Biology 1108 Lecture #9: Animal Nutrition & Digestive System

Biology 1108 - Lecture #9 Notes

Chapter 34: Animal Nutrition & Digestive System

Essential Nutrients

  • Essential Amino Acids

    • Definition: Amino acids that cannot be synthesized by the human body.

    • Total: 8 amino acids are essential for human nutrition.

  • Essential Fatty Acids

    • Example: Linoleic Acid

    • Definition: Fatty acids that cannot be produced by humans and must be obtained from the diet.

  • Essential Inorganic Molecules

    • Minerals: Required minerals for various bodily functions.

  • Essential Organic Molecules

Food Sources of Vitamins

  • Vitamin A (Retinol, retinal, Retinoic acid, Beta carotene)

    • Major Functions: Vision, immunity, reproduction, and growth.

    • Deficiency Effects: Blindness, infections, stunted growth.

    • Toxicity Effects: Bone fractures, liver damage, birth defects.

    • Food Sources: Fortified milk, eggs, liver, dark green leafy vegetables, yellow/orange vegetables.

  • Vitamin D (Cholecalciferol)

    • Functions: Bone growth and maintenance, absorption of calcium.

    • Deficiency Effects: Rickets, osteomalacia.

    • Toxicity Effects: Calcium imbalance.

    • Food Sources: Sunlight, fortified milk, fatty fish, eggs, liver.

  • Chromium

    • Functions: Helps insulin move glucose from blood into cells.

  • Vitamin E (Tocopherol)

    • Functions: Antioxidant that protects cell membranes.

    • Deficiency Effects: Red blood cell breakage, nerve damage.

    • Toxicity Effects: Interferes with blood-clotting drugs.

    • Food Sources: Vegetable oils, nuts, seeds, whole grains.

  • Vitamin K (Phylloquinone)

    • Functions: Blood clotting, bone health.

    • Deficiency Effects: Hemorrhage.

    • Toxicity Effects: None reported.

    • Food Sources: Dark leafy greens, cabbage family, liver.

  • Minerals:

    • Calcium

    • Functions: Bone and teeth formation, muscle contraction/relaxation, blood pressure regulation, nerve function.

    • Deficiency Effects: Stunted growth in children, osteoporosis in adults.

    • Toxicity Effects: Diarrhea, interference with absorption of other minerals.

    • Food Sources: Dairy, fish with bones, tofu, greens, legumes, fortified foods.

    • Iron

    • Major Functions: Energy metabolism, part of hemoglobin and myoglobin.

    • Deficiency Effects: Anemia, weakness, headaches.

    • Food Sources: Red meat, fish, poultry, legumes, dried fruits.

    • Zinc

    • Functions: Supports immune function, plays a role in DNA formation and enzyme function.

    • Deficiency Effects: Anemia, weakness, reduced immunity.

    • Food Sources: Meat, shellfish, legumes, seeds, nuts.

Food Processing: Steps

  • Ingestion: Intake of food.

  • Digestion: Breakdown of food into small nutrient molecules, which includes mechanical (tearing/grinding) and chemical (enzymatic hydrolysis) processes.

  • Absorption: Cells take up small nutrient molecules; occurs in the small intestine.

  • Elimination: Removal/release of undigested, unabsorbed nutrient material.

Feeding Types

  • Herbivore: Primarily eat plants.

  • Carnivore: Primarily eat meat.

  • Omnivore: Eat both plants and meat.

  • Decomposer: Break down dead organic material.

  • Scavenger: Consume dead animals.

Feeding Methods

  • Suspension feeder (Filter Feeder): Filter small particles from water.

  • Substrate Feeder (Deposit Feeder): Feed on organic material on a surface.

  • Fluid Feeder: Feed by sucking fluids.

  • Bulk Feeders: Consume large pieces of food.

Digestion

  • Mechanical Digestion :

    • Definition: Physical breakdown of food, occurs in:

    • Mouth (teeth)

    • Stomach

  • Chemical Digestion:

    • Definition: Enzymatic hydrolysis of macromolecules into their basic building blocks, occurs in:

    • Oral cavity

    • Stomach

    • Small Intestine

  • Extracellular Digestion:

    • Occurs in: Gastrovascular cavity or alimentary canal.

  • Intracellular Digestion:

    • Occurs inside cells.

Absorption

  • Nutrient Absorption:

    • Location: Small intestine (jejunum and ileum).

    • Process: Small broken-down nutrients diffuse from the small intestine into capillaries, then from capillaries into lymph, and finally from lymph into individual cells.

Elimination

  • Process: Occurs in the large intestine/rectum, involves the release of undigested nutrients and intestinal mutualistic bacteria.

Monogastric Digestive System: Major Subdivisions

  1. Oral cavity

  2. Pharynx

  3. Esophagus

  4. Stomach

  5. Small intestine

  6. Large intestine

  7. Rectum

Oral Cavity

  • Mechanical Digestion: Teeth help break up food.

  • Chemical Digestion: Saliva contains:

    • Amylase: Enzyme that digests starch into maltose.

    • Mucin: Slippery protein that lubricates food for easier swallowing.

    • Buffers: Neutralizes acid to prevent tooth decay.

    • Anti-bacterial chemicals: Kill bacteria that enter mouth with food.

  • Tongue Function: Forms food into a "Bolus" and pushes it into the esophagus.

Pharynx

  • Location: Back of the throat.

  • Function: Intersection between the digestive and respiratory systems.

  • Epiglottis: Flap of cartilage that helps close the trachea (windpipe) when swallowing, directing food down the esophagus.

  • Peristalsis: Involuntary wave-like muscle contractions to move food along the digestive tract.

Esophagus

  • Structure: Muscular tube leading from pharynx to stomach.

  • Function: Directs bolus down to the stomach.

  • GERD: Results when stomach acid (chyme) moves back up into esophagus.

Stomach

  • Structure: Large muscular sac with three layers of muscle.

  • Rugae: Internal folds allowing for expansion to hold up to 2 L of food/chyme.

  • Acid Chyme: Mixture of food, liquids, and enzymes in the stomach (pH ~ 2).

  • Mucosa: Stomach lining protects from acid chyme.

  • Sphincters: Rings of muscle - cardiac sphincter (between esophagus/stomach) and pyloric sphincter (between stomach and duodenum).

Gastric Juices in Stomach

  • Composition:

    • Mucin: Protects stomach lining.

    • Gastric Lipase: Enzyme that digests/splits lipids.

    • Hydrochloric acid (HCl): Secreted by parietal cells, kills bacteria and denatures proteins.

    • Pepsinogen: Secreted by chief cells, converted to pepsin by HCl; helps digest proteins.

Accessory Organs

  • Pancreas:

    • Produces: Protein digesting enzymes (trypsin, chymotrypsin, carboxypeptidase) and buffers to neutralize acidity in the small intestine.

  • Liver & Gallbladder:

    • Produces Bile: Breaks down fats into smaller droplets making them easier for lipase to digest.

Small Intestine

  • Major role: Location for chemical digestion and absorption.

    • Functions:

    • Chemical digestion through enzymatic hydrolysis.

    • Absorption of nutrients via villi and microvilli.

  • Sections:

    1. Duodenum: Most chemical digestion occurs here.

    2. Jejunum: Absorption of nutrients and water.

    3. Ileum: Absorption of nutrients and water.

Large Intestine

  • Function: Absorbs solid materials and water, reabsorbing about 90% of water passing through.

  • E. coli: Mutualistic bacteria producing Vitamin K.

  • Rectum: Solid waste elimination (feces).

Herbivores vs. Carnivores

  • Herbivores: Have longer intestines due to difficulty digesting cellulose; can’t produce cellulose-digesting enzymes.

  • Carnivores: Shorter intestines due to high protein diet; produce and utilize protein-digesting enzymes.

Digestive Disorders

  • Ulcers: Erosion of the mucous and epithelial lining of the alimentary canal.

  • Constipation: Excess water reabsorption leads to hardened fecal waste.

  • Diarrhea: Decreased water absorption results in watery feces.

  • Appendicitis: Inflammation of the appendix due to infection.

  • Gallstones: Accumulation of hardened cholesterol or calcium deposits in the gallbladder.

  • Gastroesophageal Reflux (Heartburn): Acid chyme backs up into the esophagus.