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85 Cards in this Set
- Front
- Back
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Where are tubular glands located?
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In the stomach and upper duodenum
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What is secreted by the tubular glands?
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HCl and Pepsinogen
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The crypts of leiberkuhn are invaginations of the epithelium to what level?
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The submucosa
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What glands are drained by a single excretory duct?
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Parotid
Submandibular Buccal |
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Which glands exhibit sexual dimorphosism?
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Mandibular gland
Males = Serous Females = Mucous |
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What portions of salivary ducts receive both sympathetic and parasympathetic innervation?
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myoepithelial cells
intercalated ducts |
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What generates mechanical stimulation of local glands?
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1. Direct contact of food with the surface glandular cells
2. Epithelial stimulation activates the enteric nervous system via tactile, chemical and distension mechanisms. Neural activity causes increase secretion. |
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What is the rate of normal salivary secretion?
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30 ml/hr
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What is the rate of neural-stimulated salivary secretion?
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400 ml/hr
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What type of innervation will dramatically increase glandular secretion?
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Parasympathetic
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What is the sympathetic effect on glandular secretions?
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Slight to moderate increase when parasympathetic innervation is absent and a decrease in activity when parasympathetic innervation is high.
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What gland produces the majority of salivary secretions?
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Submandibular (2/3)
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How does sympathetic innervation decrease secretion from glands?
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Reduction in blood flow to the organ system
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What causes the release of hormonal regulators?
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Presence of food in the lumen (mechanical stimulation)
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Where does the synthesis of secretory substances take place?
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In the endoplasmic reticulum and golgi
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What ion modulates the release of secretory vesicles in the GI?
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Calcium dependent release
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What triggers stimulate the calcium dependent release of secretory vesicles at the apical surface?
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Neural stimulation
Hormonal signals Mechanical stimulation |
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Describe the mechanism by which water is passed through the glandular cell.
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Neural activity stimulates active transport of chloride into the cell. This causes an increase in + ions as well. This causes hyperosmolarity causes water to move in and rupture the surface of the cell.
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How does parasympathetic stimulation effect the membrane potential of glandular cell?
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Hyperpolarizes: Suggesting Cl- shift into the cell
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What is the significance of the amphoteric properties of glycoproteins in mucous?
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Can buffer acids and bases in small amounts
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What is the function of mucous?
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Mucus allows for the easy passage of food along the GI tract and also prevents abrasions or chemical damage to the epithelium.
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Are salivary secretions essential to life?
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No
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What allows saliva to be lubricating?
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mucous component
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What is the function of saliva?
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Lubricating
Facilitates the swallowing process and is necessary for speech |
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What (6) components make up saliva?
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1. Serous
2. Mucous 3. Lactoferrin 4. Proteolytics 5. Thiocyanate 6. IgA binding proteins |
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What does lactoferrin do?
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Chelates iron to inhibit organismal growth
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What does thiocyanate do?
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bactericidal
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What enzyme is present in serous and what does it do?
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Ptyalin (alpha-amylase)
Starch digestion |
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What does the parotid gland secrete?
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Serous
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What do submandibular and sublingual glands secrete?
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Mucous and serous
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What do the Buccal glands secrete?
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Mucous
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What is the primary secretion of saliva?
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amylase and/or mucin
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What modifications occur follow the initiation of primary secretion?
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1. Na reabsorption, K secretion, Cl reabsorption (due to negative potential)
2. Ca secreted, Bicarb reabsorbed |
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How is primary secretion altered with increased flow?
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secretion becomes less and less modified--becomes more like plasma
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How are the salivatory nuclei stimulated?
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via taste and tactile stimulation of the tongue, olfactory cortex, and stomach and upper GI irritation
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What neural stimulation stimulates the activity of myoepithelial cells?
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Parasympathetic
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What factors are released in response to parasympathetic stimulation of the salivary glands?
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a release of Kallikrein, resulting in the production of bradykinin (potent vasodilator) and also growth of the salivary glands
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What are some stimuli that cause glandular inhibition?
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sleep, fear, dehydration and fatigue
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What are some stimuli that cause glandular stimulation?
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Conditioned reflexes (Pavlov style)
Smell Taste Pressure Nausea |
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What center controls salivation?
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The salivary nucleus in the medulla
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Is associated with chronic ulceration’s of the buccal mucosa and with dental caries.
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Xerostomia
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Is absence of saliva.
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Congenital xerostomia
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Is atrophy of the glands and decreased saliva production. In cystic fibrosis, salivary sodium, calcium and protein are elevated
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Sjogren's syndrome
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Sodium concentrations are increased.
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Addison's disease
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Sodium concentrations are decreased as they are in primary aldosteronism and during pregnancy.
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Cushing's syndrome
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What disease other an tumors of the salivary glands can cause excessive salivation
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Parkinson's
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What drug can increase calcium and potassium concentrations in the saliva?
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Digitalis drugs
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What are the four components of gastric juice?
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1. Intrinsic factor
2. Hydrogen ions 3. Pepsin 4. Mucous |
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What is the role of the intrinsic factor in the gastric juice?
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B12 absorption in the ileum
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What portion of the stomach is the oxyntic gland area and what does it do?
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Proximal 80%
Produces acid |
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What is the distal 20% of the stomach called and what does it do?
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Antrum/pyloric region
Produces gastrin |
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What principle cells are found in the oxyntic glands mucous of the stomach?
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Parietal cells--HCl
Chief cells--pepsinogen |
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G cells which secrete gastrin, replace parietal cells in which area of the stomach?
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Antrum/pyloric region
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What cells migrate to give rise to parietal (bottom), G (bottom), and mucous cells (top)?
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Mucous neck cells
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What is the concentration of HCl that is produced by the 1 billion parietal cells in the average human stomach?
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150-160 mmol/L @ pH 0.8-1
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How many Calories are required to make 1 liter of gastric juice?
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1500 Calories
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Explain the role of K in acid secretion.
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K conductance surges allowing K to leak into the lumen. K/H antiport is then used to transport H into the lumen.
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What are the three stimuli that regulate gastric secretion?
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Vagal nerve
Gastrin Histamine |
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Which NT will stimulate the secretion of pepsinogen, HCl, Mucous, and gastrin?
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ACh
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What hormones will strongly stimulate the release of HCl from parietal cells?
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Gastrin
Histamine |
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What receptor does histamine use to stimulate acid secretion? What drug can block this receptor?
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H2 receptor
cimentidine |
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What can cimentidine be used for?
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To block acid secretion via the histamine pathway
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What cells release histamine?
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mast cells in the lamina propria
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What is the primary trigger for acid secretion?
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Histamine
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What are the three phases of gastric secretion?
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1. Cephalic
2. Gastric 3. Intestinal |
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In which centers does the cephalic phase of gastric secretion originate?
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Cerebral cortex
amygdala Hypothalamus |
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What efferent fibers signal the cephalic phase? What do they signal?
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Vagus
Dorsal motor of the vagus Signal G cells to secrete gastrin (stimulates HCl from parietal cells) |
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What % of the gastric secretion is associated with the cephalic phase?
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30%
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Describe the gastric phase.
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Distension and partially digested protein in the stomach will signal the release of more HCl from parietal cells (short enteric reflex) and gastrin via a vagovagal reflex (long reflex).
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What % if the gastric secretion is associated with the gastric phase?
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60%
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Describe the intestinal phase of gastric secretion.
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10% of gastric juice can be secreted in the intestine via stimulation of by protein in the upper duodenum.
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What is enterooxyntin?
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Hormone secreted by endocrine cells in response to distension in the intestine to stimulate acid secretion.
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What process functions to inhibit gastric secretion?
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Enterogastric reflex
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What signals are used by the enterogastric reflex to inhibit gastric secretion?
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Vagus
ENS SNS |
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What signals can stimulate the enterogastric reflex?
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Distension in the duodenum
Acid in the upper intestine Protein breakdown products Irritation of the mucosa |
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What are enterogasterones and what causes their release?
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Hormones that are released by duodenal mucosa in response to acid, fatty acids or hyperosmotic solutions
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What is the function of enterogastrones?
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Stops gastric emptying and acid secretion
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What enterogastrone is responsible for inhibition of gastric secretion and emptying of bile from the gallbladder?
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CCK
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Is gastric motility increased or decreased with inhibition of gastric secretion?
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decreased via the enterogastrones
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What cells secrete somatostatins and when?
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When pH is below 3.0, endocrine D cells secrete somatostatin to inhibit gastric secretion and the release of gastrin
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What cells can secrete pepsinogen?
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mucous and chief cells
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What is the active pH range for pepsin?
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1.8-3.5
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What cells release intrinsic factor for the absorption of B12?
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Parietal cells
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How is trypsinogen activated?
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By enterokinase and trypsin
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What four factors control pancreatic secretion?
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ACh from the vagus
Gastrin from gastric phase CCK when food enters duodenum Secretin when pH is low |
