Which of the following statements about keratinocytes is NOT true?

• A. Keratinocytes play a role in forming a protective barrier against pathogens.
• B. Keratinocytes undergo differentiation as they move toward the skin surface.
• C. Keratinocytes produce melanin, the pigment responsible for skin color.
• D. Keratinocytes are the primary cell type found in the epidermis.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the role of keratinocytes. Keratinocytes are the primary cell type in the epidermis, the outermost layer of the skin. They are responsible for forming a protective barrier against environmental damage, pathogens, and water loss.
2. Step 2: Review the process of keratinocyte differentiation. As keratinocytes move from the basal layer of the epidermis to the surface, they undergo a process of differentiation, eventually forming the stratum corneum, which is composed of dead, flattened cells that provide a tough, protective layer.
3. Step 3: Clarify the role of melanin production. Melanin, the pigment responsible for skin color, is produced by melanocytes, not keratinocytes. Melanocytes transfer melanin to keratinocytes, but keratinocytes themselves do not produce melanin.
4. Step 4: Evaluate the statements provided in the question. Identify which statements accurately describe keratinocytes and which do not. The statement 'Keratinocytes produce melanin, the pigment responsible for skin color' is incorrect because melanin production is the function of melanocytes.
5. Step 5: Conclude that the correct answer is the statement that is NOT true about keratinocytes, which is 'Keratinocytes produce melanin, the pigment responsible for skin color.'