Stomach Anatomy

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Anatomy of the Stomach









Location and Vascular Supply

Location: Abdominal cavity.

Arterial Supply: Branches of the celiac plexus.

Venous Drainage:

  • Left gastric and right gastric veins.
  • Short gastric veins.
  • Left and right gastroomental veins.

Innervation:

  • Parasympathetic: Posterior and anterior trunks of the vagus nerve (CN X).
  • Sympathetic: Greater splanchnic nerve (T5-9); Enteric innervation.
  • Visceral afferents: Spinal ganglia of T5-9.

Lymphatic Drainage:

  • Gastroomental, pyloric, gastric nodes.
  • Nodes around the cardia.

Gastric Structure 

 

Mucosal Layer

  • Surface Epithelium: Characterized by simple columnar epithelium and numerous short gastric pits leading to the lumen.
  • Surface Mucous Cells: Uniformly cover the surface, protecting the stomach from self-digestion. Failure of these cells can result in ulcers.
  • Gastric Glands: Located beneath the pits, occupying most of the mucosal volume. Composed mainly of parietal cells (acid secretion) and chief cells (enzyme secretion).
  • Lamina Propria: Highly vascular, embraces each gland, separating individual glands but densely packed in the mucosa.

Submucosal Layer

  • Characteristics: Relatively unspecialized compared to other stomach layers.

Muscularis Externa

  • Composition: Thicker than in other parts of the digestive tract, with an additional oblique layer of smooth muscle fibers.
  • Structure: Multi-layered but often indistinct microscopically, with one layer usually cut in cross-section and others obliquely.
  • Pyloric Sphincter: An especially thick region of the muscularis externa, regulating passage to the duodenum.

Serosal Layer

  • Characteristics: Normally unremarkable, consistent with the rest of the digestive tract.

Gastric Pits and Gastric Glands

  • Gastric Pits: Tubular, mucous-secretory, considered indentations of the surface epithelium rather than glands. Each pit opens into several gastric glands.
  • Gastric Glands:
    • Fundic Glands: Comprised of parietal cells, chief cells, mucous neck cells, and stem cells.
    • Parietal Cells (Oxyntic Cells): Secretes acid by pumping chloride and hydrogen ions, plentiful in the middle mucosa.
    • Chief Cells: Secrete digestive enzymes, most plentiful in the deeper mucosa.
    • Mucous Neck Cells: Located in the upper region of the fundic glands, function unclear.
    • Stem Cells: Replenish gland cells and surface mucous cells, located near the gastric pits.

Microscopic Appearance of Fundic Glands

  • Organization: Appears jumbled or cord-like due to non-parallel, varying size and shape of the glands, and minimal free space in the glandular lumens.
  • Recognition: Predominant secretory cells (parietal and chief cells) identifiable by round, euchromatic nuclei. Chief cells dominate deep in the mucosa near the muscularis mucosae.
  • Lamina Propria: Contains capillaries nourishing the glands and supplying materials for secretion, recognized by densely heterochromatic, irregular, or flattened nuclei of its fibroblasts and endothelial cells.

Gross Anatomy of the Stomach

 

Main Regions

The stomach is anatomically segmented into four primary regions, each playing a distinctive role in the digestion process:

  1. Cardia

    • Description: The initial section where the esophagus meets the stomach.
    • Function: Acts as a transition zone from the esophagus and is responsible for preventing the reflux of stomach contents back into the esophagus.

  2. Fundus

    • Description: The uppermost part of the stomach, forming a dome-shaped region above the cardia.
    • Function: Serves as a storage area for ingested food and gases released during the digestion process.

  3. Body

    • Description: The largest and central portion of the stomach.
    • Function: Main site for mechanical digestion; the stomach walls mix the food with gastric juice, initiating the breakdown of food particles.

  4. Pylorus

    • Description: The lower segment of the stomach that connects to the duodenum of the small intestine.
    • Function: Regulates the passage of digested food from the stomach to the small intestine, ensuring proper digestion and absorption.

Arterial Supply of the Stomach

 

Origin

The arterial supply to the stomach primarily stems from the celiac trunk and its branches, which emanate from the abdominal aorta.

Main Arteries

  • Left Gastric Artery
    • Origin: Directly from the celiac trunk.
    • Supply Area: Supplies the lesser curvature of the stomach.
  • Right Gastric Artery
    • Origin: Branch of the proper hepatic artery, arising from the common hepatic artery.
    • Supply Area: Also targets the lesser curvature of the stomach.
  • Right Gastro-Omental (Gastroepiploic) Artery
    • Origin: Terminal branch of the gastroduodenal artery, arising from the common hepatic artery.
    • Supply Area: Supplies the greater curvature of the stomach.
  • Left Gastro-Omental (Gastroepiploic) Artery
    • Origin: Branch of the splenic artery, stemming from the celiac trunk.
    • Supply Area: Also supplies the greater curvature of the stomach.
  • Short Gastric Arteries
    • Origin: Branches of the splenic artery.
    • Supply Area: Supplies the fundus and upper part of the body of the stomach.

Anastomoses

  • Function: Form along the lesser and greater curvatures of the stomach, ensuring a comprehensive and rich blood supply.
  • Importance: This arrangement is vital for maintaining blood flow to specific areas of the stomach, especially crucial if an artery is occluded, a condition more prevalent in older patients.

Venous Drainage of the Stomach

 

Overview

The venous drainage of the stomach is a critical component of the circulatory system, channeling deoxygenated blood from the stomach to the liver via the portal venous system. This system plays a vital role in transporting nutrients and other substances for metabolic processing or storage in the liver.

Main Venous Pathways

  • Right and Left Gastric Veins
    • Path: Run parallel to the corresponding gastric arteries.
    • Drainage Area: Lesser curvature of the stomach.
    • Destination: Directly into the hepatic portal vein.
  • Short Gastric Veins
    • Path: Specifically drain the fundus and upper part of the stomach.
    • Destination: Drain into the splenic vein, which is a tributary of the portal vein.
  • Right and Left Gastro-Omental (Gastroepiploic) Veins
    • Path: Run parallel to the corresponding gastro-omental arteries.
    • Drainage Area: Greater curvature of the stomach.
    • Destination:
      • Right gastro-omental vein drains into the superior mesenteric vein.
      • Left gastro-omental vein drains into the splenic vein.

Convergence and Processing

  • Portal Vein: The convergence point for the gastric veins, channeling the blood to the liver.
  • Liver Processing: In the liver, blood undergoes processing where nutrients and substances absorbed from the gastrointestinal tract are metabolized or stored.
  • Systemic Circulation: Post-processing, the blood is drained into the systemic circulation through the hepatic veins, completing the circulation cycle.

Importance of the System

The venous drainage system is indispensable for the efficient transport of absorbed substances to the liver. It ensures that nutrients and other absorbed elements are properly metabolized and utilized by the body, maintaining metabolic homeostasis.

Lymphatic System of the Stomach in Gastric Cancer

 

Lymphatic Drainage Pathways

  • Upper Third of Stomach: Lymphatics spread along the left gastric artery, posterior gastric artery, splenic artery, and left inferior phrenic artery without connection to retro-pancreatic or mesenteric nodes (stations 13 and 14).
  • Lower Third of Stomach: Lymphatics channel along the common hepatic artery and superior mesenteric artery, draining into stations 12 and 13 (hepatoduodenal ligament nodes and retro-pancreatic nodes).
  • Final Drainage: Gastric lymphatic drains into lymph node station 16.

Lymphatic Axis Connections

  • Peri-gastric to Para-aortic Nodes: Four lymphatic axes connect the peri-gastric nodes with the para-aortic nodes:
    1. From the upper and middle part of the stomach via the left inferior phrenic artery to the left sub-diaphragmatic pedicle.
    2. From the upper and lower part of the stomach via the left gastric, splenic, and common hepatic arteries to the celiac pedicle.
    3. From the lower portion of the stomach via the infra-pyloric nodes to the superior mesenteric pedicle.
    4. From the lower portion of the stomach via retro-pyloric nodes to the retro-pancreatic pedicle.

Specific Node Stations and Gastric Cancer Metastasis

  • Lymph Node Metastasis: The likelihood of lymph node metastasis is closely related to the tumor’s location within the stomach and the degree of gastric wall invasion.
  • Upper Third Adenocarcinoma: Metastasis commonly involves nodes of station 1, 2, 3, 7, and 9. The splenic hilum nodes and para-aortic nodes are primarily infiltrated in upper gastric tumors.
  • Middle Third Adenocarcinoma: Metastasis often involves lymph node stations 1, 3, 4, and 6. Left gastric artery and coeliac trunk nodes are also commonly affected.
  • Lower Third Adenocarcinoma: Metastasis is frequently seen in nodes of station 3, 4, 6, 7, 8, and 9, with stations 8 and 9 being particularly prone to infiltration in T2–T3/4 cases.

Skip Metastasis

  • Phenomenon: Gastric adenocarcinoma can bypass contiguous nodes, spreading to distant lymphatic stations.
  • Common Sites: Skip metastasis often involves left gastric artery, common hepatic artery, and coeliac trunk nodes.
  • Statistics: Skip metastasis occurs in 5% to 14% of cases and involves stations 7 to 11 in 24% of cases, with hepatoduodenal ligament nodes and para-aortic nodes affected in about 1% of cases.

Implications for Treatment

Understanding the intricate lymphatic pathways and metastasis patterns of gastric cancer is vital for accurate staging, prognosis, and surgical planning. The pattern of lymphatic spread and potential skip metastasis significantly influences the strategy for lymph node dissection during surgical interventions for gastric cancer.

Innervation of the Stomach

 

The stomach’s innervation is a multifaceted system that coordinates its functions, including motility, secretion, and blood flow. This complex innervation involves the autonomic nervous system’s parasympathetic and sympathetic branches, as well as the intrinsic enteric nervous system.

Parasympathetic Innervation

  • Origin: Primarily from the anterior and posterior vagal trunks of the vagus nerve (CN X).
  • Distribution:
    • The anterior vagal trunk supplies parts of the anterior surface of the stomach and the pylorus.
    • The posterior vagal trunk innervates the remaining anterior surface and the entire posterior surface.
  • Functions:
    • Stimulates gastric secretion and motility.
    • Induces relaxation of the pyloric sphincter during gastric emptying.
    • Transmits sensory information like pain, fullness, and nausea from the stomach.

Sympathetic Innervation

  • Origin: From the celiac plexus, with nerve impulses coming from the fifth to twelfth thoracic spinal nerves (T5-T12).
  • Functions:
    • Inhibits gastric motility.
    • Constricts the pyloric sphincter, preventing gastric emptying.

Enteric Nervous System (ENS)

  • Components:
    • Myenteric (Auerbach’s) Plexus:
      • Location: Between the muscular layers of the stomach.
      • Function: Primarily regulates gastric motility.
    • Submucosal (Meissner’s) Plexus:
      • Location: In the submucosa layer.
      • Function: Primarily regulates enzyme secretion, blood flow, and ion transport within the stomach.

Summary

The innervation of the stomach is an intricate network that coordinates the complex digestive activities of the organ. The parasympathetic and sympathetic components of the autonomic nervous system, alongside the intrinsic enteric nervous system, collaboratively ensure the proper functioning of the stomach by finely tuning its motility, secretion, and various physiological processes. This sophisticated system exemplifies the dynamic nature of the gastrointestinal tract’s control mechanisms.

Anatomical Relations of the Stomach

 

Superior Relations

  • Oesophagus: Connects to the stomach at the cardia.
  • Left Dome of the Diaphragm: Sits just above the stomach, influencing its position and space in the abdominal cavity.

Anterior Relations

  • Diaphragm: Separates the thoracic cavity from the abdominal cavity, located just above the stomach.
  • Greater Omentum: A fatty apron that drapes over the stomach and other abdominal organs.
  • Anterior Abdominal Wall: Provides structural support and protection for the stomach and other abdominal organs.
  • Left Lobe of Liver: Overlaps the stomach, especially the fundus and upper part of the body.
  • Gall Bladder: Situated beneath the liver, in close proximity to the stomach.

Posterior Relations

  • Lesser Sac (Omental Bursa): A cavity behind the stomach that allows free movement and provides space for expansion.
  • Pancreas: Lies posterior to the stomach, with the body and tail extending towards the left.
  • Left Kidney and Left Adrenal Gland: Located posteriorly and slightly superior to the stomach.
  • Spleen: Positioned to the left of the stomach, connected by the lienorenal and gastrosplenic ligaments.
  • Splenic Artery: Runs along the superior border of the pancreas, supplying blood to the spleen, pancreas, and stomach.
  • Transverse Mesocolon: A fold of the peritoneum, attaching the transverse colon to the posterior abdominal wall, lying posterior to the stomach.

Sphincters of the Stomach

 

The stomach features two primary sphincters located at its entry and exit points. These sphincters play crucial roles in regulating the movement of materials into and out of the stomach, ensuring proper digestion and timing of nutrient processing.

Inferior Oesophageal Sphincter

  • Location: The oesophagus transitions to the stomach at the T11 level, after passing through the oesophageal hiatus in the diaphragm at the T10 level.
  • Function:
    • Marks the transition from the oesophagus to the stomach.
    • Allows the passage of food through the cardiac orifice into the stomach.
  • Control: Involuntary, not under direct conscious control.
  • Contrast with Superior Oesophageal Sphincter: The inferior oesophageal sphincter is situated at the stomach’s entrance, whereas the superior oesophageal sphincter is located in the pharynx.

Pyloric Sphincter

  • Location: Positioned between the pylorus of the stomach and the first part of the duodenum.
  • Function:
    • Controls the discharge of chyme (a mixture of partially digested food and gastric acid) from the stomach into the duodenum.
    • The sphincter remains contracted most of the time, ensuring food is retained in the stomach long enough for effective digestion.
  • Structure: An anatomical sphincter composed of smooth muscle.
  • Action:
    • Intermittent relaxation allows the stomach to empty its contents when intragastric pressure exceeds the resistance of the pylorus.
    • Gastric peristalsis aids in pushing chyme through the pyloric canal into the duodenum, where digestion continues.

The coordinated activity of these sphincters ensures a regulated digestive process, allowing for the sequential breakdown and absorption of nutrients while preventing issues such as reflux or premature passage of stomach contents.

Location and Vascular Supply

Location: Abdominal cavity.

Arterial Supply: Branches of the celiac plexus.

Venous Drainage:

  • Left gastric and right gastric veins.
  • Short gastric veins.
  • Left and right gastroomental veins.

Innervation:

  • Parasympathetic: Posterior and anterior trunks of the vagus nerve (CN X).
  • Sympathetic: Greater splanchnic nerve (T5-9); Enteric innervation.
  • Visceral afferents: Spinal ganglia of T5-9.

Lymphatic Drainage:

  • Gastroomental, pyloric, gastric nodes.
  • Nodes around the cardia.

Gastric Structure 

 

Mucosal Layer

  • Surface Epithelium: Characterized by simple columnar epithelium and numerous short gastric pits leading to the lumen.
  • Surface Mucous Cells: Uniformly cover the surface, protecting the stomach from self-digestion. Failure of these cells can result in ulcers.
  • Gastric Glands: Located beneath the pits, occupying most of the mucosal volume. Composed mainly of parietal cells (acid secretion) and chief cells (enzyme secretion).
  • Lamina Propria: Highly vascular, embraces each gland, separating individual glands but densely packed in the mucosa.

Submucosal Layer

  • Characteristics: Relatively unspecialized compared to other stomach layers.

Muscularis Externa

  • Composition: Thicker than in other parts of the digestive tract, with an additional oblique layer of smooth muscle fibers.
  • Structure: Multi-layered but often indistinct microscopically, with one layer usually cut in cross-section and others obliquely.
  • Pyloric Sphincter: An especially thick region of the muscularis externa, regulating passage to the duodenum.

Serosal Layer

  • Characteristics: Normally unremarkable, consistent with the rest of the digestive tract.

Gastric Pits and Gastric Glands

  • Gastric Pits: Tubular, mucous-secretory, considered indentations of the surface epithelium rather than glands. Each pit opens into several gastric glands.
  • Gastric Glands:
    • Fundic Glands: Comprised of parietal cells, chief cells, mucous neck cells, and stem cells.
    • Parietal Cells (Oxyntic Cells): Secretes acid by pumping chloride and hydrogen ions, plentiful in the middle mucosa.
    • Chief Cells: Secrete digestive enzymes, most plentiful in the deeper mucosa.
    • Mucous Neck Cells: Located in the upper region of the fundic glands, function unclear.
    • Stem Cells: Replenish gland cells and surface mucous cells, located near the gastric pits.

Microscopic Appearance of Fundic Glands

  • Organization: Appears jumbled or cord-like due to non-parallel, varying size and shape of the glands, and minimal free space in the glandular lumens.
  • Recognition: Predominant secretory cells (parietal and chief cells) identifiable by round, euchromatic nuclei. Chief cells dominate deep in the mucosa near the muscularis mucosae.
  • Lamina Propria: Contains capillaries nourishing the glands and supplying materials for secretion, recognized by densely heterochromatic, irregular, or flattened nuclei of its fibroblasts and endothelial cells.

Gross Anatomy of the Stomach

 

Main Regions

The stomach is anatomically segmented into four primary regions, each playing a distinctive role in the digestion process:

  1. Cardia

    • Description: The initial section where the esophagus meets the stomach.
    • Function: Acts as a transition zone from the esophagus and is responsible for preventing the reflux of stomach contents back into the esophagus.

  2. Fundus

    • Description: The uppermost part of the stomach, forming a dome-shaped region above the cardia.
    • Function: Serves as a storage area for ingested food and gases released during the digestion process.

  3. Body

    • Description: The largest and central portion of the stomach.
    • Function: Main site for mechanical digestion; the stomach walls mix the food with gastric juice, initiating the breakdown of food particles.

  4. Pylorus

    • Description: The lower segment of the stomach that connects to the duodenum of the small intestine.
    • Function: Regulates the passage of digested food from the stomach to the small intestine, ensuring proper digestion and absorption.

Arterial Supply of the Stomach

 

Origin

The arterial supply to the stomach primarily stems from the celiac trunk and its branches, which emanate from the abdominal aorta.

Main Arteries

  • Left Gastric Artery
    • Origin: Directly from the celiac trunk.
    • Supply Area: Supplies the lesser curvature of the stomach.
  • Right Gastric Artery
    • Origin: Branch of the proper hepatic artery, arising from the common hepatic artery.
    • Supply Area: Also targets the lesser curvature of the stomach.
  • Right Gastro-Omental (Gastroepiploic) Artery
    • Origin: Terminal branch of the gastroduodenal artery, arising from the common hepatic artery.
    • Supply Area: Supplies the greater curvature of the stomach.
  • Left Gastro-Omental (Gastroepiploic) Artery
    • Origin: Branch of the splenic artery, stemming from the celiac trunk.
    • Supply Area: Also supplies the greater curvature of the stomach.
  • Short Gastric Arteries
    • Origin: Branches of the splenic artery.
    • Supply Area: Supplies the fundus and upper part of the body of the stomach.

Anastomoses

  • Function: Form along the lesser and greater curvatures of the stomach, ensuring a comprehensive and rich blood supply.
  • Importance: This arrangement is vital for maintaining blood flow to specific areas of the stomach, especially crucial if an artery is occluded, a condition more prevalent in older patients.

Venous Drainage of the Stomach

 

Overview

The venous drainage of the stomach is a critical component of the circulatory system, channeling deoxygenated blood from the stomach to the liver via the portal venous system. This system plays a vital role in transporting nutrients and other substances for metabolic processing or storage in the liver.

Main Venous Pathways

  • Right and Left Gastric Veins
    • Path: Run parallel to the corresponding gastric arteries.
    • Drainage Area: Lesser curvature of the stomach.
    • Destination: Directly into the hepatic portal vein.
  • Short Gastric Veins
    • Path: Specifically drain the fundus and upper part of the stomach.
    • Destination: Drain into the splenic vein, which is a tributary of the portal vein.
  • Right and Left Gastro-Omental (Gastroepiploic) Veins
    • Path: Run parallel to the corresponding gastro-omental arteries.
    • Drainage Area: Greater curvature of the stomach.
    • Destination:
      • Right gastro-omental vein drains into the superior mesenteric vein.
      • Left gastro-omental vein drains into the splenic vein.

Convergence and Processing

  • Portal Vein: The convergence point for the gastric veins, channeling the blood to the liver.
  • Liver Processing: In the liver, blood undergoes processing where nutrients and substances absorbed from the gastrointestinal tract are metabolized or stored.
  • Systemic Circulation: Post-processing, the blood is drained into the systemic circulation through the hepatic veins, completing the circulation cycle.

Importance of the System

The venous drainage system is indispensable for the efficient transport of absorbed substances to the liver. It ensures that nutrients and other absorbed elements are properly metabolized and utilized by the body, maintaining metabolic homeostasis.

Lymphatic System of the Stomach in Gastric Cancer

 

Lymphatic Drainage Pathways

  • Upper Third of Stomach: Lymphatics spread along the left gastric artery, posterior gastric artery, splenic artery, and left inferior phrenic artery without connection to retro-pancreatic or mesenteric nodes (stations 13 and 14).
  • Lower Third of Stomach: Lymphatics channel along the common hepatic artery and superior mesenteric artery, draining into stations 12 and 13 (hepatoduodenal ligament nodes and retro-pancreatic nodes).
  • Final Drainage: Gastric lymphatic drains into lymph node station 16.

Lymphatic Axis Connections

  • Peri-gastric to Para-aortic Nodes: Four lymphatic axes connect the peri-gastric nodes with the para-aortic nodes:
    1. From the upper and middle part of the stomach via the left inferior phrenic artery to the left sub-diaphragmatic pedicle.
    2. From the upper and lower part of the stomach via the left gastric, splenic, and common hepatic arteries to the celiac pedicle.
    3. From the lower portion of the stomach via the infra-pyloric nodes to the superior mesenteric pedicle.
    4. From the lower portion of the stomach via retro-pyloric nodes to the retro-pancreatic pedicle.

Specific Node Stations and Gastric Cancer Metastasis

  • Lymph Node Metastasis: The likelihood of lymph node metastasis is closely related to the tumor’s location within the stomach and the degree of gastric wall invasion.
  • Upper Third Adenocarcinoma: Metastasis commonly involves nodes of station 1, 2, 3, 7, and 9. The splenic hilum nodes and para-aortic nodes are primarily infiltrated in upper gastric tumors.
  • Middle Third Adenocarcinoma: Metastasis often involves lymph node stations 1, 3, 4, and 6. Left gastric artery and coeliac trunk nodes are also commonly affected.
  • Lower Third Adenocarcinoma: Metastasis is frequently seen in nodes of station 3, 4, 6, 7, 8, and 9, with stations 8 and 9 being particularly prone to infiltration in T2–T3/4 cases.

Skip Metastasis

  • Phenomenon: Gastric adenocarcinoma can bypass contiguous nodes, spreading to distant lymphatic stations.
  • Common Sites: Skip metastasis often involves left gastric artery, common hepatic artery, and coeliac trunk nodes.
  • Statistics: Skip metastasis occurs in 5% to 14% of cases and involves stations 7 to 11 in 24% of cases, with hepatoduodenal ligament nodes and para-aortic nodes affected in about 1% of cases.

Implications for Treatment

Understanding the intricate lymphatic pathways and metastasis patterns of gastric cancer is vital for accurate staging, prognosis, and surgical planning. The pattern of lymphatic spread and potential skip metastasis significantly influences the strategy for lymph node dissection during surgical interventions for gastric cancer.

Innervation of the Stomach

 

The stomach’s innervation is a multifaceted system that coordinates its functions, including motility, secretion, and blood flow. This complex innervation involves the autonomic nervous system’s parasympathetic and sympathetic branches, as well as the intrinsic enteric nervous system.

Parasympathetic Innervation

  • Origin: Primarily from the anterior and posterior vagal trunks of the vagus nerve (CN X).
  • Distribution:
    • The anterior vagal trunk supplies parts of the anterior surface of the stomach and the pylorus.
    • The posterior vagal trunk innervates the remaining anterior surface and the entire posterior surface.
  • Functions:
    • Stimulates gastric secretion and motility.
    • Induces relaxation of the pyloric sphincter during gastric emptying.
    • Transmits sensory information like pain, fullness, and nausea from the stomach.

Sympathetic Innervation

  • Origin: From the celiac plexus, with nerve impulses coming from the fifth to twelfth thoracic spinal nerves (T5-T12).
  • Functions:
    • Inhibits gastric motility.
    • Constricts the pyloric sphincter, preventing gastric emptying.

Enteric Nervous System (ENS)

  • Components:
    • Myenteric (Auerbach’s) Plexus:
      • Location: Between the muscular layers of the stomach.
      • Function: Primarily regulates gastric motility.
    • Submucosal (Meissner’s) Plexus:
      • Location: In the submucosa layer.
      • Function: Primarily regulates enzyme secretion, blood flow, and ion transport within the stomach.

Summary

The innervation of the stomach is an intricate network that coordinates the complex digestive activities of the organ. The parasympathetic and sympathetic components of the autonomic nervous system, alongside the intrinsic enteric nervous system, collaboratively ensure the proper functioning of the stomach by finely tuning its motility, secretion, and various physiological processes. This sophisticated system exemplifies the dynamic nature of the gastrointestinal tract’s control mechanisms.

Anatomical Relations of the Stomach

 

Superior Relations

  • Oesophagus: Connects to the stomach at the cardia.
  • Left Dome of the Diaphragm: Sits just above the stomach, influencing its position and space in the abdominal cavity.

Anterior Relations

  • Diaphragm: Separates the thoracic cavity from the abdominal cavity, located just above the stomach.
  • Greater Omentum: A fatty apron that drapes over the stomach and other abdominal organs.
  • Anterior Abdominal Wall: Provides structural support and protection for the stomach and other abdominal organs.
  • Left Lobe of Liver: Overlaps the stomach, especially the fundus and upper part of the body.
  • Gall Bladder: Situated beneath the liver, in close proximity to the stomach.

Posterior Relations

  • Lesser Sac (Omental Bursa): A cavity behind the stomach that allows free movement and provides space for expansion.
  • Pancreas: Lies posterior to the stomach, with the body and tail extending towards the left.
  • Left Kidney and Left Adrenal Gland: Located posteriorly and slightly superior to the stomach.
  • Spleen: Positioned to the left of the stomach, connected by the lienorenal and gastrosplenic ligaments.
  • Splenic Artery: Runs along the superior border of the pancreas, supplying blood to the spleen, pancreas, and stomach.
  • Transverse Mesocolon: A fold of the peritoneum, attaching the transverse colon to the posterior abdominal wall, lying posterior to the stomach.

Sphincters of the Stomach

 

The stomach features two primary sphincters located at its entry and exit points. These sphincters play crucial roles in regulating the movement of materials into and out of the stomach, ensuring proper digestion and timing of nutrient processing.

Inferior Oesophageal Sphincter

  • Location: The oesophagus transitions to the stomach at the T11 level, after passing through the oesophageal hiatus in the diaphragm at the T10 level.
  • Function:
    • Marks the transition from the oesophagus to the stomach.
    • Allows the passage of food through the cardiac orifice into the stomach.
  • Control: Involuntary, not under direct conscious control.
  • Contrast with Superior Oesophageal Sphincter: The inferior oesophageal sphincter is situated at the stomach’s entrance, whereas the superior oesophageal sphincter is located in the pharynx.

Pyloric Sphincter

  • Location: Positioned between the pylorus of the stomach and the first part of the duodenum.
  • Function:
    • Controls the discharge of chyme (a mixture of partially digested food and gastric acid) from the stomach into the duodenum.
    • The sphincter remains contracted most of the time, ensuring food is retained in the stomach long enough for effective digestion.
  • Structure: An anatomical sphincter composed of smooth muscle.
  • Action:
    • Intermittent relaxation allows the stomach to empty its contents when intragastric pressure exceeds the resistance of the pylorus.
    • Gastric peristalsis aids in pushing chyme through the pyloric canal into the duodenum, where digestion continues.

The coordinated activity of these sphincters ensures a regulated digestive process, allowing for the sequential breakdown and absorption of nutrients while preventing issues such as reflux or premature passage of stomach contents.

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