Final answer:
Thinning skin is caused by the aging process and changes in the integumentary system. Various factors such as decreased activity of accessory structures, reduced production of collagen and elastin, weakened muscles, and inadequate moisture retention contribute to thinning skin in older individuals.
Step-by-step explanation:
Thinning skin occurs as a result of aging and changes in the integumentary system. With age, the activity of accessory structures in the skin, such as hair follicles and sweat glands, decreases, leading to thinner hair, nails, and reduced amounts of sebum and sweat. The reduced activity of melanocytes and dendritic cells in the skin also contributes to a paler skin tone and lowered immunity. Additionally, there is a breakdown of the skin's structure due to decreased production of collagen and elastin, weakening of the underlying muscles, and the skin's inability to retain adequate moisture. All these factors contribute to thinning skin in older individuals.