WordNet

the part of the small intestine between the jejunum and the cecum
branch of the superior mesenteric artery that supplies the ileum (同)intestinal artery, arteria ileum

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回腸(小腸の下部の1/3の部分)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/07/25 23:27:19」(JST)

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Not to be confused with Ilium.

The ileum /ˈɪliːəm/ is the final 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 posterior intestine or distal intestine may be used instead of ileum.^[2]

The ileum follows the duodenum and jejunum and is separated from the cecum by the ileocecal valve (ICV). In humans, the ileum is about 2–4 m long, and the pH is usually between 7 and 8 (neutral or slightly alkaline).

Function

The function of the ileum is mainly to absorb vitamin B₁₂ and bile salts and whatever products of digestion that were not absorbed by the jejunum. The wall itself is made up of folds, each of which has many tiny finger-like projections known as villi on its surface. In turn, the epithelial cells that line these villi possess even larger numbers of microvilli. Therefore the ileum has an extremely large surface area both for the adsorption (attachment) of enzyme molecules and for the absorption of products of digestion. The DNES (diffuse neuroendocrine system) cells of the ileum secrete various hormones (gastrin, secretin, cholecystokinin) into the blood. Cells in the lining of the ileum secrete the protease and carbohydrase enzymes responsible for the final stages of protein and carbohydrate digestion into the lumen of the intestine. These enzymes are present in the cytoplasm of the epithelial cells.

The villi contain large numbers of capillaries that take the amino acids and glucose produced by digestion to the hepatic portal vein and the liver. Lacteals are small lymph vessels, and are present in villi. They absorb fatty acid and glycerol, the products of fat digestion. Layers of circular and longitudinal smooth muscle enable the digested food to be pushed along the ileum by waves of muscle contractions called peristalsis. The undigested food (waste and water) are sent to the colon.

Differences between jejunum and ileum

There is no line of demarcation between the jejunum and the ileum. There are, however, subtle differences between the two.

The ileum has more fat inside the mesentery than the jejunum
While the length of the intestinal tract contains lymphoid tissue, only the ileum has abundant Peyer's patches, unencapsulated lymphoid nodules that contain large numbers of lymphocytes and other cells of the immune system.

Embryology

In the fetus the ileum is connected to the navel by the vitelline duct. In roughly 2% of humans, this duct fails to close during the first seven weeks after birth, causing a condition called Meckel's diverticulum.

Veterinary anatomy

In veterinary anatomy, the ileum is distinguished from the jejunum by being that portion of the jejunoileum that is connected to the caecum by the ileocecal fold.

The ileum is the short terminal part of the small intestine and forms 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.^[3] 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.

Additional images

Ileum and cecum
Ileo-cecal valve
Inferior ileocecal fossa
Arteries of cecum and vermiform process
Goblet cell in ileum
General structure of the gut wall
Dog Ileum 40X

References

^ Physiology at MCG 6/6ch2/s6ch2_30
^ Guillaume, Jean; Praxis Publishing, Sadasivam Kaushik, Pierre Bergot, Robert Metailler (2001). Nutrition and Feeding of Fish and Crustaceans. Springer. p. 31. ISBN 1-85233-241-7, 9781852332419. http://books.google.com/?id=As0flTZo_EAC&pg=PA31&lpg=PA31&dq=fish+cytology+jejunum+duodenum. Retrieved 2009-01-09.
^ 9-Nickel,R., Shummer,A., Seiferle,E. (1979) The viscera of the domestic mammals, 2nd edn. Springer-Verlag, New York, USA.

External links

SUNY Labs 37:11-0101 - "Abdominal Cavity: The Jejunum and the Ileum"
SUNY Anatomy Image 7787
SUNY Anatomy Image 8755
BU Histology Learning System: 12001oca
Ileal Villi at endoatlas.com
Ileum Microscopic Cross Section at nhmccd.edu
Ileum 20x at deltagen.com
Peyer's Patches at thehealthnews.org

UpToDate Contents

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English Journal

Innate and adaptive immune mechanisms are effectively induced in ileal Peyer's patches of Salmonella typhimurium infected pigs.

Martins RP, Lorenzi V, Arce C, Lucena C, Carvajal A, Garrido JJ.SourceGrupo de Genómica y Mejora Animal, Departamento de Genética, Facultad de Veterinaria, Universidad de Córdoba, Campus de Rabanales, Edificio Gregor Mendel C5, 14071 Córdoba, Spain.
Developmental and comparative immunology.Dev Comp Immunol.2013 Sep;41(1):100-4. doi: 10.1016/j.dci.2013.04.020. Epub 2013 May 3.
In this report we employed laser-capture microdissection (LCM) coupled to qPCR technology and bioinformatic analysis to characterize, for the first time, the response of Peyer's patches (PP) from orally infected animals to Salmonella typhimurium, in a model of non-typhoidal salmonellosis. Pathogen w
PMID 23644015

Predicting complicated Crohn's disease and surgery: phenotypes, genetics, serology and psychological characteristics of a population-based cohort.

Ryan JD, Silverberg MS, Xu W, Graff LA, Targownik LE, Walker JR, Carr R, Clara I, Miller N, Rogala L, Bernstein CN.SourceDepartment of Internal Medicine, University of Manitoba, Winnipeg, MB, Canada.
Alimentary pharmacology & therapeutics.Aliment Pharmacol Ther.2013 Aug;38(3):274-83. doi: 10.1111/apt.12368. Epub 2013 Jun 3.
BACKGROUND: Predictors of complicated Crohn's disease (CD), defined as stricturing or penetrating behaviour, and surgery have largely been derived from referral centre populations.AIM: To investigate whether serological markers, susceptibility genes or psychological characteristics are associated wi
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Casein hydrolysate diet controls intestinal T cell activation, free radical production and microbial colonisation in NOD mice.

Emani R, Asghar MN, Toivonen R, Lauren L, Söderström M, Toivola DM, van Tol EA, Hänninen A.SourceDepartment of Medical Microbiology and Immunology, Kiinamyllynkatu 13, FIN-20520, Turku, Finland.
Diabetologia.Diabetologia.2013 Aug;56(8):1781-1791. Epub 2013 Jun 8.
AIMS/HYPOTHESIS: Dietary and microbial factors and the gut immune system are important in autoimmune diabetes. We evaluated inflammatory activity in the whole gut in prediabetic NOD mice using ex vivo imaging of reactive oxygen and nitrogen species (RONS), and correlated this with the above-mentione
PMID 23748859

Japanese Journal

Morphological Analysis of the Residual Rectal Mucosa in 12 Postoperative Ulcerative Colitis Patients

弘前医学 67(1), 92-101, 2016-07-29
NAID 120005822593

症例関節リウマチに対するmethotrexate治療中に発症した悪性リンパ腫による回腸穿孔の1例

外科 = Surgery : 臨床雑誌 78(5), 555-559, 2016-05
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症例報告術前に卵巣癌との鑑別が困難であった回盲部腸管重複症に発生した腺癌の1例

東京産科婦人科学会会誌 65(2), 207-211, 2016-04
NAID 40020844056

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Ileum
	Small intestine
	The cecal fossa. The ileum and cecum are drawn backward and upward.
Gray's	subject #248 1171
Artery	ileal arteries
Vein	ileal veins
Nerve	celiac ganglia, vagus
Precursor	midgut
Dorlands/Elsevier	Ileum