Final answer:
The hair bulb is the part of the hair strand that contains the blood and nervous supply. It surrounds the hair papilla which is connected to the blood supply and nerve endings.
Step-by-step explanation:
The part of the hair that contains blood and nervous supply is the hair bulb. Hair growth begins in the hair bulb with the production of cells. The hair bulb is also identified as the structure surrounding the hair papilla. The hair papilla is a mass of connective tissue that includes blood capillaries and nerve endings from the dermis. So, the correct answer is 4) Bulb. The bulb of the hair strand is deeply embedded into the skin and is connected to the blood supply via the blood capillaries present in it.
Learn more about Hair Bulb