Respiratory System Overview

Respiratory System Structure and Function

• The respiratory system facilitates gas exchange, taking in oxygen and releasing carbon dioxide.
• Humans have a complex system with a nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and lungs.
• The lungs contain alveoli, tiny air sacs where gas exchange occurs.
• The average person breathes in and out about 15 times per minute.

Respiratory System Function

• The average person moves over 10,000 liters of air in and out of their lungs each day.
• The right lung is slightly larger than the left.
• The highest recorded sneeze speed is 165 km/h.
• The surface area of the lungs is about the size of a tennis court.
• Women and children have a faster breathing rate than men.
• Yawning draws more oxygen into the lungs.

Respiration in Different Organisms

• All living things need to respire.
• Respiration involves taking in oxygen and releasing carbon dioxide.
• Organisms like flatworms utilize their body walls for gas exchange.
• Fish use gills for respiration in water.
• Terrestrial arthropods use tracheae for respiration.
• Mammals use lungs for oxygen and carbon dioxide exchange.

Cellular Respiration

• Living organisms need a respiratory system for cellular respiration, a process that produces ATP (energy).
• Cellular respiration uses glucose and oxygen to produce energy, releasing carbon dioxide and water as byproducts.
• The chemical equation for cellular respiration is C₆H₁₂O₆ + 6O₂ → 6H₂O + 6CO₂ + 36ATP.

Gas Transfer in Animals with Lungs

• Gas transfer in animals with lungs (like humans) occurs in three phases:
  • Breathing
  • Gas Transport
  • Gas Exchange in Cells
• Breathing involves the intake of air with oxygen and the expulsion of air with carbon dioxide.
• The circulatory system transports gases throughout the body.
• Gases are exchanged in the microscopic alveoli within the lungs.

Diffusion

• Diffusion is the passive movement of particles from an area of high concentration to an area of low concentration.
• Diffusion plays a critical role in the movement of respiratory gases in the body.
• Respiratory gases diffuse across thin, moist membranes.
• The concentration gradient of oxygen and carbon dioxide facilitates the diffusion process.

Respiratory Surfaces

• Respiratory surfaces must be thin and moist to allow the efficient diffusion of gases.
• A large surface area is essential for maximum gas diffusion.
• Concentration gradients (high to low concentrations) within and around respiratory surfaces are pivotal for gas movement.
• Single-celled organisms rely solely on their cell membranes for respiration.

Alternative Respiratory Systems

• Larger organisms need a gas exchange and transport system because diffusion is insufficient.
• Some organisms breathe through their skin (like earthworms, frogs, and toads) due to a higher ratio of respiratory surface to body size.
• Gills are used by aquatic vertebrates to absorb oxygen from water.
• Tracheal systems, seen in terrestrial arthropods (like insects), involve branching tubes to transport gases directly to cells.