| Stomach | |
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| The location of the stomach in the body. | |
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| Diagram from cancer.gov: * 1. Body of stomach * 2. A plane passing through the incisura angularis on the Lesser curvature and the upper limit of the opposed dilatation on the Greater curvature divides the stomach into an upper Fundus * 3. Anterior wall * 4. Greater curvature * 5. The greater curvature of the stomach is directed mainly forward and is four or five times as long as the Lesser curvature. Lesser curvature * 6. The lesser curvature of the stomach, extending between the Cardiac and Pyloric orifices forms the right or posterior border of the stomach Cardia * 9. The cardia (also known as Z-line or esophagogastric junction or gastroesophageal junction) is the anatomical term for the junction orifice of Pyloric sphincter * 10. The pylorus (from Greek πυλωρος = "gate guard" is the region of the Stomach that connects to the Duodenum. Pyloric antrum * 11. Pyloric antrum ( antrum, lesser cul-de-sac) is the initial portion of the pyloric part of the Stomach. Pyloric canal * 12. The pyloric canal, also known as the canalis pyloricus, is the opening between the Stomach and the Small intestine See also Angular notch * 13. Nearer the Pyloric end of the Stomach than its Cardiac end is a well-marked notch the angular incisure (or notch) which varies somewhat in Gastric canal * 14. Nearer the Pyloric end of the Stomach than its Cardiac end is a well-marked notch the angular incisure (or notch) which varies somewhat in Rugal folds Work of the United States Government | |
| Latin | Ventriculus |
| Gray's | subject #247 1161 |
| Nerve | celiac ganglia, vagus[1] |
| Lymph | celiac preaortic lymph nodes[2] |
| MeSH | Stomach |
| Dorlands/Elsevier | g_03/12386049 |
In anatomy, the stomach is a bean-shaped hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication. Rugae is a term used in Anatomy that refers to a series of ridges produced by folding of the wall of an organ. A work of the United States government, as defined by United States copyright law, is "a work prepared by an officer or employee of the U Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Gray's Anatomy the Respiratory apparatus ( Apparatus Respiratorius Respiratory system Respiratory apparatus A nerve is an enclosed cable-like bundle of peripheral Axons (the long slender projections of Neurons. The celiac ganglia are two large irregularly shaped masses of Nerve tissue in the upper Abdomen. The vagus nerve (ˈveɪˌgəs (VĀ-gəs (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired Cranial nerves, and is the The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. The preaortic lymph nodes lie in front of the Aorta, and may be divided into Celiac lymph nodes, Superior mesenteric lymph nodes, and Inferior mesenteric Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument Digestion is the breaking down of chemicals in the body into a form that can be absorbed The word stomach is derived from the Latin stomachus, which derives from the Greek word stomachos (στόμαχος). Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly The words gastro- and gastric (meaning related to the stomach) are both derived from the Greek word gaster (γαστήρ).
Contents |
Functions
The stomach is a highly acidic environment due to gastric acid production and secretion which produces a luminal pH range usually between 1 and 2 depending on the species, food intake, time of the day, drug use, and other factors. Gastric acid is one of the main Secretions of the Stomach, together with several Enzymes and Intrinsic factor. A lumen (Lat lūmen, an opening or light (pl lumina is the inside space or lining of a tubular structure such as an artery or intestine pH is the measure of the acidity or alkalinity of a Solution. Combined with digestive enzymes, such an environment is able to break down large molecules (such as from food) to smaller ones so that they can eventually be absorbed from the small intestine. Digestion enzymes are Enzymes that break down Polymeric Macromolecules into their smaller building blocks Food is any substance usually composed primarily of Carbohydrates Fats water and/or Proteins that can be eaten or drunk by an In Biology the small Intestine is the part of the Gastrointestinal tract (gut between the Stomach and the Large intestine, and comprises A zymogen called pepsinogen is secreted by chief cells and turns into pepsin under low pH conditions and is a necessity in protein digestion. A zymogen (or proenzyme) is an inactive Enzyme precursor. A zymogen requires a biochemical change (such as a Hydrolysis reaction revealing the Pepsin is a digestive Protease ( released by the chief cells in the Stomach that functions to degrade food Proteins into In general a chief cell (or a " Zymogenic cell" is a cell which releases a precursor Enzyme. Pepsin is a digestive Protease ( released by the chief cells in the Stomach that functions to degrade food Proteins into Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl [3]
The human stomach can produce and secrete about 2. 2 to 3 liters of gastric acid per day with basal secretion levels being typically highest in the evening. The litre or liter (see spelling differences) is a unit of Volume. The stomach can expand to hold between 2-4 liters of food. It is a temporary food storage area, and in the process of digestion, the food goes into the stomach first.
Absorption of vitamin B12 from the small intestine is dependent on conjugation to a glycoprotein called intrinsic factor which is produced by parietal cells of the stomach. Not to be confused with Peptidoglycan. Glycoproteins are proteins that contain Oligosaccharide chains ( Glycans) covalently attached Intrinsic factor is a Glycoprotein produced by the Parietal cells of the Stomach. Parietal cells (also called oxyntic cells) are the Stomach Epithelium cells that secrete Gastric acid and Intrinsic factor
Other functions include absorbing some ions, water, and some lipid soluble compounds such as alcohol, aspirin, and caffeine. Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon Aspirin, or acetylsalicylic acid (ASA (əˌsɛtɨlsælɨˌsɪlɨk ˈæsɨd is a Salicylate drug, often used as an Analgesic to relieve Caffeine is a bitter white crystalline Xanthine Alkaloid that acts as a Psychoactive Stimulant Drug and a mild Diuretic
Anatomy of the human stomach
The stomach lies between the esophagus and the duodenum (the first part of the small intestine). The esophagus or oesophagus (see American and British English spelling differences) sometimes known as the gullet, is an organ in In Anatomy of the Digestive system, the duodenum is a hollow jointed tube about 25-30 cm (10-12 in long connecting the Stomach to the Jejunum In Biology the small Intestine is the part of the Gastrointestinal tract (gut between the Stomach and the Large intestine, and comprises It is on the left side of the abdominal cavity. The abdominal cavity is the Body cavity of the human body (and animal bodies that holds the bulk of the viscera and which is located below (or inferior The top of the stomach lies against the diaphragm. For other types of diaphragm see Diaphragm. In the Anatomy of Mammals the thoracic diaphragm is a sheet of Muscle Lying beneath the stomach is the pancreas, and the greater omentum which hangs from the greater curvature. The pancreas is a Gland organ in the digestive and Endocrine system of Vertebrates. The greater omentum (also the great omentum, omentum majus, gastrocolic omentum, or epiploön) is a large fold of Peritoneum that
Two smooth muscle valves, or sphincters, keep the contents of the stomach contained. Smooth muscle is a type of non- Striated muscle, found within the Tunica media layer of large and small Arteries and Veins, the bladder They are the esophageal sphincter (found in the cardiac region) dividing the tract above, and the Pyloric sphincter dividing the stomach from the small intestine. The cardia (also known as Z-line or esophagogastric junction or gastroesophageal junction) is the anatomical term for the junction orifice of The pylorus (from Greek πυλωρος = "gate guard" is the region of the Stomach that connects to the Duodenum.
The stomach is surrounded by parasympathetic (stimulant) and orthosympathetic (inhibitor) plexuses (anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity and the motor activity of the muscles.
In humans, the stomach has a volume of about 50 mL when empty. After a meal, it generally expands to hold about 1 liter of food,[4] but can hold as much as 4 liters. When drinking milk it can expand to just under 6 pints, or 3. 4 liter. [5]
Sections
The stomach is divided into four sections, each of which has different cells and functions. The sections are:
| Cardia | Where the contents of the esophagus empty into the stomach. The cardia (also known as Z-line or esophagogastric junction or gastroesophageal junction) is the anatomical term for the junction orifice of |
| Fundus | Formed by the upper curvature of the organ. |
| Body or corpus | The main, central region. A plane passing through the incisura angularis on the Lesser curvature and the upper limit of the opposed dilatation on the Greater curvature divides the stomach into an upper |
| Pylorus or antrum | The lower section of the organ that facilitates emptying the contents into the small intestine. The pylorus (from Greek πυλωρος = "gate guard" is the region of the Stomach that connects to the Duodenum. In Biology, " Antrum " is a general term for a cavity or chamber which may have specific meaning in reference to certain organs or sites in the body |
Blood supply
The lesser curvature of the stomach is supplied by the right gastric artery inferiorly, and the left gastric artery superiorly, which also supplies the cardiac region. The right gastric artery (pyloric artery arises from the Common hepatic artery, above the Pylorus, descends to the pyloric end of the Stomach, and passes In Human anatomy, the left gastric artery arises from the Celiac artery, and runs along the superior portion of the Lesser curvature of the Stomach The greater curvature is supplied by the right gastroepiploic artery inferiorly and the left gastroepiploic artery superiorly. The right gastro-omental artery (or right gastroepiploic artery) runs from right to left along the Greater curvature of the Stomach, between the layers The left gastro-omental artery (or left gastroepiploic artery) the largest branch of the Splenic artery, runs from left to right about a finger’s breadth or more The fundus of the stomach, and also the upper portion of the greater curvature, are supplied by the short gastric artery. The short gastric arteries consist of from five to seven small branches which arise from the end of the Splenic artery, and from its terminal divisions
Histology of the human stomach
Layers
Like the other parts of the gastrointestinal tract, the stomach walls are made of the following layers, from outside to inside:
| mucosa | The first main layer. The mucous membranes (or mucosae; singular mucosa) are linings of mostly endodermal origin covered in Epithelium, which are involved in This consists of an epithelium, the lamina propria underneath, and a thin layer of smooth muscle called the muscularis mucosae. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The lamina propria is a constituent of the moist linings known as mucous membranes or Mucosa, which line various tubes in the body (such as the respiratory tract the gastrointestinal Smooth muscle is a type of non- Striated muscle, found within the Tunica media layer of large and small Arteries and Veins, the bladder The lamina muscularis mucosae (or "muscularis mucosa" is the thin layer of Smooth muscle found in most parts of the Gastrointestinal tract, located |
| submucosa | This layer lies under the mucosa and consists of fibrous connective tissue, separating the mucosa from the next layer. In the Gastrointestinal tract, the submucosa is the layer of Loose connective tissue that supports the Mucosa, as well as joins the mucosa to the bulk In Zootomy, fibrous connective tissue ( FCT) is a type of Connective tissue which has relatively high Tensile strength, due to a relatively high The Meissner's plexus is in this layer. The nerves of the Small intestines are derived from the plexuses of Parasympathetic nerves around the Superior mesenteric artery. |
| muscularis externa | Under the submucosa, the muscularis externa in the stomach differs from that of other GI organs in that it has three layers of smooth muscle instead of two. The muscular coat ( muscular layer, muscular fibers, muscularis propria, muscularis externa) is a region of Muscle in many organs Smooth muscle is a type of non- Striated muscle, found within the Tunica media layer of large and small Arteries and Veins, the bladder
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| serosa | This layer is under the muscularis externa, consisting of layers of connective tissue continuous with the peritoneum. In Anatomy, a serous membrane (or serosa) is a smooth membrane consisting of a thin layer of cells which excrete Serous fluid In higher Vertebrates the peritoneum is the Serous membrane that forms the lining of the abdominal cavity &mdash it covers most of the intra-abdominal |
Glands
The epithelium of the stomach forms deep pits. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The glands at these locations are named for the corresponding part of the stomach:
| Cardiac glands (at cardia) | Pyloric glands (at pylorus) | Fundic glands (at fundus) |
 |  |  |
Different types of cells are found at the different layers of these glands:
| Layer of stomach | Name | Secretion | Region of stomach | Staining |
| Isthmus of gland | mucous cells | mucus gel layer | Fundic, cardiac, pyloric | Clear |
| Neck of gland | parietal (oxyntic) cells | gastric acid and intrinsic factor | Fundic, cardiac, pyloric | Acidophilic |
| Base of gland | chief (zymogenic) cells | pepsinogen, rennin | Fundic only | Basophilic |
| Base of gland | enteroendocrine (APUD) cells | hormones gastrin, histamine, endorphins, serotonin, cholecystokinin and somatostatin | Fundic, cardiac, pyloric | - |
Control of secretion and motility
The movement and the flow of chemicals into the stomach are controlled by both the autonomic nervous system and by the various digestive system hormones:
| Gastrin | The hormone gastrin causes an increase in the secretion of HCl, pepsinogen and intrinsic factor from parietal cells in the stomach. The cardiac glands of the Stomach secrete primarily Mucus. They are few in number and occur close to the Cardiac orifice where the Esophagus The cardia (also known as Z-line or esophagogastric junction or gastroesophageal junction) is the anatomical term for the junction orifice of The pyloric glands are found in the Pyloric portion of the Stomach. The pylorus (from Greek πυλωρος = "gate guard" is the region of the Stomach that connects to the Duodenum. The fundus glands (or fundic glands, or gastric glands) are found in the body and fundus of the Stomach. Goblet cells are Glandular simple columnar epithelial cells whose sole function is to secrete Mucus. In vertebrates mucus is a slippery secretion produced by and covering Mucous membranes It is a viscous Colloid containing Antiseptic enzymes (such as Parietal cells (also called oxyntic cells) are the Stomach Epithelium cells that secrete Gastric acid and Intrinsic factor Gastric acid is one of the main Secretions of the Stomach, together with several Enzymes and Intrinsic factor. Intrinsic factor is a Glycoprotein produced by the Parietal cells of the Stomach. A Gastric chief cell (or peptic cell, or gastric zymogenic cell) is a cell in the Stomach that releases Pepsinogen, gastric lipase and Pepsin is a digestive Protease ( released by the chief cells in the Stomach that functions to degrade food Proteins into Chymosin (or rennin) is an aspartic acid protease Enzyme found in Rennet. Basophilic is a technical term used by histologists. It describes the microscopic appearance of cells and tissues as seen down the Microscope, Enteroendocrine cells are specialized Endocrine cells of the Gastrointestinal tract. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body &trade The autonomic nervous system ( ANS) (or visceral nervous system) is the part of the Peripheral nervous system that acts as a Control Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body In humans gastrin is a Hormone that stimulates secretion of Gastric acid (HCl by the Parietal cells of the Stomach, as well as aiding in Intrinsic factor is a Glycoprotein produced by the Parietal cells of the Stomach. Parietal cells (also called oxyntic cells) are the Stomach Epithelium cells that secrete Gastric acid and Intrinsic factor It also causes increased motility in the stomach. Gastrin is released by G-cells in the stomach to distenstion of the antrum, and digestive products. In Anatomy, the G cell is a type of cell in the stomach that secretes Gastrin. It is inhibited by a pH normally less than 4 (high acid), as well as the hormone somatostatin. pH is the measure of the acidity or alkalinity of a Solution. Somatostatin (also known as growth hormone inhibiting hormone ( GHIH) or somatotropin release-inhibiting factor ( SRIF) is a Peptide hormone |
| Cholecystokinin | Cholecystokinin (CCK) has most effect on the gall bladder, but it also decreases gastric emptying and increases release of pancreatic juice which is alkaline and neutralizes the chyme. Cholecystokinin ( CCK; from Greek chole, "bile" cysto, "sac" kinin, "move" hence move the bile-sac The gallbladder (or cholecyst sometimes gall bladder is a small organ whose function in the body is to store Bile and aid in the digestive process |
| Secretin | In a different and rare manner, secretin, produced in the small intestine, has most effects on the pancreas, but will also diminish acid secretion in the stomach. Secretin is a Peptide hormone produced in the S cells of the Duodenum in the Crypts of Lieberkühn. |
| Gastric inhibitory peptide | Gastric inhibitory peptide (GIP) decreases both gastric acid and motility. Gastric inhibitory polypeptide ( GIP) also known as the glucose-dependent insulinotropic peptide is a member of the secretin family of Hormones |
| Enteroglucagon | enteroglucagon decreases both gastric acid and motility. Enteroglucagon is a Peptide Hormone derived from Preproglucagon. |
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 only to push food into the small intestine when the intestine is not busy. While the intestine is full and still digesting food, the stomach acts as storage for food.
Diseases of the stomach
Historically, it was widely believed that the highly acidic environment of the stomach would keep the stomach immune from infection. Gastropathy is a general term used for Stomach disease. Examples including the name include Portal hypertensive gastropathy An infection is the detrimental Colonization of a host Organism by a foreign Species. However, a large number of studies have indicated that most cases of stomach ulcers, gastritis, and stomach cancer are caused by Helicobacter pylori infection. Gastritis is an inflammation of the lining of the stomach There are many possible causes Stomach or gastric cancer can develop in any part of the Stomach and may spread throughout the stomach and to other organs particularly the Esophagus and Helicobacter pylori ( is a Gram-negative, microaerophilic Bacterium that inhabits various areas of the stomach and Duodenum.
References
- ^ Physiology at MCG 6/6ch2/s6ch2_30
- ^ Norman/Georgetown stomach
- ^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. The Medical College of Georgia, also known as MCG, is a public medical Research university located in downtown Augusta Georgia. Georgetown University is a Jesuit Private university located in Georgetown Washington D Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1.
- ^ Sherwood, Lauralee (1997). Human physiology: from cells to systems. Belmont, CA: Wadsworth Pub. Co. ISBN 0314092455.
- ^ Miller, Leslie W. ; Saladin, Kenneth S. (2004). Anatomy & physiology: the unity of form and function. Boston: McGraw-Hill Higher Education. ISBN 0-07-242903-8.
- ^ Anne M. R. Agur; Moore, Keith L. . Essential Clinical Anatomy (Point (Lippincott Williams & Wilkins)). Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 078176274X. ; p. 150
External links
- Digestion of proteins in the stomach
- Site with details of how ruminants process food
- Interview with Dr. Jerome Groopman, Highlight at 2:30
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