Final answer:
The two parts of the renal tubules that extend into the medulla of the kidney are the loop of Henle and the collecting ducts. The loop of Henle dips into the medulla as part of the nephron, while the collecting ducts gather filtered content from various nephrons and direct it towards the renal papillae.
Step-by-step explanation:
The two parts of the renal tubules that extend into the medulla of the kidney are the loop of Henle and the collecting ducts. The loop of Henle, also known as a nephritic loop, is a U-shaped tube that dips into the renal medulla.
It is a part of the renal tubule that starts from the proximal convoluted tubule (PCT) within the renal cortex and includes descending and ascending limbs that navigate through the medulla. The collecting ducts amass the filtered contents from multiple nephrons and funnel them into the renal papillae of the medulla.
It's important to note that in the kidney, there are nephrons called juxtamedullary nephrons which have loops of Henle that extend deeply into the renal medulla. These nephrons help to concentrate the urine.