Navigation Links

Excretion is the biological process by which an organism separates waste products from its body. The waste products are then usually expelled from the body by elimination.

In mammals, for example, the two major excretory processes are the formation of urine in the kidneys and the formation of feces in the intestines. The waste products are eliminated by urination and defecation respectively.

While urine and feces are both waste material of body processes, they are in completely different categories. Urine is a waste product of the urinary system process while feces are waste products of the digestive system. Feces may contain about one-third bacteria, most of which are harmless, even beneficial while in the gut, but dangerous to others and they may also contain virulent and even deadly pathogens in the form of bacteria, viruses, amoebae, and various parasitic worms. Urine, on the other hand, contains excess water, salt, and protein waste in the form of urea as uric acid, and seldom any pathogens; should a person be in a situation of insufficient water and in danger of overheating due to lack of persperation, urine may be safely used to dampen clothing to aid cooling. It is futile to attempt to drink it (or salty ocean water), as it requires more water from the body to excrete the salt than is available in the fluid. Some sea birds are able to efficently excrete excess salt through the tear ducts associated with the eyes. Such birds can drink sea water without harm.

In insects, a system involving Malpighian tubules is utilized to excrete metabolic waste. Metabolic waste diffuses or is actively transported into the tubule, which transports the wastes to the intestines. The metabolic waste is then released from the body along with fecal stuffs.

See also


(Date:11/4/2015)... 2015 --> ... by Transparency Market Research "Home Security Solutions Market - Global ... - 2022", the global home security solutions market is expected to ... The market is estimated to expand at a CAGR ... 2022. Rising security needs among customers at homes, the ...
(Date:10/29/2015)... , Oct. 29, 2015  Rubicon Genomics, ... for U.S. distribution of its DNA library preparation ... and Rubicon,s new ThruPLEX Plasma-seq kit. ThruPLEX Plasma-seq ... the preparation of NGS libraries for liquid biopsies--the ... diagnostic and prognostic applications in cancer and other ...
(Date:10/27/2015)... 27, 2015 Munich, Germany ... Mapping technology (ASGM) automatically maps data from mobile eye ... , so that they can be quantitatively analyzed ... Munich, Germany , October 28-29, 2015. SMI,s ... from mobile eye tracking videos created with SMI,s ...
Breaking Biology News(10 mins):
Other biology definition