Flashcards
GI tract structure and function
Cards in this deck (43)
- 1What are the four main functions of the digestive system?Digestion
Secretion (of chemicals)
Absorption (of
Motility - 2Function of the mouthBreakdown of foodstuffs by chewing
Three pairs of salivary glands (sublingual, submandibular, parotid) produce saliva, which acts as a lubricant and increases water content of food (reduces osmotic pressure) - 3Function of the oesophagusConduit between mouth and stomach
- 4Why is it better for food to be broken down th into monomers e.g. glucose or amino-acids an left as long-chain polymers e.g. polysaccharides or proteins?An influx of single monomers into the GI tract would create massive osmotic pressure, causing large volumes of water to enter the gut tube
Stretching of the gut tube causes massive amounts of pain - 'dumping syndrome' - 5Function of the stomachProtein digestion
Reduction of foodstuffs to liquid form
Storage
Sterilisation - 6Why is it important that the stomach 'stores' food after eating?If all food passed through to the gut tube immediately after eating, osmotic pressure would be massive due to sheer number of particles - 'dumping syndrome'
Also ekes energy from food out - 7Why is it important that the stomach converts solid foodstuff into liquid?Chemical digestion is more efficient in solution
- 8By what method does the stomach break down protein?Acid hydrolysis (via HCl produced by stomach)
- 9Function of the pancreasProduces digestive enzymes to break down fats, carbohydrates and proteins
- 10Why is it important for the pancreas to remain healthy?Contains vast numbers of enzymes, so is capable of autodigestion (of itself and surrounding body)
- 11What would happen if the mouth/salivary glands and stomach could no longer digest food?Very little - pancreas has enough enzymes to override any previous digestion, so it would carry on as normal
- 12Function of the liverProduces bile salts for sped-up digestion and absorption of fats in small intestine (emulsifies lipids)
- 13Function of the gallbladderStorage and concentration of bile
- 14Why is the gallbladder's function important?Removal of water concentrates bile
Enables large amounts of fat to be digested at once - 'Fairy liquid vs smart-price'
Compared to rats, which 'drip-feed' bile throughout the day making it weaker - 15Function of the small intestineFinal stages of chemical digestion and nutrient absorption
Mostly occurs in the first two-fifths - rest is residual capacity, to 'catch up' on anything bypassed - 16Function of the large intestineAbsorption of water
Bacterial fermentation
Faeces formation - 17General structure of the alimentary canalContinuous hollow tube (diameter varies)
~8m long
Four distinct layers - 18Name the tunics of the canalMucosa (epithelium, lamina propria, muscularis mucosae)
Submucosa
Muscularis externa
Serosa/adventitia - 19Describe the mucosaEpithelium (top layer)
Lamina propria
Muscularis mucosae (smooth muscle, supportive in function)
Gland ducts extend from submucosa in oesophagus and duodenum only - 20Describe the submucosaThicker, irregular connective tissue (supportive base)
Contains neurones (network i.e. submucosal plexus), blood vessels (out to mucosa, ME, serosa), lymph vessels
In oesophagus and duodenum only; glands within submucosa (ducts extend into mucosa) - 21Describe the muscularis externaFormed of two separate layers (circular/inner and longitudinal/outer)
Myenteric plexus present between two layers - 22Function of the muscularis externaEnables motility
Contraction of the circular muscle constricts diameter of the tube
Contraction of the longitudinal muscle shortens tube - 23What is the intramural plexus?Plexus formed by combining myenteric and submucosal plexi - known as ENS
Submucosal (Meissner's) is within submucosa; parasympathetic (R&D)
Myenteric (Auerbach's) between muscle layers; both (para)sympathetic - 24Describe the mucosal epitheliumStratified squamous in mouth, oesophagus and anal canal
Simple columnar in stomach and both intestines
Barrier separating 'outside' (within gut tube) from 'inside' (rest of body)
Synthesises and secretes enzymes, hormones, mucus, absorbs digestive products - 25Describe the lamina propriaLoose connective tissue, with glands and blood and lymph vessels
- 26Describe serosa/adventitiaConnective tissue outer layer
Outside peritoneal cavity (adventitia) - attaches oesophagus, rectum to surroundings
Inside (serosa) - surrounds stomach, S&L intestine - 27What is special about the ENS?Enables independent control of gut function, regardless of brain
- 28Give an overview of the nervous control of alimentary functionAutonomic: either long (parasympathetic) or short (ENS) reflexes
Parasympathetic response produced by vagus nerve (X) - stimulatory
Sympathetic produced by splanchnic nerve - inhibitory - 29What are the exceptions for nervous control?Salivation controlled by facial (VII) and glossopharyngeal (IX) parasympathetically
Salivation also stimulated by splanchnic nerve sympathetically (all others inhibited) - 30Which arteries supply the GI tract?Descending aorta splits into coeliac trunk, superior and inferior mesenteric arteries
- 31Which organs are supplied by which artery?Coeliac trunk: stomach, duodenum, pancreas, liver, spleen (via splenic artery, a branch)
SMA: jejunum, ileum, caecum, ascending and transverse colon
IMA: descending and sigmoid colon, rectum - 32Which veins drain the GI tract?Gastric veins: stomach
Splenic vein: pancreas, fundus, spleen
SMV: small intestine, caecum, ascending and transverse colon
IMV: descending and sigmoid colon, rectum
Hepatic portal vein drains all above veins, then travels into hepatic vein then IVC - 33Which potential function does the muscularis mucosae have?Movement of villi on surface
- 34Why are do all veins drain into the hepatic portal vein?Liver is in series with rest of organs (usually everything is in parallel to receive oxygenated blood)
Liver receives nutrients, can form glycogen etc. - 35Describe the structure of the epithelial cells and the 'brush-border'Apical membrane facing lumen, made up of microvilli - the 'brush border', which can release enzymes
Tight junctions between individual cells forming a 'sheet'
Basolateral membrane around remainder of cell - 36What are the three types of transport through cells?Transcellular: down directly through cell
Paracellular: between cells, through gaps
Vectorial: facillitated by membrane proteins (at least one per end, if not more) - 37How are vectorial proteins expressed?Transcription, translation, rER, Golgi, vesicles, expression on surface (apical or basolateral)
- 38How do glucose and galactose pass through membranes?Glu and Na must be present outside cell: SGLT1 undergoes conformation change, transports both in
GLUT2 transports Glu back out other side when concentration greater than 5mmol; Na passes out via ATPase
Water also passes paracellularly to counteract osmotic pressure change - 39How is potential difference of cells set up?Sodium-potassium ATPase present on BL membrane creates negative potential difference between inside and out (potassium in, sodium out)
- 40How is fructose transported?More direct than glucose/galactose
Moves in via GLUT5, out via GLUT2 (same as glucose/galactose)
No sodium transported and fructose immediately metabolised therefore no osmotic effect and no water movement - 41What differentiates endo- and exopeptidases?Endopeptidases form two smaller peptides from the original long chain by hydrolysing it in the middle
Exopeptidases are either amino- or carboxy-peptidases, which work at the ends of the peptides to form a single amino acid and a peptide chain one monomer shorter - 42How are amino acids transported in?Very similar to glucose/galactose
Na and AA present causes conformational change in SAAT1 (a generic protein name)
Na immediately removed from inner cell by ATPase
AA passes out via membrane protein
Water passes to equalise osmotic pressure - 43How are di/tripeptides transported?Acidic environment = abundance of hydrogen ions which drive PepT1 transporters to move peptides into cell
H then moves out again by swapping with Na via NHE3 transporter
Na moves out via ATPase
Peptide moves out via unknown transporter
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- Gastrointestinal Flashcards on GI tract structure and function, created by Phoebe Williams on 15/09/2018.
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- Phoebe Williams
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