All of the following structures are considered to be accessory structures of the skin EXCEPT:

• A. Hair follicles
• B. Nails
• C. Sweat glands
• D. Epidermis

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the term 'accessory structures of the skin.' These are structures that are not part of the main layers of the skin but are associated with its function, such as hair follicles, nails, and sweat glands.
2. Step 2: Recall the main layers of the skin: the epidermis (outermost layer), dermis (middle layer), and hypodermis (subcutaneous layer). The epidermis is a primary layer of the skin, not an accessory structure.
3. Step 3: Review the functions of accessory structures. Hair follicles produce hair, nails protect the tips of fingers and toes, and sweat glands help regulate body temperature and excrete waste. These are all considered accessory structures because they support the skin's functions.
4. Step 4: Compare the epidermis to accessory structures. The epidermis is a fundamental layer of the skin itself, responsible for protection and serving as a barrier, whereas accessory structures are additional components that aid the skin's functions.
5. Step 5: Conclude that the epidermis is not an accessory structure of the skin because it is a primary layer of the skin, unlike hair follicles, nails, and sweat glands, which are accessory structures.