The Urinary System

Last week in Part 10 we examined the Digestive System where food and liquids are brought into the body and processed for use as nutrients and energy.  The end of the digestive system revealed how the solid waste is removed through the large intestine and out the anal opening.  This week we will look at the urinary system that is responsible for the removal of other byproducts and waste materials.

In the course of living and breathing, the human body produces a number of substances that if not removed from the body would soon become toxic and kill the body.  Breathing creates carbon dioxide which is removed via the lungs.  The metabolism of food products creates a number of solid waste materials that are removed via the end of the digestive tract.  The metabolic activities throughout the body produce nitrogenous byproducts such as urea, uric acid as well as other toxins that must be filtered out and removed.  The main function of the urinary system is to filter out and remove the toxins and nitrogenous waste products. .

The urinary system consists of: a pair of kidneys, a pair of ureters, bladder, sphincter and the urethra.

I.          Kidneys – Each person, under normal conditions are born with two kidneys.  They are located just below the ribcage toward the back of the body with one kidney on each side of the spinal column.  Although the kidneys are composed of a number of different parts, the main functions are carried out in the specialized cells called nephrons.  Each kidney has approximately one million nephrons filter the blood to remove the wastes and toxins.  The functions of the kidneys include:

A.        Filter Blood – The kidneys filter a number of substances out of the blood including ammonia, urea, uric acid, creatinine, bilirubin, lead, mercury, pharmaceutical drugs and other chemicals and toxins that are not normally found in the body.

B.        Synthesis of Vitamin D – The biologically active form of vitamin D known as calcitriol is synthesized in the kidneys into a hormone that then circulates throughout the body.  The calcitriol helps regulate the amount of calcium and phosphorus in the bloodstream which helps with the growth and health of the skeletal system.

C.        Production of Red Blood Cells – The kidneys do not actually produce red blood cells.  There specialized cells in the kidneys that detect the amount of oxygen in the bloodstream.  When the oxygen levels start to get low, these cells release a hormone known as erythropoietin which helps to stimulate the production of red blood cells in the bone marrow to help increase in the oxygen level in the blood.

D.        Regulation of Free Radicals – The kidneys play an important role in regulating the amount of free radicals found in the bloodstream.  If left unchecked, free radicals can lead to damage of cell walls and DNA resulting in serious health issues.  Free radicals are atoms, ions or molecules with unpaired electrons.

E.        Regulation of Blood pH – The blood’s pH is kept around 7.4, making it slightly alkaline.  The kidneys play an important role in maintaining the pH level and preventing it from getting more alkaline or becoming acidic.

F.         Controlling Blood Pressure – The kidneys help control blood pressure in two ways:

1.         Production of Renin – The kidneys produce an enzyme known as renin which is used to activate the renin-angiotensin-aldosterone (RASS) pathway that helps to regulate blood pressure.

2.         Regulation of water in Blood – The amount of water in the blood can have a direct effect on the blood pressure.  The kidneys regulate the amount of water in the blood to help control the pressure.

II.         Ureters – The ureters are muscular tubes that connect the kidneys to the bladder.  They carry the urine produced by the kidneys to the bladder.

III.        Bladder – The bladder or urinary bladder is a muscle lined sac that stores urine.  When it is time to eliminate the urine, the muscular lining contracts forcing the urine to pass through the sphincter and into the urethra.

IV.       Sphincter – Also known as the urinary or urethral sphincter, refer to a series of circular muscles that encircle the upper part of the urethra just below where it connects to the bladder.  The main function of the sphincter is to close off the opening to the urethra to prevent the flow of urine.

V.        Urethra – The urethra is a tube that carries the urine from the bladder to the urethral opening where the urine leaves the body.

The urinary system is a marvelous designed system to filter out and remove hazardous waste and byproducts from the body.  The system is so efficient that it can operate sufficiently on just one kidney.  Many people today donate a kidney to someone else whose kidneys have failed and continues to lead a normal life.

Such an amazingly designed system that fits and works so well with the rest of the human body’s systems is a tribute to the infinite wisdom of our Creator God.

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