1. The Human Stomach
September 11, 2013
2. The Stomach
• The stomach is located in the left upper quadrant. Also contained in
this quadrant is the spleen, left kidney, a small portion of the liver,
the majority of the pancreas, and a portion of the small intestines
• The stomach is held within the abdominal cavity which is on the
anterior or ventral side of the body. Within the abdominal cavity is
the peritoneum, a two layer membrane. The outer layer the lines the
abdominal cavity is the parietal peritoneum, and the inner layer that
encases the stomach is the visceral peritoneum.
• The stomach is inferior to the diaphragm, and superior to the small
4. Medical Terminology
• The following medical terminology terms and abbreviations pertain
to the stomach:
▫ Gastr/o= Stomach
▫ Gastroenterology= Study of the stomach and small intestines
▫ Gastroenterologist= One who studies the stomach and small
▫ Hypogastric= Under the stomach
▫ Epigastric= Above the stomach
▫ GI= Gastrointestinal
▫ LUQ= Left Upper Quadrant
5. Digestive System
• The stomach is a part of the Digestive System.
• Other structures that make up the Digestive System include
▫ Oral cavity
▫ Small intestine
▫ Salivary glands
• The stomach is a J-shaped muscular organ that is composed of three
parts: the fundus (upper region), the body (main portion), and the
antrum (lower portion).
• The cardiac sphincter keeps food from going back into the esophagus.
The pyloric sphincter regulates the passage of food into the small
• The stomach varies from 15 to 25 cm long, and its diameter and volume
depend on how much food is within it. When totally distended the
stomach can hold about 4 Liters of food.
• The stomach contains muscle fibers, nerve tissues, and epithelial tissue.
The lining of the stomach is simple columnar epithelium tissue
composed entirely of mucous cells. Deep gastric pits are all over the
lining and lead to gastric glands which secrete gastric juice.
8. Layers of Muscle
• There are four layers of muscle in the stomach:
▫ Mucosa- Innermost layer. Made of mucous membrane containing
epithelial tissue which has gastric pits which secrete mucus and
▫ Submucosa- Second layer. Made of connective tissue, nerves, and
▫ Muscularis Externa-Three layers of smooth muscle: Inner
Oblique Layer, Middle Circular Layer, and Outer Longitudinal
▫ Serosa- Layers of connective tissue, continues into peritoneum.
Secretes serous fluid to protect stomach from damage when
expanding in the body.
• The stomach completes the following tasks:
▫ Receives food from the esophagus.
▫ Stores the food we eat.
▫ Mixes Hydrochloric Acid and other gastric juices into food to
break it down into chyme. Hydrochloric acid is secreted from
▫ Slowly empties contents into the small intestines for further
digestion. Chyme is passed very slowly into the small intestines
due to the fact that it is highly acidic and needs time to be
▫ The stomach usually takes around 4 hours to empty after a meal.
Liquids pass through more quickly than solids.
10. More on Gastric Juice
▫ Neural and hormonal mechanisms control gastric secretion. This
happens in three phases:
1.)Cephalic Reflex- This happens before food enters the stomach.
Aroma, taste, sight, and thought are all relayed to the hypothalamus in
the brain and after a process of nerve and motor impulses being
transferred , the stomach glands are stimulated.
2.) Gastric- This phase starts once food hits the stomach, lasts three to
four hours, and provides 2/3rds of the gastric juice provided. Gastric
juices are increased because of stomach distension and low acidity
level. Low acidity levels happen when proteins enter the stomach
raising the pH level.
3.)Intestinal- As food begins to enter the small intestines, the
intestines release Intestinal Gastrin, which encourages gastric glands
to continue their activity.
11. Mucosal Barrier
• If the stomach is so acidic, why doesn’t it eat itself?
▫ The stomach is able to withstand all of the acid it produces without being
damaged itself because of the layer of mucus within it.
▫ Three factors make up this barrier:
1.) A thick coating of bicarbonate-rich mucus builds on the stomach
wall (bicarbonate neutralizes acid).
2.) Cells are joined together by tight junctions (which do not allow
things to pass through). Therefore gastric juice can not leak into
3.) Damaged cells on the lining are shed and replaced very quickly.
12. Stomach Ulcers
• Gastric Ulcers are erosions of the stomach wall.
• 90% of recurrent ulcers are caused from a bacteria called Helicobacter
Pylori. These bacteria drill through the mucus and destroy mucosal layer.
• H. Pylori can lead to stomach cancer, but can also be treated with
antibiotics if found.