Lumen of stomach
Gastric pits
- Mucosa
Gastric gland
Submucosa
Muscularis
Oblique layer of muscle
Circular layer of muscle
Serosa
Longitudinal
layer of muscle
Three-dimensional view of layers of the stomach
Lamina
propria
Lymphatic nodule
Muscularis mucosae
Lymphatic vessel
Venule
Arteriole
Simple —
columnar
epithelium
Simple
columnar
epithelium
Lamina
propria
Gastric
glands
Muscularis
mucosae
Submucosa
Surface mucous cell
(secretes mucus)
Mucous neck cell
k
(secretes mucus)
Parietal cell
(secretes hydrochloric"
acid and intrinsic factor)
Chief cell (secretes
pepsinogen and
gastric lipase)
G cell (secretes
the hormone gastrin)
Mucus
forms a protective barrier between the
mucosa and the gastric secretions in the
lumen.
Hydrochloric acid creates
a
gastric pH of 2.0
, which
kills microbes and activates pepsinogen into pepsin
(active enzyme).
Intrinsic
factor
is essential for absorption of vitamin B12.
Pepsinogen
is an inactive gastric enzyme that becomes
pepsin (the active enzyme).
Gastric lipase
breaks down fats.
Gastrin
enters the bloodstream and stimulates secretion
of gastric juice, motility of GI tract, and relaxation of
pyloric sphincter.
Sectional view of the stomach mucosa showing gastric glands and cell types
To summarize, the main functions of the stomach in-
clude the following:
Mixes saliva, food, and gastric juice to form chyme.
Serves as a reservoir for food before release into the
small intestine.
Secretes gastric juice, which contains HCl (kills bacteria
and denatures protein), pepsin (begins the digestion of
proteins), intrinsic factor (aids absorption of vitamin
B12), and gastric lipase (aids digestion of triglycerides).
Secretes gastrin into blood.
Let's Journey Through the Digestive System 407
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