Human feces (or faeces in British English; Latin: fæx) are the solid or semisolid remains of the food that could not be digested or absorbed in the small intestine, but has been rotted down by bacteria in the large intestine. It also contains bacteria and a relatively small amount of metabolic waste products such as bacterially altered bilirubin, and the dead epithelial cells from the lining of the gut. It is discharged through the anus during a process called defecation. Urine and feces together are called excreta. They vary significantly in appearance (i.e. size, color, texture), according to the state of the diet, digestive system and general health. Normally human feces are semisolid, with a mucus coating. Small pieces of harder, less moist feces can sometimes be seen impacted in the distal (final or lower) end. This is a normal occurrence when a prior bowel movement is incomplete, and feces are returned from the rectum to the large intestine, where water is absorbed.
In the medical literature, the term "stool" is more commonly used than "feces".
Human feces together with human urine are collectively referred to as human waste or human excreta. Containing human feces, and preventing spreading of pathogens from human feces via the fecal-oral route, are the main goals of sanitation.
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Characteristics
Classification
The Bristol stool scale is a medical aid designed to classify the form of human feces into seven categories. Sometimes referred to in the UK as the Meyers Scale, it was developed by K. W. Heaton at the University of Bristol and was first published in the Scandinavian Journal of Gastroenterology in 1997. The form of the stool depends on the time it spends in the colon.
The seven types of stool are:
- Separate hard lumps, like nuts (hard to pass)
- Sausage-shaped but lumpy
- Like a sausage but with cracks on the surface
- Like a sausage or snake, smooth and soft
- Soft blobs with clear-cut edges
- Fluffy pieces with ragged edges, a mushy stool
- Watery, no solid pieces. Entirely Liquid
Types 1 and 2 indicate constipation. Types 3 and 4 are optimal, especially the latter, as these are the easiest to pass. Types 5-7 are associated with increasing tendency to diarrhea or urgency.
Meconium is a newborn baby's first feces.
Color
Human fecal matter varies significantly in appearance, depending on diet and health.
Brown
Yellow
Pale or gray
Black or red
Blue
Silver
Green
Violet or purple
Odor
Feces possess physiological odor, which can vary according to diet and health status. For example, meat protein contains a lot of the sulfur-containing amino acid methionine, which is a precursor of the sulfur-containing odorous compounds listed below. The odor of human feces is suggested to be made up from the following odorant volatiles:
- Methyl sulfides
- methylmercaptan/methanethiol (MM)
- dimethyl sulfide (DMS)
- dimethyl trisulfide (DMTS)
- dimethyl disulfide (DMDS)
- Benzopyrrole volatiles
- indole
- skatole
- Hydrogen sulfide (H2S)
(H2S) is the most common volatile sulfur compound in feces. The odor of feces may be increased when various pathologies are present, including:
- Celiac disease
- Crohn's disease
- Ulcerative colitis
- Chronic pancreatitis
- Cystic fibrosis
- Intestinal infection, e.g. Clostridium difficile infection.
- Malabsorption
- Short bowel syndrome
Attempts to reduce the odor of feces (and flatus) are largely based on animal research carried out with industrial applications, such as reduced environmental impact of pig farming. See also: Flatulence#Management, odor. Many dietary modifications/supplements have been researched, including:
- Activated charcoal (In this study it was found that activated charcoal at a dose of 0.52g four times a day did not appreciably influence the liberation of fecal gases.)
- Bismuth subsalicylate
- Chloryphyllyn
- Herbs such as rosemary
- Yucca schidigera
- Zinc acetate
Average chemical characteristics
On average humans eliminate 128 g of fresh feces per person per day with a pH value of around 6.6. Fresh feces contains around 75% water and the remaining solid fraction is 84-93% organic solids.
These organic solids consist of: 25-54% bacterial biomass, 2-25% protein or nitrogenous matter, 25% carbohydrate or undigested plant matter and 2-15% fat. Protein and fat come from the colon due to secretion, epithelial shedding and gut bacterial action. These proportions vary considerably depending on many factors such as mainly diet and body weight.
The remaining solids are composed of calcium and iron phosphates, intestinal secretions, small amounts of dried epithelial cells, and mucus.
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Abnormalities
Stool analysis (stool sample)
Clinical laboratory examination of feces, usually termed as stool examination or stool test, is conducted for the sake of diagnosis, for example, to detect the presence of parasites such as pinworms and their eggs (ova) or, to detect disease spreading bacteria. A stool culture--the controlled growth of microbial organisms in culture media under laboratory conditions--sometimes is performed to identify specific pathogens in stool. The stool guaiac test (or guaiac fecal occult blood test) is conducted to detect the presence of blood in stool that is not apparent to the unaided eye.
The main pathogens that are commonly looked for in feces include:
- Bacteroides species
- Salmonella and Shigella
- Yersinia tends to be incubated at 30 °C (86 °F), which is cooler than usual
- Campylobacter incubated at 42 °C (108 °F), in a special environment
- Aeromonas
- Candida if the person is immunosuppressed (e.g., undergoing cancer treatment)
- E. coli O157 if blood is visible in the stool sample
- Cryptosporidium
- Entamoeba histolytica
Intestinal parasites and their ova (eggs) can sometimes be visible to the naked eye.
Undigested food remnants
Sometimes food may make an appearance in the feces. Common undigested foods found in human feces are seeds, nuts, corn, and beans, mainly because of their high dietary fiber content. Beets may turn feces different hues of red. Artificial food coloring in some processed foods, such as highly colorful packaged breakfast cereals, can cause unusual coloring of feces if eaten in sufficient quantities.
Undigested objects such as seeds can pass through the human digestive system, and later germinate. One result of this is tomato plants growing where sewage sludge has been used as fertilizer.
Diarrhea
Diarrhea (or diarrhoea in British English) is the condition of having three or more loose or liquid bowel movements per day. This condition can be a symptom of injury, disease or foodborne illness and is usually accompanied by abdominal pain. There are other conditions which involve some but not all of the symptoms of diarrhea, and so the formal medical definition of diarrhea involves defecation of more than 200 grams per day (though formal weighing of stools to determine a diagnosis is never actually carried out).
It occurs when insufficient fluid is absorbed by the colon. As part of the digestion process, or due to fluid intake, food is mixed with large amounts of water. Thus, digested food is essentially liquid prior to reaching the colon. The colon absorbs water, leaving the remaining material as a semisolid stool. If the colon is damaged or inflamed, however, absorption is inhibited, and watery stools result.
Diarrhea is most commonly caused by a myriad of viral infections but is also often the result of bacterial toxins and sometimes even infection. In sanitary living conditions and with ample food and water available, an otherwise healthy patient typically recovers from the common viral infections in a few days and at most a week. However, for ill or malnourished individuals diarrhea can lead to severe dehydration and can become life-threatening without treatment.
Constipation
Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation. Severe constipation includes obstipation (failure to pass stools or gas) and fecal impaction, which can progress to bowel obstruction and become life-threatening.
Others
Bile overload is very rare, and not a health threat. Problems as simple as serious diarrhea may cause blood in one's stool. Black stools caused by the presence of blood usually indicate a problem in the intestines (the black color is a sign of digested blood), whereas red streaks of blood in stool usually are caused by bleeding in the rectum or anus.
Fecal markers
The feces can be analyzed for various markers that are indicative of various diseases and conditions. For example, fecal calprotectin levels indicate an inflammatory process such as Crohn's disease, ulcerative colitis and neoplasms (cancer).
Also, feces may be analyzed for any fecal occult blood, which is indicative of a gastrointestinal bleeding.
Fecal contamination
A quick test for fecal contamination of water sources or soil is a check for the presence of E. coli bacteria performed with the help of MacConkey agar plates or Petri dishes. E. coli bacteria uniquely develop red colonies at temperature of approximately 43 °C (109 °F) overnight. Although most strains of E. coli are harmless, their presence is indicative of fecal contamination, and hence an increased possibility of the presence of more dangerous organisms.
Fecal contamination of water sources is highly prevalent worldwide, accounting for the majority of unsafe drinking water. In developing countries most sewage is discharged without treatment. Even in developed countries events of sanitary sewer overflow are not uncommon and regularly pollute the Seine River (France) and the River Thames (England), for example.
Uses
Use as fertilizer
Human feces have historically been used as fertilizer for centuries in the form of night soil, fecal sludge, and sewage sludge. The use of untreated human feces in agriculture poses significant health risks and has contributed to widespread infection with parasitic worms--a disease called helminthiasis, affecting over 1.5 billion people in developing countries.
There are methods available to safely reuse human feces in agriculture as per the "multiple barrier concept" described by the World Health Organization in 2006. The approach to "close the loop" between human excreta (sanitation) and agriculture is also called ecological sanitation. It may involve certain types of dry toilets such as urine-diversion dry toilets or composting toilets.
Fecal transplants
In humans, fecal transplants (or stool transplant) is the process of transplantation of fecal bacteria from a healthy individual into a recipient who is suffering from a certain disease, such as irritable bowel syndrome. The resulting inoculation of healthy gut flora can sometimes improve the physiology of the recipient gut.
Fecal bacteriotherapy--also known as a fecal transplant--is a medical procedure wherein fecal bacteria are transplanted from a healthy individual into a patient. Recent research indicates that this may be a valuable method to re-establish normal gut cultures that have been destroyed through the use of antibiotics or some other medical treatments.
Biogas production
The biogas produced from feces when it is contained in sewage and treated in an anaerobic digestion process could be worth as much as 9.5 billion dollars.
Washington DC plans to produce biogas from sewage sludge, the by-product of sewage treatment, which will save 13 million dollars a year.
Paleofeces
Paleofeces, also known as coprolites, are ancient human feces, often found as part of archaeological excavations or surveys. Intact feces of ancient people may be found in caves in arid climates and in other locations with suitable preservation conditions. These are studied to determine the diet and health of the people who produced them through the analysis of seeds, small bones, and parasite eggs found inside. They also may be analyzed chemically for more in-depth information on the individual who excreted them, using lipid analysis and DNA analysis. The success rate of usable DNA extraction is relatively high in paleofeces, making it more reliable than skeletal DNA retrieval.
Society and culture
Disgust and shame
In all human cultures, feces elicit varying degrees of disgust. 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. As such, human feces is regarded as something to be avoided diligently: expelled in private and disposed of immediately and without a trace. It often is considered an unacceptable topic in polite conversation and its mere mention may cause offence in certain contexts.
The disposal of feces always has been associated with the lowest people among a society, the social outcasts, the pariahs, and the social discards. The caste system in India was created along the lines of profession and the dalits (untouchables) were left to do work related to human emissions. They did such work as cleaning and picking feces from streets, cleaning toilets, and working with dead bodies. Such practices are prevalent even today in the rural and small villages of India; where it is called "manual scavenging".
An example of repulsion by feces from the ancient world is found in the writings called Deuteronomy used by Jews and Christians:
Designate a place outside the camp where you can go to relieve yourself. As part of your equipment have something to dig with, and when you relieve yourself, dig a hole and cover up your excrement. For the LORD your God moves about in your camp to protect you and to deliver your enemies to you. Your camp must be holy, so that he will not see among you anything indecent and turn away from you.
Anal cleansing
People from different cultures employ a variety of personal cleansing practices after defecation. The anus and buttocks may be either washed with liquids or wiped with toilet paper or other solid materials. In many Muslim, Hindu and Sikh cultures, as well as Southeast Asia and Southern Europe, water is usually used for anal cleansing using a jet, as with a bidet, or most commonly, splashed and washed with the hand. In other cultures (such as many Western countries), cleaning after defecation is generally done with toilet paper only.
Terminology and other terms used
There are many synonyms in informal registers for human feces. Many are euphemismistic, colloquial, or both; some are profane (such as shit), whereas most belong chiefly to child-directed speech (such as poo or poop) or to crude humor (such as turd).
Source of the article : Wikipedia
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