What do the small granules in the stratum granulosum primarily contain?

The small granules found in the stratum granulosum primarily contain keratin. This layer of the epidermis is key in the process of keratinization, where the cells begin to lose their nuclei and cytoplasmic organelles, gradually transforming into hardened, keratin-rich cells. Keratin is a fibrous protein that provides structure, resilience, and water-resistance to the skin, making it vital for protective functions.

In the stratum granulosum, the granules themselves, known as keratohyalin granules, play a crucial role in the aggregation of keratin filaments and contribute to the formation of the skin's outer barrier. As cells move up from the deeper layers of the epidermis, they accumulate keratin and the granules help in binding the keratin together, which is essential for maintaining skin integrity.

Other choices, while important in different contexts, do not correctly capture the primary content of the granules in this specific layer. Melanin is predominantly found in the stratum basale and stratum spinosum, collagen is mainly associated with the dermis, and elastic fibers are also more prominent in the dermal layer, used for skin elasticity. Thus, the presence of keratin granules specifically