The kidneys are the major organs of this system and are responsible for a variety of critical functions. For example, they filter the blood and reabsorb essential chemical substances, regulate blood volume and blood pressure, manufacture erythropoietin, which triggers the formation of red blood cells, produce urine and excrete it from the body.
Components
The major components of the urinary system are:
- Pair of Kidneys
- Pair of Ureters
- Urinary Bladder
- Internal Sphincter
- Urethra
- External Sphincter
- Urinary Meatus
A person can easily function with only one kidney, which is why the kidney is one of the few organs that can be taken from a live donor.
Processes
Urine Formation
The formation of urine is the responsibility of the kidneys. Each kidney has a tube-like structure emanating from it called the ureter that collects the urine and drains it into the bladder where it is stored until the person urinates.
Varying from individual to individual in frequency is the urge to urinate; some individuals have a very sensitive urge trigger and will need to empty their bladders more frequently than others do.
From the bladder urine empties into a tube-like structure called the urethra. The bladder neck has an internal sphincter muscle that controls urine flow. When a person feels the urge to urinate, the external sphincter muscle relaxes allowing the passage of urine from the bladder into the urethra and out of the body via the urinary meatus.
Blood Filtration
The kidneys are also responsible for the filtration of blood. Simply stated, blood is filtered through small vessels (capillaries), which will reabsorb important substances like glucose and amino acids, while others like urea, are waste products that must be removed and excreted via urine.
pH Balance
The kidneys monitor the body’s acid-base balance (pH) and will immediately set into motion mechanisms to normalize it. This is a very complicated system with other buffering mechanisms in place, for example, in the blood and respiratory system.
Red Blood Cell Production
The kidneys manufacture a hormone called erythropoietin, which when triggered, will stimulate the production of red blood cells.
Blood Pressure Regulation
The kidneys play a critical role in blood pressure regulation by controlling the fluid volume outside the cells and by implementing the renin-angiotensin-aldosterone mechanism, which chemically helps to control problematic fluctuations in blood pressure.
Vitamin D Activation
The kidneys aid the process of calcium metabolism by activating one of the forms of vitamin D, 1,25-dihydroxycholecalciferol.
Kidney Function Tests
Often problems with the kidneys are subclinical meaning physical manifestations are not visible until the damage is already in progress. Therefore, laboratory and diagnostic tests provide the key to determining kidney health.
Blood and Urine Tests
First, blood tests are ordered to assess the kidneys' ability to remove metabolic wastes from the blood and to maintain normal electrolyte and pH composition of the blood. Second, urine sample tests assess the color, odor, and composition of urine. Third, a specific gravity test assesses hydration levels and the kidney’s ability to concentrate urine.
Diagnostic Tests
A cystoscope is an instrument that allows the doctor to see structures of the urinary system like the urethra and bladder for example. Another important function of this instrument is the ability to remove small growths and tissue samples to scar tissue and stones.
One test that is commonly ordered is the x-ray, which shows images of the kidneys, ureters, and bladder. These radiological images provide the doctor with positional information regarding the size, shape, and location of the organs.
Another imaging device called an ultrasound uses the reflection of high frequency waves to visualize parts of the body not captured by traditional x-rays. An ultrasound is often indicated when a doctor needs to diagnose disorders of the system, for example, structural changes, kidney stones, abscesses, and fluid accumulations.
In conclusion, the urinary system does so much more than produce and excrete urine. Many problems can occur within this system and specific diagnostic and laboratory tests are used to confirm or rule-out a suspected diagnosis. Regular medical checks of the kidneys and corresponding organs are prudent in maintaining optimal health.
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