Filtration-Circulation-the Human Kidney

Filtration and Circulation: Understanding the Complexity of the Human Kidney

  1. Kidney Contenders and Matthew A. Sparks, MD review the health of the human kidney 


  

“A bag of blood vessels” explains Matthew Sparks, MD, an Assistant Professor at Duke University School of Medicine in Durham, NC. “Twenty percent of each pumped unit of blood goes through the kidney.” The kidney is a highly vascular organ that filters waste, excess fluid and electrolytes from the body in the form of urine. Many people have a basic comprehension of their kidneys, but few understand the inner workings of the circulation and filtration of this complex, yet vital organ that contributes to sustainability of their lives.

“One of the tenets of healthy kidney function is maintaining normal blood pressure”. The kidneys function to restore proper blood pressure when things go quickly astray from either too low or too high of a blood pressure. This happens at the level of the arterioles- the small blood vessels that lead to and from the specialized filter of the kidney called the glomerulus. Our heart continually pumps oxygenated blood (oxygenated through our lungs) that circulates throughout our bodies through our aorta, the major artery in the human body. The blood not only delivers oxygen throughout our body, it is the fluid that transports our waste products, excess fluid and electrolytes as well. Our kidneys will filter our blood and remove the materials that our bodies not need. 

The waste materials must be separated from our blood by our kidneys; in order to do this effectively it is important to have sufficient kidney blood flow and blood pressure. The nephron, the powerhouse of our kidneys, receives urine after blood is filtered by the glomerulus. The glomerulus separates the waste products and passes them into the nephron where urine is ultimately created. Our kidneys only excrete materials that our bodies do not need. Our bodies need hydration to sustain cellular activity. “An acute illness like diarrhea (for example) results in dehydration and low blood pressure; as a result of the low blood pressure the blood vessels (arterioles) in your kidneys will constrict and decrease the amount of blood filtering through your glomerulus, causing less urine production through the nephron” says Sparks. For a healthy person, this is a normal response and allows for blood pressure to restore until the body can hydrate again or the acute illness ends. People who are diagnosed with chronic diseases, such as diabetes and hypertension for example, who are on blood pressure medication can experience severe side effects from angiotensin converting enzyme inhibitors, or angiotensin receptor blockers, or with NSAIDs and develop acute kidney injuries. In these situations, the kidneys can have a difficult time reacting to the low blood pressure and this in turn leads to prolonged low blood pressure and ultimately kidney injury. Therefore, it is important to talk to your doctor about what to do in these situations.

The kidney plays a multifaceted part of our health and an organ that medical science is still discovering new ways it operates. “Often times kidney functions are misunderstood,” says Sparks. “However, it is important to understand the important role the kidneys play in your health.”