Species variations Margo plicatus-horses (horses) Line between glandular and nonglandular portions of stomach of the stomach (carnivores don’t have nonglandular portion) Gastrophilus larva attach here! Ruminants-they get their own lecture!!
Antrum Distal portion of the stomach Grinds food Regulates acid production G cells-produce hormone Gastrin Gastrin enters bloodstream, not into lumen Gastrin stimulates production of HCl and pepsinogen Mucous cells present
Pylorus Sphincter-regulates movement of “chyme” Helps prevent backflow of material from duodenum Remains partially open-liquids move quickly through stomach, solids slower Enterogastric reflex If: Distended intestines or Increased acidity in intestines Then: decreased stomach emptying
Control of motility PNS Vagus nerve Increases contraction of Body/Antrum for forward motion of chyme Hormonal control Antrum fills-G cells produce Gastrin Gastrin causes relaxation of Fundus SNS Decreases motility=“gastric atony” Stress can induce
GI hormones Gastrin Trigger=antrum is stretched Action=relaxes fundus Secretin Trigger=decreased pH in duodenum Action=decrease peristalsis in body and antrum CCK Trigger=increased fats and protein in duodenum Action=decrease peristalsis in body and antrum
With all this acid, why don’t all animals have ulcers??? Mucus production pH < 3 G cells stop production of Gastrin Controls on parietal cells in HCl production Cells turnover every 3-4 days throughout the gi tract. Prostaglandins Control HCl production via Gastrin Increase bicarbonate-for mucous layer Maintain blood flow
With all this acid, why don’t all animals have ulcers??? Prostaglandins Control HCl production via Gastrin Increase bicarbonate-for mucous layer Maintain blood flow NSAIDs-block prostaglandins!!! Very hard on the stomach Ulcerogenic
Normal Gastric Transit Time? 2-4 hours; longer for high fast foods What could cause delayed emptying?? Stress Obstruction
Intestines Small Intestines Duodenum (pancreatic and bile duct empties) Jejunum Ileum Mesentery
Layers of the intestines Mucosa Submucosa Muscularis Serosa Lumen
Function Most nutrient absorption occurs in the small intestines Microvilli (brush borders) Digestive enzymes Nutrients transported via carriers or simple diffusion What are nutrients? Protein, fats, carbohydrates Minerals and vitamins Water (most water absorption in large intestine)
Villi: Capillaries Lacteals-vessels where lipids are absorbed Crypts Replenish cells of villi within 2-3 days (Crypts of Lieberkuhn) Peyers patches- immune function
SEGMENTAL (MIXING) CONTRACTIONS Mixing action, slows intestinal motility, allows for proper digestion/absorption of nutrients
PERISTALTIC (PROPULSIVE WAVE) CONTRACTION Direction of wave
Controls of intestinal motility Stretch controls Parasympathetic nervous system- maintains normal motility Stress can cause Ileus Post-op, certain antidiarrheals CCK-action in the intestines-increase motility Prostaglandins-increase motility and secretions
Basic nutrient digestion Electrolytes, water-absorbed unaltered Carbohydrates Amylase-enzyme in saliva, pancreas Complex carbs to dissaccharides (sucrose, maltose, isomaltose, and lactose) Specific enzymes (sucrase, maltase, isomaltase, lactase)-digest disaccharide to monosaccharide (glucose, galactose and fructose) *** Intestines adapt enzymes to diet, takes time to upregulate proper enzymes!!!!!
Basic nutrient digestion-Protein Pancreatic Proteases (Trypsin, chymotrypsin, carboxypeptidase…) Break proteins (polypeptides) into peptides All proteases are released as inactive form!! **Trypsinogen activates all protease!! Peptides then absorbed at the brush border
Basic nutrient digestion-Fats Emulsification-starts in the antrum Micelle formed Bile Acids-release into the duodenum-surrounds micelle-making them water soluble Pancreatic lipase-breaks down further Diffuses at brush border
Basic nutrient digestion-vitamins Fat soluble vitamins- Vitamins A, D, E, K Absorbed with micelles into lacteals Fat digestion problems can lead to Vitamin deficiencies
Large intestine Cecum (ileocecal junction), colon Colon terminates in rectum and anal canal Function-water and electrolyte absorption, lubrication (mucus secreting cells), storage Microbial action Very simple in carnivores Hindgut fermenters-highly adapted Control-parasympathetic nervous system Stretch receptors
Anus Internal and external anal sphincter Internal Parasympathetic-relax internal anal sphincter Sympathetic-tighten internal anal sphincter External Voluntary control Perianal surgery Risk of nerve damage-incontinence Avulsion of tail Spinal cord injury
Anal Glands Scent glands Normally expressed with normal BM
Avian Digestive System Esophagus-right side of the neck Mucous glands-lubricates Crop-expansion of esophagus-storage Larger crop-need less meals per day Mucosal lining crop milk (pigeons, doves) Protection for insectivores
Avian Digestive System Stomach Glandular Stomach =Proventriculus Chemical digestion Muscular Stomach =Gizzard Striated muscles to grind food (bone, scales, nuts) Produces pellets to be regurgitated (owls, hawks, herons, etc)
Avian Digestive System Cloaca-termination of tracts Coprodeum-from intestines Urodeum-from kidneys and genitals Proctodeum-site of sperm storage prior to “cloacal kiss”, stores other excrement. Mute= waste product Dark fecal center with ring of urates
Related Organs-Liver (Hepatic) Largest organ (skin?) Hepatocytes Hepatic portal system Intestinal capillaries to hepatic sinusoids Lining sinusoids=phagocytic cells Infectious agents, toxins, old RBCs Hepatic Triad: 1) A hepatic artery 2) A branch of the hepatic portal vein 3) A bile duct
Liver Storage-excess glucose stored as glycogen Glycogenesis= production of glycogen Glycogenolysis= release of glucose by breakdown of glycogen Gluconeogenesis AA broken down to then form into Glucose Liver can perform if needed
Liver Function Blood-storage and Filtration Recycles RBC’s, macrophages Clotting Iron Storage Metabolic Nutrients Drug Metabolism Excretory/Secretory Bile
Liver-Metabolic functions Carbohydrates Store Glycogen Gluconeogenesis- (Amino acids to glucose) Converts Galactose and Fructose to Glucose Why do we need glucose???
Liver-Metabolic Functions Fats Forms Ketone Bodies for an alternate energy source when Carbohydrates are not available Form Lipoproteins-LDL and HDL Form Cholesterol and Phospholipids Where do we need phospholipids?? Fat Synthesis-Convert CHO and proteins to Fat
Liver-Metabolic Functions Protein- Synthesize nonessential Amino Acids Nitrogen Removal-Converts Ammonia to Urea Forms All Plasma Proteins (Except Globulins- who produces globulins??) ALBUMIN!!!!!! Clotting Factors!!!!!
Liver-Storage functions Storage/metabolism –glucose, amino acids, some vitamins (fat soluble), Iron and minerals (Copper)
Liver-Bile Fat digestion with bile acids Bile Bile acids, cholesterol, bilirubin (breakdown product of hemoglobin in RBCs) Bile is secreted into canaliculi, come together to form bile ducts Hepatic duct, cystic duct and common bile duct Horses and Rats- No gallbladder
Liver Disease-What do we look for Blood work Liver enzymes Albumin Bilirubin levels Bile Acid Trials Clotting Factors Ammonia levels Ultrasound Biopsy
Liver Disease-What do we look for Liver disease-Ascites! Fluid that has left the capillaries in attempt to maintain oncotic pressure
Liver Disease-What do we look for Improper bilirubin metabolism= Jaundice (clinical sign) or Icterus (appearance of serum)
Liver-What do we look for?? Hepatoencephalopathy-clinical sign of excess ammonia in the blood Portosystemic shunts
Pancreas Exocrine gland=empties product via pancreatic duct Pancreatic amylase Proteases (trypsin) Lipase Bicarbonate-neutralize stomach acids Endocrine function Production of insulin and glucagon
Pancreas-exocrine function Hormonal control is most important. Secretin-released by response to HCL in intestine CCK - released by presence of protein & fats
Pancreas Insulin Produced by beta cells in the islets of Langerhans Stimulated by increase in blood glucose (after a meal) Drives glucose from blood into cells Feed the cells Glucagon Alpha cells produce Released when blood glucose is low (between meals) Stimulates glycogenolysis and gluconeogenesis
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