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The stomach is a muscular, hollow organ in the upper gastrointestinal tract of humans and many other animals. It is a large, stretchy bag that stores food and helps break it down during the gastric phase of digestion. The stomach is located between the oesophagus and the small intestine and can hold about 2 to 3 litres of food. The stomach has multiple muscle layers, including the inner oblique layer, which is responsible for food churning and mechanical digestion, the middle circular layer, and the outer longitudinal layer. These layers facilitate peristalsis, the vigorous movement of the stomach contents, and help move pre-digested food towards the small intestine. The abdominal muscles, located between the ribcage and pelvis, also play a role in digestion by holding organs in place and supporting the body during movement.
| Characteristics | Values |
|---|---|
| Location | Upper gastrointestinal tract of humans and many other animals |
| Function | Breaking down food, digestion, regulating gut microbiota, influencing digestion and overall health |
| Structure | Muscular, hollow organ with a dilated structure, 5 different cell types, multiple muscle layers, 4 sections |
| Capacity | 2 to 3 liters of food |
| Layers | Inner oblique, middle circular, outer longitudinal |
| Arterial supply | Celiac trunk, common hepatic artery, splenic artery, left gastric artery |
| Innervation | Sympathetic, arising from T5 to T9 spinal cord segments via the greater splanchnic nerve |
| Plexuses | Auerbach or myenteric plexus, Meissner or submucosal plexus |
| Muscle Tissue | Smooth muscle, thick and arranged in 3 layers |
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What You'll Learn
- The stomach is a muscular, hollow organ
- The stomach has multiple muscle layers
- The stomach's sympathetic innervation arises from the T5 to T9 spinal cord segments
- The stomach's inner oblique layer is responsible for food churning
- The pyloric sphincter controls the passage of food from the stomach to the duodenum
The stomach is a muscular, hollow organ
The stomach is a muscular bag that stores food and helps break it down. It can hold about 2 to 3 litres of food, acting as a blender and food reservoir. The stomach is the digestive system's most dilated portion. This organ lies between the oesophagus, which is superior to it, and the small intestine, which is inferior to it. The lower oesophageal sphincter at the top of the stomach regulates food passing from the oesophagus into the stomach and prevents the contents of the stomach from re-entering the oesophagus.
The stomach can be divided into four sections, beginning at the cardia, followed by the fundus, the body, and the pylorus. The gastric cardia is where the contents of the oesophagus empty from the gastro-oesophageal sphincter into the cardiac orifice, the opening into the gastric cardia. The fundus is formed in the upper curved part, and the body or corpus is the main, central region of the stomach. The pylorus opens to the body of the stomach and connects the stomach to the duodenum at the pyloric sphincter. The pyloric sphincter controls the passage of partially digested food from the stomach into the duodenum, the first and shortest part of the small intestine.
The stomach wall has multiple muscle layers to facilitate waves of brisk peristalsis for the second phase of digestion. The inner oblique layer is unique to the stomach and is primarily responsible for food churning and mechanical digestion. The middle circular layer is concentric with the stomach's longitudinal axis. This layer thickens in the pylorus region to form the pyloric sphincter, which regulates the output from the stomach into the duodenum. The outer longitudinal layer surrounds the middle layer. Contractions of the outer longitudinal layer facilitate food movement toward the pylorus.
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The stomach has multiple muscle layers
The stomach is a muscular, hollow organ in the upper gastrointestinal tract of humans and many other animals. It is a highly mobile and distensible organ with a rich blood supply. The stomach has a dilated structure and functions as a vital organ in the digestive system. It takes in food from the food pipe, mixes it, and breaks it down with the help of digestive enzymes and gastric acid. The stomach is also involved in regulating gut microbiota, which influences digestion and overall health.
Beneath the mucosa lies the submucosa, consisting of fibrous connective tissue. The submucosa includes Meissner's plexus, which is situated within the submucosal layer and regulates local blood flow and gastric secretion. Outside of the submucosa lies the muscular layer, which consists of three layers of muscular fibres: the inner oblique, middle circular, and outer longitudinal layers. The middle circular layer thickens in the pylorus region to form the pyloric sphincter, which regulates the output from the stomach into the duodenum. The Auerbach or myenteric plexus is a network of neurons located between the longitudinal and circular layers of the gastrointestinal tract's muscularis externa.
The stomach contains the thickest muscular layer consisting of three layers, allowing for maximum peristalsis. The muscle layer is made up of three sub-layers that each pull the stomach in different directions, moving the contents of the stomach around and facilitating digestion. These muscle layers also move the pre-digested food towards the small intestine once it is ready for passage.
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The stomach's sympathetic innervation arises from the T5 to T9 spinal cord segments
The stomach is a large, muscular, and hollow organ with a great capacity to hold food. It is a highly mobile and distensible organ with a rich blood supply. The stomach has multiple muscle layers to facilitate waves of brisk peristalsis for the second phase of digestion. The inner oblique layer is unique to the stomach and is primarily responsible for food churning and mechanical digestion. The middle circular layer thickens in the pylorus region to form the pyloric sphincter, which regulates the output from the stomach into the duodenum. The outer longitudinal layer surrounds the middle layer, and its contractions facilitate food movement toward the pylorus.
Preganglionic fibres can pass through the sympathetic trunk without synapsing. These fibres are usually derived from the spinal cord levels T5 to L2/L3. Once they pass through the sympathetic trunk, they combine with fibres from other levels to form and exit the trunk as a splanchnic nerve. The splanchnic nerves synapse on a prevertebral ganglion, and the post-synaptic fibres then pass on to the abdomen and pelvic viscera via a visceral motor nerve plexus. The postganglionic compartment consists of postganglionic fibres travelling to effectors, and the number of postganglionic fibres is greater than preganglionic ones.
The sympathetic outflow to the skin includes cholinergic neurons innervating sweat glands (sudomotor neurons) and adrenergic neurons innervating blood vessels and hair follicles (vasoconstrictor and pilomotor neurons). The lumbar sympathetic ganglia, which receive innervation from T9-L1 preganglionic neurons, innervate the lower limb via branches of the lumbosacral plexus.
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The stomach's inner oblique layer is responsible for food churning
The stomach is a muscular organ with multiple muscle layers that facilitate digestion. The stomach wall is made of the same four layers as most of the rest of the alimentary canal, but with adaptations to the mucosa and muscularis for the stomach's unique functions. The muscularis in the stomach has three layers of muscle, including an inner oblique smooth muscle layer, which is unique to the stomach. This inner oblique layer enables the stomach to churn and mix food vigorously, aiding in the mechanical breakdown of food into smaller particles.
The stomach is a highly mobile and distensible organ with a rich blood supply. It has five different cell types functioning at high metabolic rates. The stomach's multiple muscle layers facilitate waves of brisk peristalsis for the second phase of digestion. The stomach participates in all digestive activities except ingestion and defecation. It secretes gastric juices that break down food and absorbs certain drugs, such as aspirin and some alcohol. The stomach begins the digestion of protein and continues the digestion of carbohydrates and fats.
The inner oblique layer of the stomach's muscularis is responsible for creating the motion that churns and physically breaks down food into smaller particles. This churning action is essential for mixing and mechanically breaking down food, aiding in the digestive process. The stomach can hold about 2 to 3 liters of food, acting as both a blender and a food reservoir.
The stomach wall is specifically adapted for the organ's functions. The epithelium, or innermost layer, is responsible for most digestive, absorptive, and secretory processes. The epithelium includes gastric pits that lead to gastric glands, which secrete gastric juice. These gastric juices contain enzymes such as hydrochloric acid, which activates the protein-digesting enzyme pepsin. Additionally, the stomach mucosa's epithelial lining consists of surface mucus cells, which secrete a protective coat of alkaline mucus. This mucus layer protects the stomach from self-digestion by neutralizing gastric acid.
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The pyloric sphincter controls the passage of food from the stomach to the duodenum
The stomach is a muscular bag that stores food and facilitates digestion. It has multiple muscle layers that enable peristalsis, a process that involves waves of brisk contractions to break down food and mix it with digestive juices.
The pyloric sphincter is a critical component of the digestive system, acting as a gateway between the stomach and the small intestine. It is a band of smooth muscle that connects the pylorus, a part of the stomach, to the duodenum, the first section of the small intestine. The duodenum is responsible for peristalsis, propelling partially digested food through the rest of the small intestine.
As the duodenum fills with food and digestive juices, it exerts pressure on the pyloric sphincter, causing it to close. This closure prevents the re-entry of partially digested food and juices into the stomach. The duodenum then uses peristalsis to move the contents through the rest of the small intestine. Once the duodenum empties, the pressure on the pyloric sphincter is relieved, allowing it to open again for the passage of more food from the stomach.
The proper functioning of the pyloric sphincter is crucial for maintaining the unidirectional flow of food and digestive juices through the digestive system. When the pyloric sphincter malfunctions, it can lead to digestive problems such as bile reflux and gastroparesis.
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Frequently asked questions
The stomach is a muscular, hollow organ in the upper gastrointestinal tract of humans and many other animals. It is a large, stretchy bag with a great capacity to hold food. The stomach has multiple muscle layers that facilitate digestion.
The stomach has three layers of muscle fibres, with fibres lying at angles to each other. These are the inner oblique layer, the middle circular layer, and the outer longitudinal layer. The inner oblique layer is unique to the stomach and is responsible for food churning and mechanical digestion.
The stomach is a vital organ in the digestive system. It takes in food from the food pipe, mixes it, and breaks it down with digestive enzymes and gastric acid. The stomach also plays a role in regulating gut microbiota, influencing digestion and overall health.
