Final answer:
The stratum granulosum is primarily involved in keratin synthesis. It is known for the production of keratin and keratohyalin as keratinocytes become flatter and generate a grainy appearance, contributing to the skin's barrier function.
Step-by-step explanation:
The stratum granulosum, or granular layer, is a layer of the epidermis primarily involved in keratin synthesis. It is situated above the stratum spinosum and below the stratum lucidum (when present). In this layer, keratinocytes become flatter and more compact, producing large amounts of keratin and keratohyalin. This production gives the cells a grainy appearance and helps to form a part of the skin's barrier function. The keratin and keratohyalin, along with thickening of the cell membranes, contribute to the formation of the next layers, the stratum lucidum and the stratum corneum.
Melanin production primarily occurs in the stratum basale, where melanocytes are found, and not in the stratum granulosum. Desquamation, the shedding of dead skin cells, mainly occurs in the more superficial stratum corneum. Cellular respiration occurs in all living cells, including keratinocytes of the epidermis, but it is not a characteristic feature of the stratum granulosum.