Final answer:
In the stratum granulosum, keratin intermediate filaments contribute to the production of large amounts of keratin and keratohyalin, causing the keratinocytes to appear grainy. These proteins remain after the cells die, ultimately forming part of the skin's upper layers and accessory structures.
Step-by-step explanation:
In the stratum granulosum, keratin intermediate filaments undergo significant changes as keratinocytes are pushed upward from the stratum spinosum. As keratinocytes move into the stratum granulosum, they become flatter, their cell membranes thicken, and they produce large quantities of keratin and keratohyalin. Keratin is a fibrous protein that, along with keratohyalin, accumulates in lamellar granules within the cells. These proteins fill the keratinocytes, giving them a grainy look and forming a large part of their mass. Ultimately, the nuclei and other cell organelles disintegrate as the keratinocytes die, and these fibrous proteins are left behind to contribute to the formation of the stratum lucidum, the stratum corneum, and the accessory structures of hair and nails.