Final answer:
The Stratum granulosum is special because it is where keratinocytes produce large amounts of keratin and keratohyalin, flatten, and undergo terminal differentiation, resulting in their cell membranes thickening and their nuclei disintegrating.
Step-by-step explanation:
Special Characteristics of the Stratum Granulosum
The Stratum granulosum is distinctive due to the transformation that keratinocytes undergo within this layer of the epidermis. As these cells are pushed up from the stratum spinosum, they become flatter and their cell membranes thicken. At this stage, they produce copious amounts of keratin and keratohyalin. Keratin is a fibrous protein that strengthens the cells, while keratohyalin accumulates as lamellar granules, giving the layer its granular look.
This process results in the tough protective layer of the epidermis, contributing to the formation of the stratum lucidum, the stratum corneum, and the accessory structures such as hair and nails. Significantly, the nuclei and other cell organelles disintegrate as the cells die, which emphasizes the terminal differentiation phase keratinocytes experience here.