When a needle is inserted into the forearm, which sequence correctly represents the order in which the epidermal layers are pierced, from superficial to deep?

• A. Stratum granulosum, stratum corneum, stratum spinosum, stratum basale
• B. Stratum spinosum, stratum corneum, stratum granulosum, stratum basale
• C. Stratum basale, stratum spinosum, stratum granulosum, stratum corneum
• D. Stratum corneum, stratum granulosum, stratum spinosum, stratum basale

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the structure of the epidermis, which is the outermost layer of the skin. The epidermis is composed of several layers arranged from superficial (outermost) to deep (innermost). These layers are: stratum corneum, stratum granulosum, stratum spinosum, and stratum basale.
2. Step 2: Recall the function and characteristics of each layer. The stratum corneum is the outermost layer, consisting of dead, keratinized cells that provide a protective barrier. The stratum granulosum contains cells that are undergoing keratinization. The stratum spinosum is composed of living keratinocytes connected by desmosomes, and the stratum basale is the deepest layer, where cell division occurs to replenish the epidermis.
3. Step 3: When a needle is inserted into the forearm, it pierces the epidermal layers in order from superficial to deep. This means the needle first penetrates the stratum corneum, followed by the stratum granulosum, then the stratum spinosum, and finally the stratum basale.
4. Step 4: Compare the given sequences in the problem to identify the correct order. The correct sequence is: Stratum corneum, stratum granulosum, stratum spinosum, stratum basale.
5. Step 5: Understand why the other sequences are incorrect. For example, the sequence 'Stratum granulosum, stratum corneum, stratum spinosum, stratum basale' is incorrect because the stratum corneum is the outermost layer and must be pierced first. Similarly, the sequence 'Stratum spinosum, stratum corneum, stratum granulosum, stratum basale' is incorrect because the stratum spinosum is deeper than the stratum corneum and stratum granulosum.