5.3.2. Overview of the Stomach - Gastric Acid Flashcards
What is Gastric Acid?
Hydrochloric Acid
Which cells produce Gastric Acid?
Parietal Cells
Where are the Gastric Parietal Cells found?
In the Gastric Glands
Are the Parietal Cells Superficial or Deep to the Mucous Cell Neck of the Gastric Gland?
Deep
Are the Parietal Cells Superficial or Deep to the Chief Cells of the Gastric Gland?
Superficial
What is the First Stage of Gastric Acid Secretion?
Carbon Dioxide from the Capillaries diffusing across the Gastric Cell Membrane
What does the diffused Carbon Dioxide combine with in the Gastric Cell?
Water
What does the Carbon Dioxide combine to form, in the Gastric Cell?
Carbonic Acid (H2CO3)
What is needed in the Gastric Cell to combine Carbon Dioxide and Water?
Carbonic Anhydrase
An intracellular reaction causes the Carbonic Acid (H2CO3) to form what?
- Bicarbonate (HCO3)
2. A Hydrogen Ion (H)
What happens to the Bicarbonate (HCO3) after it has been formed?
It is transported into the Capillary Lumen
What transports the Bicarbonate into the Capillary Lumen?
A Bicarbonate Chloride Transport Protein
Other than transport Bicarbonate (HCO3) out of the Gastric Cell, what else does the Bicarbonate Chloride Transport Protein do?
Transports A Chloride Ion from the Capillary Lumen into the Gastric Cell
What happens to this Chloride Ion after it enters into the Gastric Cell?
It diffuses out into the Gastric Lumen due to leaky Chloride Channels
What happens to the Hydrogen Ion after it has been formed in the Gastric Cell?
It is transported into the Gastric Lumen
What transports the Hydrogen Ion into the Gastric Lumen?
A Hydrogen Potassium Transport Protein
Other than transport A Hydrogen Ion out of the Gastric Cell, what else does the Hydrogen Potassium Transport Protein do?
Transports A Potassium Ion from the Gastric Lumen into the Gastric Cell
What 3 mechanisms control Gastric Acid secretion?
- Neurocrine
- Endocrine
- Paracrine
By what mechanism does the Neurocrine mechanism control Gastric Acid secretion?
- The arrival of the Bolus in the Stomach causes the Enteric Reflex to occur
- The Presence of Food causes Parasympathetic Vagal Nerve Stimulation to Increase
- Both of these cause Acetylcholine release, which acts on the Parietal Cells to increase the production of Gastric Acid
By what mechanism does the Endocrine mechanism control Gastric Acid secretion?
- The Presence of Food causes Parasympathetic Vagal Nerve Stimulation to Increase
- This causes Gastrin Release from G-Cells of the Stomach / Duodenum
- Gastrin acts on the Parietal Cells to increase the production of Gastric Acid
By what mechanism does the Paracrine mechanism control Gastric Acid secretion?
- The Presence of Food causes Parasympathetic Vagal Nerve Stimulation to Increase, and Gastrin to be Produced
- These act on Enterochromaffin Cells (ECL Cells) within the Gastric Glands (In the Gastric Mucosa)
- This causes the Production of Histamine from ECL Cells
- Histamine acts on the Parietal Cells to increase the production of Gastric Acid
What are the 3 Phases which inhibit Gastric Acid Secretion?
- The Cephalic Phase
- The Gastric Phase
- The Intestinal Phase
By what mechanism does the Cephalic Phase inhibit Gastric Acid secretion?
- Stopping eating decreases the Vagus Nerve (Parasympathetic) Activity
- This causes a decrease in the Production of Gastric Acid
By what mechanism does the Gastric Phase inhibit Gastric Acid secretion?
- The pH decreases due to the increasing concentration of Gastric Acid
- This inhibits Gastrin production from the G-Cells in the Stomach / Duodenum
- This causes a decrease in the Production of Gastric Acid
By what mechanism does the Intestinal Phase inhibit Gastric Acid secretion?
- The presence of Acid in the Duodenum stimulates the Enterogastric Reflex and the release of Secretin
- Fat in the Duodenum causes the release of Gastric Inhibitor Polypeptide (GIP) to be released
- These all decrease Gastrin Secretion
- This causes a decrease in the Production of Gastric Acid