Which of the following type of cells are LEAST affected by Radiation ?

PGIMER Chandigarh NO - 2015

Pathology & Genetics

Easy

Appeared in: PGIMER Chandigarh NO - 2015

Explanation

Heart muscle cells (cardiomyocytes) are highly resistant to radiation because they are terminally differentiated, meaning they are fully specialized and do not undergo mitosis (cell division) in adults.
Radiation therapy primarily works by damaging the DNA of rapidly dividing cells, preventing them from replicating.
Since heart muscle cells do not divide, they are less vulnerable to this mechanism of damage, making them one ofthe most radioresistant tissues in the body.
This principle is explained by the Law of Bergonié and Tribondeau, which links high radiosensitivity to high mitotic activity and low cell differentiation.

Option A: Hair follicle cells are incorrect because they divide very rapidly to facilitate continuous hair growth. This high mitotic rate makes them highly sensitive to radiation, which is why alopecia (hair loss) is a common side effect of radiation therapy.
Option B: Cancer cells are incorrect as they are, by definition, cells that undergo rapid and uncontrolled division. This high rate of proliferation makes them a primary target for radiation therapy, which aims to destroy them.
Option D: GI muscle (smooth muscle) is relatively radioresistant due to its low turnover rate. However, it is not as terminally differentiated as cardiac muscle. Furthermore, the lining of the GI tract (mucosa) is extremely radiosensitive. Between the two muscle types, heart muscle is considered more resistant.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cellular Radiosensitivity as background academic context rather than a clinical decision trigger.
Understanding radiosensitivity is crucial for nurses managing patients undergoing radiation therapy to anticipate and manage side effects.
Common side effects like hair loss (alopecia), skin redness (erythema), and gastrointestinal issues (mucositis, diarrhea) are direct results of radiation affecting rapidly dividing cells in those tissues.
What if? If a patient receives radiation to the chest for lung or breast cancer, the nurse must monitor for long-term cardiac complications (cardiotoxicity). Even though heart muscle is resistant, high cumulative doses can cause fibrosis and damage over months or years, highlighting the need for careful treatment planning and long-term follow-up.

How to Approach the Question

First, analyze the question and identify the key term 'LEAST'. This indicates you are looking for the most radioresistant cell type.
Recall the basic principle of how radiation affects cells: it is most damaging to cells that divide frequently and are not fully specialized (Law of Bergonié and Tribondeau).
Evaluate each option based on this principle:
Hair follicles and Cancer cells: Both are known for rapid cell division, so they are highly sensitive.
Heart muscle and GI muscle: Both are muscle tissues and generally have low division rates, making them resistant.
Compare the two resistant options. Heart muscle cells are terminally differentiated (post-mitotic), meaning they do not divide at all. This makes them more resistant than GI smooth muscle.

Concept Tested & Keywords

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