Download Secretory Systems and Stomach

Buccal Cavity: Primary Salivary Glands
Stensen’s
duct
Buccinator
Sublingual
gland
Masseter
muscle
Parotid gland
Mandible
Wharton’s
duct
Submaxillary
Gland
Organization of the “Salivon”
• Filtration: In the Acinus is Primarily Passive
Acinar cells
Ductal cells
Myoepithelial cell
Acinus
Intercalated duct
Myoepithelial cell
Striated duct
Functions of Saliva: Digestion, Protection-Lubrication
•

-
Digestive:
a-Amylase: Starch Digestion
pH optima 7.0; Active in Proximal Stomach
Ligual Lipase: Fat Digestion
pH optima ~4.0; does not require bile salts
• Lubrication/Protection:
- Anti-Bacterial: I -, SCN -, Secretory IgA,
Lysozyme and Lactoferrin
- Anti-Corrosive: HCO3 to buffer pH; F- Ca2+.
- Lubrication: Mucus- Mucopolysaccharides, H2O
Coat the Food to Aid in Swallowing-Taste
Prevent Abrasion
Organization of the “Salivon”
• Filtration: In the Acinus is Primarily Passive
Acinar cells
Ductal cells
Myoepithelial cell
SP
Acinus
Intercalated duct
Striated duct
Myoepithelial cell
Acetylcholine
Capillaries
SP: Substance P
Stomach Anatomy
Gastric Pits and Glands
Gastric Lumen
Gastric
Pits
Columnar
Epithelium
Lamina
Propria
Mucosa
Gastric
Gland
Lymph
Node
Lymphatics
SubMucosa
Mucularis
Serosa
Gastric Pits
GASTRIC
GLANDS
Gastric Lumen
Mucus
Superficial
epithelial
cells
Mucus
neck
cells
Parietal
cells
(Oxyntic)
Peptic
cells
The Epithelial Protective Barrier
Tight Junctions between Adjacent Cells
Mucus and Bicarbonate Secretion
Rapid Turnover – Cell Migration and
Proliferation
: All Appear to be Driven by Prostaglandins
Oxyntic Gland Secretions
Cell Type
Component
• Peptic
•
Gastroferrin
Pepsin-ogen
• Mucus Neck
• Oxyntic
Function:
Iron Binding Protein
Protease
Mucopolysaccharides; HCO3
Intrinsic Factor
•
HCl
B12 Binding
Protein
Digestion/
“denaturation”
(P/D)
P
D
P
D
P/D
P- Protective; D- Digestive
Roles of HCl in the Stomach
• Protein Digestion :
- Activates Pepsin
- Denatures and Solubilizes Tissue
• Protective: Kills Bacteria
CA – Carbonic Anhydrase
The Oxyntic Cell
BasoLateral
HCO3-
Lumen
of gland
CA
H2CO3
Metabolism CO2
HCO3-
H+
Cl-
ATP
K+
Cl-
ClNa+
ATP
Na+
H+
K+
Canaliculus
K+
Cl-
Role of Carbonic Anhydrase
CA
CO2 + H2O
H2CO3
HCO3- + H+
Key Players: HCl Secretion
• H+ / K+ ATPase :
• Carbonic
Anhydrase
• Na/K ATPase
Location
Inhibitor
Lumenal
Omeprazole
Cytosolic
Acetozolamide
Basolateral
Ouabain
• K+ / Cl- cotransport : Lumenal
Cl- / HCO3 antiport: Basolateral
Histamine
A
CM
CM
A
A
CM
Ca2+
La2+
Adenylate
ATP
cAMP
Cyclase
IP3
Ca2+
Ca2+
A - ATROPINE
Blocks
Does not
block
Ln2+- Lanthanum
CM - Cimetidine
H+
H+ Secretion
Phases of Secretion
Phase
• Cephalic
• Gastric
Stimuli
Pathway
Smell, Taste
Central reflexes
Chyme Enters Stomach
Distension,
Local Effects
Amino Acids
• Intestinal
Chyme Enters
Local Feedback
the Intestine
• Inter-Digestive
Histamine
Basal
Release
Primary Mechanisms for Inhibiting HCl
Secretion
Location (Phase)
• Antrum
(Gastric)
Stimuli
Pathway
Acidification pH < 3 Somatostatin Inhibition
Maximal
pH < 1
of Gastrin Secretion
• Duodenum
(Intestinal)
Distension
pH < 6
Fat and Peptides
Enteric (Local) Reflexes
Entero-gastrone?
Regulation of G-Cell Secretion
Vagus nerves
Myenteric
Ach
Ach
Plexus
+
GRP
Gastrin
Gastrin
Cell
Digested
Protein
Ach
Somatostatin
Cell
H+
Body
ECL
Antrum