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77 Cards in this Set

  • Front
  • Back
How much saliva is secreted per day?
1000 ml
pH of saliva
Sites of saliva secretion:
-Parotid glands
-Submandibular glands
-Sublingual glands
-Small buccal glands
2 types of protein secretions in Saliva:
(what does each contain?
Serous - contains Ptyalin for starch digestion
Mucus - contains mucin for lubrication / protection
What types of protein secretions are in Parotid glands?
Only serous
What types of protein secretions are in Submandibular glands?
Both serous and mucus
What types of protein secretions are in Sublingual glands?
Both serous and mucus
What types of protein secretions are in buccal glands?
Only mucus
General composition of saliva:
-Rich in K and HCO3
-Low in Na / Cl
2 functional structures within the submandibular gland:
-Acini cells
-Salivary ducts
What do Acini cells produce?
Primary secretion composed of:
1. Ptyalin
2. Mucus
3. ECF
What happens to the primary secretion produced in acini?
It flows through the salivary ducts and its composition gets modified by two major AT processes and 2 passive processes.
What electrolyte changes occur during saliva formation?
1. Na reabsorption out of duct
2. K exchange for Na
3. Net neg charge -70 mV
4. Cl passive reabsorption out of duct
5. HCO3 put into duct in exchange for Cl
How is saliva composition altered during rapid/maximal salivation?
Saliva becomes like ECF
What is the main controller of saliva secretion?
What does PNS activation do to salivary secretion?
Increases it
What excites the PNS sup/inf salivatory nuclei in the brainstem? (3 things)
1. Taste/tactile stim in mouth
2. Higher CNS centers (appetite)
3. Stomach/duodenal reflexes --> salivate to flush out irritants or neutralize bad tastes.
What 2 other things regulate saliva secretion?
1. SNS - minor; increases salivation
2. Blood perfusion
How is blood perfusion to salivary glands increased?
By PNS activity which causes vasodilatin, Kallikrein release which splits a2-globulin to form Bradykinin
Main component of Esophageal secretions: Why?
Mucus - to protect the proximal esoph from excoriation by entering foods and distal esoph from acid reflux from stomach.
3 types of Cells/Glands that produce Gastric Secretions:
1. Mucus secreting cells (all over gastric epithel lining)
2. Oxyntic glands
3. Pyloric glands
Where are Oxyntic glands found? What do they secrete? (4 things)
-Proximal 80% of stomach lining
HCl, Pepsinogen, IF, Mucus
Where are Pyloric glands found? What do they serete? (3 things)
-Distal 20% of stomach lining
Mucus, Pepsinogen, and Gastrin
3 types of cells in Oxyntic Glands:
1. Mucus neck cells
2. Peptic Chief cells
3. Parietal Oxyntic cells
What do Mucus neck cells secrete?
What do Peptic Chief cells secrete?
What do Parietal Oxyntic cells secrete?
HCl and IF
Special feature of Parietal oxyntic cells:
-They contain large branching canaliculi where HCl is formed.
What does the canaliculus of parietal cells function to do?
Help make concentrated HCl solution by regulating active and passive transport of electrolytes
What must occur for pepsinogen secreted by oxyntic glands to be active?
-Contact with HCl
-Contact with preactivated Pepsin
How does acid activate Pepsinogen?
It cleaves it
What is required for Active Pepsin to function?
Acidic environment between pH of 1.8-3.5
-No activity if pH is higher than this
What else is formed by Parietal cells in Oxyntic glands?
Intrinsic factor
What is the clinical importance of IF?
-Vital for Vitamin B12 absorption
-Prevention of pernicious anemia
What are the pyloric glands mainly responsible for secreting?
(some pepsinogen too)
Dominant cell type in pyloric glands:
Mucous cells - identical to the neck cells in oxyntic glands.
What is gastrin?
A hormone that controls gastric secretion - stimulates ECF like cells to release histamine, thus parietal cells to release HCl.
What glands cover the entire surface of the stomach mucosa?
Surface mucous cells
What is different about the mucus secreted by Surface mucus cells compared to Pyloric glands?
It is much thicker
What unique feature of Surface mucous gland mucus especially helps it protect the stomach lining?
It is alkaline - so the underlying stomach wall isn't exposed to gastric acidic secretions.
What stimulates secretion from the pyloric glands?
Any contact with food or irritants.
What cells secrete HCl?
Only the parietal cells of the oxyntic glands
Acidity of parietal cell secretions:
2 types of control of acid secretion:
-Endocrine (gastrin)
What cells operate in close association with parietal cells?
ECL cells - enterochromaffin like cells.
What is the function of ECL cells?
To secrete histamine
How are secretions of parietal and ECL cells related?
Directly proportional - when ECl cells secrete histamine, parietal cells will secrete HCl.
What is the primary stimulator for histamine release from ECL cells?
Gastrin hormone from the pyloric glands in the antral stomach
What causes Gastrin release?
Presence of protein in the stomach
2 other stimulants for histamine release from ECL cells (other than Gastrin):
1. ACh from stomach vagal nerve endings
2. Hormones from ENS in stomach wall
What cells secrete Gastrin?
G-cells in the pyloric glands of the distal (antral) stomach.
2 forms of Gastrin:
Large - 34 AA
Small - 17 AA Predominant type
How does gastrin stimulate histamine relase from ECL cells?
After being secreted from the antral portion of the stomach it gets to the body by mixing.
How is Gastrin-stimulated acid secretion controlled?
By the ACIDITY of the stomach; when pH falls below 3, gastrin will not stimulate Histamine and HCl secretion.
What are the 2 main effects of pH below 3 on acid secretion from parietal cells?
1. DIRECTLY Blocks G-cells from secreting Gastrin
2. Low pH causes inhibitory NERVE reflexes that inhibit gastrin secretion
So the two types of regulation of gastric secretion are:
-Neural via Vagal ACh
-Hormonal via Gastrin and Histamine
What in general activates all types of secretion in gastric glands?
ACh - stimultates:
-Pepsinogen from peptic cells
-HCl from parietal cells
3 phases of gastric secretion:
1. Cephalic
2. Gastric
3. Intestinal
When does the cephalic phase of gastric secretion occur?
Before food enters stomach; while being eaten
What stimulates the cephalic phase?
Sight, smell, thought, taste.
Where do the neurogenic signals for the cephalic phase originate?
The cerebral cortex and appetite centers
How are the signals for the cephalic phase transferred to the stomach?
Via vagus nerves from the dorsal motor nuclei of the vagi
When does the Gastric phase of gastric secretion occur?
When food enters the stomach
What 3 reflexes occur in the gastric phase to increase secretions?
1. Vasovagal reflexes
2. Local enteric reflexes
3. Gastrin mechanism of acid secretion
What percentage of gastric secretions are a result of the
-Cephalic phase
-Gastric phase
Cephalic: 20%
Gastric: 70%
When does the Intestinal phase of gastric secretions start?
When food is present in the duodenum
What does food in the duodenum do to gastric secretions?
Stimulates them to continue
How does the duodenum stimulate gastric secretion?
A small amt of GASTRIN is released from duodenal mucosa in response to distention; gets back to stomach via blood.
How does intestinal chyme effect gastric secretions
-During the intestinal phase
-During the gastric phase
In a paradoxical way:
-During intestinal phase of gastric secretion chyme in SI stimulates secretion.
-During gastric phase SI chyme inhibits gastric secretion.
Why does chyme in the SI stimulate gastric secretion during the intestinal phase?
Because during the intestinal phase of gastric secretion that's what should happen.
Why does chyme in the SI INHIBIT gastric secretion during the GASTRIC phase?
Because when there is already food in the small intestine you don't want the stomach to empty - hence the enterogastric reflex.
What is the reflex that inhibits gastric secretion during the gastric phase?
Enterogastric reflex
Effects of the Enterogastric reflex:
-Decreased gastric motility
-Decreased gastric secretion
What hormone is responsible for the enterogastric reflex?
What does Secretin do?
Controls pancreatic secretion and inhibits stomach secretion.
What are 3 other hormones that work along with Secretin?
What stimulates the release of SEcretin?
protein in the SI