A surfactant is a combination of

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2022

Explanation

Pulmonary surfactant is a complex mixture of several phospholipids, proteins, and ions.
The primary components are lipids (specifically phospholipids like dipalmitoylphosphatidylcholine), which make up about 90% of its weight and are responsible for reducing surface tension.
Proteins account for about 10% and are crucial for spreading the lipid film and for immune defense.
Carbohydrates are present in smaller amounts, often as part of glycoproteins.
Ions, such as calcium, are essential for the proper structure and function of the surfactant complex.

Option B: This option incorrectly includes vitamins. Vitamins are essential micronutrients for overall body function but are not a structural component of the pulmonary surfactant mixture.
Option C: This option incorrectly includes hormones. Hormones are signaling molecules that regulate physiology and behavior, but they are not secreted as part of the surfactant complex in the alveoli.
Option D: This option includes 'fluid,' which is too general. While surfactant is suspended in the thin layer of fluid lining the alveoli, the fluid itself is not a specific biochemical component of the surfactant mixture. Option A is more precise by naming 'ions' as a key component.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Composition of Pulmonary Surfactant as background academic context rather than a clinical decision trigger.
A deficiency in surfactant is the primary cause of Neonatal Respiratory Distress Syndrome (NRDS), especially in premature infants born before their lungs are mature enough to produce adequate amounts.
Surfactant can also be inactivated in adults with Acute Respiratory Distress Syndrome (ARDS) due to inflammation, infection, or meconium aspiration.
Surfactant replacement therapy, where exogenous surfactant is administered directly into the lungs, is a life-saving intervention for premature infants with NRDS.

How to Approach the Question

Identify the core concept of the question, which is the chemical composition of surfactant.
Recall the primary function of surfactant: to reduce surface tension in the alveoli.
Remember that surfactant is a complex biological mixture. Think about the major classes of biomolecules: lipids, proteins, and carbohydrates.
Evaluate each option based on this knowledge.
Option A includes phospholipids (a specific type of lipid), proteins, carbohydrates, and ions. This is the most complete and accurate description.
Eliminate options containing incorrect components like vitamins (Option B) or hormones (Option C).

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 2A p. 50-52

E6 Obstetrics Williams p. 24-43

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