The kidneys in human beings are a part of the system for

The volume of glomerular filtrate produced is $180 \, L$ per day,but the volume of urine excreted is just $1-2 \, L$. Give a suitable reason for this statement.

$(a)$ Draw the structure of a nephron and label the following parts on it:
$(i)$ Renal artery
$(ii)$ Bowman's capsule
$(iii)$ Glomerulus
$(iv)$ Collecting duct
$(b)$ Name four substances in the initial filtrate which are selectively reabsorbed as the filtrate flows along the tubule.

Just as $CO_{2}$ is removed from the blood in the lungs,nitrogenous wastes such as urea or uric acid are removed from blood in the liver.

How is the amount of urine produced regulated?

$(a)$ Draw a diagram of the human excretory system and label the following: Aorta,Vena cava,Urinary bladder,Urethra.
$(b)$ List two vital functions of the kidney.