Chapter 13 Chapter 13 Digestive tractDigestive 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 absorptio

n ---lamina propria: LCT-compact CT: contain mo

re cells and fiber• BV, LV-capillaries• Lymphoid T• glands: structures formed by invagination of e

pi. 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. Esophagus3. Esophagus

1)      mucosa: • epithelium: stratified squamous epi.• lamina propria: CT• muscularis mucosa: longitudinal arrang

ed SM 2)      submucosa: • LCT• esophageal gland: mucous gland

3)      muscularis: • inner circular and o

uter 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. Stomach4. 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 m

ucus• 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 Nu

cleus• cytoplasm: /basal-basophilic /apical-zymogen granulesEM: RER, Golgi apparatus---function: secret pepsinoge

n

b. parietal cell or oxyntic cell---structure:LM: • large, pyramidal or spherical• round centrally-located nucle

us• eosinophilic cytoplasmEM:• intracellular secretory canali

culus-invaginations• tubulovesicular system• mitochondria

---function: i. secret hydrochloric acid (HCl) -synthesis processes of HCl: in intracellular secret

ory 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 celle. endocrine cell , i.e• G cell: secreting gastrin( 胃泌素 ), promote s

ecretion 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 intestine5. 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 t

o 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, basally- located, in groups

-apical: acidophilic G- Lysozyme （ 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 intestine6. 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）