Question

Sol. [Key Concept: Juxtamedullary nephrons]

Juxtamedullary nephrons have long loops of Henle that descend deep into the medulla, so option (1) is correct. Their renal corpuscles lie in the deep cortex near the corticomedullary boundary, and they are fewer than cortical nephrons. The long loops and associated vasa recta help maintain the medullary gradient needed to concentrate urine.