The Nephron - Structure and Function of the Nephron

The Nephron
Credit: NIDDK
The nephron is the tiny filtering structure in your kidneys. Each of your kidneys contain more than a million tiny filtering nephrons that help clean your blood.

Function of the Nephrons

Your nephrons help:
  • Remove excess water,wastes and other substances from your blood.
  • Return substances like sodium, potassium or phosphorus whenever any of these substances run low in your body.

Each nephron is composed of two main structures: the glomerulus and renal (kidney) tubule.

The Glomerulus

The glomerulus is a tiny blood vessel or capillary, which looks like a ball of yarn. Actual filtering of your blood occurs in the glomerulus.

Each of your glomeruli acts like a sieve that helps keep normal proteins and cells in your bloodstream and allows wastes, excess fluid and other substances to pass.

The Tubule

The tubule, also called renal or kidney tubule, is a tiny tube where the wastes, extra fluid and other recyclable substances like sodium and potassium filtered out from the glomerulus pass through.

Image of Nepron showing the glomerulus and tubule
The Nephron: Showing the
Glomerulus and Tubule
Credit: NIDDK
Your kidneys measure out chemicals like sodium, phosphorus, and potassium and release them back to the blood to return to the body when need arises. In this way, your kidneys regulate the your body’s level of these substances. The right balance is necessary for you to function properly.
Damage to the Nephrons

Damage to your nephrons can lead to kidney disease. Conditions that can affect your glomerulus are:

Related Articles:

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What to do if you have Blood in your Urine ?

What You Should do if You Notice That Your Urine Has Blood

Having blood in the urine is termed as hematuria. In general, there are two types of hematuria. One type is, you have the problem but you do not notice it because there is very little blood and can be observed only under a microscope. This type is called microscopic hematuria. On the other hand, when it is obvious that your urine is red or you see that it is of tinge of red, pink, or cola-colored, the condition is called gross hematuria. This only means that you can see bloody urine with your naked eye.

Questions like, "What to do if you have blood in your urine? or Should I worry if I see blood in my urine?" are commonly asked questions. Having bloody urine makes people worry because, well, you don't normally see blood in your urine every time you urinate.

Hematuria is more of a sign of an underlying health problem than a disease in itself. It is important that you consult your doctor if you notice your urine has blood so that he or she can rule out other health conditions.


There are many causes of hematuria, some are not serious (e.g. due to menstruation and performing vigorous exercises) and usually goes away on its own while others require medical treatment.

  • Urinary Tract Infections (UTIs). Urinary tract infections are more common in women, but men can develop it too. You may get UTI when microorganisms like bacteria enter your urethra where they begin to multiply causing inflammation of the urethra, called urethritis — a type of UTI. Sometimes the bacteria travel up to higher urinary organs including the bladder, ureter, or kidney causing infection, as well.

  • Kidney or bladder stone. Some substances in your urine, especially when concentrated, may combine to form small crystals. Sometimes, these crystals may become larger as time passes in your kidney or bladder. A stone that lodges in smaller urinary tract structure can cause pain and hematuria.

  • Cancer. Sometimes, having bloody urine may be a sign of advanced cancer in any of your urinary organs. However, your doctor will be the one to determine whether the cause of your hematuria is cancer or not.

  • Medications. Some medicines may cause hematuria to happen, such as aspirin, heparin and certain antibiotics.

  • Exercise. Sometimes, the condition may be caused by performing strenuous or vigorous exercises. Experts are not really sure why exercise causes hematuria. Some believe that it may be due to trauma in the bladder, such as that occurs when the bladder is jarred during running.

In some cases, the actual cause cannot be found.


Your doctor will likely ask about your symptoms and will conduct a thorough physical examination. Sometimes, your doctor will recommend tests and procedures to look for the cause of your problem and to rule out other health problems. Examples of tests that your doctor might suggest include urine sample analysis; imaging tests, such as computerized tomography (CT) scan or magnetic resonance imaging (MRI); and cystoscopy.


Treatment of hematuria depends on the actual cause of the condition. For example, if hematuria is caused by a urinary tract infection, your doctor may prescribe antibiotics. If no serious health problem is found, no treatment may be necessary. However, your doctor may still recommend regular follow-up tests.

Related Articles:

National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC). Hematuria (Blood in the Urine) . Accessed on April 11, 2016.

National Library of Medicine (NLM). Urine - Bloody . Accessed on September 28, 2010.

Page Last Revised: April 11, 2016

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Top Tests for Kidney Disease Screening

Kidney disease may not present with symptoms during its early stages. In fact, your doctor may first detect that your have the condition when he or she performs a routine blood or urine test. There are simple tests that your doctor can use to detect if you have kidney disease. The National Kidney Foundation recommends the three simple tests to screen for kidney disease. It include blood pressure checking, spot checking fr protein or albumin in the urine, and calculating glomerular filtration rate (GFR) based on serum creatinine measurement.

Blood Pressure Measurement

Studies have established that uncontrolled high blood pressure can lead to the development of kidney disease. In some cases, it may already be a sign that kidney damage has already occurred.

The best way to know whether your blood pressure is too high or within normal range is to have it checked by your health care provider. Having a very high blood pressure can lead to many complications including stroke, heart attack, or kidney disease.

The National Heart, Lung and Blood Institute (NHLBI) recommends that people who have been diagnosed with kidney disease should try to keep their blood pressure below 130/80 and use whatever therapy is necessary, including lifestyle changes and medications.

Microalbuminuria and Proteinuria

Normally, your kidneys take out wastes from your blood but leave out protein, called albumin. If your kidneys are damaged, albumin may leak and become a part of your urine. This condition is called microalbuminuria, which can be a sign degenerating kidney function. As it worsens, albumin and other proteins in the blood leak out causing proteinuria.

A simple test that your doctor can do to test for protein is using a dipstick in a sample of your urine. The doctor can easily do this in his or her clinic during your visit. The color of the dipstick can tell your doctor whether protein is absent or present.

Glomerular Filtration Rate (GFR) Based on Creatinine Measurement

GFR is a measure of how effective the kidneys are filtering waste products from the blood. In the past, GFR calculation involves injection of a substance into the bloodstream, which is later on measured in a 24-hour urine collection. Now, scientist have found a new way of calculating GFR without injecting agents or collecting urine samples. The procedure, called eGFR, involves measuring of creatinine levels from a small sample of your blood. Creatinine is a waste product in the blood created by the normal breakdown of muscle cells during activity.

Normal range for blood creatinine levels may vary from laboratory to laboratory, but usually ranges from 0.6 to 1.2 mg/dL (milligrams of creatinine per one deciliter of blood). If your level is slightly above the range, you may not feel sick. However, this slight variation may indicate that your kidneys are not working at full strength as they should.

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), a creatinine level of 1.7 mg/dL for most men and 1.4 mg/dL for most women equates to 50 percent of normal kidney function.

The NIDDK website says, "The eGFR calculation uses the patient’s creatinine measurement along with age and values assigned for sex and race. Some medical laboratories may make the eGFR calculation when a creatinine value is measured and include it on the lab report."

Different stages of chronic kidney disease (CKD) can be determined based on the calculated eGFR. When the calculated eGFR is less than 15 milliliters per minute (mL/min), dialysis or kidney transplantation is necessary to sustain life.

Related Topics:
Understanding Glomerular Filtration Rate
Stages of CKD (Chronic Kidney Disease)
Online GFR Calculators for Adults and Children

National Institute of Diabetes and Digestive and Kidney Diseases. The Kidneys and How They Work. Accessed at on September 20, 2010.

National Kidney Foundation. Glomerular Filtration Rate (GFR). Accessed at on September 20, 2010.

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