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) tunica muscularis
• smooth muscle
• skeletal muscle
• inner circular and outer longitudinal
*Nerve plexus: regulate the movement of
M
4) tunica adventitia: CT
• serosa: CT + mesothelium
• fibrosa: LCT
3. Esophagus
•
•
•
•
•
1)
mucosa:
epithelium: stratified squamous epi.
lamina propria: 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
ditchgastric 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
• 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 , i.e
• G cell: secreting gastrin( 胃 泌 素 ), promote
secretion of parietal cell
• D cell: secreting somatostatin（生长抑素）,
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
（胰蛋白酶原）, amylase
（淀粉酶） - glucose and
protein
• enzymes-adipose
• SER
---goblet cell
---endocrine cell:
• I cell: secreting cholecystokinin（胆囊收
缩素）
• S cell: secreting secretin（促胰液素）
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 GLysozyme （ 溶 菌 酶 ）
EM:
-protein-secreting cell
feature
Function: related to
immune function
goblet cell
absorptive cell
③muscularis mucosa: SM inner circular
and outer longitudinal
2)
submucosa: CT
• Large BV and LV
• duodenal gland: mucous gland-secreting
epidermal growth factor（表皮生长因子）,
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（结肠带）: longitudinal
bunds
bag coli（结肠袋）