Why can't the body cells live without performing specialized tasks and being organized according to specialization into systems that accomplish functions essential for the whole body's ________?
Every cell of your body needs to obtain _________ and oxygen and to eliminate wastes, yet every cell of your body cannot directly make these exchanges with the environment surrounding the body, because the cell is isolated from this external environment.
How is it possible for a chondrocyte (or other specialized cell) to make vital _________ with the external environment with which it has no direct contact?
The key is the presence of an aqueous internal environment with which the body cells are in direct contact. This internal environment consists of extracellular fluid. Most of this _____________ fluid consists of the plasma, the fluid portion of the blood, and the ____________ fluid, which surrounds and bathes all the cells.
Various body systems make exchanges between the external environment and the ________ environment. For example, the digestive system transfers nutrients from the external environment within the small intestine to the internal environment of the blood. Similarly, the ___________ system transfers oxygen from the external environment in the alveoli of the lungs to the internal enviornment of the plasma.
As a result, the nutrients and oxygen from the external environment are transferred into the internal environment of the plasma which in turn transfers them to the internal environment of the interstitial fluid. Finally, the cells which are in contact with the interstitial fluid are able to transfer the nutrients and oxygen from the interstitial fluid into the _____________ fluid of the cell.
Similarly, wastes produced by the cells are extruded into the interstitial fluid, picked up by the plasma, and transported to the organs that specialize in eliminating these wastses from the internal environment to the external environment. For example, the lungs remove carbon dioxide from the plasma, and the kidneys remove other wastes for elimination in the _____.
Thus, every cell of your body takes in essential nutirents and oxygen from and eliminates wastes into its watery surrounds, just as an ameoba does. The major difference is that each cell of the body must help maintain the composition of the internal enviornment so that this fluid continuously remains suitable to support the survival of all the body cells. In contrast an ameoba does nothing to ________ its surroundings.
