Feces (alsofaecesorfæces) are the solid or semi-solid remains of food that was not digested in thesmall intestine, and has been broken down bybacteria in thelarge intestine.[1][2] Feces contain a relatively small amount ofmetabolic waste products such as bacterially-alteredbilirubin and dead epithelial cells from the lining of the gut.[1]
The distinctiveodor of feces is due toskatole, andthiols (sulfur-containing compounds), as well as amines and carboxylic acids. Skatole is produced fromtryptophan via indoleacetic acid.Decarboxylation gives skatole.[3][4]
The perceived bad odor of feces has been hypothesized to be a deterrent for humans, as consuming or touching it may result in sickness or infection.[5]
Feces are discharged through theanus orcloaca duringdefecation. This process requires pressures that may reach 100 millimetres of mercury (3.9 inHg) (13.3 kPa) in humans and 450 millimetres of mercury (18 inHg) (60 kPa) in penguins.[6][7] The forces required to expel the feces are generated through muscular contractions and a build-up of gases inside the gut, prompting the sphincter to relieve the pressure and release the feces.[7]
Ecology
After an animal has digested eaten material, the remains of that material are discharged from its body as waste. Although it is lower in energy than the food from which it is derived, feces may retain a large amount of energy, often 50% of that of the original food.[8] This means that of all food eaten, a significant amount of energy remains for the decomposers of ecosystems.
Many organisms feed on feces, from bacteria to fungi to insects such asdung beetles, who cansense odors from long distances.[9] Some may specialize in feces, while others may eat other foods. Feces serve not only as a basic food, but also as a supplement to the usual diet of some animals. This process is known ascoprophagia, and occurs in various animal species such as young elephants eating the feces of their mothers to gain essentialgut flora, or by other animals such as dogs, rabbits, and monkeys.
Seeds also may be found in feces. Animals who eatfruit are known asfrugivores. An advantage for a plant in having fruit is that animals will eat the fruit and unknowingly disperse the seed in doing so. This mode ofseed dispersal is highly successful, as seeds dispersed around the base of a plant are unlikely to succeed and often are subject to heavypredation. Provided the seed can withstand the pathway through the digestive system, it is not only likely to be far away from the parent plant, but is even provided with its own fertilizer.
Organisms that subsist on dead organic matter ordetritus are known asdetritivores, and play an important role in ecosystems by recycling organic matter back into a simpler form that plants and otherautotrophs may absorb once again. This cycling of matter is known as thebiogeochemical cycle. To maintain nutrients in soil it is therefore important that feces returns to the area from which they came, which is not always the case in human society where food may be transported from rural areas to urban populations and then feces disposed of into a river or sea.
Depending on the individual and the circumstances, human beings may defecate several times a day, every day, or once every two or three days. Extensive hardening of the feces that interrupts this routine for several days or more is calledconstipation.
The appearance of human fecal matter varies according to diet and health.[11] Normally it is semisolid, with amucus coating. A combination ofbile andbilirubin, which comes from deadred blood cells, gives feces the typical brown color.[1][2]
After themeconium, the first stool expelled, a newborn's feces contains onlybile, which gives it a yellow-green color.Breast feeding babies expel soft, pale yellowish, and not quite malodorous matter; but once the baby begins to eat, and the body starts expelling bilirubin from dead red blood cells, its matter acquires the familiar brown color.[2]
At different times in their life, human beings will expel feces of different colors and textures. A stool that passes rapidly through the intestines will look greenish; lack of bilirubin will make the stool look like clay.
Acoprolite isfossilized feces and is classified as atrace fossil. Inpaleontology they give evidence about the diet of an animal. They were first described byWilliam Buckland in 1829. Prior to this, they were known as "fossilfir cones" and "bezoar stones". They serve a valuable purpose in paleontology because they provide direct evidence of the predation and diet of extinct organisms.[18] Coprolites may range in size from a few millimetres to more than 60 centimetres.
Palaeofeces are ancientfeces, often found as part ofarchaeological excavations or surveys. Intact paleofeces of ancient people may be found in caves in arid climates and in other locations with suitable preservation conditions. These are studied to determine thediet andhealth of the people who produced them through the analysis of seeds, small bones, and parasite eggs found inside. Feces may contain information about the person excreting the material as well as information about the material. They also may be analyzed chemically for more in-depth information on the individual who excreted them, usinglipid analysis and ancientDNA analysis. The success rate of usable DNA extraction is relatively high in paleofeces, making it more reliable than skeletal DNA retrieval.[19]
The reason this analysis is possible at all is due to the digestive system not being entirely efficient, in the sense that not everything that passes through the digestive system is destroyed. Not all of the surviving material is recognizable, but some of it is. Generally, this material is the best indicator archaeologists can use to determine ancient diets, as no other part of the archaeological record is so direct an indicator.[20]
A process that preserves feces in a way that they may be analyzed later is theMaillard reaction. This reaction creates a casing of sugar that preserves the feces from the elements. To extract and analyze the information contained within, researchers generally have to freeze the feces and grind it up into powder for analysis.[21]
In northernThailand,elephants are used to digest coffee beans in order to makeBlack Ivory coffee, which is among the world's most expensive coffees.Paper is also made from elephant dung in Thailand.[25]Haathi Chaap is a brand of paper made from elephant dung.
Dog feces was used in thetanning process ofleather during theVictorian era. Collected dog feces, known as "pure", "puer", or "pewer",[26] were mixed with water to form a substance known as "bate", becauseproteolyticenzymes in the dog feces helped to relax the fibrous structure of the hide before the final stages of tanning.[27] Dog feces collectors were known aspure finders.[28]
Elephants,hippos,koalas and pandas are born with sterile intestines, and require bacteria obtained from eating the feces of their mothers to digest vegetation.
Feces is the scientific terminology, while the termstool is also commonly used in medical contexts.[30] Outside of scientific contexts, these terms are less common, with the most common layman's term beingpoop orpoo. The termshit is also in common use, although it is widely considered vulgar or offensive. There are many other terms, see below.
Stool is a common term in reference tohuman feces. For example, inmedicine, to diagnose the presence or absence of a medical condition, astool sample sometimes is requested for testing purposes.[33]
The termbowel movement(s) (with each movement a defecation event) is also common inhealth care.
Feces when used asfertilizer (usually mixed with animal bedding and urine) –manure
Horses – horse manure, roadapple (before motor vehicles became common, horse droppings were a big part of the rubbish communities needed to clean off roads)
In all human cultures, feces elicit varying degrees ofdisgust in adults. Children under two years typically have no disgust response to it, suggesting it is culturally derived.[34] Disgust toward feces appears to be strongest in cultures whereflush toilets make olfactory contact with human feces minimal.[35][36] Disgust is experienced primarily in relation to the sense of taste (either perceived or imagined) and, secondarily to anything that causes a similar feeling by sense of smell, touch, or vision.
^Langley, Leroy Lester; Cheraskin, Emmanuel (1958).The Physiology of Man. McGraw-Hill.Archived from the original on 1 August 2020. Retrieved3 December 2019.
^Johnson, Steven (2006).The ghost map: the story of London's most terrifying epidemic--and how it changed science, cities, and the modern world. New York: Riverhead Books.ISBN1-59448-925-4.OCLC70483471.
