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What are the Exocrine secretions in the Stomach and what is there location?
- Surface cells- Mucus, HCO3
- Neck cells- Mucus, HCO3
- Parietal cells- HCL, Intrinsic factor
- Chief cells- Pepsinogen and gastric lipase
What are the endocrine secretions in the stomach?
From andtral D and G cells- Gastrin and Somatostatin.
What are the three phases of the digestive period?
Cephalic- Gastric- Intestinal-
What is the Cephalic phase?
Sensory receptors causes the increase in Acid secretions due to efferent preganglionic vagal fibers that activate the ENS fibers.
What is the gastric phase?
- Three parts:
- Intragastric buffering by food- pH rises slightly
- Distension-activates Vago Vago reflexes that effect ENS to secrete Gastrin and lower pH.
- Chemical stimulation- Ca,Caffeine,Alcohol and protein stimulate acid secretions.
What does GRP do?
It stimulates Gastrin cells to release gastrin in to the blood -->leads to acid secretion.
What is the role of CCK and Secretin?
In the intestine, they responed to high protein nad H+ levels and cause the release of the inhibitory hormone Enterogastrone which decreases gastrin release.
Name some aggresive factors of the Mucosal barrier.
HCL/Pepsin, Bile, H. Pylori (gram Neg in the antrum), alcohol and nicotine and aspirin(decrease the production of prostaglandins which causes an increase in acid)
Name some protective factors.
Mucus, HCO3, Blood flow (washes H+ away), Membrane integrity and fast membrane repair.
What is intrinsic factor? where is it secreted?
- It is a glycoprotein that is secreted by by the parietal cells in reponse to ACh gastrin or histamine.
- Is essential for B12 Absorption in the ileum.
Role of R-protiens and IF in B12 absorption.
- In the stomach- B12 binds to R protein.
- In the intestin trypsin causes the b12 to release R and grab IF.
- IF carries B12 to the ileum where it binds to a recepter, is internalized.
- B12 then releases IF and binds to transcobalamin II