Introduction To The Gi Tract Notes
This is a sample of our (approximately) 3 page long Introduction To The Gi Tract notes, which we sell as part of the Gastrointestinal (GI) System Notes collection, a 1st (70-80%) package written at Bristol University in 2012 that contains (approximately) 57 pages of notes across 19 different documents.
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Introduction To The Gi Tract Revision
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Lecture 2 Introduction to the GI tract
Functions of GI system o Ingestion (taking in food) o Digestion
Food & large molecules chemically degraded to produce smaller molecules o Absorption
Nutrient molecules absorbed by cells that line GI tract & enter blood o Egestion (removal of waste) Structure of GI tract o See lecture notes Epithelia of the gastrointestinal tract o Turnover of cell layer in a couple of days o Types of cell
Goblet cell (mucous cell)
Microvacuolated columnar cell (will absorb salt and water)
Enteric endocrine cell (secrete paracrine/hormonal factors to help digestion) o Absorptive cell (small intestine)
Paracellular pathway (H2O)
Transcellular pathway (Na+/glucose transporter; Na+/K+ ATPase)
Absorption across basolateral membrane o Secretory cell (stomach)
Lots of Golgi apparatus and mitochondria
Secretion across apical membrane into lumen of intestine Movement of salt and water across intestinal epithelium
1. Sodium-potassium NKCC1 pump sets up gradient to allow Cl- pump to work
2. Cl- passively moves from high to low concentration passively
3. Na+/K+ ATPase 2
4. K+ channel to remove K+ to allow NKCC1 function
5. H2O and Na+ move into lumen paracellularly Gastrointestinal secretions o Five major secretory tissues
Salivary glands; Gastric glands; Exocrine pancreas; Liver-biliary system; Intestine o Total secretion= 8-9 litres/day o Containing: enzymes, ions, water, mucus etc. o Function: Breakdown large compounds, regulate pH, dilute, protect etc. Blood circulation of GI tract o Exuberant blood supply in villi & GI o Central Lacteal where fats are absorbed and taken into blood stream o Splanchnic circulation
Organised so important things absorbed are taken to liver first instance
After meal, 8 fold increase in splanchnic circulation
Most blood delivered where needed in tract
5 3 1 4
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