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AP0509 Component 2 Exam > Gastrointestinal Tract (plus Diseases) > Flashcards

Gastrointestinal Tract (plus Diseases) Flashcards

1
Q

What does the gastrointestinal tract consist of?

A
  • mouth (oral cavity)
  • oesophagus
  • stomach
  • small intestine (duodenum, jejunum, ileum)
  • large intestine (colon, caecum)
  • rectum
  • anus
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2
Q

What does the lip consist of?

A
  • skin
  • oral mucosa
  • vermilion border
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3
Q

Oral mucosa

A
  • thick stratified squamous
    epithelium, supported by a lamina propria
  • soft palate, underside of tongue, floor of mouth and mucosal surfaces: not keratinised, some may be parakeratinised
  • gums, hard palate, most upper surface of tongue: keratinised, some may be parakeratinised
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4
Q

Underneath the oral mucosa

A
  • tough collagenous submucosal layer with accessory salivary glands
  • thin submucosa where it lies over bone
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5
Q

Tongue - dorsal surface

A
  • Lingual Muscles (Striated): Extrinsic and Intrinsic
  • Sulcus Terminalis
  • V-shaped depression, divides tongue into anterior 2/3 + posterior 1/3. Foramen caecum at its apex.
  • Lingual papillae on the anterior 2/3: Filiform, Fungiform, Circumvallate, Foliate
  • Taste buds associated with select papillae
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6
Q

Filiform of lingual papillae

A
  • Small and Conical
  • Lined by keratinized stratified squamous epithelium
  • No taste buds
  • Mechanical function
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7
Q

Fungiform of lingual papillae

A
  • Mushroom shaped
  • Prominent on tip of tongue
  • Lined by stratified squamous epithelium
  • Taste buds in the epithelium on dorsal surface
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8
Q

Foliate of lingual papillae

A
  • Found on the lateral edges of tongue
  • Parallel rows separated by deep clefts
  • Taste buds
  • Rudimentary in human
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9
Q

Circumvallate of lingual papillae

A
  • 8-12 large and dome shaped found anterior to
    sulcus terminalis
  • Surrounded by a moat-like invagination which receives ducts of serous Von Ebner’s glands
  • Taste buds in epithelium of lateral surface
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10
Q

Taste buds

A
  • extend through the entire thickness of epithelium and detect taste stimulating particles from food
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11
Q

Composition of taste buds

A
  • Taste pore
  • Sensory neuroepithelial cells: synapse with afferent neurons (CN VII, IX, X), microvilli on apical surface, express 1 class of receptor protein, turnover ~ 10 days
  • Supporting cells: microvilli on apical surface, turnover ~ 10 days
  • Basal cells: stem cells
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12
Q

Teeth

A
  • main areas: crown and root
  • odontoblasts
  • ameloblasts
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13
Q

Odontoblasts

A
  • tall columnar secretory cells near pulp cavity
  • produce dentine, which is laid down and then calcified
  • dentine: 90% type I collagen, 70% wet weight hydroxyapatite
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14
Q

Ameloblasts

A
  • tall columnar secretory cells from ectodermal origin near surface tooth
  • produce enamel
  • enamel: 96% mineralised, hydroxyapatite the primary mineral, doesn’t contain collagen
  • they die when the tooth erupts
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15
Q

Salivary glands

A
  • 3 major pairs of salivary glands and many minor glands
  • Parotid glands on the inside of the cheeks
  • Submandibular glands at the floor of the mouth
  • Sublingual glands under the tongue
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16
Q

Acini in parotid glands

A
  • pure serous glands
  • Only serous cells (protein-secreting)
  • pure serous cells produce e.g. Amylase (carbohydrates)
  • Amylase stored apical in acidophilic secretory granules
  • Granules also contain peroxidase, lysozyme, cystatins
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17
Q

Ducts in parotid glands

A
  • secretory acini - intercalated ducts - intralobular or striated ducts - interlobular ducts - major ducts
  • parotid gland has longest intercalated ducts
  • myoepithelial cells around acini
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18
Q

Acini in submandibular glands

A
  • Mixed gland
  • Mostly pure serous acini, but also groups of mixed acini among the pure serous acini
  • Serous cells are filled with prominent, purplish-staining zymogen granules
  • Mucous cells (mucin-secreting) are pale-staining w/abundant clear cytoplasm. Arranged in duct-like structures, capped by so-called serous demilumes
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19
Q

Ducts in submandibular glands

A
  • Intercalated ducts are short, but present; striated ducts are long and clearly evident
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20
Q

Acini in sublingual glands

A
  • Mixed gland
  • Gland consist mostly of mucous acini capped with serous demilumes
  • The mucin-secreting cells predominate, with far less protein-secreting cells
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21
Q

Ducts in sublingual glands

A
  • Short intercalated and striated ducts, but are few in
    number
  • Long excretory ducts: Multiple sublingual ducts empty directly into the floor of the oral cavity, near to or with the submandibular ducts
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22
Q

Gross structure of oesophagus

A
  • ~25cm long muscular tube
  • Connects pharynx to stomach
  • Function: conduit for the bolus of food from the mouth
  • Lumen normally collapsed with longitudinal folds
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23
Q

Epithelium in oesophagus

A
  • stratified squamous non keratinised

- protects from mechanical and chemical injury

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24
Q

Lamina propria of oesophagus

A
  • connective tissue containing diffuse lymphatic tissue and lymphatic nodules
  • Oesophageal Cardiac Glands: mainly in terminal part, produces neutral mucus which protects from regurgitated gastric contents
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25
Q

Muscularis mucosae of oesophagus

A
  • single layer of longitudinal muscle
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26
Q

Submucosa of oesophagus

A
  • Dense irregular connective tissue
  • Large blood and lymphatic vessels
  • Submucosal Plexus (Meissner’s plexus)
  • Oesophageal Glands Proper: scattered throughout the length, produces slightly acidic mucous, lubricates the lumen, excretory duct lined by stratified squamous epithelium
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27
Q

Muscularis externa of oesophagus

A
  • typical 2 layers, inner circular and outer longitudinal
  • upper 3rd: striated
  • middle 3rd: striated and smooth
  • lower 3rd: smooth
  • myenteric plexus (Auerbach’s plexus)
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28
Q

Serosa and Adventitia

A
  • above diaphragm: fixed to adjacent structure by adventitia

- below diaphragm: serosa continuous w/that of the stomach

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29
Q

Oesophagogastric Junction

A
  • mucosa undergoes an abrupt transition
  • epithelium: stratified squamous to simple columnar
  • lamina propria: oesophageal cardiac glands replaced by cardiac glands of stomach
  • muscularis mucosa: 2 layers of smooth muscles arranged as inner circular and outer longitudinal
  • submucosa: oesophageal proper glands to NO glands
  • muscularis externa: inner oblique layer
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30
Q

Stomach

A
  • 3 region based on type of glands
  • cardiac region: near oesophageal orifice, contains cardiac glands
  • fundic region: situated between cardia and pylorus, contains fundic glands
  • pyloric region: distal, funnel-shaped region proximal to pyloric sphincter, contains pyloric glands
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31
Q

Mucosa of stomach

A
  • gastric pits or foveolae

- gastric glands: extend from muscularis mucosae, empty into gastric pits

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32
Q

Epithelium on stomach

A
  • lines gastric pits
  • simple columnar epithelium
  • surface mucus cells
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33
Q

Lamina propria on stomach

A
  • loose connective tissue

- surrounds gastric glands

34
Q

Muscularis mucosae on stomach

A
  • inner circular and outer longitudinal
35
Q

Submucosa on stomach

A
  • dense connective tissue

- lymphatics, blood vessels and submucosal plexus

36
Q

Muscularis externa of stomach

A
  • 3 layers of muscle: innermost oblique, middle circular: thickens to form the
    pyloric sphincter, outer longitudinal
  • Functions: to mix stomach contents (chyme) and force the partially digested food into the small intestines
37
Q

Serosa of stomach

A
  • Continuous with that of duodenum
38
Q

Cardiac region of stomach

A 
- Relatively short pits & short 
glands
- Tubular with occasional 
branching
- Cells: mucous-secreting, enteroendocrine
39
Q

Pyloric region of stomach

A 
- Relatively long pits and short 
glands 
- Branched, coiled, tubular with wide lumen 
- Mucus cells secrete a viscous mucus
- Enteroendocrine
40
Q

Fundic region of stomach

A
  • short pits: lined by surface mucus cells
  • long glands: simple branched tubular glands, 2-4 glands empty into one gastric pit, 3 parts: isthmus, neck, fundus
  • Cell types: mucous neck cells, parietal cells, chief cells, enteroendocrine cells, stem cells
41
Q

Hydrochloric acid (fundic gland secretion)

A
  • produced by parietal cells
  • Gives gastric juice low pH: < 1.0 to 2.0
  • Converts inactive pepsinogen into pepsin
  • Kills most bacteria
42
Q

Pepsin (fundic acid secretion)

A
  • Produced by chief cells
  • Potent proteolytic enzyme
  • Hydrolyzes proteins into
    small peptides
  • Converted from pepsinogen
43
Q

Mucus (fundic acid secretion)

A
  • Protective coating for the
    stomach
  • physiological barrier: neutral to alkaline pH: bicarbonate
  • physical barrier
44
Q

Intrinsic factor (fundic acid secretion)

A
  • essential for B12 absorption in the distal ileum
45
Q

Surface mucus cells

A
  • Secretes thick viscous mucus that adheres
    to epithelium - protects from acidity of gastric juice
  • Lines gastric pits
  • Elongated nucleus
  • Large apical cup of mucinogen granules takes up most of cytoplasm
46
Q

Mucus neck cells

A
  • Located in neck of gland
  • Secretes soluble mucous that helps transports gastric secretion to lumen
  • Smaller than SMC
  • Less mucinogen in apical cytoplasm
  • Spherical nucleus
47
Q

Parietal (oxyntic) cells

A
  • Secrete HCl and Intrinsic factor
  • Found throughout gland but concentrated in neck
  • Large mono or binucleated cells
  • Eosinophilic due to +++mitochondria
  • Extensive intracellular canalicular system that
    communicates with lumen of gland
  • Stimulated by gastrin
48
Q

Chief cells

A
  • Located at the base of gland
  • Typical protein-secreting cell: Abundant rER (Gives cells basophilic appearance), Apical zymogen granules
  • Secretions: Pepsinogen converted to pepsin by low pH (proteolytic enzyme), secretes weak lipase
49
Q

Enteroendocrine cells

A
  • secretes hormones into lamina propria
  • found throughout the gland: more prevalent in the base
  • Close cells: don’t reach lumen
  • Open cells: exposed lumen, serve as primary chemoreceptors
  • Gastrin secreting cells are concentrated in pyloric antrum
50
Q

Gastro-duodenal junction

A
  • mucosa: appearance of finger shaped villi
  • submucosa: appearance of Brunner’s glands (mucous)
  • muscularis: only 2 layers of muscles
51
Q

Small intenstine

A
  • longest component of digestive tract
  • principal site for digestion and absorption
  • receives chyme from stomach, enzymes from pancreas, microvilli of enterocytes, bile from liver
52
Q

Mucosa of small intestine

A
  • Simple columnar epithelium
  • Lamina propria contains Gut Associated Lymphatic Tissue
    (GALT)- ex. Peyer’s patches in ileum
  • Muscularis mucosae (MM)2 thin layers: Inner circular and
    outer longitudinal
  • Villi
  • Intestinal glands or Crypts of Lieberkühn
53
Q

Submucosa of small intestine

A
  • dense connective tissue
  • submucosal (Meissner’s) plexus
  • circular folds or Plicae circularis
  • duodenal submucosal glands
54
Q

Muscularis externa of small intestine

A
  • 2 muscle layers: inner circular and outer longitudinal with myenteric plexus
  • both are involved in peristaltic contraction
55
Q

Serosa/Adventitia

A
  • mainly serosa except 2nd, 3rd and 4th parts of duodenum
56
Q

Plicae Circulares or circular folds

A
  • Also referred to as Valves of Kerckring
  • Permanent transverse folds of the submucosa
  • Most numerous in distal duodenum and jejunum
  • Reduced in size and frequency in ileum
57
Q

Villi

A
  • Finger-like & leaf-like mucosal projections: 0.5-1.5 mm
  • Lamina propria contains central lacteals: blind-ended lymphatic capillary, accompanied by smooth muscle, absorption of lipids
58
Q

Crypts of Lieberkuhn

A
  • Simple tubular glands
  • Extend from muscularis mucosae to open unto
    lumen at base of villi
  • Continuous with epithelium of villi
  • Surrounded by lamina propria
59
Q

Enterocytes

A
  • Simple columnar epitheliocytes which are primarily absorptive, renew every 4-6 days
  • They also have secretory function: produce digestive enzymes, secretes water and electrolytes
  • Microvilli: Form the striated border which contains terminal digestive enzymes
    • Tight junctions: Allows selective absorption across the plasma membrane
    • Lateral plication: Increase lateral surface area
60
Q

Goblet cells

A
  • Goblet cells are unicellular mucous secreting cells
  • Renewed every 4-6 days
  • Mucinogen granules accumulate in the apical cytoplasm
  • Increase in number from duodenum to colon
61
Q

Paneth cells

A
  • found ib base of intestinal glands
  • renewed every 4 weeks
  • intensely acidophilic apical secretory vesicles
  • lysozyme: antibac enzyme, digest cell walls of certain groups of bacteria
  • alpha-defensins: microbicidal peptides
  • basophilic basal cytoplasm
  • regulate normal bacterial flora in small intestine
62
Q

Enteroendocrine cells

A
  • Closed cells concentrated in lower portion of intestinal
    gland
  • Open cells found at all levels
  • Found at base of the crypts
  • Renew every 60-90 days
  • Produce some of the same peptide hormones as stomach
  • Most active regulators of GI physiology released in the small intestine: CCK, secretin, GIP, motilin
63
Q

M cells

A
  • Epithelial cells that cover Peyer’s patches and large lymphatic nodules
  • Microfold cells
  • Modified enterocytes
  • Cover enlarged lymphatic nodules
  • Microfolds on apical surface rather than microvilli
  • Antigen-transporting cells
64
Q

What makes M cells antigen-transporting cells?

A
  • Take up microorganisms & macromolecules from lumen
  • Transport vesicles to basolateral cell membrane
  • Discharge vesicle contents into intercellular space
  • Processed substances interact with cells of GALT
65
Q

Parts of large intestine

A
  • Colon: ascending, transverse, descending, sigmoid
  • Cecum & vermiform appendix
  • Rectum
  • Anal canal
66
Q

Characteristic features of large intestine

A
  • Taenia coli (TC): 3 thickened bands of the outer longitudinal muscularis externa layer
  • Haustra coli (HC): visible sacculations between TC, external surface of cecum and colon
  • Omental appendices (OA): small fatty projections of the serosa, outer surface of colon
67
Q

Mucosa of large intestine

A
  • “Smooth” surface
  • Numerous, straight, tubular, intestinal glands: crypts of Lieberkühn
  • Principal functions
  • Reabsorption of water & electrolytes
  • Elimination of waste
  • Epithelium: simple columnar, no Paneth cells, abundant goblet cells
  • Lamina propria contains GALT
    • Muscularis mucosae: Inner circular, Outer longitudinal
68
Q

Muscularis externa of large intestine

A
  • Found in ascending, transverse, descending and sigmoid colon, cecum
  • Inner circular layer
  • Outer longitudinal layer: Teniae coli (TC), Prominent longitudinal bands of longitudinal muscle
  • Myenteric (Auerbach’s) plexus
69
Q

Appendix

A
  • thin, finger-like extension of the cecum
  • Tenia coli ends at base of appendix - quick identification during appendectomy
  • Distinguishing characteristic- Numerous lymphatic nodules that extend into submucosa
  • Appendicitis: results from blockage of opening to
    the cecum, scarring, thick mucus or stool
70
Q

Rectum

A
  • Distal dilated portion of
    alimental canal
  • Anatomic transverse folds
  • Mucosa is same as colon: intestinal glands (Crypts
    of Lieberkühn), abundant goblet cells
    • Muscularis externa: No tenia coli - continuous outer longitudinal layer
  • Adventitia
71
Q

Recto anal junction

A
  • Internal anal sphincter – thickened inner circular layer
    of the muscularis externa
  • External anal sphincter – Striated muscle of the pelvis
72
Q

Barrett’s oesophagus (metaplasia)

A
  • Heartburn: burning sensation felt behind the breastbone (sometimes in neck and throat)
  • Caused by stomach acid refluxing up into oesophagus
  • At lower end of oesophagus where it enters the stomach: Lower Oesophageal Sphincter, should remain tightly closed, except to allow food and liquid to pass into the stomach, heartburn occurs when the LES opens at the wrong
73
Q

Gastroesophageal Reflux Disease (GERD)

A
  • heartburn severe or
    occurs frequently over a long period of time
  • if untreated, constant acid irritation to lining of the oesophagus, and complications can occur
  • 1 in 10 with GERD are found to have Barrett’s oesophagus some of which may lead to invasive adenocarcinoma of the
    oesophagus
74
Q

Gastric and duodenal ulcer

A
  • H. Pylori secretes urease and proteases: break down mucus, creates an alkaline
    environment) - stimulates
    gastrin - increase acid/pepsin
  • causes chronic gastritis, exposing the surface to the effects of pepsin and acid.
  • Irritated and inflamed membrane becomes necrotic, leaving a hole.
  • HCl secretion is under nerve and hormonal control, stressful situations can trigger ulcers.
75
Q

Coeliac disease

A
  • gluten sensitive enteropathy
  • autoimmune mediated intolerance to Gliadin
  • marked inflammation of mainly distal duodenum and proximal jejunum
  • mucosa appears flattened due to villi atrophy and crypts hyperplasia
  • increased lymphocytes and plasma cells in lamina propria
76
Q

Diagnosis of coeliac disease

A
  • IgA antibodies for transglutaminase and endomysium and deamidated gliadin peptide
  • mucosal changes can revert to normal w/ gluten free diet
  • may lead to malignancy (10-15%)
77
Q

Crohn’s disease

A
  • Ulcer formation of terminal ileum in SI as well as LI, and
    upper GI
  • Malabsorption accompanied by crampy abdominal pain
  • Long fissure-like ulcers with normal mucosa in between
  • “cobblestone” appearance
  • Patchy distribution of ulcers (skip lesions)
  • Non caeseating Granuloma formation with Giant cells
  • Ulceration frequently extends through all layers of the wall producing fistulas
  • Fibrosis from chronic inflammation results in strictures - obstruction
78
Q

Hirschsprung’s disease

A
  • Congenital disorder of the colon
  • Incomplete migration of cells from neural crest into large colon
  • Absence of ganglia nerve cells (Auerbach and Meissner plexus)
  • Variable length but seldom >30 cm
  • That section of colon is essentially paralyzed
  • Chronic constipation
  • Diagnosis (Barium enema (mainstay), rectal biopsy (only certain)
  • Pull-through surgery
79
Q

Oesophageal varices

A
  • Extremely dilated submucosal veins
  • Lower 3rd of oesophagus
  • Cause: mostly liver cirrhosis (alcohol)
  • risk of bleeding increases with pressure in portal vein (portal hypertension)
  • Variceal haemorrhage carries a high mortality/recurrence
80
Q

Haemorrhoids

A
  • Dilations of the submucosal veins
  • Any pathology with increased pelvic pressure
  • Secondary to portal hypertension
  • Chronic constipation
  • Internal (painless), external (very painful)
  • Bleeding, thrombosis, infection

AP0509 Component 2 Exam (21 decks)

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