4 - DIGESTIVE SYSTEM

• What are the five categories of nutrients in animal feed?

  Water, protein, carbohydrates, minerals, vitamins
• What is the primary function of nutrients in animal feed?

  Used by the animal for growth and production
• What does an animal's diet provide?

  • Chemical energy for ATP production
  • Organic building blocks for synthesizing molecules
  • Essential nutrients from dietary sources
• How many classes of essential nutrients are there?

  Four classes
• What are essential amino acids and where are they found?

  Complete proteins in meat, eggs, and cheese
• What are essential fatty acids?

  Unsaturated fatty acids obtained from diet
• Why are vitamins important in the diet?

  They are organic molecules required in small amounts
• What are minerals in the context of nutrition?

  Simple inorganic nutrients usually required in small amounts
• What is the process of digestion in a hydra?

  1. Begins in the gastrovascular cavity
  2. Completed intracellularly after engulfing food
  3. Specialized cells of the gastrodermis digest food
• What is ingestion?

  The process of taking in food
• What is digestion?

  Breaking down food into absorbable molecules
• How does mechanical digestion aid in digestion?

  Increases the surface area of food
• What is chemical digestion?

  Splitting food into small molecules for absorption
• What is absorption in the digestive process?

  Involves nutrients entering the bloodstream
• What is transport in the context of digestion?

  Moving absorbed nutrients throughout the body
• What is assimilation in digestion?

  Using absorbed food for energy and growth
• What is elimination in the digestive process?

  Excretion of undigested food through feces
• What are the types of digestion in animals?

  • Intracellular digestion: Engulfing food by phagocytosis
  • Extracellular digestion: Breakdown of food outside cells
• What is the function of specialized compartments in digestion?

  Reduce risk of digesting own cells
• What are herbivores?

  Animals that depend on plants for nutrition
• What are carnivores?

  Animals that depend on other animals for food
• What are omnivores?

  Organisms that eat both plants and animals
• What are the types of feeding modes in animals?

  • Filter feeding: Nutrients from water particles
  • Deposit feeding: Nutrients from soil particles
  • Fluid feeding: Nutrients from fluids of organisms
  • Bulk feeding: Eating whole organisms
• What is a complete digestive tract?

  A digestive tube with two openings
• What does the mammalian digestive system consist of?

  An alimentary canal and accessory glands
• What are the mammalian accessory glands?

  Salivary glands, pancreas, liver, gallbladder
• Describe the digestive process in an earthworm.

  1. Food sucked in by muscular pharynx
  2. Stored and moistened in the crop
  3. Mechanical digestion in the gizzard
  4. Digestion and absorption in the intestine
• Describe the digestive process in a grasshopper.

  1. Digestive chambers: foregut, midgut, hindgut
  2. Food moistened and stored in the crop
  3. Most digestion occurs in the midgut
  4. Gastric cecae function in digestion and absorption
• Describe the digestive process in birds.

  1. Crop for storing food
  2. Stomach and gizzard for mechanical digestion
  3. Chemical digestion and absorption in the intestine
• How long does food take to pass down the esophagus?

  5–10 seconds
• How long does food spend in the stomach?

  2–6 hours
• How long does digestion and absorption occur in the small intestine?

  5–6 hours
• What happens to undigested material in the large intestine?

  It passes through and is expelled as feces
• What is the role of teeth in digestion?

  • Bite and grind food into smaller pieces
  • Increase surface area for digestion
• What does the tongue do during digestion?

  Mixes food with saliva to form a bolus
• What is the function of salivary glands?

  Produce saliva containing amylase for starch digestion
• How does water aid in digestion?

  Helps dissolve substances in food
• What is the role of mucus in digestion?

  Helps bind chewed food to form a bolus
• Describe the swallowing process.

  1. Pharynx connects to trachea and esophagus
  2. Sphincter seals off esophagus
  3. Swallowing reflex triggered by food bolus
  4. Epiglottis prevents food from entering trachea
  5. Esophageal sphincter relaxes for bolus passage
• What is the pH of gastric juice and why is it important?

  Low pH of about 2 kills bacteria