Term Paper: Kidneys and How They Function

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¶ … Kidneys and How They Function

One of the most important functions of the kidneys - though not the only key function - is to provide an effective filtering device for the blood in the human body, through which about 200 quarts of blood flow on a daily basis, according to the National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC). Within those 200 quarts of blood the kidneys screen out about 2 quarts of waste products. A big portion of that waste becomes urine and is stored in the bladder, thanks to the smooth functioning of the kidneys.

Where did those wastes in the blood come from? This is the explanation of what the kidneys' principle role truly is. There is a normal breakdown of active tissues in all that humans eat, and the body knows what portions of that food it needs to sustain its functions and repair its ills, and what it doesn't need it sends to the blood. Then, the blood circulates through the kidneys and the result is as mentioned above. Without the work of the kidneys, wastes would gather and collect in the body and cause harm. In a very real way, the kidneys are analogous to the average municipal wastewater treatment plant; raw waste goes into the plant from human repositories in homes and elsewhere. Those materials are filtered and processed and are expelled as "gray water" or something akin to gray water.

The gray water or treated water is then transported to the ocean, or to holding facilities for further community use. Likewise, the kidneys' separate out the waste and it is transported to the bladder for permanent removal.

The specific structure of the kidneys can be explained within a discussion of nephrons. Indeed, the pivotal physiological and cellular mechanisms / components within the kidneys are called nephrons. There are about a million nephrons in the kidneys. Inside each nephron, according to NKUDIC, is a glomerulus - a miniature blood vessel, or capillary - "intertwines" with a small "urine-collecting tube" that is called a tubule. This is the esoteric exchange system / mechanism that actually, through a chemical process, sends the waste materials and some water over to the bladder. The kidneys' job here is to decide what amount of certain chemicals (phosphorus, potassium and sodium) are needed to help the glomerulus / nephrons interactive mechanisms keep that waste moving out of the blood and into the safety of the bladder.

According to Professor Roger G. Mark (the MIT Division of Health Sciences and Technology: Renal Physiology) the formation of urine actually begins "with a passive ultrafiltration process." That process includes the movement of water and "associated dissolved small molecules" is determined by hydrostatic and oncotic pressures. The capillaries alluded to earlier are one hundred times "more permeable to water and crystalloids" than are ordinary capillaries in the human muscle tissue. As the fluid runs along these capillaries, the pressure rises as a result of the loss of water in the process.

Meantime, the glomerular filtration rate (GFR) is working hard, pushing through 125 milliliters per minute, according to Mark's research materials. Most of the substances that are filtered through the glomerulus are in turn "reabsorbed" by the tubules of the kidney, becoming "interstitial fluid" and finally put back into the blood. That reabsorption process saves essential substances, including water, amino acids, electrolytes and glucose.

Mark makes the point on page 14 that key to the kidney's regulatory mechanism / function is its ability to "secrete hydrogen ion and potassium ion" to fully regulate the pH levels. It is important to the function of the kidneys that there be a good balance between the amount of water and sodium that are filtered daily. Mark writes that the amount of water and sodium that the kidneys filter every day can exceed the amount of water and sodium that the individual takes in "by more than a factor of 100!" The balance therein is fully dependent on "tubular reabsorption. On the subject of sodium balance, Mark explains that in a normal kidney scenario the amount of sodium taken in is matched by the amount excreted. and, of course the sodium that is excreted is done so in the form of "...sweat, saliva, and gastrointestinal secretions."

How do the kidneys affect other body systems? Besides keeping the blood free of harmful waste products, and providing a way to dispose of those wastes, the kidneys also do three important things for the body, the NKUDIC explains. One, they produce erythropoietin (EPO), which stimulates bone marrow and helps create red blood cells, which carry the oxygen throughout the body and keep humans alive and healthy. The kidneys also produce rennin, which effectively regulates a human's blood pressure. And another product of the kidneys is calcitriol, which according to NKUDIC is "the active form of Vitamin D," which assists the production of calcium for the bones and also calcium "for normal chemical balance in the body."

The importance of the kidneys cannot be overstated. This is a vital organ that not only provides cleansing and waste removal services, but keeps bones strong with supplies of calcium and regulates blood pressure as well as providing stimulus to bone marrow to produce healthy red blood cells.

Two healthy kidneys in a typical human usually means that they have normal "renal function" (your kidneys are operating the way they were intended to operate), according to NKUDIC information. Even with only one functional kidney, in many cases a person can live a normal life - which is why there are frequent opportunities for kidney transplants through willing donors.

Research has taught us that there are many things that can cause harm to kidneys, and many reasons for and causes of kidney failure. NKUDIC reports that there are hereditary kidney diseases but they may not be found out until a person is in adulthood. "Trauma" and some over-the-counter medicines can cause kidney failure and disease in some people. In fact, some products which are made from a combination of aspirin, acetaminophen and other painkillers like ibuprofen can put kidneys at risk, the research shows. The most recent research has delved into the problem that proteins in a person's diet, and various levels of cholesterol affect the normal functioning of kidneys.

Persons who are obese and have high blood pressure are potential candidates for kidney disease. And persons over the age of 65 are "more than twice as likely" to develop chronic kidney disease (CKD) than people who are between the ages of 45 and 65, NKUDIC continues. The best test of how effective one's kidneys are functioning is by testing the glomerular filtration rate (GFR). That is a test that reveals how much blood is being successfully filtered by the kidneys. The NKUDIC research show that a normal GFR rate is 90 and above, but when that rate falls to between 60 and 89, it indicates that the ability of the kidneys to filter blood effectively is declining. Further down to between 30 and 59 a person begins to experience anemia, and that person should be under a physician's care.

When the GFR is down to between 15 and 29 it may mean that the person requires dialysis, and may indeed need to have a catheter placed in the abdomen; short of that, the person whose GFR is that low, research shows, may actually require a donated kidney from a friend or family member. By the time the CKD has reached a point where the GFR is below 15, in order for that individual to maintain existence he or she will need major dialysis or a kidney transplant, which is expensive but it saves lives.

What do we understand about kidney disease? The NKUDIC clearinghouse estimates that 100,000 people in the U.S. experience kidney failure annually (it is called nephropathy). And the most common cause of nephropathy is diabetes - which accounts for around 45% of new cases of nephropathy. There are nearly 18 million Americans with diabetes, and of those people, about 150,000 also have kidney failure. Treating these patients is not inexpensive; the NKUDIC suggests that some $27 billion is wracked up in medical bills annually.

Recent Research: Harvard Medical School researchers (www.hms.harvard.edu),under the direction of and in cooperation with Dr. Ajay K. Singh have attempted to learn recently if epoetin alfa as an agent to correct the problem of anemia in chronic kidney disease patients. "They found no improvement in quality of life" in those patients treated with epoetin alfa; indeed, they learned that there was a "higher risk for serious cardiovascular events, including death," when epoetin alfa was used to "heighten hemoglobin levels" in patients with anemia due to chronic kidney disease (CKD), according to the Harvard Medical School data.

This particular research follows on the heels of "small tests" in which the higher hemoglobin levels are linked to better quality of life experiences for patients suffering from anemia and CKD. More than 1,400 patients across America in 130… [END OF PREVIEW]

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