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85 Cards in this Set

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