The Loop of Henle is concerned with which of the following systems?

What is hilum?

In humans,the primary excretory system consists of:
$I.$ Pair of kidneys
$II.$ One pair of ureters
$III.$ Urinary bladder
$IV.$ Urethra
$V.$ Skin
$VI.$ Lungs
$VII.$ Liver

Select the correct statements from the following.
$(i)$ Renal papilla is a narrow tip of the medullary pyramid.
(ii) Renal cortex is red-coloured and striated.
(iii) Longitudinal-circular-longitudinal arrangement of smooth muscles is observed in the renal pelvis at its origin.
(iv) Ureter is a long,non-muscular hollow tube that communicates with the renal pelvis at its origin.

Which of the following is not a part of a kidney?

Columns of Bertini in the kidney of mammals are formed as the extension of