Nephrons

The juxta medullary nephron is a type of nephron located in the kidney, crucial for urine concentration. Consider the provided options about juxta medullary nephrons:

Therefore, the correct statement regarding juxta medullary nephrons is: Loop of Henle of juxta medullary nephron runs deep into medulla.

To determine the correctness of the statements, let's analyze each one:

Statement I: "In the nephron, the descending limb of loop of Henle is impermeable to water and permeable to electrolytes."

The descending limb of the loop of Henle is actually permeable to water and relatively impermeable to electrolytes. This allows water to move out of the tubule, concentrating the filtrate.

Statement II: "The proximal convoluted tubule is lined by simple columnar brush border epithelium and increases the surface area for reabsorption."

The proximal convoluted tubule is lined by simple cuboidal epithelium with a brush border, not columnar. The brush border increases the surface area for reabsorption of substances back into the blood.

Both Statement I and Statement II contain inaccuracies:

Therefore, the correct answer is: Both statement I and Statement II are false.

The proximal tubule (P) is primarily responsible for reabsorbing a large portion of the filtrate, including water, sodium chloride, bicarbonate, and other nutrients. It also secretes hydrogen ions (H+) for acid-base balance. The distal tubule (D) is involved in the fine-tuning of ion exchange and pH balance. It reabsorbs sodium and bicarbonate, and secretes potassium (K+) and hydrogen ions. Looking at the diagrams, option (3) accurately reflects the processes occurring in both the proximal and distal tubules of the nephron. Thus, the correct diagram is option (3).