Nephron

Nephrons are the structural and functional unit of Kidney. They are tiny filtration units of the kidney which are large in number. Read more..

Functioning of Nephron 

• The Nephron runs the network of small blood vessels known as capillaries that brings in impure blood containing many waste metabolic products and takes out pure blood that has been filtered by the nephron.
• The impure blood or the arterial blood comes into the kidney by the renal artery and the pure blood which has been filtered of all the metabolic and other waste products goes back to the body by other renal vein. 

Also Check -Structure of Nephron

Step By Step process of Functioning of Nephrons

The functioning of nephron has 3 mechanism to convert blood into urine which are

1. Filtration 
2. Reabsorption 
3. Secretion

After entering the kidney the renal artery gets divided into many small divisions until it reaches the smallest one that enters the nephron. 

Also Check – 12 Important Functions Of Kidney

Filtration 

• The Glomerulus is a tuft of blood vessels that is located inside the Bowman’s capsule. This tuft of vessels  greatly increases the surface area for filtration.
• The wall of the blood vessel outside the basement membrane of the glomerulus is in contact with the wall of the Bowman’s capsule.
• The wall of the Bowman’s capsule contains special types of cells which are known as  podocytes. Between these podocytes there are small caps which are known as the filtration slits. Together these three layers form the glomerular filtration barrier that acts like a filter paper.
• Blood coming in in this blood vessel that gets filtered through this glomerular filtration barrier to form the impure plasma that is passed down into the renal tubule.
• The glomerular blood pressure provides the driving force for water and solutes to be filtered out of the blood plasma and into the interior of the Bowman’s capsule called the Bowman’s space.
• 1/5 of the plasma is filtered in the glomerulus and the rest passes into the Efferent arteriole. 
• The Efferent vessel is of smaller diameter as compared to the afferent vessel. The blood is coming in through a vessel of larger diameter and leaving through a vessel of smaller diameter this increases the pressure inside the glomerulus which provides a driving force which makes this filtration possible.

Also Check – 9 Important Function of Nephron 

Reabsorption 

• The plasma that gets filtered into the Bowman’s space is known as the glomerular filtrate.
• The glomerular filtrate next moves into the renal tubules where it is further processed to form urine.
• It’s an important process as an initial glomerular fluid that is filtered into the Bowman’s space contains a lot of things that shouldn’t be excreted out with urine like sodium chloride glucose amino acids and excess water.
• The first part of the tubule is the proximal convoluted tubule(PCT) where approximately two-thirds of the filtered salts and water and almost all glucose and amino acids are Reabsorbed.
• All the essential content of glomerular filtrate is achieved by the method of a Reabsorption.
• The whole length of the renal tubule is surrounded with blood vessels known as the peritubular capillaries ,All that gets reabsorbed is then passed back into the blood circulation.
• The wall of the renal tubules has many types of protein channels that reabsorbs some of the important things that shouldn’t be excreted with urine.
• The filtrate then passes into the loop of Henle.
• The loop of Henle has some role in reabsorption of important salts of  Sodium, calcium, potassium, magnesium and magnesium.
• The main role of The Loop of Henle is in the concentration of urine.
• The loop of Henle has a descending limb and an ascending limb.
• The ascending limb of the loop of Henle contains special ion channels that pump out ions like sodium and chloride. 
• The ascending limb does not allow water to move out as it has no channels in its wall that allows the water to move out.
• The channels that allow water to move out are known as the Aquaporins. Aquaporins are present in the descending limb of the loop of Henle that makes it freely permeable to water.
•  All salty and the water will move out of the descending limb into the renal medulla and then eventually into the blood vessels. 
• It then gets reabsorbed and this is the reason why the loop of Henle is so long that is to give  for this water to secrete out. 
• After the loop of Henle the water then passes into the distal convoluted tubules .
• In the Distal Convoluted tubule again reabsorption of ions like calcium and Sodium takes place. 

Secretion

• In secretion the waste ions and hydrogen ions pass from the capillaries into the renal tubules.
• This is the final step in the formation of urine during which walls of the tube actively remove waste substances which are harmful to the body from the blood that has escaped filtration. 
• The secreted ions combine with the remaining filtrate and become urine. 
• The major substances secreted into the distal convoluted tubules include hydrogen ions, potassium ions and ammonium ions.
• The mechanism of secretion also takes place in the proximal convoluted tubules but to a lesser extent. 
• Wastes that get secreted from the proximal convoluted tubules include substances like urea, uric acid, creatine, ammonium ions and some other Drugs.