Advanced Dental Admission Test (ADAT)

What characterizes the stratum corneum in terms of cellular composition?

1. Presence of collagen fibers

2. Presence of flattened, pyknotic cells

3. Presence of keratin-rich cells

4. Presence of open pores

The correct answer is: Presence of flattened, pyknotic cells

The stratum corneum is the outermost layer of the skin, primarily characterized by its composition of keratinized cells. It consists mainly of flattened, dead cells that have undergone a process known as keratinization, which is the accumulation of the protein keratin. This process leads to the formation of the flattened, pyknotic cells that define this layer. Pyknotic cells are cellular remnants that have condensed nuclei, indicating that they have lost metabolic activity and are in the final stages of apoptosis (programmed cell death). The primary function of the stratum corneum is to provide a protective barrier. The keratin-rich composition plays a crucial role in maintaining moisture levels while also providing resistance to mechanical injury and microbial invasion. These flattened cells make up the impermeable barrier that prevents water loss from the underlying layers of skin. While collagen fibers are important for the structural integrity of other layers of the skin such as the dermis, they are not present in the stratum corneum. Likewise, open pores are not characteristic of the stratum corneum itself; rather, pores are openings associated with hair follicles or sweat glands. Therefore, the presence of flattened, pyknotic cells accurately describes the cellular composition of