Which of the following cells secrete pulmonary surfactant?

KPSC Staff Nurse - 2021

Applied Anatomy

Easy

Appeared in: KPSC Staff Nurse - 2021

Explanation

Type II alveolar cells, also known as Type II pneumocytes, are specialized cuboidal cells interspersed among the Type I cells in the alveolar lining.
Their primary function is to synthesize and secrete pulmonary surfactant, a complex substance composed of phospholipids and proteins.
Surfactant reduces the surface tension of the fluid lining the alveoli, which prevents them from collapsing during exhalation (atelectasis) and increases lung compliance, making it easier to breathe.

Option A: Type I alveolar cells are structurally adapted for gas exchange, not secretion. They are extremely thin, squamous cells that form the vast majority of the alveolar surface area to allow for rapid diffusion of oxygen and carbon dioxide.
Option C: Type III alveolar cells are not a standard, universally recognized classification for alveolar epithelial cells. Some older texts may refer to 'brush cells' as Type III, but their function is uncertain and not related to surfactant. Other sources may mislabel alveolar macrophages as Type III cells.
Option D: Type IV alveolar cells is not a recognized classification in lung histology. The primary epithelial cells are Type I and Type II pneumocytes.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cellular physiology of the respiratory system, specifically the production of pulmonary surfactant as background academic context rather than a clinical decision trigger.
Surfactant deficiency is the underlying cause of Neonatal Respiratory Distress Syndrome (NRDS) in premature infants, whose Type II cells are too immature to produce it in sufficient quantities.
Nursing interventions for at-risk infants include administering antenatal corticosteroids to the mother to accelerate fetal lung maturation and providing exogenous surfactant therapy directly into the infant's lungs post-birth.
In adults, conditions like Acute Respiratory Distress Syndrome (ARDS) can damage Type II cells, leading to decreased surfactant production, alveolar collapse, and severe hypoxemia.

How to Approach the Question

First, identify the key concept in the question stem, which is 'pulmonary surfactant secretion'.
This is a factual recall question requiring knowledge of respiratory histology and physiology.
Access your knowledge about the different cell types within the lung alveoli.
Differentiate the functions: Type I cells are for structure and gas exchange, while Type II cells are secretory.
Evaluate the options based on this differentiation. Type II cells are the only ones that secrete surfactant.
Eliminate options 'Type III' and 'Type IV' as they are not standard classifications for alveolar epithelial cells.

Concept Tested & Keywords

Concept Tested: Cellular physiology of the respiratory system, specifically the production of pulmonary surfactant.
Stem keywords: pulmonary surfactant, secrete, cells, alveolar
Lead-in keywords: Which
Negative lead-in flag: false

QgPASn2i8cylHPjESaP3OV

E6 Histology Inderbir 11e p. 18-20

E6 Nursing Fundamentals Taylor p. 706-708