heat definition In physics, a form of energy associated with the movement of atoms and molecules in any material. The higher the temperature of a material, the faster the atoms are moving, and hence the greater the amount of energy present as heat.
Cilia (singular: cilium) are microscopic, hair-like structures that extend outwardfrom the surface of manyanimal cells. These structures are important in the cell cycle and replication, and cilia play a vital part in human and animal development and in everyday life. A typical cilium is between one and ten micrometers long, and usually less than one micrometer wide.
The length of a single cilium is 1-10 micrometres and width is less than 1 micrometre. Cilia are broadly divided into two types. They function separately and sometimes together: Source: Amelia Shoemark. ' Motile ' (or moving) cilia are found in the lungs, respiratory tract and middle ear.These cilia have a rhythmic waving or beating motion (see right). They work, for instance, to keep the airways clear of mucus and dirt, allowing us to breathe easily and without irritation. They also help propel sperm.hey are now recognised as playing crucial roles in a number of organs. Some act as a sensory antenna for the cell, receiving signals from other cells or fluids nearby. 1  In the kidney, for example, cilia bend with urine flow and send a signal to alert the cells that there is a flow of urine.