Nephrons

Nephrons
a. Nephron structure
(1) A nephron is the functional unit of the kidney.
(2) It consists of a renal corpuscle and a renal tubule.
(a) The corpuscle consists of a glomerulus and a glomerular capsule.
(b) Segments of the renal tubule include the proximal convoluted tubule, nephron loop (descending and ascending limbs), and distal convoluted tubule, which empties into a collecting duct.
(3) The collecting duct (technically not part of a nephron) empties into the minor calyx of the renal pelvis.

b. Blood supply of a nephron
(1) The glomerular capillary receives blood from the afferent arteriole and passes it to the efferent arteriole.
(2) The efferent arteriole gives rise to theperitubular capillary system, which
surrounds the renal tubule.
c. Juxtaglomerular apparatus
(1) The juxtaglomerular apparatus is at the point of contact between the last portion of the ascending limb of the nephron loop and the afferent and efferent arterioles.
(2) It consists of the macula densa and juxtaglomerular cells.

The Correct Answer and Explanation is :

Nephrons: Structure and Function

a. Nephron Structure
A nephron is the functional unit of the kidney responsible for filtering blood, reabsorbing water and nutrients, and excreting waste products as urine. It consists of two main parts: the renal corpuscle and the renal tubule.

1. Renal Corpuscle
   The renal corpuscle consists of the glomerulus, a network of capillaries where blood filtration occurs, and the glomerular capsule (also known as Bowman’s capsule), which encases the glomerulus and collects the filtered fluid.
2. Renal Tubule
   The renal tubule is divided into several segments:

• Proximal Convoluted Tubule (PCT): This is where the majority of reabsorption occurs, including nutrients like glucose, amino acids, and electrolytes.
• Nephron Loop (also called the loop of Henle): This consists of a descending limb (where water is reabsorbed) and an ascending limb (where sodium and chloride ions are reabsorbed).
• Distal Convoluted Tubule (DCT): This part fine-tunes the reabsorption process, particularly with respect to electrolytes and acid-base balance.
• The tubule then empties into a collecting duct, which is not technically part of the nephron but is involved in the final adjustments to urine composition.

1. Collecting Duct
   The collecting duct carries urine from multiple nephrons and empties into the minor calyx of the renal pelvis, where it eventually moves into the ureter for excretion.

b. Blood Supply of a Nephron
Blood enters the nephron through the afferent arteriole, which supplies the glomerulus. After filtration, the blood exits via the efferent arteriole and enters the peritubular capillary system, which surrounds the renal tubule and facilitates the exchange of gases, nutrients, and waste products.

c. Juxtaglomerular Apparatus
The juxtaglomerular apparatus (JGA) is located where the ascending limb of the nephron loop contacts the afferent and efferent arterioles. It plays a role in regulating blood pressure and filtration rate. It consists of:

• Macula Densa: Cells in the DCT that sense the concentration of sodium chloride and signal the afferent arteriole to adjust blood flow accordingly.
• Juxtaglomerular Cells: Specialized smooth muscle cells in the afferent arteriole that secrete renin, which helps regulate blood pressure and fluid balance.

I’ll generate an image to help visualize the structure of the nephron and its components.

Here is a detailed diagram of a nephron, showing all the key structures and their relationships, including the renal corpuscle, renal tubule segments, blood supply, and the juxtaglomerular apparatus. Let me know if you’d like further details or explanations!