Evolution of Respiratory Systems

Introduction

• Focus on an unnamed ancient organism crucial to the evolution of vertebrates.
• Existed around 380 million years ago.
• Known for achieving the milestone of breathing air.

Evolution of Breathing

• Early life evolved in water, using simple diffusion to obtain oxygen.
• Diffusion is inefficient for larger organisms requiring more oxygen.
• Early life forms evolved circulatory and respiratory systems to move oxygen internally.

Gills to Lungs

• Gills were the initial respiratory structures but worked only in water.
• Earth's changing environment led to a necessity for breathing air.
• A lobe-finned fish evolved lungs, allowing it to breathe air and overcome the limitations of gills.

Development of Respiratory and Circulatory Systems

• Lungs enabled larger, more diverse life forms.
• Vertebrates evolved additional structures: ribs, trachea, diaphragm, forming a respiratory system.
• Respiratory and circulatory systems work together for cellular respiration.

Breathing Mechanics

• Breathing combines diffusion and bulk flow.
• Bulk flow moves large amounts of oxygen rapidly.
• Oxygen diffuses quickly across cell membranes due to proximity to blood vessels.

Anatomy of Breathing

• Lungs act like pumps but need muscle assistance (diaphragm and intercostal muscles).
• Diaphragm and ribs facilitate lung expansion and contraction.
• Breathing involves changes in lung pressure relative to external air.

Conducting and Respiratory Zones

• Conducting Zone: Air passageways including nose and sinuses, warming and moistening air.
• Respiratory Zone: Includes bronchioles, alveolar ducts, and sacs where gas exchange occurs.
• Alveoli provide extensive surface area for gas exchange with blood.

Physiology of Gas Exchange

• Alveoli facilitate oxygen and carbon dioxide exchange through diffusion.
• Respiratory and circulatory systems work in tandem to maintain efficient respiration.

Conclusion

• Diffusion and bulk flow are fundamental to respiration.
• Modern respiratory systems have evolved over 400 million years.
• Summary of the mechanics of diffusion, bulk flow, and the anatomy of respiratory systems.