The correct option is 2 and 3 only.
Explanation
The renal blood supply involves a specific arrangement where the efferent arteriole, emerging from the glomerulus, forms a secondary capillary network around the renal tubules. The structure and presence of these vessels vary between the two types of nephrons: cortical and juxtamedullary.
Statement-wise Analysis:
- Statement 1 is Incorrect. The vasa recta are minute vessels that run parallel to the Loop of Henle, forming a 'U' shape. They do not run perpendicular. This parallel arrangement is critical for the counter-current mechanism which concentrates urine.
- Statement 2 is Correct. Cortical nephrons, which make up the majority of nephrons, have a short Loop of Henle that extends only very little into the medulla. In these nephrons, the vasa recta are either absent or highly reduced. Well-developed vasa recta are a characteristic feature of juxtamedullary nephrons.
- Statement 3 is Correct. The efferent arteriole emerging from the glomerulus divides to form a fine capillary network around the renal tubule known as the peritubular capillaries. The vasa recta is a specialized portion of this network associated with the Loop of Henle.
Key Takeaway:
Peritubular capillaries arise from the efferent arteriole. The vasa recta runs parallel to the Loop of Henle and is distinctively well-developed in juxtamedullary nephrons while being reduced or absent in cortical nephrons.