      • microvilli on apical surface
      • turnover ~10 days
    • supporting cells
      • microvilli on apical surface
      • turnover ~10 days
    • basal cells
      • stem cells
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12
Q

name the 3 distinct layers of mucosa

A
  1. epithelium
  2. lamina propria
    • loose CT, blood & lymph vessels, mucosal glands, gut-associated lymphatic tissue (GALT)
  3. muscularis mucosa
    • variable, usually 2 layers
      • inner circular
      • outer longitudinal
    • contraction produces movement of the mucosa
    • boundary between mucosa and submucosa
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13
Q

describe the function of the mucosa

A
  • protection: separates the external lumen from tissues and organs of the body
  • absorption: movement of the digested nutrients, water and electrolytes into blood and lymph vessels
  • secretion: carried out mainly by glands throughout the tube which secrete mucus, digestive enzymes, hormones and antibodies
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14
Q

describe the submucosa

A
  • dense irregular CT
  • large blood vessels and lymphatic vessels
  • some areas contain submucosal glands
    • esophagus and duodenum
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15
Q

describe the submucosal plexus (Meissner’s plexus)

A
  • part of enteric nervous system
  • cell bodies of postganglionic PS neurons
  • innervate muscularis mucosa
  • derived from neural crest cells
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16
Q

describe the muscularis externa

A
  • two concentric layers of smooth muscle
    1. inner circular
      • contracts, compresses and mixes content by constricting the lumen
      • forms sphincters at specific locations
    2. outer longitudinal
      • contractions propels content of lumen by shortening the tube
      • in large intestine, thickened to form three bands called teniae coli
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17
Q
A

submucosal plexus

pale-staining PS ganglion cells

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18
Q
A

muscularis externa

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19
Q

describe the myenteric plexus (Auerbach’s plexus)

A
  • located between the circular and longitudinal muscle layers
  • derived from neural crest cells
  • part of enteric nervous system
  • contains postganglionic PS neurons
  • innervates the muscularis externa for peristlatic movement
    • slow rhythmic contraction of muscle layers
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20
Q
A

myenteric/Auerbach’s plexus

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21
Q

describe the serosa layer of the alimentary canal

A
  • serous membrane
    • CT lined by simple sqamous epi.
  • mesothelium
    • small amount of underlying loose CT
  • continuous w/ mesentery and lining of abdominal cavity
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22
Q

describe the adventitia layer of the alimentary canal

A
  • CT not lined by simple squamous epi.
  • attaches structures to the body walls
    • parts of the GI tract that do not possess a complete serosal covering
      • thoracic esophagus
      • 2nd, 3rd, 4th parts of duodenum
      • ascending and descending colon
      • rectum and anal canal
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23
Q

describe the esophagus

A
  • epithelium = stratified squamous non keratinized
  • lamina proopria: CT containing diffuse lymphatic tissue and lymphatic nodules
    • esophageal cardiac glands are present mainly in the terminal part of esophagus
      • produces neutral mucus which protects from regurgitated gastric contents
  • muscularis mucosa: single layer of longitudinal muscle that begins at the level of cricoid cartilage
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24
Q

describe the submucosa of the esophagus

A
  • dense irregular CT
  • esophagel glands proper:
    • scattered throughout the length
    • produces slightly acidic mucous
    • lubricates the lumen
26
Q

describe the esophagogastric junction

A
  • epithelium changes from stratified squamous (esophagus) to simple columnar (stomach)
  • lamina propria: esophageal cardiac glands replaced by cardiac glands of stomach
27
Q
A

esophagogastric junction

28
Q

describe the 3 regions of the stomach

A
  1. cardiac region
    • near esophgeal orifice
    • contain cardiac glands
  2. fundic region (fundus)
    • situated between cardia and pylorus
    • contains fundic (gastric) glands
  3. pyloric region (pylorus)
    • distal, funnel-shaped region proximal to pyloric sphincter
    • contains pyloric glands
29
Q

contrast the cardiac region and the pyloric region

A
  • cardiac region
    • relatively short pits and short glands
    • tubular with occasional branching
    • cells
      • mucus secreting
      • enteroendorcine
  • pyloric region
    • relatively long pits and short glands
    • branched, coiled, tubular with wide lumen
    • mucus cells secrete a viscous mucus
31
Q

describe the fundic region of the stomach

A
  • short pits
    • lined by surface mucus cells
  • long glands
    • simple branched tubular glands
    • 2-4 glands empty into 1 gastric pit
  • cell types:
    • mucus neck cells
    • parietal cells
    • chief cells
    • enteroendocrine cells
    • stem cells
      • found in neck of gland
32
Q

describe the secretions of the fundic gland

A
  • parietal cells
    • hydrocholic acid (HCl)
      • converts inactive pepsinogen into pepsin
    • intrinsic factor
      • glycoprotein that binds to vit. B12
      • lack of intrinsic factor = pernicious anemia
  • chief cells
    • pepsin
      • ​potent proteolytic enzyme
        • hydrolyzes proteins into small peptides
      • converted from pepsinogen
  • mucus
33
Q

contrast surface mucus cells with mucus neck cells

A
  • surface mucus cells
    • secretes thick viscous mucus that adheres to epi. and lines gastric pits
    • elongated nucleus
    • bicarb rich mucus protects epi. from acidity of gastric juice
  • mucus neck cells
    • secretes soluble mucus that helps transport gastric secretion to lumen
35
Q
A
  • chief cells secrete pepsinogen
    • converted to pepsin by low pH
36
Q

describe enteroendocrine cells

A
  • secretes hormones into the lamina propria
  • found throughout the gland
    • more prevalent in the fundus
37
Q

describe peptic ulcers

A
  • H. pylori secretes urease and proteases which:
    • break down mucus
    • creates an alkaline environment which stimulates gastrin -> increase acid/pepsin (cycle)
  • bacterial infxn causes mucosal inflammation, exposing the surface to the effects of pepsin and acid
38
Q

describe the small intestine

A
  • mucosa:
    • simple columnar epi.
    • lamina propria contains GALT
  • submucosa:
    • dense CT
    • submucosal (Meissner’s) plexus
    • plicae circularis (circular folds)
39
Q

describe plicae circulares

A
  • valves of Kerckring
  • permanent transverse folds
  • most numerous in distal duodenum and jejunum
  • reduced in size and freq. in ileum
40
Q

describe villi

A
  • finger-like mucosal projections
  • lamina propria contains central lacteals
    • blind-ended lymphatic capillary
    • accompanied by smooth muscle
    • absorption of lipids (first site of fat absorption)
41
Q

describe microvilli

A
  • feature of enterocytes
  • major increase in luminal surface area
  • gives the cells a striated border
    • brush border
42
Q

describe enterocytes

A
  • simple columnar
  • primary absorptive cells
  • have secretory function:
    • produce digestive enzmyes
    • secretes water and electrolytes
  • tight junctions allow for selective absorption across the plasma membrane
43
Q

describe goblet cells

A
  • unicellular mucus secreting cells
  • renewed every 4-6 days
  • mucinogen granules accumulate in the apical cytoplasm
  • increase in number from duodenum to colon
44
Q

describe paneth cells

A
  • found in base of intestinal glands
  • renewed every 4 weeks
  • intensely acidophilic apical secretory vesicles
    • lysozyme: antibacterial enzyme, digests cell walls of certain groups of bacteria
    • a-defensins: microbicidal peptides
  • regulates normal bacterial flora in small intestine
45
Q

describe enteroendocrine cells in the small intestine

A
  • similar to those seen in stomach
  • found at the base of the crypts
  • renewed every 60-90 days
  • produce some of the same peptide hormones as stomach
    • CCK
    • secretin
    • GIP
    • motilin
46
Q

describe M cells in the small intestine

A
  • epithelial cells that cover Peyer’s patches and large lymphatic nodules
  • microfolds on apical surface rather than microvilli
  • antigen-transporting cells
47
Q

describe Brunner’s glands

A
  • located in submucosa of small intestine (duodenum)
  • secretes a highly alkaline solution that helps to neutralize the acidic chyme from the stomach
49
Q

describe the jejunum

A
  • numerous plicae circularis
  • long prominent villi (more absorption)
  • increase in goblet cells
  • no submucosal glands
50
Q
52
Q

describe Celiac disease

A
  • gluten sensitive enteropathy
  • autoimmune mediated intolerance to Gliadin (a glycoprotein found in gluten)
  • inflammation of mainly distal duodenum and prox. jejunum
  • mucosa appears flattened
  • 2 signs:
    • ​atrophy of villi
    • hyperplasia of cryts of Leiberkuhn
  • IgA antibodies for transglutaminase and endomysium and deamidated gladin peptide
53
Q

describe Crohn’s disease

A
  • ulcer formation of mainly small intestine especially the terminal ileum
  • malabsorption accompanied by crampy abdominal pain
  • underlying inflammation give a “cobblestone” appearance
  • granuloma formation with Giant cells
54
Q

describe the mucosa of the large intestine

A
  • numerous, straight, tubular, intestinal glands
    • crypts of Liberkuhn
  • principal functions:
    • reabsorption of water and electrolytes
    • elimination of waste
  • epithelium
    • simple columnar
      • no Paneth cells
        • you want bacterial flora to exist
      • abundant goblet cells
55
Q

describe the appendix

A
  • tenia coli ends at base of appendix
  • numerous lymphatic nodules
    • extend into submucosa
  • appendicitis
    • results from blockage of opening to the cecum
      • scarring, thick mucus or stool
56
Q
57
Q

describe the rectoanal junction

A
  • epithelium transitions from glandular intestinal epi. (simple columnar) to stratified squamous epi. (non-keratinized to keratinized)
58
Q

describe congenital megacolon (Hirschspring disease)

A
  • faulty migration of neural crest cells
  • lack of myenteric plexus
  • decreased peristaltic movements of the gut
  • dilated colonic segment
59
Q

describe hemorrhoids

A
  • causes:
    • any pathology which increases pelvic pressure
    • secondary to portal hypertension
    • chronic constipation
  • submucosal veins undergo progressive dilatation and bulge towards the lumen
  • internal: above pectinate line -> painless
  • external: below pectinate line -> painful

DM Histo (2 decks)

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