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Stomach

life science Maturity 9-11 Next article →

The stomach is a muscular, hollow organ within the upper gastrointestinal tract. It serves as a vital component of the digestive system in humans and many animals. In medical science, terms related to this organ often use the word "gastric." This comes from "gaster," the Ancient Greek name for the stomach. The organ is located in the left upper quadrant of the abdominal cavity. Its top edge rests against the diaphragm.

2414 Stomach
2414 Stomach

Digestion in the stomach follows a specific sequence of events. It begins with the cephalic phase, where the sight and smell of food act as stimuli. This is followed by the gastric phase, which occurs once food enters the organ. Inside, the stomach performs a chemical breakdown of food. It uses secreted digestive enzymes and gastric acid to process the meal. This process turns food into a substance called chyme.

Stomach emptying into duodenum
Stomach emptying into duodenum

The stomach is divided into four distinct anatomical sections. The first is the cardia, which is the small region surrounding the esophageal opening. Next is the fundus, a dome-shaped area at the upper curved part. The third section is the body, also known as the corpus, which is the large central region. Finally, the pylorus connects the stomach to the duodenum. The pylorus contains the pyloric antrum, which opens into the main body.

2414 Stomach
2414 Stomach

The structure of the stomach wall is quite complex. It consists of layers including the mucosa, submucosa, muscular layer, subserosa, and serosa. The innermost layer is the gastric mucosa, a mucous membrane. Beneath this lies the submucosa, which contains fibrous connective tissue. The muscular layer is unique because it contains three layers of muscle fibers. These are the inner oblique, middle circular, and outer longitudinal layers.

Gastrointestinal wall of human stomach hariadhi
Gastrointestinal wall of human stomach hariadhi

Each muscular layer performs a specific job to move food. The inner oblique layer is responsible for churning and physically breaking down food. This layer is distinct because it is not found in other parts of the digestive tract. The middle circular layer helps form the pyloric sphincter. This sphincter controls the movement of chyme into the duodenum. The outer longitudinal layer uses muscular shortening to move food toward the pylorus.

Layers of the GI Tract english
Layers of the GI Tract english

Tiny gastric glands within the mucosa are essential for chemical digestion. In the fundus and body, fundic glands contain specialized cells. Parietal cells in these glands secrete hydrochloric acid and intrinsic factor. Chief cells secrete pepsinogen, which becomes the enzyme pepsin in acidic conditions. Other cells secrete a protective layer of mucus and bicarbonate. Near the pylorus, pyloric glands secrete mucus and a hormone called gastrin.

Illu stomach layers
Illu stomach layers

The stomach's capacity and shape change based on its contents. When empty, the organ is somewhat J-shaped. When partially full, it takes on a pear-like shape. A newborn baby's stomach can only hold about 30 millilitres. An adult stomach normally expands to hold about one litre. However, the maximum volume in adults can reach 2 to 4 litres. In extreme circumstances, volumes of up to 15 litres have been observed.

Histology of normal fundic mucosa
Histology of normal fundic mucosa

Biology shows how much activity happens within this organ. Nearly 70% of the 20,000 protein-coding genes in human cells are expressed in the stomach. Many of these proteins help create the right environment for digestion. The stomach also relies on a complex blood supply. Arteries like the left gastric and right gastroepiploic arteries provide necessary nutrients. This network ensures the stomach can maintain its intense muscular and secretory work.

Stomach blood supply
Stomach blood supply
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🖼️ Images & Media (11)
File:2414 Stomach.jpg
2414 Stomach.jpg
File:Stomach blood supply.svg
Stomach blood supply.svg
File:Gastrointestinal wall of human stomach hariadhi.svg
Gastrointestinal wall of human stomach...
File:Layers of the GI Tract english.svg
Layers of the GI Tract english.svg
File:Illu_stomach_layers.jpg
Illu_stomach_layers.jpg
File:Histology of normal fundic mucosa.png
Histology of normal fundic mucosa.png
File:Histology of normal antral mucosa.png
Histology of normal antral mucosa.png
File:Stomach emptying into duodenum.svg
Stomach emptying into duodenum.svg
File:Stomach endoscopy 1.jpg
Stomach endoscopy 1.jpg
File:Fundic gland polyposis0001.jpg
Fundic gland polyposis0001.jpg
File:Mammalian Stomachs remake.png
Mammalian Stomachs remake.png
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