11/13: Stomach Flashcards
What are the regions of the stomach?
Cardia, Fundus, body, pylorus
What is cardia surrounded by?
Lower esophagus sphincter smooth Mm
What does the cardia contain?
Predominantly mucus-secreting glands
What is the fundus?
Glandular portion of the stomach
What does the fundus secrete?
Acid, pepsin, and some mucus
The is the largest part of the stomach?
Body
Where is food mixed and starts to break down?
Body - contains acid and enzyme secreting glands
What does the pylorus or pyloric antrum contain?
Primarily mucus and gastrin secreting glands
What does the pyloric sphincter control?
Outflow from stomach into duodenum - smooth mm
What is the stomach?
Distensible organ used for food storage
What occurs to food in the stomach?
Undergoes mechanical breakdown via muscular activity & chemical breakdown via gastric secretions to form chyme
In addition to inner circular & outer longitudinal Mm layers of stomach, there is…
An inner oblique layer in the msucularis externa
Describe the absorption in the stomach?
Little absorption, except for water, alcohol, and some drugs (aspirin)
What are the stomach lining folds?
Rugae
What is the stomach lined by?
Simple columnar epithelium
What is contains in the glandular body of the stomach?
Gastric pits (=foveolae)
What do gastric pits form?
Entrance to gastric glands
What do gastric glands secrete?
2 liters watery gastric juice/day
What is contained in gastric gands?
HCl and pepsinogen (inactive precursor of pepsin, hydrolyzes protein)
What is pepsinogen converted to and how?
Pepsin; action of HCl
What is the mucosa protected by?
Thick layer of mucus
What cells do gastric glands contain?
5 different classes
What does gastric epithelium secrete?
Acid, digestive enzymes and mucus. Also contain hormone-secreting cells
What are the secretions of the gastric epithelium?
- hydrochloric acid (HCl)
- proteolytic enzyme (primarily pepsin)
- Mucus (mainly neutral mucus)
What are cells of the gastric epithelium?
- Acid producing parietal cells
- Enzyme-producing chief
cells - Mucus-secreting cells
(surface and neck cells). - Stem cells
- Enteroendocrine cells
What do surface mucus cells secrete?
Thick, insoluble mucus &
bicarbonate ions
Where are surface mucus cells located?
On surface
What do mucus neck cells secrete?
soluble mucus
Where are mucus neck cells located?
upper third of pit, at neck of gastric gland
What do parietal cells secrete?
HCl
What do parietal cells produce?
Intrinsic factor which is necessary for absorption of vitamin B12
What does pepsin break down?
Large protein molecules into small peptides
What are acid secreting cells?
Parietal cells = oxyntic cells
What exactly do parietal cells secrete?
Secrete HCl & intrinsic factor (necessary for absorption of Vit B12 from ileum)
Where are parietal cells most numerous?
In middle third of gland, stain pink to purple
What are pepsin secreting cells?
Chief cells, peptic cells, or zymogenic cells
What do chief cells secrete?
Inactiva pepsinogen
Where are chief cells located?
Base of gland (bottom third); stain purple due to large # of ribosomes
What is the lifespan of parietal and chief cells?
Long; replaced about 1 yr
What are parietal and chief cells controlled by?
Autonomic nervous system and hormones from endocrine cells in pylorus
What are cells that have a paracrine function, which control motility of GI tract?
Enteroendocrine cells
What do enteroendocrine cells do?
secrete a variety of peptide hormones in response to local factors; control GI motility, gastric secretion
What does gastrin do?
Stimulates secretion of HCl and pepsin
What do somatostatin “d” cells do?
Inhibits secretion of gastrin
What does secretin do?
Inhibits gastric secretion and stimulates smooth mm contraction
What is the function of undifferentiated stem cells?
Continuously divide to replace lost or damaged epithelial cells
As mature, migrate up or down gland
What is gastritis caused by?
Irritation due to excessive alcohol use, chronic vomitting, stress, or use of medications such as aspirin or other anti-inflammatories
What is a bacteria that lives in the mucous lining
of the stomach; without treatment, the infection can lead to ulcers, and in
some people, stomach cancer?
Helicobacter pylori (H. pylori)
What is a backflow of bile into the stomach from the bile tract (that connects to the liver and gallbladder)?
Bile reflux
What are ulcers associated with?
Chronic infection of H. pylori
What is produced by h.pylori?
Urease
What does urease do?
Increase gastric pH -> secondary increase in acid production
What is treatment for h. pylori infection?
“triple therapy”
Long term abx and proton pump inhibitor (prevents H+ secretion)
What are stomach ulcers?
Type of peptic ulcer disease
What are peptic ulcers?
Any ulcers that affect both the
stomach and small
intestines
