GIT physiology Flashcards

Question

describe the control of gastric emptying?

Answer 1

stomach emptying occurs when pressure created by stomach pump exceeds pyloric pressure in general, gastric emptying is proportional to fullness of stomach i.e. fuller, the quicker howeveer there are a number of neural and hormal factors influencing this... neural = enterogastric reflex * food in duodenum - walls stretch - vagus nerve inhibited - reduces motility , slows emptying. * gives time and control over emptying hormonal = * chyme + acidity in duodemum, release of CCK and secretion - reduce motility External * prokinetics (erythomycin, neostig, metoclop) * opiods * pain, fear - reduces

Answer 2

mechanical - churning chemical - pepsin, acidity

Answer 3

both a voluntary and involuntary process 1. voluntary movement of food bolus to posterior mouth. sensory afferents via trigeminal, glossopharyngeal and vagus to swallowing centre 2. causes brainstem activation of swallowing stages. elevation of soft palate to close off nasopharynx 3. closure of vocal cords and larynx drawn down. epiglottis swings over cords. upper oesophageal spinchter widens 4. peristasis starting in upper oesophagus - coordinated by swallowing cells (medulla and pons). swallowing centre inhibits resp centre. LOS relaxes.

Answer 4

carbohydrates - amylase in saliva and pancreatic juices. makes oligosaccharides and disaraccharides. further broken down by lactase, sucrase and maltase into glucose which can be absorbed. proteins = pepsin and aa are absorbed fats = lipase and emulsification

Answer 5

lipids are emulsified by bile salts increases S.A for lipase to breakdown triglycerides to FFA and glycerol FFA, cholesterol, fat soluble vitamins and other molecules form micelles at the luminal membrane, FFA and monoglycerides leave the micelle and are absorbed into intestinal cell. within intestinal cell, they reform to form chylomicrons chylomicrons enter lymphatics via exocytosis enter blood at thoracic duct capillary endothelium has lipoprotein lipase which further digests and allows uptake of FFA to cells. chylomicrons with removed FFA return to hepatocytes

Answer 6

secondary ATP Na/K ATPase on basolateral membrane gradient for NA into the cell SGLT 2 = cotransport for Na and glucose - luminal GLUT 2 = basolateral

Answer 7

nausea - unpleasant experience / senation of the need to vomit vomitting - physical involuntary forceful expulsion of gastric content via the mouth

Answer 8

complex process involving many afferent and efferent pathways Thought to be coordinated by the vomitting centre - an area within the medulla oblongata made of multiple neural connections. This recieves 3 main inputs * chemoreceptor trigger zone - lies at base of 4th ventricle, area postrema and lies outside of BBB allowing it to sense toxins within the blood and input into vomitting centre * nucleus tractus solitarus - lies within medulla - recieves inputs from various areas (vestibular apparatus, GIT, pain afferents) * higher centres - pain, emotion, fear, raised ICP various neurotransmitters and receptors are involved including dopamine, serotonin, acetylcholine, histamine and mu opioid receptors. once threshold reached, central pattern generator activated and vomitting initiated.

Answer 9

pre-ejection - nausea, activation of sympathetic NS - sweating, tachycardia. also parasymp - salivation, relaxation of oesophageal sphincters and retrograde peristalsis retching - respiration caeses, glottis closes, larynx rises, soft palate elevates - protect airway ejection phase - coordinated contraction of diaphragm and abdominal muscles.

Answer 10

toxins in blood - CTZ - many receptors D2, 5HT3, u opioid, neurokinin (sub P) vesticular apparatus - motion sickness - via H1 and M3 reecptors GIT - toxins in gut lumen, gut visceral pathology - 5HT3, dopamine receptors and substance P all implicated. e.g. 5HT3 receptors on end of vagal afferents which transmit impulses to vomitting centre. raised ICP

Answer 11

electrolyte disturbance dehydration aspiration poor absorption/ malnutrion increase ICP wound dehiscence

Answer 12

patient factors - anxiety, female, previous PONV or motion sickness, non smoker, dehydration anaesthetic factors - inhalation agents, N20, opioids . over use of bag/ mask ventilation and stomach inflation surgical factors - obsteric, cholecystectomy, middle ear , laparoscopic

Answer 13

increases with age - more likely than adults rare under 2 no sex differences before puberty

Answer 14

APFEL * adult scoring system * 1 point for each = female, non smoker, opioids, prev PONV * each point = 20% POVOC * paediatric tool * 1 point = op more than 30mins, stradbidmus surgery, prev PONV, FHx PONV

Answer 15

major organ within body sits in RUQ consisting of 2 anatomical lobes divided by falciform ligament. also 2 smaller accessory lobes = caudate and quadrate lobe.

Answer 16

anatomical - 2 unequal lobes divided by falciform ligament physiological - 2 more equal size lobes, determined by their bilary drainage and blood supply. can be further divided into 8 functional units 4 on each side.

Answer 17

falciform - between R and L lobe. also attaches anterior surface to anterior abdo wall. coronary - attaches superior surface to diaphragm triangular ligaments - attach left and right lobe to diaphragm

Answer 18

made up of millions of lobules Whereby there is a branch of the hepatic vein at the centre of a hexagonal structure at each corner of the hexagon is the portal triad = hepatic artery, portal vein, bile duct 30% of blood flow is via hepatic artery and 70% via the portal vein however hepatic artery and portal vein supply around 50:50 of O2 content to the hepatocytes - they drain into sinusoids which lie between the hepatocytes. these sinusoids eventually meet and drain into the hepatic vein. bile duct cannuli also line the hepatocytes, which make bile which is drained via bile duct the liver can also be divided into zones 1,2,3 - this is a functional division (acinus) - zone 1 is closest to arteries and zone 3 closest to hepatic vein.

Answer 19

liver acinus = functional unit

Answer 20

hepatic artery and portal vein empty into the sinusoids - capillaries which pentrate hepatocytes and drain into hepatic vein. large gaps (sinusoidal cap) to allow passage of proteins and sometimes cells close association with kupffer cells

Answer 21

zone 1 = metabolism - most oxygenated region, rich in mitochondria. glycogen synthesis etc zone 3 - drug detox , CYP450 - poorest blood supply. at risk of ischaemia. anaerobic.

Answer 22

extremely vascular organ, recieves 25% of CO (1500ml/min). 30:70 hepatic artery: portal vein but 50:50 O2 supply both enter at the hilum and divide to eventually supply portal triad portal vein goes to liver after draining and supply GIT, pancreas, spleen. (from superior mesenteric plexus) hepatic artery comes from coeliac trunch which arises from aorta hepatic vein - drains into IVC

Answer 23

hepatic blood flow alters throughout the day with reduces with sleep, exercise, increases after a meal. hence needs regulation. mostly controlled via hepatic artery (rather than portal vein). intrinsic * myogenic response - up to MAP 60mmHg- 150mmHg * hepatic arterial buffer response - if portal vein flow is reduced, hepatic artery is increased and vice versa to help maintain flow. this occurs via adenosine. adenosine is constantly being produced around portal triad, if flow is reduced, it builds up and causes vasodilation of hepatic artery to increase flow. extrinsic - neural - sympathetic NS - A1 - humeral - catecholamines, angiotensin II, ADH. also nitric oxide (vasodilation), and secretin, glucagon and CCK all cause vasodilation and improved flow - drugs - volatiles reduce flow

Answer 24

bile is made by hepatocytes drained via bile caniculi in lobules into bile duct within liver follows series of bile ducts e.g. interlobular, septal. eventually ends in left and right hepatic duct which join to fom common hepatic bile duct then common bile duct which enters duodenum at sphincter of oddi. pancreatic duct also drains into common bile duct

Answer 25

depends on which zone 1 = many mitochondria and glycogen synthesis enzymes, more RER for protein synthesis. zone 3 = rich in SER and CYP450

Answer 26

bile is composed of bile pigments (bilirubin, biliverdin), cholesterol, phospholipids, bile acids and electrolytes. it is produced by hepatocytes and enters the biliary system and is secreted into the small intestine to aid with digestion. prior to secretion it is stored in the gall bladder where it is concentrated by primary and secondary AT. released from gall bladder by CCK (causes contraction) when fatty acids are present in duodenum. also vagal stimulus causes contraction. primary bile salts include cholic acid and chenodeoxycholic acid in the colon bacteria modify these to produce secondary bile acids = deoxycholic acid and lithocholic acid. these are absorbed by terminal ileum and trasnported by portal vein to liver and resecreted by hepatocytes.

Answer 27

emulsification of fats and aid digestion - increase S.A absorption of fat soluble vitamins - ADEK elimination of cholesterol and bilirubin

Answer 28

not reabsorbed and recycled hepatocytes cant make enough bile so fat indegesiton and poor fat soluble vitamin absorptoon

Answer 29

when erythrocytes are digested by macrophages in the spleen they release haemoglobin broken down to haem and globin globin reused haem broken down to biliverdin which is converted to unconjugated bilirubin. unconjugated bilirubin binds to albumin taken up by liver and conjugated conjugated bilirubin excreted in bile conjugated bilirubin --> urobilinogen by intestinal bacteria. excreted and some reabsorbed and excreted in urine.

Answer 30

Jaundice is a condition characterized by the yellowing of the skin, mucous membranes, and the whites of the eyes (sclerae) due to elevated levels of bilirubin in the blood, a condition known as hyperbilirubinemia. pre hepatic = heamolysis (haemolytic anaemias - spherocytosis, autoimmune, ABO incompatibiltiy) hepatic = cirrhosis ,hepatitis, gilberts post hepatic = gall stones , tumours in general pre-hepatic - rise in unconjugated hepatic - both increase post hepatic - conjugated increases

Answer 31

unconjugated binds albumin in blood low albumin can result in increase of unconjugated bilirubin

Answer 32

the metabolic pathway of conversion of lactate back to glucose during aerobic conditions during anaerobic exercise, lactate can build up from glycolysis. (produced by lactate dehydrogenase). this also occurs in ischaemia or all the time by RBC (no nucleus) the lactate is transported to the liver in the blood and converted back to pyruvate and then glucose - for further glycolysis, glycogen storage or production of aa. certain lactate dehydrogenase isoenzymes can catalyse the reverse reaction

Answer 33

amino acid breakdown produces ammonia from amine group also nucleic acid metabolism urea cycle removes ammonia from blood urea cycle occurs in zone 1 of hepatocytes where ammonia is converted to urea for excretion in kidneys.

Answer 34

metabolic * glycogenesis * gluconeogeneiss * glycogenolysis * urea cycle * cori cycle drug detox * cyp 450 - phase 1 * phase 2 - conjugation * protects body from toxins ingested haematological * clotting factors * albumin immunological * acute phase proteins - CRP * kuppfer cells digestion * bile - fat sol vitamins

Answer 35

transaminase blood levels - suggests inflammation of liver e.g. ALT , AST synthetic function - clotting factors, INR , albumin levels indicators of biliary disease - bilirubin, ALP

Answer 36

glucose in blood macromolecules - glycogen, proteins, fats (break down and gluconeogenesis / B oxidation)

Answer 37

chemical processes that occur within cells encompassing anabolic and catabolic reactions. regulated by complex pathways and second messengers and enzymes 2 main pathways = catabolism (exothermic) and anabolism (endothermic)

Answer 38

the amount of energy used by an individual in times of rest to maintain basic physiological functions.. 12 hours after a meal, in normothermia usually around 70-100 cals/ hr varies depending on gender, age, muscle mass etc overall in women around 1500cals/day and 2000 in men.

Answer 39

patient - age, sex, muscle mass, ethnicity, pregnancy situation - stress, exercise, eating (reduced in starvation), temp pathological - hyperthyroidism/ hypothyroidism

Answer 40

0.5 - 1g/kg protein 5-10g/kg carbs 1-2g/kg fats around 100 cal/hr = 2400calories

Answer 41

glycolysis - ATP and pyruvate glucogenesis- production of glycogen gluconeogenesis - converted to aa

Answer 42

glycogen is phosphorylated to released glucose-P (glycogen phosphorylase, debranching enzyme) the reverse can also happen (glycogen synthase, branching enzyme) glucose 1P to glucose 6P to glucose enyzme pathways are regulated by a number of hormones - adrenaline, cortisol , glucagon, insulin

Answer 43

glycolysis - 10 steps - glucose to pyruvate. produces net 2 ATP, 2NADH and 2 pyruvate. pyruvate enters mitochondria LINK reaction - pyrvuvate to acetyl coA (pyruvate dehydrogenase) - CO2 and NADH produced krebs cycle * cycle of enzyme reactions * starting with citrate and ending with oxaloacetate * oxaloacetate combines with acetyl coA to madke citrate. * produces NADH, FADH ATP and CO2 oxidative phosphorylation * inner mitochondrial membrane and inner mito space * consists of series of electron transport carriers * NADH is oxidised and donates electron to the chain, e is transported down the chain, releasing energy to pump H+ ions across into IMS. * H+ builds up and flows down gradient via ATP synthase * O2 is final e acceptor and H+ --> H20 * regenerates NAD * produces 34 ATP in total 38 ATP

Answer 44

glycolysis produces pyruvate and 2 ATP and 2 NADH NADH needs to be regenerated for this pathway to continue pyruvate --> lactate (lactate dehydrogenase) replenishes NAD (oxidised)

Answer 45

glucose aminao acids - produce pyruvate and acetyl coA and enter krebs fats - B oxidation to produce acetyl coA

Answer 46

describes the production of glucose from other molecules. mostly occurs in liver but also kidneys. stimulated by glucagon, inhibited by insulin important as RBC and neurons only use glucose as substrate. mostly via pyruvate e.g. latate and glucogenic aa both produce pyruvate which can be converted back to glucose also via glycerol - can undergo reverse glycolysis allows fatty acids to produce glucose some aa and fatty acids cant produce glucose but can produce acetyl coA and enter krebs

Answer 47

ATP phosphocreatine NADH

Answer 48

starvation is defined as the failure to ingest sufficient calories to sustain normal body function during starvation - blood glucose needs to be maintained for RBC and brain this is via gluconeogenesis due ot fall in insulin, rise in glucagon slowly levels of FFA and ketones rise as fats are metabolised and ketosis takes place.. first 24 hrs = glycogen stores used. glucose drops iniitially, causes increase glucagon, drop in insulin. promotes glycogenolysis day 1 -4 = glycogen depleted, glucose levels stabilised. fat metabolism predominates. FFA and glycerol produced. FFA can be used by non-glucose dependant tissues. glycerol converted to glucose by gluconeogenesis. day 4 plus = FFA are converted to ketones (ketosis) brain adapts to use ketones

Answer 49

enteral route always prefered where possible however sometime TPN necessary * disorders requiring complete GIT rest - pancreatitis * post op feeding failed = more than 5 days e.g. ileus * malnourished and unable to eat = radiotherapy

Answer 50

solutions are prepared depending on requirements water 30-40ml/kg/day 30 kcal/kg/day 1g/ kg/ day protein - essential vitamins/minerals etc usualy more cals and protein due to hypercatabolic state in stress/ surgery requires central access

Answer 51

related to access = infection, thrombosis, bleeding related to TPN = volume overload electrolyte disturbances hyperglycaemia can cause derranged LFTs

Answer 52

severe metabolic and electrolyte disturbance following introduction of food too quickly after a prolonged period of starvation. during starvation, metabolic pathways alter. these require K+ and PO4 - these are driven out of cells and stores depleted once refeeding has begun, K+ and PO4 are driven into cells (low levels intracellularly) for glycogen and fat production (insulin driven) this reduces extracellular levels can result in hypokalaemia, hypophosphataemia and hypomagnesaemia arrhyhtmias, muscle weakness, confusion, seizures. need to feed slow and monitor electrolytes

Answer 53

catabolic process releasing the energy from glucose into smaller usable forms of energy ATP. consists of glycolysis, link, krebs, oxidative phosphorylation however also can be anaerobic (only glycolysis)

Answer 54

proteins hydrolysed to aa aa deaminated ammonia --> urea (urea cycle) the remainder of the aa can be converted to acetyl coA --> krebs cycle. or glucogenic aa can be converted back to glucose

Answer 55

insulin, adrenaline, somatostatin

Answer 56

no, not enough smooth muscle blood flow is directly related to portal pressure.

Answer 57

inspiration - negative thoracic pressure , increases CO and heptaic blood flow expiration - the opposite in PPV - positive pressure will reduce blood flow. PEEP reduces it further.

Answer 58

hepatocytes kuppfer sinusoidal biliary epithelium

Answer 59

occurs when there is poor o2 supply to zone 3 results in hypoxic injury to hepatocytes, poor drug detoxification so toxicity can develop caused by hypoperfusion - hypotension, haemorrhage, sepsis drug toxicity - halothane and paracetamol and alcohol

Answer 60

perfusion pressrue = MAP - hepatic pressure MAP = CO x SVR low SVR due to drugs, hypovolvaemia, haemorrhage low CO - PEEP/ IPPV, drugs hepatic pressure - surgical pressure

Answer 61

chronic liver inflammation can result in scarring - cirrhosis. small fibrotic liver with poor function caused by viral hepatitis, alcohol, wilsons, autoimmune hepatitis results in * poor synthetic function (low albumin, clotting), * poor metabolic function (poor fat absorption, risk of hypoglycaemia), * poor drug detox * increased resistance to blood flow and portal hypertension

Answer 62

more than 12mmHg ascites - high venous hydrostatic pressure splenomegaly varices

Answer 63

stimulus - Ach from vagus nerve, presence of peptides roles = acid secretion, motility, stimulates pepsinogen release

Answer 64

as HCL secreted to lumen, HCO3 is reabsorbed into blood

Answer 65

starts at 20min complete 3 to 4 hours depends on what is eaten and external factors

Answer 66

2 hour clear fluids 6 hours food / non clear paeds 1 hour clear fluids 6 hours food 4 hours breast milk

Answer 67

syndrome associated with gastric surgery loss of stomach means suddenly food dumped into intestine pain, bloating, hyperglycaemia

Answer 68

can be used to USS stomach to estimate contents to estimate risk of aspiration. stomach USS when patient in right lateral position can be useful if limiting starvation period is necessary paediatrics, emergency theatre or gastric emptying is slowed - trauma, diabetic neuropathy, opioid us less than 1.5ml/kg in stomach is associated with low risk of aspiration

Answer 69

following fasting guidelines RSI other prokinetics antacids reduce opioid use gastric USS

Answer 70

drug metabolism slowed potential coagulopathy risk of worsening hepatitis psot op - hepatic encephalopathy avoid hepatotoxic drugs and those that use minimal liver metabolism