Notes on Animal Nutrition and Digestive System

Purpose of the Digestive System

• The digestive system breaks down food into usable nutrients necessary for survival and energy production.

Gastrovascular Cavities of Jellyfish and Nematodes

• Gastrovascular cavity: A simple digestive system consisting of a single opening for ingestion and waste excretion.

  • Jellyfish: Use their gastrovascular cavity to digest food and distribute nutrients.

  • Nematodes: Have a more complex gastrovascular cavity for nutrient absorption but also possess a simple one-way alimentary canal.

Mechanical and Chemical Digestion and the Enzymes in the Process

• Mechanical digestion: Physical breakdown of food (e.g., chewing in the mouth).

• Chemical digestion: Involves enzymes that chemically break down food:

  • Amylase: Breaks down carbohydrates into simple sugars.

  • Pepsin: Starts protein digestion in the acidic environment of the stomach.

Glucose Stored as Glycogen

• Excess glucose is stored as glycogen in the liver and muscles for future energy use. Hormones such as glucagon and insulin regulate blood sugar levels and glycogen storage.

Purpose of the Villi

• Villi are finger-like projections in the small intestine that increase the surface area for absorption of nutrients into the bloodstream.

Enzymes and What They Break Down

• Amylase: Breaks down starch and carbohydrates into simple sugars.

• Pepsin: Breaks down proteins into smaller peptides in the stomach.

Digestive Systems of Ruminants and Birds

• Ruminants: Have a four-compartment stomach that helps digest cellulose (e.g., cows, sheep). They ferment food before digestion to extract nutrients.

• Birds (Avian): Possess a crop for storage, a proventriculus for digestion, and a gizzard for grinding food, efficiently processing their diet.

Peristalsis and Alimentary Tract

• Peristalsis: A series of wave-like muscle contractions that moves food through the alimentary tract smoothly, involving smooth muscle layers that contract in sequence.

Function of Each Digestive Organ

• Mouth: Begins mechanical and chemical digestion.

• Esophagus: Transports bolus to the stomach via peristalsis.

• Stomach: Churns food and starts protein digestion with gastric juices.

• Small Intestine: Primary site of digestion and absorption (duodenum, jejunum, ileum).

• Large Intestine: Absorbs water and stores waste before elimination.

Vitamins and Minerals

• Vitamins: Organic compounds crucial for metabolic processes, often acting as coenzymes.

• Minerals: Inorganic elements necessary for various body functions, helping in metabolism and physiological processes.