Gross and Microscopic Anatomy of the Stomach

Study Notes

Gross Anatomy

The stomach is a J-shaped, muscular organ located in the upper left quadrant of the abdomen, beneath the diaphragm.
It connects the esophagus to the duodenum (the first part of the small intestine).
The stomach has four main regions: cardia, fundus, body, and pylorus.
- The cardia is the entrance to the stomach.
- The fundus is the dome-shaped portion superior to the cardia.
- The body is the largest region, situated between the fundus and pylorus.
- The pylorus is the narrow, distal region that connects to the duodenum.
- The pylorus contains a thickened ring of smooth muscle, the pyloric sphincter, that controls the emptying of stomach contents into the small intestine.
The stomach's walls are composed of four layers: mucosa, submucosa, muscularis externa, and serosa.

Microscopic Anatomy

The stomach lining, or mucosa, is highly folded to increase surface area for absorption and secretion.
- Gastric pits are invaginations of the mucosa
  - These pits lead to gastric glands that secrete gastric juice.
- Gastric glands contain various cell types that secrete different components of gastric juice, including:
  - Mucus neck cells, which secrete mucus.
  - Parietal cells, which secrete hydrochloric acid and intrinsic factor.
  - Chief cells, which secrete pepsinogen.
  - Enteroendocrine cells, which secrete hormones, such as gastrin.
The submucosa contains connective tissue, blood vessels, and lymphatics.
The muscularis externa has three layers of smooth muscle: an inner oblique layer, a middle circular layer, and an outer longitudinal layer. This complex muscular arrangement aids in mixing and churning of food.
The serosa is the outermost layer, a thin layer of connective tissue covered by visceral peritoneum.

Blood Supply and Innervation

The stomach receives blood from the celiac trunk.
- Branches of the celiac artery, such as the left gastric, splenic, and common hepatic arteries, provide the blood supply to the stomach.
The stomach is innervated by the autonomic nervous system.
- The parasympathetic fibers, via the vagus nerve, stimulate gastric secretion.
- The sympathetic fibers, from the celiac plexus, inhibit gastric secretion.

Functions

The stomach plays a crucial role in the digestive process, performing several functions:
- Storage: The stomach stores ingested food temporarily.
- Mechanical breakdown: The churning and mixing action of the stomach's muscles physically breaks down food into smaller pieces.
- Chemical breakdown: Gastric juices, secreted by the gastric glands, begin the chemical digestion of proteins.

Clinical Significance

Gastric ulcers, caused by the erosion of the stomach lining, can result from infection with Helicobacter pylori, use of nonsteroidal anti-inflammatory drugs, or other factors.
Gastritis, an inflammation of the stomach lining, may be caused by various factors, including infection, stress, and alcohol.
Stomach cancer is a serious disease, and risk factors include chronic infections, particular dietary habits and genetics.
Stomach distension can lead to conditions like abdominal pain and discomfort. It also plays a role in acid-related disorders like heartburn and GERD.

Description

Explore the intricate details of the stomach's gross and microscopic anatomy. This quiz covers the main regions of the stomach, its structural layers, and the function of the gastric mucosa. Test your knowledge on the anatomy essential for understanding digestive processes.