Salivary and Gastrointestinal Physiology Quiz

<p>Decreases saliva secretion (B)</p> Signup and view all the answers

<p>Pepsinogen (A)</p> Signup and view all the answers

<p>Nervous system stimulation (D)</p> Signup and view all the answers

<p>Composition closest to plasma (C)</p> Signup and view all the answers

<p>Inositol 1,4,5-triphosphate (IP3) (B)</p> Signup and view all the answers

<p>Parietal cells (A)</p> Signup and view all the answers

<p>They contract to eject saliva into the mouth. (B)</p> Signup and view all the answers

<p>Increases the production, but less than parasympathetic stimulation (A)</p> Signup and view all the answers

<p>H+, K+-ATPase in parietal cells (A)</p> Signup and view all the answers

<p>Na+ and Cl- are reabsorbed while K+ and HCO3- are secreted. (B)</p> Signup and view all the answers

<p>Saliva has lower K+ concentration at high flow rates. (B)</p> Signup and view all the answers

<p>The pH of the blood increases, causing alkaline tide (C)</p> Signup and view all the answers

<p>Pepsinogen (D)</p> Signup and view all the answers

<p>By both the parasympathetic and sympathetic nervous systems. (B)</p> Signup and view all the answers

<p>Decreases saliva production (C)</p> Signup and view all the answers

<p>Cranial nerves VII and IX (C)</p> Signup and view all the answers

<p>It increases Na+ reabsorption. (C)</p> Signup and view all the answers

<p>Both gastric H+ and pancreatic HCO3- secretion are prevented (A)</p> Signup and view all the answers

<p>Because the ducts reabsorb more solute than water. (D)</p> Signup and view all the answers

<p>Sympathetic stimulation is less important than parasympathetic. (A)</p> Signup and view all the answers

<p>Inhibition of gastrin secretion (A)</p> Signup and view all the answers

<p>By inhibiting the release of histamine and gastrin (C)</p> Signup and view all the answers

<p>They activate G_i proteins to inhibit H⁺ secretion (C)</p> Signup and view all the answers

<p>Prostaglandins, mucus, and HCO₃^- (D)</p> Signup and view all the answers

<p>Development of gastric ulcers (C)</p> Signup and view all the answers

<p>Mucosal blood flow (B)</p> Signup and view all the answers

<p>They inhibit further secretion when pH is below 3.0 (C)</p> Signup and view all the answers

<p>Loss of the mucosal barrier (B)</p> Signup and view all the answers

<p>HCl and Intrinsic factor (C)</p> Signup and view all the answers

<p>Pepsinogen (C)</p> Signup and view all the answers

<p>Vagal stimulation and small peptides (B)</p> Signup and view all the answers

<p>It neutralizes acidic chyme in the duodenum (C)</p> Signup and view all the answers

<p>Na+ and Cl- (B)</p> Signup and view all the answers

<p>They secrete HCO3- and absorb Cl- (B)</p> Signup and view all the answers

<p>Ductal cells are primarily responsible for secreting enzymes. (A)</p> Signup and view all the answers

<p>Somatostatin and H+ concentration (C)</p> Signup and view all the answers

<p>On the outside, with hydrophilic portions in the aqueous solution and hydrophobic portions in the micelle interior (B)</p> Signup and view all the answers

<p>Choleretic agents (D)</p> Signup and view all the answers

<p>They are converted to secondary bile acids by bacteria (D)</p> Signup and view all the answers

<p>To signal the gallbladder to contract and release bile (B)</p> Signup and view all the answers

<p>Bile is pushed into the duodenum (A)</p> Signup and view all the answers

<p>They are excreted in feces, leading to fat absorption impairment (B)</p> Signup and view all the answers

<p>To facilitate the recirculation of bile acids to the liver (D)</p> Signup and view all the answers

<p>Via isosmotic absorption of solutes and water (A)</p> Signup and view all the answers

Saliva is a fluid produced by salivary glands in the mouth. It plays a crucial role in the initial stages of digestion by breaking down starch and lubricating food.

Saliva is mainly composed of water and contains important enzymes like α-amylase for starch digestion and lingual lipase for fat digestion. It also contains electrolytes like potassium and bicarbonate.

Saliva's composition can vary depending on its flow rate. When flow is low, saliva has lower salt and bicarbonate levels but higher potassium. As flow increases, its composition becomes more like plasma.

The salivary glands, including the parotid, submandibular, and sublingual glands, produce saliva. Their structure resembles a cluster of grapes. Each gland starts with an acinus that generates the initial saliva and then modifies it as it travels through the duct system.

The acinus is the initial part of a salivary gland where saliva production starts. These are lined with acinar cells that secrete the primary saliva.

The duct system in salivary glands modifies the initial saliva by adjusting its composition. It is lined with columnar epithelial cells that regulate the final saliva.

The salivary glands are responsible for initial starch digestion through the enzyme α-amylase and some fat digestion through lingual lipase. They lubricate food with mucus, protect the mouth and esophagus by diluting and buffering ingested food.

The parotid glands are located in the cheeks, while the submandibular glands are found under the jaw. The sublingual glands are located under the tongue.

Initial saliva produced by the acinus is similar in composition to plasma. It is isotonic with the same concentrations of Na+, K+, Cl-, and HCO3-.

Ducts modify saliva by reabsorbing Na+ and Cl-, and secreting K+ and HCO3-. This makes saliva hypotonic.

Aldosterone acts on the ducts to increase Na+ reabsorption and K+ secretion.

High flow rate means more initial saliva passes through the ducts, resulting in saliva closer to the initial composition. Na+ and Cl- high, K+ low.

Low flow rate means more time for reabsorption and secretion, resulting in saliva with lower Na+ and Cl- and higher K+.

Saliva production is regulated by the sympathetic and parasympathetic nervous systems, not GI hormones, with parasympathetic being more important.

Parasympathetic stimulation increases saliva production by increasing transport processes in acinar and ductal cells, and causing vasodilation. It acts on muscarinic receptors.

Sympathetic stimulation also increases saliva production, though less than parasympathetic.

The second messenger for sympathetic stimulation of salivary glands, increasing cAMP levels.

Parasympathetic stimulation increases saliva production, while sympathetic stimulation has a smaller effect.

Parietal cells are located in the body of the stomach and secrete HCl and intrinsic factor.

Chief cells secrete pepsinogen, a precursor to pepsin, which begins protein digestion in the stomach.

G cells, located in the antrum of the stomach, secrete gastrin, a hormone that stimulates gastric acid production.

The H⁺-K⁺ pump in parietal cells actively transports protons (H⁺) into the stomach lumen, in exchange for potassium (K⁺).

Omeprazole, a proton pump inhibitor, blocks the H⁺-K⁺ pump, preventing HCl secretion and reducing stomach acidity.

Bicarbonate (HCO₃^-) produced in parietal cells is absorbed into the bloodstream in exchange for chloride (Cl^-).

When the stomach pH drops below 3.0, gastrin secretion is inhibited, leading to a reduction in gastric H+ secretion. This negative feedback mechanism helps regulate stomach acidity.

Somatostatin, a hormone, inhibits H+ secretion by directly acting on parietal cells and indirectly by reducing histamine and gastrin release.

Prostaglandins, signaling molecules, inhibit H+ secretion by reducing cAMP levels and protecting the stomach lining.

Peptic ulcer disease occurs when the protective mucosal barrier in the stomach or duodenum is damaged, leading to excessive H+ and pepsin activity. This can be caused by factors like H. pylori, NSAIDs, and stress.

Gastric ulcers, a type of peptic ulcer, lead to damage in the stomach lining and a reduction in H+ secretion as acid leaks back out.

Mucus, bicarbonate, prostaglandins, blood flow, and growth factors protect the stomach lining from damage. H+ , pepsin, H. pylori, NSAIDs, stress, smoking, and alcohol have damaging effects.

The parietal cells are the cells responsible for producing and secreting gastric acid (H+).

Negative feedback mechanisms, like low stomach pH inhibiting gastrin, help regulate H+ secretion to maintain proper stomach acidity.

Micelles are tiny spheres with a hydrophobic core and a hydrophilic outer layer. They are formed in the small intestine to help absorb dietary fats.

Bile salts are produced by the liver and stored in the gallbladder. They help emulsify fats, breaking them down into smaller droplets.

Bile is a digestive fluid produced by the liver and stored in the gallbladder. It's released into the small intestine to help digest fats.

Cholesterol is the starting material for creating bile acids. Hepatocytes in the liver transform cholesterol into primary bile acids.

Cholic acid and chenodeoxycholic acid are the two primary bile acids. They are produced by the liver from cholesterol.

Deoxycholic acid and lithocholic acid are secondary bile acids, formed from primary bile acids by bacteria in the intestines.

Bile acids are conjugated with glycine or taurine, resulting in the formation of bile salts. They are named according to their parent bile acid (e.g., taurocholic acid comes from cholic acid).

Cholecystokinin (CCK) is a hormone that stimulates the gallbladder to release bile. It's released in response to food, particularly fats, in the duodenum.

The main role of the pancreas is to produce pancreatic juice, which contains a high concentration of bicarbonate ions to neutralize the acidic chyme from the stomach and digestive enzymes for protein, carbohydrate, and fat digestion.

Pancreatic juice is characterized by its relatively high volume, similar sodium and potassium levels to blood plasma, significantly higher bicarbonate concentration compared to plasma, lower chloride concentration than plasma, and isotonic nature. It also contains pancreatic lipase, amylase, and proteases.

The pancreatic juice composition varies with flow rate. At low flow, the fluid is primarily sodium and chloride, whereas at high flow, it is dominated by sodium and bicarbonate. However, regardless of the flow rate, the juice remains isotonic.

The pancreas's exocrine structure is similar to a cluster of grapes, with acinar cells forming the majority of its weight.

Acinar cells in the pancreas are responsible for producing a small volume of initial pancreatic secretion, which mainly consists of sodium and chloride ions.

Ductal cells are responsible for modifying the initial pancreatic secretion by secreting bicarbonate ions and absorbing chloride ions through a Cl^--HCO₃^- exchanger. Due to the ducts' permeability to water, water moves into the lumen to maintain isotonicity.

Pancreatic secretion is stimulated by various factors, including vagal nerve stimulation, secretin released by the duodenum in response to acidic chyme, and cholecystokinin (CCK) released by the duodenum in response to fat and proteins.

The pancreas is stimulated to secrete bicarbonate ions by the hormone secretin, which is released from the duodenum in response to acidic chyme. This helps neutralize the acidic chyme before it reaches the small intestine.