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77 Cards in this Set
- Front
- Back
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How much saliva is secreted per day?
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1000 ml
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pH of saliva
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6-7
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Sites of saliva secretion:
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-Parotid glands
-Submandibular glands -Sublingual glands -Small buccal glands |
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2 types of protein secretions in Saliva:
(what does each contain? |
Serous - contains Ptyalin for starch digestion
Mucus - contains mucin for lubrication / protection |
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What types of protein secretions are in Parotid glands?
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Only serous
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What types of protein secretions are in Submandibular glands?
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Both serous and mucus
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What types of protein secretions are in Sublingual glands?
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Both serous and mucus
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What types of protein secretions are in buccal glands?
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Only mucus
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General composition of saliva:
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-Rich in K and HCO3
-Low in Na / Cl |
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2 functional structures within the submandibular gland:
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-Acini cells
-Salivary ducts |
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What do Acini cells produce?
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Primary secretion composed of:
1. Ptyalin 2. Mucus 3. ECF |
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What happens to the primary secretion produced in acini?
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It flows through the salivary ducts and its composition gets modified by two major AT processes and 2 passive processes.
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What electrolyte changes occur during saliva formation?
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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 |
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How is saliva composition altered during rapid/maximal salivation?
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Saliva becomes like ECF
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What is the main controller of saliva secretion?
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PNS
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What does PNS activation do to salivary secretion?
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Increases it
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What excites the PNS sup/inf salivatory nuclei in the brainstem? (3 things)
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1. Taste/tactile stim in mouth
2. Higher CNS centers (appetite) 3. Stomach/duodenal reflexes --> salivate to flush out irritants or neutralize bad tastes. |
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What 2 other things regulate saliva secretion?
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1. SNS - minor; increases salivation
2. Blood perfusion |
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How is blood perfusion to salivary glands increased?
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By PNS activity which causes vasodilatin, Kallikrein release which splits a2-globulin to form Bradykinin
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Main component of Esophageal secretions: Why?
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Mucus - to protect the proximal esoph from excoriation by entering foods and distal esoph from acid reflux from stomach.
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3 types of Cells/Glands that produce Gastric Secretions:
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1. Mucus secreting cells (all over gastric epithel lining)
2. Oxyntic glands 3. Pyloric glands |
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Where are Oxyntic glands found? What do they secrete? (4 things)
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-Proximal 80% of stomach lining
-Secrete: HCl, Pepsinogen, IF, Mucus |
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Where are Pyloric glands found? What do they serete? (3 things)
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-Distal 20% of stomach lining
-Secrete: Mucus, Pepsinogen, and Gastrin |
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3 types of cells in Oxyntic Glands:
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1. Mucus neck cells
2. Peptic Chief cells 3. Parietal Oxyntic cells |
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What do Mucus neck cells secrete?
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-Mucus
-Pepsinogen |
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What do Peptic Chief cells secrete?
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Pepsinogen
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What do Parietal Oxyntic cells secrete?
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HCl and IF
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Special feature of Parietal oxyntic cells:
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-They contain large branching canaliculi where HCl is formed.
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What does the canaliculus of parietal cells function to do?
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Help make concentrated HCl solution by regulating active and passive transport of electrolytes
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What must occur for pepsinogen secreted by oxyntic glands to be active?
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-Contact with HCl
-Contact with preactivated Pepsin |
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How does acid activate Pepsinogen?
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It cleaves it
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What is required for Active Pepsin to function?
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Acidic environment between pH of 1.8-3.5
-No activity if pH is higher than this |
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What else is formed by Parietal cells in Oxyntic glands?
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Intrinsic factor
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What is the clinical importance of IF?
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-Vital for Vitamin B12 absorption
-Prevention of pernicious anemia |
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What are the pyloric glands mainly responsible for secreting?
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-Mucus
-Gastrin (some pepsinogen too) |
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Dominant cell type in pyloric glands:
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Mucous cells - identical to the neck cells in oxyntic glands.
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What is gastrin?
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A hormone that controls gastric secretion - stimulates ECF like cells to release histamine, thus parietal cells to release HCl.
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What glands cover the entire surface of the stomach mucosa?
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Surface mucous cells
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What is different about the mucus secreted by Surface mucus cells compared to Pyloric glands?
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It is much thicker
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What unique feature of Surface mucous gland mucus especially helps it protect the stomach lining?
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It is alkaline - so the underlying stomach wall isn't exposed to gastric acidic secretions.
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What stimulates secretion from the pyloric glands?
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Any contact with food or irritants.
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What cells secrete HCl?
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Only the parietal cells of the oxyntic glands
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Acidity of parietal cell secretions:
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0.8
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2 types of control of acid secretion:
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-Endocrine (gastrin)
-Nervous |
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What cells operate in close association with parietal cells?
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ECL cells - enterochromaffin like cells.
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What is the function of ECL cells?
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To secrete histamine
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How are secretions of parietal and ECL cells related?
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Directly proportional - when ECl cells secrete histamine, parietal cells will secrete HCl.
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What is the primary stimulator for histamine release from ECL cells?
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Gastrin hormone from the pyloric glands in the antral stomach
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What causes Gastrin release?
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Presence of protein in the stomach
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2 other stimulants for histamine release from ECL cells (other than Gastrin):
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1. ACh from stomach vagal nerve endings
2. Hormones from ENS in stomach wall |
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What cells secrete Gastrin?
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G-cells in the pyloric glands of the distal (antral) stomach.
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2 forms of Gastrin:
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Large - 34 AA
Small - 17 AA Predominant type |
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How does gastrin stimulate histamine relase from ECL cells?
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After being secreted from the antral portion of the stomach it gets to the body by mixing.
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How is Gastrin-stimulated acid secretion controlled?
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By the ACIDITY of the stomach; when pH falls below 3, gastrin will not stimulate Histamine and HCl secretion.
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What are the 2 main effects of pH below 3 on acid secretion from parietal cells?
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1. DIRECTLY Blocks G-cells from secreting Gastrin
2. Low pH causes inhibitory NERVE reflexes that inhibit gastrin secretion |
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So the two types of regulation of gastric secretion are:
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-Neural via Vagal ACh
-Hormonal via Gastrin and Histamine |
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What in general activates all types of secretion in gastric glands?
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ACh - stimultates:
-Pepsinogen from peptic cells -HCl from parietal cells -Mucus |
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3 phases of gastric secretion:
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1. Cephalic
2. Gastric 3. Intestinal |
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When does the cephalic phase of gastric secretion occur?
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Before food enters stomach; while being eaten
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What stimulates the cephalic phase?
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Sight, smell, thought, taste.
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Where do the neurogenic signals for the cephalic phase originate?
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The cerebral cortex and appetite centers
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How are the signals for the cephalic phase transferred to the stomach?
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Via vagus nerves from the dorsal motor nuclei of the vagi
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When does the Gastric phase of gastric secretion occur?
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When food enters the stomach
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What 3 reflexes occur in the gastric phase to increase secretions?
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1. Vasovagal reflexes
2. Local enteric reflexes 3. Gastrin mechanism of acid secretion |
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What percentage of gastric secretions are a result of the
-Cephalic phase -Gastric phase |
Cephalic: 20%
Gastric: 70% |
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When does the Intestinal phase of gastric secretions start?
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When food is present in the duodenum
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What does food in the duodenum do to gastric secretions?
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Stimulates them to continue
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How does the duodenum stimulate gastric secretion?
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A small amt of GASTRIN is released from duodenal mucosa in response to distention; gets back to stomach via blood.
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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. |
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Why does chyme in the SI stimulate gastric secretion during the intestinal phase?
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Because during the intestinal phase of gastric secretion that's what should happen.
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Why does chyme in the SI INHIBIT gastric secretion during the GASTRIC phase?
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Because when there is already food in the small intestine you don't want the stomach to empty - hence the enterogastric reflex.
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What is the reflex that inhibits gastric secretion during the gastric phase?
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Enterogastric reflex
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Effects of the Enterogastric reflex:
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-Decreased gastric motility
-Decreased gastric secretion |
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What hormone is responsible for the enterogastric reflex?
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Secretin
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What does Secretin do?
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Controls pancreatic secretion and inhibits stomach secretion.
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What are 3 other hormones that work along with Secretin?
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GIP
VIP Somatostatin |
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What stimulates the release of SEcretin?
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protein in the SI
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