Animal Nutrition Vocabulary

Animal Nutrition - Ch. 16

Lecture Objectives

  • Types of Feeders
  • Four Stages of Food Processing
  • Human Alimentary Canal (Digestive Tub)

Why We Eat

  • Cells need energy.
  • Cells/tissues break down food and build molecules: monomers to polymers (organic/macromolecules).
  • Essential nutrients are required.

Types of Feeders

  • Suspension Feeders and Filter Feeders (e.g., Baleen whales).
  • Substrate Feeders (e.g., Caterpillar feeding on feces).
  • Bulk Feeders.
  • Fluid Feeders.

Four Stages of Food Processing

  1. Ingestion
  2. Digestion
    • Mechanical digestion
    • Chemical digestion (enzymatic hydrolysis)
  3. Absorption: Nutrient molecules enter body cells.
  4. Elimination: Undigested material is expelled.

Incomplete Digestive System

  • Mouth
  • Tentacles
  • Food particles are engulfed and digested.
  • Food particles are broken down.
  • Digestive enzymes are released.
  • Epidermis and Gastrodermis layers are involved.

Human Alimentary Canal (Complete Digestive Tract)

  • Components:
    • Oral cavity (Mouth)
    • Pharynx
    • Esophagus
    • Stomach
    • Small intestine
      • Duodenum of small intestine
    • Large intestine
    • Rectum
    • Anus
  • Accessory Organs:
    • Salivary glands
    • Liver
    • Gallbladder
    • Pancreas

Oral Cavity

  • Functions:
    • Masticate food (chewing).
    • Salivary glands:
      • Water
      • Mucus
      • Buffers
      • Calcium
      • Antibacterial substances
      • Amylase & Lysozyme: Form a bolus (a rounded mass of food).

Tongue and Pharynx

  • The tongue manipulates the bolus of food
  • Pharynx directs bolus to esophagus.
  • Glottis and Larynx are involved in swallowing.
  • Epiglottis blocks the trachea.
  • Esophageal sphincter contracts to prevent food from re-entering the pharynx.
  • Peristalsis: Wave-like muscle contractions that move the bolus down the esophagus to the stomach.

Stomach

  • Gastric glands are located in gastric pits on the interior surface of the stomach.
  • Epithelium contains:
    • Mucous cells: Secrete mucus to protect the stomach lining.
    • Chief cells: Secrete pepsinogen (inactive form of pepsin).
    • Parietal cells: Secrete HCl (hydrochloric acid).
      • HCl: Provides an acidic environment (low pH) that converts pepsinogen to pepsin (active enzyme for protein digestion).
      • H^+ and Cl^- are secreted.
  • Pepsin: Enzyme that breaks down proteins.
  • Sphincters regulate the entry and exit of food from the stomach.

Small Intestine (Duodenum)

  • The stomach contents (chyme) are released into the duodenum.
  • Duodenum: First 10 inches of the small intestine; where most digestion occurs.
  • Connected to liver, gallbladder, and pancreas.

Intestinal Wall

  • Muscle layers facilitate movement and mixing of chyme.
  • Large circular folds increase surface area.
  • Villi: Finger-like projections that increase surface area for nutrient absorption.

Nutrient Absorption in Small Intestine

  • Villi are covered with epithelial cells that have microvilli (brush border) on their apical (lumenal) surface.
  • Microvilli increase surface area for absorption.
  • Nutrient absorption occurs across epithelial cells.
  • Blood capillaries within villi transport nutrients to the liver.
  • Lacteal (lymph vessel) in villi absorbs fats.

Large Intestine

  • Components:
    • Cecum
    • Appendix
    • Ascending portion of colon
    • Small intestine connects to the cecum.
  • Functions:
    • Absorb water and electrolytes.
    • Produce and absorb vitamins.
    • Form and move feces to the rectum for elimination.
  • Contractions increase pressure to move stool to the rectum.
  • Feces are held in the rectum until elimination.