What term describes hair with a central canal that helps in nutrient absorption?

The correct term that describes hair with a central canal responsible for nutrient absorption is the medulla. The medulla is the innermost layer of the hair shaft and can be found in some types of hair. It contains soft keratin and air spaces, which can contribute to the absorption of nutrients as well as the overall texture and flexibility of the hair. Understanding the structure of the hair is important for hair care and treatments, as different layers play distinct roles.

The other options refer to different aspects of hair anatomy. The cortex is the thick middle layer that provides strength, color, and texture, while the follicle is the structure from which hair grows, and the bulb is the enlarged portion at the base of the hair follicle that contains living cells and is critical for hair growth. Each of these components has its own function, but the medulla specifically denotes the central canal and its role in nutrient absorption.