The Anatomy and Functions of the Kidneys

The Kidneys lie behind the Peritoneum, they are a pair organ.

The upper pole is at T12 (Spina; level)., and the lower pole is L3 (right kidney).

What makes the L3 lower is because of the presence of the liver on the side.

The kidney faces the spine, oriented with a concave surface.

The size of kidney is 11cm long and weighs about 150g approximately

The Hilus makes the ureter and the main blood vessels and nerves access the kidney. There are two distinct regions by the cut surface of the kidney. There is the cortex, which is a dark outer region and a pale inner region named medulla. Cover by the fibrous capsule is the outer cortex. The pad fat covered by the kidney gives us protection against injury. The Cortex also provides nephrons filtering and the reabsorption components while the concentration and diluting collection of nephrons ducts system are being contained by the medulla. Moving into the bladder from the ureter is the duct that funnelled urine from the pelvis at the heart of the medulla.

Nephrons is a functional unit of kidney, in each kidney there Is 1million nephrons.

 Component of Nephrons

Bowman capsule – The site of filtration

The Proximal convoluted tubule – site of reabsorption and secretion

Loop of Henle – the site where concentration and dilution of urine mainly occur

Distal convoluted tube – The fine-tuning site for reabsorption and more secretion

Collecting duct –  this is vital to the urine concentration and movement of urine into the renal pelvis

The Vital functions of Kidneys

The important functions of kidneys are that they to get rid of end product metabolism and to regulate the electrolytes found in the body fluid.

The Excretion:

Excretion of waste product from metabolism

The Regulatory of:

Blood pressure

Acid base balance

Electrolyte balance

Body fluid osmolarity

Body water volume

The Metabolic function of:

Vitamin D

Renin production

Erythropoietin production

In Order to maintain the consistency of our body fluid, we need urinary volume, urinary concentration and urinary content.

Urine Volume

Urine is produced by a healthy person per day which can vary from 300ml if there is less fluid intake or there is water loss from the body e.g. diarrhoea.

Healthy urine output should not drop below 300ml per day because to excrete daily load of toxic waste product, the body needs 300ml of urine. The amount of waste product to be removed by the kidney, the increase in the minimum urine volume.

The average urine output per day is 1500ml. It is very important to maintain constant body fluid volume to help with the excessive heat that causes sweating, colonic infection causing diarrhoea or excessive taste and water ingestion.

 Normal Input and Output of Fluid

Input mls                                           Output mls

Water               1500                        Urine                               1500

Food                  500                        Insensible loss   lungs  400 + skin 400 (800)

Metabolism        400                      Faeces                           100

Total                 2400                                                         2400           

Input (Water, Food and Metabolism) –  Output (  Urine, lungs, Skin and Feaces)     

 Concentration of Urine                                                              

To excrete a fairly fixed solute volume daily in a variable volume of water, the kidney must have the ability to concentrate or dilute the urine. On a very summer day, when little amount of fluid has been consumed, urine will be dark in colour and of low volume. However, if beer is been drunk at a party larger amount of urine are passed.

The diuretic effect of beer is not only the amount of consumption but also as a result of alcohol in beer which supresses the secretion (from the posterior pituitary glands) of anti-diuretic hormone (ADH, also known as Vasopressin), this hormone prevents diuresis.

Renal disease is always a sign that the mechanism that controls the concentration or dilution of urine is being affected causing individuals some form of dehydration or fluid overload.

 Content of Urine

Ions: Sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate and ammonium.

Metabolic waste: Urea, creatinine and uric acid.

Drug Metabolic: Mostly, metabolites of pharmacological agents are excreted from the body through the kidney. Although, many are detoxified in the liver first.



Thomas N. (2003) ED.Renal Nursing Elsevier , UK

Amiel GE, Atala A. (1999) Current and and future modalities for functional renal replacement Urol Clin North AM 235-246.

Editorial Transplantation Nephrol News Issues 2000: (14)66