| A | B |
|---|
| cell | the basic unit of structure and function in living things |
| cell membrane | outside boundary of a cell; controls which substances can enter and leave a cell |
| nucleus | control center of a cell that directs its activity |
| cytoplasm | region of a cell between the cell membrane and nucleus; contains a gel-like material and cell organelles |
| tissue | a group of similar cells that perform a specific function in an organism |
| muscle tissue | a body tissue that contracts or shortens, make body parts move |
| nerve tissue | a body tissue that carries messages back and forth between the brain and every other part of the body |
| connective tissue | a body tissue that provides support for the body and connects all of its parts |
| epithelial tissue | a body tissue that covers the surfaces of the body, inside and out |
| organ | a structure in the body that is composed of different kinds of tissue |
| organ system | a group of organs that work together to perform a major function in the body |
| homeostasis | the process by which an organism's internal environment is kept stable in spite of changes in the environment |
| stress | the reaction of a person's body and mind to threatening, challenging, or disturbing events |
| vertebrae | the bones that make up the backbone of an animal |
| marrow | the soft tissue that fills the internal spaces in bone |
| vertebra | one bone that makes up the many bones of the backbone |
