Cilia and Ciliary Movements
A second type of cellular motion, ciliary movement, is a
whiplike movement of cilia on the surfaces of cells. This occurs in only two places in the human body:
on the surfaces of the respiratory airways and on the inside surfaces of the uterine tubes (fallopian
tubes) of the reproductive tract. In the nasal cavity and lower respiratory airways, the whiplike motion
of cilia causes a layer of mucus to move at a rate of about 1 cm/min toward the pharynx, in this way
continually clearing these passageways of mucus and particles that have become trapped in the mucus.
In the uterine tubes, the cilia cause slow movement of fluid from the ostium of the uterine tube toward
the uterus cavity; this movement of fluid transports the ovum from the ovary to the uterus. As shown
in Figure 2-17, a cilium has the appearance of a sharp-pointed straight or curved hair that projects 2 to
4 micrometers from the surface of the cell. Many cilia often project from a single cell—for instance, as
many as 200 cilia on the surface of each epithelial cell inside the respiratory passageways.
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