Digestion in Animals Overview

Digestion: An Overview

• Digestion is a vital biological process where organisms break down food into simpler forms for cell use.
• Different animals have diverse digestive mechanisms adapted to their diets and environments.

Examples of Digestive Systems in Animals

Hydra

• Hydra is a multicellular, microscopic creature in freshwater environments.
• It has a simple digestive system.
• Its name reflects its resemblance to a mythological creature.
• Hydra has a cylindrical body with tentacles for capturing prey.
• This structure enables efficient feeding in aquatic environments.

Cnidarians

• Cnidaria is a phylum encompassing soft-bodied, stinging organisms like corals, sea anemones, and jellyfish.
• The name "Cnidaria" comes from the Greek word cnid, meaning "nettle," referring to their stinging abilities.

Earthworm

• Earthworms (annelids) have a complete digestive tract, a long tubular structure with a mouth and anus.
• Their digestive system is divided into specialized regions (mouth, pharynx, esophagus, crop, gizzard, intestine, and anus).
• They feed on decaying plant material in soil.
• During burrowing, they ingest soil which aids digestion.
• The food travels through the pharynx, esophagus, crop, and gizzard. Muscular gizzard walls grind the food with help from ingested soil.

Grasshopper

• Grasshoppers (arthropods) have a three-part digestive system (foregut, midgut, and hindgut).
• The foregut includes the buccal cavity, pharynx, esophagus, crop, and proventriculus. The proventriculus grinds food and controls passage into midgut.
• The midgut is the main site of digestion and absorption.
• The hindgut processes remaining material and expels waste through anus.

Human Digestion

• Human digestion involves six key processes: ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.
• Digestion begins in the mouth with mechanical breakdown by teeth and tongue, and chemical breakdown by saliva initiating starch digestion.
• Food travels down the pharynx, into the esophagus to the stomach where it's churned and chemically digested using enzymes like pepsin and hydrochloric acid.
• It's converted to chyme and stored in the stomach.
• The small intestine completes digestion, using enzymes secreted by the pancreas and bile from the liver to break down fats, carbs and proteins.
• Villi in the lining absorb nutrients. Lacteals absorb fats.
• Remaining water and waste are consolidated in the large intestine and expelled as feces.