Digestive System Overview

Digestive System

• Ingestion: Taking food into the body.
• Digestion: Breaking down food.
• Absorption: Taking in nutrients from food.
• Egestion: Eliminating waste.

Digestive Tract

• Peristalsis: Rhythmic contractions in the digestive system that move food.
• Sphincters: Rings of muscles that control the movement of food and prevent backflow.

Digestion Types

• Mechanical: Physical breakdown of food.
  • Chewing: Incisors cut, canines tear/rip, molars grind.
  • Tongue: Moves food.
  • Emulsification: Saliva lubricates and hydrates food.
• Chemical: Breakdown of food by enzymes.
  • Enzymes are produced by glands.

Absorption

• Lacteals: Absorb fats.
• Villi: Increase surface area for absorption.
• Capillaries: Surround villi to absorb nutrients.
• Small Intestine: Villi are located here.

Mouth Digestion

• Physical: Chewing with teeth.
• Chemical: Saliva moistens food and contains amylase, an enzyme that breaks down starch.

Stomach Digestion

• Physical: Storage and mixing of food.
• Chemical:
  • Hydrochloric Acid: Breaks down tissue and kills bacteria.
  • Gastric Fluids: 2 liters released daily by stomach lining.
  • Mucus: Protects stomach lining from acid.
  • Pepsin: Enzyme that begins protein digestion.

Large Intestine

• Concentrates waste by absorbing water.
• Stores feces (undigested/unabsorbed material, water, and bacteria).
• Bacteria produce vitamins.

Additional Notes & Facts

• Pharynx: Tube that directs air to the trachea/lungs or food to the esophagus.
• Liver:
  • Produces bile, an enzyme that helps break down fats in the small intestine.
  • Functions as the body's chemical factory.
• Gallbladder: Stores bile produced by the liver; releases it into the small intestine when needed.
• Pancreas: Produces enzymes for breaking down fats, starches, and sugars. Also produces hormones for digestion.
• Rectum: Stores waste.
• Anus: Sphincter that pushes waste out.

Respiratory System

• Summary: Takes in oxygen for energy and expels carbon dioxide.

Inhalation Order (Breathing - Ventilation)

• Nasal cavity or mouth.
• Pharynx.
• Larynx.
• Trachea.
• Bronchi.
• Bronchioles.
• Alveoli.

Exhalation Order

• Reverse of inhalation order

Inhalation Functions

• Diaphragm: Contracts (flattens and moves down).
• Intercostal Muscles: Contract, moving rib cage up and out.
• Thoracic Cavity: Enlarges.
• Lung Pressure: Decreases, air rushes in.

Exhalation Functions

• Diaphragm: Relaxes and moves up.
• Intercostal Muscles: Relax, moving rib cage down and in.
• Thoracic Cavity: Decreases in volume.
• Lung Pressure: Increases, air is forced out.

Air Processing

• Cilia: Small hairs in the nasal cavity and airways.
  • Sweep debris and mucus up the trachea to be coughed, swallowed, or spit out.
• Mucus: Coats cilia and lung tissue.
  • Traps dust and bacteria.
  • Allows gases to dissolve for movement through membranes.
• Blood Vessels: Warm air to body temperature.

Gas Exchange

• External Respiration: Oxygen diffuses from alveoli into blood.
• Hemoglobin: Oxygen binds to hemoglobin in red blood cells for transport.
• Carbon Dioxide: Diffuses from blood into alveoli.