Final Answer:
The hair shaft is the visible part of the hair extending beyond the skin's surface. The hair root, on the other hand, is below the skin and includes the hair bulb, hair papilla, and matrix. The sebaceous gland produces sebum, a natural oil that moisturizes the hair and skin. The arrector pili muscle is responsible for hair erection.
Step-by-step explanation:
The hair follicle consists of two main parts: the exposed hair shaft and the non-exposed hair root. The shaft is the part of the hair visible on the skin's surface, while the root lies beneath the skin. The hair root comprises several essential structures, including the hair bulb, hair papilla, and matrix. The bulb is the rounded base of the hair follicle, containing the actively dividing cells responsible for hair growth. The hair papilla is a connective tissue structure that provides nourishment to the growing hair. The matrix, located around the papilla, is a region of actively dividing cells that contribute to hair shaft formation.
Additionally, sebaceous glands are associated with hair follicles and produce sebum, an oily substance that helps moisturize the hair and skin. This process is crucial for maintaining healthy hair and preventing dryness. Furthermore, the arrector pili muscle is a small muscle connected to hair follicles. When stimulated, it contracts, causing the hair to stand upright—a phenomenon commonly known as "goosebumps." This muscle's contraction is often linked to emotional responses or temperature changes, providing a physiological response to external stimuli.
In summary, the hair shaft and root, along with the sebaceous gland and arrector pili muscle, collectively contribute to the structure, growth, and maintenance of hair. Understanding these components is essential for comprehending the complex biology of hair and the factors influencing its appearance and health.