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112 Cards in this Set
- Front
- Back
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What are the areas betwen the teeth called?
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Diastema
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What makes up dentine?
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70% calcium hydroxyapetie
20% organic components like collagen fibres 10% water |
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What is the function of dentine?
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Has an elastic quality, so it provides flexibility and shock absorption for overlying enamel.
Can be replaced throughout life. |
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Discuss the structure of dentine.
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Make of odontoblast cell bodies laid down on a matrix of collagen fibres. These sit in dentinal tubules that also contain nerve endings and fluid.
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What makes up enamel?
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96% mineral - calcium hydroxyapetite
4% organic and water (from keratin family...ie, modified skin) Most highly mineralised tissue in body |
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What gives enamel its strong properties?
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During its development, calcium absorbs ions like strontium, magnesium, lead and fluoride.
Makes it VERY hard and able to withstand mechanical forces during mastication and prehension of food. |
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How is enamel different from dentine?
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Different mineralisation
Enamel not replaceable after eruption (except in bunnies) Enamel not innervated, not living |
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What is the peridontal ligament?
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It runs in a spiral fashion between cement and alveolar bone to suspend the tooth in a bony socket
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What is the gingiva sulcus?
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This is where the tooth is attached to the gingiva by epithelium.
Place for infection! |
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Name the salivary glands in the canine.
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Mandibular
Parotid Sublingual Buccal (ventral and dorsal, zygomatic) |
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What are the different types of papillae, and their shape?
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Filiform - small, fine, cone-like
Fungiform - small and circular Foliate - layered, and tube-like on edges of tongue Vallate - looks like an encircled circle |
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What nerves create the general sensation of the tongue and taste?
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General sensation - mandibular nerve (rostral 2/3 and glossopharyngeal for root)
Taste - chorda tympani, branch of facial nerve |
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What is the dental formula for the dog?
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3-1-4-2
3-1-4-3 |
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What regulates the salivary glands?
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Parasympathetic causes vasodilation and flow of saliva
Sympathetic causes vasocontriction and slow flow |
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Which nervous systems control the gut?
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Parasympathetic, sympathetic and enteric - all autonomic
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Describe the origin of the sympathetic nerve fibres and their synapse points.
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They originate from T5-L2 and synapse in prevertebral ganglia
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What do postganglionic sympathetic nerve fibres release as a neuroxmitter?
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Noradrenaline
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Describe the origin of the parasympathetic nerve fibres and their synapse points.
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They originate from vagus in medulla and pelvic nerve from S2-S4. The fibres all synapse in the enteric nervous system - ALL POSTGANGLIONIC FIBRES ARE ENTERIC NEURONES
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Describe the somatic innervation of the gut.
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Vagus nerve provides voluntary control over skeletal muscle and pudendal nerve provides control over external anal sphincter.
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How many nerve cells are in the enteric nervous system?
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10-100 million
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Explain the enteric nervous system and what it controls.
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The reflexes can operate independently of the CNS and it controls motility, fluid movements and blood flow.
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What are the two plexuses in the gut?
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The submucous plexus (Meissners plexus) and the myenteric plexus (Auerbachs plexus) which is between the muscles layers
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What do the myenteric and submucous plexuses control?
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Myenteric - smooth muscle motility
Submucous - absorption, secretion and blood flow |
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What are the 3 functional categories of neurons?
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Motor
Sensory Interneurone |
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What are the most important neuroxmitters in the enteric nervous system?
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Acetyl choline (contracts sm)
Substance p (contracts) Nitric oxide (relaxes sm) Vasoactive intestinal peptide (VIP, relaxes) |
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Where are neuroxmitters located in neurons?
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They are located in the cytoplasm and are sent out via vesicles.
There can be more than 1 type in a neuron |
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Explain the reflex pathways of the GI tract.
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Controlled by mechanoreceptors and chemoreceptors which respond to stretch and chemies.
Local - Enterogastric reflexes Intrinsic - Peristalsis and segmentation by ENS Long Primary Afferents - Accn reflex, control of stomach motility by vagovagal |
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What muscle is involved in segmentation?
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Only circular muscle, adjacent excitation and inhibition.
Contents do NOT propel |
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What is the definition of a sphincter?
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An area of high interluminal pressure that offers resistance to flow
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What are the two spincters of the oesophagus?
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The upper oesophageal sphincter (UOS) and the lower oesophageal sphincter (LOS).
These are not well-defined anatomical sphincters, just areas of sustained high pressure. |
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What causes contriction of the UOS?
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1. cricopharyngeal muscle
2. elastic recoil of the surrounding tissues |
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To open the UOS, what must happen?
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The cricopharyngeal muscle must relax.
Innervation is from the glossopharyngeal nerve (CN IX) |
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Describe the LOS.
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Tonically closed area of raised pressure. Has oblique entry into cardiac region of stomach, which allows for resistance esp in horse.
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What are the controls of the LOS?
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Constriction is caused by vagal excitation.
Relaxation is caused by beta-andrenergic mechanism and VIP. |
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Describe the pyloric sphincter.
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A thickening of circular muscle which produces contractions that coordinate with the rest of the pyloric muscle.
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What is the 'duodenal break'?
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Result of neural and hormonal mechanisms that monitor chyme to give + or - feedback about speed of gastric emptying.
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What are the clinical signs of emesis?
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Tachypnoea, salivation, pupilodilation, sweating and pallor.
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What are the peripheral and central stimuli for vomition?
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Peripheral - pharyngeal, oesophageal or gastric irritation or excessive gastric distension.
Central - labyrinthine (middle ear) stimulation, drugs or electrical stimulation of vom centre in medulla |
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What is retching?
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The same as emesis, except that the UOS doesnt relax, so food does not get into the mouth.
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Describe the sequence of vomition.
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1. glottis and nasopharyngeal orifices close
2. duodenal and gastric antral antiperistalsis 3. stomach and oesophagus relaxes = projectile return of food to mouth augmented by abdominal press |
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How do ruminants vomit?
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Abomasal reflux - vomit from abomasum to reticulorumen.
(can projectile in rhododendron poisoning tho) |
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What two sphincters control ruminant regurgitation and what nerve is the control?
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LOS and pre-diaphragmatic sphincters
Under control of vagus - muscle contraction by ach and relaxation by vip |
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What is the only way out of the rumen besides the oesophagus?
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The reticulo-omasal orifice (ROO), which is control by the vagus and the opening is time with the ruminant "A cycle"
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Describe the 4 steps of the ruminant "A cycle".
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1. Double contraction of the reticulum, roo dilates to allow emptying into omasal canal
2. Contraction of cranial and dorsal sacs, and dorsal blind sac, of rumen 3. Contraction of ventral blind sac of rumen 4. Contraction of ventral rumen |
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What is the "gastric groove" in ruminants?
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It is on the medial side of the reticulum. Two muscular lips in a long spiral that are open in youth for milk passage.
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Describe the sphincter of oddi (SOO).
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Bile enters the duodenum through this sphincter. The opening of it is controlled by hormones in the GI tract and the vagus nerve.
Coordinated with peristalsis. |
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Discuss the two sphincters of the anus.
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Internal sphincter - smooth muscle that is not under voluntary control
External sphincter - striated muscle under voluntary control. |
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How is appetite controlled?
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By the hypothalamus
Constantly switched on! |
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How is satiety achieved?
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Distended stomach
Fever GI hormones Blood glucose level Fear/stress |
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Define prehension.
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The ability to take food into the mouth.
Involves teeth, lips and tongue. |
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Define mastication.
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Mechanical breakdown of food by teeth.
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Describe the differences between the mastication of humans/cattle and dogs/cats.
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Humans and cattle can grind food into fine structures before swallowing becase of flat-topped premolars and molars.
Dogs and cats have sharp premolars and molars that are designed for cutting and shearing - swallow food in chunks. |
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What controls salivation?
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Medulla oblongata.
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What is parasympathetic stimulations role in salivation?
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Para stimulation with ach or vip increase blood flow to the glands which increase salivation.
Sympathetic stimulation reduces flow. |
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Which glands secrete saliva for which foods?
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Meat and moist foods - submandibular and sublingual
Dry - parotid, which has a higher water content |
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What are the 3 phases of swallowing and what nerves control it?
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Oral - Voluntary - CN 5,7,12
Pharyngeal - Involuntary - CN 5,7,9,10 Oesophageal - Involuntary - CN 10 |
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What is the difference the the oesophageal muscle of the dog and cat?
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Dog - partly striated
Cat - all smooth |
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Is there peristalsis for liquids?
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A contraction only occurs for the last swallow
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What is the primary contraction type in the intestine?
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Segmentation
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What is the purpose of segmentation?
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To efficiently mix food with enzymes and other secretions - allows better exposure of nutrients to brush border
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Describe chyme.
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This is a soup-like material that empties from the stomach into the duodenum containing particles of 2 mm or less.
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How does calorific value determine rate of gastric emptying?
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High calorie diets (fat) empty more slowly
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Describe housekeeper contractions.
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When the stomach is empty, these "sweeping" contractions run through the whole organ to empty saliva, and gastric secretions to duodenum
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What do active and inactive enzymes end in?
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Inactive -ogen
Active -ase (except trypsin and pepsin) |
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What do chief cells secrete?
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Chief cells are in gastric pits and secrete the enzyme PEPSINOGEN
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How does pepsinogen become activated?
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It interacts with HCl in the stomach to become pepsin
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Where is HCl produced in the stomach?
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In the parietal cells of the gastric pits.
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Why doesn't the stomach get hurt by the acid?
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The gastric mucosal barrier protects it.
Made up of mucus containing bicarbonate that comes from the GASTROCYTES, a layer of ep basal membrane cells with bicarb rich cytoplasm |
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What enzymes does the pancreas produce?
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Trypsinogen, amylase and lipase
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How is trypsinogen activated?
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Produced in pancreas, enters duodenum and is activated by ENTEROKINASE which is produced by duodenal mucosal cells
Activated trypsin can make more of itself |
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How is trypsinogen stored?
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In zymogen granules in the pancreatic cells to prevent autodigestion of pancreas
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What is the purpose of trypsin?
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To split proteins into small peptides.
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How is amylase made active?
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Is released from pancreas (NOT in zymogen granules) and interacts with calcium and chloride ions from duodenum to become active.
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What is the purpose of amylase?
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To split starch into maltose, maltotriose and glucose.
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How is lipase made active?
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Released from cytoplasm of pancreatic cells (NOT in zymogen granules) and interacts with colipase to become active
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What is the purpose of lipase?
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To hydrolyse fats into fatty acids and monoglycerides
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What else does the pancrease produce besides enzymes (exocrine related)?
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Bicarb to neutralize the HCl in the chyme coming from the stomach.
It also creates a nice alkaline medium that is good for activity of the pancreatic enzymes. |
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What is the function of bile?
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-Contains bile acids help digest fat
-Contains bicarb to help create alkaline medium |
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What makes poo brown?
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Stercobilin, which is converted bile pigments.
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What is the role of intestinal enzymes on the brush border?
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These include peptidases which hydrolyse peptides to amino acids and disaccharidases (sucrase, lactase) which hydrolyse disaccharides to glucose.
They are designed to complete the process of digestion. |
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What stimulates pancreatic and bile secretions?
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Nutrients (esp fat) entering the duodenum stimulate CHOLECYSTOKININ, which in turn stimulates bile and pancreatic secretions.
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What is SECRETIN's role in digestion?
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When released, stimulates pancreatic secretion of bicarb.
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Stomach stage of protein digestion.
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HCl and pepsin hydrolyse polypeptides into shorter peptide chains.
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Intestinal stage of protein digestion.
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Trypsin and chymotrypsin in the duodenum break down peptides to AA and dipeptides.
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Brush border stage of protein digestion.
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Peptidases on brush border hydrolyse dipeptides to free AA, which binds to carriers on enterocytes entering blood on other side and going to the liver.
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Stomach state of carb digestion.
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Not so important - HCl randomly breaks down long chains into shorter ones.
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Intestinal stage of carb digestion.
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Amylase in duodenum hydrolyses starch into small units like maltose, dextrins and glucose.
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Brush border stage of carb digestion.
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Disaccharidases on brush border further break down carbs to either glucose, galactose or fructose.
Xported to liver via portal vein. |
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Stomach stage of fat digestion.
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Not impt in stomach - only gastric lipase does a bit.
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Intestinal stage of fat digestion.
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Bile acids emulsify fats, making them more water soluble. Lipase hydrolyses the triglycerides into monoglycerides and free FA.
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Brush border state of fat digestion.
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Fats are NOT digested on brush border.
Instead, bile acids help FA enter enterocyte by forming a MICELLE, which contains hydrolysed fat, lipase and bile acids. |
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What happens to micelles once in the enterocyte?
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Triglyceride is reformed from free FA and attach to lipoprotein and cholesterol to form a CHYLOMICRON complex.
This enters the lacteal and not capillaries, going to the lymph nodes. |
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Where are bile acids reabsorbed?
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In the ILEUM, and are xported to the portal vein and removed by hepatocytes and stored for later use.
"Entero-Epatic Recirculation of Bile Acids" |
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Describe passive absorption of nutrients.
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Nutrients enter enterocyte directly across cell membrane without need for special carrier or energy.
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Describe active absorption of nutrients.
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Absorption requires energy, which is provided by ATP. This improves the speed of absorption.
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Which vitamins are absorbed with FA into lacteals and which are absorbed in the small intestine?
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Lacteals - A,D,E,K
Small Int - B,C (active) |
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How is glucose utilised after delivery to liver?
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Converted to glycogen and stored in hepatocytes until needed.
Some used immediately to maintain blood glucose, while excess is converted to fat and stored in adipose tissue. |
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How are amino acids utilised after delivery to liver?
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In liver, used for building new protein for growth and repair.
Excess AA used as E source, can be converted to fat and stored in adipose. Ammonia produced is converted to urea and excreted. |
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How are FA utilised after chylomicron sent into lacteals?
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Travels through the lymph vessels and eventually get to circulation near heart.
Once in circulation, most triglyceride is deposited in fat depots and some is used for energy/repair needs. |
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What % of body weight is the liver in herbivores vs. carnivores?
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H - 1-1.5%
C - 3-8% |
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What are some key liver functions?
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1. Metabolism
2. Bile secretion 3. Storage of metabolites 4. Detox |
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What percent of the livers volume is blood?
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20%
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Where does the bulk of the liver lie in most species?
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To the right
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What are the canine liver lobes?
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Left lateral
Right lateral Right medial Left medial Quadrate Papillary process Caudate process |
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What are the 3 liver ligaments?
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R/L triangular
Coronary Fulciform |
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What is contained in the "portal triad"?
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Branch of portal vein
Branch of hepatic artery Bile system and Lymph ducts |
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What are the 2 liver blood supplys?
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"Functional" - from rest of body, comes from portal
"Nutritional" - from hepatic artery, for the liver itself LIKE HEART |
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What is the function of Kuppfner cells?
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They are on the luminal surface of sinusoidal epithelial cells.
Are fixed macrophages and clear out old RBCs and recycle iron. |
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What is the innervation of the liver?
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PARA - vagal trunks
SYM - periarterial plexuses |
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What is the duct that takes bile from the liver to gallbladder?
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Cystic duct
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Why don't horses need gallbladders?
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They are trickle feeders and have constant bile supply and a diet of no fat, just fibre.
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What supplies blood to the pancreas?
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Cranial and caudal pancreaticoduodenal arteries (branches of celiac artery).
Drains into portal vein. |
