Upper GI Flashcards
(23 cards)
What are the components of the GI system?
- Salivary glands
- parotid, sublingual, sub-mandibular
- Oesophagus
- Stomach
- Small bowel
- duodenum, jejenum, ileum
- Liver and gall bladder
- Large bowel
- appendix, ascending, transverse, descending,
sigmoid colon
- appendix, ascending, transverse, descending,
- Rectum
- Anus
What are the 4 layers of the gut wall?
- Mucosa —> innermost
- epithelium, lamina propria (connective),
muscularis mucosae
- epithelium, lamina propria (connective),
- Sub-mucosa
- connective tissue
- meissners plexus
- submucosal glands
- Muscularis
- longitudinal, circular (+oblique in stomach) muscle
- myenteric plexus
- Serosa/Adventitia —> outermost
- connective tissue (+epithelium)
What is the arrangement of teeth in the oral cavity?
32
- 8 incisors
- 4 canines
- 8 premolars
- 12 molars
Which muscle is responsible for biting?
Masseter —> largest jaw muscle
What are the 3 salivary glands?
- Parotid —> down from ear
- Sublingual —> under tongue
- Submandibular —> furthest down
- aqueous —> soften food
- enzymes —> salivary amylase
—> lingual lipase
What are the 2 sets of muscles of the tongue?
- Intrinsic - only in tongue
—> alter shape - Extrinisic - attach to other structure
—> move position of tongue
What is the structure of the oesophagus?
- 25cm —> C5/6 to T10/11
- in posterior mediastinum
- start —> upper oesophageal sphincter (under
cricopharyngeus muscle) - end —> cardia of stomach
What is the 15-25-40 rule?
Endoscopy —> marks constrictions:
- 15 cm —> cricopharyngeal constriction
- oesophagus starts
- striated muscle (voluntary control) - 25 cm —> aortic and bronchial constriction
- 40cm —> diaphragmatic and sphincter constriction
- oesophagus ends (Z-line)
- smooth muscle (involuntary control)
What is the function of the oesophagus?
Move food from pharynx to stomach
- Epithelium - non-keratinised, stratified, squamous
- damaged by extreme temps/textures
- lubricated by mucus
- Muscle - peristalsis
- upper —> striated
- closed at rest
lower —> mainly smooth
- vagus —> myenteric plexus
What are the 4 stages of swallowing?
Stage 0: Oral phase
- mouth forms bolus
- oesophageal sphincters closed
Stage 1: Pharyngeal phase
- bolus from pharynx to oesophagus
- oesophageal sphincters open
Stage 2: Upper oesophageal phase
- superior circular rings contract
inferior circular rings dilate
longitudinal muscle sequentially contracts
- upper sphincter closes
Stage 3: Lower oesophageal phase
- bolus to stomach
- lower sphincter closes
What is the gastro-oesophageal Z line?
Visible junction between oesophageal and gastric mucosa
- epithelial transition: stratified squamous —> simple
columnar (stomach acid protection)
What are the 3 functions of the stomach?
- Break down food
- Release food to duodenum steadily
- Kill parasites/bacteria
What is the structure of the stomach?
- Cardia —> joins to oesophagus
- Fundus —> top bend
- Body
- Pyloric —> bottom (antrum and canal)
- rugae —> allow for expansion
—> crypts for glands
Which 4 chemicals are secreted by the stomach?
- Mucus —> gel coat to protect tissue (+ rapid
epithelial turnover)
—> trap HCO3- - HCl —> kill microorganisms
- 2L/day
- 150mM H+ conc
- lumen pH 1-2 (epithelial surface 6-7) - Pepsinogen —> denatures proteins
- Gastrin —> stimulates HCl production
What are the 5 secretory cells of the stomach?
- Chief —> pepsinogen
- Parietal —> HCl
- Mucus neck —> mucus
- Surface mucus —> mucus (traps HCO3-)
- Enteroendocrine —> gastrin
What is secreted from where in the stomach? (3)
- Cardia and pyloric —> mucus
- Body and fundus —> mucus
—> HCl
—> pepsinogen - Antrum —> gastrin
What is the function of gastric chief cells and how are they adapted?
Secrete pepsinogen (HCl cleaves to pepsin)
- inc RER
- inc golgi
- inc apical secretion granules
What is the function of gastric parietal cells and how are they adapted?
Produce HCl
- inc mitochondria —> for H+/K+ ATPase
- internal canaliculi —> secretory
- project into canaliculi
- cytoplasmic tubulovesicles —> H+/K+ ATPase
- fuse with membrane
How is stomach acid produced?
- CO2 diffuse from blood into parietal cell
- H2O into parietal cell via aquaporin
- CO2 + H2O —> H2CO3 using carbonic anhydrase
- H2CO3 —> H+ + HCO3
- H+ into lumen via H+/K+ ATPase
- HCO3- to blood via HCO3-/Cl- antiport —> Cl- in
- Cl- into lumen via fac diff
- H+ + Cl- —> HCl in lumen
What are the 3 stimulants of HCl production?
- ECL cells produce histamine —> binds H2 receptor
- G cells produce gastrin —> binds to gastrin receptor
- Vagus nerve releases ACh —> bind to muscarinic
receptor
Which drugs inhibit stomach acid production and how? (3)
- Pantoprazole —> inhibits H+/K+ ATPase
- PPI (proton pump inhibitor) - Omeprazole —> inhibits H+/K+ ATPase
- PPI (proton pump inhibitor) - Ranitidine —> inhibits H2 receptor
What is the function of gastrin?
Stimulates HCl production
- binds to parietal cell receptors
- stimulates histamine release from chromaffin cells
- secreted from pyloric antrum
- secretion stimulated by stomach distension, small
peptides and amino acids, vagus nerve
What are the 3 phases of gastric secretion?
- Cephalic phase:
- thought/sight —> cerebral cortex —>
hypothalamus + medulla oblongata —> vagus
nerve —> stomach secretions - taste/smell —> hypothalamus + medulla
oblongata —> vagus nerve —> stomach secretions
- thought/sight —> cerebral cortex —>
- Gastric phase:
- food in stomach —> distension —> stretch
receptors —> medulla —> vagus nerve —>
stomach - food chemicals/pH change —> chemoreceptors
—> gastrin to blood
- food in stomach —> distension —> stretch
- Intestinal phase:
- stomach emptying —> low pH in duodenum —>
gastrin to blood
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- stomach emptying —> low pH in duodenum —>
