Respiratory System - Lung Physiology

Hemoglobin is a protein in red blood cells responsible for carrying oxygen throughout the body. It binds to oxygen in the lungs and releases it in tissues. This binding is reversible, meaning that oxygen can attach and detach depending on the oxygen concentration.

The oxygen-hemoglobin dissociation curve shows the relationship between the partial pressure of oxygen (Po2) in the blood and the percentage of hemoglobin saturated with oxygen. The curve is S-shaped, indicating that hemoglobin's affinity for oxygen changes with different Po2 levels.

As blood becomes more acidic (lower pH), hemoglobin's affinity for oxygen decreases, causing it to release more oxygen to tissues. This is important because active tissues produce acidic byproducts, making oxygen release more efficient.

The Haldane effect describes how carbon dioxide (CO2) levels influence oxygen transport. Increased CO2 in the blood reduces hemoglobin's affinity for oxygen, favoring oxygen release. This, in turn, promotes CO2 binding to hemoglobin.

Ventilation refers to the movement of air into and out of the lungs. Lung zones are different regions of the lung, each with specific characteristics. The lung zones are distinguished based on their ventilation and blood flow (perfusion) dynamics.

The point on the oxygen-hemoglobin dissociation curve where hemoglobin is 50% saturated with oxygen.

A metabolically important phosphate compound present in blood that affects oxygen-hemoglobin binding. Higher levels of BPG (2,3-biphosphoglycerate) shift the curve to the right, reducing hemoglobin's affinity for oxygen. This is important in conditions like high altitude.

Cooperative binding describes how the binding of one oxygen molecule to hemoglobin increases the affinity for subsequent oxygen molecules to bind.

The binding of oxygen to hemoglobin is affected by various factors, including pH, carbon dioxide concentration, temperature, and 2,3-BPG.

The oxygen-hemoglobin dissociation curve can shift to the right (decreased affinity) or left (increased affinity) depending on various factors.

The partial pressure of oxygen (Po2) is higher at the apex of the lung compared to the base.

The upper region of the lung, where ventilation exceeds perfusion, resulting in a higher Po2.

The lower region of the lung, where perfusion exceeds ventilation, resulting in a lower Po2.

The ratio of carbon dioxide output to oxygen uptake.

Adult tuberculosis preferentially affects the apex of the lung due to its higher Po2, which is a more favorable environment for the bacteria.