Alimentary Flashcards

Frage	Antworten
What are the four main basic processes of the GI tract?	1. Digestion - breaking down the food 2. Motility - moving the food 3. secretion - enzymes and solutes that are secreted to help digestion 4. Absorption - across into blood stream
What is the function of the regulatory peptides produced by the GI tract?	Stimulate digestive juices and cause organ movement.
What is the purpose of digestion?	Breaking down of macromolecules into smaller molecules that can be dissolved in the plasma to reach every cell.
How long is the GI tract? What is the advantage of this length?	20 feet long. It maximises absorption back into blood stream of useful molecules.
What secretions in the: mouth, stomach and small intestine assist digestion?	Mouth - saliva Stomach - gastic secretions Small intestine - pancreatic secretions, bile
In which part of the GI tract does absorption normally begin: a) oesophagus b) stomach c) small intestine d) colon	c - small intestine. In the stomach mainly secretion occurs.
What secretions are produced in the mouth and what are their functions?	Salt and water - chewing Mucous - swallowing Amylase - enzyme to digest polysaccharidse
What secretions are produced in the stomach and what are their functions? What is the normal pH of the stomach?	HCl - kills microbes Pepsin - digests proteins pH 1-2
What are the secretions in the liver and what are their functions?	Bile salts - solubilize water-insoluble fats Bicarbonate - neutralise HCl
Why is it that bicarbonate is able to neutralise HCl?	A neutralisation reaction occurs as it is between a strong acid and a strong base. Therefore this produces carbon dioxide and water.
How much water is absorbed in: a) the small intestine per day b) the colon per day	a) small intestine - 8.5 litres b) colon - 0.4-10 litres
How much secretion is there from each of the following per day and what is the pH? a) gastric, b) pancreatic, c) bile, d) intestine	a) 2 litres per day, pH 1.5-3.0 b) 1.5 litres per day, pH 8.0-8.4 c) 0.5 litres per day, pH 7.8-8.0 d) 1.5 litres per day, pH 7.8-8.0
How is water absorbed?	Passive osmotic forces
What kind of junctions separates cells? What is the function of these junctions?	Tight junctions. They block intercellular channels.
What changes occur to tight junctions during active absorption?	The tight junctions are permeable to H2O and small dissolved molecules. The absorbed solutes increase osmotic pressure and intracellular hydrostatic pressure which creates a driving force for movement of H2O.
What are the two main routes of absorption in the GI tract?	Transcellular and paracellular
True or false? Transcellular movement is passive and occurs via diffusion and convection?	FALSE. Transcellular is active, carrier-mediated, energy-dependent movement. Paracellular is passive.
What does diffusion across membranes depend on?	lipid nature of cell membrane.
What process influences convection?	Solvent drag.
How do tight junctions alter permeability in the GI tract?	They cause permeability to decrease from the proximal to the distal part of the tract.
True or false? Leakiness, permeability and electrical resistance decrease along the tract?	Trick question. Leakiness and permeability do decrease along the tract. Electrical resistance increases therefore less anions can be absorbed.
What are the four things that reflexes in the nervous system respond to?	1. Volume - distension of the wall 2. Osmolarity - gastric chyme 3. Acidity - duodenal chyme 4. Chyme products - concentration of digestion products.
Where does extrinsic nervous supply to the GI tract come from?	ANS
Where does intrinsic nervous supply come from and where it is found in the GI tract?	Enteric nervous system. It is embedded in the walls of the GI tract.
True or false: the myenteric plexus of the enteric nervous system is responsible for sensory function.	FALSE. The myenteric is mainly motor. The submucosal is mainly sensory.
Where do short reflexes occur: in the enteric nervous system or the ANS?	Enteric nervous system. They are independent of the CNS.
What is the function of long reflexes?	They allow the CNS to influence motility and secretory activity in the GI tract by using the ANS to influence the ENS.
What are the 3 phases of GI control?	1. Cephalic - before food has entered the GI tract 2. Gastric - when food is in the stomach 3. intestinal - where food enters the intestines
Name 3 of the endocrine hormones released by the GI tract.	Any from gastrin, secretin, cholecytokinin, pancreatic polypeptides, gastric inhibitory polypeptide, motilin, glucagon like peptides and neurotensin.
What are the two local hormones (paracrine) that are secreted by the GI tract? Where are they released to?	Histamine and somatostatin. Released to the interstitial fluid as they act on cells nearby so don't have far to travel (therefore don't need to travel in blood).

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