Digestive System: Stomach Flashcards
What are the functions of the stomach?
Continue digestion of carbs
Storage (*primary function)
Some nutrient breakdown (mostly chemical, less physical)
What are the gross anatomical features of the stomach?
Concave lesser curvature
Convex greater curvature
Cardia: narrow region by gastroesophageal sphincter
Fundus: domed region filled with gas
Body/corpus: largest portion
Pylorus: constricted portion by pyloric sphincter
Rugae: longitudinal folds which allow for distention
Gastric pits: tiny depressions in stomach’s surface, 1 pit leads to more than one gland
What is the surface epithelium of the mucosa of the stomach?
Simple columnar
What are the functions of the surface mucosa cells of the stomach?
Produce thick visible mucus
Secrete bicarbonate ions (buffering)
Where are the regenerative cells found in the stomach?
Bases of pits
What makes up the lamina propria of the stomach?
Loose vascular CT present in small amounts between glands
What makes up the muscularis mucosae of the stomach?
Smooth muscle layers that is often arranged in three layers
What are the three layers of the stomach’s muscularis mucosae?
- Inner circular
- Outer longitudinal
- Outermost circular/oblique
Is the submucosa of the stomach vascular?
Yes, it is highly vascular
Where is the submucosa of the stomach located?
AVA (arteriovenous anastomosis)
What is the function of the AVA?
To shut down activity and secretion FAST
What is next to the inner circular layer of muscle in the stomach submucosa?
Submucosal (Meissner’s) plexus
What is the function of the submucosal plexus in the stomach?
To influence the mucosa through secretion, blood flow, and any limited muscle contractions
How many layers of muscularis externa are possible in the stomach? Where at?
3 layers; especially between the cardiac region and greater curvature (all smooth muscle)
What are the layers of the stomach’s muscularis externa?
- Innermost oblique
- Middle circular (well developed)
- Outer longitudinal (thin)
Where is the myenteric (Auerbach’s) plexus located in the stomach?
Between circular and longitudinal layers
What is the function of the myenteric plexus in the stomach?
To stimulate muscularis externa
Which is present in the stomach: serosa or adventitia?
Serosa
What three regions of the stomach is gastric histology based off of?
Cardiac, Gastric (fundus and body), Pyloric
Why do the cardiac glands have a coiled base in the cardiac region?
Due to shorter pits
What cells are present in the cardiac region of the stomach?
Primarily surface mucous, some neck mucous, a few DNES and parietal cells. NO chief cells
Which region of the stomach is the smallest and obtains much mucus?
Cardiac region
What are the boundaries of the gastric glands of the gastric region?
Extends from gastric pit to muscularis mucosae
What is another name for the gastric gland?
Zymogenic gland
What are the three regions in the gastric gland?
Isthmus, Neck, Base
How long do the surface mucous cells in the isthmus live?
3-5 days
What do the surface mucous cells of the isthmus produce?
Thick visible mucus that traps bicarbonate ions
What is the function of the surface mucous cells of the isthmus?
To protect mucosa from auto-digestion and the rougher components of chyme
What is another name for the DNES cells in the isthmus?
Enteroendocrine cells
What are types of DNES cells in the isthmus?
Type D, Type EC, Type G
What do the Type D DNES cells do?
Produce somatostatin which inhibits release of hormones/HCL by nearby DNES cells
What do the Type EC DNES cells do?
Produce serotonin and substance P which increases gut motility
What do the Type G DNES cells do?
Produce gastrin which stimulates HCL and pepsinogen secretion, aids in gut motility, acts as regenerative cells in body of stomach
How long do the mucous cells of the neck live?
6 days
What do the neck mucous cells produce?
A soluble, less alkaline mucus
What is the function of the neck mucous cells?
To lubricate gastric contents
Do the regenerative cells of the neck replace all cell types?
Yes
How long do the parietal (oxyntic) cells of the neck live?
150-200 days
What makes up the neck parietal cells?
Odd columnar with intracellular canaliculi
Do the parietal neck cells produce acid?
Yes, very strong HCL with a pH of 0.8 and buffered immediately to 1.2 pH
What do the parietal neck cells produce?
Very strong HCL
Gastric intrinsic factor
What is the function of the parietal neck cells?
Necessary for vitamin B12 absorption
What can chronic gastritis lead to?
Pernicious anemia
Low number of which cells can lead to low amounts of intrinsic factor?
Parietal cells
Low amounts of intrinsic factor causes what?
Decreases vitamin B12 absorption which is necessary for RBC maturation
Are there a lot of DNES cells present in the neck?
No, there are few
Where are the chief cells located? What is their other name?
Located in the base of the gastric region; also known as Zymogenic cells
How long do the chief cells live?
60-90 days
What do the chief cells produce?
Primarily pepsinogen and some gastric lipase
What is the purpose of pepsinogen? Gastric lipase?
Pepsinogen- break down proteins
Gastric lipase: break down fats
Are parietal cells present in the base?
Yes, some are
How long do the DNES cells of the base live? Are there many or few?
60-90 days, few are present
What types of cells are present in the isthmus of the gastric region?
Surface mucous cells DNES cells (Types D/EC/G)
What types of cells are present in the neck of the gastric region?
Neck mucous cells
Regenerative cells
Parietal (oxyntic) cells
DNES cells
What types of cells are present in the base of the gastric region?
Chief (zymogenic) cells
Parietal cells
DNES cells
How are the pits in the pyloric region of the stomach?
Deeper; very twisted and branched pyloric glands (shorter glands)
What types of cells are present in the pyloric region?
Surface mucus (primarily)
DNES cells
Parietal cells
Neck mucous cells
What do some of the neck mucous cells of the pyloric region produce?
Lysozyme
What is the pyloric sphincter?
The anatomical sphincter between the pylorus of the stomach and the duodenum
What are characteristics of an anatomical sphincter?
Well developed inner circular layer of muscle in muscularis externa
Inner circular layer in muscular externa can be independently controlled