Pages 466-469. Temporary food storage mechanical and chemical breakdown of food ◦ Pepsin is...
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Transcript of Pages 466-469. Temporary food storage mechanical and chemical breakdown of food ◦ Pepsin is...
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The StomachPages 466-469
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Temporary food storage mechanical and chemical breakdown of
food◦ Pepsin is secreted to break down protein
chyme (processed food) is the end result◦ A combination of digestive enzymes, pepsin, HCl◦ Sent to the small intestine
© 2015 Pearson Education, Inc.
Functions of the Stomach
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C-shaped organ - left side of abdominal cavity
Sphincters control openings:◦ Food enters at cardioesophageal sphincter◦ Food exits at pyloric sphincter (valve)
Regions of the stomach:◦ Cardial part (cardia)—near the heart◦ Fundus—expanded portion lateral (left) to the cardiac
region◦ Body—midportion◦ Pylorus—funnel-shaped terminal end
© 2015 Pearson Education, Inc.
Characteristics of the Stomach
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Figure 14.4a Anatomy of the stomach.
EsophagusCardia Fundus
Serosa
Body
Rugaeof mucosa
Pyloricsphincter(valve)
Pylorus
(a)
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Figure 14.4b Anatomy of the stomach.
Fundus
Body
Rugaeof mucosa
Pyloricsphincter
(b)
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Rugae allow stomach stretch internal folds of the mucosa present when the stomach is empty
Muscularis externa has a third oblique layer◦ helps to churn, mix, and pummel the food
© 2015 Pearson Education, Inc.
Stomach
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Figure 14.4a Anatomy of the stomach.
EsophagusCardia Fundus
Serosa
Body
Rugaeof mucosa
Pyloricsphincter(valve)
Pylorus
• Oblique layer• Circular layer• Longitudinal layer
Muscularisexterna
(a)
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lined with simple columnar epithelium
In addition, it contains◦ gastric pits
house gastric glands secrete gastric juice
◦ mucous cells produce bicarbonate-rich alkaline mucus that protect the stomach wall
© 2015 Pearson Education, Inc.
The Stomach mucosa
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Gastrin – which promotes production of:◦ Enzymes that break down proteins:
Pepsin Rennin (present in infants)
◦ Hydrochloric Acid◦ Intrinsic factor (a glycoprotein)- needed for
vitamin B12 absorption in the small intestine
Regulated by neural and hormonal factors
Most chemical digestion occurs in the pyloric region
Composition of Gastric Juice
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Figure 14.4c Anatomy of the stomach.
Pyloricsphincter
Gastric pits
Gas
tric
pi
tG
astr
ic g
land
Surfaceepithelium
Parietal cells (secrete HCL)
GastricglandsChief cells Produce pepsinogen (pepsin)
Enteroendocrine cells(secrete gastrin)
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Food propulsion1. Peristalsis: waves of peristalsis force food past the
pyloric sphincter2. Grinding: The pylorus regulates the flow of chyme
into the small intestine 3 ml at a time Retropulsion: peristaltic waves close the pyloric
sphincter this forces contents back into the stomach. the stomach empties in 4–6 hours depending on meal
quality High fat = slow digestion
© 2015 Pearson Education, Inc.
Activities in the Stomach