How long is the human small intestine?
Gastrointestinal tract
The small intestine begins at the duodenum and is a tubular structure, usually between 6 and 7 m long. Its mucosal area in an adult human is about 30 m. Its main function is to absorb the products of digestion (including carbohydrates, proteins, lipids, and vitamins) into the bloodstream. There are three major divisions:
Large intestine
The length of the adult human male colon is 65 inches or 166 cm (range of 80 to 313 cm), on average, for females it is 155 cm (range of 80 to 214 cm).
Ileum
The ileum is the short termi of the small intestine and the connection to the large intestine. It is suspended by the caudal part of the mesentery (mesoileum) and is attached, in addition, to the cecum by the ileocecal fold. The ileum terminates at the cecocolic junction of the large intestine forming the ileal orifice. In the dog the ileal orifice is located at the level of the first or second lumbar vertebra, in the ox in the level of the fourth lumbar vertebrae, in the sheep and goat at the level of the caudal point of the costal arch. By active muscular contraction of the ileum, and closure of the ileal opening as a result of engorgement, the ileum prevents the backflow of ingesta and the equalization of pressure between jejunum and the base of the cecum. Disturbance of this sensitive balance is not uncommon and is one of the causes of colic in horses. During any intestinal surgery, for instance, during appendectomy, distal 2 feet of ileum should be checked for the presence of Meckel's diverticulum.
Intestine transplantation
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.
Cervix
The cervix or cervix uteri ("") is the lower part of the uterus in the human female reproductive system. The cervix is usually 2 to 3 cm long (~1 inch) and roughly cylindrical in shape, which changes during pregnancy. The narrow, central cervical canal runs along its entire length, connecting the uterine cavity and the lumen of the vagina. The opening into the uterus is called the internal os, and the opening into the vagina is called the external os. The lower part of the cervix, known as the vaginal portion of the cervix (or ectocervix), bulges into the top of the vagina. The cervix has been documented anatomically since at least the time of Hippocrates, over 2,000 years ago.
Large intestine
The taenia coli run the length of the large intestine. Because the taenia coli are shorter than the large bowel itself, the colon becomes "sacculated", forming the haustra of the colon which are the shelf-like intraluminal projections.
Esophagus
The esophagus (American English) or oesophagus (British English) (), commonly known as the food pipe or gullet (gut), is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the stomach. The esophagus is a fibromuscular tube, about 25 centimetres long in adults, which travels behind the trachea and heart, passes through the diaphragm and empties into the uppermost region of the stomach. During swallowing, the epiglottis tilts backwards to prevent food from going down the larynx and lungs. The word "esophagus" is the Greek word οἰσοφάγος , meaning "gullet".
Small intestine
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.
Small intestine
Absorption of the majority of nutrients takes place in the jejunum, with the following notable exceptions:The small intestine supports the body's immune system. The presence of gut flora appears to contribute positively to the host's immune system. 
Peyer's patches, located within the ileum of the small intestine, are an important part of the digestive tract's local immune system. They are part of the lymphatic system, and provide a site for antigens from potentially harmful bacteria or other microorganisms in the digestive tract to be sampled, and subsequently presented to the immune system.
Crinoid
The mouth descends into a short oesophagus. There is no true stomach, so the oesophagus connects directly to the intestine, which runs in a single loop right around the inside of the calyx. The intestine often includes numerous diverticulae, some of which may be long or branched. The end of the intestine opens into a short muscular rectum. This ascends towards the anus, which projects from a small conical protuberance at the edge of the tegmen.
Small intestine
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.
Large intestine
The colon is the last part of the digestive system. It extracts water and salt from solid wastes before they are eliminated from the body and is the site in which flora-aided (largely bacterial) fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a major role in absorption of foods and nutrients. About 1.5 litres or 45 ounces of water arrives in the colon each day.
Duodenal cancer
The duodenum is the first part of the small intestine. It is located between the stomach and the jejunum. After foods combine with stomach acid, they descend into the duodenum where they mix with bile from the gallbladder and digestive fluid from the pancreas.
Large intestine
In mammals, the colon consists of five sections: the cecum plus the ascending colon, the transverse colon, the descending colon, the sigmoid colon, and the rectum.
Digestion
In the small intestines, the duodenum provides critical pH balancing to activate digestive enzymes. The liver secretes bile into the duodenum to neutralize the acidic conditions from the stomach, and the pancreatic duct empties into the duodenum, adding bicarbonate to neutralize the acidic chyme, thus creating a neutral environment. The mucosal tissue of the small intestines is alkaline with a pH of about 8.5.
Uterus
The uterus is located within the pelvic region immediately behind and almost overlying the bladder, and in front of the sigmoid colon. The human uterus is pear-shaped and about long, broad (side to side), and thick. A typical adult uterus weighs about 60 grams. The uterus can be divided anatomically into four regions: the fundus – the uppermost rounded portion of the uterus, the corpus (body), the cervix, and the cervical canal. The cervix protrudes into the vagina. The uterus is held in position within the pelvis by ligaments, which are called endopelvic fascia. These ligaments include the pubocervical ligaments, transverse cervical ligaments or cardinal ligaments, and the uterosacral ligaments. It is covered by a sheet-like fold of peritoneum, the broad ligament.
From outside to inside, regions of the uterus include:
Fasciolopsis
"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.
Human sexuality
The male genitalia are the penis and the scrotum. The penis provides a passageway for sperm and urine. An average-sized flaccid penis is about in length and in diameter. When erect, the average penis is between to in length and in diameter. The penis's internal structures consist of the shaft, glans, and the root.
Ototrema schildti
"Ototrema schildti" has an aspinose body measuring 346 to 421 μm long and 181 to 253 μm wide. The oral sucker is 55 to 71 μm long and 61 to 79 μm wide. When the ventrolateral papillae are viewed at an oblique angle they become conspicuous. The trematode lacks a prepharynx and the pharynx is 11 to 20 μm long and 22 to 25 μm wide. The ceca do not reach the testes. At midlevel the acetabulum measures 55 to 71 μm in diameter. The equatorial and subspherical testes are 44 to 66 μm in diameter. The curved cirrus sac is 80 to 173 μm long and 33 to 52 μm wide. The cirrus sac ranges from dorsal to reaching or overlapping the acetabulum, extends anteriorly to the cecal bifurcation, and recurves towards the genital pore in front of the acetabulum. The cirrus is often extended with long and sharp spines. The vasa efferentia unite at the base of the cirrus sac to form an internally winding seminal vesicle. The ovoid ovary is 55 to 77 μm long and 40 to 71 μm wide. The ovary has smooth contours and posteriorly tapers towards the oviduct. The seminal recepticale is bipartite and has a long Laurer's canal that rises from the distal ends, extending posteriorly and dorsally. The finely dissected vitellaria are present in lateral fields and do not overlap medially. The vitellaria are in the region between the oral sucker and ceca. The many-coiled uterus fills the posterior section of the body. The genital pore is median and immediately precetabular. The oval and operculate eggs are 18 to 21 μm long and 9 to 11 μm wide. The "V"-shaped bladder is hidden by the many coils of the uterus, and extends to the testes.
Rectum
The rectum is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction, the end of the sigmoid colon, at the level of the third sacral vertebra or the sacral promontory depending upon what definition is used. Its caliber is similar to that of the sigmoid colon at its commencement, but it is dilated near its termination, forming the rectal ampulla. It terminates at the level of the anorectal ring (the level of the puborectalis sling) or the dentate line, again depending upon which definition is used. In humans, the rectum is followed by the anal canal which is about long, before the gastrointestinal tract terminates at the anal verge. The word rectum comes from the Latin " ", meaning "straight intestine".
Ileal interposition
In addition to sleeve gastrectomy procedure, the connection between the stomach and the duodenum is closed off from the level of the second segment of the duodenum. While preserving the last 30 cm part of the small intestine, a 170 cm segment of ileum is prepared and connected to the first segment of the duodenum, which is at the end of the stomach. The other end of the ileum segment is connected to the proximal part of the small intestine. Thus, distal part of the small intestine is ‘’interposed’’ between proximal part of the small intestine and the stomach. Since duodenum and the proximal part of the small intestine is disabled, a partial bypass is in question. Patients who undergo this operation achieve better weight and blood sugar control, but face anemia (iron deficiency) risk because of the bypass procedure.
Gastrointestinal tract
The gastrointestinal tract forms an important part of the immune system. The surface area of the digestive tract is estimated to be about 32 square meters, or about half a badminton court. With such a large exposure (more than three times larger than the exposed surface of the skin), these immune components function to prevent pathogens from entering the blood and lymph circulatory systems. Fundamental components of this protection are provided by the intestinal mucosal barrier which is composed of physical, biochemical, and immune elements elaborated by the intestinal mucosa. Microorganisms also are kept at bay by an extensive immune system comprising the gut-associated lymphoid tissue (GALT)
Gallstone ileus
First described by Thomas Bartholin in 1654, gallstone ileus is a rare form of small bowel obstruction caused by an impaction of a gallstone within the lumen (small opening) of the small intestine. Such a gallstone enters the bowel via a cholecysto-enteric fistula. The presence of large stones, >2.5 cm in diameter, within the gallbladder are thought to predispose to fistula formation by gradual erosion through the gallbladder fundus. Once a fistula has formed, a stone may travel from the gallbladder into the bowel and become lodged almost anywhere along the GI tract. Obstruction occurs most commonly at the near the distal ileum, within 60 cm proximally to the ileocecal valve. Rarely, gallstone ileus may recur if the underlying fistula is not treated.
Esophagitis
Esophagitis can be asymptomatic; or can cause epigastric and/or substernal burning pain, especially when lying down or straining; and can make swallowing difficult (dysphagia). The most common cause of esophagitis is the reverse flow of acid from the stomach into the lower esophagus: gastroesophageal reflux disease (GERD). 
The esophagus is a muscular tube made of both voluntary and involuntary muscles. It is responsible for peristalsis of food. It is about 8 inches long and passes through the diaphragm before entering the stomach. The esophagus is made up of four layers: from the inside out, they are the mucosa, submucosa, muscularis externa, and the serosa. The mucosa, the inner most layer and lining of the esophagus, is composed of stratified squamous epithelium, lamina propria, and muscularis mucosae. At the end of the esophagus is the lower esophageal sphincter, which normally prevents stomach acid from enteringthe esophagus.
Human digestive system
Peristalsis is the rhythmic contraction of muscles that begins in the esophagus and continues along the wall of the stomach and the rest of the gastrointestinal tract. This initially results in the production of chyme which when fully broken down in the small intestine is absorbed as chyle into the lymphatic system. Most of the digestion of food takes place in the small intestine. Water and some minerals are reabsorbed back into the blood in the colon of the large intestine. The waste products of digestion (feces) are defecated from the anus via the rectum.
Retroperistalsis
In the small intestine, local stimulation of the intestinal smooth muscle by the presence of food particles causes contractions that tend to travel from the stimulated point in both directions. Under normal circumstances, the progress of the contractions in an oral direction is quickly inhibited, while the contractions travelling away from the mouth tend to persist. If the intestine is paralyzed by applying such drugs as nicotine or cocaine to the intestinal wall, the contractions initiated by local stimulations travel equally well in both directions. Ordinarily, peristaltic waves appear in the small intestine at irregular intervals and travel for varying distances; some travel only a few inches, others a few feet. They serve to expose food to the intestinal wall for absorption and to move it forward.
Paryphanta busbyi
The kidney is shortly tongue-shaped, in length less than twice its breadth, about half the length of the lung, and about one and a half times the length of the pericardium; the latter has the usual position on the left margin of the kidney. The ureter continues around the right margin of the kidney, follows the posterior limit of the lung, and opens close to the intestine. From this point the intestine, or rectum, forms a long straight tube. There is a well-marked ridge on the pulmonary wall less than 3 mm. from the side of the rectum, and the narrow area thus defined appears to be the open continuation of the ureter. The above-mentioned ridge examined in section proves to be tubular; it continues into the tissue of the mantle, and appears to unite with the blood-sinus contained therein. The venation of the lung, with the exception of the great pulmonary vein, is very indistinct. This vein runs direct to the auricle, is of considerable breadth, and has an undulating, almost convolute, appearance. On approaching the pneumostome it forms several branches, and the latter, with their accompanying afferent vessels, are fairly well indicated. The vessels on the rectal side of the lung are minute and very much branched, while on the cardiac side only a few traces may be seen.
Anguina tritici
It is a large nematode, ranging from 3–5 mm in length. Anguina tritici has a three part esophagus and the esophageal glands do not overlap with intestine. The female body tends to be thickened and curved ventrally. It has a short stylet (8-11 µm). Females have one ovary and the vulva located posterior. Males possess small spicules and small bursae or alae.
Large intestine (Chinese medicine)
The large intestine (Chinese: 大肠/大腸: pinyin: "dà cháng") is one of the "fu" organs stipulated by traditional Chinese medicine (TCM). As distinct from the Western medical concept of large intestine, this concept from TCM is more a way of describing a set of interrelated parts than an anatomical organ. It is a functionally defined entity and not equivalent to the anatomical organ of the same name.
Stomach
In adult humans, the stomach has a relaxed, near empty volume of about 75 millilitres. Because it is a organ, it normally expands to hold about one litre of food. The stomach of a newborn human baby will only be able to retain about 30 millilitres.
Human digestive system
The stomach is a distensible organ and can normally expand to hold about one litre of food. This expansion is enabled by a series of gastric folds in the inner walls of the stomach. The stomach of a newborn baby will only be able to expand to retain about 30 ml.
Pinworm (parasite)
The life cycle begins with eggs being ingested. The eggs hatch in the duodenum (i.e., first part of the small intestine). The emerging pinworm larvae grow rapidly to a size of 140 to 150 μm, and migrate through the small intestine towards the colon. During this migration, they moult twice and become adults. Females survive for 5 to 13 weeks, and males about 7 weeks. The male and female pinworms mate in the ileum (i.e., last part of the small intestine), whereafter the male pinworms usually die, and are passed out with stool. The gravid female pinworms settle in the ileum, caecum (i.e., beginning of the large intestine), appendix and ascending colon, where they attach themselves to the mucosa and ingest colonic contents.
Excretory system
The large intestine's main function is to transport food particles through the body and expel the indigestible parts at the other end, but it also collects waste from throughout the body. The typical brown colour of mammal waste is due to bilirubin, a breakdown product of normal heme catabolism. The lower part of the large intestine also extracts any remaining usable water and then removes solid waste. At about 10 feet long in humans, it transports the wastes through the tubes to be excreted.
Small intestine
Food from the stomach is allowed into the duodenum through the pylorus by a muscle called the pyloric sphincter.
Large intestine
The average inner diameter of sections of the colon in centimeters (with ranges in parentheses) are cecum 8.7 (8.0-10.5), ascending colon 6.6 (6.0-7.0), transverse colon 5.8 (5.0-6.5), descending/sigmoid colon 6.3 (6.0-6.8) and rectum near rectal/sigmoid junction 5.7 (4.5-7.5).
Human digestive system
In the large intestine, the passage of the digesting food in the colon is a lot slower, taking from 12 to 50 hours until it is removed by defecation. The colon mainly serves as a site for the fermentation of digestible matter by the gut flora. The time taken varies considerably between individuals. The remaining semi-solid waste is termed feces and is removed by the coordinated contractions of the intestinal walls, termed peristalsis, which propels the excreta forward to reach the rectum and exit via defecation from the anus. The wall has an outer layer of longitudinal muscles, the taeniae coli, and an inner layer of circular muscles. The circular muscle keeps the material moving forward and also prevents any back flow of waste. Also of help in the action of peristalsis is the basal electrical rhythm that determines the frequency of contractions. The taeniae coli can be seen and are responsible for the bulges (haustra) present in the colon. Most parts of the GI tract are covered with serous membranes and have a mesentery. Other more muscular parts are lined with adventitia.
Anal sex
The abundance of nerve endings in the anal region and rectum can make anal sex pleasurable for men or women. The internal and external sphincter muscles control the opening and closing of the anus; these muscles, which are sensitive membranes made up of many nerve endings, facilitate pleasure or pain during anal sex. The "Human Sexuality: An Encyclopedia" states that "the inner third of the anal canal is less sensitive to touch than the outer two-thirds, but is more sensitive to pressure" and that "the rectum is a curved tube about eight or nine inches long and has the capacity, like the anus, to expand".
Large intestine
The descending colon is the part of the colon from the splenic flexure to the beginning of the sigmoid colon. One function of the descending colon in the digestive system is to store feces that will be emptied into the rectum. It is retroperitoneal in two-thirds of humans. In the other third, it has a (usually short) mesentery. The arterial supply comes via the left colic artery. The descending colon is also called the "distal gut", as it is further along the gastrointestinal tract than the proximal gut. Gut flora are very dense in this region.
Ear canal
The ear canal (external acoustic meatus, external auditory meatus, EAM; ) is a tube running from the outer ear to the middle ear. The adult human ear canal extends from the pinna to the eardrum and is about in length and in diameter.
Stapes
The stapes is the third bone of the three ossicles in the middle ear. The stapes is a stirrup-shaped bone, and the smallest in the human body. It rests on the oval window, to which it is connected by an annular ligament. The stapes is described as having a base, resting on the oval window, as well as a head that articulates with the incus. These are connected by anterior and posterior limbs (). The stapes articulates with the incus through the incudostapedial joint. The stapes is the smallest bone in the human body, and measures roughly 3 x 2.5mm, greater along the head-base span.
Pit latrine
A pit latrine, also known as pit toilet or long drop, is a type of toilet that collects human feces in a hole in the ground. Urine and feces enter the pit through a drop hole in the floor, which might be connected to a toilet seat or squatting pan for user comfort. Pit latrines can be built to function without water (dry toilet) or they can have a water seal (pour-flush pit latrine). When properly built and maintained, pit latrines can decrease the spread of disease by reducing the amount of human feces in the environment from open defecation. This decreases the transfer of pathogens between feces and food by flies. These pathogens are major causes of infectious diarrhea and intestinal worm infections. Infectious diarrhea resulted in about 700,000 deaths in children under five years old in 2011 and 250 million lost school days. Pit latrines are a low cost method of separating feces from people.
A pit latrine generally consists of three major parts: a hole in the ground, a concrete slab or floor with a small hole, and a shelter. The shelter is also called an outhouse. The pit is typically at least three meters (10 feet) deep and one meter (3.2 feet) across. The hole in the slab should not be larger than 25 centimeters (9.8 inches) to prevent children falling in. Light should be prevented from entering the pit to reduce access by flies. This may require the use of a lid to cover the hole in the floor when not in use. The World Health Organization recommends the pits are built a reasonable distance from the house, balancing issues of easy access versus that of smell. The distance from water wells and surface water should be at least 10 meters (32 feet) to decrease the risk of groundwater pollution. When the pit fills to within 0.5 meters (1.6 feet) of the top, it should be either emptied or a new pit constructed and the shelter moved or re-built at the new location. Fecal sludge management involves emptying pits as well as transporting, treating and using the collected fecal sludge. If this is not carried out properly, water pollution and public health risks can occur.
A basic pit latrine can be improved in a number of ways. One includes adding a ventilation pipe from the pit to above the structure. This improves airflow and decreases the smell of the toilet. It also can reduce flies when the top of the pipe is covered with mesh (usually made out of fiberglass). In these types of toilets a lid need not be used to cover the hole in the floor. Other possible improvements include a floor constructed so fluid drains into the hole and a reinforcement of the upper part of the pit with bricks, blocks, or cement rings to improve stability. In developing countries the cost of a simple pit toilet is typically between US$25 and $60. Recurring expenditure costs are between US$1.5 and $4 per person per year for a traditional pit latrine, and up to three times higher for a pour flush pit latrine (without the costs of emptying). 
As of 2013 pit latrines are used by an estimated 1.77 billion people, mostly in developing countries. About 892 million people (12 percent of the global population), practiced open defecation in 2016, mostly because they have no toilets. Southern Asia and Sub-Saharan Africa have the lowest access to toilets. The Indian government has been running a campaign called "Swachh Bharat Abhiyan" (Clean India Mission in English) since 2014 in order to eliminate open defecation by convincing people in rural areas to purchase, construct and use toilets, mainly pit latrines. It is estimated that 85 million pit latrines have been built due to that campaign as of 2018. Another example from India is the "No Toilet, No Bride" campaign which promotes toilet uptake by encouraging women to refuse to marry men who do not own a toilet.
Schistosoma mansoni
Schistosomes, unlike other trematodes, are long and cylindrical worms. The male "S. mansoni" is approximately 1 cm long (0.6–1.1 cm) and is 0.1 cm wide. It is white, and it has a funnel-shaped oral sucker at its anterior end followed by a second pediculated ventral sucker. The external part of the worm is composed of a double bilayer, which is continuously renewed as the outer layer, known as the membranocalyx, and is shed continuously. The tegument bears a large number of small tubercules. The suckers have small thorns in their inner part as well as in the buttons around them. The male genital apparatus is composed of 6 to 9 testicular masses, situated dorsally. There is one deferent canal beginning at each testicle, which is connected to a single deferent that dilates into a reservatory, the seminal vesicle, located at the beginning of the gynaecophoric canal. The copula happens through the coaptation of the male and female genital orifices.
Kidney dish
Generally, the volume of a pulp kidney dish (or "vomit dish") is 700 ml. Its length is 25 cm-26 cm, its width 11 cm. Each year more than 100 million pulp kidney dishes are used in hospital or family care.
Small intestine cancer
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.
Aonchotheca forresteri
At 6.8 to 9.2 (7.7) mm, males are only about half as long as females. Their maximum width is 34 to 42 (37) μm. The length of the esophagus is 2.3 to 3.0 (2.6) mm, of which the muscular pharynx makes up 260 to 315 (273) μm, and is lined by 35 to 42 (37) stichocytes. The back region of the worm is 4.5 to 6.2 (5.1) mm long. The back, or rectal, opening of the digestive tube is located near the end of the worm, and the length of the cloaca is 530 to 576 (550) μm. Near the back end, there are two alae (ridges) at the sides (laterally), which are 40 to 55 (46) μm long; these are located at 10 to 15 μm from another, small ala at the tip. In "A. putorii", the lateral alae are much longer and reach the ala at the tip. The spicule, a spikelike structure that functions in reproduction, is curved at the tip and hardened and has a length of 380 to 426 (406) μm. It is smaller than that of the similar "A. tamiasstriati" from North American chipmunks and larger than that of "A. murissylvatici" from various North American and European small rodents, but about as long as that of "A. putorii", which however lacks the curved tip.
Draeden
A draeden's rarely-seen true appearance is a cluster of about forty tubular strands, all symmetrically attached at a central node. Each strand has a mouth at its end, and opens upon a digestive passage that leads to the central node. The node is spherical and ridged, resembling a human brain, and is the creature's equivalent of a stomach. It contains several boulders to aid digestion. A draeden's nervous system spans its entire body. The creatures's total length varies from 19 to 38 miles, tip to tip. The central node usually comprises one-tenth of the creature's total diameter. Draeden usually appear to other creatures as the most deadly thing imaginable to those creatures.
Gastrodiscoides
It is a large fluke, vase-shaped, and bright-pink in colour. In average it measures 5–8 mm long and 3–5 mm wide. The disc-shaped body is divisible into anterior conical and posterior discoidal regions. The anterior region is a conical projection bearing a prominent oral sucker. The posterior portion is relatively broad, up to 8 mm wide, discoidal, and ventrally excavated. It is an amphistome worm such that the ventral sucker is close to the posterior end. The body covering, called a tegument, is smooth in appearance, but contains a fine structure in a series of concentric folds bearing numerous tightly packed tubercles. Ventral surface contains a specialised region of the tegument. Ciliated and non-ciliated papillae are arranged around the oral sucker. The incomplete alimentary canal consists of a pair of lateral pouches arising from the oral sucker and a slightly tortuous pharyngeal tube, which bifurcates into two gut cæca. The large excretory bladder is in the middle, behind the ventral sucker. The species, being hermaphrodite, has both male and female reproductive systems, arranged in the posterior region. The testes lie in alongside the bifurcation of the cæca, and a common genital pore is on the cone just anterior to the bifurcation. The oval-shaped ovary lies just posterior to the testes in the middle, and the loosely coiled uterus opens to the genital pore. Vitelline glands are scattered around the cæca.
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. 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 mammals the duodenum may be the principal site for iron absorption.
Short bowel syndrome
Short bowel syndrome (SBS, or simply short gut) is a malabsorption disorder caused by a lack of functional small intestine. The primary symptom is diarrhea, which can result in dehydration, malnutrition, and weight loss. Other symptoms may include bloating, heartburn, feeling tired, lactose intolerance, and foul smelling stool. Complications can include anemia and kidney stones.
Most cases are due to the surgical removal of a large portion of the small intestine. This is most often required due to Crohn's disease in adults and necrotising enterocolitis in young children. Other causes include damage to the small intestine from other means and being born with an abnormally short intestine. It usually does not develop until less than of the normally small intestine remains.
Treatment may include a specific diet, medications, or surgery. The diet may include slightly salty and slightly sweet liquids, vitamin and mineral supplements, small frequent meals, and the avoidance of high fat food. Occasionally nutrients need to be given through an intravenous line, known as parenteral nutrition. Medications used may include antibiotics, antacids, loperamide, teduglutide, and growth hormone. Different types of surgery, including an intestinal transplant, may help some people.
Short bowel syndrome newly occurs in about three per million people each year. There are estimated to be about 15,000 people with the condition in the United States. It is classified as a rare disease by the European Medicines Agency. Outcomes depend on the amount of bowel remaining and whether or not the small bowel remains connected with the large bowel.
Large intestine
The cecum – the first part of the large intestine
Small intestine (Chinese medicine)
Transporting point of SI: Urinary Bladder 27. Conception vessel – anterior midline from perineum to lower lip. This is also the Alarm point for the SI which is called "Gateway to the Source"(guan yuan). Governing vessel is from perineum, to spine to crown of head down to upper lip.
Microcotyle mouwoi
The description by Ishii and Sawada in 1938 includes the following:
"Elongated body 2.2-3.2 mm long and 0.378- 0.55mm wide. Two oval anterior suckers lies at the anterior end of the body.The haptor has 28-30 clamps. The mouth, which opens at the anterior end of the body leads into the pharynx. The pharynx lies in contact with two anterior suckers. The short oesophagus divides into two intestinal canals, which run to near the end of the haptor.
Male organs comprises testicular follicles, longitudinally on the median line at the posterior portion of the body. The vas deferens from testes winds on forward along the ovary, into the genital opening, which has four long spines. The female organs includes the elongated ovary with the slender end posterior and the broad anterior part to the right. The oviduct receives the vitelloduct and becomes the slender ootype. The uterus proceeds forward to the genital opening. The vitellaria fill up the lateral body from a little behind the genital opening to the end of the haptor. The vaginal opening lies median, dorsal and behind the genital opening."
Penis
As with any other bodily attribute, the length and girth of the penis can be highly variable between mammals of different species. In many mammals, the size of a flaccid penis is smaller than its erect size. In the realm of absolute size, the smallest vertebrate penis belongs to the common shrew (5 mm or 0.2 inches).
Large intestine
As estimated from the image in panel A, there are about 100 colonic crypts per square millimeter of the colonic epithelium. Since the average length of the human colon is 160.5 cm and the average inner circumference of the colon is 6.2 cm, the inner surface epithelial area of the human colon has an average area of about 995 sq cm, which includes 9,950,000 (close to 10 million) crypts.
Chitterlings
Both large and small intestine (typically pig) is eaten throughout China. Large intestine is called "feichang", literally "fat intestine" because it is fatty. Small intestine is called "zhufenchang", literally "pig powder intestine" because it contains a white, pasty or powdery substance. The character "zhu" or "pig" is added at the beginning to disambiguate. This is because, in Cantonese cuisine, there is a dish called "chang fen" which uses intestine-shaped noodles.
Fish physiology
The small intestine is the part of the digestive tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In fish, the divisions of the small intestine are not clear, and the terms "anterior" or "proximal" intestine may be used instead of duodenum. The small intestine is found in all teleosts, although its form and length vary enormously between species. In teleosts, it 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.
Large intestine
The large intestine houses over 700 species of bacteria that perform a variety of functions, as well as fungi, protozoa, and archaea. Species diversity varies by geography and diet. The microbes in a human distal gut often number in the vicinity of 100 trillion, and can weigh around 200 grams (0.44 pounds). This mass of mostly symbiotic microbes has recently been called the latest human organ to be "discovered" or in other words, the "forgotten organ".
Spongy urethra
The spongy urethra runs along the length of the penis on its ventral (underneath) surface. It is about 15–16 cm in length, and travels through the corpus spongiosum. The ducts from the urethral gland (gland of Littre) enter here. The openings of the bulbourethral glands are also found here. Some textbooks will subdivide the spongy urethra into two parts, the bulbous and pendulous urethra. The urethral lumen runs effectively parallel to the penis, except at the narrowest point, the external urethral meatus, where it is vertical. This produces a spiral stream of urine and has the effect of cleaning the external urethral meatus. The lack of an equivalent mechanism in the female urethra partly explains why urinary tract infections occur so much more frequently in females.
Renal ultrasonography
The kidney is divided into parenchyma and renal sinus. The renal sinus is hyperechoic and is composed of calyces, the renal pelvis, fat and the major intrarenal vessels. In the normal kidney, the urinary collecting system in the renal sinus is not visible, but it creates a heteroechoic appearance with the interposed fat and vessels. The parenchyma is more hypoechoic and homogenous and is divided into the outermost cortex and the innermost and slightly less echogenic medullary pyramids. Between the pyramids are the cortical infoldings, called columns of Bertin (Figure 1). In the pediatric patient, it is easier to differentiate the hypoechoic medullar pyramids from the more echogenic peripheral zone of the cortex in the parenchyma rim, as well as the columns of Bertin (Figure 2).
The length of the adult kidney is normally 10–12 cm, and the right kidney is often slightly longer than the left kidney. The adult kidney size is variable due to the correlation with body height and age; however, normograms for pediatric kidney size are available.
Small intestine
The three sections of the small intestine look similar to each other at a microscopic level, but there are some important differences. The parts of the intestine are as follows:
Equine anatomy
The horse’s small intestine is long and holds . This is the major digestive organ, and where most nutrients are absorbed. It has three parts, the duodenum, jejunum and ileum. The majority of digestion occurs in the duodenum while the majority of absorption occurs in the jejunum. Bile from the liver aids in digesting fats in the duodenum combined with enzymes from the pancreas and small intestine. Horses do not have a gall bladder, so bile flows constantly. Most food is digested and absorbed into the bloodstream from the small intestine, including proteins, simple carbohydrate, fats, and vitamins A, D, . Any remaining liquids and roughage move into the large intestine.
Ileostomy
A patient must have an adequate length of small intestine to be considered a potential candidate.
External anal sphincter
The external anal sphincter measures about 8 to 10 cm in length, from its anterior to its posterior extremity, and is about 2.5 cm opposite the anus, when defecation occurs the sphincter muscle retracts.
Anguina agrostis
The lip region is slightly offset (3-4 µm high) and the nematode has a very short stylet (10 µm). "A. agrostis" has a three-part esophagus. The procorpus is cylindrical with a swelling near its midsection. The metacorpus is ovoid in shape and the isthmus is long and narrow. The postcorpus has three glands and is highly developed, but does not overlap the intestine. On average, infective juveniles (J2) measure 530 µm and dauer juveniles measure 760 µm; the increase in size is due to feeding and the formation of lipid droplets or storage bodies. Females range from 1.5-2.7 mm in length, are curved ventrally, and are swollen. The vulva is located near the posterior end and one ovary is present. Males are smaller (1.1-1.7 mm in length), are not as swollen, and have a small bursae that extends subterminally. One testis is present.
Echinococcus granulosus
Echinococcus granulosus, also called the hydatid worm, hyper tape-worm or dog tapeworm, is a cyclophyllid cestode that dwells in the small intestine of canids as an adult, but which has important intermediate hosts such as livestock and humans, where it causes cystic echinococcosis, also known as hydatid disease. The adult tapeworm ranges in length from 3 mm to 6 mm and has three proglottids ("segments") when intact—an immature proglottid, mature proglottid and a gravid proglottid. The average number of eggs per gravid proglottid is 823. Like all cyclophyllideans, "E. granulosus" has four suckers on its scolex ("head"), and "E. granulosus" also has a rostellum with hooks. Several strains of "E. granulosus" have been identified, and all but two are noted to be infective in humans.
Human skin
In terms of surface area, the skin is the second largest organ in the human body (the inside of the small intestine is 15 to 20 times larger). For the average adult human, the skin has a surface area of between 1.5-2.0 square meters (16.1-21.5 sq ft.). The thickness of the skin varies considerably over all parts of the body, and between men and women and the young and the old. An example is the skin on the forearm which is on average 1.3 mm in the male and 1.26 mm in the female. The average square inch (6.5 cm²) of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than 1,000 nerve endings. The average human skin cell is about 30 micrometers in diameter, but there are variants. A skin cell usually ranges from 25-40 micrometers (squared), depending on a variety of factors.
Duodenal switch
The common channel is the portion of small intestine, usually 75-150 centimeters long, in which the contents of the digestive path mix with the bile from the biliopancreatic loop before emptying into the large intestine. The objective of this arrangement is to reduce the amount of time the body has to capture calories from food in the small intestine and to selectively limit the absorption of fat. As a result, following surgery, these patients absorb only approximately 20% of the fat they intake.
Inguinal canal
The inguinal canals are situated just above the medial half of the inguinal ligament. In both sexes the canals transmit the ilioinguinal nerves. The canals are approximately 3.75 to 4 cm long. , angled anteroinferiorly and medially.
Cat anatomy
Food then moves on to the jejunum. This is the most nutrient absorptive section of the small intestine. The liver regulates the level of nutrients absorbed into the blood system from the small intestine. From the jejunum, whatever food that has not been absorbed is sent to the ileum which connects to the large intestine. The first part of the large intestine is the cecum and the second portion is the colon. The large intestine reabsorbs water and forms fecal matter.
Gastrointestinal tract
The large intestine also called the colon, consists of the cecum, rectum, and anal canal. It also includes the appendix, which is attached to the cecum. The colon is further divided into:
The main function of the large intestine is to absorb water.
The area of the large intestinal mucosa of an adult human is about 2 m.
Trachea
The trachea is no more than 4mm diameter during the first year of life, expanding to its adult diameter by late childhood. The trachea is more mobile and of more variable length, deeper, and smaller in children.
Large intestine
The colon is the largest portion of the large intestine, so many mentions of the large intestine and colon overlap in meaning whenever anatomic precision is not the focus. Most sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal. Some other sources exclude the anal canal.
Small intestine
The small intestine or small bowel is the part of the gastrointestinal tract between the stomach and the large intestine, and is where most of the end absorption of food takes place. The small intestine has three distinct regions – the duodenum, jejunum, and ileum. The duodenum is the shortest part of the small intestine and is where preparation for absorption begins. It also receives bile and pancreatic juice through the pancreatic duct, controlled by the sphincter of Oddi. The primary function of the small intestine is the absorption of nutrients and minerals from food, using small finger-like protrusions called villi.
Manatee
Like the horse, the manatee has a simple stomach, but a large cecum, in which it can digest tough plant matter. Generally, the intestines are about 45 meters, unusually long for an animal of the manatee's size.
Sigmoid colon
The sigmoid colon (pelvic colon) is the part of the large intestine that is closest to the rectum and anus. It forms a loop that averages about 35–40 cm (13.78-15.75 in) in length. The loop is typically shaped like a Greek letter sigma (ς) or Latin letter S (thus "sigma" + "-oid"). This part of the colon normally lies within the pelvis, but on account of its freedom of movement it is liable to be displaced into the abdominal cavity.
Pinniped
Pinnipeds have a simple stomach that is similar in structure to terrestrial carnivores. Most species have neither a cecum nor a clear demarcation between the small and large intestines; the large intestine is comparatively short and only slightly wider than the latter. Small intestine lengths range from 8 times (California sea lion) to 25 times (elephant seal) the body length. The length of the intestine may be an adaptation to frequent deep diving, as the increased volume of the digestive tract serves as an extended storage compartment for partially digested food during submersion. Pinnipeds do not have an appendix. As in most marine mammals, the kidneys are divided into small lobes and can effectively absorb water and filter out excess salt.
Prostate cancer
The prostate is a part of the male reproductive system that helps make and store seminal fluid. In adult men, a typical prostate is about 3 centimeters long and weighs about 20 grams. It is located in the pelvis, under the urinary bladder and in front of the rectum. The prostate surrounds part of the urethra, the tube that carries urine from the bladder during urination and semen during ejaculation. Because of its location, prostate diseases often affect urination, ejaculation, and rarely defecation. The prostate contains many small glands which make about 20% of the fluid constituting semen. In prostate cancer, the cells of these prostate glands mutate into cancer cells. The prostate glands require male hormones, known as androgens, to work properly. Androgens include testosterone, which is made in the testes; dehydroepiandrosterone, made in the adrenal glands; and dihydrotestosterone, which is converted from testosterone within the prostate itself. Androgens are also responsible for secondary sex characteristics such as facial hair and increased muscle mass.
Gastrointestinal tract
The lower gastrointestinal tract includes most of the small intestine and all of the large intestine. In human anatomy, the intestine (bowel, or gut. Greek: éntera) is the segment of the gastrointestinal tract extending from the pyloric sphincter of the stomach to the anus and, as in other mammals, consists of two segments, the small intestine and the large intestine. In humans, the small intestine is further subdivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the, cecum, ascending, transverse, descending and sigmoid colon, rectum, and anal canal.
Pancreas
The pancreas is an organ that in humans lies in the upper left part of the abdomen. It is found behind the stomach. The pancreas is about long.
Human digestive system
The largest structure of the digestive system is the gastrointestinal tract (GI tract). This starts at the mouth and ends at the anus, covering a distance of about nine (9) metres.
Ureteric stent
A ureteral stent (pronounced you-REE-ter-ul), or ureteric stent, is a thin tube inserted into the ureter to prevent or treat obstruction of the urine flow from the kidney. The length of the stents used in adult patients varies between 24 and 30 cm. Additionally, stents come in differing diameters or gauges, to fit different size ureters. The stent is usually inserted with the aid of a cystoscope. One or both ends of the stent may be coiled to prevent it from moving out of place; this is called a JJ stent, double J stent or pig-tail stent.
Small intestine
The three major classes of nutrients that undergo digestion are proteins, lipids (fats) and carbohydrates:Digested food is now able to pass into the blood vessels in the wall of the intestine through either diffusion or active transport. The small intestine is the site where most of the nutrients from ingested food are absorbed. The inner wall, or mucosa, of the small intestine is lined with simple columnar epithelial tissue. Structurally, the mucosa is covered in wrinkles or folds called plicae circulares, which are considered permanent features in the wall of the organ. They are distinct from rugae which are considered non-permanent or temporary allowing for distention and contraction. From the plicae circulares project microscopic finger-like pieces of tissue called villi (Latin for "shaggy hair"). The individual epithelial cells also have finger-like projections known as microvilli. The functions of the plicae circulares, the villi, and the microvilli are to increase the amount of surface area available for the absorption of nutrients, and to limit the loss of said nutrients to intestinal fauna.
List of kidney stone formers
Kidney stones can reach exceptional size. In December 2003, a kidney stone weighing 356 g (12.5 oz) was removed from the right kidney of Peter Baulman of Australia. At its widest point, the stone measured 11.86 cm (4.66 in). In 2017, a 2 kg (4.4 lb) stone spanning 20 cm was surgically removed from Abdul Abu Al Hajjar in Kensington, England. As of August 2006, the most kidney stones ever passed naturally was 5,704 by Canadian Donald Winfield. The largest number removed through surgery was 728, during a three-hour operation upon Mangilal Jain of India, on January 27, 2004.
Fictional incidents of kidney stones have been portrayed in the media on several occasions.
Placenta
Placental mammals, such as humans, have a chorioallantoic placenta that forms from the chorion and allantois. In humans, the placenta averages 22 cm (9 inch) in length and 2–2.5 cm (0.8–1 inch) in thickness, with the center being the thickest, and the edges being the thinnest. It typically weighs approximately 500 grams (just over 1 lb). It has a dark reddish-blue or crimson color. It connects to the fetus by an umbilical cord of approximately 55–60 cm (22–24 inch) in length, which contains two umbilical arteries and one umbilical vein. The umbilical cord inserts into the chorionic plate (has an eccentric attachment). Vessels branch out over the surface of the placenta and further divide to form a network covered by a thin layer of cells. This results in the formation of villous tree structures. On the maternal side, these villous tree structures are grouped into lobules called cotyledons. In humans, the placenta usually has a disc shape, but size varies vastly between different mammalian species.
Small intestine (Chinese medicine)
SI Meridian Points (S1-S10):
SI-1 (Shao Ze/Lesser Marsh) : Resuscitates, promotes lactation, opens orifices, clears Heat. 
SI-2 (Qian Gu/Front Valley): Clears Heat, activates the meridian.
SI-3 (Hou Xi/Back Stream): Benefits the neck and back, treats malaria activates the meridian.
SI-4 (Wan Gu/Wrist Bone): Activates and clears the meridian, resolves Damp-Heat.
SI-5 (Yang Gu/Yang Valley): Clears Heat, clears the meridian, reduces swelling.
SI-6 (Yang Lao/Nourishing the Aged): Activates the meridian, benefits the eyes, benefits the shoulder and arm, alleviates pain. 
SI-7 (Zhi Zheng/Branch of the Upright): Activates the meridian, frees obstructions, calms the Shen, clears Heat, alleviates pain. 
SI-8 (Xiao Hai/Small Sea): Activates the meridian, alleviates pain, clears Heat and Damp-Heat.
SI-9 (Jian Zhen/True Shoulder): Activates the meridian, alleviates pain, benefits the shoulder. 
SI-10 (Nao Shu/Upper Arm Shu): Activates the meridian, alleviates pain, benefits the shoulder.https://theory.yinyanghouse.com/acupuncturepoints/smallintestine_meridian_graphic
http://www.sacredlotus.com/go/acupuncture/channel/small_intestine_channel_of_hand_tai_yang
http://www.acatcm.com/small-intestine-meridian-hand-tai-yin-points
Equine nutrition
The small intestine is long and holds to . This is the major digestive organ where 50 to 70 percent of all nutrients are absorbed into the bloodstream. Bile from the liver acts here, combined with enzymes from the pancreas and small intestine itself. Equids do not have a gall bladder, so bile flows constantly, an adaptation to a slow but steady supply of food, and another reason for providing fodder to horses in several small feedings.
Malabsorption
Normally the human gastrointestinal tract digests and absorbs dietary nutrients with remarkable efficiency. A typical Western diet ingested by an adult in one day includes approximately 100 g of fat, 400 g of carbohydrate, 100 g of protein, 2 L of fluid, and the required sodium, potassium, chloride, calcium, vitamins, and other elements. Salivary, gastric, intestinal, hepatic, and pancreatic secretions add an additional 7–8 L of protein-, lipid-, and electrolyte-containing fluid to intestinal contents. This massive load is reduced by the small and large intestines to less than 200 g of stool that contains less than 8 g of fat, 1–2 g of nitrogen, and less than 20 mmol each of Na, K, Cl, HCO, Ca, or Mg.
Small intestine
The jejunum and ileum are suspended in the abdominal cavity by mesentery. The mesentery is part of the peritoneum. Arteries, veins, lymph vessels and nerves travel within the mesentery.
Anal canal
In humans it is approximately 2.5 to 4 cm long, extending from the anorectal junction to the anus. It is directed downwards and backwards. It is surrounded by inner involuntary and outer voluntary sphincters which keep the lumen closed in the form of an anteroposterior slit.
Duodenum
The duodenum precedes the jejunum and ileum and is the shortest part of the small intestine.
Gastrodiscoides
Humans are now considered as the accidental host because humans are not the primary requirement for the life cycle; pigs are recognised as the principal definitive host. Infection causes a helminthic disease called gastrodiscoidiasis. It is a digenetic trematode with a complex life cycle involving asexual reproduction in an intermediate host, presumably aquatic snails, and sexual reproduction in the vertebrate host. As a hermaphrodite, eggs are produced by self-fertilisation and are released along the fæces of the host. Eggs measure ~146 by 66 μm, are rhomboidal in shape, transparent, and green in colour. Each egg contains about 24 vitelline cells and a central unembryonated ovum. Eggs in a wet environment hatch into miracidia in 9–14 days.
Mesentery
The mesentery of the small intestine arises from the root of the mesentery (or mesenteric root) and is the part connected with the structures in front of the vertebral column. The root is narrow, about 15 cm long, 20 cm in width, and is directed obliquely from the duodenojejunal flexure at the left side of the second lumbar vertebra to the right sacroiliac joint. The root of the mesentery extends from the duodenojejunal flexure to the ileocaecal junction. This section of the small intestine is located centrally in the abdominal cavity and lies behind the transverse colon and the greater omentum.
Human digestive system
The cecum is a pouch marking the division between the small intestine and the large intestine. The cecum receives chyme from the last part of the small intestine, the ileum, and connects to the ascending colon of the large intestine. At this junction there is a sphincter or valve, the ileocecal valve which slows the passage of chyme from the ileum, allowing further digestion. It is also the site of the appendix attachment.
Intestinal gland
As estimated from the image in panel A, there are about 100 colonic crypts per square millimeter of the colonic epithelium. The length of the human colon is, on average 160.5 cm (measured from the bottom of the cecum to the colorectal junction) with a range of 80 cm to 313 cm. The average inner circumference of the colon is 6.2 cm. Thus, the inner surface epithelial area of the human colon has an area, on average, of about 995 sq cm, which includes 9,950,000 (close to 10 million) crypts.
Fish anatomy
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.
Bulbourethral gland
The bulbourethral glands are compound tubulo-alveolar glands, each approximately the size of a pea in humans. In chimpanzees, they are not visible during dissection, but can be found on microscopic examination. In boars, they are up to 18 cm long and 5 cm in diameter. They are composed of several lobules held together by a fibrous covering. Each lobule consists of a number of acini, lined by columnar epithelial cells, opening into a duct that joins with the ducts of other lobules to form a single excretory duct. This duct is approximately 2.5 cm long and opens into the bulbar urethra at the base of the penis. The glands gradually diminish in size with advancing age.
Ivan Mackerle
"sausage-like worm over half a metre (20 inches) long, and thick as a man's arm, resembling the intestine of cattle. Its tail is short, as [if] it were cut off, but not tapered. It is difficult to tell its head from its tail because it has no visible eyes, nostrils or mouth. Its colour is dark red, like blood or salami..."
Small intestine
Each villus has a network of capillaries and fine lymphatic vessels called lacteals close to its surface. The epithelial cells of the villi transport nutrients from the lumen of the intestine into these capillaries (amino acids and carbohydrates) and lacteals (lipids). The absorbed substances are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by our body. The material that remains undigested and unabsorbed passes into the large intestine.
Short bowel syndrome
The length of the small intestine can vary greatly, from as short as to as long as . On average it is about . Due to this variation it is recommended that following surgery the amount of bowel remaining be specified rather than the amount removed.
Urinary bladder
The urinary bladder is a hollow muscular organ in humans and some other animals that collects and stores urine from the kidneys before disposal by urination. In the human the bladder is a hollow muscular, and distensible (or elastic) organ, that sits on the pelvic floor. Urine enters the bladder via the ureters and exits via the urethra. The typical human bladder will hold between 300 and (10.14 and ) before the urge to empty occurs, but can hold considerably more.
Large intestine
The colon crypts are shaped like microscopic thick walled test tubes with a central hole down the length of the tube (the crypt lumen). Four tissue sections are shown here, two cut across the long axes of the crypts and two cut parallel to the long axes. In these images the cells have been stained by immunohistochemistry to show a brown-orange color if the cells produce a mitochondrial protein called cytochrome c oxidase subunit I (CCOI). The nuclei of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with haematoxylin. As seen in panels C and D, crypts are about 75 to about 110 cells long. Baker et al. found that the average crypt circumference is 23 cells. Thus, by the images shown here, there are an average of about 1,725 to 2530 cells per colonic crypt. Nooteboom et al. measuring the number of cells in a small number of crypts reported a range of 1500 to 4900 cells per colonic crypt. Cells are produced at the crypt base and migrate upward along the crypt axis before being shed into the colonic lumen days later. There are 5 to 6 stem cells at the bases of the crypts.