2. Water’s Role In The Body
2.1 How Body Water Is Obtained
The average adult is composed of almost 60% fluid. That’s more water than the total of all other substances in the body! Our body’s water is obtained from the fluids we drink and from the water content of the foods we eat. It is also obtained from the body’s internal oxidation reactions. The oxidation process occurs in the combining of hydrogen in the food we eat with the oxygen we breathe. Some animals are dependent on the oxidative water they produce for their very existence.
2.2 Minerals In the Body Fluids
The water within our body contains many materials in solution; that is, it contains many substances dissolved in it. The complement of minerals dissolved in the body fluid are referred to as salts. These salts include sodium, calcium, magnesium, potassium, chlorine, phosphorus and other elements. They possess electric charges and are thereby referred to as electrolytes.
Some salts possess positive electrical charges and others possess negative charges. These charges, inherent in the salts, are part of the regulatory process in the movement of fluids within the body. The positively and negatively charged particles exist1 in equally balanced amounts in the body. The resultant charge between the particles is therefore neutral.
It is true that the balance of salts is crucial to the proper functioning of the human organism. It is, however, not necessary that we udd substances such as table salt, baking soda, mineral supplements or mineralized waters to our diet in order to assure ourselves of the proper complement of salts. Our bodies, as you will remember from Lesson 10 on minerals, can assimilate and utilize only organic minerals as are found in foods. Adding table salt to the diet is literally adding a poison I We’ll discuss this in more detail later in the lesson.
2.3 Cellular Fluids
About three-fourths of the body’s fluid is stored within the cells and is known as cellular fluid. The extracellular fluid is composed of plasma and interstitial fluid.
Blood plasma, a clear, yellow-colored fluid, is approximately 92% water. The plasma carries within it a huge volume of substances. It transports mineral salts and carries carbohydrates, proteins, gases, enzymes, fats and hormones. There are certain plasma proteins that are always present in the plasma. Other materials are in a constant state of change. The amounts of food materials (such as glucose), carbon dioxide and nitrogen wastes are constantly changing in the plasma.
Interstitial fluid is similar to plasma except it does not contain the plasma’s complement of proteins. However, interstitial fluid does contain glucose, minerals and urea and it continually bathes the cells. Through this bathing, the cell is supplied with all its needs for existence.
In addition to the circulatory system formed by the blood, yet another system exists and flows through the lymph vessels. The lymph circulation, along with the blood, is responsible for the flow and mixing of the extracellular fluid. One of the major functions of the lymph vessels is the return of the proteins to the circulation after they leave the bloodstream. The lymph provides the only routing whereby these “plasma proteins” can be restored to the circulation. Another part of the lymphatic system consists of small filtering organs called lymph nodes, which filter the lymph fluid as it passes through.
2.4 The Inner Sea and Its Movements
The fluids in our body are true life-keepers and can be likened unto an ocean in which literally trillions of cells, themselves largely water, are immersed. Within this “ocean” the materials we need for our survival are carried. In addition, the same system is responsible for carrying away our wastes, such as nitrogen, unusable minerals and other toxic substances.
The nutrients our body needs are broken down from foodstuffs in the digestive system. After they are broken down they are water-soluble. This means they can be
mixed with water and dissolved in it. When the nutrients are, put into solution, the pass through the capillaries (small tubes) within the intestinal wall. The blood flowing in these walls picks up the tiny particles of nutrients. Through the circulatory system, the nutrients are finally distributed by the extracellular fluid bathing the cells.
When the nutrients are finally distributed by the circulatory system to the cells, how do they make themselves available for use by the cells themselves?
It is the responsibility of the circulatory system to distribute the nutrients and bathe the cells with them. The process by which needed materials are absorbed (and also by which wastes leave the cell) are known by the names diffusion, osmosis and active transport.
Diffusion is merely the arbitrary movement of particles through the cell walls. The movement of the particles is limited by the size of the pores of the cell wall (cellular membrane). The cellular membrane is a semipermeable membrane—it allows only certain substances in particular forms to pass through it. This factor is very crucial to the cell’s existence. If the cellular membrane did not have the capacity to keep some substances outside of the cell and others permanently inside, the cell would be no different in composition from the fluid surrounding it, and it would not be able to maintain its distinct life.
Osmosis refers to the particular process in which the balance of salts takes place. Water tends to go where the greater concentration of salt lies; in other words, water will pass through the semipermeable membrane from a lesser concentrated salt solution to a greater concentrated solution. The result is that the proportion of positive and negative electrolytes is balanced. An easy way to remember the term osmosis is that it’s a fancy way of saying that in cellular metabolism, water goes where the salt is.
At this point, mention should be made that this action of water is not an intelligent one done by the water. Water is utilized by the body; it is itself an inert substance and does not act upon the body.
In addition to osmosis and diffusion, a process called active transport occurs, in which electrolytes move across the cellular membrane from an area of lesser salt concentration to an area of great salt concentration.
Fluids constantly flow through the cellular membranes in both directions—both into and out of the cell—through these processes of diffusion, osmosis and active transport. However, the total amount of cellular fluid and the total amount of extracellular fluid remain at a constant balance during this interchange. There is a real need for this precisely balanced flow of fluids between the cellular fluid and the extracellular fluid, so that the cells within the body do not continually shrink and expand.
An example illustrates the importance of this balance of fluids. If the cells were immersed in distilled water, they would grow to the point of bursting because distilled water is so much less dense than the fluid in the cells! Conversely, if the cells were surrounded by e strong salt solution, the cells would lose their water and shrivel up. These examples are an impossibility in the functioning of our organism, but they do point to the need for the proper balancing of both the amounts and types of fluids to which our cells are exposed.
Now let’s see what happens when the processes of diffusion, osmosis and active transport occur within the body. Glucose, or blood sugar, is a primary nutritive factor derived from foods. It is the immediate fuel of the cells of the body and is distributed by the extracellular fluids. The liver is responsible, among other things, for regulating the amount of blood sugar that reaches the cells. It also forms proteins from amino acids, which are then dissolved in the plasma. These plasma proteins float in the watery part of the blood and are easily absorbed by the individual cells, which break it down again into its component amino acids.
Minerals can be directly absorbed from the small intestine and put into the bloodstream without undergoing chemical change.
2.3 Waste Removal
Thus far we have been discussing water’s role in delivering nutrients to the body’s cells. Water plays an equally significant role in removing the wastes of the body.
One of the more persistently produced wastes by humans and animals alike is carbon dioxide. The body has uses for a small amount of carbon dioxide, but would expire could it not expel its excesses! In the process of carbon dioxide expulsion, the cells firstly allow their excess carbon dioxide to diffuse into the extracellular fluid. Later the lungs exhale the unneeded carbon dioxide. Blood is able to carry carbon dioxide because carbon dioxide is easily dissolved in the blood’s water.
Another waste that the body continually produces is nitrogen. Nitrogen is basically a by-product of protein metabolism. The elimination of nitrogen is not as simple as that of carbon dioxide; it cannot merely be discharged as nitrogen gas. Our organism has not developed the capacity to discharge nitrogen. If nitrogen were combined with hydrogen in the bloodstream, it would form the extremely toxic substance ammonia. The ammonia would then itself poison the body. Therefore, nitrogen must be expelled in a form that is not itself toxic to the human body. Ammonia combines with carbon dioxide, itself a waste product of humans, to form urea. Urea itself is a solid, but it is easily dissolved in the water within the bloodstream.
Urea would quickly reach a toxic level within the body were it not for the functioning of the kidneys. It is the job of the kidneys to filter the blood. They also return to the bloodstream the substances in blood that the body needs. The waste products, including urea, are not reabsorbed but are mixed with water to form urine, which is afterwards expelled through the bladder.
As stated earlier, nitrogen is a by-product of protein metabolism. It costs the body energy to expel this substance in the form of urea. A person following the Life Science regime and eating a diet of raw fruits, vegetables, nuts and seeds will not have as many proteinacious wastes as someone eating a conventional diet of processed foods, meats and dairy products and thereby will expend less energy in expelling these wastes. The urine of a person who is eating a conventional diet high in protein is apt to be darker and thicker than the urine of a person who eats Hygienically.
2.4 Water Cools the Body
One of the major reasons the water balance in the body is so crucial to our health is water’s direct relationship to the temperature regulation of the body. Some. animals, such as the camel, actually undergo large differences in body temperature dependent on the air. temperature around them. Yet an internal temperature change of even a very few degrees can mean death to a human being.
A “normal” human adult gains about two and one-half quarts of water daily. To maintain bodily balance, one also loses approximately the same amount. This water is gained from food and liquid sources, and also, from oxidative sources. Oxidative water is merely water that is formed by the chemical reaction of hydrogen combining with oxygen within the body.
The body loses water through the kidneys and bowels. It also loses water through the lungs, and through the skin as perspiration. Perspiration cools the skin when it evaporates, which helps to maintain body temperature, but it can be dangerous or even fatal if the body loses too much water. On an extremely hot day we may lose as much as a quart of water per hour through perspiration. Losing eight quarts by this method would mean death.
When water is lost by the blood, the blood becomes denser. When this happens, water is drawn into the capillaries from the intercellular fluid so that the blood can maintain its flow and carry away unneeded heat in the body.
The skin stops the evaporation of the water in the body. It is the structure from which 85% of the body’s heat is lost. Sweat is a clear fluid, mostly water, and it may contain toxins. Sweat is excreted through the pores of the skin. Heat is lost by radiation and the evaporation of sweat from the skin. Typically we may lose a pint of water daily due to sweat.