Describe the accessory structure (nails, hair) of the skin and its functions

The skin, also known as the integumentary system, has several accessory structures including nails and hair. These structures play a crucial role in protecting the body, maintaining body temperature, and sensing the external environment.

1. Nails: Nails are hard, keratinized structures that cover the dorsal surface of the terminal bones of fingers and toes. They are derived from the stratum corneum layer of the skin. The primary function of nails is to protect the fingertips and toes from injuries. They also enhance the sensitivity of the fingertips by acting as a counterforce to the tactile pad when it touches an object. Additionally, nails can be used as tools for scratching or peeling.

2. Hair: Hair is another accessory structure of the skin that is found all over the body except on the palms of the hands, soles of the feet, and certain parts of the genitalia. Hair is composed of dead, keratinized cells and is produced in hair follicles. The main function of hair is to protect the skin from UV radiation and the entry of foreign particles. On the scalp, it provides insulation from cold for the head. The hair in the nostrils, ears, and eyes prevents dust and other small particles from entering the body. Hair also plays a role in sensory perception; the bending of hair stimulates nerve endings allowing the person to feel a light touch.

In conclusion, the accessory structures of the skin, such as nails and hair, play a crucial role in protecting the body, maintaining body temperature, and providing sensory perception.