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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