Because the Kidneys are one of the most vital organs in the human body after the heart, their absence or malfunction can lead to extreme illness and even death. The Kidney has a very complicated structure and complex functions for this reason. The Kidneys purify waste materials and toxic substances from the blood, thereby keeping the body clean and healthy. The Kidneys create urine by this process, and sends it to the ureter, where it passes through the urethra, and out of the body.

People generally have two Kidneys. The Kidneys are located deep in the upper abdomen on either side of the spine, and are protected by the rib cage. They are bean shaped, and are about 10 cm long, 6 cm high, and 4 cm wide in normal adults. The Kidneys create urine from filtered blood, and they send the urine to the bladder through the ureter. The ureter is a hollow muscular tube that is about 25 cm long. The bladder is a hollow, muscular organ which lies in the lower back part of the abdomen. It temporarily stores urine.


The adult bladder can store between 400 to 500 ml of urine at any one time. The urine in the bladder leaves the body through urination. The ureter is short in females, and long in males.

The Kidneys exist to filter blood and deposit the harmful wastes into a waste liquid called urine. These harmful wastes include extra salts, waste, chemicals, and other harmful substances which the human body does not need. The Kidneys do this by purifying blood. All food contains protein which is essential for cells to grow and repair themselves, however this protein produces harmful waste products during metabolism. The Kidneys filter these waste products and proteins, and deposits them in urine.

Two key waste products that the body produces during the process of metabolism are creatinine and urea. Their quantities in the human body are easily measurable, and they will be in high quantities in human blood when the Kidneys fail. Their value in a blood test is directly correlated with how well the kidneys are functioning.

The kidneys also remove excess fluid from the body which would otherwise interfere with key body functions. This fluid leaves the body in the form of urine. The kidneys ensure that the body retains the correct amount of fluid needed for proper metabolic functions. People with kidney failure have kidneys that are no longer able to rid the body of excess fluid, they experience swelling as a result.

The kidneys maintain the desired balance of chemicals and minerals, such as: sodium, potassium, hydrogen, calcium, phosphorous, magnesium, and bicarbonate. The kidneys also ensure that that the fluid in the body contains the right concentrations of these chemicals and minerals. This is key because changes in the levels of these chemicals and minerals can seriously and negatively affect key body functions. For example, changes in the levels of sodium can affect sensory abilities, while changes in the levels of potassium can seriously affect the rhythm of the heart and the functioning of its muscles. The human body needs the right balance and levels of magnesium and calcium for healthy bones and teeth.


The kidneys produce many hormones which regulate the balance of water and salt in the body. These in turn regulate the bodys blood pressure. Some of these hormones are: renin, angiotensin, aldosterone, prostaglandin, etc…People with kidney failure often times have high blood pressure because of the imbalance of hormone production in their bodies, and their bodies failure to regulate the balances of salt and water properly.

The kidneys produce erythroypoietin which helps the kidneys produce the red blood cells that the body needs to survive. When the kidneys fail, they dont produce enough erythroypoietin which in turn leads to a marked decrease in red blood cells. The person becomes anemic as a result because his or her blood has low hemoglobin. If a person is in renal failure, iron and vitamin supplements will not improve his or her anemia.

The kidneys convert vitamin D into its active form. This is vital for the absorption of calcium from food, liquids, and vitamin supplements. People with renal failure have bones that dont grow as much because their bodies do not make as much active vitamin D. Children with renal failure may even experience growth retardation as a result.

The adult bladder can store between 400 to 500 ml of urine at any one time. The urine in the bladder leaves the body through urination. The ureter is short in females, and long in males.

The kidneys filter and purify the blood and produce urine as a byproduct. The urine contains the waste products and harmful materials that the body no longer needs. The kidneys filter and purify 20% of the total blood volume pumped by the heart every minute, which is 1,200 ml. The heart purifies 1,700 liters of blood every day. The kidneys contain small sacs called nephrons which filter and purify the blood. Each kidney contains one million nephrons which are composed of glomerulus and tubules.

The glomerulus filter blood because they have very tiny pores which are capable of filtering out certain organic waste products and harmful substances. While water and small matter can easily pass through the pores, larger materials like: red and white blood cells, platelets, and proteins cannot. Therefore, they are not present in the urine of people with healthy kidneys.

The glomeruli produce approximately 125 ml of urine a minute. They produce 180 liters of urine a day. The urine contains waste products, harmful substances, excess glucose and other useful substances which the body does not need to use. The kidneys reabsorb 99% of the 180 liters of urine produced daily, and only 1.8 liters leaves the bladder as urine everyday.

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