MCAT Basics (from MedSchoolCoach) The Respiratory System
Jun 5, 2025
Explore the fascinating mechanics of the respiratory system! Discover how the diaphragm and intercostal muscles work together to facilitate breathing. Learn about the vital roles of gas exchange and how pulmonary surfactant prevents alveolar collapse. Dive into the upper and lower respiratory tract structures, from the nose to the alveoli, and understand how pressure changes drive airflow. Uncover how breathing regulates blood pH and the innovative ways our body filters particles, all while managing thermoregulation!
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Two-Part Respiratory Anatomy
- The respiratory tract splits into upper (nose, sinuses, larynx, trachea) and lower (bronchi, bronchioles, alveoli) sections with distinct roles.
- Alveoli are tiny, thin-walled sacs where gas exchange occurs and capillaries surround them for diffusion.
Breathing Driven By Pressure Changes
- Diaphragm contraction flattens the dome and increases chest cavity volume to lower intrapulmonary pressure.
- Air flows from higher atmospheric pressure into lungs down that pressure gradient during inhalation.
Surfactant Prevents Alveolar Collapse
- Surface tension from the water lining alveoli tends to collapse them, and smaller alveoli feel more pressure per Laplace's law.
- Pulmonary surfactant (≈90% lipids) reduces surface tension to prevent alveolar collapse.