Final answer:
The hair shaft is the visible, dead part of hair above the skin, while the living part, the hair root, contains the hair matrix which is essential for hair growth.
Step-by-step explanation:
Hair is a keratinous filament that grows from the hair follicle in the skin. The human body is adorned with hair follicles that produce hair, which serves multiple functions such as insulation, protection, and sensory input. The hair matrix is a crucial part of this structure, found deep within the hair follicle.
The hair shaft is the part of hair that is visible above the skin surface—the portion that is not anchored to the follicle and is considered dead as it has no biochemical activity. Contrarily, the part within the follicle—the hair root—is the only living portion of the hair. The hair root culminates in the hair bulb, which includes the hair matrix, a layer of actively dividing basal cells that contribute to hair growth.
The hair matrix surrounds the hair papilla, which is rich in connective tissue and nourished by blood capillaries and nerve endings from the dermis. This comprehensive structure is pivotal for the continuous growth and regeneration of hair.