105-456: Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma . In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream . Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to
210-407: A bolus before being transported down the esophagus through peristalsis . The sublingual region underneath the front of the tongue is a location where the oral mucosa is very thin, and underlain by a plexus of veins. This is an ideal location for introducing certain medications to the body. The sublingual route takes advantage of the highly vascular quality of the oral cavity, and allows for
315-424: A blood and nerve supply which enables proprioception. This is the ability of sensation when chewing, for example if we were to bite into something too hard for our teeth, such as a chipped plate mixed in food, our teeth send a message to our brain and we realise that it cannot be chewed, so we stop trying. The shapes, sizes and numbers of types of animals' teeth are related to their diets. For example, herbivores have
420-412: A build-up of gases inside the gut, prompting the sphincter to relieve the pressure and release the feces. 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. This means that of all food eaten,
525-410: A complex digestive system as do, for example, ruminants. Instead they extract more nutrition from grass by giving their food a second pass through the gut . Soft faecal pellets of partially digested food are excreted and generally consumed immediately. They also produce normal droppings, which are not eaten. Young elephants, pandas, koalas, and hippos eat the faeces of their mother, probably to obtain
630-506: A contiguous channel traversing the inner and outer membranes of the bacteria. It is a simple system, which consists of only three protein subunits: the ABC protein , membrane fusion protein (MFP), and outer membrane protein . This secretion system transports various chemical species, from ions, drugs, to proteins of various sizes (20–900 kDa). The chemical species secreted vary in size from the small Escherichia coli peptide colicin V, (10 kDa) to
735-428: A crop or enlarged esophagus . Herbivores have evolved cecums (or an abomasum in the case of ruminants ). Ruminants have a fore-stomach with four chambers. These are the rumen , reticulum , omasum , and abomasum. In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud (or bolus ). The cud
840-433: A deterrent for humans, as consuming or touching it may result in sickness or infection. Feces are discharged through the anus or cloaca during defecation . 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. The forces required to expel the feces are generated through muscular contractions and
945-743: A diverse range of species from annelids to elephants, chimpanzees and many birds. About 182 fish consume seeds or fruit. Animals (domesticated and wild) use as many types of grasses that have adapted to different locations as their main source of nutrients. Humans eat thousands of plant species; there may be as many as 75,000 edible species of angiosperms , of which perhaps 7,000 are often eaten. Plants can be processed into breads, pasta, cereals, juices and jams or raw ingredients such as sugar, herbs, spices and oils can be extracted. Oilseeds are pressed to produce rich oils – sunflower , flaxseed , rapeseed (including canola oil ) and sesame . Many plants and animals have coevolved in such
1050-407: A general response to stress conditions, the process of loading cargo proteins seems to be selective. The gastrovascular cavity functions as a stomach in both digestion and the distribution of nutrients to all parts of the body. Extracellular digestion takes place within this central cavity, which is lined with the gastrodermis, the internal layer of epithelium . This cavity has only one opening to
1155-411: A hand to grab pieces of dead grass, leaves, and weeds, with bits of soil to help chew. The lips break the food down into smaller pieces. In the pharynx, the food is lubricated by mucus secretions for easier passage. The esophagus adds calcium carbonate to neutralize the acids formed by food matter decay. Temporary storage occurs in the crop where food and calcium carbonate are mixed. The powerful muscles of
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#17327880567031260-583: A high protein, fibre, vitamin E and B content. Seeds are a good source of food for animals because they are abundant and contain fibre and healthful fats, such as omega-3 fats . Complicated chemical interactions can enhance or depress bioavailability of certain nutrients. Phytates can prevent the release of some sugars and vitamins. Animals that only eat plants are called herbivores , with those that mostly just eat fruits known as frugivores , leaves, while shoot eaters are folivores (pandas) and wood eaters termed xylophages (termites). Frugivores include
1365-678: A million. Herbivores generally have more than carnivores as they need to tell which plants may be poisonous. Not all mammals share the same tastes: some rodents can taste starch , cats cannot taste sweetness, and several carnivores (including hyenas , dolphins, and sea lions) have lost the ability to sense up to four of the five taste modalities found in humans. Food is broken into nutrient components through digestive process. Proper digestion consists of mechanical processes ( chewing , peristalsis ) and chemical processes ( digestive enzymes and microorganisms ). The digestive systems of herbivores and carnivores are very different as plant matter
1470-482: A number of molars which are used to grind plant matter, which is difficult to digest. Carnivores have canine teeth which are used to kill and tear meat. A crop , or croup, is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion. In some birds it is an expanded, muscular pouch near the gullet or throat. In adult doves and pigeons, the crop can produce crop milk to feed newly hatched birds. Certain insects may have
1575-409: A plant in having fruit is that animals will eat the fruit and unknowingly disperse the seed in doing so. This mode of seed dispersal is highly successful, as seeds dispersed around the base of a plant are unlikely to succeed and often are subject to heavy predation . 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
1680-477: A significant amount of energy remains for the decomposers of ecosystems. Many organisms feed on feces, from bacteria to fungi to insects such as dung beetles , who can sense odors from long distances. 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 as coprophagia , and occurs in various animal species such as young elephants eating
1785-589: A site for fermentation of indigestible matter by gut bacteria and for resorption of water from digests before excretion. In mammals , preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach . Mechanical and chemical digestion begin in the mouth where food is chewed , and mixed with saliva to begin enzymatic processing of starches . The stomach continues to break food down mechanically and chemically through churning and mixing with both acids and enzymes. Absorption occurs in
1890-546: A source of food for protozoa, who in turn provide a source of food for other organisms such as small invertebrates. Other organisms that feed on bacteria include nematodes, fan worms, shellfish and a species of snail. In the marine environment, plankton (which includes bacteria , archaea , algae , protozoa and microscopic fungi ) provide a crucial source of food to many small and large aquatic organisms. Without bacteria, life would scarcely exist because bacteria convert atmospheric nitrogen into nutritious ammonia . Ammonia
1995-556: A specific ecological niche within specific geographical contexts. Omnivorous humans are highly adaptable and have adapted to obtain food in many different ecosystems. Humans generally use cooking to prepare food for consumption. The majority of the food energy required is supplied by the industrial food industry , which produces food through intensive agriculture and distributes it through complex food processing and food distribution systems. This system of conventional agriculture relies heavily on fossil fuels , which means that
2100-425: A system with nineteen food classifications: cereals, roots, pulses and nuts, milk, eggs, fish and shellfish, meat, insects, vegetables, fruits, fats and oils, sweets and sugars, spices and condiments, beverages, foods for nutritional uses, food additives, composite dishes and savoury snacks. In a given ecosystem, food forms a web of interlocking chains with primary producers at the bottom and apex predators at
2205-470: A valuable purpose in paleontology because they provide direct evidence of the predation and diet of extinct organisms. Coprolites may range in size from a few millimetres to more than 60 centimetres. Palaeofeces are ancient feces , often found as part of archaeological 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
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#17327880567032310-456: A way that the fruit is a good source of nutrition to the animal who then excretes the seeds some distance away, allowing greater dispersal. Even seed predation can be mutually beneficial, as some seeds can survive the digestion process. Insects are major eaters of seeds, with ants being the only real seed dispersers. Birds, although being major dispersers, only rarely eat seeds as a source of food and can be identified by their thick beak that
2415-425: Is a vacuole formed around a particle absorbed by phagocytosis . The vacuole is formed by the fusion of the cell membrane around the particle. A phagosome is a cellular compartment in which pathogenic microorganisms can be killed and digested. Phagosomes fuse with lysosomes in their maturation process, forming phagolysosomes . In humans, Entamoeba histolytica can phagocytose red blood cells . To aid in
2520-447: Is a fruit if the part eaten is derived from the reproductive tissue , so seeds, nuts and grains are technically fruit. From a culinary perspective, fruits are generally considered the remains of botanically described fruits after grains, nuts, seeds and fruits used as vegetables are removed. Grains can be defined as seeds that humans eat or harvest, with cereal grains (oats, wheat, rice, corn, barley, rye, sorghum and millet) belonging to
2625-696: Is a sensation considered unpleasant characterised by having a sharp, pungent taste. Unsweetened dark chocolate, caffeine , lemon rind, and some types of fruit are known to be bitter. Umami, commonly described as savory, is a marker of proteins and characteristic of broths and cooked meats. Foods that have a strong umami flavor include cheese, meat and mushrooms. While most animals taste buds are located in their mouth, some insects taste receptors are located on their legs and some fish have taste buds along their entire body. Dogs, cats and birds have relatively few taste buds (chickens have about 30), adult humans have between 2000 and 4000, while catfish can have more than
2730-464: Is absorbed into the blood. 95% of nutrient absorption occurs in the small intestine. Water and minerals are reabsorbed back into the blood in the colon (large intestine) where the pH is slightly acidic (about 5.6 ~ 6.9). Some vitamins, such as biotin and vitamin K (K 2 MK7) produced by bacteria in the colon are also absorbed into the blood in the colon. Absorption of water, simple sugar and alcohol also takes place in stomach. Waste material ( feces )
2835-435: Is also triggered by acetylcholine and histamine . The intestinal phase has two parts, the excitatory and the inhibitory. Partially digested food fills the duodenum . This triggers intestinal gastrin to be released. Enterogastric reflex inhibits vagal nuclei, activating sympathetic fibers causing the pyloric sphincter to tighten to prevent more food from entering, and inhibits local reflexes. Protein digestion occurs in
2940-512: Is among the world's most expensive coffees. Paper is also made from elephant dung in Thailand. Haathi Chaap is a brand of paper made from elephant dung. Dog feces was used in the tanning process of leather during the Victorian era . Collected dog feces, known as "pure", "puer", or "pewer", were mixed with water to form a substance known as "bate", because proteolytic enzymes in
3045-472: Is an enzyme that breaks down the disaccharide sucrose , commonly known as table sugar, cane sugar, or beet sugar. Sucrose digestion yields the sugars fructose and glucose which are readily absorbed by the small intestine. DNA and RNA are broken down into mononucleotides by the nucleases deoxyribonuclease and ribonuclease (DNase and RNase) from the pancreas. Food Food is any substance consumed by an organism for nutritional support. Food
3150-536: Is burned as fuel in many countries. Animals such as the giant panda and zebra possess gut bacteria capable of producing biofuel. The bacterium in question, Brocadia anammoxidans , can be used to synthesize the rocket fuel hydrazine . A coprolite is fossilized feces and is classified as a trace fossil . In paleontology they give evidence about the diet of an animal. They were first described by William Buckland in 1829. Prior to this, they were known as "fossil fir cones " and " bezoar stones". They serve
3255-494: Is called constipation . The appearance of human fecal matter varies according to diet and health. Normally it is semisolid, with a mucus coating. A combination of bile and bilirubin , which comes from dead red blood cells , gives feces the typical brown color. After the meconium , the first stool expelled, a newborn's feces contains only bile , which gives it a yellow-green color. Breast feeding babies expel soft, pale yellowish, and not quite malodorous matter; but once
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3360-402: Is caused by acids , such as vinegar in alcoholic beverages. Sour foods include citrus, specifically lemons and limes . Sour is evolutionarily significant as it can signal a food that may have gone rancid due to bacteria. Saltiness is the taste of alkali metal ions such as sodium and potassium. It is found in almost every food in low to moderate proportions to enhance flavor. Bitter taste
3465-731: Is drunk or processed into dairy products (cheese, butter, etc.). Eggs laid by birds and other animals are eaten and bees produce honey , a reduced nectar from flowers that is used as a popular sweetener in many cultures. Some cultures consume blood , such as in blood sausage , as a thickener for sauces, or in a cured , salted form for times of food scarcity, and others use blood in stews such as jugged hare . Animals, specifically humans, typically have five different types of tastes: sweet , sour , salty , bitter , and umami . The differing tastes are important for distinguishing between foods that are nutritionally beneficial and those which may contain harmful toxins. As animals have evolved ,
3570-406: Is eliminated from the rectum during defecation . Digestive systems take many forms. There is a fundamental distinction between internal and external digestion. External digestion developed earlier in evolutionary history, and most fungi still rely on it. In this process, enzymes are secreted into the environment surrounding the organism, where they break down an organic material, and some of
3675-427: Is even provided with its own fertilizer. Organisms that subsist on dead organic matter or detritus are known as detritivores , and play an important role in ecosystems by recycling organic matter back into a simpler form that plants and other autotrophs may absorb once again. This cycling of matter is known as the biogeochemical cycle . To maintain nutrients in soil it is therefore important that feces returns to
3780-414: Is finally moved into the small intestine, where the digestion and absorption of nutrients occurs. Microbes produced in the reticulo-rumen are also digested in the small intestine. Regurgitation has been mentioned above under abomasum and crop, referring to crop milk, a secretion from the lining of the crop of pigeons and doves with which the parents feed their young by regurgitation. Many sharks have
3885-502: Is harder to digest. Carnivores mouths are designed for tearing and biting compared to the grinding action found in herbivores. Herbivores however have comparatively longer digestive tracts and larger stomachs to aid in digesting the cellulose in plants. According to the World Health Organization (WHO), about 600 million people worldwide get sick and 420,000 die each year from eating contaminated food. Diarrhea
3990-406: Is mainly composed of water, lipids , proteins , and carbohydrates . Minerals (e.g., salts) and organic substances (e.g., vitamins ) can also be found in food. Plants, algae , and some microorganisms use photosynthesis to make some of their own nutrients. Water is found in many foods and has been defined as a food by itself. Water and fiber have low energy densities, or calories , while fat
4095-535: Is no singular form, making the word a plurale tantum ; out of various major dictionaries, only one enters variation from plural agreement . "Feces" is used more in biology and medicine than in other fields (reflecting science 's tradition of classical Latin and Neo-Latin ) There are many synonyms in informal registers for feces, just like there are for urine . Many are euphemistic , colloquial , or both; some are profane (such as shit ), whereas most belong chiefly to child-directed speech (such as poo or
4200-470: Is relatively high in paleofeces, making it more reliable than skeletal DNA retrieval. 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
4305-422: Is skeletal muscle on the floor of the mouth of most vertebrates, that manipulates food for chewing ( mastication ) and swallowing (deglutition). It is sensitive and kept moist by saliva . The underside of the tongue is covered with a smooth mucous membrane . The tongue also has a touch sense for locating and positioning food particles that require further chewing. The tongue is used to roll food particles into
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4410-506: Is the most common illness caused by consuming contaminated food, with about 550 million cases and 230,000 deaths from diarrhea each year. Children under five years of age account for 40% of the burden of foodborne illness, with 125,000 deaths each year. A 2003 World Health Organization (WHO) report concluded that about 30% of reported food poisoning outbreaks in the WHO European Region occur in private homes. According to
4515-738: Is the most energy-dense component. Some inorganic (non-food) elements are also essential for plant and animal functioning. Human food can be classified in various ways, either by related content or by how it is processed. The number and composition of food groups can vary. Most systems include four basic groups that describe their origin and relative nutritional function: Vegetables and Fruit, Cereals and Bread, Dairy, and Meat. Studies that look into diet quality group food into whole grains/cereals, refined grains/cereals, vegetables, fruits, nuts, legumes, eggs, dairy products, fish, red meat, processed meat, and sugar-sweetened beverages. The Food and Agriculture Organization and World Health Organization use
4620-565: Is the precursor to proteins, nucleic acids, and most vitamins. Since the advent of industrial process for nitrogen fixation, the Haber-Bosch Process , the majority of ammonia in the world is human-made. Plants as a food source are divided into seeds, fruits, vegetables, legumes, grains and nuts. Where plants fall within these categories can vary, with botanically described fruits such as the tomato, squash, pepper and eggplant or seeds like peas commonly considered vegetables. Food
4725-606: Is the prototypic system. In the nitrogen-fixing Rhizobia , conjugative elements naturally engage in inter- kingdom conjugation. Such elements as the Agrobacterium Ti or Ri plasmids contain elements that can transfer to plant cells. Transferred genes enter the plant cell nucleus and effectively transform the plant cells into factories for the production of opines , which the bacteria use as carbon and energy sources. Infected plant cells form crown gall or root tumors . The Ti and Ri plasmids are thus endosymbionts of
4830-521: Is the scientific terminology, while the term stool is also commonly used in medical contexts. Outside of scientific contexts, these terms are less common, with the most common layman's term being poop or poo . The term shit is also in common use, although it is widely considered vulgar or offensive. There are many other terms, see below. The word faeces is the plural of the Latin word faex meaning "dregs". In most English-language usage , there
4935-439: Is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fibre, especially cellulose and hemi-cellulose , is primarily broken down into the volatile fatty acids , acetic acid , propionic acid and butyric acid in these chambers (the reticulo-rumen) by microbes: ( bacteria , protozoa , and fungi). In the omasum, water and many of the inorganic mineral elements are absorbed into
5040-402: Is then released, and the glucose stored as an energy reserve. Photosynthetic plants, algae and certain bacteria often represent the lowest point of the food chains, making photosynthesis the primary source of energy and food for nearly all life on earth. Plants also absorb important nutrients and minerals from the air, natural waters, and soil. Carbon, oxygen and hydrogen are absorbed from
5145-562: Is used as a cement to make adobe ( mudbrick ) huts, or even in throwing sports, especially with cow and camel dung. Kopi luwak , or civet coffee, is coffee made from coffee beans that have been eaten and excreted by Asian palm civets ( Paradoxurus hermaphroditus ). Giant pandas provide fertilizer for the world's most expensive green tea . In Malaysia , tea is made from the droppings of stick insects fed on guava leaves. In northern Thailand , elephants are used to digest coffee beans in order to make Black Ivory coffee , which
5250-406: Is used to crack open the seed coat. Mammals eat a more diverse range of seeds, as they are able to crush harder and larger seeds with their teeth. Animals are used as food either directly or indirectly. This includes meat, eggs, shellfish and dairy products like milk and cheese. They are an important source of protein and are considered complete proteins for human consumption as they contain all
5355-428: Is usually of plant, animal, or fungal origin and contains essential nutrients such as carbohydrates , fats , proteins , vitamins , or minerals . The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or stimulate growth. Different species of animals have different feeding behaviours that satisfy the needs of their metabolisms and have evolved to fill
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#17327880567035460-785: The International Association for Food Protection , the World Resources Institute , the World Food Programme , the Food and Agriculture Organization , and the International Food Information Council . Food is any substance consumed to provide nutritional support and energy to an organism . It can be raw, processed, or formulated and is consumed orally by animals for growth, health, or pleasure. Food
5565-750: The Poaceae (grass) family and pulses coming from the Fabaceae (legume) family. Whole grains are foods that contain all the elements of the original seed (bran, germ, and endosperm ). Nuts are dry fruits, distinguishable by their woody shell. Fleshy fruits (distinguishable from dry fruits like grain, seeds and nuts) can be further classified as stone fruits (cherries and peaches), pome fruits (apples, pears), berries (blackberry, strawberry), citrus (oranges, lemon), melons (watermelon, cantaloupe), Mediterranean fruits (grapes, fig), tropical fruits (banana, pineapple). Vegetables refer to any other part of
5670-516: The Pseudomonas fluorescens cell adhesion protein LapA of 900 kDa. A type III secretion system means that a molecular syringe is used through which a bacterium (e.g. certain types of Salmonella , Shigella , Yersinia ) can inject nutrients into protist cells. One such mechanism was first discovered in Y. pestis and showed that toxins could be injected directly from the bacterial cytoplasm into
5775-403: The cephalic phase , gastric phase , and intestinal phase . The cephalic phase occurs at the sight, thought and smell of food, which stimulate the cerebral cortex . Taste and smell stimuli are sent to the hypothalamus and medulla oblongata . After this it is routed through the vagus nerve and release of acetylcholine. Gastric secretion at this phase rises to 40% of maximum rate. Acidity in
5880-441: The diet and health 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, using lipid analysis and ancient DNA analysis. The success rate of usable DNA extraction
5985-504: The palindromic word poop ) or to crude humor (such as crap , dump , load and turd .). The feces of animals often have special names (some of them are slang), for example: In all human cultures, feces elicit varying degrees of disgust in adults. Children under two years typically have no disgust response to it, suggesting it is culturally derived. Disgust toward feces appears to be strongest in cultures where flush toilets make olfactory contact with human feces minimal. Disgust
6090-533: The WHO and CDC , in the USA alone, annually, there are 76 million cases of foodborne illness leading to 325,000 hospitalizations and 5,000 deaths. From 2011 to 2016, on average, there were 668,673 cases of foodborne illness and 21 deaths each year. In addition, during this period, 1,007 food poisoning outbreaks with 30,395 cases of food poisoning were reported. Feces Feces ( or faeces ; sg. : faex ) are
6195-420: The ability to turn their stomachs inside out and evert it out of their mouths in order to get rid of unwanted contents (perhaps developed as a way to reduce exposure to toxins). Other animals, such as rabbits and rodents , practise coprophagia behaviours – eating specialised faeces in order to re-digest food, especially in the case of roughage. Capybara, rabbits, hamsters and other related species do not have
6300-434: The absorption of nutrients by increasing the surface area of the intestine. Bile helps in emulsification of fats and also activates lipases. In the large intestine, the passage of food is slower to enable fermentation by the gut flora to take place. Here, water is absorbed and waste material stored as feces to be removed by defecation via the anal canal and anus . Different phases of digestion take place including:
6405-607: The air or water and are the basic nutrients needed for plant survival. The three main nutrients absorbed from the soil for plant growth are nitrogen, phosphorus and potassium, with other important nutrients including calcium, sulfur, magnesium, iron boron, chlorine, manganese, zinc, copper molybdenum and nickel. Bacteria and other microorganisms also form the lower rungs of the food chain. They obtain their energy from photosynthesis or by breaking down dead organisms, waste or chemical compounds. Some form symbiotic relationships with other organisms to obtain their nutrients. Bacteria provide
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#17327880567036510-440: The apex predators, the animals that have no known predators in its ecosystem. Humans are considered apex predators. Humans are omnivores, finding sustenance in vegetables, fruits, cooked meat, milk, eggs, mushrooms and seaweed. Cereal grain is a staple food that provides more food energy worldwide than any other type of crop. Corn (maize) , wheat, and rice account for 87% of all grain production worldwide. Just over half of
6615-468: The archaeological record is so direct an indicator. A process that preserves feces in a way that they may be analyzed later is the Maillard 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. Animal dung occasionally
6720-423: 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
6825-514: The baby begins to eat, and the body starts expelling bilirubin from dead red blood cells, its matter acquires the familiar brown color. 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. The feces of animals, e.g. guano and manure , often are used as fertilizer . Dry animal dung , such as that of camel , bison and cattle ,
6930-412: The bacteria required to properly digest vegetation. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to get any nutritional value from many plant components. An earthworm 's digestive system consists of a mouth, pharynx , esophagus , crop, gizzard , and intestine . The mouth is surrounded by strong lips, which act like
7035-404: The bacteria, which are in turn endosymbionts (or parasites) of the infected plant. The Ti and Ri plasmids are themselves conjugative. Ti and Ri transfer between bacteria uses an independent system (the tra , or transfer, operon) from that for inter-kingdom transfer (the vir , or virulence , operon). Such transfer creates virulent strains from previously avirulent Agrobacteria . In addition to
7140-411: The blood stream. The abomasum is the fourth and final stomach compartment in ruminants. It is a close equivalent of a monogastric stomach (e.g., those in humans or pigs), and digesta is processed here in much the same way. It serves primarily as a site for acid hydrolysis of microbial and dietary protein, preparing these protein sources for further digestion and absorption in the small intestine. Digesta
7245-464: The body. In most vertebrates , digestion is a multistage process in the digestive system, starting from ingestion of raw materials, most often other organisms. Ingestion usually involves some type of mechanical and chemical processing. Digestion is separated into four steps: Underlying the process is muscle movement throughout the system through swallowing and peristalsis . Each step in digestion requires energy, and thus imposes an "overhead charge" on
7350-431: The case of human feces , fecal transplants or fecal bacteriotherapy are in use. Urine and feces together are called excreta . The distinctive odor of feces is due to skatole , and thiols ( sulfur -containing compounds), as well as amines and carboxylic acids. Skatole is produced from tryptophan via indoleacetic acid. Decarboxylation gives skatole. The perceived bad odor of feces has been hypothesized to be
7455-423: The consequent "soup". In others, once potential nutrients or food is inside the organism , digestion can be conducted to a vesicle or a sac-like structure, through a tube, or through several specialized organs aimed at making the absorption of nutrients more efficient. Bacteria use several systems to obtain nutrients from other organisms in the environments. In a channel transport system, several proteins form
7560-534: The cytoplasm of its host's cells rather than be secreted into the extracellular medium. The conjugation machinery of some bacteria (and archaeal flagella) is capable of transporting both DNA and proteins. It was discovered in Agrobacterium tumefaciens , which uses this system to introduce the Ti plasmid and proteins into the host, which develops the crown gall (tumor). The VirB complex of Agrobacterium tumefaciens
7665-408: The digestion of their food, animals evolved organs such as beaks, tongues , radulae , teeth, crops, gizzards, and others. Birds have bony beaks that are specialised according to the bird's ecological niche . For example, macaws primarily eat seeds, nuts, and fruit, using their beaks to open even the toughest seed. First they scratch a thin line with the sharp point of the beak, then they shear
7770-508: The dog feces helped to relax the fibrous structure of the hide before the final stages of tanning. Dog feces collectors were known as pure finders . Elephants, hippos , koalas and pandas are born with sterile intestines, and require bacteria obtained from eating the feces of their mothers to digest vegetation. In India, cow dung and cow urine are major ingredients of the traditional Hindu drink Panchagavya . Politician Shankarbhai Vegad stated that they can cure cancer . Feces
7875-450: The energy made available from absorbed substances. Differences in that overhead cost are important influences on lifestyle, behavior, and even physical structures. Examples may be seen in humans, who differ considerably from other hominids (lack of hair, smaller jaws and musculature, different dentition, length of intestines, cooking, etc.). The major part of digestion takes place in the small intestine. The large intestine primarily serves as
7980-567: The essential amino acids that the human body needs. One 4-ounce (110 g) steak, chicken breast or pork chop contains about 30 grams of protein. One large egg has 7 grams of protein. A 4-ounce (110 g) serving of cheese has about 15 grams of protein. And 1 cup of milk has about 8 grams of protein. Other nutrients found in animal products include calories, fat, essential vitamins (including B12) and minerals (including zinc, iron, calcium, magnesium). Food products produced by animals include milk produced by mammary glands , which in many cultures
8085-425: The feces of their mothers to gain essential gut flora , or by other animals such as dogs, rabbits, and monkeys. Feces and urine, which reflect ultraviolet light, are important to raptors such as kestrels , who can see the near ultraviolet and thus find their prey by their middens and territorial markers. Seeds also may be found in feces. Animals who eat fruit are known as frugivores . An advantage for
8190-447: The food and agricultural systems are one of the major contributors to climate change , accounting for as much as 37% of total greenhouse gas emissions . The food system has significant impacts on a wide range of other social and political issues, including sustainability , biological diversity , economics , population growth , water supply , and food security . Food safety and security are monitored by international agencies like
8295-482: The food further and this is combined with the churning action of the stomach. Mainly proteins are digested in stomach. The partially digested food enters the duodenum as a thick semi-liquid chyme . In the small intestine, the larger part of digestion takes place and this is helped by the secretions of bile , pancreatic juice and intestinal juice . The intestinal walls are lined with villi , and their epithelial cells are covered with numerous microvilli to improve
8400-416: The form of trypsinogen , which is activated in the duodenum by enterokinase to form trypsin. Trypsin then cleaves proteins to smaller polypeptides. Digestion of some fats can begin in the mouth where lingual lipase breaks down some short chain lipids into diglycerides . However fats are mainly digested in the small intestine. The presence of fat in the small intestine produces hormones that stimulate
8505-550: The form of starch, fructose, glucose and other sugars. Most vitamins are found from plant sources, with exceptions of vitamin D and vitamin B 12 . Minerals can also be plentiful or not. Fruit can consist of up to 90% water, contain high levels of simple sugars that contribute to their sweet taste, and have a high vitamin C content. Compared to fleshy fruit (excepting Bananas) vegetables are high in starch, potassium , dietary fiber, folate and vitamins and low in fat and calories. Grains are more starch based and nuts have
8610-412: The gizzard churn and mix the mass of food and dirt. When the churning is complete, the glands in the walls of the gizzard add enzymes to the thick paste, which helps chemically breakdown the organic matter. By peristalsis , the mixture is sent to the intestine where friendly bacteria continue chemical breakdown. This releases carbohydrates, protein, fat, and various vitamins and minerals for absorption into
8715-428: The ideal conditions of pH for amylase to work; and other electrolytes ( Na , K , Cl ). About 30% of starch is hydrolyzed into disaccharide in the oral cavity (mouth). After undergoing mastication and starch digestion, the food will be in the form of a small, round slurry mass called a bolus . It will then travel down the esophagus and into the stomach by the action of peristalsis . Gastric juice in
8820-434: The mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva . Saliva, a liquid secreted by the salivary glands , contains salivary amylase , an enzyme which starts the digestion of starch in the food. The saliva also contains mucus , which lubricates the food; the electrolyte hydrogencarbonate ( HCO 3 ), which provides
8925-417: The number of chews per bite increases relevant gut hormones and may decrease self-reported hunger and food intake. When the pyloric sphincter valve opens, partially digested food ( chyme ) enters the duodenum where it mixes with digestive enzymes from the pancreas and bile juice from the liver and then passes through the small intestine, in which digestion continues. When the chyme is fully digested, it
9030-572: The outside that functions as both a mouth and an anus : waste and undigested matter is excreted through the mouth/anus, which can be described as an incomplete gut . In a plant such as the Venus flytrap that can make its own food through photosynthesis, it does not eat and digest its prey for the traditional objectives of harvesting energy and carbon, but mines prey primarily for essential nutrients (nitrogen and phosphorus in particular) that are in short supply in its boggy, acidic habitat. A phagosome
9135-405: The physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes . Mechanical digestion takes place in the mouth through mastication and in the small intestine through segmentation contractions . In chemical digestion , enzymes break down food into the small compounds that the body can use. In the human digestive system , food enters
9240-413: The plant that can be eaten, including roots, stems, leaves, flowers, bark or the entire plant itself. These include root vegetables (potatoes and carrots), bulbs (onion family), flowers (cauliflower and broccoli), leaf vegetables ( spinach and lettuce) and stem vegetables (celery and asparagus ). The carbohydrate, protein and lipid content of plants is highly variable. Carbohydrates are mainly in
9345-450: The products diffuse back to the organism. Animals have a tube ( gastrointestinal tract ) in which internal digestion occurs, which is more efficient because more of the broken down products can be captured, and the internal chemical environment can be more efficiently controlled. Some organisms, including nearly all spiders , secrete biotoxins and digestive chemicals (e.g., enzymes) into the extracellular environment prior to ingestion of
9450-667: The release of pancreatic lipase from the pancreas and bile from the liver which helps in the emulsification of fats for absorption of fatty acids . Complete digestion of one molecule of fat (a triglyceride ) results a mixture of fatty acids, mono- and di-glycerides, but no glycerol . In humans, dietary starches are composed of glucose units arranged in long chains called amylose, a polysaccharide . During digestion, bonds between glucose molecules are broken by salivary and pancreatic amylase , resulting in progressively smaller chains of glucose. This results in simple sugars glucose and maltose (2 glucose molecules) that can be absorbed by
9555-413: The release of more gastric juices. As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach. Inhibition of gastrin and gastric acid secretion is lifted. This triggers G cells to release gastrin , which in turn stimulates parietal cells to secrete gastric acid. Gastric acid is about 0.5% hydrochloric acid , which lowers the pH to the desired pH of 1–3. Acid release
9660-422: The same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which is waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. Pepsin breaks down proteins into peptides or proteoses , which is further broken down into dipeptides and amino acids by enzymes in the small intestine. Studies suggest that increasing
9765-430: The secretion of saliva and its digestive enzymes. Food is formed into a bolus by the mechanical mastication and swallowed into the esophagus from where it enters the stomach through the action of peristalsis . Gastric juice contains hydrochloric acid and pepsin which would damage the walls of the stomach and mucus and bicarbonates are secreted for protection. In the stomach further release of enzymes break down
9870-405: The seed open with the sides of the beak. The mouth of the squid is equipped with a sharp horny beak mainly made of cross-linked proteins . It is used to kill and tear prey into manageable pieces. The beak is very robust, but does not contain any minerals, unlike the teeth and jaws of many other organisms, including marine species. The beak is the only indigestible part of the squid. The tongue
9975-612: The small intestine. Lactase is an enzyme that breaks down the disaccharide lactose to its component parts, glucose and galactose . Glucose and galactose can be absorbed by the small intestine. Approximately 65 percent of the adult population produce only small amounts of lactase and are unable to eat unfermented milk-based foods. This is commonly known as lactose intolerance . Lactose intolerance varies widely by genetic heritage; more than 90 percent of peoples of east Asian descent are lactose intolerant, in contrast to about 5 percent of people of northern European descent. Sucrase
10080-583: The solid or semi-solid remains of food that was not digested in the small intestine , and has been broken down by bacteria in the large intestine . Feces contain a relatively small amount of metabolic waste products such as bacterially altered bilirubin , and dead epithelial cells from the lining of the gut. Feces are discharged through the anus or cloaca during defecation . Feces can be used as fertilizer or soil conditioner in agriculture. They can also be burned as fuel or dried and used for construction . Some medicinal uses have been found. In
10185-399: The speedy application of medication into the cardiovascular system, bypassing the gastrointestinal tract. Teeth (singular tooth) are small whitish structures found in the jaws (or mouths) of many vertebrates that are used to tear, scrape, milk and chew food. Teeth are not made of bone, but rather of tissues of varying density and hardness, such as enamel, dentine and cementum. Human teeth have
10290-424: The stomach and duodenum in which 3 main enzymes, pepsin secreted by the stomach and trypsin and chymotrypsin secreted by the pancreas, break down food proteins into polypeptides that are then broken down by various exopeptidases and dipeptidases into amino acids . The digestive enzymes however are mostly secreted as their inactive precursors, the zymogens . For example, trypsin is secreted by pancreas in
10395-401: The stomach and gastrointestinal tract , and the process finishes with defecation. The human gastrointestinal tract is around 9 metres (30 feet) long. Food digestion physiology varies between individuals and upon other factors such as the characteristics of the food and size of the meal, and the process of digestion normally takes between 24 and 72 hours. Digestion begins in the mouth with
10500-435: The stomach is not buffered by food at this point and thus acts to inhibit parietal (secretes acid) and G cell (secretes gastrin) activity via D cell secretion of somatostatin . The gastric phase takes 3 to 4 hours. It is stimulated by distension of the stomach, presence of food in stomach and decrease in pH . Distention activates long and myenteric reflexes. This activates the release of acetylcholine , which stimulates
10605-512: The stomach starts protein digestion . Gastric juice mainly contains hydrochloric acid and pepsin . In infants and toddlers , gastric juice also contains rennin to digest milk proteins. As the first two chemicals may damage the stomach wall, mucus and bicarbonates are secreted by the stomach. They provide a slimy layer that acts as a shield against the damaging effects of chemicals like concentrated hydrochloric acid while also aiding lubrication. Hydrochloric acid provides acidic pH for pepsin. At
10710-448: The tastes that provide the most energy are the most pleasant to eat while others are not enjoyable, although humans in particular can acquire a preference for some substances which are initially unenjoyable. Water, while important for survival, has no taste. Sweetness is almost always caused by a type of simple sugar such as glucose or fructose , or disaccharides such as sucrose , a molecule combining glucose and fructose. Sourness
10815-523: The top. Other aspects of the web include detrovores (that eat detritis ) and decomposers (that break down dead organisms). Primary producers include algae, plants, bacteria and protists that acquire their energy from sunlight. Primary consumers are the herbivores that consume the plants, and secondary consumers are the carnivores that consume those herbivores. Some organisms, including most mammals and birds, diet consists of both animals and plants, and they are considered omnivores. The chain ends with
10920-535: The use of the multiprotein complexes listed above, gram-negative bacteria possess another method for release of material: the formation of outer membrane vesicles . Portions of the outer membrane pinch off, forming spherical structures made of a lipid bilayer enclosing periplasmic materials. Vesicles from a number of bacterial species have been found to contain virulence factors, some have immunomodulatory effects, and some can directly adhere to and intoxicate host cells. While release of vesicles has been demonstrated as
11025-403: The world's crops are used to feed humans (55 percent), with 36 percent grown as animal feed and 9 percent for biofuels . Fungi and bacteria are also used in the preparation of fermented foods like bread , wine , cheese and yogurt . During photosynthesis , energy from the sun is absorbed and used to transform water and carbon dioxide in the air or soil into oxygen and glucose. The oxygen
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