Respiration

•  Gas Exchange

  • the process of exchanging one gas to another

  
• Factors Affecting Gas Exchange 

  •  Surface area
  • The greater the area, the more molecules can cross the surface at once
  • Gas concentration gradient across the respiratory surface
  • The steeper the gradient, the faster diffusion proceeds
  • Respiratory proteins steepen the gradient in many animals 
• The respiratory surface is made up of the alveoli and capillary walls. The walls of it may share the same membrane.
• Respiratory Medium

  Respiratory medium is either water or air

  • Water is 50 times more viscous than air
  • Moving water over a respiratory surface requires more effort
  • A volume of water holds less O2 than the same volume of air
  • Air is a reliable source
  • Oxygen concentration in aquatic environments varies widely 
• Gills

  • the main respiratory organ of fishes and aquatic organisms
  • Gas exchange in it is called countercurrent exchange
• Countercurrent exchange in gills ensures efficient oxygen uptake by maintaining a concentration gradient. Blood flows through the lamellae in the opposite direction to water passing over the gills. As oxygen-deficient blood enters the gills, it encounters oxygen-poor water that still has slightly more oxygen, allowing diffusion into the blood. As blood moves through the gills, it continuously absorbs oxygen from water with increasingly higher oxygen levels. This process ensures that even oxygen-rich blood leaving the gills meets the most oxygen-rich water, maximizing gas exchange efficiency.

  
• Lungs

  • contains alveoli that exchanges gas from blood via diffusion

  
•  The Human Respiratory System

   Additional roles of the respiratory system

  – Air moves past vocal cords to enable speech

  – Inhaled molecules stimulate olfactory receptors in the nose

  – Contributes to acid-base balance

  – Contributes to maintenance of body temperature 
• PHASES/MECHANISM OF RESPIRATION

  • Pulmonary Ventilation – The movement of air into and out of the lungs to refresh the gases.
  • External Respiration – Oxygen diffuses from the lungs into the blood, while carbon dioxide moves from the blood to the lungs.
  • Transport of Respiratory Gases – The cardiovascular system transports oxygen from the lungs to body tissues and carbon dioxide from tissues to the lungs via the blood.
  • Internal Respiration – Oxygen diffuses from the blood into tissue cells, while carbon dioxide moves from tissue cells into the blood.
• Respiration

  • Supply body cells with oxygen from the environment
  • Deliver waste carbon dioxide from cells to the environment