digestive ii vet 206 simple stomach intestines. food storage start/continue digestion of basic...
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Digestive II
VET 206Simple stomach
Intestines
Food storage Start/continue digestion of basic energy
formin
Major Functions of Stomach Food storage Start/continue digestion of basic energy
forming nutrients
Directional terms/Function Oral-toward the mouth Aboral-away from the mouth
Simple Stomach function Protein digestion begins
Formation of chyme Fat emulsification begins
Simple Stomach
Lesser curvature
Greatercurvature
Rugal Folds
Omentum
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!!
Cardia
Muscular Thickening-functional sphincter Horses, rats-especially thick!!
Mucus producing cells=Goblet cells Mucin (Alkaline) + Bicarbonate (base) Protect stomach lining from stomach acids (pH 2-3!!)
(mucus-noun; mucous-adj)
Fundus and Body Distend and expand as needed Glandular area
Chief cells-pepsinogen Inactive precursor to pepsin (proteolytic enzyme)
Parietal cells-HCl acid Activates pepsinogen
Mucous cells- mucus Intrinsic Factor-allow absorption of Vitamin B12
Fundus and Body
Parietal cell -control
Gastrin
(Parasympathetic neurotransmitter)
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
Peristalsis-antrum
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
Colon Ascending, transverse
and descending Rectum-terminal
portion of colon Rectal valves-
Separates gas from solid material
L.R.
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 liningcrop 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 PhospholipidsWhere 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-RBC recycling
http://diaglab.vet.cornell.edu/clinpath/modules/chem/images/bilirubin%20metabolism.jpg
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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