Surfactant is secreted by?

Appeared in: VSSC Nursing Officer - 2021

Explanation

Pulmonary surfactant is secreted by Type II alveolar cells (pneumocytes).
Histologically, Type II pneumocytes are classified as simple cuboidal epithelial cells.
These cuboidal cells contain secretory granules called lamellar bodies where surfactant is assembled.
Their primary function is to produce and release surfactant, which reduces alveolar surface tension and prevents lung collapse during expiration.

Option A: This is a general term. The alveolar epithelium is composed of both Type I (squamous) and Type II (cuboidal) cells. Only the Type II cells secrete surfactant, making this answer less precise than 'Cuboidal epithelium'.
Option C: Simple squamous epithelium in the alveoli refers to Type I pneumocytes. These cells are extremely thin to facilitate gas exchange and do not secrete surfactant.
Option D: Keratinized epithelium is a protective, waterproof layer of tissue found in the epidermis of the skin. It is not present in the respiratory system, especially not in the delicate alveoli.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Histology of Lung Alveoli and Surfactant Secretion as background academic context rather than a clinical decision trigger.
A deficiency in surfactant, common in preterm infants, leads to Respiratory Distress Syndrome (RDS), where the alveoli collapse, causing severe breathing difficulty.
The administration of antenatal corticosteroids to mothers at risk of preterm delivery stimulates the maturation of fetal Type II pneumocytes, increasing surfactant production and reducing the risk and severity of RDS in the newborn.
Exogenous surfactant can be administered directly into the lungs of premature infants to compensate for the deficiency, a life-saving intervention in neonatal intensive care.

How to Approach the Question

First, identify the key term in the question: 'surfactant'. Recall its function in the lungs, which is to reduce surface tension.
Next, link this function to the specific cell responsible for its production. Remember that the alveoli have two main cell types: Type I and Type II pneumocytes.
Differentiate the functions: Type I cells are for gas exchange, and Type II cells are secretory.
Associate the secretory cell (Type II pneumocyte) with its histological shape. Secretory cells are typically cuboidal or columnar, not flat (squamous). Therefore, Type II cells are cuboidal.
Evaluate the options. 'Cuboidal epithelium' specifically describes the surfactant-secreting cells. 'Alveolar epithelium' is too general, and 'Squamous epithelium' is incorrect. 'Keratinized epithelium' is irrelevant to the lungs.

Concept Tested & Keywords

Q9njiR2v-cVrpqUgjtntnY

E6 Obstetrics Williams p. 24-43

E6 Histology Inderbir 11e p. 18-20

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Attempt every question from this paper in a timed mock, then review the full solution for each one.