Kidney: the blood filtering organ in human body

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Kidneys are a pair of bean-shaped organs at the back of the abdomen. The size of each kidney is about 4 to 5 inches long and the primary function is to filter blood by regulating the balance of electrolytes within blood and maintaining pH homeostasis. The kidneys also remove waste by taking out excess organic molecules from the blood. Besides these, the organ is responsible for controlling the fluid balance of body, regulating blood pressure through salt and water balance and sustaining acid-base balance. As kidneys filter blood, urine is created and collects in the pelvis of kidneys. Pelvis is a funnel-shaped structure that drains down tubes, known as uterus, to the bladder.

The kidneys serve as a natural blood filter and eradicate water-soluble waste which is averted towards the bladder. While producing urine, kidneys excrete urea and ammonium, commonly referred to as nitrogenous wastes. Glucose, water and amino acids are reabsorbed by the kidneys. Hormones such as calcitriol and erythropoietin are produced in kidneys. Another important enzyme called rennin is also formed in the kidneys; however this enzyme has a negative feedback.

Functions of Kidney

Each kidney has about a million units called nephrons and each nephron is a microscopic filter for blood. Without experiencing any prior symptoms or problems, one can lose about 90% of kidney functions. In this context, the main functions of a kidney are:

  • Waste Excretion: The kidney filters out varieties of waste products that body does not require. All toxins, excess salt and urea get metabolized into urine. Urea is synthesized in the liver and transported to the kidneys through blood, for removal. It requires several independent nephron characteristics to operate. Also, passive countercurrent exchange by the blood vessels, supplying blood to the nephrons is important for this function.
  • Vital nutrients re-absorption: Kidneys also function to re-absorb essential nutrients. At normal plasma levels, glucose is completely reabsorbed in the proximal tubule. Plasma levels of 350 mg/dL completely saturate the transporters and as a result glucose is lost through urine. Plasma glucose levels of 160 are sufficient for allowing glucosuria, an important clinical clue to diabetes mellitus.
  • Acid-base homeostasis: With the help of lungs, kidneys regulate acid-base homeostasis and maintain relatively stable pH values. While the lungs take an active role in acid-base homeostasis by preserving carbon dioxide concentration, kidneys perform two crucial roles: reabsorbing and regenerating bicarbonate from urine and excreting hydrogen ions and fixed acids into urine.
  • Blood pressure regulation: Kidneys require constant pressure for filtering blood. When the pressure drops down, kidneys increase it. It produces angiotensin, a blood-vessel constricting protein which also alerts the body to retain sodium and water. Constriction of protein and retention of water and sodium help to restore normal blood pressure levels.
  • Osmolality regulation: Kidneys re-absorb water and increases urine concentration when osmolality increases, causing the posterior pituitary gland to secrete antidiuretic hormone (ADH). When plasma osmolality is detected by hypothalamus, it communicates directly to the posterior pituitary gland, following which kidneys work to return the plasma osmolality to its normal levels.
  • Hormone secretion: Kidneys secrete various hormones such as erythropoietin and rennin, an enzyme. When oxygen level decreases in the tissues (the condition known as hypoxia), erythropoietin is released in the renal circulation. Kidneys also stimulate the production of red blood cells in the bone marrow. Rennin regulates aldosterone levels.

How to keep kidneys healthy?

Now that kidneys perform some of the most significant functions, it is necessary to keep kidneys healthy, which can be done in the following ways:

  • Hydration, without overdoing: Normal intakes of water and other healthy liquids enhance kidney’s efficiency in executing its functions.
  • Eating healthy food: Healthy and moderate eating habits controls blood pressure and weight, which helps kidneys to work in good condition.
  • Regular exercise: Exercising in early morning is a good discipline for maintaining healthy kidneys. However, one must not over-workout, which can cause breakdown of muscle tissues.
  • Quitting smoking: As said smoking is injurious to health, it first affects the liver and kidney, disrupts its normal functioning and brings worse health conditions.

Importance of healthy food and water for maintaining good kidneys

Kidneys, being on the most significant parts of the body, require proper maintenance and care. Hygienic food and sufficient water are most important for having good kidneys. Often, kidney stones develop when minerals get deposited in urine. In order to avoid this, one must consume diet which has less salt and oxalate-rich food.

Amount of water intake is compulsory, especially for those exercising frequently. Besides these, the following intakes will ensure healthy kidneys for life.

Tips to keep Kidneys Healthy

  • Fruits and Vegetables: Fruits like grapes, blueberries and cranberries improve kidney’s function. Among vegetables; beets, onions, fennel, celery, asparagus, string beans and spinach enhances power of kidneys and prevents kidney-related diseases.
  • Iron-Rich Foods: Iron-rich food like green leafy vegetables and eggs increase iron-intake. As a result, kidneys can produce more number of red blood cells and prevent chronic kidney diseases. This also helps in maintaining proper red blood cell count and efficient kidneys.
  • Fluids: Diluted urine is another sign of healthy kidneys and for this, staying hydrated in very essential. Apart from water, fruit juices and ginger also keeps body hydrated, all the time. Beverages must be restricted to one or two cups per day, since it dehydrates body.
  • Low-Potassium Foods: Kidneys also keep a check on potassium levels. High levels of potassium invite kidney damages and other acute problems like strokes and heart attacks. Low-potassium food like noodles, rice, pasta apples, corn, beans, eggplant, cookies without chocolates and nuts, zucchini, peas, pepper and pears must be consumed for fine effective kidneys.

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