Biology 120 Chapter 2 Presentation

1. The Stomach
Tanis Rusin
Medical Terminology
Biology 120
Chapter 2 Presentation
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2. Stomach Presentation Outline
• Position & Purpose
• Gross Anatomy
• Muscle Compostion
• Moving Food
• Digestive Process
• Homeostatic Imbalances
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3. Position & Purpose of the
Stomach
•The 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.
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4. Gross 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).
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5. Muscle Layers of the Stomach
1. Longitudinal Layer –
most superficial
muscle layer of the
stomach Longitudinal Layer
2. Circular Layer – Circular Layer
middle muscle layer
of the stomach
3. Oblique Layer – Oblique
Layer
deepest muscle layer
of the stomach
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6. Moving Food Through the Stomach
• Peristalsis: wavelike contractions my the smooth muscle layers that
move foodstuffs through the GI tract (see image below).
1. Propulsion: Peristaltic waves move from the fundus toward the
pylorus
2. Grinding: The most vigorous peristalsis & mixing action occur close
to the pylorus
3. Retropul.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.
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7. Digestive Process
1. Bolus (masticated food) enters the stomach through the
esophagus causing stomach distension (stretching).
2. Once the stretch receptors are activated it causes Acetylcholine
(ACh) to be released. ACh stimulates the output of gastric juice.
3. 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. 7

8. Homeostatic 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.
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9. The End
Thank You for Viewing
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