Learn: The Mammalian Lung - Ventilation and Gas Exchange

Welcome!You've already explored gas exchange surfaces and learned about Fick’s Law. Today, we'll dive into how the mammalian lung functions during ventilation and gas exchange.

What is Ventilation?Ventilation is the movement of air into and out of the lungs, ensuring a constant supply of oxygen and removal of carbon dioxide. It relies on the coordinated action of muscles and pressure changes.

How Ventilation WorksThe diaphragm and intercostal muscles work together to create pressure changes. During inhalation, the diaphragm contracts and moves down, while external intercostal muscles lift the ribs, increasing chest volume and decreasing pressure. Air is drawn in. During exhalation, these muscles relax, reducing chest volume and increasing pressure, pushing air out.

Structure of the AlveoliThe lungs contain millions of tiny air sacs called alveoli. These have thin walls (one cell thick) and are surrounded by capillaries, providing a large surface area for gas exchange. Oxygen diffuses into the blood, and carbon dioxide diffuses out.

Role of SurfactantAlveoli are coated with a substance called surfactant, which reduces surface tension and prevents them from collapsing during exhalation. This ensures efficient gas exchange.

Gas Exchange and Partial PressureGas exchange occurs due to differences in partial pressure. Oxygen moves from the alveoli (high partial pressure) to the blood (low partial pressure), while carbon dioxide moves in the opposite direction.

Review Time!Great work! You've learned about ventilation, alveoli structure, and gas exchange. Let's test your understanding with a few questions.