Final answer:
An accessory structure, as opposed to a component of the cutaneous membrane, includes hair, nails, sweat glands, and sebaceous glands. These structures support the integumentary system by helping with protection, temperature regulation, and providing strength to the skin.
Step-by-step explanation:
Accessory Structures of the Integumentary System:
The structure that is considered an accessory structure, rather than part of the cutaneous membrane (the skin), includes structures such as hair, nails, sweat glands, and sebaceous glands. These structures are not part of the skin itself but are integral to the integumentary system, aiding in protection and the maintenance of body functions. They embryologically originate from the epidermis but can extend deep through the dermis into the hypodermis. Hair, for instance, is composed of dead keratinized cells, and nails serve to protect the extremities of our fingers and toes, also being made of keratinized cells. Sweat and sebaceous glands are involved in regulating body temperature and moisturizing the skin, respectively.
The cutaneous membrane consists of multiple layers including the epidermis and dermis, with the hypodermis underneath. Whereas the accessory structures like hair and nails emerge from and sometimes penetrate through these layers, they are considered as supplementary components that serve specialized functions.