Editing Stomach

{{short description|Digestive organ}}
{{About|the internal organ|the middle part of the body|Abdomen|other uses|Stomach (disambiguation)}}
{{Redirect|Gastric|the sauce flavoring|Gastrique}}
{{Infobox anatomy
| Name        = Stomach
| Latin       = ventriculus, stomachus 
| Greek       = στόμαχος
| Image      = File:Gray1046.svg
| Caption    = Sections of the human stomach
| Width       =
| Image2       = Tractus intestinalis ventriculus.svg
| Caption2     = Scheme of [[Gastrointestinal tract|digestive tract]], with stomach in red
| Precursor   = [[Foregut]]
| System      = [[Digestion|Digestive system]]
| Artery      = [[Right gastric artery]], [[left gastric artery]], [[right gastro-omental artery]], [[left gastro-omental artery]], [[short gastric arteries]]
| Vein        = [[Right gastric vein]], [[left gastric vein]], [[right gastroepiploic vein]], [[left gastroepiploic vein]], [[short gastric veins]]
| Nerve       = [[Celiac ganglia]], [[vagus nerve]]<ref>{{cite book| title= Essentials of Human Physiology| first= Thomas M. |last= Nosek| chapter=Section 6/6ch2/s6ch2_30 |chapter-url=http://humanphysiology.tuars.com/program/section6/6ch2/s6ch2_30.htm |archive-url=https://web.archive.org/web/20160324124828/http://humanphysiology.tuars.com/program/section6/6ch2/s6ch2_30.htm|archive-date=2016-03-24}}</ref>
| Lymph       = [[Celiac lymph nodes]]<ref>{{NormanAnatomy|stomach|The Stomach }}</ref>
}}
{{Gastrointestinal tract sidebar}}
The '''stomach''' is a muscular, [[hollow organ]] in the [[upper gastrointestinal tract]] of [[Human|humans]] and many other animals, including several [[invertebrate]]s. The [[Ancient Greek]] name for the stomach is ''gaster'' which is used as ''gastric'' in medical terms related to the stomach.<ref name="MW1">{{cite web |title=Definition of GASTRIC |url=https://www.merriam-webster.com/dictionary/gastric |website=www.merriam-webster.com |access-date=13 May 2025 |language=en |date=12 May 2025}}</ref> The stomach has a dilated structure and functions as a vital organ in the [[digestive system]]. The stomach is involved in the [[gastric phase|gastric phase of digestion]], following the [[cephalic phase]] in which the sight and smell of food and the act of [[chewing]] are stimuli.  In the stomach a chemical breakdown of food takes place by means of secreted  [[digestive enzyme]]s and [[gastric acid]]. It also plays a role in regulating gut [[microbiota]], influencing digestion and overall health.<ref name="Chaurasia2013">{{Cite book |last=Chaurasia |first=B.D. |title=Human Anatomy |publisher=CBS Publishers and Distributors |year=2013 |isbn=978-81-239-2331-4 |edition=6th |volume=2 |location=4819/XI, Prahlad Street, Ansari Road, Daryaganj, New Delhi 110002, India |pages=250–252 |chapter=19}}</ref>

The stomach is located between the [[esophagus]] and the [[small intestine]].  The [[pyloric sphincter]] controls the passage of partially digested food ([[chyme]]) from the stomach into the [[duodenum]], the first and shortest part of the small intestine, where [[peristalsis]] takes over to move this through the rest of the intestines.

==Structure==
In the [[human digestive system]], the stomach lies between the [[esophagus]] and the [[duodenum]] (the first part of the [[small intestine]]). It is in the [[Quadrants and regions of abdomen#Quadrants|left upper quadrant]] of the [[abdominal cavity]]. The top of the stomach lies against the [[diaphragm (anatomy)|diaphragm]]. Lying behind the stomach is the [[pancreas]]. A large double fold of visceral [[peritoneum]] called the [[greater omentum]] hangs down from the [[Curvatures of the stomach|greater curvature]] of the stomach. Two [[sphincter]]s keep the contents of the stomach contained; the [[oesophagus#Sphincters|lower esophageal sphincter]]  (found in the cardiac region), at the junction of the esophagus and stomach, and the [[pyloric sphincter]] at the junction of the stomach with the duodenum.

The stomach is surrounded by [[parasympathetic nervous system|parasympathetic]] (inhibitor) and [[sympathetic nervous system|sympathetic]] (stimulant) [[plexuses]] (networks of [[blood vessel]]s and [[nerve]]s in the [[anterior]] gastric, [[Posterior (anatomy)|posterior]], [[Anatomical terms of location#Superior and inferior|superior]] and [[Anatomical terms of location#Superior and inferior|inferior]], celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles.

The stomach is [[wikt:distensibility|distensible]], and can normally expand to hold about one litre of food.<ref>{{cite book |author=Sherwood, Lauralee |title=Human physiology: from cells to systems |publisher=Wadsworth Pub. Co |location=Belmont, CA |year=1997 |isbn=978-0-314-09245-8 |oclc=35270048 |url-access=registration |url=https://archive.org/details/humanphysiologyf00sher }}</ref> The shape of the stomach depends upon the degree of its distension and that of surrounding viscera, e.g. the colon.<ref name="Chaurasia2013">{{Cite book |last=Chaurasia |first=B.D. |title=Human Anatomy |publisher=CBS Publishers and Distributors |year=2013 |isbn=978-81-239-2331-4 |edition=6th |volume=2 |location=4819/XI, Prahlad Street, Ansari Road, Daryaganj, New Delhi 110002, India |pages=250–252 |chapter=19}}</ref> When empty, the stomach is somewhat J-shaped; when partially distended, it becomes pyriform in shape. In obese persons, it is more horizontal.<ref name="Chaurasia2013" /> In a newborn human baby the stomach will only be able to hold about 30 millilitres. The maximum stomach volume in adults is between 2 and 4 litres,<ref name="pmid9863573">{{cite journal |vauthors=Wenzel V, Idris AH, Banner MJ, Kubilis PS, Band R, Williams JL, etal| title=Respiratory system compliance decreases after cardiopulmonary resuscitation and stomach inflation: impact of large and small tidal volumes on calculated peak airway pressure | journal=Resuscitation |year=1998 |volume=38 |issue=2 |pages=113–8 |pmid=9863573 |doi=10.1016/S0300-9572(98)00095-1}}</ref><ref>{{cite book|author=Curtis, Helena & N. Sue Barnes|title=Invitation to Biology|edition=5|publisher=Worth|year=1994}}</ref> although volumes of up to 15 litres have been observed in extreme circumstances.<ref>Morris D. Kerstein, Barry Goldberg, Barry Panter, M. David Tilson, Howard Spiro, Gastric Infarction, Gastroenterology, Volume 67, Issue 6, 1974, Pages 1238–1239, ISSN 0016-5085, https://doi.org/10.1016/S0016-5085(19)32710-6.</ref>

=== Sections ===
{{Redirect|Cardia|the ancient Greek colony|Cardia (Thrace)}}
[[File:2414 Stomach.jpg|thumb|Diagram showing parts of the stomach]]

The human stomach can be divided into four sections, beginning at the cardia followed by the fundus, the body and the pylorus.<ref name="Tortora09">{{cite book |last1=Tortora |first1=Gerard J. |last2=Derrickson |first2=Bryan H. |title=Principles of anatomy and physiology |date=2009 |publisher=Wiley |location=Hoboken, NJ |isbn=9780470233474 |pages=937–942 |edition=12., internat. student version}}</ref><ref name=Elsevier />
* The gastric '''cardia''' is where the contents of the esophagus empty from the [[gastroesophageal sphincter]] into the cardiac orifice, the opening into the gastric cardia.<ref name=SCHWARTZ2010 /><ref name=Elsevier/> A cardiac notch at the left of the cardiac orifice, marks the beginning of the [[greater curvature]] of the stomach. A horizontal line across from the cardiac notch gives the dome-shaped region called the fundus.<ref name=Elsevier /> The cardia is a very small region of the stomach that surrounds the esophageal opening.<ref name=Elsevier />
* The '''fundus''' ({{ety|la||bottom}}) is formed in the upper curved part.
* The '''body''' or '''corpus''' is the main, central region of the stomach.
* The [[pylorus]] opens to the body of the stomach. The pylorus ({{ety|el||gatekeeper}}) connects the stomach to the [[duodenum]] at the [[pyloric sphincter]].

The cardia is defined as the region following the "z-line" of the [[gastroesophageal junction]], the point at which the [[epithelium]] changes from [[stratified squamous epithelia|stratified squamous]] to [[columnar]]. Near the cardia is the lower esophageal sphincter.<ref name=SCHWARTZ2010 >{{cite book|editor-first=F. Charles |editor-last=Brunicardi |editor2-first=Dana K. |editor2-last=Andersen |title=Schwartz's principles of surgery|date=2010|publisher=McGraw-Hill, Medical Pub. Division|location=New York|isbn=978-0071547703|edition=9th|display-editors=etal}}</ref>

=== Anatomical proximity ===
The '''stomach bed''' refers to the structures upon which the  stomach rests in mammals.<ref>[https://books.google.com/books?id=S9MvAQAAMAAJ&dq=%22stomach+bed%22&pg=RA1-PA7] Habershon, S. H. "Diseases of the Stomach: A Manual for Practitioners and Students,"Chicago Medical Book Company, 1909,  page 11.</ref><ref>[https://books.google.com/books?id=fn7TUwyORwQC&dq=%22stomach+bed%22&pg=PA157] Weber, John and Shearer, Edwin Morrill "Shearer's manual of human dissection, Eighth Edition," McGraw Hill, 1999, page 157. {{ISBN|0-07-134624-4}}.</ref> These include the [[tail of the pancreas]], [[splenic artery]], left [[kidney]], left [[suprarenal gland]], [[transverse colon]] and its [[mesocolon]], and the [[left crus of diaphragm]], and the [[left colic flexure]]. The term was introduced around 1896 by Philip Polson of the Catholic University School of Medicine, Dublin. However this was brought into disrepute by surgeon anatomist J Massey.<ref>[https://archive.org/details/transactionsroy01irelgoog/page/n434 <!-- quote="stomach bed". -->] Transactions of the Royal Academy of Medicine in Ireland, Volume 14, 1896, "Birmingham, A(mbrose), "Topographical anatomy of the spleen, pancreas, duodenum, kidneys, &c.", pages 363-385. Retrieved 29 February 2011.</ref><ref>[https://books.google.com/books?id=nKdMAQAAIAAJ&dq=%22stomach+bed%22&pg=PA524] The Lancet, Volume 1, Part 1, 22 February 1902. page 524, "Royal Academy of Medicine in Ireland." Retrieved 28 February 2012</ref><ref>[https://books.google.com/books?id=yWoBAAAAYAAJ&dq=%22stomach+bed%22+birmingham&pg=PA353] The Dublin journal of medical science, Volume 114, page 353."Reviews and bibliographical notes." Retrieved 28 February 2012.</ref>

=== Blood supply ===
[[Image:Stomach blood supply.svg|thumb|240px|Schematic image of the blood supply to the human stomach: [[left gastric artery|left]] and [[right gastric artery]], [[left gastroepiploic artery|left]] and [[right gastroepiploic artery]] and [[short gastric arteries]]<ref name=Moore150>{{cite book |author1=Anne M. R. Agur |author2=Moore, Keith L. |title=Essential Clinical Anatomy (Point (Lippincott Williams & Wilkins)) |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year= 2007|isbn=978-0-7817-6274-8 |oclc= 172964542}}; p. 150</ref>]]

The lesser curvature of the human stomach is supplied by the [[right gastric artery]] inferiorly and the [[left gastric artery]] superiorly, which also supplies the cardiac region. The greater curvature is supplied by the [[right gastroepiploic artery]] inferiorly and the [[left gastroepiploic artery]] superiorly. The fundus of the stomach, and also the upper portion of the greater curvature, is supplied by 5-7 [[short gastric arteries]], which arise from the splenic artery.<ref name="Chaurasia2013"/>

===Lymphatic drainage===
The two sets of [[gastric lymph nodes]] drain the stomach's tissue fluid into the lymphatic system through the [[intestinal lymph trunk]], to the [[cisterna chyli]].<ref name="Chaurasia2013"/>

===Microanatomy===
====Wall====
{{Main article|Gastrointestinal wall}}
[[Image:Gastrointestinal wall of human stomach hariadhi.svg|thumb|right|The gastrointestinal wall of the human stomach]]
[[File:Layers of the GI Tract english.svg|thumb|Layers of the gastrointestinal wall of which the stomach is a dilated part]]

Like the other parts of the [[gastrointestinal wall]], the human stomach wall from inner to outer, consists of a [[mucosa]], [[submucosa]], [[muscular layer]], [[subserosa]] and [[serosa]].<ref>{{cite web|title=University of Rochester medical center|url=https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=34&contentid=17785-1|date=2020|access-date=2021-12-19|archive-date=2021-11-19|archive-url=https://web.archive.org/web/20211119050031/https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=34&contentid=17785-1|url-status=dead}}</ref>

The inner part of the stomach wall is the [[gastric mucosa]] a mucous membrane that forms the lining of the stomach. the membrane consists of an outer layer of [[columnar epithelium]], a [[lamina propria]], and a thin layer of [[smooth muscle]] called the [[muscularis mucosa]]. Beneath the mucosa lies the [[submucosa]], consisting of [[fibrous connective tissue]].<ref>{{Cite web|title=Stomach histology|url=https://www.kenhub.com/en/library/anatomy/stomach-histology|access-date=2021-01-09|website=Kenhub|language=en}}</ref> [[Meissner's plexus]] is in this layer interior to the oblique muscle layer.<ref>{{Cite book|title=Gastrointestinal physiology : development, principles and mechanisms of regulation|last=Welcome, Menizibeya Osain|publisher=Springer|year=2018|isbn=978-3-319-91056-7|location=Cham, Switzerland|pages=628|oclc=1042217248}}</ref>

Outside of the submucosa lies the muscular layer. It consists of three layers of muscular fibres, with fibres lying at angles to each other. These are the inner oblique, middle circular, and outer longitudinal layers.<ref>{{Cite web |date=2018-07-22 |title=22.5C: Muscularis |url=https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Anatomy_and_Physiology_(Boundless)/22%3A_Digestive_System/22.05%3A_Layers_of_the_Alimentary_Canal/22.5C%3A_Muscularis |access-date=2024-02-09 |website=Medicine LibreTexts |language=en}}</ref> The presence of the inner oblique layer is distinct from other parts of the gastrointestinal tract, which do not possess this layer.<ref>{{Cite web|title=SIU SOM Histology GI|url=http://www.siumed.edu/~dking2/erg/stomach.htm|access-date=2021-01-09|website=www.siumed.edu|archive-date=2021-01-11|archive-url=https://web.archive.org/web/20210111015056/http://www.siumed.edu/~dking2/erg/stomach.htm|url-status=dead}}</ref> The stomach contains the thickest muscular layer consisting of three layers, thus maximum peristalsis occurs here.
* The ''inner oblique layer:'' This layer is responsible for creating the motion that churns and physically breaks down the food. It is the only layer of the three which is not seen in other parts of the [[digestive system]]. The antrum has thicker skin cells in its walls and performs more forceful contractions than the fundus.
* The ''middle circular layer:'' At this layer, the [[pylorus]] is surrounded by a thick circular muscular wall, which is normally tonically constricted, forming a functional (if not anatomically discrete) [[pyloric sphincter]], which controls the movement of [[chyme]] into the [[duodenum]]. This layer is concentric to the [[Anatomical terms of location#Axes|longitudinal axis]] of the stomach.
* The [[myenteric plexus]] (Auerbach's plexus) is found between the outer longitudinal and the middle circular layer and is responsible for the innervation of both (causing [[peristalsis]] and mixing).

The ''outer longitudinal layer'' is responsible for moving the semi-digested food towards the pylorus of the stomach through muscular shortening.

To the outside of the muscular layer lies a [[serosa]], consisting of layers of connective tissue continuous with the [[peritoneum]].

Smooth mucosa along the inside of the lesser curvature forms a passageway - the '''gastric canal'''  that fast-tracks liquids entering the stomach, to the pylorus.<ref name=Elsevier>{{citation |title=Gray's Anatomy |url=https://www.uk.elsevierhealth.com/grays-anatomy-9780702077050.html |publisher=Elsevier |edition=42nd |pages=1160–1163 |author-first=Susan |author-last=Standring}}</ref>

====Glands====
{{Main article|Gastric glands}}
[[File:Illu_stomach_layers.jpg|thumb|Diagram showing gastric pits (13) gastric glands (12) lamina propria (10) epithelium (11)]]
[[File:Histology of normal fundic mucosa.png|thumb|Histology of normal fundic mucosa. Fundic glands are simple, branched tubular glands that extend from the bottom of the gastric pits to the muscularis mucosae; the more distinctive cells are parietal cells. H&E stain.]]
[[File:Histology of normal antral mucosa.png|thumb|Histology of normal antral mucosa. Antral mucosa is formed by branched coiled tubular glands lined by secretory cells similar in appearance to the surface mucous cells. H&E stain.]]
The mucosa lining the stomach is lined with [[gastric pit]]s, which receive [[gastric juice]], secreted by between 2 and 7 [[gastric glands]].{{citation needed|date=May 2020}} Gastric juice is an acidic fluid containing [[hydrochloric acid]] and digestive enzymes.<ref>{{Cite web |date=21 August 2009 |title=How does the Stomach Work? |url=https://www.ncbi.nlm.nih.gov/books/NBK279304/#:~:text=Gastric%20juice%3A%20Acid%2C%20salts%20and%20enzymes&text=These%20glands%20make%20digestive%20enzymes,juice%20are%20made%20each%20day. |access-date=16 June 2024 |website=National Institute of Health: National Library of Medicine |publisher=Institute for Quality and Efficiency in Health Care (IQWiG).}}</ref> The glands contains a number of cells, with the function of the glands changing depending on their position within the stomach.{{citation needed|date=May 2020}}

Within the body and fundus of the stomach lie the ''fundic glands''. In general, these glands are lined by column-shaped cells that secrete a protective layer of [[mucus]] and [[bicarbonate]]. Additional cells present include [[parietal cell]]s that secrete hydrochloric acid and [[intrinsic factor]], [[Gastric chief cell|chief cell]]s that secrete [[pepsinogen]] (this is a precursor to pepsin- the highly acidic environment converts the pepsinogen to pepsin), and neuroendocrine cells that secrete [[serotonin]].<ref name=Dorland777/>{{citation needed|date=May 2020}}

Glands differ where the stomach meets the esophagus and near the pylorus.<ref>{{Cite journal|last1=Gallego-Huidobro|first1=J|last2=Pastor|first2=L M|date=April 1996|title=Histology of the mucosa of the oesophagogastric junction and the stomach in adult Rana perezi.|journal=Journal of Anatomy|volume=188|issue=Pt 2|pages=439–444|issn=0021-8782|pmc=1167580|pmid=8621343}}</ref> Near the [[gastroesophageal junction]] lie ''cardiac glands'', which primarily secrete mucus.<ref name=Dorland777>{{cite book|last1=Dorland's|title=Dorland's Illustrated Medical Dictionary|date=2012|publisher=Elsevier|isbn=978-1-4160-6257-8|page=777|edition=32nd}}</ref> They are fewer in number than the other gastric glands and are more shallowly positioned in the mucosa. There are two kinds - either simple [[tubular gland]]s with short ducts  or [[compound racemose glands|compound racemose]] resembling the [[duodenal]] [[Brunner's glands]].{{citation needed|date=October 2019}} Near the pylorus lie ''pyloric glands'' located in the antrum of the pylorus. They secrete mucus, as well as [[gastrin]] produced by their [[G cells]].<ref>{{cite book|last1=Dorland's|title=Dorland's Illustrated Medical Dictionary|date=2012|publisher=Elsevier|isbn=978-1-4160-6257-8|page=762|edition=32nd}}</ref>{{citation needed|date=May 2020}}

=== Gene and protein expression ===
{{Further |Bioinformatics#Gene and protein expression}}
About 20,000 [[protein-coding genes]] are expressed in human cells and nearly 70% of these genes are expressed in the normal stomach.<ref>{{Cite web|url=https://www.proteinatlas.org/humanproteome/stomach|title=The human proteome in stomach - The Human Protein Atlas|website=www.proteinatlas.org|access-date=2017-09-25}}</ref><ref>{{Cite journal|last1=Uhlén|first1=Mathias|last2=Fagerberg|first2=Linn|last3=Hallström|first3=Björn M.|last4=Lindskog|first4=Cecilia|last5=Oksvold|first5=Per|last6=Mardinoglu|first6=Adil|last7=Sivertsson|first7=Åsa|last8=Kampf|first8=Caroline|last9=Sjöstedt|first9=Evelina|date=2015-01-23|title=Tissue-based map of the human proteome|journal=Science|language=en|volume=347|issue=6220|pages=1260419|doi=10.1126/science.1260419|issn=0036-8075|pmid=25613900|s2cid=802377}}</ref> Just over 150 of these genes are more specifically expressed in the stomach compared to other organs, with only some 20 genes being highly specific. The corresponding specific proteins expressed in stomach are mainly involved in creating a suitable environment for handling the digestion of food for uptake of nutrients. Highly stomach-specific proteins include [[gastrokine-1]] expressed in the mucosa; [[pepsinogen]] and [[gastric lipase]], expressed in [[gastric chief cell]]s; and a gastric [[Hydrogen potassium ATPase|ATPase]] and [[gastric intrinsic factor]], expressed in [[parietal cell]]s.<ref>{{Cite journal|last1=Gremel|first1=Gabriela|last2=Wanders|first2=Alkwin|last3=Cedernaes|first3=Jonathan|last4=Fagerberg|first4=Linn|last5=Hallström|first5=Björn|last6=Edlund|first6=Karolina|last7=Sjöstedt|first7=Evelina|last8=Uhlén|first8=Mathias|last9=Pontén|first9=Fredrik|date=2015-01-01|title=The human gastrointestinal tract-specific transcriptome and proteome as defined by RNA sequencing and antibody-based profiling|journal=Journal of Gastroenterology|language=en|volume=50|issue=1|pages=46–57|doi=10.1007/s00535-014-0958-7|pmid=24789573|s2cid=21302849|issn=0944-1174}}</ref>

==Development==
In the early part of the [[human embryogenesis|development of the human embryo]], the ventral part of the embryo abuts the [[yolk sac]]. During the third week of development, as the embryo grows, it begins to surround parts of the yolk sac. The enveloped portions form the basis for the adult gastrointestinal tract.<ref name=LARSEN2009 /> The sac is surrounded by a network of [[vitelline arteries|vitelline arteries and veins]]. Over time, these arteries consolidate into the three main arteries that supply the developing gastrointestinal tract: the [[celiac artery]], [[superior mesenteric artery]], and [[inferior mesenteric artery]]. The areas supplied by these arteries are used to define the [[foregut]], [[midgut]], and [[hindgut]].<ref name=LARSEN2009 /> The surrounded sac becomes the primitive gut. Sections of this gut begin to differentiate into the organs of the gastrointestinal tract, and the esophagus, and stomach form from the foregut.<ref name=LARSEN2009>{{cite book|author=Gary C. Schoenwolf |title=Larsen's human embryology|year=2009|publisher=Churchill Livingstone/Elsevier|location=Philadelphia|isbn=978-0-443-06811-9|chapter=Development of the Gastrointestinal Tract|edition=4th}}</ref>

As the stomach rotates during early development, the dorsal and ventral mesentery rotate with it; this rotation produces a space anterior to the expanding stomach called the greater sac, and a space posterior to the stomach called the lesser sac. After this rotation the dorsal mesentery thins and forms the greater [[Greater omentum|omentum]], which is attached to the greater curvature of the stomach. The ventral mesentery forms the lesser omentum, and is attached to the developing [[liver]]. In the adult, these connective structures of omentum and mesentery form the [[peritoneum]], and act as an insulating and protective layer while also supplying organs with [[blood]] and lymph vessels as well as nerves.<ref name="SADLER">Sadler, T.W, (2011) Langman’s Medical Embryology (12th edition), LWW, Baltimore, MD</ref> Arterial supply to all these structures is from the [[celiac trunk]], and venous drainage is by the [[portal venous system]]. Lymph from these organs is drained to the prevertebral celiac nodes at the origin of the celiac artery from the [[aorta]].

==Function==
===Digestion===
{{Further|Human digestive system}}
{{See also|Gastric acid}}
In the [[human digestive system]], a [[Bolus (digestion)|bolus]] (a small rounded mass of [[mastication|chewed up]] food) enters the stomach through the esophagus via the [[Esophagus#Sphincters|lower esophageal sphincter]]. The stomach releases [[proteases]] (protein-digesting [[enzyme]]s such as [[pepsin]]), and [[hydrochloric acid]], which kills or inhibits [[bacteria]] and provides the acidic [[pH]] of 2 for the proteases to work. Food is churned by the stomach through [[Peristalsis|peristaltic]] muscular contractions of the wall – reducing the volume of the bolus, before looping around the fundus<ref>{{cite book |author1=Richard M. Gore |author2=Marc S. Levine. |title=Textbook of Gastrointestinal Radiology |publisher=Saunders |location=Philadelphia, PA. |year= 2007|isbn=978-1-4160-2332-6}}</ref> and the [[body of stomach]] as the boluses are converted into [[chyme]] (partially digested food). Chyme slowly passes through the [[pyloric sphincter]] and into the [[duodenum]] of the [[small intestine]], where the extraction of nutrients begins.

[[Gastric juice]] in the stomach contains [[pepsinogen]] and [[gastric acid]], ([[hydrochloric acid]]) which activates this inactive form of enzyme into the active form, pepsin. Pepsin breaks down proteins into [[polypeptides]].

====Mechanical digestion====
Within a few moments after food enters the stomach, mixing waves begin to occur at intervals of approximately 20 seconds. A mixing wave is a unique type of [[peristalsis]] that mixes and softens the food with gastric juices to create chyme. The initial mixing waves are relatively gentle, but these are followed by more intense waves, starting at the body of the stomach and increasing in force as they reach the pylorus. 

The pylorus, which holds around 30 mL of chyme, acts as a filter, permitting only liquids and small food particles to pass through the mostly, but not fully, closed pyloric sphincter. In a process called [[gastric emptying]], rhythmic mixing waves force about 3 mL of chyme at a time through the pyloric sphincter and into the duodenum. Release of a greater amount of chyme at one time would overwhelm the capacity of the small intestine to handle it. The rest of the chyme is pushed back into the body of the stomach, where it continues mixing. This process is repeated when the next mixing waves force more chyme into the duodenum.

Gastric emptying is regulated by both the stomach and the duodenum. The presence of chyme in the duodenum activates receptors that inhibit gastric secretion. This prevents additional chyme from being released by the stomach before the duodenum is ready to process it.<ref name="Openstax Anatomy & Physiology attribution">{{CC-notice|cc=by4|url=https://openstax.org/books/anatomy-and-physiology/pages/23-4-the-stomach}} {{cite book|last1=Betts|first1=J Gordon|last2=Desaix|first2=Peter|last3=Johnson|first3=Eddie|last4=Johnson|first4=Jody E|last5=Korol|first5=Oksana|last6=Kruse|first6=Dean|last7=Poe|first7=Brandon|last8=Wise|first8=James|last9=Womble|first9=Mark D|last10=Young|first10=Kelly A|title=Anatomy & Physiology|location=Houston|publisher=OpenStax CNX|isbn=978-1-947172-04-3|date=September 13, 2023|at=23.4 The Stomach}}</ref>

====Chemical digestion====
The fundus stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in the fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of [[salivary amylase]] continue until the food begins mixing with the acidic chyme. Ultimately, mixing waves incorporate this food with the chyme, the acidity of which inactivates salivary amylase and activates [[lingual lipase]]. Lingual lipase then begins breaking down triglycerides into free fatty acids, and mono- and diglycerides.

The breakdown of protein begins in the stomach through the actions of hydrochloric acid, and the enzyme [[pepsin]].

The stomach can also produce [[gastric lipase]], which can help digesting fat.

The contents of the stomach are completely emptied into the duodenum within two to four hours after the meal is eaten. Different types of food take different amounts of time to process. Foods heavy in carbohydrates empty fastest, followed by high-protein foods. Meals with a high triglyceride content remain in the stomach the longest. Since enzymes in the small intestine digest fats slowly, food can stay in the stomach for 6 hours or longer when the duodenum is processing fatty chyme. However, this is still a fraction of the 24 to 72 hours that full digestion typically takes from start to finish.<ref name="Openstax Anatomy & Physiology attribution"/>

=== Absorption ===
Although the absorption in the human digestive system is mainly a function of the small intestine, some absorption of certain small molecules nevertheless does occur in the stomach through its lining. This includes:
* Water, if the body is [[Dehydration|dehydrated]]
* Medication, such as [[aspirin]]
* [[Amino acids]]<ref>{{Cite book|title = Amino Acids in Animal Nutrition|edition = 2nd|editor-first = J.P.F.|editor-last = D'Mello|chapter = Absorption of Amino acids and Peptides|last1 = Krehbiel|first1 = C.R.|chapter-url = http://www.fcav.unesp.br/Home/departamentos/zootecnia/lucianohauschild/085199654x_chap03.pdf|first2 = J.C.|last2 = Matthews|pages = 41–70|access-date = 2015-04-25|archive-date = 2015-07-15|archive-url = https://web.archive.org/web/20150715082016/http://www.fcav.unesp.br/Home/departamentos/zootecnia/lucianohauschild/085199654x_chap03.pdf|url-status = dead}}</ref>
* 10–20% of ingested [[ethanol]] (e.g. from alcoholic beverages)<ref name=intox>{{cite web|title=Alcohol and the Human Body|url=http://www.intox.com/t-physiology.aspx|publisher=Intoximeters, Inc.|access-date=30 July 2012}}</ref>
* [[Caffeine]]<ref>{{Cite book|title = Coffee and Health|last = Debry|first = Gérard|publisher = John Libbey Eurotext|year = 1994|isbn = 9782742000371|location = Montrouge|url = https://books.google.com/books?id=uZaaCk-8s9sC&pg=PA129|access-date = 2015-04-26|format = PDF (eBook)|page = 129}}</ref>
* To a small extent water-soluble [[vitamin]]s (most are absorbed in the small intestine)<!-- See page 419--><ref>{{Cite book|title = Nutritional Sciences: From Fundamentals to Food|last1=McGuire|first1=Michelle|last2=Beerman|first2=Kathy|publisher=Cengage Learning|edition=3|url = https://books.google.com/books?id=bYAJAAAAQBAJ|isbn=978-1133707387|date=2012-01-01|page=419}}</ref>

The [[parietal cell]]s of the human stomach are responsible for producing [[intrinsic factor]], which is necessary for the absorption of [[vitamin B12]]. B12 is used in cellular metabolism and is necessary for the production of [[red blood cell]]s, and the functioning of the [[nervous system]].

=== Control of secretion and motility ===
[[Image:Stomach emptying into duodenum.svg|thumb|center|600px|Emptying of stomach chyme into the duodenum through the pyloric sphincter]]

Chyme from the stomach is slowly released into the [[duodenum]] through coordinated [[peristalsis]] and opening of the pyloric sphincter. The movement and the flow of chemicals into the stomach are controlled by both the [[autonomic nervous system]] and by the various [[Digestion#Digestive hormones|digestive hormones]] of the digestive system:

{| class="wikitable"
| [[Gastrin]] || The hormone ''gastrin'' causes an increase in the secretion of HCl from the parietal cells and pepsinogen from chief cells in the stomach. It also causes increased motility in the stomach. Gastrin is released by [[G cell]]s in the stomach in response to distension of the antrum and digestive products (especially large quantities of incompletely digested proteins). It is inhibited by a [[pH]] normally less than 4(high acid), as well as the hormone [[somatostatin]].
 |-
 | [[Cholecystokinin]] || ''Cholecystokinin'' (CCK) has most effect on the [[gall bladder]], causing gall bladder contractions, but it also decreases gastric emptying and increases release of [[Pancreas|pancreatic]] juice, which is alkaline and neutralizes the chyme. CCK is synthesized by I-cells in the mucosal epithelium of the small intestine.
 |-
 | [[Secretin]] || In a different and rare manner, ''secretin'', which has the most effects on the pancreas, also diminishes acid secretion in the stomach. Secretin is synthesized by [[S cell|S-cells]], which are located in the duodenal mucosa as well as in the jejunal mucosa in smaller numbers.
 |-
 | [[Gastric inhibitory polypeptide]] || ''Gastric inhibitory polypeptide'' (GIP) decreases both gastric acid release and motility. GIP is synthesized by K-cells, which are located in the duodenal and jejunal mucosa.
 |-
 | [[Enteroglucagon]] || ''Enteroglucagon'' decreases both gastric acid and motility.
 |-
 |}

Other than gastrin, these hormones all act to turn off the stomach action. This is in response to food products in the [[liver]] and gall bladder, which have not yet been absorbed. The stomach needs to push food into the small intestine only when the intestine is not busy. While the intestine is full and still digesting food, the stomach acts as storage for food.

===Other===
;Effects of EGF
[[Epidermal growth factor]] (EGF) results in cellular proliferation, differentiation, and survival.<ref name="Herbst">{{cite journal | author = Herbst RS | title = Review of epidermal growth factor receptor biology | journal = International Journal of Radiation Oncology, Biology, Physics | volume = 59 | issue = 2 Suppl | pages = 21–6 | year = 2004 | pmid = 15142631 | doi = 10.1016/j.ijrobp.2003.11.041 | doi-access = free }}</ref>  EGF is a low-molecular-weight polypeptide first purified from the mouse submandibular gland, but since then found in many human tissues including the [[submandibular gland]], and the [[parotid gland]]. Salivary EGF, which also seems to be regulated by dietary inorganic [[iodine]], also plays an important physiological role in the maintenance of oro-esophageal and gastric tissue integrity. The biological effects of salivary EGF include healing of oral and gastroesophageal ulcers, inhibition of gastric acid secretion, stimulation of DNA synthesis, and mucosal protection from intraluminal injurious factors such as gastric acid, bile acids, pepsin, and trypsin and from physical, chemical, and bacterial agents.<ref>{{cite journal|author = Venturi S.|author2 = Venturi M.|year = 2009|title = Iodine in evolution of salivary glands and in oral health|journal = Nutrition and Health|volume = 20|pages = 119–134|pmid = 19835108|issue = 2|doi=10.1177/026010600902000204|s2cid = 25710052}}</ref>

;Stomach as nutrition sensor
The human stomach has  receptors responsive to [[sodium glutamate]]<ref>{{cite journal | last1 = Uematsu | first1 = A | last2 = Tsurugizawa | first2 = T | last3 = Kondoh | first3 = T | last4 = Torii | first4 = K. | year = 2009 | title = Conditioned flavor preference learning by intragastric administration of L-glutamate in rats | journal = Neurosci. Lett. | volume = 451 | issue = 3| pages = 190–3 | doi = 10.1016/j.neulet.2008.12.054 | pmid = 19146916 | s2cid = 21764940 }}</ref> and this information is passed to the [[lateral hypothalamus]] and [[limbic system]] in the [[brain]] as a [[palatability]] signal through the [[vagus nerve]].<ref>{{cite journal | last1 = Uematsu | first1 = A | last2 = Tsurugizawa | first2 = T | last3 = Uneyama | first3 = H | last4 = Torii | first4 = K. | year = 2010 | title = Brain-gut communication via vagus nerve modulates conditioned flavor preference | journal = Eur J Neurosci | volume = 31 | issue = 6| pages = 1136–43 | doi = 10.1111/j.1460-9568.2010.07136.x | pmid = 20377626 | s2cid = 23319470 }}</ref> The stomach can also sense, independently of tongue and oral taste receptors, [[glucose]],<ref name="Araujo">{{cite journal| pmid= 18367093 | doi=10.1016/j.neuron.2008.01.032| title= Food Reward in the Absence of Taste Receptor Signaling| year= 2008| last1= De Araujo| first1= Ivan E.| last2= Oliveira-Maia| first2= Albino J.| last3= Sotnikova| first3= Tatyana D.| last4= Gainetdinov| first4= Raul R.| last5= Caron| first5= Marc G.| last6= Nicolelis| first6= Miguel A.L.| last7= Simon| first7= Sidney A.| journal= Neuron| volume= 57| issue= 6| pages= 930–41| s2cid=47453450| doi-access= free}}</ref> [[carbohydrate]]s,<ref name="Perez">{{cite journal | last1 = Perez | first1 = C. | last2 = Ackroff | first2 = K. | last3 = Sclafani | first3 = A. | year = 1996 | title = Carbohydrate- and protein conditioned flavor preferences: effects of nutrient preloads | journal = Physiol. Behav. | volume = 59 | issue = 3| pages = 467–474 | doi = 10.1016/0031-9384(95)02085-3 | pmid = 8700948 | s2cid = 23422504 }}</ref>  [[protein]]s,<ref name="Perez"/> and [[fat]]s.<ref>{{cite journal | last1 = Ackroff | first1 = K. | last2 = Lucas | first2 = F. | last3 = Sclafani | first3 = A. | year = 2005 | title = Flavor preference conditioning as a function of fat source | journal = Physiol. Behav. | volume = 85 | issue = 4| pages = 448–460 | doi = 10.1016/j.physbeh.2005.05.006 | pmid = 15990126 | s2cid = 7875868 }}</ref> This allows the brain to link [[nutritional]] value of foods to their tastes.<ref name="Araujo"/>

;Thyrogastric syndrome  
This syndrome defines the association between thyroid disease and chronic gastritis, which was first described in the 1960s.<ref>{{cite journal |pages=605–25 |title=Autoimmunity in pernicious anemia and thyroiditis: a family study. |year=1965 |last1=Doniach  |first1=D. |last2=Roitt |first2=I.M. |last3=Taylor |first3=K.B. |journal=Ann N Y Acad Sci |volume=124 |issue=2 |pmid=5320499|doi=10.1111/j.1749-6632.1965.tb18990.x |bibcode=1965NYASA.124..605D |s2cid=39456072 }}</ref> This term was coined also to indicate the presence of thyroid autoantibodies or autoimmune thyroid disease in patients with pernicious anemia, a late clinical stage of atrophic gastritis.<ref>{{cite journal |pages=771–81 |title=An analysis of gastric parietal cell antibodies and thyroid cell antibodies in patients with pernicious anaemia and thyroid disorders. |year=1968 |last1=Cruchaud |first1=A. |last2=Juditz |first2=E.|journal=Clin Exp Immunol |volume=3|issue=8 |pmid=4180858|pmc=1578967 }}</ref> In 1993, a more complete investigation on the stomach and thyroid was published,<ref>{{cite journal |pages=17–23 |title=A new hypothesis: iodine and gastric cancer. |year=1993 |last1=Venturi |first1=S. |last2=Venturi |first2=A. |last3= Cimini |first3=D., Arduini, C; Venturi, M; Guidi, A.|journal=Eur J Cancer Prev|volume=2 |issue=1|pmid=8428171|doi=10.1097/00008469-199301000-00004 }}</ref> reporting that the thyroid is, embryogenetically and  phylogenetically, derived from a primitive stomach, and that the thyroid cells, such as primitive gastroenteric cells, migrated and specialized in uptake of iodide and in storage and elaboration of iodine compounds during vertebrate evolution. In fact, the stomach and thyroid share iodine-concentrating ability and many morphological and functional similarities, such as cell polarity and apical microvilli, similar organ-specific antigens and associated autoimmune diseases, secretion of glycoproteins (thyroglobulin and mucin) and peptide hormones, the digesting and readsorbing ability, and lastly, similar ability to form iodotyrosines by peroxidase activity, where iodide acts as an electron donor in the presence of H<sub>2</sub>O<sub>2</sub>. In the following years, many researchers published reviews about this syndrome.<ref>{{cite journal|title=Thyro-entero-gastric autoimmunity: Pathophysiology and implications for patient management. A review.|year=2019 |last1=Lahner|first1=E. |last2=Conti |first2=L. |last3=Cicone |first3=F. ; Capriello, S; Cazzato, M; Centanni, M; Annibale, B; Virili, C.|journal=Best Pract Res Clin Endocrinol Metab |volume=33 |issue=6 |pages=101373 |pmid=31864909|doi=10.1016/j.beem.2019.101373 |s2cid=209446096 }}</ref>

==Clinical significance==
[[File:Stomach endoscopy 1.jpg|thumb|An [[endoscopy]] of a normal stomach of a healthy 65-year-old woman]]
[[File:Fundic gland polyposis0001.jpg|thumb|Endoscopic image of a fundic gland [[polyp (medicine)|polyp]]]]

===Diseases===
{{Main article|Stomach disease}}
A [[Upper gastrointestinal series|series of radiographs]] can be used to examine the stomach for various disorders. This will often include the use of a [[Upper gastrointestinal series|barium swallow]]. Another method of examination of the stomach, is the use of an [[endoscopy|endoscope]]. A [[gastric emptying study]] is considered the gold standard to assess the gastric emptying rate.<ref>{{cite journal|last1=Masaoka|first1=Tatsuhiro|last2=Tack|first2=Jan|title=Gastroparesis: Current Concepts and Management|journal=Gut and Liver|date=30 September 2009|volume=3|issue=3|pages=166–173|doi=10.5009/gnl.2009.3.3.166|pmc=2852706|pmid=20431741}}</ref>

A large number of studies have indicated that most cases of [[peptic ulcer]]s, and [[gastritis]], in humans are caused by ''[[Helicobacter pylori]]'' infection, and an association has been seen with the development of [[stomach cancer]].<ref name="Brown">{{cite journal|last1=Brown|first1=LM|title=Helicobacter pylori: epidemiology and routes of transmission|journal=Epidemiologic Reviews|date=2000|volume=22|issue=2|pages=283–97|pmid=11218379|doi=10.1093/oxfordjournals.epirev.a018040|doi-access=free}}</ref>

A [[stomach rumble]] is actually noise from the intestines.

===Surgery===
In humans, many [[bariatric surgery]] procedures involve the stomach, in order to lose weight. A [[Adjustable gastric band|gastric band]] may be placed around the cardia area, which can adjust to limit intake. The [[Sleeve gastrectomy|anatomy of the stomach may be modified]], or the stomach may be [[Gastric bypass surgery|bypassed entirely]].

Surgical removal of the stomach is called a [[gastrectomy]], and removal of the cardia area is a called a '''cardiectomy'''.  "Cardiectomy" is a term that is also used to describe the removal of the [[heart]].<ref>[http://dictionary.reference.com/browse/cardiectomy cardiectomy] at dictionary.reference.com</ref><ref Name="BARLOW">{{cite journal  | author =Barlow, O. W. | title =The survival of the circulation in the frog web after cardiectomy  | journal =Journal of Pharmacology and Experimental Therapeutics | volume = 35| issue = 1 | pages = 17–24 | year=1929  | url =http://jpet.aspetjournals.org/cgi/content/abstract/35/1/17  | access-date = February 24, 2008 }}</ref><ref Name="MELTZER">{{cite journal | title =The effect of strychnin in cardiectomized frogs with destroyed lymph hearts; a demonstration | journal = Proceedings of the Society for Experimental Biology and Medicine| volume =10  | issue =2  | year =1913  | pages =23–24 | doi = 10.3181/00379727-10-16| last1 =Meltzer  | first1 =S. J.  | s2cid = 76506379| url = https://zenodo.org/record/1450222}}</ref> A gastrectomy may be carried out because of gastric cancer or severe perforation of the stomach wall.

[[Nissen fundoplication|Fundoplication]] is stomach surgery in which the fundus is wrapped around the lower esophagus and stitched into place.  It is used to treat [[Gastroesophageal reflux disease|gastroesophageal reflux disease (GERD)]].<ref name=Minjarez06>{{cite journal |first1=Renee C. |last1=Minjarez |first2=Blair A. |last2=Jobe |title=Surgical therapy for gastroesophageal reflux disease. |journal=GI Motility Online |year=2006 |url=http://www.nature.com/gimo/contents/pt1/full/gimo56.html |doi=10.1038/gimo56|doi-broken-date=1 November 2024 }}</ref>

===Etymology===
The word ''stomach'' is derived from [[Ancient Greek|Greek]] ''stomachos'' ({{lang|el|στόμαχος}}), ultimately from ''stoma'' ({{lang|el|στόμα}}) 'mouth'.<ref>{{cite book|author=Simpson, J. A. |title=The Oxford English dictionary|url=https://archive.org/details/oxfordenglishdic12simp |url-access=registration |date=1989|publisher=Clarendon Press|location=Oxford|isbn=9780198611868|edition=2nd|at=Stomach}}</ref> ''Gastro-'' and ''gastric'' (meaning 'related to the stomach') are both derived from Greek ''gaster'' ({{lang|el|γαστήρ}}) 'belly'.<ref>[http://classic.studylight.org/lex/grk/view.cgi?number=1064 gasth/r]. The New Testament Greek Lexicon</ref><ref>[http://dictionary.reference.com/browse/gaster?r=75&src=ref&ch=dic gaster]. dictionary.reference.com</ref><ref>{{cite book|author=Simpson, J. A. |title=The Oxford English dictionary|url=https://archive.org/details/oxfordenglishdic12simp |url-access=registration |date=1989|publisher=Clarendon Press|location=Oxford|isbn=9780198611868|edition=2nd|at=Gastro, Gastric}}</ref>

==Other animals==
Although the precise shape and size of the stomach varies widely among different vertebrates, the relative positions of the esophageal and duodenal openings remain relatively constant. As a result, the organ always curves somewhat to the left before curving back to meet the pyloric sphincter. However, [[lamprey]]s, [[hagfish]]es, [[chimaera]]s, [[lungfish]]es, and some [[teleost]] fish have no stomach at all, with the esophagus opening directly into the intestine. These animals all consume diets that require little storage of food, no predigestion with gastric juices, or both.<ref name=VB>{{cite book |author=Romer, Alfred Sherwood|author2=Parsons, Thomas S.|year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, PA|pages= 345–349|isbn= 978-0-03-910284-5}}</ref>

{|
|-
| [[File:Mammalian Stomachs remake.png|thumb|upright=1.50|Comparison of stomach glandular regions from several mammalian species. Frequency of glands may vary more smoothly between regions than is diagrammed here.  Asterisk (ruminant) represents the omasum, which is absent in [[Tylopoda]] (Tylopoda also have some cardiac glands opening onto ventral [[Reticulum (anatomy)|reticulum]] and [[rumen]]<ref>{{cite book|url=https://books.google.com/books?id=gvt_qSsLobUC&q=tylopoda+omasum&pg=PA350|title=Functional Anatomy and Physiology of Domestic Animals|author=William O. Reece|isbn=978-0-7817-4333-4|year=2005|publisher=Wiley }}</ref>)  Many other variations exist among the mammals.<ref>{{cite web |url=http://www.cnsweb.org/digestvertebrates/WWWEdStevensCDAnatomy.html |archive-url=https://web.archive.org/web/20081201045413/http://www.cnsweb.org/digestvertebrates/WWWEdStevensCDAnatomy.html |url-status=dead |archive-date=2008-12-01 |title=Digestive System of Vertebrates |author1=Finegan, Esther J. |author2=Stevens, C. Edward |name-list-style=amp }}</ref><ref>{{cite web|url=http://www.onemedicine.tuskegee.edu/DigestiveSystem/Stomach/Stomach_Ruminants.html|archive-url=https://web.archive.org/web/20101130085507/http://www.onemedicine.tuskegee.edu/DigestiveSystem/Stomach/Stomach_Ruminants.html|url-status=dead|archive-date=2010-11-30|title=The anatomy of the digestive system|author=Khalil, Muhammad|website=onemedicine.tuskegee.edu}}</ref>]]
| style="padding-left:1em;" |
;<span style="color:#E2E200;">Yellow</span>: [[Oesophagus|Esophagus]]
;<span style="color:#00AD00;">Green</span>: [[Oesophageal (nonglandular) region|Esophageal (nonglandular) region]].<ref name=APFA>{{cite book |author=Wilke, W. L.  |author2=Fails, A. D.|author3= Frandson, R. D.|year=2009 |title=Anatomy and physiology of farm animals |publisher=Wiley-Blackwell |location= Ames, Iowa|pages= 346|isbn= 978-0-8138-1394-3}}</ref>
;<span style="color:#A700C3;">Purple</span>: [[Cardiac gland region]].<ref name=APFA/>
;<span style="color:#C70000;">Red</span>: [[Fundic gland region]].<ref name=APFA/>
;<span style="color:#247AFF;">Blue</span>: [[Pyloric gland region]].<ref name=APFA/>
;<span style="color:#2A2AFF;">Dark blue</span>: [[Duodenum]]
|}
The gastric lining is usually divided into two regions, an anterior portion lined by fundic glands and a posterior portion lined with pyloric glands. Cardiac glands are unique to [[mammal]]s, and even then are absent in a number of species. The distributions of these glands vary between species, and do not always correspond with the same regions as in humans. Furthermore, in many non-human mammals, a portion of the stomach anterior to the cardiac glands is lined with epithelium essentially identical to that of the esophagus. [[Ruminant]]s, in particular, have a complex four-chambered stomach. The first three chambers ([[rumen]], [[Reticulum (anatomy)|reticulum]], and [[omasum]]) are all lined with esophageal mucosa,<ref name=VB/> while the final chamber functions like a [[monogastric]] stomach, which is called the [[abomasum]].

In [[bird]]s and [[crocodilian]]s, the stomach is divided into two regions. Anteriorly is a narrow tubular region, the [[proventriculus]], lined by fundic glands, and connecting the true stomach to the [[crop (anatomy)|crop]]. Beyond lies the powerful muscular [[gizzard]], lined by pyloric glands, and, in some species, containing stones that the animal swallows to help grind up food.<ref name=VB/>

In [[insect]]s, there is also a crop. The insect stomach is called the [[insect#Midgut|midgut]].

Information about the stomach in [[echinoderm]]s or [[mollusc]]s can be found under the respective articles.

==Additional images==
<gallery>
Image:Gray532.png|Image showing the celiac artery and its branches
File:An open stomach.jpg|A human stomach at autopsy showing the many [[Gastric folds|folds]] ([[rugae]])
File:3D Medical Animation Stomach Structure.jpg|High-quality image of the stomach
</gallery>

== See also ==
{{Commons}}
* [[Gastroesophageal reflux disease]]
* [[Gastric microbiota]]
* [[Proton-pump inhibitor]]

== References ==
{{Reflist}}

== External links ==
{{Wiktionary}}
* [https://www.proteinatlas.org/humanproteome/stomach Stomach] at the Human Protein Atlas
* [https://web.archive.org/web/20070310213747/http://www.med.uiuc.edu/m1/biochemistry/TA%20reviews/sam/AminoAcids.htm Digestion of proteins in the stomach or tiyan]  (archived 10 March 2007)
* [https://web.archive.org/web/20091027033803/http://uk.geocities.com/bacterial_ed/bacteria_and_food.htm  Site with details of how ruminants process food] (archived 27 October 2009)
* [http://www.partone.lifeinthefastlane.com/control_of_gastric_emptying.html Control of Gastric Emptying] ({{Webarchive|url=https://web.archive.org/web/20191112051823/http://www.partone.lifeinthefastlane.com/control_of_gastric_emptying.html |date=2019-11-12 }})

{{Human regional anatomy}}
{{Digestive tract}}
{{Authority control}}

[[Category:Stomach| ]]
[[Category:Abdomen]]
[[Category:Digestive system]]
[[Category:Organs (anatomy)]]