The organs concerned with the formation, storage and elimination of urine constitute urinary system.

The process of removal of these wastes (mainly nitrogenous wastes) from the body is known as excretion.

Trimethylamine oxide ; Excreted by some marine teleosts

Bile pigments ; The yare excreted by the liver in bile juice and is eliminated along with faeces

Creatine and creatinine ; It is an important energy compound in muscles.

Excess water and minerals ; These are lost in a controlled manner by a specialized excretory or osmoregulatory organ

Ammonia ; Highly toxic, soluble, readily diffusable, excreted in dilute form by freshwater animals and marine inverebrates. Such animals are said to be ammoniotelic.

Urea ; Urea is less toxic than ammonia but needs to be diluted to be excreted. Excreted by terrestrial animals said to be ureotelic

Uric acid ; It is nontoxic. It requires less water for excretion sice it is insoluble. Excreted by birds and insects sid to be urecotelic.

Kidneys are the chief excretory organs of vertebrates. Their roles are :

They remove wastes that are formed during cellular metabolism, as well as toxic substances and excess non-toxic substances from the body

They control the volume of blood and interstitial fluids by controlled ion excretion.

The excretory system of humans consists of two kidneys, two ureters, a urinary bladder, and a urethra

A nephron consists of a renal corpuscle and a long complicated renal tubule

Arising from the bowman's capsule, traverses within the cortex.

The loop of Henle begins as a direct continuation of the pars rectait consists of a thick ascending limb, a loop and a thick descending limb.

The distal convoluted tubule has a straight part in cintinuation of ascending limb of the loop of henle and a convoluted part lying in the cortex.

Juxta medullary nephrons ; In this type, the Loop of Henle is vvery long and extends deep into the medulla

Cortical nephron ; In cortical nephrons, the loop of Henle extends very little into the medulla

Micturition is the voiding of urine according to the will of the person in suitable time and space.