Nephron- Function Renal Tubules 

Nephrons are considered to be the structural and functional unit of the kidney since they filter the blood in the kidney. Therefore, nephrons are responsible for the removal of the waste and unwanted fluid from your body.

A typical nephron consists of a glomerulus, a small network of blood vessels, and Bowman’s capsule, a closed sac. In addition, tubes that carry urine from the kidney to the bladder are known as ureters.

Structure of the nephron:

A nephron is a fundamental unit of the kidney which has multiple functions and a detailed structure. Even though the nephron consists of various parts, the main bifurcation of the nephron is done in two parts: renal tubules and renal corpuscles. These two parts of the nephron are further divided into smaller units.

1. Renal Corpuscles:
   
   The filtration of the blood plasma begins from the renal corpuscles. This filtration process requires is mainly carried out by two components namely the glomerulus and the Bowman’s capsule. Let us have a look at the functions of these two components in detail.
    
   • Glomerulus-
     
     The glomerulus of the nephron is mainly responsible for the filtration of the blood. It is a cluster of small and numerous blood vessels. It has a thin wall that allows tiny molecules, waste products, and unwanted fluids to pass into the tubule. So, the blood is entirely filtered in this part of the nephron, thereby producing the glomerular filtrate. The Glomerular filtrate is also called primary urine.
   
   
   • Bowman’s Capsule-
     
     Bowman’s capsule is a cup-like structure and encloses the glomerulus. It has a space enclosed in it called the Bowman space. From here, the glomerulus filtrate is passed on to the other parts of the nephron i.e. into the renal tubule to eject it out of the body. Before the glomerulus filtrate enters the Bowman’s capsule, it must pass through multiple layers.
2. Renal Tubules:
   
   The renal tubule is a long pipe-like structure that collects the filtrate generated by the glomerulus and passed on by the Bowman’s capsule. These tiny tubes can reabsorb the required nutrients, fluids, and other components from the glomerular filtrate back into the blood. The remaining materials and liquids that are left in these tubes become the secondary urine and are passed on to the collecting duct system.
   The renal tubule can be divided into three divisions based on each of their workings. The three subparts in it are mentioned below:
    
   • Proximal Convoluted Tubule-
     
     The proximal convoluted tubule (PCT) is the first part of the renal tubule and is located just near the glomerulus at the urinary pole. This is where the maximum amount of the glomerulus filtrate essential for the body is reabsorbed.
     
     Essential substances like proteins, fats, glucose, and needed fluids are reabsorbed from the glomerular filtrate. The reabsorption of essential substances from the glomerular filtrate is an active process and requires energy.
   
   
   • Loop of Henle-
     
     The loop of Henle is located at the bottom of the medulla and has a pin-shaped structure. This loop has ascending and descending limbs. The ascending limb is permeable to electrolytes and impermeable to water, whereas the descending limb is permeable to water but impermeable to the electrolyte.
     
     Reabsorption of nutrients is not prominent in this part of the renal tubule because most of it has already been absorbed in the PCT.
     
     Here, the remaining filtrate is then passed on to the distal convoluted tubule.
   
   
   • Distal convoluted tubule-
     
     The distal convoluted tubule is shorter compared to the proximal convoluted tubule. In the DCT of the nephron, the final reabsorption and secretion of ions and other materials take place.
     
     The DCT helps in maintaining the levels of sodium and potassium in the blood. The DCT delivers the filtrate left behind to get excreted from the body into the collecting duct.
     
     Lastly, there is a collecting duct that collects the entire filtrate. This filtrate contains unwanted and unnecessary fluids and components to be excreted from the body. This is a connecting duct that connects the nephron to the renal pelvis. Here, to make sure the urine produced is concentrated, reabsorption of water takes place.

The Bottom Line

The system, structure, and function of the nephron, along with all its divisions and sections, can be complicated to understand. Here, a very simple overview of the entire topic has been given, although there are more complex functions and procedures of all the components. Every section has its importance and uniqueness that makes up the entire system.