What do adnexal structures in the skin include?

Adnexal structures in the skin refer specifically to the accessory structures that are closely related to the skin's function and protection. The correct answer highlights components that are integral to the skin's physiology and maintenance.

Hair plays a crucial role in thermoregulation and sensory perception, while sebaceous glands, often associated with hair follicles, secrete oil (sebum) that helps to moisturize skin and hair, maintaining their health and protecting against microbial infection. Eccrine glands, a type of sweat gland, are important for temperature regulation through perspiration, facilitating evaporative cooling. Together, hair, sebaceous glands, and eccrine glands represent a comprehensive view of the structures involved in the skin's protective and regulatory functions.

Other options include elements that do not accurately represent the adnexal structures or contain items that are not classified as such. For example, nails are indeed related to the skin but do not include the functional components that are also present in B. This highlights the specificity and relevance of the correct choice concerning skin anatomy and physiology.