Difference between Cortical Nephrons and Juxtamedullary Nephrons

 Nephrons are the fundamental structural and functional units of the kidney. Each human kidney contains approximately one million nephrons, tirelessly working to filter blood, remove waste products, and maintain the body's fluid and electrolyte balance. Essentially, nephrons are the microscopic "factories" that produce urine.

Each nephron consists of two main parts:

I. Renal Corpuscle: This is where the initial filtration of blood occurs. It's composed of:

• Glomerulus: A cluster of tiny blood capillaries where blood is filtered.
• Bowman's Capsule (or Glomerular Capsule): A cup-shaped structure that surrounds the glomerulus and collects the filtered fluid (filtrate).

II. Renal Tubule: This long, convoluted tubule extends from the Bowman's capsule and further processes the filtrate. It's divided into several segments:

• Proximal Convoluted Tubule (PCT): Where most of the reabsorption of essential substances like water, glucose, amino acids, and ions occurs.
• Loop of Henle: A U-shaped tube that dips into the kidney's medulla. It plays a crucial role in establishing the concentration gradient necessary for producing concentrated urine. It has descending and ascending limbs with different permeabilities to water and solutes.
• Distal Convoluted Tubule (DCT): Involved in the fine-tuning of urine composition, with further reabsorption and secretion of ions to regulate electrolyte balance and pH.
• Collecting Duct: Receives filtrate from multiple nephrons and plays a final role in water reabsorption to concentrate the urine before it's transported out of the kidney.

Types of Nephrons:

Nephrons are categorized into two main types based on their location within the kidney and the length of their loop of Henle:

A. Cortical Nephrons:

• Location: Primarily located in the renal cortex, the outer region of the kidney.
• Abundance: They make up the majority (about 80-85%) of all nephrons.
• Loop of Henle: They have relatively short loops of Henle that extend only a short distance into the renal medulla.
• Function: Primarily involved in the reabsorption of essential nutrients and the regulation of electrolyte balance. They are important for maintaining overall body fluid balance.

B. Juxtamedullary Nephrons:

• Location: Their renal corpuscles are located near the junction of the renal cortex and renal medulla.
• Abundance: They constitute the remaining 15-20% of nephrons.
• Loop of Henle: They possess very long loops of Henle that extend deep into the renal medulla.
• Function: These nephrons are critical for producing concentrated urine. Their long loops of Henle, along with associated blood vessels (vasa recta), are essential for creating and maintaining the osmotic gradient in the medulla, which allows for significant water reabsorption and the formation of concentrated urine, thus conserving water in the body.

Cortical Nephrons vs Juxta Medullary Nephrons

Cortical Nephrons	Juxta Medullary Nephrons
They comprise 85%-86% of the nephrons in the kidney.	They comprise 14%-15% of the nephrons in the kidney
They have smaller size glomeruli located in the renal cortex.	They have larger size glomeruli located at the junction at the cortex and the medulla of the kidney.
They possess short loops of Henle which penetrate only as far as the outer layer of the renal medulla before turning back to the cortex; some of their loops are restricted to the cortex.	They possess long loops of Henle which penetrate deep into the medulla and sometimes reach the tip of the renal papillae before turning back towards the cortex.
The descending limb of loop of Henle contains a thin segment whereas ascending limb contains a thick segment.	Both the descending and ascending limbs of loop of Henle contain thin segments.
Its Henle loop manifest a vascular supply in the form of peritubular capillary plexus.	Its Henle loop manifest a vascular supply in the form of vasa recta.
Rate of filtration is slow.	Rate of filtration is fast.
These nephrons play a major role in excretion of waste products in dissolved form in the urine.	These nephrons are important in the counter current system by which the kidneys concentrate urine.