Final answer:
The epidermis is the outer epithelial layer of the skin that forms a protective barrier, while the dermis is the inner connective tissue layer containing important skin structures. Beneath these layers lies the hypodermis, which is composed of connective and fatty tissue but is not considered a part of the skin itself.
Step-by-step explanation:
The epidermis and the dermis are the two primary layers that compose the human skin. The epidermis is the outer layer, made of closely packed epithelial cells, which forms a protective barrier. This barrier is primarily made up of keratinocytes, the cells that produce keratin, a tough fibrous protein. As new keratinocytes form at the basal layer of the epidermis, they slowly move up towards the surface, becoming filled with keratin and eventually dying to create a waterproof, protective outer layer.
The dermis lies beneath the epidermis and consists of dense, irregular connective tissue that provides strength and elasticity to the skin. It contains critical structures such as blood vessels, sensory receptors, hair follicles, oil and sweat glands. The dermis is responsible for most of the functional activity of the skin, including sensation, temperature regulation, and structural integrity.
Just below the dermis is the hypodermis, which is made of loose connective and fatty tissues and plays a role in insulating the body as well as providing energy storage. While it is not considered a part of the skin, it closely associates with the dermal layer.