GI Tract

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  • Created by: Molly
  • Created on: 05-06-14 09:16
What is the structure of the GI tract? Outside in
Serosa - Muscularis externa - Submucosa - Muscosa
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What does the Muscosa contain?
Epithelium, Lamina propria, Muscularis mucoase
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What does the Muscularis externa contain?
Circular and Longitudinal muscle
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What's the other name for the submucosal plexus?
Meissner's plexus
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What's the other name for the Myenteric plexus?
Auerbach's plexus
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How much fluid is secreted in total from the GI tract?
8-9 L/day
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What's gastrin involved in?
Gastric secretion and motility
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What's CCK involved in?
Gallbladder contraction and pancreatic secretion
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What GIP involved in?
Inhibits gastric secretion and stimulates insulin release
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What control is salivary secretion under?
Neural control (both branches stimulate)
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Ach does what?
Decreases NaCl reabsorption
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NA does what?
Stimulates HCO3- secretion
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Aldosterone does what?
Stimulates NaCl reabsorption and K+ secretion
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Which parts of the brain are involved in swallowing?
Medulla and lower pons
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What happens in the oral or voluntary phase of swallowing?
The tongue presses the food against the hard palate and the bolus if forced into the pharynx stimulating the touch receptor
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What happens in the pharyngeal phase of swallowing?
Soft palate elevates, epiglottis closes trachea, upper oesophageal sphincter relaxes
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What happens in the upper oesophageal phase of swallowing?
Upper oesophageal sphincter closes
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Which region of the stomach relaxes during swallowing?
Orad region
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What's the vomiting reflex controlled by?
The brain stem
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What's the first step in vomiting?
Reverse peristalsis
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What's the next step?
Pyloric sphincter and stomach relax
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Forced inspiration occurs against a closed what?
Glottis
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What the happens?
A sharply elevated intra-abdominal pressure
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What's the last stage?
Reflex relaxation of the upper oesophagus sphincter
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How much fluid is secreted from the stomach?
1.5-2.5 L/Day
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What's secreted from the oxynic glandular region?
HCl, intrinsic factor, Pepsinogens, Mucus, histamine
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What's secreted from the cardiac glandular region?
Mucus
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What's secreted from the pyloric glandular region?
Mucus, gastrin, somatostatin
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Describe the types of stimulation of HCl
Paracrine- ECL cell = Histamine and Endocrine- G cell = Gastrin
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What stimulates the Ca signalling pathway?
Ach and Gastrin
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What stimulates and inhibits the cAMP signalling pathway?
+ Histamine, - Somatostatin
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Where is intrinsic factor secreted from?
Parietal cells in the gastric fundus
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What does intrinsic factor help with?
Absorption of Vit B12 in the ileum
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In gastric secretion (stomach), what's the cephalic phase dependent on?
The vagal nerve
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In gastric secretion (stomach), what's the gastric phase dependent on?
Local and vagovagal reflexes and hormones
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What acts as a reservoir in receptive relaxation?
Fundus and body
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What happens in peristalsis contraction within the stomach?
Body and antrum mix food with secretions
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What happens in tonic contraction within the stomach?
Pylorus controls the emptying of food into the duodenum
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What controls gastric emptying?
Neurons and hormones
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Gastric emptying doesn't exceed the rate of what?
Acid neutralisation, fat emulsification, and production of chyme in SI
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What are the endocrine secretions of the pancreas?
Insulin and glucagon
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What are the exocrine secretion of the pancreas?
Salts, water and enzymes
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In pancreatic secretion, what's the cephalic phase dependent on?
Vagal impulses
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In pancreatic secretion, what's the gastric phase dependent on?
Vagovagal and gastropancreatic reflexes
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In pancreatic secretion, what's the intestinal phase dependent on?
Hormones
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Where is bile secreted and stored?
From hepatocytes and in the gallbladder
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In gallbladder secretion, what are the cephalic and gastric phases dependent on?
Vagovagal reflexes
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What happens in the intestinal phase of gallbladder secretion?
Fatty Acids - CCk - contraction etc
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Which nerves cause contraction of the gallbladder?
Sympathetic
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What's the enterohepatic circulation?
Bile acids are reabsorbed from the ileum
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How much is secreted from the small and large intestines?
1 Litre/Day
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What are two special features of the large intestine?
No villi or nutrient absorption
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What's a special feature of the small intestine?
No active K+ secretion
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Give an example of brush border hydrolysis of oligomer to monomer
Sucrose to glucose and fructose
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How is protein digested and absorbed?
Luminal hydrolysis of polymer to monomer
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How are peptides digested and absorbed?
Intracellular hydrolysis
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How are triglycerides digested and absorbed?
Luminal hydrolysis followed by intracelluar resynthesis
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What does lactase do?
Splits lactose into galacose and glucose
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What does maltase do?
Produces glucose monomers
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What does sucrase do?
Splits up sucrose, maltose and maltotriose
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What does isomaltase do?
Splits a-limit dextrins, maltose and maltotriose
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What are carbs broken down into, and by what?
a-dextrins, di & trisaccharides by a-amylase
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What's this product then broken down into and by what?
Glucose, galactose and fructose by oligosaccharidases
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What are proteins broken down into and by what?
Aa, di & tripeptides by proteases
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How are fats digested and absorbed?
Emulsion droplets, pancreatic enzymes -- micelles, diffusion, exocytosis
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Other cards in this set

Card 2

Front

What does the Muscosa contain?

Back

Epithelium, Lamina propria, Muscularis mucoase

Card 3

Front

What does the Muscularis externa contain?

Back

Preview of the front of card 3

Card 4

Front

What's the other name for the submucosal plexus?

Back

Preview of the front of card 4

Card 5

Front

What's the other name for the Myenteric plexus?

Back

Preview of the front of card 5
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