Cell (Encyclopedia of Science)
The cell is the basic unit of a living organism. In multicellular organisms (organisms with more than one cell), a collection of cells that work together to perform similar functions is called a tissue. In the next higher level of organization, various tissues that perform coordinated functions form organs. Finally, organs that work together to perform general processes form body systems.
Types of cells
Multicellular organisms contain a vast array of highly specialized cells. Plants contain root cells, leaf cells, and stem cells. Humans have skin cells, nerve cells, and sex cells. Each kind of cell is structured to perform a highly specialized function. Often, examining a cell's structure reveals much about its function in the organism. For instance, certain cells in the small intestine have developed microvilli (hairs) that promote the absorption of foods. Nerve cells, or neurons, are another kind of specialized cell whose form reflects function. Nerve cells consist of a cell body and long attachments, called axons, that conduct nerve impulses. Dendrites are shorter attachments that receive nerve impulses.
Sensory cells are cells that detect information from the outside environment and transmit that information to the brain. Sensory cells often have unusual shapes and structures that contribute to their function. The rod cells in the retina of...
(The entire section is 2580 words.)
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