What is Reabsorption?

Reabsorption is a process in the kidney. Also, if more specific, then it is the process of the Nephrons. As the process of the kidney is the combination process of the Nephrons. As Nephrons are the functional unit of the kidney, so it is being used to excrete unessential elements from the body. And Reabsorption is one type of subprocess. There are mainly three sub-processes in the urine formation process. Reabsorption is one type of subprocess. Other than the Reabsorption, there is a Filtration & Secretion process present.

The word “Reabsorption” means to again absorb all the elements. After the filtration process, this process starts in the kidney or the Nephrons. In the filtration process, polluted blood comes to the Glomerulus via the Afferent Blood Vessels. There all the elements from the blood come into the renal corpuscles region. Only the elements of the blood remain there. So, the blood is now pure. And it goes out by the Efferent Blood Vessels.

Now, all the substances that come into the Renal Corpuscles are not harmful. Among them, there are a large number of substances that are very useful for the body. The filtration process can’t pick up only the harmful elements of the body. So, all the elements come to the Nephrons. Now, Nephrons return those helpful elements to the body by absorbing those elements. This process is known as Reabsorption. It is seen that 180 Liter/Day of substances are comes to the Nephrons. But among them, only 1.8 Liter/Day substances are selected as harmful. So they are only removing from the body. So, the process that helps to return the essential elements from the Nephrons to the body is known as Reabsorption.

Process of Reabsorption in Kidney

Mainly the Reabsorption process is executed in the tube of the Nephrons. This means this process can be highly visualized from the Proximal Convoluted Tubule to the Distal Convoluted Tubule. So, Proximal Convoluted Tubule, Henley’s Loop & Distal Convoluted Tubule are the area where the Reabsorption takes place. Also, there is one more important part is the blood vessels. The Efferent Blood Vessels are situated very near to these tubes. There is a capillary network near this tube. This capillary structure is made up in such a way that the tubes & the layer of the blood vessels are close to each other. So, the substances can easily diffuse by the layer of the blood vessels. Hence, they can able to return to the body using the blood vessels.

• Reabsorption in the Proximal Convoluted Tubule (PCT): Reabsorption mainly takes part in the PCT region. Here, 65% of the elements are reabsorbed & returned to the body. Here, glucose, and amino acids are reabsorbed. Along with that, some ions are also reabsorbed here. Ions are the most important for the easy functioning of the body. Mainly, Na⁺, K⁺, Cl^–, Mg²⁺, etc, ions are reabsorbed from the PCT & return to the body. The main importance of PCT is that it can able to reabsorb Glucose. Glucose is the only element that can be absorbed by the PCT. 98% glucose is reabsorbed from here. Other tube-like structures don’t have this type of ability. And glucose is the main energy provider to the body. So, from this context, PCT is very important.
• Reabsorption in the Henley’s Loop: In Henley’s Loop, some more Reabsorption takes place. It is the region where mainly water is reabsorbed. Here mainly 15% of the substances are reabsorbed. Among them, the large amount is water. Along with the water, it can reabsorb other elements also. Nearly, 25% of Sodium, Calcium, Potassium, and 55% of Magnesium are reabsorbed from here. Water is reabsorbed to concentrate the urine formation. Water is also an essential element in the body. Removing excess water from the body will reduce the body’s energy. This might create dehydration. So, during dehydration, the water is reabsorbed in high amounts from this region. So, the urine gets concentrated.
• Reabsorption in the Distal Convoluted Tubule (DCT): It is the region where there is little presence of the Reabsorption process. Mainly the DCT is known for another process Secretion. But, this place is known for the absorption of different ions. Like, Na⁺, K⁺, and HCO₃^– are reabsorbed from this region. Nearly, 10% of the remaining substances are reabsorbed from here. After the concentration of the urine, there is no chance to more reabsorb from that concentrated element. It is now becoming ready to remove from the kidney. That is the reason, the here Reabsorption process is very less in percentage.
• Reabsorption in the Collecting Duct: The collecting Duct doesn’t also perform in the Reabsorption process. In a very less amount, this area can reabsorb the ions from the substances. Otherwise, there is no Reabsorption function in the collecting duct. Some ions like Na⁺, K⁺, Cl^–, and HCO₃^– are reabsorbed here. Nearly, 4% of the remaining substances are reabsorbed from here.

The kidney is the organ that helps to eliminate harmful substances from the body. The process that helps to eliminate those substances is known as the excretion process. So, the kidney is an excretory organ. This organ helps to balance the substances in the body. The human body also has a kidney. In the human body, there are two kidneys are present. They are situated in the posterior wall of the abdomen cavity. They are situated on both sides of the vertebral column. These bean-shaped organs play an important role in the human body.

If the kidneys are intersects in two parts, there two major divisions can be witnessed. They are the Cortex & Medulla. The cortex is the region outside of the kidney. They are the outer portion of the kidney. And the inner part is known as the Medulla. There are some pyramids-like structures are present. They are known as the Medulla Pyramid. The kidney has a functional unit. This is known as the Nephron. There are millions of nephrons are present in the Kidney. Whatever function is being executed by the kidney; the whole functions are executed by the Nephrons.