WHAT ARE CILIA AND FLAGELLA?
Eukaryotic flagella are whiplike structures that propel cells such as sperm through fluid
Cilia and flagella are whip-like appendages of many living cells that are used to move fluid or to propel the cells. Cilia beat with an oar-like motion and flagella have a snake-like motion as illustrated in Figure 1. The cilia in your lungs keep dirt and dust from clogging your breathing tubes (the bronchi) by moving a layer of sticky mucous along to clean out the airways. Sperm cells use a flagellum as a propeller to move the cell through the fluid of the oviduct to reach the egg. Thousands of animals and plants use cilia and flagella for swimming (example: paramecium), or feeding (example: clams and mussels) or mating (example: green algae). It is a curious fact that all of these cilia and flagella have a very similar internal arrangement of tubes (the outer doublets) and protein connectors (the nexin links and dynein arms) that suggest that there is something very special about this particular way of building a cell propeller. Figure 2 is a diagram of these internal parts of a cili
