Question

When someone is standing, gravity stretches the bottom of the lung down toward the floor to a greater extent than the top of the lung. What implication could this have on the flow of air in the lungs? Where does gas exchange occur in the lungs?

Short answer

Gas exchange occurs in the lungs between the alveoli and capillaries.

Step-by-step solution

Step 1. Introduction

Mammalian lungs are located in the thoracic cavity where they are surrounded and protected by the rib cage, intercostal muscles, and bound by the chest wall. The bottom of the lungs is contained by the diaphragm, a skeletal muscle that facilitates breathing. Breathing requires the coordination of the lungs, the chest wall, and most importantly, the diaphragm.

Step 2. Explanation

• The lung is particularly susceptible to changes in the magnitude and direction of gravitational forces.
• When someone is standing, the pleural pressure gradient leads to increased ventilation further down in the lung.
• As a result, the intrapleural pressure is more negative at the base of the lung than at the top, and more air fills the bottom of the lung than the top.
• Gas exchange occurs in the lungs between the alveoli and capillaries.