Question

Which of the following layers is the outermost layer of the skin with dead cells?
A. Stratum lucidum
B. Stratum corneum
C. Stratum spinosum
D. Stratum granulosum

Answer 1

The epidermis provides a protective barrier that repels water, blocks pathogens, and regulates body temperature. The main layers of the epidermis are: stratum corneum, lucidum layer, seed layer, spinosum layer, germ layer (also called basal layer). Outermost layer of our skin is the epidermis, which is the same layer that we see with our eyes.

Complete answer:
Option A Stratum lucidum: Stratum lucidum is a layer that gets its name from the transparent appearance it shows under a microscope. This layer is easily found only on certain hairless parts of our body, namely the palms and soles of the feet. That is, the places where our skin is usually the thickest. It is not the outermost layer of skin.
Hence option A is not correct.
Option B Stratum corneum: The cells of the cornea act as a hard protective layer against environmental trauma, such as abrasion, light, heat, chemicals, and microorganisms. The cells of the stratum corneum are also surrounded by lipids or fats which help repel water. The stratum corneum is the outermost layer of the epidermis, which is made up of thin layers of dead keratinocytes that are constantly being lost. Since the stratum corneum is the outermost layer of the skin.
So, option B is the correct answer.
Option C Stratum spinosum: From the basal layer, keratinocytes migrate into the spinosum layer, a layer so called because its cells are globular cells. The spinosum layer is partly responsible for the strength and flexibility of the skin.
Since this is not the outermost layer, option C is not correct.
Option D Stratum granulosum: Stratum granulosum is a thin layer of cells in the epidermis above stratum spinosum and below the stratum corneum. Keratocytes migrate from the lower spinosum layer to become granulosa cells in this layer.
Since this layer is not the outermost layer, option D is also not correct.

Therefore, Option B. The stratum corneum is the correct answer.

Note:
Millions of these new cells appear every day in the basal layer. The newly created cells will grow older cells into the upper layers of the epidermis over time. As these old cells rise to the surface, they change shape, nuclear makeup, and chemistry. These changes partly give the different classes of the population distinct characteristics.