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The Stomach

1The StomachTanis RusinMedical TerminologyBiology 120Chapter 2 Presentation

2Stomach Presentation Outline Position & Purpose Gross Anatomy Muscle Compostion Moving Food Digestive Process Homeostatic Imbalances

3Position & Purpose of the StomachThe stomach lies in the upper left quadrant of the peritoneal cavity.

It is a part of the digestive system, also known as the gastrointestinal tract or GI tract.

The stomach receives food from the esophagus, begins to digest it & eventually moves it into the duodenum for further digestion.

4Gross Anatomy of the Stomach

Cardia: Surrounds the cardiac orifice through which food enters the stomach from the esophagus.

Fundus: Dome shaped part that bulges superolaterally to the cardia.

Body: midportion of the stomach, is continuous inferiorly with the funnel shaped pyloric region.

Pyloric Region: begins superiorly & wide from the body and narrows to form the pyloric canal & terminates at the pylorus.

Pyolorus: continuous with the duodenum (part of the small intestine).

5Muscle Layers of the StomachLongitudinal Layer most superficial muscle layer of the stomachCircular Layer middle muscle layer of the stomachOblique Layer deepest muscle layer of the stomach

Longitudinal LayerCircular LayerOblique Layer

6Moving Food Through the StomachPeristalsis: wavelike contractions my the smooth muscle layers that move foodstuffs through the GI tract (see image below).

Propulsion: Peristaltic waves move from the fundus toward the pylorusGrinding: The most vigorous peristalsis & mixing action occur close to the pylorusRetropul.sion: The pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum, simultaneously forcing most of its contained material backward into the stomach.

7Digestive ProcessBolus (masticated food) enters the stomach through the esophagus causing stomach distension (stretching).Once the stretch receptors are activated it causes Acetylcholine (ACh) to be released. ACh stimulates the output of gastric juice. Proteases (protein digesting enzymes) & HCl secretion is also stimulated.

4. HCl secretion causes an increase in the pH level. This creates an ideal environment for protein digestion (the only significant type of enzymatic digestion that occurs in the stomach).5. The end result is a product called chyme, partially digested food & gastic juice, which is then moved to the duodenum.

8Homeostatic Imbalances of the Stomach Peptic Ulcers The most common type of ulcer which is typically acidic & thus very painful. Can be caused by a malignant tumor in the stomach, drugs such as aspirin & ibuprofen, high levels of stress. Depending on how severe, they can be treated with antacids, nonsteroidal anti-inflammatories or antibiotics.

Gastritis Inflammation of the lining of the stomach.Can be caused by excessive alcohol consumtion, prolonged use of nonsteroidal anit-inflammatory drugs such as aspirin & ibuprofen or infection post surgery. Treatment can include taking antacids, antibiotics & avoiding hot or spicy foods.

Gastric Cancer - Can develop in any part of the stomach & may spread to other organs. - Can be caused by genetic factors & tobacco smoking.- Treatment can include radiation, chemotherapy & surgery.

9The EndThank You for Viewing