Download Chapter 13 Digestive tract

Chapter 13
Digestive
tract
---Digestive system:
Digestive tract
Digestive gland
1. Components of digestive tract
---oral cavity
---pharynx
---esophagus
---stomach
---small intestine
---large intestine
2. General plan of digestive tract
---Except for oral cavity and pharynx, all other
organs share a similar histological plan
1) mucosa
---epithelium:
stratified squamous epi.: protecting
simple columnar epi,: digestion and
absorption
---lamina propria: LCT-compact CT: contain
more cells and fiber
BV, LV-capillaries
Lymphoid T
glands: structures formed by invagination of
epi. into lamina propria
---muscularis mucosa: a thin layer of SM
2) submucosa: more dense CT
small artery and vein, LV
glands (esophagus and duodenum)
submucosa N plexus:
-multipolar N
-unmyelinated NF
-function: regulate the contract of SM and
secreting of gland
*Plica: projection of mucosa and submucosa
3) muscularis externa
smooth muscle
skeletal muscle
inner circular and outer longitudinal
*Nerve plexus: regulate the movement of
M
4) adventitia: CT
serosa: CT + mesothelium
fibrosa: LCT
3. Esophagus
1)
mucosa:
epithelium: stratified squamous epi.
lamina propria: compact CT
muscularis
mucosa:
longitudinal
arranged SM
2)
submucosa:
LCT
esophageal gland: mucous gland
3)
muscularis:
inner circular and outer longitudinal
upper 1/3: skeletal muscle
middle 1/3: mixed of skeletal M and smooth
muscle
lower 1/3: smooth muscle
4) adventitia: fibrosa
4. Stomach
---dilated part
---store food temporarily
---digest protein primarily
---absorb part of water and Ions
1)
Mucosa:
---plica-longitudinal
---shallow ditch- gastric area(2-6mm)
---gastric pit- small depressions
①epithelium:
simple
columnar epi
surface mucous cell:
-tall columnar
-N ovoid, basally-located
-mucinogen granule
-tight junction
-high HCO3- undissolved
mucus
less endocrine cell
②lamina propria: CT contains fibroblast,
LC, plasma cell, mast cell and
eosinophil, SM
gastric
gland(fundic
gland)-oxyntic
gland
cardiac gland: mucous gland
pyloric gland: mucous gland
* Fundic gland
-long, branch tube liked
gland:
/neck, body and basa
-five types of cells can be
seen
a. chief cell or zymogenic
cell
---structure:
LM:
columnar
Round,
basally-located
Nucleus
cytoplasm:
/basal-basophilic
/apical-zymogen granules
EM: RER, Golgi apparatus
---function:
secret
pepsinogen
b. parietal cell or oxyntic cell
---structure:
LM:
large, pyramidal or spherical
round
centrally-located
nucleus
eosinophilic cytoplasm
EM:
intracellular
secretory
canaliculus-invaginations
tubulovesicular system
mitochondria
---function:
i. secret hydrochloric acid (HCl)
-synthesis processes of HCl: in intracellular
secretory canaliculus
H+ K+ -ATP pump: get H+ from cell
Cl- channel: get Cl- from blood
H+ +Cl-→HCl(intracellular secretort canaliculi)
-function of HCl:
HCl
↓
pepsinogen→pepsin
kill the bacterium
ii. secret intrinsic factor- glycoprotein +
VB12→absorption of VB12
c. mucous neck cell
less, neck part
columnar
flattened, basally-located N
pale stain in HE stain
d. stem cell: undifferentiated cell
e. endocrine cell
ECL cell: secreting histamine, promote
secretion of parietal cell
D cell: secreting somatostatin, inhibit the
secretion of parietal cell
* cardiac gland and pyloric
gland: mucous gland, contain
G cell, which secretes gastrin,
to promote the secreting of
parietal cell
* Mucous-HCO3 barrier:
0.25-0.5mm thick mucous
HCl PH: 0.9-1.5
H+ + HCO3- → H2CO3 →H2O +
CO2
↑
bicarbonatase
③ Muscularis mucosa: inner circular and
outer longitudinal arranged SM
2) submucosa: CT with BV, LV, N and fat cell
3)
muscularis : thicker
inner oblique
middle circular
outer longitudinal
4) advantitia: serosa
5. Small intestine
---duodenum
---jejunum
---ileum
1)
Mucosa
---circular plica
---intestinal villus
---small intestinal
gland
①epithelium:
---absorptive cell:
microvilli: striated-border
-1-1.4um long, 80nm in D,
2000-3000
-enlarge the surface area
to 30 times
cell coat:
-0.1-0.5um
-enzymes:
trypsinogen,
amylase - glucose and
protein
enzymes-adipose
SER
---goblet cell
---endocrine cell:
I cell: secreting cholecystokininpancreozymin
S cell: secreting secretin
②lamina propria: CT (LC,
macrophage, plasma cell
and eosinophil and mast
cell)
a. villus: is the projection
of epithelium and lamina
propria
epithelium: absorptive
cell, goblet cell and
endocrine cell
lamina propria: CT with
central
lacteal,
fenestrated cap. and SM
b.
small intestinal gland: is the
invagination of epi.into propria
absorptive cell
goblet cell
endocrine cell
stem cell
Peneth cell
Peneth cell:
LM:
-pyramidal,
basallylocated, in groups
-apical: acidophilic Gcontain
defensin(cryptdin),
Lysozyme
EM:
-protein-secreting cell
feature
Function: related to
immune function
③muscularis mucosa: SM inner circular
and outer longitudinal
2)
submucosa: CT
Large BV and LV
duodenal
gland:
mucous
glandsecreting epidermal growth factor,
promote the epithelial cell proliferation
of small intestine
3) muscularis: SM, inner circular and
outer longitudinal
4) adventitia: serosa and less fibrosa
6. Large intestine
---absorb water and ions
---structure feature:
a. no villus and no circular plica
b. well-developed large intestinal gland
c. contain more goblet cells
d. taeniae coli: longitudinal bunds
bag coli