Alimentary Ch5 PDF - Liver, Pancreas, Metabolism & Ruminant Digestion

5.1 Liver & Pancreas (DL) Liver ​ Function: storage, metabolism, bile synthesis ​ Receive: ○​ Nutrient-rich deoxygenated blood: from gut ○​ Oxygenated blood: from hepatic artery ○​ Branch → supply every hepatocyte ​ External lobation...

5.1 Liver & Pancreas (DL) Liver ​ Function: storage, metabolism, bile synthesis ​ Receive: ○​ Nutrient-rich deoxygenated blood: from gut ○​ Oxygenated blood: from hepatic artery ○​ Branch → supply every hepatocyte ​ External lobation ○​ Converge → drain back to caudal vena cava ​ Arrangement: ○​ Blood supply, bile canaliculi: easy exchange ​ Bile: gh canaliculi, → portal triad ○​ Lobule: accumulation of hepatocyte & vessel ​ Mockled appearance of liver Sinusoid: ​ Specialised, fenestrated, leaky capillary ​ Between line of hepatocytes ​ Easy diffusion between hepatocyte & blood ​ Blood flow: portal triad → central vein ○​ Merge w/ portal vein ○​ → Caudal vena cava → heart Portal triad: ​ Artery: thick wall, round ​ Vein: thin wall, irregularly shaped ​ Bile duct: ○​ Simple columnar epithelium ○​ + water → modify bile Hepatocyte: ​ Smooth ER: cholesterol → bile acid ○​ Detergent property: hydrophilic + hydrophobic region ○​ Take phospholipid & cholesterol from cell membrane  ○​ Bile salt: attach to Na ​ Draw water: duct wall cell → bile ​ Drug & toxin: excrete through liver ○​ Bilirubin: pigment (non-functional) ​ RBC turnover ​ Green colour ​ Lv: test liver function Gall bladder: ​ Store & concentrate bile ​ Simple columnar epithelium ​ Glandular Pancreas ​ Endocrine: hormone ○​ Islets of Langerhans ​ ~ Island w/in sea of acini ○​ Alpha cell: glucagon  ​ Glycogenolysis ○​ Beta cell: insulin ​ Glycogenesis ○​ Delta: somatostatin ​ Growth inhibiting ​ Decrease HCl production → slow down digestion process ○​ PP: pancreatic polypeptide ​ Exocrine: enzyme Pancreatic duct: ​ Stratified cuboidal epithelium ○​ Protective + secretory ​ Merge exocrine secretion into main pancreatic duct ​ Open @ major duodenal papilla ○​ Duct of Santorini: major duodenal papilla ​ Both dog & cat ○​ Duct of Wirsung: minor duodenal papilla ​ Dog, X cat 5.2 Regulating & Integrating Metabolism Enzyme: Blood glucose lv: ​ Normal: 4.5-5.5 mM ​ Higher: ○​ After CHO meal: ~ 7 mM ○​ Diabetes: 10-12 mM  ​ Lower: ○​ Starvation: 3-4 mM ○​ Ruminant: 2-3 mM ​ Parasympathetic nervous system ​ → Insulin: ○​ After meal → decrease blood glucose lv ○​ Stimulate storage & use of fuel ​ Glycogen deposition in muscle & liver ​ Glycolysis in liver → produce substrate for fatty acid synthesis ​ Increase protein synthesis (esp. muscle): excess amino acid → metabolic intermediate ○​ Indicate fed state ​ → Glucagon: ○​ Fasting → increase blood glucose lv ○​ Main target organ: liver ○​ Release stored fuel ​ Glycogenolysis, gluconeogenesis in liver → glucose enter blood ​ Hormone-sensitive lipase in adipose tissue: CHO → fat (metabolism) Regulation of glucose uptake: ​ Transporter: 1-5 ○​ Diff. glucose conc. ○​ Express in diff. tissue ​ GLUT 1 & 3: ○​ All cells ○​ Km (conc. of substrate during half max. transport rate): ~ 1-5 mM ​ Basal slow uptake ​ GLUT 2: ○​ Pancreatic beta cell (insulin), hepatocyte ○​ Km: ~ 15-20 mM ​ High conc. ​ Hyperglycaemic → uptake ​ GLUT 4: ○​ Muscle, adipocyte ○​ Active when insulin is present ○​ Km: ~ 5 mM ​ Internalise w/in cell in vesicle ​ Insulin → vesicle fuse w/ plasma membrane → rapid glucose uptake ○​ Cycling: ​ GLUT 2: glucose uptake into beta cell & hepatocyte ​ Insulin release ​ Expression on muscle & fat cells ​ Rapid glucose uptake ​ Storage (glycogen & glycerol) / glycolysis (synthesise fatty acid)  ​ GLUT 5: ○​ Small intestine ○​ Absorption Ketogenesis: ​ Hepatocyte only (required enzyme) ​ Fat & carb breakdown → acetyl CoA enter Krebs cycle ○​ Fast: fat breakdown predominate → accumulation of acetyl CoA ​ Increase production: mobilised fatty acid → beta oxidation ​ Decrease usage: increased energy charge (ATP from beta oxidation), gluconeogenesis → deplete intermediate of Krebs cycle (inhibit) ○​ → Ketone body ​ 4-C: 3-hydroxybutyrate, acetoacetate ​ 3-C: acetone ​ Ketone body usage: ○​ Fatty acid X cross barrier ○​ Krebs cycle: convert back into acetyl CoA ○​ Fasting response: produce energy > glucose ​ RBC: glycolysis ​ Maintain blood glucose lv ○​ Fuel brain ​ Excessive production → ketoacidosis ○​ Decrease pH, poisonous ○​ Severe metabolic disease: ​ Ruminant production disease ​ Severe diabetes ​ Starvation ○​ Test: urine Muscle metabolism: ​ Store glucose ​ Resting: gluconeogenesis (fatty acid) ​ Insulin / adrenaline (sympathetic, increase blood glucose lv) 5.3 Pathogenesis of Metabolic Disturbances Diabetes: Lipidosis: fatty degeneration ​ Liver taking lots of fat ​ Cause: ○​ Increase fatty acid uptake → increase blood lv ​ Starvation: increase mobilisation of part of fat, others stored as neutral fat ​ Overeating: energy intake > expenditure, temporarily stored before movement to body ​ Metabolic diseases: alternate pathway for energy production, ketogenesis (chronic diabetes, ruminant production disease: -ve energy balance, gluconeogenesis) ○​ Decrease fatty acid use ​ Hypoxia (X O2) ​ Toxin: pregnancy toxaemia (sheep: twin lambs), acetonemia (high yield diary cow, shortly after parturition) ​ Appearance: ○​ Liver: ​ Increase in size ​ Colour: tan, yellowish ​ Slight pressure → rupture ○​ Kidney cortex: paler ​ Cat: fatty kidneys (normal) ○​ Heart: ​ Flabby ​ Papillary muscle: w/ streak → X pump properly ​ Microscopic: ○​ Fat compromise function: ​ Reduce space, blood flow ○​ Liver & kidney:  ​ Fat globule / vacuole (size: vary) ​ Nucleus: push to periphery Glycogen infiltration: ​ Moderate amount: X alternation ​ Microscopic: foamy cytoplasmic vacuole ​ In-born error: ○​ Inherited defect of key metabolic enzyme ○​ Domestic species (very rare) ○​ W/ excess glycogen accumulation (storage disease) ○​ → Phosphorylase: ​ X break down glycogen ​ Can carry out gluconeogenesis ○​ → Glucose 6-phosphatase: ​ More serious ​ X produce glucose → severe fasting hypoglycaemia ​ Only in liver: site of required enzyme ○​ → Muscle isoform of PFK (phosphofructokinase), pyruvate kinase: ​ Glucose 6-P → pyruvate ​ Clinical sign: aerobic exercise intolerance (high intensity, long walk) / 5.4 Ruminant & Monogastric GIT Point-to-Point 5.5 Ruminant Digestion & Metabolism Herbivore fermentation: ​ Microorganism ​ Digest cellulose & other plant carb ​ Foregut / hindgut ​ Slow food passage (compare w/ enzymatic digestion): fibre ​ Constant environment ○​ Continuous food intake & outflow: acidity ○​ pH regulation: HCO3- in saliva Cellulose digestion in rumen: 3 phases (glycolysis) ​ Extracellular microbial enzyme: ○​ Complex → simple sugar ​ Intracellular microbial enzyme: ○​ Simple sugar → pyruvate ○​ → Volatile fatty acid: ​ Acetate: 60-70 % (4-C, make 2 acetyl CoA, increase w/ roughage) ​ Propionate: 15-20 % (3-C, gluconeogenesis → make oxaloacetate, increase w/ concentrate) ​ Butyrate: 10-15 % (4-C, make 2 acetyl CoA) ​ → Form long chain for storage ​ → Much lower blood glucose lv ○​ → Gas (eg. CO2, CH4) ​ Cow: ≤ 30 L / hr ​ Bovaer: feed additive, reduce CH4 emission Intensive Extensive ​ Increase glucose lv in milk: oxaloacetate production ○​ Make more propionate ○​ Ruminant bypass protein ​ Heated soybean (60°) ​ → Gluconeogenesis substrate Metabolic profile: ​ Ketosis ○​ Primary: food basis ○​ Secondary: individual based  ​ X Ca ​ Lame ​ Uterine infection ​ Displaced abomasum ​ Ruminant acidosis ○​ SARA ○​ pH drops in rumen → upset microbes ○​ Defect integrity of rumen wall ​ Pregnancy toxaemia ○​ = Twin lamb disease Protein digestion in rumen: ​ Incorporated into microbe ○​ Microbe: X proteinaceous nitrogen compound (eg. urea) → manufacture amino acid ​ Broken down @ rest of GIT, amino acid absorbed into body ​ Make own essential amino acid → thrive on low / poor quality protein diet ​ Manufacture vitamin → absorbed in small intestine ​ X deal w/ high production demand of glucose ​ Can feed urea ​ Deamination → VFA & NH3 production ○​ Rumen microflora: use NH3 to make new amino acid ​ Part of microbial protein ​ → Some: pass through rumen, digest in abomasum & small intestine N-based digestion & metabolism (N cycling): Foregut / hindgut fermenter: ​ Foregut: ○​ Material: rumen → abomasum ​ Monogastric stomach ○​ → Intestine ○​ Slurry, protein-rich broth → extra vitamin ​ Hindgut: ○​ Fermentation occur after ‘conventional’ GIT  ○​ Little digestion of fermentation product ​ Eg. rabbit: post-fermentation ingestion ○​ Product: ​ VFA (absorb in colon) ​ Microbial protein ​ Vitamin ○​ → Need higher quality diet High producing ‘intensive’: high quality diet ​ Provide protein ○​ Energy ○​ Fermentation: microbial growth substrate ○​ Bypass protein 5.6 Energy Imbalance & Herd Health Rumen function: ​ Cycle: Primary: mixing Secondary: eructation ​ Dorsal & ventral sac of rumen + ​ Only rumen reticulum ​ Produce gas: CH4, CO2, N3 ○​ 1 L / min ​ Bolus: pass up oesophagus → remastication ○​ ‘Chewing of cud’: sign of good health ​ Help digestion ○​ Saliva production: 100-150 L / day ○​ HCO3-: 3.5 kg ​ Buffer pH for rumen Bloat (ruminal tympany): ​ Excess of gas → abnormally enlarged rumen, X eruct (cardiac sphincter → oesophagus) ○​ Distension ○​ LHS enlarged (X symmetrical) ​ Severe: whole abdomen ○​ Compress lungs & heart → respiratory distress → death ​ @ Left paralumbar fossa ​ Symptom: recumbent ○​ Unable to stand, lie down on its side / chest ○​ Rumen expand ​ 2 types: Free gas bloat Frothy bloat ​ @ Rumen ​ Gas from stable foam ​ Gas production: 1 L / min ​ Small bubble: X coalesce (merge) ​ Fluid blockage → X ​ X eructation eructation  Cause ​ Physical obstruction to ​ Pasture / leguminous bloat oesophagus ○​ Legume 豆科植物 in forage: ○​ Hard food type contain soluble protein ○​ Choke ○​ Eg. lush pasture (grazing ​ Rumen / reticulum: X motility area, green & healthy grass), ○​ Tetanus clover ○​ Hypocalcaemia ​ Grain overload / feedlot bloat ○​ Rumen acidosis (X ○​ High lv: too much carb feed properly) ○​ Finely ground: large surface ○​ Vagus nerve (CN 10) area damage / indigestion ○​ → Rumen acidosis ​ Grain overload Treatment ​ Stomach tube: release gas ​ Anti-foaming agent ○​ Mouth X close (bite) ○​ Reduce surface tension ​ Trocar & cannula: pass into ○​ Gas bubble coalesce rumen, via left paralumbar ○​ Normal eructation (sublumbar) fossa ​ Synthetic surfactant ○​ Red devil: take cap ○​ Poloxalene (Bloat Guard) off → perforate → ○​ Simethicone (Birp) screw & hold in place ​ Oil → pull out ○​ Liquid paraffin / mineral oil ○​ Cooking oil: corn, maize ​ Prevention: ○​ Pasture management ○​ X finely ground cereal ○​ ≥ 40 % forage Hypocalcaemia: ​ = Milk fever ​ → Sedation (state of sleepiness), mastitis, injury ​ Solution: sit cow up → stand cow up ○​ Eructate, improve rapidly Actinomyces bovis: ​ Rod-shaped bacterium ​ → Lumpy jaw ​ Rare Abomasum: ​ Left (/ right) displaced abomasum ​ Torsion (RHS) ○​ Very serious: cut off blood supply → Displaced abomasum: ​ Cause: ○​ Decreased feed intake ​ Energy deficiency: lose weight rapidly ​ Rise of blood ketone lv (sweet smell) ​ Ketosis ○​ Vicious cycle: feel unwell → eat even less ​ Diagnosis (LDA): ○​ Flick finger → metallic ‘ping’ ○​ Tinkle ​ Find source → put stethoscope ​ Watery sound → Ketosis: ​ Build up of ketone body in blood ​ Cause: -ve energy balance, fat loss ○​ Produce ketone ​ Diagnosis: blood / urine test ○​ Beta-hydroxybutyrate (ketone) ○​ Make cow urinate: push hand in vulva → move up & down ​ Primary: ○​ X underlying disease ○​ Glucose X meet energy demand ​ Esp. high-producing dairy cattle (during early lactation, poor nutrition) ○​ -ve energy balance, excessive break down of fat ○​ Solution: nutritious diet ​ Secondary: ○​ Cause: another (primary) disease → unwell, reduce appetite ​ LDA / RDA ​ Metritis (uterus inflammation), mastitis ​ Traumatic reticulitis (= hardware disease) ​ → Fatty liver: ○​ Excessive weight loss → fat deposit ○​ Fat cow syndrome: extreme ​ Completely full of fat ​ Liver failure ​ → Pregnancy toxaemia (sheep, beef cattle) ​ → Twin lamb disease (sheep) 5.7 Ruminant Abdomen Case study ​ 4 y/o, Holstein fresian (dairy cattle) ​ Yield: 35 L (normal) → 8 L ​ Lethargic, inappetant ​ Calving: 10 days ago ○​ Live calf, normal parturition Clinical exam: ​ Respiratory rate: watch rise & fall of flank ​ Pain response: ○​ Bruxism (teeth grinding) ○​ Stand w/ hindlegs underneath: guard abdomen ​ BCS, abdomen shape ​ Logical manner: tail → LHS → head → RHS ○​ From ventral aspect Clinical finding: ​ Heart & lungs: normal ​ Last rib: ‘sprung’ ​ Rumen movement: audible (caudal) ​ LHS abdomen auscultation: ○​ Resonant ‘ping’ ​ Fluid-gas interface ​ Stethoscope over skin, flick abdominal wall ​ Potential cause: displaced abomasum, caecal volvulus ○​ Ballottement (fluid splashing sound) ​ Rectum: firm dry faeces Potential diagnosis (ruled out): Retained foetal membrane Metritis Mastitis Ruminal atony Vaginal exam Udder exam Normal rumen sound Normal temp.  Caecal dilation (w/ volvulus) RDA Ketosis Peritonitis RHS X ‘ping’ X primary issue ‘Ping’ & tinkle @ LHS → Abomasal displacement: ​ Dairy herd: economic loss ○​ Treatment cost ○​ Premature culling ○​ Production loss ​ Peak period: 3-4 weeks after calving ​ Cause: ○​ Calving ​ Pregnancy: uterus displace abomasum ​ After calving: abomasum move back to normal position → increase risk ​ Reduced fill (lower food consumption) → greater movement ○​ Atony (loss of contraction) ​ X contraction, turn over content (eg. disease) ​ Gas accumulation, abomasum move up abdomen ​ Diagnosis: ○​ Blood, milk, urine test ○​ Abdomen auscultation (LHS & RHS) ​ Prevent: good management ○​ Esp. weeks before & after parturition ​ Left (LDA): ○​ 80-90 % ​ 90 %: 1st 4 weeks after calving (off feed, depressed → reduced milk production) ○​ Move to LHS of normal position ○​ Trapped between rumen & left abdominal wall → stretching ○​ Constriction of entrance & exit of abomasum → fill w/ gas ​ Right (RDA): ○​ More serious condition, lower recovery rate ○​ Move up right abdominal wall ○​ Trapped above omasum ○​ Constriction of entrance & exit of abomasum → fill w/ gas & fluid ​ → Abdomen pain, elevate heart rate, colic sign, scant (little) faeces, diarrhoea ​ More severe: twist → torsion ​ → Severe shock (cold extremity), extreme dullness Abomasum: 4th, ‘true’ stomach ​ Location: near abdominal cavity floor, RHS ○​ Below omasum ○​ Rumen: above abomasum ○​ Reticulum: LHS of abomasum Treatment: Toggling & rolling ​ Conservative ​ Manipulate abomasum → return to normal position ​ 50 % relapse: require surgery ​ Toggle: ○​ Lie on back: pass through skin, into abomasum ○​ Anchor abomasum in correct position (depend on abomasum ‘floating’ back) ○​ Reduce relapse rate Surgery: ​ Suture, attach to abdominal wall ​ Technique: depend on animal condition ​ → Omentopexy: greater omentum ​ → Pyloropexy: pyloric antrum ○​ Lower ⅓ part of stomach ○​ Junction of pylorus & duodenum ​ Reduce recurrence risk ​ Allow assessment of abomasum condition ​ Fluid therapy 皮下水 ​ Post-management: ○​ Good quality forage ○​ X concentrate feeding Prevention: nutrition 5.8 Avian & Exotics GIT Avian Pregastric system: ​ X teeth, beak covering jaw (diff. form) ○​ X masticate ○​ Mechanical disruption of food ​ Oesophagus: ○​ Large diameter (esp. w/ large meal) ○​ Swallowing: oesophageal peristalsis ​ Neck extension: help ​ Crop (present in most species): ○​ Expansion of ventral wall of oesophagus, @ thoracic inlet ○​ Muscular pouch, store food before digestion ​ Stomach: full ​ Perch on safe spot → start digestion (parasympathetic) ○​ Bulge to RHS, lie against breast muscle ○​ Vary: simple expansion → 1 pouch → 2 ○​ Contraction state of stomach → food divert into crop (later propel into stomach by peristalsis waves) Stomach: Proventriculus: ​ Glandular ​ Receive food from oesophagus ​ Secrete mucus, HCl, pepsinogen (~ mammalian stomach) Gizzard 胗: ​ Non-glandular, muscular ​ Shape: disk  ​ 2 orifice: ○​ Receive ingesta from glandular stomach ○​ Empty into duodenum ​ Mechanical disruption of food ○​ Contain small stone (grit): facilitate grinding ​ Contraction: feed go back & forth ○​ Between proventriculus & gizzard ○​ Grind food, increase exposure to digestive enzyme ​ → Periodic retropulsion ○​ Backward movement of food: pylorus → stomach ○​ Facilitate ingesta & enzyme mixing ​ Regurgitation: ○​ Bone pellet, hair, feather ○​ Raptor (bird of prey) Small intestine: ​ ~ Mammal ○​ Absorptive epithelial cell: same enzyme & transporter ​ Duodenum, jejunum, ileum ○​ Less histologically distinct ​ Proximal: receive bile (liver), digestive enzyme (pancreas) Large intestine: ​ Short colon ○​ Short villi: extend into lumen ​ 1 pair of caeca (caecum) ○​ Dispensable (→ can remove w/ X harm) / fermentation (absorb VFA) ​ Cloaca: ○​ Expanded, tubular ○​ Common opening: digestive, reproductive, urinary system ○​ → Vent: outside of bird ○​ Antiperistalsis: ​ Assist caeca filling ​ Water absorption: urine transport (cloaca → large gut) Goose: Mesogastric viscera Proventriculus & gizzard  Crop GIT Exotics Snake anatomy: System Structure Detail Endocrine Thymus ​ Thin ​ Top of trachea Parathyroid ​ Near thymus Thyroid ​ Cranial to heart ​ Control ecdysis: shedding of outer layer Adrenals ​ Close to testes / ovaries Cardiac Heart ​ Cranioventral to end of trachea ​ Mobile: eat → displace ​ 2 atria, 1 common ventricle Aorta ​ Paired: fuse into 1 abdominal aorta ​ Both exit heart from ventricle Vena cava ​ Sinus venosus (chamber before atria): narrow tube ​ Lead up to right atrium Respiratory Trachea ​ Supported by C-shaped cartilage Lung ​ Vary: species ○​ 2 / reduced into 1 (X left) ​ X diaphragm Air sac ​ Caudal ⅓ ​ X respiratory Digestive Oesophagus ​ Distend greatly: allow passage of large prey  Liver ​ Elongated ​ Extend: mid-point of lung → caudal stomach Stomach ​ Shape: tubular ​ Gland: secrete HCl & peptin (pepsin) ​ Digestion Gall bladder ​ Caudal to liver Pancreas ​ Form splenopancreas ​ Adjacent to gall bladder Spleen Small intestine ​ Poorly defined ○​ Duodenum, jejunum, ileum ​ Linear ​ Boidae: caecum @ junction of small & large intestine Urinary Kidneys ​ Paired ​ Attach to dorsal body wall ​ Right: cranial, left: caudal ​ Caudal (male): involved in reproduction ○​ Breeding period: enlarged ​ Nephron: X loop of Henle Ureter ​ X urinary bladder ​ 1 ureter leave each kidney, empty into urodeum of cloaca Reproductive Testes / ovaries ​ Testes: ○​ Cranial to kidneys ○​ Right: cranial, left: caudal ​ Ovaries: ○​ Middle of coelomic cavity ​ Breeding period: increase in size Hemipenes ​ Intromittent (male) ​ Base of tail ​ Probe: insert towards tail ○​ Depth: > 6 scales from cloaca ○​ Female: X hemipenes → < 6 scales Cloaca ​ Common exit of GIT & urogenital tract ​ Faeces: mix w/ urate / pass separately ​ Male: paired hemipenes lie inverted in cloaca ○​ X urination Chelonian (tortoise): Sea turtle: Big reptile: crocodilian Alligator Crocodile Caiman ​ Webbed feet ​ Separated toes ​ Size: small → medium ​ Chunky face ​ Pointy face ​ Compare w/ alligator: ​ X sweat gland → release longer & sharper teeth, heat through mouth agility Dolphin: Shark: stomach Hippopotamus: stomach Simian (gibbon): caecum 5.9 Equine Abdomen Common disease of caecum: 1.​ Caecal tympany: ○​ Gas accumulation → dilation 2.​ Caecal impaction ○​ Fluid filled ​ Functional failure: emptying ○​ Solid filled ​ Impaction of dehydrated ingesta 3.​ Caecal intussusception: ○​ Fold into adjacent part of intestine ○​ Apex invaginate into caecal body, enter large intestine Caecum & colon: Colic: ​ Any form of abdominal pain ​ Cause: vary ○​ Mainly: gastrointestinal ○​ Urinary, reproductive system  ○​ Severe respiratory disease ​ Sign: ○​ Paw @ ground ○​ Watch flank ○​ Kick, bite belly ○​ Repeat: lie down, curl back of upper lip ○​ Roll, dog sit, lie on back ○​ Head: unusual position ○​ Sweat ○​ Stretch out as if to urinate ○​ Depression, inappetence Emergency condition: ​ Nephrosplenic ligament entrap large colon ​ Spleen: engorged w/ blood 充血