Comparative Digestive Systems in Animals

Digestion

Process of breaking down food into nutrients.

Absorption

Uptake of nutrients into the bloodstream.

Mechanical Digestion

Physical breakdown of food into smaller pieces.

Chemical Digestion

Enzymatic breakdown of food into simpler molecules.

Microbial Digestion

Digestion aided by microorganisms in the gut.

Enzymes

Proteins that catalyze biochemical reactions in digestion.

Mastication

Chewing process that prepares food for swallowing.

Non-Ruminant

Animals with a simple stomach structure.

Monogastric

Single-chambered stomach, e.g., pigs and cats.

Ruminant

Animals with a complex stomach for fermentation.

Avian

Birds with specialized digestive systems for grains.

Carnivores

Flesh-eating animals with simple GIT organization.

Herbivores

Plant-eating animals with complex GIT structures.

Omnivores

Animals that consume both plant and animal matter.

Granivores

Animals primarily feeding on seeds and grains.

Pregastric Fermentation

Microbial fermentation occurring before the stomach.

Hindgut Fermentation

Fermentation occurring after the small intestine.

Saliva

Fluid containing water, enzymes, and electrolytes.

Lysozyme

Antibacterial enzyme found in saliva.

Amylase

Enzyme that digests starch into sugars.

Deglutition

The act of swallowing food or water.

Bolus

Rounded mass of food formed during chewing.

Peristalsis

Wave-like muscle contractions moving food through GIT.

Vomiting

Reflex expelling contents from the stomach.

Emetics

Drugs that induce vomiting.

Chemoreceptor Trigger Zone (CTZ)

Brain area that detects stimuli for vomiting.

Vomiting Center

Brainstem region coordinating the vomiting reflex.

Esophageal area

Region with no glands; some amylase activity.

Cardia

Secretes alkaline mucus to protect stomach lining.

Gastric glands

Produce HCl and pepsinogen in the stomach.

Pyloric region

Contains glands that secrete protective mucus.

Gastric juice

Contains water, pepsinogens, HCl, and intrinsic factor.

Cephalic phase

Brain signals increase stomach secretions pre-meal.

Gastric phase

Food stimulates hormone release for HCl production.

Intestinal phase

Hormones reduce stomach activity after food enters.

Gastrin

Hormone that stimulates gastric acid secretion.

Histamine

Increases HCl production in stomach lining.

Acetylcholine

Neurotransmitter enhancing gastric secretions.

Duodenal area

Mixes digesta and secretions in the small intestine.

Jejunal area

Primary site for nutrient absorption.

Brunner's gland

Produces alkaline secretion to protect duodenum.

Bile salts

Activate lipase and emulsify fats for digestion.

Pancreatic lipase

Enzyme that breaks down fats efficiently.

Large intestine

Retrieves nutrients, electrolytes, and water.

Microbial activity

Aids digestion in the large intestine.

Vitamin synthesis

Bacteria produce some B vitamins in large intestine.

Chymosin

Clots milk in young pigs to control digestion.

Lactase

Enzyme for digesting milk, decreases post-weaning.

Weaning diets

Dietary adjustments for young pigs during weaning.

Gastric lipase

Enzyme aiding fat digestion in dogs and cats.

Pre-caecal digestion

Digestion occurring before the cecum in horses.

Pre-Caecal Digestion

Initial enzymatic digestion in stomach and small intestine.

Microbial Fermentation

Breakdown of fiber into volatile fatty acids in large intestine.

Volatile Fatty Acids (VFAs)

Energy sources produced from fiber fermentation.

Gall Bladder Absence

Horses cannot store bile due to lack of gall bladder.

Ruminant Stomach Compartments

Rumen, reticulum, omasum, abomasum for digestion.

Oesophageal Groove

Allows milk to bypass undeveloped rumen in young ruminants.

Rumen Development

Stimulated by fibrous foods and VFAs for nutrient absorption.

Ruminant Digestion Cycle

Includes regurgitation, remastication, reinsalivation, and redeglution.

Carbohydrate Breakdown Stages

Conversion to simple sugars followed by fermentation.

Methane Production

7% energy loss in ruminants during fermentation.

Acidosis Risk

High-concentrate diets may cause lactate buildup.

Rumen Degradable Protein (RDP)

Protein broken down by microbes into peptides and amino acids.

Rumen Undegradable Protein (RUP)

Protein not broken down, beneficial for dairy cows.

Urea Poisoning

Excess urea leads to toxic ammonia levels in blood.

Lipid Breakdown

Bacterial lipases convert lipids into free fatty acids.

Biohydrogenation

Unsaturated fatty acids converted to saturated forms.

Fatty Acid Absorption

Short-chain fatty acids absorbed in rumen; long-chain in SI.

Avian Digestion

Beak replaces lips; teeth absent in birds.

Esophageal Diverticulum

Reservoir for food storage in birds.

Glandular Stomach

Produces HCl and pepsinogen for digestion.

Koilin Production

Hardens in presence of HCl in avian gizzard.

Pancreatic Juices

Contain enzymes similar to mammalian secretions.

Intestinal Mucosa Enzymes

Produces mucin, amylase, maltase, sucrase, proteolytic enzymes.

Chick Digestive Efficiency

Chicks digest uncooked cereals well due to enzyme activity.

Cloaca Function

Final transport of digesta in avian species.