Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: How long is the human small intestine?
The length of the small intestine can vary greatly, from as short as 2.75m (9.0ft) to as long as 10.49m (34.4ft), also depending on the measuring technique used.[3] The typical length in a living person is 3m-5m.[4][5] The length depends both on how tall the person is and how the length is measured.[3] Taller people generally have a longer small intestine and measurements are generally longer after death and when the bowel is empty.[3]
The human gastrointestinal tract consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine, and is a 9-meter-long continuous tube; the largest body surface area exposed to the external environment. The intestine offers nutrients and protection to microbes, enabling them to thrive. Therefore, the intestine is home to a microbial community of 100 trillion beneficial and pathogenic bacteria, archaea, viruses, and eukaryotes. For reference, humans are home to 10 to 10 bacteria in total.
Lepidotrichia are bony, bilaterally-paired, segmented fin rays found in bony fishes. They develop around actinotrichia as part of the dermal exoskeleton. Lepidotrichia may have some cartilage or bone in them as well. They are actually segmented and appear as a series of disks stacked one on top of another. The genetic basis for the formation of the fin rays is thought to be genes coding for the proteins actinodin 1 and actinodin 2.As with other vertebrates, the intestines of fish consist of two segments, the small intestine and the large intestine. In most higher vertebrates, the small intestine is further divided into the duodenum and other parts. In fish, the divisions of the small intestine are not as clear, and the terms "anterior intestine" or "proximal intestine" may be used instead of duodenum. In bony fish, the intestine is relatively short, typically around one and a half times the length of the fish's body. It commonly has a number of "pyloric caeca", small pouch-like structures along its length that help to increase the overall surface area of the organ for digesting food. There is no ileocaecal valve in teleosts, with the boundary between the small intestine and the rectum being marked only by the end of the digestive epithelium. There is no small intestine as such in non-teleost fish, such as sharks, sturgeons, and lungfish. Instead, the digestive part of the gut forms a "spiral intestine", connecting the stomach to the rectum. In this type of gut, the intestine itself is relatively straight, but has a long fold running along the inner surface in a spiral fashion, sometimes for dozens of turns. This fold creates a valve-like structure that greatly increases both the surface area and the effective length of the intestine. The lining of the spiral intestine is similar to that of the small intestine in teleosts and non-mammalian tetrapods. In lampreys, the spiral valve is extremely small, possibly because their diet requires little digestion. Hagfish have no spiral valve at all, with digestion occurring for almost the entire length of the intestine, which is not subdivided into different regions.
It is approximately 1.5cm in diameter in newborns after 35 weeks of gestational age,[6] and 2.5–3cm (1inch) in diameter in adults. On abdominal X-rays, the small intestine is considered to be abnormally dilated when the diameter exceeds 3cm.[7][8] On CT scans, a diameter of over 2.5cm is considered abnormally dilated.[7][9] The surface area of the human small intestinal mucosa, due to enlargement caused by folds, villi and microvilli, averages 30 square meters.[10]
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 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.
The zàng-fǔ () organs are functional entities stipulated by Traditional Chinese medicine (TCM). They constitute the centre piece of TCM's general concept of how the human body works. The term zàng (脏) refers to the organs considered to be yin in nature – Heart, Liver, Spleen, Lung, Kidney – while fǔ (腑) refers to the yang organs – Small Intestine, Large Intestine, Gall Bladder, Urinary Bladder, Stomach and Sānjiaō.
"Fasciolopsis buski" is commonly called the giant intestinal fluke, because it is an exceptionally large parasitic fluke, and the largest known to parasitise humans. Its size is variable and a mature specimen might be as little as 2 cm long, but the body may grow to a length of 7.5 cm and a width of 2.5 cm. It is a common parasite of humans and pigs and is most prevalent in Southern and Southeastern Asia. It is a member of the family Fasciolidae in the order Plagiorchiida. The Echinostomida are members of the class Trematoda, the flukes. The fluke differs from most species that parasitise large mammals, in that they inhabit the gut rather than the liver as "Fasciola" species do. "Fasciolopsis buski" generally occupies the upper region of the small intestine, but in heavy infestations can also be found in the stomach and lower regions of the intestine. "Fasciolopsis buski" is the cause of the pathological condition fasciolopsiasis.
All bilaterians have a gastrointestinal tract, also called a gut or an alimentary canal. This is a tube that transfers food to the organs of digestion. In large bilaterians, the gastrointestinal tract generally also has an exit, the anus, by which the animal disposes of feces (solid wastes). Some small bilaterians have no anus and dispose of solid wastes by other means (for example, through the mouth). The human gastrointestinal tract consists of the esophagus, stomach, and intestines, and is divided into the upper and lower gastrointestinal tracts. The GI tract includes all structures between the mouth and the anus, forming a continuous passageway that includes the main organs of digestion, namely, the stomach, small intestine, and large intestine. However, the complete human digestive system is made up of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver and gallbladder). The tract may also be divided into foregut, midgut, and hindgut, reflecting the embryological origin of each segment. The whole human GI tract is about nine metres (30 feet) long at autopsy. It is considerably shorter in the living body because the intestines, which are tubes of smooth muscle tissue, maintain constant muscle tone in a halfway-tense state but can relax in spots to allow for local distention and peristalsis.
When ingested along the diet, genistin is readily converted to its aglycone form, genistein. It is hydrolyzed by removing the covalently bound glucose to form genistein and that genistein is the form of the compound that is absorbed in the intestine and is the form responsible for the biological activities of the isoflavone. The digestive metabolism was first demonstrated in 2002 that the gut microflora played a large role in the conversion of genistin to genistein. It was later found that enzymes present in the human small intestine and liver also have the ability to convert the isoflavone. Hydrolysis actually starts very quickly in the digestive system once genistin is ingested, conversion begins in the mouth and then continues in the small intestine. Moreover, both human saliva and the intestinal cell-free extract from mice can cause the complete conversion.
Giardiasis is a disease of the small intestine caused by a protist parasite "Giardia lamblia". This does not spread but remains confined to the lumen of the small intestine. It can often be asymptomatic, but as often can be indicated by a variety of symptoms. Giardiasis is the most common pathogenic parasitic infection in humans.
Human feces (or faeces in British English; ) are the solid or semisolid remains of the food that could not be digested or absorbed in the small intestine of humans, 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. Human feces have similarities to feces of other animals and 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.
Definitive hosts include fish-eating birds and mammals. The most common definitive hosts are the domestic dog, cat, and red fox. Humans are also definitive hosts for "N. salmincola". A long list of experimental definitive hosts include the hamster and wood rat. An experimental study failed to infect two white rats and two white mice. Trematodes exist along the whole length of the small intestine in smaller animals like hamsters, while they exist only in the upper end of the small intestine in larger animals like dogs.
The lower gastrointestinal tract (GI), includes the small intestine and all of the large intestine. The intestine is also called the bowel or the gut. The lower GI starts at the pyloric sphincter of the stomach and finishes at the anus. The small intestine is subdivided into the duodenum, the jejunum and the ileum. The cecum marks the division between the small and large intestine. The large intestine includes the rectum and anal canal.
Most food digestion takes place in the small intestine. Segmentation contractions act to mix and move the chyme more slowly in the small intestine allowing more time for absorption (and these continue in the large intestine). In the duodenum, pancreatic lipase is secreted together with a co-enzyme, colipase to further digest the fat content of the chyme. From this breakdown, smaller particles of emulsified fats called chylomicrons are produced. There are also digestive cells called enterocytes lining the intestines (the majority being in the small intestine). They are unusual cells in that they have villi on their surface which in turn have innumerable microvilli on their surface. All these villi make for a greater surface area, not only for the absorption of chyme but also for its further digestion by large numbers of digestive enzymes present on the microvilli.
Several enzymes that are present in the intestinal lumen may be involved in the hydrolysis of dietary retinyl esters. Cholesterol esterase is secreted into the intestinal lumen from the pancreas and has been shown, in vitro, to display retinyl ester hydrolase activity. In addition, a retinyl ester hydrolase that is intrinsic to the brush-border membrane of the small intestine has been characterized in the rat as well as in the human. The different hydrolyzing enzymes are activated by different types of bile salts and have distinct substrate specificities. For example, whereas the pancreatic esterase is selective for short-chain retinyl esters, the brush-border membrane enzyme preferentially hydrolyzes retinyl esters containing a long-chain fatty acid such as palmitate or stearate. Retinol enters the absorptive cells of the small intestine, preferentially in the all-trans-retinol form.
There is no small intestine as such in non-teleost fish, such as sharks, sturgeons, and lungfish. Instead, the digestive part of the gut forms a spiral intestine, connecting the stomach to the rectum. In this type of gut, the intestine itself is relatively straight but has a long fold running along the inner surface in a spiral fashion, sometimes for dozens of turns. This valve greatly increases both the surface area and the effective length of the intestine. The lining of the spiral intestine is similar to that of the small intestine in teleosts and non-mammalian tetrapods.[21]
Intestine transplantation dates back to 1959, when a team of surgeons at the University of Minnesota led by Richard C. Lillehei reported successful transplantation of the small intestine in dogs. Five years later in 1964, Ralph Deterling in Boston attempted the first human intestinal transplant, albeit unsuccessfully. For the next two decades, attempts at transplanting the small intestine in humans were met with universal failure, and patients died of technical complications, sepsis, or graft rejection. However, the discovery of the immunosuppressant ciclosporin in 1972 triggered a revolution in the field of transplant medicine. Due to this discovery, in 1988, the first successful intestinal transplant was performed in Germany by E. Deltz, followed shortly by teams in France and Canada. Intestinal transplantation was no longer an experimental procedure, but rather a life-saving therapy. In 1990, a newer immunosuppressant drug, tacrolimus, appeared on the market as a superior alternative to ciclosporin. In the two decades since, intestine transplant efforts have improved tremendously in both number and outcomes.
The small intestine contains a trace amount of microorganisms due to the proximity and influence of the stomach. Gram-positive cocci and rod-shaped bacteria are the predominant microorganisms found in the small intestine. However, in the distal portion of the small intestine alkaline conditions support gram-negative bacteria of the "Enterobacteriaceae". The bacterial flora of the small intestine aid in a wide range of intestinal functions. The bacterial flora provide regulatory signals that enable the development and utility of the gut. Overgrowth of bacteria in the small intestine can lead to intestinal failure. In addition the large intestine contains the largest bacterial ecosystem in the human body. About 99% of the large intestine and feces flora are made up of obligate anaerobes such as "Bacteroides" and "Bifidobacterium." Factors that disrupt the microorganism population of the large intestine include antibiotics, stress, and parasites.
A gastrojejunostomy or GJ feeding tube is a combination device that includes access to both the stomach and the jejunum, or middle part of the small intestine. Typical tubes are placed in a G-tube site or stoma, with a narrower long tube continuing through the stomach and into the small intestine. The GJ-tube is used widely in individuals with severe gastric motility, high risk of aspiration, or an inability to feed into the stomach. It allows the stomach to be continually vented or drained while simultaneously feeding into the small intestine. GJ-tubes are typically placed by an interventional radiologist in a hospital setting. The primary complication of a GJ-tube is migration of the long portion of the tube out of the intestine and back into the stomach.
As a result of its slow digestion, isomaltulose reaches more distally in the human small intestine than does sucrose, as evidenced by their different incretin hormones responses. The incretin hormone glucose-dependent insulinotropic polypeptide (GIP) is secreted from the earlier (proximal) part of the small intestine in lower amounts after isomaltulose than for sucrose ingestion, whereas the incretin hormone glucagon-like peptide-1 (GLP-1) is secreted from a later (distal) part of the small intestine in higher amounts with isomaltulose compared with sucrose.
Little research is conducted on these cancers due to their relative rarity when compared to the more common colorectal cancers. APC-min mice which carry a gene deficiency corresponding to that of humans with FAP also go on to develop small intestinal tumors, though humans do not.
There is no small intestine as such in non-teleost fish, such as sharks, sturgeons, and lungfish. Instead, the digestive part of the gut forms a spiral intestine, connecting the stomach to the rectum. In this type of gut, the intestine itself is relatively straight, but has a long fold running along the inner surface in a spiral fashion, sometimes for dozens of turns. This valve greatly increases both the surface area and the effective length of the intestine. The lining of the spiral intestine is similar to that of the small intestine in teleosts and non-mammalian tetrapods. In lampreys, the spiral valve is extremely small, possibly because their diet requires little digestion. Hagfish have no spiral valve at all, with digestion occurring for almost the entire length of the intestine, which is not subdivided into different regions.
In mammals copper is absorbed in the stomach and small intestine, although there appear to be differences among species with respect to the site of maximal absorption. Copper is absorbed from the stomach and duodenum in rats and from the lower small intestine in hamsters. The site of maximal copper absorption is not known for humans, but is assumed to be the stomach and upper intestine because of the rapid appearance of Cu64 in the plasma after oral administration.
The idea that a SIBO test should be several hours long and that distal overgrowth is important is wrong and is not supported by the scientific literature. The optimal testing is 1 hour. Small intestinal bacterial overgrowth (SIBO) occurs as a result of excessive numbers of bacteria inhabiting the proximal small intestine. Bacterial concentrations greater than 10 organisms per milliliter is diagnostic for SIBO. We know bacteria are colonizing the proximal and not the distal small intestine for several reasons. First, the gold standard method for detection of SIBO is jejunal aspirates. Intestinal fluid of the proximal intestine is sampled, not distal intestinal fluid. Secondly, the consequences of SIBO are the result of competition between bacteria and the human host for ingested nutrients in the intestine. Various functional consequences of bacterial infiltration cause enterocyte damage in the jejunum such as diminished disaccharidase activity, fat malabsorption, decreased amino acid transport and decreased vitamin B absorption. Thus, detection of proximal bacterial overgrowth is critical.
The small intestine is where most chemical digestion takes place. Many of the digestive enzymes that act in the small intestine are secreted by the pancreas and liver and enter the small intestine via the pancreatic duct. Pancreatic enzymes and bile from the gallbladder enter the small intestine in response to the hormone cholecystokinin, which is produced in the small intestine in response to the presence of nutrients. Secretin, another hormone produced in the small intestine, causes additional effects on the pancreas, where it promotes the release of bicarbonate into the duodenum in order to neutralize the potentially harmful acid coming from the stomach.