Within multicellular organisms, tissues are organized communities of cells that work together to carry out a specific function. The exact role of a tissue in an organism depends on what types of cells it contains. For example, the endothelial tissue that lines the human gastrointestinal tract consists of several cell types. Some of these cells absorb nutrients from the digestive contents, whereas others (called goblet cells) secrete a lubricating mucus that helps the contents travel smoothly.
However, the multiple cell types within a tissue don't just have different functions. They also have different transcriptional programs and may well divide at different rates. Proper regulation of these rates is essential to tissue maintenance and repair. The spatial organization of the cells that form a tissue is also central to the tissue's function and survival. This organization depends in part on polarity, or the orientation of particular cells in their place. Of course, external signals from neighboring cells or from the extracellular matrix are also important influences on the arrangement of cells in a tissue.
The range in size of most atomic radii is approximately <span>5 × 10−21 m to 2 × 10−20 m. The rest of the choices do not answer the question above.</span>
