Digestive enzymes take part in the chemical process of digestion , which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes in the mouth , stomach , pancreas , and duodenum , before being able to be absorbed into the bloodstream. Initial breakdown is achieved by chewing (mastication) and the use of digestive enzymes of saliva . Once in the stomach further mechanical churning takes place mixing the food with secreted gastric acid . Digestive gastric enzymes take part in some of the chemical process needed for absorption . Most of the enzymatic activity, and hence absorption takes place in the duodenum.
63-529: [REDACTED] Look up digest in Wiktionary, the free dictionary. Digest may refer to: Biology [ edit ] Digestion of food Restriction digest Literature and publications [ edit ] The Digest , formerly the English and Empire Digest Digest size magazine format Digest (Roman law) , also known as Pandects ,
126-407: 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
189-424: 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
252-410: 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
315-428: 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
378-731: A digest of Roman law Digest (poetry collection) , 2014 poetry collection Computer science and electronic security [ edit ] Digest, a MIME Multipart Subtype Digest access authentication Digital Geographic Exchange Standard Email digest Message digest or hash algorithm (in cryptography) Other uses [ edit ] trade name of the drug Lansoprazole See also [ edit ] Publications [ edit ] The Literary Digest Architectural Digest Writer's Digest Reader's Digest Baseball Digest Gun Digest Golf Digest Consumers Digest Inventors Digest Football Digest Topics referred to by
441-408: 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
504-411: 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
567-483: 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
630-589: 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
693-407: 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 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
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#1732765435710756-426: 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
819-493: 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 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
882-435: 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
945-432: 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. Digestive enzyme Digestive enzymes are found in
1008-400: Is different from Wikidata All article disambiguation pages All disambiguation pages Digestion 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
1071-415: 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
1134-410: Is secreted eventually via the pancreatic duct into the duodenum. Digestive or exocrine function of pancreas is as significant to the maintenance of health as its endocrine function. Two of the population of cells in the pancreatic parenchyma make up its digestive enzymes: Pancreatic juice , composed of the secretions of both ductal and acinar cells, contains the following digestive enzymes: Some of
1197-422: 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
1260-590: 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 ) 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
1323-607: 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
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#17327654357101386-439: 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
1449-403: 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
1512-402: 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 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
1575-416: The duodenum : Throughout the lining of the small intestine there are numerous brush border enzymes whose function is to further break down the chyme released from the stomach into absorbable particles. These enzymes are absorbed whilst peristalsis occurs. Some of these enzymes include: In carnivorous plants, digestive enzymes and acids break down insects and in some plants small animals. In some plants,
1638-405: The esophagus and into the stomach by the action of peristalsis . Gastric juice in 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
1701-578: The gastrointestinal tract . In the human digestive system , the main sites of digestion are the mouth, stomach, and small intestine. Digestive enzymes are secreted by different exocrine glands including salivary glands , gastric glands , secretory cells in the pancreas , and secretory glands in the small intestine . In some carnivorous plants plant-specific digestive enzymes are used to break down their captured organisms. Complex food substances that are eaten must be broken down into simple, soluble, and diffusible substances before they can be absorbed. In
1764-420: 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
1827-434: 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:
1890-412: 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
1953-404: 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
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2016-565: The bacterial cytoplasm into 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
2079-411: 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
2142-464: 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
2205-408: 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
2268-414: 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 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
2331-673: The digestive tracts of animals (including humans) and in the tracts of carnivorous plants , where they aid in the digestion of food, as well as inside cells , especially in their lysosomes , where they function to maintain cellular survival. Digestive enzymes are classified based on their target substrates : lipases split fatty acids into fats and oils ; proteases and peptidases split proteins into small peptides and amino acids ; amylases split carbohydrates such as starch and sugars into simple sugars such as glucose , and nucleases split nucleic acids into nucleotides . Digestive enzymes are found throughout much of
2394-450: 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
2457-496: The environment surrounding the organism, where they break down an organic material, and some of 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
2520-520: The environments. In a channel transport system, several proteins form 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
2583-402: The extracellular environment prior to ingestion of 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
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2646-482: 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
2709-418: The food, and also in an enzymatic sense, by digesting it. The following are enzymes produced by the stomach and their respective function: Pancreas is both an endocrine and an exocrine gland, in that it functions to produce endocrinic hormones released into the circulatory system (such as insulin , and glucagon ), to control glucose metabolism, and also to secrete digestive / exocrinic pancreatic juice, which
2772-421: The food; the electrolyte hydrogencarbonate ( HCO 3 ), which provides 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
2835-417: 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
2898-412: 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
2961-405: The leaf collapses on the prey to increase contact, others have a small vessel of digestive liquid . Then digestion fluids are used to digest the prey to get at the needed nitrates and phosphorus . The absorption of the needed nutrients are usually more efficient than in other plants. Digestive enzymes independently came about in carnivorous plants and animals. Some carnivorous plants like
3024-407: The oral cavity, salivary glands secrete an array of enzymes and substances that aid in digestion and also disinfection. They include the following: Of note is the diversity of the salivary glands. There are two types of salivary glands: The enzymes that are secreted in the stomach are gastric enzymes . The stomach plays a major role in digestion, both in a mechanical sense by mixing and crushing
3087-573: 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
3150-479: The preceding endogenous enzymes have pharmaceutical counterparts ( pancreatic enzymes ) that are administered to people with exocrine pancreatic insufficiency . The pancreas's exocrine function owes part of its notable reliability to biofeedback mechanisms controlling secretion of the juice. The following significant pancreatic biofeedback mechanisms are essential to the maintenance of pancreatic juice balance/production: The following enzymes/hormones are produced in
3213-669: 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
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#17327654357103276-413: 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
3339-409: The same term [REDACTED] This disambiguation page lists articles associated with the title Digest . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Digest&oldid=1237692868 " Category : Disambiguation pages Hidden categories: Short description
3402-431: 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
3465-406: 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
3528-548: The small Escherichia coli peptide colicin V, (10 kDa) to 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
3591-447: The small compounds that the body can use. In the human digestive system , food enters 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
3654-613: 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
3717-399: 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
3780-424: 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
3843-403: 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
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#17327654357103906-435: 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
3969-537: 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
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