BSI 2 Lecture 64: Mouth, Esophagus, and Stomach Flashcards
What is the composition of saliva from the parotid, submandibular, and sublingual glands?
99.5% water and 0.5% solutes
What makes up the 0.5% solute?
- lingual lipase
- salivary amylase
- ions
- mucus
- IgA
- bacterial lysozyme
What is lingual lipase?
A digestive enzyme that works on triglycerides
Where is lingual lipase activated?
In the stomach
What is salivary amylase?
A digestive enzyme that acts on carbohydrates
Does each salivary gland secrete the same proportion of water and solutes?
No
What stimulates the salivation?
parasympathetic nervous system
What happens to food in the mouth?
- Begins to dissolve in saliva
- salivary amylase digests starch
- Food is reduced to bolus
What happens in the esophagus?
Peristalsis pushes food down by coordinated contractions . No further digestion or absorption takes place.
What happens in the stomach?
- Bolus is turned into chyme
- Pepsinogen is activated to pepsin by HCl and digests proteins
- Lingual lipase is activated and breaks down fats
What is absorbed in the stomach?
water, ions, short chain fatty acids, certain drugs, and alcohol
What types of cells are in the gastric glands?
- Mucous cells
- Parietal cells
- Chief Cells
- G cells
- D cells
- ECL cells
What do mucous cells do?
secrete a mucous that prevents digestion of the cell wall
What do parietal cells do?
secrete HCl and intrinsic factor
What is the function of HCl?
- kill microbes
- denature proteins
- activate pepsinogen
- stimulate secretion of hormones that promote flow of bile and pancreatic juice
- allow for absorption of some drugs
What is HCl secretion stimulated by?
- acetylcholine
- gastrin
- histamine
What is HCl secretion inhibited by?
- somatostatin
- prostaglandins
- CCK (cholecystokinin)
What are the function of vitamin B12?
- coenzyme in amino acid metabolism
- stimulates erythropoiesis
- energy production
- normal functioning of nervous system
- folate metabolism
What are the signs and symptoms of vitamin B12 deficiency?
- anemia
- fatigue
- depression
- poor memory
- neurological abnormalities
- GI symptoms
How is B12 absorbed?
Gastric acids release B12 from foods and R proteins bind. Pancreatic enzymes degrade the R proteins in the duodenum and intrinsic factor binds, the intrinsic factor/B12 complex is absorbed in the distal ileum via receptor-mediated endocytosis
What is a side function of intrinsic factor?
It protects B12 from being catabolized by intestinal bacteria
What do chief cells do?
Secrete pepsinogen and gastric lipases
How can pepsinogen be activated?
By contact with other active pepsin molecules or HCl
What do G cells do?
Secrete gastrin into the bloodstream
What does gastrin do?
- stimulate parietal cells, chief cells, and ECL cells
- increases motility
- relaxes pyloric sphincter
- increases activity of stomach
What do D cells do?
Secrete somatostatin
What do ECL cells do?
Secrete histamine
