The Nephron
The basic functioning unit of the human kidney is the nephron. The kidney consists of over 1 million nephrons that carry out the vital functions of the kidney. The nephron consists of two components; the glomerulus, which is the vascular side of the filtering system, and the renal tubule, which is the urinary side of the filtering system. The nephron is responsible for the filtration of the blood after it enters the renal artery, which branches into tiny arteries to form the nephron. The nephron is also responsible for selecting the substances that the body will use and reabsorbing them. The nephron sorts through the good and bad substances, filters out the bad and reabsorbs the good. The bad, which are the wastes that the body cannot use, is excreted to start the formation of urine. Urine is what remains after the removal of wastes from the blood, resorption of water, nutrients, ammonia and after the nephron break downs drug products. After this process of resorption and removal of waste products, urine exits the nephron by way of tubes called ureters, and then onto the bladder. The urine is stored here until urination. The urine is exited out of the body by way of a tube called the urethra. Healthy kidneys produce anywhere from 1-2 liters of urine per day.
The kidney cells are highly sensitive to low oxygen levels in the blood. When low oxygen levels are detected, the cells produce and release a hormone called erythropoietin. Erythropoietin travels to the bone marrow and stimulates red blood cell formation. Red blood cells are responsible for the transport of oxygen. When the kidney is damaged, it cannot produce erythropoietin properly. When this occurs, anemia results.
Blood Pressure Maintanance
The kidneys also help keep the blood pressure maintained. Increasing blood volume can cause increasing blood pressure. The kidneys act to remove fluid from the blood stream, forming urine and lowering blood pressure. When blood pressure is low, the kidneys release the enzyme renin into the blood. Renin forms angiotensin, which causes a strong vasoconstriction, increasing blood pressure. Angiotensin activates the adrenal cortex to release the hormone aldosterone. Aldosterone helps the kidney to maintain the sodium (salt) levels in the blood, increasing blood volume, and thus blood pressure. In addition to maintaining blood pressure and urine formation, the kidney also helps to maintain calcium for bones.
The kidney is considered an endocrine gland, because it secretes hormones within the organ. The kidney secretes three hormones: erythropoietin, renin and calcitriol, which is the active form of vitamin D. Remember, kidneys keep track of our sodium content, and if you take in excess amounts of sodium, your kidneys will have to work extra hard at maintaining a safe level for you to stay healthy.
The kidney performs many intricate tasks 24 hours per day, everyday. Help your kidneys perform their duties by watching sodium intake, drinking plenty of water everyday and keeping sugar to a minimum. Eating green leafy vegetables will be well respected by your kidneys.
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