What are the functions of the stomach?
- Stores food
- Disinfects food
- Breaks food down in chyme
How does the stomach break food down into chyme?
- Chemical disruption
- Physical disruption
Where do stomach secretions come from?
What are gastric pits?
Indentations in the stomach mucosa that are openings to gastric glands
What do gastric pits contain?
What do gastric glands contain?
Parietal, Chief, and G-cells, along with smooth muscle cells
Label this diagram
- A - Gastric pit (opening to gastric gland)
- B - Mucous epithelium
- C - Lymphatic vessel
- D - Lamina propria
- E - Muscularis mucosae
- F - Submucosa
- G - Oblique muscle
- H - Circular muscle
- I - Longitudinal muscle
- J - Serosa
- K - Artery and vein
- L - Myenteric plexus
- M - Gastric pit
- N - Gastric gland
- O - Mucous cells
- P - Neck
- Q - Parietal cells
- R - Chief cells
- S - Smooth muscle cells
- T - G cell
What substances are secreted by the stomach?
- Hydrochloric acid
- Proteolytic enzymes
What proteolytic enzyme is secreted by the stomach?
What is the cellular origin of hydrochloric acid in the stomach?
Parietal (oxyntic) cells
What is the purpose of HCl secreted by the stomach?
Acid keeps luminal pH < 2
What is the cellular origin of proteolytic enzymes in the stomach?
What is the function of proteolytic enzymes in the stomach?
Non-specifically breaks down proteins to peptides
What is the cellular origin of mucus in the stomach?
Neck cells (surface cells)
What are the characteristics of stomach mucus?
Why is stomach mucus sticky?
So it is not removed easily from the stomach lining
Why is stomach mucus basic?
Due to amine groups on proteins
What is the cellular origin of HCO3- in the stomach?
Neck cells (surface cells)
What is the purpose of HCO3- in the stomach?
Provides a buffer for H+ ions
Where is HCO3- secreted by neck cells into?
What is the cellular origin of gastrin?
What is the function of gastrin in the stomach?
Binds to surface receptor on parietal cell, stimulating acid and intrinsic factor
Are body fluids acid or alkaline?
Most are slightly alkaline
What must be true for a slightly alkaline body fluid to secrete H+ ions?
It must be created in large quantities
Where does the production of a large amount of body fluid with the intent of secreting H+ occur?
In the mitochondria of parietal cells
How is H+ produced in parietal cells?
By splitting water into H+ and OH- ions
What happens to OH- ions produced from the splitting of water in parietal cells?
They combine with CO2 from metabolsim to from HCO3-, which is exported to the blood
How much HCO3- enters the blood for every mole of H+ secreted into the stomach?
What allows parietal cells to produce H+ at a high rate?
They have lots of mitochondria
Can the ions produced in the mitochondria of parietal cells accumulate in the cell?