Choose the correct statement given below regarding juxta medullary nephron.

To understand the characteristics of juxtamedullary nephrons, let us analyze the structural differences between the two main types of nephrons found in the human kidney: cortical nephrons and juxtamedullary nephrons.

Nephrons are categorized based on their location in the renal cortex and the length of their loop of Henle:
1. Cortical Nephrons: These make up the majority (about 85%) of nephrons. Their renal corpuscles lie in the outer cortex, and they have relatively short loops of Henle that extend only a short distance into the outer medulla.
2. Juxtamedullary Nephrons: These make up about 15% of nephrons. Their renal corpuscles lie close to the corticomedullary junction (the border between the cortex and medulla), and they have long loops of Henle that extend deep into the renal medulla. This long loop of Henle is essential for establishing the concentration gradient in the renal medulla, which allows for the concentration of urine.

Let us evaluate each of the given options based on these facts:
- "Juxta medullary nephrons are located in the columns of Bertini.": This is incorrect. The renal corpuscles and convoluted tubules of cortical and juxtamedullary nephrons reside in the renal cortex, not primarily within the renal columns (columns of Bertini), which are extensions of the cortex between the renal pyramids.
- "Renal corpuscle of juxta medullary nephron lies in the outer portion of the renal medulla.": This is incorrect. Renal corpuscles are never located in the renal medulla; they are located in the renal cortex (specifically, close to the junction with the medulla for juxtamedullary nephrons).
- "Loop of Henle of juxta medullary nephron runs deep into medulla.": This is correct. The defining feature of juxtamedullary nephrons is their long loop of Henle that penetrates deep into the inner zone of the renal medulla.
- "Juxta medullary nephrons outnumber the cortical nephrons.": This is incorrect. Cortical nephrons are much more numerous (approx. 85%) compared to juxtamedullary nephrons (approx. 15%).

Therefore, the only correct statement is that the loop of Henle of juxtamedullary nephrons runs deep into the medulla.