Post on 12-Jan-2016
The StomachPages 466-469
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
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Functions of the Stomach
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
Figure 14.4a Anatomy of the stomach.
EsophagusCardia Fundus
Serosa
Body
Rugaeof mucosa
Pyloricsphincter(valve)
Pylorus
(a)
Figure 14.4b Anatomy of the stomach.
Fundus
Body
Rugaeof mucosa
Pyloricsphincter
(b)
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
Figure 14.4a Anatomy of the stomach.
EsophagusCardia Fundus
Serosa
Body
Rugaeof mucosa
Pyloricsphincter(valve)
Pylorus
• Oblique layer• Circular layer• Longitudinal layer
Muscularisexterna
(a)
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
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
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)
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