Stomach

This image illustrates the anatomy of the human stomach and its connections to adjacent parts of the digestive system. The stomach is shown with the esophagus entering from the top and the duodenum leading out from the bottom right. The cardia is the area around the opening where the esophagus meets the stomach. Above the cardia is the fundus, the rounded upper portion of the stomach, which often contains trapped air and can be seen on an x-ray.

The main body of the stomach is displayed with distinct muscle layers: the longitudinal layer, the circular layer, and the oblique layer. These muscular layers are responsible for the mechanical digestion of food through a process called peristalsis, which is the rhythmic contraction of stomach muscles to mix and propel food.

We see the internal surface of the stomach is marked by gastric folds, also known as rugae, which allow the stomach to stretch and expand when filled with food. The lesser curvature, the inner curve of the stomach, and the greater curvature, the outer curve, provide attachment points for the lesser and greater omentum, respectively — structures that help anchor the stomach to other digestive organs.

At the bottom of the stomach, there’s the pylorus, which acts as a gateway to the duodenum. The pyloric sphincter, a ring-like muscle, regulates the passage of partially digested food from the stomach to the duodenum. This control ensures that food moves in one direction and at an appropriate rate for further digestion and absorption in the small intestine.

The image provides a detailed overview of the human digestive system, highlighting the position of the stomach and a close-up view of the intestinal lining.

On the left, the silhouette of a human body shows the liver in red, situated just above the green gallbladder, and a complex network of the small intestine in pink below them. This visual is typical for depicting the anatomical positioning and relationship between these organs.

The middle part of the image zooms in on the stomach’s shape and position, indicating the direction of food passage with a black arrow. This section of the digestive system is where food is mechanically and chemically broken down by the stomach muscles and gastric juices.

On the right, we see an amplified section of the intestinal lining. This detailed illustration showcases the villi, which are small, finger-like projections that extend into the lumen of the intestine. The villi increase the internal surface area of the intestinal walls making absorption of nutrients more efficient. Each villus contains a network of capillaries and a lacteal, which are part of the lymphatic system. The capillaries absorb amino acids and simple sugars derived from proteins and carbohydrates, while the lacteals absorb fatty acids and glycerol resulting from fats. Beneath the villi, we can see the muscularis mucosa, which helps in moving the villi to maximize contact with digested food. The illustration vividly shows the layers of the intestinal wall, including the mucosa, submucosa, muscularis externa, and serosa, each with its distinct role in the function of the digestive tract.

This diagram illustrates the various sections of the human stomach, each highlighted in a different color for clarity. At the top, the esophagus is shown leading into the stomach, transitioning at the cardia, which is the section where the esophagus connects to the stomach. Just above the cardia is the fundus – the upper curved part which typically holds gases that are byproducts of digestion and can expand as the stomach fills.

The main central portion of the stomach is labeled as the body, which is the largest region and the primary digestive chamber where acids and enzymes break down food. Below the body, the stomach narrows into the pyloric antrum, a funnel-like structure that plays a significant role in mixing stomach contents and regulating the passage of food into the small intestine.

The pyloric canal is the narrow passage leading out of the stomach to the duodenum, the first part of the small intestine, shown in blue. The duodenum continues from the pylorus and is where the most chemical digestion takes place, aided by enzymes from the pancreas and bile from the gallbladder.

This visualization aids in understanding the stomach’s role in digestion, which includes the mechanical churning of food and the chemical breakdown via gastric juices. The different sections each contribute to the overall process of preparing food for nutrient absorption in the intestines.

The image depicts the vascular anatomy associated with the stomach, specifically the veins that drain blood away from the stomach. The network of veins is complex, indicating how blood is channeled from the stomach back to the heart.

At the top, we see the esophagus leading into the stomach at the gastroesophageal junction, near the fundus, the uppermost part of the stomach. The left gastric vein runs along the lesser curvature of the stomach, which is on the right side as we view the image, and is responsible for draining the blood from this region of the stomach into the portal vein. The portal vein is a significant vessel in the hepatic portal system, which carries blood from the gastrointestinal tract and spleen to the liver.

The right gastric vein parallels the left but along the lesser curvature’s opposite side. This vein also contributes to the blood flow into the portal vein. The splenic vein is shown traveling behind the stomach, collecting blood from the spleen and the short gastric veins along the fundus.

The greater curvature of the stomach, depicted on the left as we look at the image, is where the right gastro-omental vein runs. It drains the greater curvature’s right part and, together with the left gastro-omental vein (not shown in this image), is part of the venous drainage system of the stomach’s larger curve.

The inferior vena cava, one of the two largest veins in the human body, is presented behind the liver, and it carries deoxygenated blood from the lower half of the body to the heart.

This intricate venous network ensures that deoxygenated blood and nutrients absorbed by the stomach and intestines are effectively transported to the liver for processing, which is crucial for detoxification and metabolism before the blood is returned to the general circulation.

This image is an anatomical illustration of the stomach wall, detailing the different layers and components involved in its structure and function.

At the top layer, the mucosa is shown with gastric pits leading into the gastric glands. The mucous cells lining the surface produce mucus to protect the stomach lining from the acidic environment necessary for digestion.

Beneath the mucosa, there is the submucosa, which contains the submucosal nerve plexus. This nerve network plays a crucial role in regulating digestive secretions and reacting to the presence of food in the stomach.

Deeper still, we have the muscularis layer, which is composed of three sub-layers of muscle fibers: the inner oblique, the middle circular, and the outer longitudinal layers. These muscle layers are responsible for the stomach’s churning action, mixing the stomach contents with digestive juices, and moving food towards the small intestine.

At the very bottom, the serosa is the outermost layer of the stomach wall. It is composed of a thin layer of cells that secrete serous fluid, providing lubrication that reduces friction from muscle movements during digestion.

Within the muscularis layer, we can also see the myenteric nerve plexus, part of the enteric nervous system, which controls peristalsis and other reflexes within the gut.

The image also depicts the blood vessels, including arteries (in red) supplying oxygenated blood to the stomach, and veins (in blue) carrying deoxygenated blood away. Additionally, lymphatic vessels (also in blue but thinner) are shown, which are part of the immune system and help remove interstitial fluid from tissues.

This layered structure allows the stomach to perform its complex functions efficiently, from secretion of gastric juices for digestion to the muscular contractions for mechanical processing of food, all while being regulated by an intricate nerve network.

TermDefinition
AntrumThe lower portion of the stomach that grinds food and regulates emptying of the stomach contents into the duodenum.
Body of StomachThe main, central section of the stomach where the majority of digestion occurs.
CardiaThe section of the stomach where the esophagus connects to the stomach.
Circular MuscleMuscle fibers in the stomach wall that are oriented circumferentially and aid in digestion.
DuodenumThe first part of the small intestine immediately beyond the stomach.
EsophagusThe tube that connects the throat to the stomach, allowing food and liquids to enter the digestive system.
FundusThe upper part of the stomach that serves as a storage area for food and gases.
Gastric FoldsRidges on the internal stomach lining that allow for expansion as the stomach fills.
Gastric GlandsGlands located within the lining of the stomach that secrete stomach acid and enzymes for digestion.
Gastric PitIndentations in the stomach lining that lead into the gastric glands.
Greater CurvatureThe convex lateral surface of the stomach.
Inferior Vena CavaOne of the two main veins in the human body, carrying deoxygenated blood from the lower half of the body to the heart.
Lesser CurvatureThe concave medial surface of the stomach.
Longitudinal MuscleThe outer layer of stomach muscles that run lengthwise.
MucosaThe innermost layer of the stomach lining that contains the gastric glands.
Mucous CellsCells that produce mucus to protect the lining of the stomach.
Myenteric Nerve PlexusNetwork of nerves located between the layers of the muscularis, controlling gut motility.
Oblique MuscleThe innermost layer of stomach muscles that aid in the mechanical digestion of food.
Pyloric CanalThe passage connecting the stomach to the duodenum.
Pyloric SphincterA band of smooth muscle at the junction between the stomach and the duodenum.
SerosaThe outermost layer of the stomach wall that secretes serous fluid.
Splenic VeinA vein draining blood from the spleen and parts of the stomach to the portal vein.
SubmucosaThe layer of the stomach wall just outside the mucosa that contains nerves and blood vessels.
Submucosal Nerve PlexusNetwork of nerves within the submucosa that regulate digestive secretions and blood flow.
VilliFinger-like projections in the small intestine that increase the surface area for absorption.

The diagram presents a flowchart detailing the regulation of gastric secretion, which is a crucial part of the digestive process. The flowchart breaks down into two primary regulatory mechanisms: hormonal control and neural control.

Starting with gastric secretion, this process is shown to be inhibited by feedback from proteins. When proteins are present in the stomach, they trigger a response that reduces the secretion of gastrin, a hormone that stimulates the release of gastric juices. This feedback loop is part of the hormonal control pathway, which operates to regulate the digestive process based on the current content of the stomach, ensuring that the secretion of gastric acid is moderated to prevent damage to the stomach lining and to optimize digestion.

The hormonal control route, highlighted by the reduction of gastrin, is stimulated by the presence of proteins. In response to gastrin, the stomach is stimulated to secrete gastric juices, which are essential for the digestion of food.

On the other side, we see the neural control pathway. This pathway involves the vagus nerve, which stimulates the stomach to release gastric juices through vagal stimulation. However, when there is a decrease in neural signals, it implies a reduction in the stimulatory effect that the vagus nerve has on gastric secretion.

The flowchart converges on the stomach, showing its role in secreting gastric juices, which are instrumental in the digestion process. Ultimately, this process results in the digestion of food, breaking it down into absorbable nutrients and waste.

Medical students would benefit from understanding this diagram, as it clearly outlines the complex interplay between hormonal and neural factors in the regulation of gastric secretions, an essential concept in gastrointestinal physiology.

Practice Quiz