human feces human feces human feces (or faeces in british english) is the solid or semisolid remains of food that could not be digested or absorbed in the small intestine of humans, but has been further broken 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. human feces photographed in a toilet, shortly after defecation. human feces has similarities to the feces of other animals and varies significantly in appearance (i.e. size, color, texture), according to the state of the diet, digestive system and general health. normally human feces is 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 is returned from the rectum to the large intestine, where water is further 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. characteristics classification main article: bristol stool scale 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 human feces ordinarily has a light to dark brown coloration, which results from a combination of bile, and bilirubin derivatives of stercobilin and urobilin, from dead red blood cells. normally it is semisolid, with a mucus coating. yellow yellowing of feces can be caused by an infection known as giardiasis, which derives its name from giardia, an anaerobic flagellated protozoan parasite that can cause severe and communicable yellow diarrhea. another cause of yellowing is a condition known as gilbert's syndrome. yellow stool can also indicate that food is passing through the digestive tract relatively quickly. yellow stool can be found in people with gastroesophageal reflux disease (gerd). pale or gray stool that is pale or grey may be caused by insufficient bile output due to conditions such as cholecystitis, gallstones, giardia parasitic infection, hepatitis, chronic pancreatitis, or cirrhosis. bile pigments from the liver give stool its brownish color. if there is decreased bile output, stool is much lighter in color. black or red feces can be black due to the presence of red blood cells that have been in the intestines long enough to be broken down by digestive enzymes. this is known as melena, and is typically due to bleeding in the upper digestive tract, such as from a bleeding peptic ulcer. conditions that can also cause blood in the stool include hemorrhoids, anal fissures, diverticulitis, colon cancer, and ulcerative colitis. the same color change can be observed after consuming foods that contain a substantial proportion of animal blood, such as black pudding or tiết canh. black feces can also be caused by a number of medications, such as bismuth subsalicylate (the active ingredient in pepto-bismol), and dietary iron supplements, or foods such as beetroot, black liquorice, or blueberries. hematochezia is similarly the passage of feces that is bright red due to the presence of undigested blood, either from lower in the digestive tract, or from a more active source in the upper digestive tract. alcoholism can also provoke abnormalities in the path of blood throughout the body, including the passing of red-black stool. hemorrhoids can also cause surface staining of red on stools, because as they leave the body the process can compress and burst hemorrhoids near the anus. blue prussian blue, or blue, a coloring used in the treatment of radiation, cesium, and thallium poisoning, can turn the feces blue. substantial consumption of products containing blue food dye, such as blue curaçao or grape soda, can have the same effect. silver a tarnished-silver or aluminum paint-like feces color characteristically results when biliary obstruction of any type (white stool) combines with gastrointestinal bleeding from any source (black stool). it can also suggest a carcinoma of the ampulla of vater, which will result in gastrointestinal bleeding and biliary obstruction, resulting in silver stool. green feces can be green due to having large amounts of unprocessed bile in the digestive tract and strong-smelling diarrhea. this can occasionally be the result from eating liquorice candy, as it is typically made with anise oil rather than liquorice herb and is predominantly sugar. excessive sugar consumption or a sensitivity to anise oil may cause loose, green stools. it can also result from consuming excessive amounts of blue or green dye. violet or purple violet or purple feces is a symptom of porphyria or more likely the consumption of beetroot. odor feces possesses physiological odor, which can vary according to diet and health status. for example, meat protein is rich in the 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 disulfide (dmds) dimethyl trisulfide (dmts) 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.