Jejunum - wikipedia Jejunum Jejunum Small intestine Superior and inferior duodenal fossæ. Details Precursor midgut Artery jejunal arteries Vein jejunal veins Nerve celiac ganglia, vagus Identifiers Latin Jejunum MeSH D007583 TA A05. 6.03. 001 FMA 7207 Anatomical terminology ( edit on Wikidata ) The jejunum ( / dʒ ɪˈdʒuːnəm / ) is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. The jejunum lies between the duodenum and the ileum. The jejunum is considered to begin at the attachment of the suspensory muscle of the duodenum to the duodenum, a location called the duodenojejunal flexure. The division between the jejunum and ileum is not anatomically distinct. In adult humans, the small intestine is usually 6 - 7m long, about two - fifths of which ( 2.5 m ) is the jejunum. Contents 1 Structure 1.1 Histology 2 Function 3 Other animals 4 History 4.1 Etymology 5 References 6 External links Structure See also : Small intestine The interior surface of the jejunum -- which is exposed to ingested food -- is covered in finger - like projections of mucosa, called villi, which increase the surface area of tissue available to absorb nutrients from ingested foodstuffs. The epithelial cells which line these villi have microvilli. The transport of nutrients across epithelial cells through the jejunum and ileum includes the passive transport of sugar fructose and the active transport of amino acids, small peptides, vitamins, and most glucose. The villi in the jejunum are much longer than in the duodenum or ileum. The pH in the jejunum is usually between 7 and 9 ( neutral or slightly alkaline ). The jejunum and the ileum are suspended by mesentery which gives the bowel great mobility within the abdomen. It also contains circular and longitudinal smooth muscle which helps to move food along by a process known as peristalsis. If the jejunum is impacted by blunt force the emesis reflex ( vomiting ) will be initiated. Histology The jejunum contains very few Brunner 's glands ( found in the duodenum ) or Peyer 's patches ( found in the ileum ). However, there are a few jejunal lymph nodes suspended in its mesentery. The jejunum has many large circular folds in its submucosa called plicae circulares which increase the surface area for nutrient absorption. The plicae circulares are the best developed in the jejunum. There is no line of demarcation between the jejunum and the ileum. However, there are subtle histological differences : The jejunum has less fat inside its mesentery than the ileum. The jejunum is typically of larger diameter than the ileum. The villi of the jejunum look like long, finger - like projections, and are a histologically identifiable structure. While the length of the entire intestinal tract contains lymphoid tissue, only the ileum has abundant Peyer 's patches, which are unencapsulated lymphoid nodules that contain large numbers of lymphocytes and immune cells, like microfold cells. Transmission electron microscope ( TEM ) image of human jejunum TEM image of mouse jejunum ( 14,000-fold magnification ) Dog jejunum ( magnified 100-fold ) Function The lining of the jejunum is specialized for the absorption, by enterocytes, of small nutrient particles which have been previously digested by enzymes in the duodenum. Once absorbed, nutrients ( with the exception of fat, which goes to the lymph ) pass from the enterocytes into the enterohepatic circulation and enter the liver via the hepatic portal vein, where the blood is processed. The jejunum is involved in magnesium absorption. Other animals In fish, the divisions of the small intestine are not as clear and the terms middle intestine or mid-gut may be used instead of jejunum. History Etymology Jejunum is derived from the Latin word jējūnus, meaning `` fasting. '' It was so called because this part of the small intestine was frequently found to be void of food following death, due to its intensive peristaltic activity relative to the duodenum and ileum. The Early Modern English adjective jejune is derived from this word. References Jump up ^ Physiology : 6 / 6ch2 / s6ch2_30 - Essentials of Human Physiology Jump up ^ OED 2nd edition, 1989. Jump up ^ Entry `` jejunum '' in Merriam - Webster Online Dictionary. ^ Jump up to : Drake, Richard L. ; Vogl, Wayne ; Tibbitts, Adam W.M. Mitchell ; illustrations by Richard ; Richardson, Paul ( 2005 ). Gray 's anatomy for students. Philadelphia : Elsevier / Churchill Livingstone. pp. 273 -- 275. ISBN 978 - 0 - 8089 - 2306 - 0. Jump up ^ Deakin, Barbara Young... ( et al. ) ; drawings by Philip J. ( 2006 ). Wheater 's functional histology : a text and colour atlas ( 5th ed. ). ( Edinburgh ? ) : Churchill Livingstone / Elsevier. p. 263,. ISBN 978 - 0 - 443 - 068 - 508. Jump up ^ Moon, Jackie. SemiPro. Jump up ^ CRANE, RK ( Oct 1960 ). `` Intestinal absorption of sugars ''. Physiological Reviews. 40 : 789 -- 825. PMID 13696269. Jump up ^ Guillaume, Jean ; Praxis Publishing ; Sadasivam Kaushik ; Pierre Bergot ; Robert Metailler ( 2001 ). Nutrition and Feeding of Fish and Crustaceans. Springer. p. 31. ISBN 9781852332419. Retrieved 2009 - 01 - 09. Jump up ^ Harper, Douglas. `` jejunum ''. Etymology Online. Retrieved 15 November 2014. Jump up ^ `` Oxford English Dictionary : jejune, adj ''. External links Gastrolab.net : The Jejunum Peyer 's patches Anatomy photo : 37 : 11 - 0100 at the SUNY Downstate Medical Center -- `` Abdominal Cavity : The Jejunum and the Ileum '' Anatomy image : 7856 at the SUNY Downstate Medical Center Anatomy of the gastrointestinal tract, excluding the mouth Upper Pharynx Muscles Spaces peripharyngeal retropharyngeal parapharyngeal retrovisceral danger prevertebral Pterygomandibular raphe Pharyngeal raphe Buccopharyngeal fascia Pharyngobasilar fascia Piriform sinus Esophagus Sphincters upper lower glands Stomach Curvatures greater lesser Angular incisure Cardia Body Fundus Pylorus antrum canal sphincter Gastric mucosa Gastric folds Microanatomy Gastric pits Gastric glands Cardiac glands Fundic glands Pyloric glands Foveolar cell Parietal cell Gastric chief cell Enterochromaffin - like cell Lower Small intestine Microanatomy Intestinal villus Intestinal gland Enterocyte Enteroendocrine cell Goblet cell Paneth cell Duodenum Suspensory muscle Major duodenal papilla Minor duodenal papilla Duodenojejunal flexure Brunner 's glands Jejunum No substructures Ileum Ileocecal valve Peyer 's patches Microfold cell Large intestine Cecum Appendix Colon Ascending colon Hepatic flexure Transverse colon Splenic flexure Descending colon Sigmoid colon Continuous taenia coli haustra epiploic appendix Rectum Transverse folds Ampulla Anal canal Anus Anal columns Anal valves Anal sinuses Pectinate line Internal anal sphincter Intersphincteric groove External anal sphincter Wall Serosa / Adventitia Subserosa Muscular layer Submucosa Circular folds Mucosa Muscularis mucosa Retrieved from `` https://en.wikipedia.org/w/index.php?title=Jejunum&oldid=835139938 '' Categories : Digestive system Hidden categories : Pages with unresolved properties All articles with unsourced statements Articles with unsourced statements from September 2014 Talk Contents About Wikipedia বাংলা Bahasa Banjar Bosanski Català Čeština Cymraeg Deutsch ދިވެހިބަސް Eesti Español Esperanto Euskara فارسی Français Galego 한국어 Ido Bahasa Indonesia Íslenska Italiano עברית Basa Jawa Kapampangan Қазақша Kurdî Latviešu Lietuvių Limburgs Magyar Nederlands 日本 語 Norsk Polski Português Română Русский Simple English Slovenčina Slovenščina Svenska Tagalog ไทย Türkçe Українська 中文 37 more Edit links This page was last edited on 6 April 2018, at 20 : 14. 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Question: function of the jejunum in the digestive system
Answer: absorption, by enterocytes, of small nutrient particles which have been previously digested by enzymes in the duodenum