How can osteocytes remain alive within bone? Select one: Osteocytes have membrane extensions that protrude from bone and allow them to exchange materials with the surrounding fluids. Haversian canals are bone structures that contain blood vessels that provide materials for the osteocytes. Bones are composed of only dead or dormant cells. Bones are hollow in the middle and the low pressure there draws fluid from the blood that nourishes the osteocytes.