STOMACH

STOMACH

Definition

The stomach is a sac-like organ in the abdominal cavity that plays a crucial role in digestion.

Location

The stomach is located in the upper left region of the abdomen, below the diaphragm and above the small intestine.

Structure

• The stomach is a muscular, sac-like organ with a capacity of about 1.5 liters.
• It is divided into four main regions: fundus, body, antrum, and pylorus.
• The stomach wall consists of three layers: mucosa, submucosa, and muscularis.

Mucosa

• The mucosa is the innermost layer of the stomach wall, lined with epithelial cells that secrete mucus.
• The mucosa is folded into longitudinal and circular folds to increase the surface area for digestion.

Submucosa

• The submucosa is a layer of loose connective tissue that separates the mucosa from the muscularis.
• It contains blood vessels, lymphatic vessels, and nerve fibers.

Muscularis

• The muscularis is a layer of smooth muscle that surrounds the stomach and helps to mix food with digestive enzymes.
• The muscularis is divided into two layers: inner circular and outer longitudinal.

Blood Supply

• The stomach is supplied by the left gastric artery, right gastric artery, and short gastric arteries.
• The blood supply is rich in oxygenated blood, which helps to facilitate the digestive process.

Nerve Supply

• The stomach is innervated by the vagus nerve, which regulates the digestive process.
• The vagus nerve stimulates the release of digestive enzymes and helps to regulate the movement of food through the stomach.

Lymph Drainage

• The stomach drains lymph into the cisterna chyli, which is located in the abdominal cavity.
• The lymphatic system helps to remove waste products and excess fluids from the stomach.

Function

• The stomach secretes digestive enzymes and acids that break down food into smaller molecules.
• The stomach churns food with its muscular walls, mixing it with digestive enzymes and acids.

Stepwise Mechanism

1. Food enters the stomach through the esophagus →
2. The stomach secretes digestive enzymes and acids →
3. The stomach churns food with its muscular walls →
4. The food is mixed with digestive enzymes and acids →
5. The food is broken down into smaller molecules →
6. The food is released into the small intestine for further digestion.

Clinical Significance

• The stomach is a common site for ulcers and other digestive disorders.
• The stomach can be affected by various diseases, such as gastritis, peptic ulcers, and stomach cancer.

Developmental Process

• The stomach develops from the foregut endoderm during embryonic development →
• The stomach differentiates into the fundus, body, antrum, and pylorus →
• The stomach wall develops its layers, including the mucosa, submucosa, and muscularis →
• The stomach is innervated by the vagus nerve and drained by the lymphatic system →
• The stomach is fully formed and functional by birth.

STOMACH

1. Describe the morphology of stomach

The stomach is a sac-like organ located in the abdominal cavity. It is a distensible, muscular, and hollow organ that lies between the esophagus and the small intestine. The stomach has a rounded shape with a capacity of about 1 liter in adults. The stomach is divided into four main regions: cardia, fundus, body, and antrum.

2. Describe the relations of stomach

The stomach is related to the following structures:

• Esophagus (anteriorly)
• Diaphragm (inferiorly)
• Liver (inferiorly and to the right)
• Spleen (to the left)
• Pancreas (to the right)
• Transverse colon (inferiorly and to the right)
• Left kidney (posteriorly)

3. Describe the interior of stomach

The interior of the stomach is lined with mucous membrane that secretes mucus and digestive enzymes. The stomach has three layers of smooth muscle: the longitudinal, circular, and oblique layers. The longitudinal layer runs parallel to the greater curvature, the circular layer surrounds the stomach, and the oblique layer runs between the longitudinal and circular layers. The stomach has three main types of glands: oxyntic, pyloric, and mucous glands.

4. Describe the blood and nerve supply of stomach

The stomach receives blood supply from the:

• Left gastric artery (from the celiac trunk)
• Right gastric artery (from the hepatic artery)
• Gastroepiploic artery (from the splenic artery)
• Short gastric arteries (from the splenic artery)

The stomach receives nerve supply from the:

• Vagus nerve (parasympathetic)
• Sympathetic nerves (from the celiac plexus)
• Enteric nervous system (intrinsic nervous system)

5. Explain the applied anatomy of stomach

The stomach is involved in the digestion of food. The process of digestion involves the following steps:

• Food enters the stomach through the esophagus
• The stomach secretes mucus and digestive enzymes to break down food
• The stomach churns and mixes food with digestive juices
• The stomach contracts and relaxes to move food into the small intestine for further digestion and absorption.

The applied anatomy of the stomach is relevant in the diagnosis and treatment of various gastric disorders, such as ulcers, gastritis, and gastric cancer.