Hair colour in Humans turns white due to the absence of which of the following pigments?

Appeared in: RRB Staff Nurse Kolkata-2015

Explanation

Melanin is the pigment responsible for the color of hair, skin, and eyes.
It is produced by specialized cells called melanocytes, which are located at the base of hair follicles.
The process of hair turning white, known as canities or achromotrichia, occurs when these melanocytes stop producing melanin.
A complete absence of melanin production results in white hair, while a reduction in production leads to gray hair.

Option B: Melatonin is a hormone, not a pigment. Its primary function is to regulate the body's circadian rhythms, or the sleep-wake cycle.
Option C: Bilirubin is a yellow pigment that results from the breakdown of heme in red blood cells. It is processed by the liver and excreted in bile.
Option D: Biliverdin is a green pigment that is an intermediate in the breakdown of heme to bilirubin. It is responsible for the greenish color sometimes seen in bruises.

Visual 1: Diagram - A cross-section of a hair follicle showing the location of melanocytes and the process of melanin being deposited into the hair shaft. This helps visualize how color is incorporated into hair.
Visual 2: Chart - A chart illustrating the different types of melanin (eumelanin and pheomelanin) and the resulting hair colors from their various combinations and concentrations.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The role of pigments in determining human hair color as background academic context rather than a clinical decision trigger.
Premature graying of hair can sometimes be a sign of underlying health issues, such as vitamin B12 deficiency, thyroid disease, or vitiligo.
Nurses should be aware that certain medications or nutritional deficiencies can affect hair pigmentation, and this can be an important clinical observation.
What if? If a young patient presents with sudden and rapid graying of hair, a nurse should consider it a potential clinical sign that warrants further investigation for underlying systemic conditions, rather than just a cosmetic issue.

How to Approach the Question

First, identify the key terms in the question: 'hair colour', 'turns white', and 'absence of pigment'.
The question is asking for the specific pigment that gives hair its color.
Evaluate each option based on your knowledge of basic human biology.
Recall or deduce that melanin is the primary pigment for hair, skin, and eye color.
Eliminate the other options by identifying their functions: Melatonin is a sleep hormone, and Bilirubin/Biliverdin are bile pigments related to red blood cell breakdown.

Concept Tested & Keywords

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