Scanning electron micrograph of a macrophage migrating from the alveoli surface of the lung (left) to the ciliated surface of a bronchiole (right). The direction of movement is indicated by its shape, which is broad and ruffled at the leading edge and tapers at the trailing edge. Macrophages are large scavenger cells, or phagocytes, found in connective tissue and many of the major organs. They are involved in a process called phagocytosis whereby the cytoplasm of the cell engulfs & digests foreign materials. In this case the macrophage has engulfed an asbestos fibre seen as a needlelike extension at the top of the cell.