KIDNEY. What is a kidney? functions of the Kidney:
The kidneys are two reddish-brown, bean-shaped structures that lie asymmetrically on the posterior dorsal body wall of the lumber-upper region of the abdomen below the adrenal gland.

At the concave edge is a depression called the helium. Arising from the helium is a small tube called the ureter.
The helium also serves as the point of entry of the renal artery and leaving of the renal vein.

They are bean-shaped organs located on either side of the spine, just below the rib cage, and are roughly the size of a fist. The main function of the kidneys is to filter waste products and excess fluid from the blood to produce urine. Here are some key aspects of the kidneys:

  1. Filtration: The kidneys filter the blood to remove waste products, excess water, and toxins. This filtration process occurs in tiny units called nephrons, which are present in the kidneys.

  2. Fluid and Electrolyte Balance: The kidneys help regulate the balance of fluids, electrolytes (such as sodium, potassium, and calcium), and acid-base levels in the body. They play a crucial role in maintaining proper hydration and the stability of various bodily functions.

  3. Blood Pressure Regulation: The kidneys contribute to blood pressure regulation by adjusting the amount of water and salt reabsorbed into the bloodstream. They release a hormone called renin, which plays a role in controlling blood pressure.

  4. Waste Product Excretion: The kidneys eliminate waste products produced by the body\’s metabolism, such as urea, creatinine, and uric acid. These waste products are dissolved in urine and excreted from the body.

  5. Red Blood Cell Production: The kidneys produce a hormone called erythropoietin, which stimulates the bone marrow to produce red blood cells. Red blood cells are responsible for carrying oxygen to various tissues and organs in the body.

  6. Vitamin D Activation: The kidneys convert inactive vitamin D into its active form, which is necessary for the absorption of calcium and the maintenance of bone health.


The ureter connects the kidney to the urinary bladder and from the bladder to the urethra. The urethra opens through the male organ and separately in females as the urinary tract.


The kidney is made up of two distinct regions:

the outer cortex and inner medulla. This contains thousands of urinary tubules. Each malpighian tubule consists of a malpighian body situated in the cortex and convoluted tube.


Each malpighian body consists of a cup-like chamber,
 into which a knot of blood capillaries, the glomerulus, fit. Beyond the malpighian body, each tubule makes a U-shaped loop into the medulla, re-enters into the cortex and bends again into the medulla where its course is completed.
The U-shaped loop is Henle’s loop representing kidney functions


The tubule transverses both regions and opens at the tips (papillae) of triangular-shaped masses called pyramids, which open into the pelvis.


The functions of the kidney include
(1) Excretion: The kidney helps to remove unwanted nitrogenous wastes like urea, ammonium compound, water and salts from the body
(2) Detoxification: The kidney also helps to eliminate poisonous substances from the body as excretion, e.g toxins, drugs and alcohol as a kidney functions
(3) Removal of excess glucose: The kidney also aids in the removal of excess glucose from the body

(4) Maintenance of acid/base balance: The kidney helps to maintain the blood pH and osmotic pressure. Normal urine is slightly acidic.
(5) Osmo-regulation of the body: The kidney also functions in the osmoregulation of the body. i.e keeps the concentration of the blood plasma and conditions of the body cells fairly constant.
(6) Conservation: The key aids the conservation of some useful materials by re-absorbing them from the glomerular filtrate which is the first step in urine formation. Materials conserved include water, glucose, sodium ions, chlorine ions and Vitamin C.

kidney overview

The kidneys are two bean-shaped organs in the renal system. They help the body pass through waste as urine. They also help filter blood before sending it back to the heart.

The kidneys perform many crucial functions, including:

maintaining overall fluid balance
regulating and filtering minerals from the blood
filtering waste materials from food, medications, and toxic substances
creating hormones that help produce red blood cells, promote bone health, and regulate blood pressure


Nephrons are the most important part of each kidney. They take in blood, metabolize nutrients, and help pass out waste products from filtered blood. Each kidney has about 1 million nephrons. Each has its own internal set of structures–kidney functions

Renal corpuscle

After blood enters a nephron, it goes into the renal corpuscle, also called a Malpighian body. The renal corpuscle contains two additional structures:

The glomerulus

. This is a cluster of capillaries that absorb protein from blood travelling through the renal corpuscle.
The Bowman capsule. The remaining fluid, called capsular urine, passes through the Bowman capsule into the renal tubules.

kidney functions of Renal tubules

The renal tubules are a series of tubes that begin after the Bowman capsule and end at collecting ducts.Each tubule has several parts:

Proximal convoluted tubule.

This section absorbs water, sodium, and glucose back into the blood.

Loop of Henle. This section further absorbs potassium, chloride, and sodium into the blood.

Distal convoluted tubule.

This section absorbs more sodium into the blood and takes in potassium and acid.

By the time fluid reaches the end of the tubule, it’s diluted and filled with urea. Urea is a byproduct of protein metabolism that’s released in urine.

kidney functions of the Renal cortex

The renal cortex is the outer part of the kidney. It contains the glomerulus and convoluted tubules.

The renal cortex is surrounded on its outer edges by the renal capsule, a layer of fatty tissue. Together, the renal cortex and capsule house and protect the inner structures of the kidney.

Renal medulla of the kidney

The renal medulla is the smooth, inner tissue of the kidney. It contains the loop of Henle as well as renal pyramids.
Renal pyramids

Renal pyramids are small structures that contain strings of nephrons and tubules. These tubules transport fluid into the kidney. This fluid then moves away from the nephrons toward the inner structures that collect and transport urine out of the kidney.

Collecting ducts of the kidney functions

There’s a collecting duct at the end of each nephron in the renal medulla. This is where filtered fluids exit the nephrons.

Once in the collecting duct, the fluid moves on to its final stop in the renal pelvis.

Renal pelvis of the kidney

The renal pelvis is a funnel-shaped space in the innermost part of the kidney. It functions as a pathway for fluid on its way to the bladder

Calyces part of the kidney

The first part of the renal pelvis contains the calyces. These are small cup-shaped spaces that collect fluid before it moves into the bladder. This is also where extra fluid and waste become urine.

The hilum is a small opening located on the inner edge of the kidney, where it curves inward to create its distinct bean-like shape. The renal pelvis passes through it, as well as the:

Renal artery. This brings oxygenated blood from the heart to the kidney for filtration.
Renal vein. This carries filtered blood from the kidneys back to the heart.

Ureter function in the kidney

The ureter is a tube of muscle that pushes urine into the bladder, where it collects and exits the body.

Kidney conditions

Because of all of the vital functions the kidneys perform and the toxins they encounter, the kidneys are susceptible to various problems.

Some of these conditions include:

chronic kidney disease
kidney failure
kidney stones
acute nephritis
polycystic kidney disease
urinary tract infections
kidney cysts
nephrotic syndrome

Learn more about some of the most common kidney diseases.
Symptoms of a kidney problem

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