What are the three basic structures of vertebrate skin?

The three basic structures of vertebrate skin are the epidermis, dermis, and glands.

The epidermis is the outermost layer of skin, providing the primary barrier against the external environment and protecting underlying tissues. It consists of multiple layers of cells, primarily keratinocytes, which contribute to skin's protective function.

The dermis lies beneath the epidermis and contains connective tissue, blood vessels, nerves, hair follicles, and various glands. It plays a crucial role in providing strength and elasticity to the skin as well as housing structures that assist in thermoregulation and sensory perception.

Glands, which are also considered part of the skin structure, include the sebaceous glands that secrete oil and sweat glands responsible for temperature regulation and excretion.

In contrast, the other answer choices include components that either misrepresent the skin's structural layers or introduce non-skin elements without accurate context. For example, while the hypodermis and adipose tissue are important for insulation and energy storage, they are not layers of the skin itself. Thus, the choice encompassing the epidermis, dermis, and glands accurately captures the essential components that make up the integumentary system of vertebrates.