Predominant constituent of Hyaline membrane is:
**Core Concept**
Hyaline membranes are a hallmark feature of acute respiratory distress syndrome (ARDS) and are composed of cellular debris, fibrin, and surfactant proteins. The formation of hyaline membranes is a critical component of the pathophysiology of ARDS, leading to impaired gas exchange and respiratory failure.
**Why the Correct Answer is Right**
The predominant constituent of hyaline membranes is phospholipid-rich surfactant, which is secreted by type II pneumocytes. The surfactant is composed of phospholipids, particularly phosphatidylcholine, and surfactant proteins A and D. The phospholipids in the surfactant reduce the surface tension of the alveolar fluid, facilitating lung expansion and gas exchange. The disruption of surfactant function due to injury or inflammation leads to the formation of hyaline membranes.
**Why Each Wrong Option is Incorrect**
* **Option A:** Cellular debris is a component of hyaline membranes, but it is not the predominant constituent.
* **Option B:** Fibrin is a component of hyaline membranes, but it is not the primary constituent.
* **Option C:** The correct answer is surfactant, not surfactant-associated proteins.
**Clinical Pearl / High-Yield Fact**
The formation of hyaline membranes in ARDS is a critical step in the pathophysiology of the disease, leading to impaired gas exchange and respiratory failure. The disruption of surfactant function is a key factor in the formation of hyaline membranes.
**Correct Answer: C. Surfactant**