Q.Macrophages and leucocytes exhibit

Before we ever think about arms and legs, movement is already happening deep inside the body at the level of single cells. Movement is one of the defining signs of life, and the cells of the human body carry it out in three broad ways: amoeboid movement, ciliary movement and muscular movement. Each serves the body differently, and only muscular movement uses muscles at all.

Amoeboid movement is how certain cells travel without any muscles — they crawl. Named after the way an amoeba creeps along, it is seen in our own body in cells like the macrophages and the leucocytes (white blood cells) of the blood. It works like this:

• The cell pushes out temporary extensions of itself called pseudopodia, literally 'false feet', which form when the protoplasm inside the cell streams and flows in a particular direction and drags the cell forward.
• Cytoskeletal elements, especially the fine threads called microfilaments, help produce this movement.

Ciliary movement uses tiny hair-like structures called cilia that cover the lining of many internal tubular organs. Their rhythmic, coordinated beating sweeps material along the surface. It matters in two familiar places:

• In the trachea (windpipe), the coordinated beating helps drive out dust and other foreign particles breathed in with the air, keeping the airway clean.
• In the female reproductive tract, it helps move the ovum (egg) along the passage.

Muscular movement is the one that depends on muscle, using the special ability of muscles to contract. Movements of body parts such as the limbs, jaws and tongue rely on this contractile property. …