Types of movement

Types of movement

Not every kind of biological movement uses the same machinery. Four distinct types occur in and around the cells of the human body:

• Amoeboid movement — cells that crawl by extending temporary cytoplasmic projections called pseudopodia, produced by the streaming flow of cytoplasm inside the cell. Phagocytic white blood cells such as macrophages use this mode of movement to chase down and engulf invading pathogens; it is essentially the same mechanism Amoeba uses to crawl, adapted for immune defence.
• Ciliary movement — produced by the coordinated beating of many short, hair-like cilia projecting from a ciliated epithelial cell. This lines passages such as the respiratory tract, where ciliary beating sweeps mucus and trapped particles upward and out, and the genital tract, where it helps move the egg along the fallopian tube.
• Flagellar movement — produced by a single long, whip-like flagellum. The clearest human example is the sperm cell, whose flagellum beats to propel it toward the egg.
• Muscular movement — the movement most people mean by "movement": the contraction and relaxation of skeletal muscle moving the hands, legs, jaws and tongue, which is the main subject of the rest of this chapter. …