Stomach | Definition, Function, Structure, Diagram, & Facts

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They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2024-10-29T00:00:00CDT" >Oct 29, 2024</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/science/stomach/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn border-2 ai-ask-button btn border-2 module-spacing btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400 p-10 ml-5"> Ask the Chatbot a Question </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Key People: </dt> <dd><a href="/biography/William-Beaumont" topicid="57700">William Beaumont</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/chyme" topicid="117464">chyme</a></dd> <dd><a href="/science/gastric-gland" topicid="226712">gastric gland</a></dd> <dd><a href="/science/pylorus" topicid="484656">pylorus</a></dd> <dd><a href="/science/gizzard" topicid="234488">gizzard</a></dd> <dd><a href="/science/parietal-cell" topicid="443583">parietal cell</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/stomach"> See all related content </a> </div> </div> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref281068"></span>stomach</strong>, saclike expansion of the digestive system, between the <a href="https://www.britannica.com/science/esophagus" class="md-crosslink " data-show-preview="true">esophagus</a> and the <a href="https://www.britannica.com/science/small-intestine" class="md-crosslink " data-show-preview="true">small intestine</a>; it is located in the <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="anterior" href="https://www.britannica.com/dictionary/anterior" data-type="EB">anterior</a> portion of the <a href="https://www.britannica.com/science/abdominal-cavity" class="md-crosslink autoxref " data-show-preview="true">abdominal cavity</a> in most vertebrates. The stomach serves as a temporary receptacle for storage and mechanical distribution of food before it is passed into the <a href="https://www.britannica.com/science/intestine" class="md-crosslink autoxref " data-show-preview="true">intestine</a>. In animals whose stomachs contain digestive glands, some of the chemical processes of <a href="https://www.britannica.com/science/digestion-biology" class="md-crosslink autoxref " data-show-preview="true">digestion</a> also occur in the stomach.</p><span class="marker MOD1 mod-inline"></span></section><span class="marker h2"></span><section data-level="1" id="ref230035"> <h2 class="h1">Humans</h2> <span class="marker PREMOD2 mod-inline"></span><div class="assemblies multiple medialist slider js-slider position-relative d-inline-flex align-items-center mw-100" data-type="other"><div class="slider-container js-slider-container overflow-hidden d-flex"><div class="rw-track d-flex align-items-center"><div class="position-relative rw-slide col-100 px-20 "><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="68634" data-asm-type="image"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/15/74315-050-94AB6078/layers-stomach-human-Structures-layer-muscle-oblique.jpg" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center media-overlay-link card-media" data-href="/media/1/567085/68634"><picture><source media="(min-width: 680px)" srcset="https://cdn.britannica.com/15/74315-050-94AB6078/layers-stomach-human-Structures-layer-muscle-oblique.jpg"><img src="https://cdn.britannica.com/15/74315-050-94AB6078/layers-stomach-human-Structures-layer-muscle-oblique.jpg?w=300" alt="structures of the human stomach" data-width="1600" data-height="1012" loading="eager"></picture><div class="position-absolute top-10 left-10 assembly-slide-tag rounded-lg">1 of 2</div><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" href="https://cdn.britannica.com/15/74315-050-94AB6078/layers-stomach-human-Structures-layer-muscle-oblique.jpg" data-href="/media/1/567085/68634">structures of the human stomach</a><span>The stomach has three layers of muscle: an outer longitudinal layer, a middle circular layer, and an inner oblique layer. The inner lining consists of four layers: the serosa, the muscularis, the submucosa, and the mucosa. The mucosa is densely packed with gastric glands, which contain cells that produce digestive enzymes, hydrochloric acid, and mucus.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div></figcaption></figure></div><div class="position-relative rw-slide col-100 px-20 "><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="194813" data-asm-type="video"><div class="md-assembly-wrapper card-media " data-type="video" video-id="179646"><a data-id="179646" class="gtm-assembly-link d-flex justify-content-center" style="--aspect-ratio: 16/9" href="/video/human-stomach-rumbles/-194813"><img src="https://cdn.britannica.com/46/179646-138-01D8C3ED/human-stomach-rumbles.jpg?w=800&h=450&c=crop" alt="Why does your stomach make noise?" loading="lazy"><script type="application/json"> { "sources": [ { "file" : "//content.jwplatform.com/manifests/EBVHJrUM.m3u8" } ], "image": "https://cdn.britannica.com/46/179646-138-01D8C3ED/human-stomach-rumbles.jpg" ,"tracks": [ { "file" : "//assets-jpcust.jwpsrv.com/tracks/zhxCQxPt", "label": "English" } ] ,"adfile": "//content.jwplatform.com/manifests/JBCOdZAa.m3u8" } </script><div class="btn btn-xl btn-white btn-circle position-absolute shadow" style="top: 50%; transform: translateY(-50%)"><em class="material-icons" data-icon="play_arrow"></em></div><div class="position-absolute top-10 left-10 assembly-slide-tag rounded-lg">2 of 2</div></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><span class="md-assembly-title font-weight-bold mr-5 d-inline font-sans-serif md-video-caption" video-control="179646">Why does your stomach make noise?</span><span>Learn why the human stomach rumbles.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div><a class="font-14 mt-10 d-inline-block" href="/science/stomach/images-videos">See all videos for this article</a></figcaption></figure></div></div></div><button disabled="true" class="prev-button js-prev-button position-absolute btn btn-circle shadow btn-lg btn-blue-dark m-20"><span class="material-icons" data-icon="keyboard_arrow_left"></span></button><button disabled="true" class="next-button js-next-button position-absolute btn btn-circle shadow btn-lg btn-blue-dark m-20"><span class="material-icons" data-icon="keyboard_arrow_right"></span></button></div><p class="topic-paragraph">The human stomach is subdivided into four regions: the fundus, an expanded area curving up above the cardiac opening (the opening from the stomach into the esophagus); the body, or intermediate region, the central and largest portion; the antrum, the lowermost, somewhat funnel-shaped portion of the stomach; and the <a href="https://www.britannica.com/science/pylorus" class="md-crosslink autoxref " data-show-preview="true">pylorus</a>, a narrowing where the stomach joins the small intestine. Each of the openings, the cardiac and the pyloric, has a <a href="https://www.britannica.com/science/sphincter-muscle" class="md-crosslink autoxref " data-show-preview="true">sphincter muscle</a> that keeps the neighbouring region closed, except when food is passing through. In this manner, food is enclosed by the stomach until ready for digestion.</p><span class="marker MOD2 mod-inline"></span> <span class="marker PREMOD3 mod-inline"></span><div class="assemblies"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="207473" data-asm-type="video"><div class="md-assembly-wrapper card-media " data-type="video" video-id="186973"><a data-id="186973" class="gtm-assembly-link d-flex justify-content-center" style="--aspect-ratio: 16/9" href="/video/bloating-meals-discomfort-heartburn/-207473"><img src="https://cdn.britannica.com/73/186973-138-37D2738B/bloating-meals-discomfort-heartburn.jpg?w=800&h=450&c=crop" alt="Why do people feel full after a big meal?" loading="lazy"><script type="application/json"> { "sources": [ { "file" : "//content.jwplatform.com/manifests/NS5aOP7K.m3u8" } ], "image": "https://cdn.britannica.com/73/186973-138-37D2738B/bloating-meals-discomfort-heartburn.jpg" ,"tracks": [ { "file" : "//assets-jpcust.jwpsrv.com/tracks/fU7y0FaS", "label": "English" } ] ,"adfile": "//content.jwplatform.com/manifests/hS2fl4aV.m3u8" } </script><div class="btn btn-xl btn-white btn-circle position-absolute shadow" style="top: 50%; transform: translateY(-50%)"><em class="material-icons" data-icon="play_arrow"></em></div></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><span class="md-assembly-title font-weight-bold mr-5 d-inline font-sans-serif md-video-caption" video-control="186973">Why do people feel full after a big meal?</span><span>Learn why eating large meals can cause bloating, heartburn, and discomfort.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div><a class="font-14 mt-10 d-inline-block" href="/science/stomach/images-videos">See all videos for this article</a></figcaption></figure></div></div><p class="topic-paragraph">The stomach has the ability to expand or contract depending upon the amount of food contained within it. When contracted, the interior walls form numerous folds (rugae), which disappear when the walls are distended. The thick mucous-membrane lining of the walls is densely packed with small <a href="https://www.britannica.com/science/gastric-gland" class="md-crosslink " data-show-preview="true">gastric gland</a>s; these <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="secrete" href="https://www.britannica.com/dictionary/secrete" data-type="EB">secrete</a> a mixture of enzymes and <a href="https://www.britannica.com/science/hydrochloric-acid" class="md-crosslink autoxref " data-show-preview="true">hydrochloric acid</a> that partly digest proteins and fats.</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/human-organs" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/27/165127-131-C4AB31BC/human-heart-illustration-X-ray-Myocardium-Anatomy-Aorta.jpg" alt="3d illustration human heart. Adult Anatomy Aorta Black Blood Vessel Cardiovascular System Coronary Artery Coronary Sinus Front View Glowing Human Artery Human Heart Human Internal Organ Medical X-ray Myocardium" class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-green">Britannica Quiz</div> <div class="font-weight-semi-bold mt-5">Human Organs</div> </div> </a><span class="marker MOD3 mod-inline"></span> <span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph">The stomach muscles are rarely inactive. Upon entry of food, they relax briefly, then begin to contract. Periodic contractions churn and knead food into a semifluid mixture called <a href="https://www.britannica.com/science/chyme" class="md-crosslink " data-show-preview="true">chyme</a>; rhythmical pumping (<span id="ref281069"></span><a href="https://www.britannica.com/science/peristalsis" class="md-crosslink " data-show-preview="true">peristaltic</a>) waves move food toward the pylorus and small intestine. Peristaltic contractions persist after the stomach empties and, increasing with time, may become painful. Such hunger pangs may also be related to the amount of sugar in the blood. If the level of sugar decreases significantly, hunger can be experienced without the stomach’s intervention.</p><span class="marker MOD4 mod-inline"></span> <span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">The absorption of food, water, and electrolytes by the stomach is practically negligible, but iron and highly fat-soluble substances such as alcohol and some drugs are absorbed directly. Secretions and movements of the stomach are controlled by the <a href="https://www.britannica.com/science/vagus-nerve" class="md-crosslink autoxref " data-show-preview="true">vagus nerve</a> and the sympathetic nervous system; emotional stress can alter normal stomach functions. Common stomach disorders include <a href="https://www.britannica.com/science/peptic-ulcer" class="md-crosslink " data-show-preview="true">peptic ulcer</a>, <a href="https://www.britannica.com/science/stomach-cancer" class="md-crosslink " data-show-preview="true">cancer</a>, and <a href="https://www.britannica.com/science/gastritis" class="md-crosslink " data-show-preview="true">gastritis</a>.</p><span class="marker MOD5 mod-inline"></span> <div class="mb-20"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="293683" data-asm-type="infogram"><div class="md-assembly-wrapper card-media " data-type="infogram"><script id="infogram_0__/DNSuZk1kpY58VZ5k7kz7" src="https://e.infogram.com/js/dist/embed.js?Itp" type="text/javascript" title="The Human Body"></script></div></figure></div></div> </section><span class="marker h3"></span><section data-level="1" id="ref6918"><h2 class="h1">Other animals</h2><span class="marker PREMOD7 mod-inline"></span><p class="topic-paragraph">The stomachs of some other animals differ considerably from that of humans; many have multiple-chambered organs or special <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="adaptations" href="https://www.merriam-webster.com/dictionary/adaptations" data-type="MW">adaptations</a>. The stomachs of cows and most cud-chewing (ruminant) animals are divided into four separate parts. Food is received first in the rumen, where <a href="https://www.britannica.com/science/mucus" class="md-crosslink autoxref " data-show-preview="true">mucus</a> is added and cellulose is broken down. Next, it goes back to the <a href="https://www.britannica.com/science/mouth-anatomy" class="md-crosslink autoxref " data-show-preview="true">mouth</a> to be thoroughly rechewed. When swallowed again, it is passed to the second and third chambers, the reticulum and omasum, where water is extracted and absorbed. The food then goes to a final chamber, the abomasum, to receive the digestive enzymes.</p><div class="module-spacing"> <DIV class="marketing-INLINE_SUBSCRIPTION marketing-content" data-marketing-id="INLINE_SUBSCRIPTION"><style> .student-promo-banner-wrapper { container-type: inline-size; margin-bottom: 15px; } @container (min-width: 475px) { .student-promo-banner { flex-direction: row; } .student-promo-banner-img-wrapper { margin-bottom: 0; margin-right: 10px; justify-content: flex-start; } .student-promo-banner-text-wrapper { text-align: left; margin-bottom: 0px; margin-left: 10px; } .student-promo-banner-button-wrapper { margin-right: 0; } }</style> <div class="student-promo-banner-wrapper"> <div class="student-promo-banner d-flex flex-column align-items-center bg-blue rounded p-20"> <div class="student-promo-banner-img-wrapper mb-20 mr-0 d-flex justify-content-center"> <img class="rounded" style="max-width: 100px; min-width: 80px" src="https://cdn.britannica.com/marketing/BlueThistle.webp" /> </div> <div class="student-promo-banner-text-wrapper ml-0 mb-10 text-center text-white"> <div class="h2 mb-10">Get Unlimited Access</div> <div class="h4 font-weight-semi-bold">Try Britannica Premium for free and discover more.</div> </div> <div class="student-promo-banner-button-wrapper d-flex justify-content-center align-items-center ml-auto mr-auto"> <a class="btn btn-m btn-orange" href="https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=black-friday-2024">Subscribe</a> </div> </div> </div> </DIV></div><span class="marker MOD7 mod-inline"></span><span class="marker PREMOD8 mod-inline"></span><p class="topic-paragraph">Birds have a three-chambered stomach: the first chamber, the crop, receives the food initially and either stores or begins to moisten and soften (macerate) it; the true stomach area adds digestive juices; and the <a href="https://www.britannica.com/science/gizzard" class="md-crosslink " data-show-preview="true">gizzard</a>, with its stones, or toothlike structures, grinds the food.</p><span class="marker MOD8 mod-inline"></span><span class="marker PREMOD9 mod-inline"></span><p class="topic-paragraph"><span id="ref281070"></span><a href="https://www.britannica.com/animal/rodent" class="md-crosslink " data-show-preview="true">Rodents</a> have only one stomach area, and many must eat their food twice before absorption takes place. Food is eaten and passed through the lower <a href="https://www.britannica.com/science/gastrointestinal-tract" class="md-crosslink autoxref " data-show-preview="true">digestive tract</a>, where it is coated with metabolites to help break it down. The fecal material is then re-eaten and mixed with additional food. Enzymes and water are removed from the once-passed material by the stomach and used to help <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="digest" href="https://www.britannica.com/dictionary/digest" data-type="EB">digest</a> new nutritional substances. Dry fecal pellets are finally excreted.</p><div class="one-good-fact-module"> </div><span class="marker MOD9 mod-inline"></span><span class="marker PREMOD10 mod-inline"></span><p class="topic-paragraph">The <span id="ref281071"></span><a href="https://www.britannica.com/animal/sea-star" class="md-crosslink " data-show-preview="true">starfish</a> can turn its stomach inside out and extrude it partly from the body to eat the soft contents of shelled animals such as clams. <span id="ref281072"></span><a href="https://www.britannica.com/animal/camel" class="md-crosslink " data-show-preview="true">Camels</a> and <span id="ref281073"></span><a href="https://www.britannica.com/animal/llama" class="md-crosslink " data-show-preview="true">llamas</a> can regurgitate their stomach contents and spit this material at approaching enemies. <span id="ref281074"></span><a href="https://www.britannica.com/animal/crayfish" class="md-crosslink " data-show-preview="true">Crayfish</a> produce stones of calcium salts in their stomach. These are stored until the <a href="https://www.britannica.com/animal/animal" class="md-crosslink autoxref " data-show-preview="true">animal</a> sheds its external shell, when the stones are reabsorbed by the stomach and used in forming a new shell.</p><span class="marker MOD10 mod-inline"></span><span class="md-signature"><a href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419">The Editors of Encyclopaedia Britannica</a></span></section><span class="md-signature">This article was most recently revised and updated by <a href="/editor/rick-livingston/12680385">Rick Livingston</a>.</span><span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article></div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":1,"pageId":567085,"pageLength":666,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/topic-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"D","adLeg":"D","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"MEDIUM","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Stomach | Definition, Function, Structure, Diagram, & Facts | Britannica