Which layer of the skin contains no blood vessels or nerves?

The epidermis is the outermost layer of the skin and is primarily composed of keratinocytes, which are cells that produce keratin, a protective protein. One key characteristic of the epidermis is that it is avascular, meaning it contains no blood vessels. This absence of blood vessels is important as it helps to form a protective barrier and limits the direct exposure of underlying tissues to blood supply, thereby minimizing the risk of infections or injuries directly affecting deeper tissues.

Additionally, the lack of nerves within the epidermis is significant for its role in sensation. While the epidermis does not have its own nerve endings, it relies on the underlying dermis, which contains blood vessels, nerves, and various sensory receptors, to provide sensory feedback.

In contrast, the dermis is rich in blood vessels and nerves, providing nourishment and sensation to the skin, while the hypodermis, or subcutaneous layer, connects the skin to underlying tissues and also has a network of blood vessels and nerves. Therefore, the absence of both blood vessels and nerves distinctly identifies the epidermis as the correct answer in this context.