Animal Digestive Systems

Monogastric System Definition

Animals with a single-chambered stomach, such as pigs and humans.

Peristalsis

Wave-like muscular contractions that squeeze food down the digestive tract.

Hydrochloric Acid (HCl) in Stomach

Softens the food bolus and kills pathogens.

Pepsin

An acidic-condition protease enzyme that begins breaking down proteins in the stomach.

Chyme

A sloppy mixture of churned food produced by the stomach.

Duodenum Bile Function

Emulsifies fats into small globules to allow lipase attack.

Pancreatic Digestive Functions

Secretes alkali, protease, carbohydrase, and lipase enzymes into the duodenum.

Pancreatic Endocrine Functions

Secretes insulin and glucagon directly into the bloodstream to control glucose levels.

Villi Function

Millions of tiny, finger-like projections in the ileum that absorb nutrients into the bloodstream.

Villus Structure (Lacteal & Capillaries)

Central lacteal transports fat to liver; capillary network absorbs sugars and amino acids.

Goblet Cells

Secretes mucus to keep food moving smoothly alongside peristalsis.

Colon Function

Absorbs most remaining water, leaving waste material (roughage).

Rectum & Anus

Stores faeces until defecation occurs via the anal sphincter.

Hindgut Fermenters Definition

Monogastric herbivores relying on symbiotic bacterial fermentation in an enlarged cecum and large intestine.

Examples of Hindgut Fermenters

Horses, rabbits, guinea pigs, hares, rodents, and rhinos.

Cecotropes

Highly nutritious soft faecal matter produced in the cecum and re-ingested by the animal.

Ruminant Definition

Mammals with a specialized 4-chambered stomach designed to break down cellulose.

Examples of Ruminants

Cattle, sheep, goats, deer, camels, giraffes, and kangaroos.

Rumen Function

Large capacity chamber where microbial digestion begins and food is stored.

Reticulum Function

Honey-combed chamber that filters foreign objects and passes food back for rumination.

Omasum Function

Grinds food via muscular contractions and absorbs water using leaf-like folds.

Abomasum Function

The 'true stomach' with glandular tissue that secretes HCl and digestive enzymes.

Ruminant Herbivore Dentition

Lack upper incisors (possess a dental pad) and have broad molars for grinding.

Non-Ruminant Herbivore Dentition (e.g., Horse)

Upper and lower incisors, long diastema, and large grinding premolars/molars.

Carnivore Dentition (e.g., Lion)

Sharp, pointed teeth with large canines and carnassial teeth for tearing meat.

Omnivore Dentition (e.g., Bear)

Pointed incisors/canines for tearing and flattened molars for crushing plant matter.

Avian Crop

Outpocketing of the oesophagus used to temporarily store and soften food.

Avian Proventriculus

The glandular stomach where chemical digestion begins via acid and enzymes.

Avian Gizzard (Ventriculus)

The muscular stomach that mechanically grinds up tough food, often aided by grit.

Avian Cloaca

Single terminal opening where digestive, urinary, and reproductive wastes are excreted.