Which of the following layers of skin is a sturdy collagenous layer?

The dermis is the correct answer because it is the layer of skin that contains a significant amount of collagen, which provides strength and elasticity to the skin. The dermis lies beneath the epidermis and is primarily composed of dense connective tissue, which includes collagen fibers. This layer plays a crucial role in supporting the epidermis and housing various structures such as blood vessels, hair follicles, and sweat glands.

The epidermis, while essential for protecting the body, is primarily made up of epithelial cells and does not have the same collagen-rich structure as the dermis. The hypodermis, also known as the subcutaneous layer, is primarily composed of fat and connective tissue, serving as an insulator and shock absorber rather than providing the sturdy, collagenous support the dermis offers. Keratin, on the other hand, is a protein found within the skin, particularly in the epidermis, and is responsible for waterproofing and protecting skin cells but is not a layer of skin itself. Therefore, the dermis is distinct for its robust collagenous structure, making it essential for the skin's strength and resilience.