Which of the following organs is not present in a pair in the human body?

Choose the correct statement given below regarding juxta medullary nephron.

Kidneys are reddish-brown,bean-shaped structures situated between the levels of . . . . . . thoracic and . . . . . . lumbar vertebrae.

Analogy type question:
$(1)$ Inner concave notch of kidney : Hilum :: Broad funnel-shaped part of renal pelvis : ............. .
$(2)$ Renal tubule begins with a double-walled cup-like structure called Bowman's capsule :: Bowman's capsule along with glomerulus : ............. .

Choose the correct option:
$(1)$ $ANF$ is secreted when blood pressure decreases / blood pressure increases.
$(2)$ Renal pyramids are located in the renal cortex / renal medulla.

Cortical nephrons are ...... in number compared to juxtamedullary nephrons.