Stomach - structure of wall, divisions, vascular supply, innervation and lymphatics

Structure of stomach wall

The wall in all regions of the stomach is made up of all four major layers of alimentary tube. The muscularis layer consists of three layers of muscle: inner oblique, middle circular (becomes sphincter), outer longitudinal. The mucosa and submucosa of the empty stomach have folds known as rugae – which flatten when the stomach is filled with food.

Cardia

• Mucosa: Transition from the stratified squamous non keratinized epithelium to simple columnar epithelium.

1. Lamina Propria: Gastric pits with Cardiac glands
2. Muscularis mucosa

• Submucosa: Arteries, veins, submucosal plexus.
• Muscularis: smooth muscle, myenteric plexus.
• Serosa: Loose CT, mesothelium.
• Contains cardiac glands (tubular glands) under the gastric pits – secreting mucus and lysozyme – enzyme that attacks bacterial walls

Fundus

Mucosa: Simple columnar epithelium.

Lamina propria: Containing the Gastric Pits (Deeper, Longer and Narrower) and the Proper Gastric Glands: isthmus, neck and base (different epithelial distribution)

Chief cells: In the base

Function:

• Producing inactive precursor pepsinogen. 🡪 In the gastric lumen (pH<5) changes into an active enzyme pepsin - breaking down large molecules of proteins.
• produce Lipase and Leptin

Parietal Cells: In upper half of gland

• Function:
  • Acid producing cells, H+ ions, Cl- 🡪 HCl acid
  • Intrinsic factor (b12 absorption)

Enteroendocrine cells: Throughout digestive system

• Function: produce and secrete different hormones: Serotonin, Gastrin…

Mucus-neck cells: In the neck between parietal cells

• Function: mucus producing cells

Pylorus

Glands: Pyloric glands, the same as in the Cardiac glands, Tubular mucous cells secreting mucus and lysozyme – which is an enzyme that attacks the bacterial walls.

Divisions of the Stomach:

Parts:

• Cardia: attached to esophagus (T10) - Cardiac Orifice
• 

  Description of Stomach Divisions
  Fundus: Superior part, below left dome of diaphragm.
• Body : Major part of stomach, between fundus and pylorus.
• Pylorus : Out flow, can be divided into 2 parts:
  • Pyloric Antrum: wider part
  • Pyloric Canal: Connects to the duodenum.

Curvatures:

• Greater curvature: lower border, between fundus and pylorus.
• Lesser curvature: upper border, between cardia and angular notch.

Notches and angles:

• Cardiac notch – between esophagus and fundus.
• Angular notch – between body and pylorus (lesser curvature)
• Angle of Stomach – between body and pylorus (greater curvature)

Fixations of the Stomach:

Peritoneal duplicators covered by mesothelium (ligaments) extend from the serous coat of the stomach and course towards both curvatures.

Blood and lymph vessels, nerves and lymph nodes are positioned in the loose fibrous tissue between the sheets of peritoneum.

• Lesser omentum: From the lesser curvature to surrounding structures
  • Hepatogastric ligament: to the liver
  • Hepatoduodenal ligament (with portal triad in it) : liver to duodenum
• Greater omentum: From the greater curvature to surrounding organs
  • Gastrosplenic ligament: to the spleen.
  • Gastrophrenic ligament: to the diaphragm.
  • Gastrocolic ligament: to the transverse colon

Lesser Omental bursa (smaller part of the peritoneal cavity) – behind the lesser omentum, posterior to the hepatoduodenal ligament. Its entrance id the omental foramen.

Blood supply (The Celiac Trunk)

Blood supply via the celiac trunk

• Anastomosis Along the lesser curvature:
  • Left gastric Artery (From Celiac Trunk)
  • Right Gastric Artery (from hepatic artery proper)
• Anastomosis along the Greater curvature:
  • Left Gastro-Omental (from splenic artery)
  • Right Gastro-Omental (From the Gastroduodenal artery)

Other branches:

• Short Gastric arteries (from splenic artery) – to fundus and body.
• Pyloric artery (from hepatic artery proper) – to anterior surface of the pylorus.

Venous Drainage : Portal Vein

• Left and right gastric vein to the hepatic Portal system
• Right Gastro-Omental vein to the superior mesenteric to the Hepatic portal
• Left Gastro-Omental vein to the splenic to the Hepatic portal
• Short Gastric veins

An important portocaval anastomosis is formed by connections with the esophageal veins within the area of the cardia.

Innervation

• Parasympathetic: Vagus nerves (anterior and posterior vagal trunks, anterior and posterior gastric branches) => more peristalsis, increase circulation.
• Sympathetic: Splanchnic nerves (fibers from the coeliac plexus and via the Peri-atrial plexuses enter the stomach wall) => Balances parasympathetic activity, blood vessels constrictions, movements, producing of acids.
• Viscerosensory:
  • via parasympathetic nerves - Pressure, cold, heat
  • via sympathetic nerves - Pain.

Lymphatic Drainage

Subserous (in mesenteries) lymphatic vessel network:

• Cardia, most of anterior and posterior wall drains to the lesser curvature and finally the Gastric nodes (proximal to the left gastric artery).
• Fundus, greater curvature drain to the splenic nodes.
• Greater curvature drain to the Gastro omental nodes
• Pylorus drains into the Gastro-omental nodes, pyloric nodes.