What is the primary purpose of the stratum granulosum?

The primary purpose of the stratum granulosum, which is a layer of the epidermis situated above the stratum spinosum and below the stratum lucidum, is to produce keratin. This layer is crucial in the process of keratinization, where keratinocytes (the main cells in the epidermis) move up through the layers of the skin and undergo changes that lead to the synthesis of keratin, a key structural protein that provides strength and waterproofing to the skin.

In the stratum granulosum, keratinocytes begin to lose their nuclei and organelles, ultimately leading to their death. This process is essential in forming the protective outer layer of the skin. The granules seen in this layer contain keratohyalin, which helps in consolidating keratin filaments together and also plays a role in maintaining hydration in the skin. Thus, understanding the function of the stratum granulosum in keratin production is vital for appreciating how the skin maintains its barrier properties and protects the underlying structures from environmental damage.