Flashcards
GI
Cards in this deck (70)
- 1What part of the horse is modified into fermentation chamber?Ascending colon (large colon)
- 2What are taenial bands?Longitudinal muscle not continuous strand but arranged into taenial bands (taenia)
• Different number of taeniae in different parts
• Shorter than large intestine itself resulting in sacculations (haustra) • Enable mixing and delays transit time to allow fermentation - 3Degree off fermentation n large colon in different species?• Degree of fermentation depends on material reaching large intestine
• In carnivores most digestion / absorption has already occurred prior to large intestine therefore fermentation minimal
• In ruminants / omnivores fermentation moderate
• In horses vast majority of non-hydrolysable CHO reaches large intestine so
fermentation extensive - 4What are the products of fermentation in the large intestine and what happens to them?• Microbial products of fermentation are VFAs / CH4 / CO2
• Large intestinal mucosa can absorb these VFAs
• Gases passed to rectum by peristalsis and expelled (flatulence) - 5What is wasted due to hind gut fermentation?• As large intestine is terminal part of GI tract some VFAs AND ALL microbial protein egested / wasted
• Rabbits / rats practice coprophagy to avoid this waste - 6What are the different volatile fatty acids and how does a horse use them?• Acetate
• Used in liver
• Oxidised in most other cells to generate ATP • Major source of acetyl CoA for lipid synthesis
• Propionate
• Substrate for gluconeogenesis
• Butyrate
• Energy production
• Cellular homeostasis - 7How is sodium, chlorine, water and VFA's absorbed in a horse? (in the hind gut)• VFAs (acetate, propionate, butyrate)
• Absorbed by SCFA / HCO3- exchanger
• Na+
• Absorbed by sodium channels & Na+/H+ exchanger (NHE transporter) • Sodium absorption enhanced by aldosterone
• Cl-
• Absorbed by bicarbonate / hydroxyl exchange
• Water
• Most of rest of water passing from SI absorbed in large intestine
• Osmotic pressure
• Hydrostatic pressure • Solvent drag
• Extensive re-absorption in horses - 8What is the difference in how hCHO is felt with comparing horses and ruminants?• Fermentation similar process to that occurring in ruminant fore- stomach
• EXCEPT small intestine occurs before fermentation vessel • In ruminants any hCHO immediately fermented so none
passes into SI
• However in horse potentially lots of hCHO can pass into LI if overload of SI capacity to digest / absorb it - 9In horses how do they deal with the decreasing pH due to the increasing volume of VFA's?• VFAs cause a decline in pH of luminal contents
• Neutralised by copious pancreatic secretion containing HCO3- • Goblet cells in large intestine secrete mucous & HCO3-
• Ileum also secretes HCO3-
• If production of VFAs excessive H+ ions too numerous to be neutralised by HCO3- secretions
• pH of luminal contents declines
• Favours multiplication of acid resistant microbes (amylolytic bacteria /
lactate producers)
• Lactic acid poorly absorbed cf VFAs causing further pH decline - 10What is the difference between ruminant and horse protein fermentation?• Probably similar to ruminants
• HOWEVER
• Equine hind-gut more capable of absorbing amino acids / peptides
• Hence less amino acids / peptides taken up by microbes, more being absorbed by the host
• This is a good thing as microbial protein is lost in faeces in hind-gut fermenters
• Microbial nitrogen requirements satisfied by urea secreted by ileum / large intestine
• Broken down by microbial urease into NH3 to be used as NPN source for microbial protein synthesis - 11How do horses absorb water?• Compared to other species more water reabsorption occurs in large intestine
• At luminal pH (6.5) most VFAs in ionic form which are poorly absorbed
• Local mechanism of secretion of H+ in exchange for Na+ converts ions to their respective acids thus enhancing their absorption
• HCO3- secreted in exchange for Cl- maintain pH at level suitable for fermentation
• Consequently when VFAs absorbed there is also a net absorption of NaCl which enhance water reabsorption via osmotic pressure & solvent drag - 12What are the advantages and disadvantages of hid-gut compared to fore-gut fermentation?• Hind-gut fermentation 70% as efficient as fore-gut fermentation • Microbes less efficient
• Lower degree of amylolytic fermentation
• Hind-gut fermenters lose microbial protein in faeces
• Coprophagy - rabbits / rodents eat certain component of their faeces high in microbial protein
• HOWEVER gut-transit time in fore-gut fermenters dependent on rate of fermentation and can’t be reduced whatever the nutrient quality of the fibre
• Horses on poor quality forage can decrease gut transit time and therefore consume more
• Ruminants more efficient on good quality forage
• Horses more efficient on poor quality forage as long as it’s in abundance - 13What is large intestine transit time?• Hind-gut fermenters - several days
• Fore-gut fermenters - 24 hours - 14Name the attachments from the liver to the diaphragm?Coronary ligament and left & right triangular ligaments.
- 15What structure runs in the falciform ligament and what would have this been in the foetus?Round ligament of the liver. This is the foetal remnant of the umbilical vein.
- 16How doe the the gall bladder empty its content and where do its contents go?Duodenum
Cystic duct drains into common bile duct that empties it secretions at the major
duodenal papilla. - 17What are the three branches off the ventral midline off the abdominal aorta?Celiac, cranial mesenteric and caudal mesenteric arteries.
- 18Name the three anatomical regions of the stomach and what is the embryological derivations of these regions?Fundus, corpus and pylorus.
In the dog, fundus and corpus from the fundic region and pylorus from the pyloric
region. - 19how many flexures do the duodenum contain?3 sigmoid flexure, cranial duodenal flexure and caudal duodenal flexure
- 20What domestic species is at biggest risk to peritonitis and why?Horse.
Greater omentum is minimal. - 21In ruminant fermentation what bacteria are present and what do they do?Amylolytic-hCHO
cellulolytic-non h-CHO
Proteolytic-protein
methanogenic-convert CO2 to CH4 to regenerate NAD+
Facultative anaerobes-remove 02 to maintain anaerobic environment - 22How are the products of fermentation absorbed by the ruminant?diffuse across rumen-reticulum epithelia
main site of absorption is papillae bottom of caudo-dorsal blind sac and ventral sac
VFAs in the rumen are in their dissociated form -pressumed that they are converted to un-dissociated form as they pass through the epithelia.
Metabolised as they are absorbed - 23How are the end products of fermentation used by the host? (ruminant)All used to generate ATP
Acetate is used to generate Acetyl CoA for lipid synthesis
Propionate used for a precursor in gluconeogenesis
Butyrate required to maintain healthy cellular homeostasis - 24Describe how the ruminant digests and absorbs protein?Main source of protein is microbial protein.
Digested and absorbed int eh abomasum and small intestine. - 25Describe the digestion of starch in a pig?starch=hCHO
glucose joined by an alpha-glycosidic bonds
broken down by salivary amylase into disaccharides
starch digestion counties with pancreatic amylase in the duodenum
disaccharide broken down to monosaccharides by brush border disaccharidases
salivary amylase eventually destroyed by stomach acid - 26how is the pigs stomach adapted for starch digestion?enlarged funds with no acid secretion
salivary amylase can continue working before it is destroyed by stomach acid
funds derived from cardiac region so only recreated mucus
Gradual increase in pH from luminal wall to centre of stomach
newly swallowed food pushed to centre of stomach - 27How are carbohydrates absorbed in the pig?in small intestine
absorbed as monosaccharides
transporter protein=SGLT
Specifically SGLT1 transports glucose and galactose
Fructose by GLUT5
All monosaccharides transported into blood via GLUT2 - 28Which phases of digestion do he carbohydrate enzymes operate in?Luminal phase-amylase
membranous phase-disaccharideases - 29How does starch digestion differs in carnivores compared to omnivores?NO salivary amylase
starch digestion performed by pancreatic amylase in duodenum - 30What is swallowing called?Deglutition
- 31Describe the process of swallowing?Food molded into bolus by tongue and moved upwards and
backwards to pharynx
• Under voluntary control
• Forces soft palette up to seal off nasal cavity
• Pressure-sensitive sensory cells stimulated
• Swallowing centre in medulla initiates swallowing reflex • Under involuntary control
• Epiglottis closes off trachea
• Upper oesophageal sphincter closes behind food bolus (epiglottis opens to allow respiration)
• Complicated peristaltic contractions force food down oesophagus
• Animals can swallow upwards
• Lower oesophageal sphincter opens to allow passage of food into stomach - 32Name some swallowing disorders?• Failure of soft palette to close off nasal cavity • Failure of epiglottis to close off trachea
• Pharyngeal paralysis
• Nerve / muscle injury • Botulism
• Clostridial toxins block acetylcholine release • Myaestheania gravis
• Antibodies formed against acetylcholine receptors • Anaesthesia
• Many anaesthetic agents induce vomiting • Swallowing process impaired
• Inhalational pneumonia - 33What is the innervation of the oesophagus?• Sympathetic
• via cervical sympathetic chain
• Parasympathetic
• SVE/AA via recurrent laryngeal (cranial division of XI) to
cranial cervical oesophagus
• AE/AA via vagus (X) to caudal cervical / thoracic oesophagus
• Species with striated muscle in caudal oesophagus still innervated by parasympathetic - 34what is the lower oesophageal sphincter?• = Cardiac sphincter
• Physiological sphincter rather than anatomical
• Except in horses
• Always closed except during swallowing
• Oesophagus enters abdomen at oblique angle
• Higher pressure in abdomen cf thorax causes stomach
to exert pressure on diaphragm thus re-inforcing closure • Prevents regurgitation of acidic stomach contents - 35Describe the process of vomiting and what is the other name for it?emesis
• Active propulsion of stomach contents into oral cavity
• Deep inspiration with simultaneous closure of trachea / nasal cavity
• Increases intra-abdominal pressure via diaphragm
• Forceful contraction of abdominal muscles (NOT gastric muscle) • Cardiac sphincter opens
• Food propelled up oesophagus
• Upper oesophageal sphincter opens
• Controlled by vomiting centre in medulla
• Stimulated by phyaryngeal / gastric distension or
irritation
• Normal in dogs / cats to expel bones / hair • Ruminants prefer to regurgitate
• Horses (& rats)
• Very well developed cardiac sphincter
• Exaggerated oblique entry through diaphragm
• Stomach usually ruptures before vomiting occurs - 36Explain gastric torsion?• Occurs in horses and dogs with wide chests
• Stomach rotates 90-360 ̊
• Seals off cardiac sphincter thus preventing vomiting
• Stomach distends further with gas
• If rotation compromises blood supply gastric tissue becomes oedematous / hypoxic and in severe cases necrotic
• Stomach dilatation can impair venous return to heart via caudal vena cava resulting in circulatory shock
• EXTREME EMERGENCY requiring surgical intervention - 37what are the functions of the stomach?• Digestion
• Continuation of starch digestion
• Initiation of protein digestion • Protection
• Stomach acid kills bacteria ingested with food • Storage
• Ensures food delivered to small intestine (main site of digestion / absorption) at controlled rate
• Mechanical breakdown / mixing
• Breaks down food and mixes with gastric juice forming a semi-
liquid chyme - 38What are the anatomical regions of the stomach?• Cardia
• = entrance to stomach • Physiological valve
• Fundus
• = blind-ending part of
stomach
• Corpus
• = body of stomach
• Pylorus
• = exit from stomach - 39What are the embryological regions of the stomach?• Oesophageal region
• Non-glandular
• Stratified squamous epithelium
• Cardiac region
• Secretes mucous only
• Fundic region
• Secretes mucous / gastric
juices
• Pyloric region
• Secretes mucous only
• Regulates stomach emptying - 40What are the cell types of the stomach and what do they do?• Consists of cylindrical glands
• Mucous (globlet) cells • Secrete mucus to protect
against HCl
• Parietal (oxyntic) Cells
• Secrete HCl to digest protein
• Chief (peptic) Cells • Secrete pepsinogen
(pepsin) to digest protein
• Entero-endocrine Cells • Secrete hormones - 41What regulates stomach emptying?• Mainly regulated by strength of contraction
• Also opening / closing of pyloric sphincter
• Stimulation of emptying
• Neural regulation - Expansion of stomach walls increases strength of
contraction
• Hormonal regulation – Release of gastrin increases strength of contraction and dilates pyloric sphincter
• Inhibition of emptying
• Factors in duodenum act to inhibit gastric contractions
• Increased pressure in duodenal walls, Low pH, High fat / peptide concentration, High osmolarity
• Neural regulation via increased sympathetic activity / decreased parasympathetic activity (via vagus)
• Hormonal regulation via secretin, cholecystokinin & gastric inhibitory peptide (GIP) - 42What animals do not have a gall bladder?Horses and rats
- 43What does the biliary system do?• Conveys bile from liver to duodenal lumen
• Secrete bile across hepatocyte membrane into canaliculi
• Bile flows from canaliculi into small bile ducts = ductules
• Ductules anastomose into larger ducts
• Ducts coalesce to form hepatic bile ducts
• Hepatic bile ducts lead into common bile duct
• Common bile duct enters duodenum at ‘Sphincter of Oddi’
• If present bile moves between gall bladder & bile duct via cystic duct - 44describe a general overview of the blood supply to the liver?• Hepatic Portal Vein
• 75% of blood entering liver
• Hepatic Artery
• 25% of blood entering liver
• Sinusoids
• Venous and arterial blood mix as they flow into sinusoids
• Central Veins
• Blood from sinusoids empty into central veins
• Hepatic Veins
• Central veins coalesce into hepatic veins
• Caudal Vena Cava
• Hepatic veins empty into caudal vena cava - 45Between the lobules are portal tracts (triads) what do they consist of?bile duct
hepatic artery
hepatic portal vein - 46What is the functional unit of liver?Hepatic acinus
- 47What are the functions of the liver?Storage of Glycogen, Iron, Copper and Vitamins
Detoxification of Body Wastes, Xenobiotics and Drugs
Synthesis of Cholesterol and Bile Acids
Synthesis of Plasma Proteins
Breakdown of RBC (degradation of harm)
Carbohydrate, Lipid and Amino Acid Metabolism
Removal of Bacteria
Production of Clotting Factors - 48Summerise liver metabolism?• Carbohydrate metabolism
• Glycogenesis
• Glycogenolysis
• Gluconeogenesis (maintenance of blood glucose)
• Lipid metabolism
• Oxidation of fatty acids and ketone body formation • Synthesis of cholesterol, phospholipids & bile acids
• Protein metabolism
• Deamination & transamination of amino acids • Synthesis of non-essential amino acids - 49Describe the process of Detoxification & Clearance in the liver?• Major role in purification, transformation & clearance
• All substances absorbed from GI organs pass through liver via
hepatic portal vein
• Removes harmful substances from blood
• Converts substances (e.g. drugs / toxins) into less toxic compounds
• Hepatocyte microsomes contain non-specific enzyme system which oxidises substances via the co-enzyme cytochrome P450, followed by further degradation
• Conjugated with water-soluble compounds and excreted in bile
• Drugs (pharmaceuticals)
• Nearly all drugs are modified / degraded in liver
• Conjugated or modified for excretion in urine or bile
• Toxins
• Responsible for detoxifying chemical agents & poisons
• Acute or chronic poisoning (e.g. phytotoxins, heavy metals)
• Endogenous Metabolites
• Ammonia converted to urea & excreted in urine
• Hormones inactivated by liver
• Haem broken down into bilirubin and excreted in bile - 50Describe degradation of Red blood cells?• RBCs removed from blood by macrophages in spleen and liver
• Degraded to yield haem from haemoglobin
• Haem converted to bile pigments
• Haem converted to biliverdin (green) in macrophage
• Biliverdin transformed to bilirubin (yellow)
• Bilirubin transported to liver in blood bound to albumin • Bilirubin conjugated with glucoronic acid in liver - 51Describe excretion of bile pigments?•
• •
Bile pigments play no part in digestion = waste route for haem
Conjugated bilirubin excreted into bile
In gut bilirubin can be acted on by intestinal bacteria
• Remove glucoronic acid
• Metabolise bilirubin to stercobilin (brown)
• This is what gives faeces its colour - 52What are the functions of bile?• Promotes hydrolysis by lipases (very effective detergent) • Bile acids facilitate digestion of dietary triglycerides by acting as
emulsifying agents – render fats accessible to pancreatic lipases • Facilitates intestinal absorption of lipids
• Bile acid micelles improves solubilisation and uptake of lipids • Exit route for waste products and drugs
• Synthesis and subsequent excretion in the faeces and represents only significant mechanism for the elimination of excess cholesterol - 53What is the composition of bile?• Water
• Electrolytes
• HCO3- actively secreted into bile making it alkaline
• Biliary proteins
• Bile pigments (bilirubin)
• Cholesterol
• Phospholipds (phosphatidylcholine) • Bile acids:
• Cholic acid
• Chenodeoxycholic acid - 54How is bile stored, and why is this beneficial?• Bile stored in gall bladder (if present)
• Allows storage and concentration of bile
• Beneficial to animals with intermittent digestion • Carnivores
• Omnivores
• Herbivores with continuous digestion:
• Levels of fat in diet usually low
• Horses - lack gall bladder
• Ruminants - have gall bladder with ineffective concentrating mechanism
• Due to presence of fermentation chamber occurring before duodenum release of fats into duodenum probably intermittent rather than continuous - 55What are the two major bile acids? How are they made water soluble?• Cholic acid
• Chenodeoxycholic acid
• These bile acids are hydrophobic
• To make them water soluble they are conjugated with glycine or taurine:
• Cholic acid + Glycine = Glycocholic acid
• Cholic acid + Taurine = Taurocholic acid
• Chenodeoxycholic acid + Glycine = Glycochenodeoxycholic acid
• Chenodeoxycholic acid + Taurine = Taurochenodeoxycholic acid - 56What is the recycling process of bile known as?Enterohepatic Circulation
- 57How does Enterohepatic Circulation work?• Bile acids absorbed from terminal ileum by active transport
• Transported back to liver via hepatic portal vein
• Efficiently captured from blood stream by liver via Na+- dependent Taurocholate Co-transporting Polypeptide (NTCP)
• This recycling process referred to as ‘Enterohepatic Circulation’ - 58How is bile secretion regulated?• Parasympathetic System (vagus)
• CCK
• Released in response to presence of fat in duodenum
• Causes contraction of gall bladder & relaxation of sphincter of Oddi
• Animals without gall bladder have inactive sphincter of Oddi with
continuous flow of bile into the duodenum
• Secretin
• Released in response to presence of acid chyme in duodenum • Mainly stimulates release of pancreatic juice
• But also increases HCO3- production by liver
• Also regulated by amount of bile salts returning to liver via enterohepatic circulation
• During a meal presence of fat in duodenum causes release of CCK
• Contraction of gall bladder
• Relaxation of Sphincter of Oddi
• Enterohepatic circulation of bile salts increases • Consequent increase in bile secretion by liver
• Between meals lack of fat in duodenum
• Relaxation of gall bladder
• Contraction of Sphincter of Oddi
• Enterohepatic circulation of bile salts decreases • Bile stored and concentrated in gall bladder - 59What can cause liver disease in animals?• Infection
• Poisoning (acute or chronic)
• Tumours - 60Wha are the clinical signs of liver disease?• Hepatic dysfunction
• Depression, decreased appetite & lethargy • Stunting & weight loss
• Vomiting & diarrhoea
• Polyuria & polydipsia (PU/PD)
• Ascites & altered liver size • Increase = hepatomegaly
• Decrease = microhepatica
• Icterus (= jaundice)
• Increased levels of bilirubin in blood
• Bleeding tendency - 61What are Porto-Systemic Shunts?• Aberrant vessel(s)
• Connect portal circulation direct to caudal vena cava
• Blood bypasses liver • 2 principal types
• Congenital = single shunt (may be genetic)
• Acquired = multiple shunts (due to portal hypertension) - 62What are the clinical signs and treatment options of porto-systemic shunts?Clinical Signs
• Liver unable to detoxify waste products = hepatic encephalopathy
• Hyperammoniaemia • Depression / tremors • Head pressing
• Polyuria / Polydipsia
• Worse after eating
Diagnosis & Treatment
• Ultrasound, exploratory laparotomy, fluoroscopy
• Prognosis
• Acquired = poor
• Congenital can be corrected by surgery - 63Name all the different peritoneum of the abdomen and what they connect to?• Serous membrane that lines abdominal cavity & envelops abdominal organs • Single continuous sheet
• Parietal peritoneum
• Closely adherent to abdominal wall • Extends through inguinal canal
• Visceral peritoneum
• Closely adherent to organ surface • Envelops organs
• Connecting peritoneum • Mesentery
• Connects bowel to body wall • Omentum
• Connects stomach to something • Fold
• Connects bowel / organ to one-another • Ligament
• Connects organ to body wall / bowel - 64What are the holes in the diaphragm?• Aorta passes through aortic hiatus between left & right crura
• Caudal vena cava passes through caval foramen in central tendon
• Oesophagus passes through oesophageal hiatus - 65What are the 4 lobes of the liver?• Left & Right lobes (split into medial & lateral in dog)
• Caudate (papillary process)
• Quadrate - 66What are the different epithelium in the different regions of stomach and the oesophagus?oesophageal-stratified squamous
cardiac-glandular (mucous only)
fundic-Glandular (HCl / pepsinogen)
pyloric-Glandular (mucous only) - 67What are the two lobes of the pancreas and where are they?2 lobes
• Right lobe running in
cranio-caudal direction
• Left lobe running medio- laterally - 68What is the jejunum covered by?greater omentum
- 69What is this called: Groove with lips that runs from oesophagus to reticulo-omasal orificeOesophageal Groove
Also referred to as reticular groove or ventricular groove - 70How does the oesophageal groove?• Groove with lips that runs from oesophagus to reticulo-omasal orifice
• When animal sucks warm milk reflex causes lips to curl over forming a tube
• Cold milk prevents complete curling over and can then spill into reticulo-rumen
• Milk passes from oesophagus direct to omasum and thence abomasum for
digestion hence avoiding fermentation by developing rumen
• If milk intake exceeds capacity of tube it spills over into the rumino-reticulum and is fermented
• Lactose fermented to lactic / other organic acids
• Adverse effect on developing micro-organisms (common cause of diarrhoea in
calves)
• Sucking and chemoreceptors in pharynx sensitive to milk compounds cause reflex closure of groove
• Can also be stimulated by certain salt solutions used to prepare oral medication that bypasses fermentation chamber
• Reflex lost when animal weaned
• Retained if milk continues to be fed
• Retained in browsers
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- Flashcards on GI, created by Heather M on 17/08/2018.
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