What structural feature distinguishes thick skin from thin skin?

Thick skin is characterized by the presence of a prominent stratum lucidum layer, which is an additional layer of cells found between the stratum corneum and the stratum granulosum in areas of the body that experience significant friction and abrasion, such as the palms of the hands and the soles of the feet. This layer is typically absent in thin skin, which covers most of the body. The stratum lucidum provides an extra barrier of protection due to its dense, clear layer of keratinocytes that helps to reduce water loss and increase skin resilience.

The other options do not serve as distinguishing features of thick skin. Thick skin contains no hair follicles, which are present in thin skin. While thick skin does indeed have a thicker epidermis overall, it is specifically the presence of the stratum lucidum that is the key distinguishing feature. Lastly, while nerve endings may be more densely packed in some regions of thick skin, this does not specifically define the structural difference between thick and thin skin like the stratum lucidum does.