Nutrition: Hydration Chapter 4
Water At Work
Water & The Urinary System
Urine forms in the kidneys, with water being the most important substance in the delivery, filtration, and excretion of liquid waste. Much like a gulp of water sluices chewed food down the esophagus and into the digestive tract, the water in blood helps to carry all variety of molecules through the bloodstream. Those substances that are unwanted (e.g., toxins), unneeded (leftover electrolytes), or in excess (extra protein and vitamins) are filtered out as the watery blood passes through the kidneys, straining out impurities and excess water. READ MORE
From the kidney, water helps carry the impurities out through the ureter and into the bladder. As liquid waste fills and distends the elastic sac of the bladder, the pressure resulting from increased water volume trips a signal to the brain: it’s time to release waste. With the relaxing of the urinary sphincter (a ring of muscle at the base of the bladder), pressure on the bladder is relieved as urine is expelled through the urethra.
While water consumption is easily relatable to urine output, staying hydrated has a healthful effect on excreting solid waste as well, since water helps break down food and wash it through the gastrointestinal tract. Dehydration, by contrast, slows GI function and hardens the stool. Drinking plenty of water is the first preventive measure to avoid constipation. LESS
Prevention And ProtectionREAD MORE
Additionally, mucous membranes of the respiratory system are more effective at trapping the pathogens that cause disease when moistened by hydration. In another protective measure, the pressurized water within joints, tendons, muscle, and fat helps areas of the body function like gel-filled football pads, providing cushion against shock. LESS
Regulating TemperatureREAD MORE
When you see someone’s skin become red from heat or exertion, it is due to a rush of blood. What’s happening is that blood shunts closer to the surface of the skin so that it can be cooled. With the help of perspiration, the skin surface cools down and exchanges heat from the blood. The cooled blood then circulates toward the core, keeping the entire body at a reasonable temperature. Going back to our engine comparison, antifreeze regularly passes through the fins of a radiator, which provide greater surface area through which heat can escape; our body is cooled in a similar manner, with our entire outer layer of skin providing surface area for heat release. LESS
Water is a key ingredient in nutrient metabolism, which is the process of converting food into energy. Unlike any other physical or chemical component of metabolism, water is involved throughout the metabolic process, and it all begins with the breakdown of foods in the mouth. There, water is an ingredient within saliva, which soaks and softens foods so that they can more easily be chewed and swallowed. Sugars, salts, and nutrients such as B-complex vitamins and Vitamin C are water-soluble, meaning that they dissolve in water. All nutrients have to dissolve, but some are broken down in lipids (fats) rather than in water. READ MORE
Water transportation is a familiar concept, but of course there is no surface on which to travel in our closed circulatory system. Rather than riding buoyantly like boats on the sea, molecules of nutrients move in the bloodstream more like small fish at the mercy of the tide.
Once food is broken down into molecules in the upper digestive tract, the nutrients pass through the permeable walls of the small intestine and into the bloodstream together with ingested water. In the fast-moving bloodstream, which gains fluency thanks to its watery constitution, nutrients are carried to the body’s cells or to the kidneys as waste. LESS
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