Final answer:
Hair is mostly made of keratinized cells, which are densely packed cells filled with keratin. The hair matrix, located at the base of the hair root, contains basal cells that contribute to hair growth.
Step-by-step explanation:
Hair is primarily constructed of keratinized cells. These cells are densely packed and filled with keratin, a fibrous protein that gives hair its hardness and water-resistant properties. The keratinized cells in the hair follicle grow out of the epidermis and form the hair shaft, which is the visible part of the hair. The hair matrix, located at the base of the hair root, contains a layer of basal cells that are responsible for its growth.