1.
A scientist genetically engineers a mouse to lack the hormone secretin. Compared with a normal animal, which of the following would be expected to be increased in the mutant mouse?
Correct Answer
D. Susceptibility to duodenal erosions and ulcerations
Explanation
Secretin is a hormone that stimulates the release of bicarbonate-rich pancreatic juice into the duodenum to neutralize the acidic chyme from the stomach. Without secretin, the pH of pancreatic ductular secretion would be decreased, as there would be less bicarbonate secretion. The volume of pancreatic secretion would also be decreased since secretin plays a role in stimulating pancreatic enzyme secretion. The pH of duodenal contents would be decreased as well, due to the lack of bicarbonate secretion. However, the absence of secretin would not directly affect gallbladder contractility. Therefore, the only expected increase in the mutant mouse would be susceptibility to duodenal erosions and ulcerations, as the acidic chyme would not be properly neutralized.
2.
A 50-year-old male patient comes to his primary care physician complaining of a chronic burning sensation in his chest. The pain is worse when lying down at night after a meal, and can be alleviated to some degree by the use of over-the-counter antacids. The pain experienced by the patient is most likely due to dysfunction of which of the following gastrointestinal structures?
Correct Answer
B. Lower esopHageal spHincter
Explanation
The chronic burning sensation in the chest, worsened by lying down at night after a meal, and relieved by antacids, suggests gastroesophageal reflux disease (GERD). The lower esophageal sphincter (LES) is responsible for preventing the backflow of stomach acid into the esophagus. Dysfunction of the LES can lead to acid reflux and the symptoms described by the patient. Therefore, the pain experienced by the patient is most likely due to dysfunction of the lower esophageal sphincter.
3.
As part of a diagnostic test, a gastroenterologist uses an endoscope to deliver a bolus of dilute acid into the distal esophagus. The bolus is sufficient to cause esophageal dilatation. In a normal individual, the bolus will be cleared from the esophagus predominantly by which of the following?
Correct Answer
E. Secondary peristalsis
Explanation
In a normal individual, the bolus will be cleared from the esophagus predominantly by secondary peristalsis. Secondary peristalsis is a reflexive contraction of the esophageal muscles that occurs in response to the presence of a bolus in the esophagus. This reflex helps to propel the bolus further down the esophagus and into the stomach. Primary peristalsis, on the other hand, is the normal rhythmic contraction of the esophageal muscles that occurs during swallowing to move the bolus from the mouth to the stomach. While swallowing and relaxation of the upper esophageal sphincter also play a role in clearing the bolus, secondary peristalsis is the primary mechanism for clearance in this scenario.
4.
Mr. Simms is having lunch at his team's practice facility. As he swallows food, his stomach changes size to accommodate his meal. What motor neurons specifically mediate this response at the smooth muscle level?
Correct Answer
D. Inhibitory neurons from the myenteric plexus
Explanation
The correct answer is inhibitory neurons from the myenteric plexus. These neurons mediate the response of the smooth muscles in the stomach by inhibiting their contraction, allowing the stomach to expand and accommodate the meal.
5.
Which of the following pattern of smooth muscle contraction is characteristic of the stomach and small intestines during a period of fasting?
Correct Answer
C. Migrating motor complex
Explanation
The migrating motor complex is a pattern of smooth muscle contraction that occurs in the stomach and small intestines during a period of fasting. It is characterized by a coordinated, sequential contraction and relaxation of the smooth muscles, which helps to clear any residual food particles and bacteria from the digestive tract. This pattern of contraction is important for maintaining the health and function of the gastrointestinal system during periods of fasting.
6.
In the control of gastric motility, there are several factors that inhibit motility and/or promote relaxation, including duodenal hormones such as cholecystokinin (CCK). What is the primary signal for release of CCK from intestinal cells into the blood?
Correct Answer
B. Fatty acids in the duodenum
Explanation
Fatty acids in the duodenum are the primary signal for the release of CCK from intestinal cells into the blood. When fatty acids are present in the duodenum, it triggers the release of CCK, which inhibits gastric motility and promotes relaxation. This is an important mechanism in the control of gastric motility, as it helps to regulate the digestion and absorption of fats in the small intestine.
7.
Which of the following neurotransmitters, hormones or paracrine substances has the greatest impact on acid secretion by the parietal cells of the gastric mucosa?
Correct Answer
A. Histamine
Explanation
Histamine has the greatest impact on acid secretion by the parietal cells of the gastric mucosa. Histamine acts on H2 receptors located on the parietal cells, stimulating the production and release of gastric acid. This is a key mechanism in the regulation of gastric acid secretion and plays a crucial role in the digestive process. Acetylcholine and gastrin also contribute to acid secretion, but histamine has been found to have the most significant impact. Somatostatin, on the other hand, inhibits acid secretion and acts as a negative regulator in the stomach.
8.
As the rate of secretion increases in both the salivary glands and pancreas, which of the following ions is found to increase most?
Correct Answer
D. Bicarbonate
Explanation
As the rate of secretion increases in both the salivary glands and pancreas, bicarbonate ions are found to increase the most. Bicarbonate ions are important in maintaining the pH balance in the body. They act as a buffer to neutralize excess acid in the stomach and help in the digestion process. Therefore, an increase in secretion rate would result in an increased production of bicarbonate ions to maintain the proper pH levels in the digestive system.
9.
A 22 year old university student, Ms. Smith, complains of pain in the central abdomen. It gradually increased in severity and became localized to the lower right abdomen. She developed nausea and vomiting as well. As the pain increased in intensity, she was brought to the ER where her was temperature was 38 degree C. What is the probable diagnosis?
Correct Answer
B. Acute appendicitis
Explanation
Based on the symptoms described, such as pain in the central abdomen that localized to the lower right abdomen, along with nausea, vomiting, and an increased temperature, the probable diagnosis is acute appendicitis. Acute appendicitis is characterized by inflammation of the appendix, which can cause severe abdominal pain and other associated symptoms. This condition often requires immediate medical attention and may require surgical intervention to remove the inflamed appendix.
10.
A patient presents with recurrent fatty diarrhea, malabsorption, weakness, anemia for about last 6 months. Which part of the gastro-intestinal system is most important for digestion and absorption?
Correct Answer
D. Small Intestine
Explanation
The small intestine is the most important part of the gastrointestinal system for digestion and absorption. It is responsible for the majority of nutrient absorption, including fats. The patient's symptoms of recurrent fatty diarrhea and malabsorption suggest that there is a problem with fat digestion and absorption, which is primarily carried out in the small intestine.
11.
As part of a research study, a volunteer undergoes a test known as scintigraphy, in which the transit of a swallowed soluble radioactively labeled tracer is tracked over time as it travels through the gut. Assuming this volunteer has normal gastrointestinal function, how long following the swallow would it take the tracer to appear in the colon?
Correct Answer
A. 7 - 10 hours
Explanation
Based on the information given, scintigraphy is a test that tracks the transit of a swallowed tracer through the gut. The question asks how long it would take for the tracer to appear in the colon. Since the colon is further down the gastrointestinal tract, it would take some time for the tracer to reach there. The correct answer of 7 - 10 hours suggests that it would take this amount of time for the tracer to travel through the gut and reach the colon.
12.
GI Histology
Which one of the following statements concerning the histological structures in the fundus/body region of the stomach is correct?
Correct Answer
C. Chief cells produce pepsin
Explanation
Chief cells are located primarily at the base of the gastric glands, not at the neck region. These cells are responsible for producing and secreting pepsinogen, which is then converted to pepsin in the presence of hydrochloric acid. Pepsin is an enzyme that helps in the digestion of proteins.
13.
As saliva passes through the striated duct, which of the following changes occurs?
Correct Answer
D. Active absorption of Na+
Explanation
As saliva passes through the striated duct, it undergoes active absorption of Na+. This means that the cells in the striated duct actively transport sodium ions from the saliva into the surrounding tissue. This process helps to regulate the concentration of sodium ions in the saliva and maintain the overall balance of electrolytes in the body.
14.
A transition from simple columnar epithelium with simple tubular glands (predominant cells are goblet) to non-keratinized stratified squamous epithelium are revealed in a histological slide. The sample is taken from one spot of the gastrointestinal tract. Based on the tissue types, which part of GI tube is under examination?
Correct Answer
E. Pectinate line
Explanation
The pectinate line is the transition zone between the simple columnar epithelium of the rectum and the non-keratinized stratified squamous epithelium of the anal canal. This transition occurs at the junction of the sigmoid colon and rectum. Therefore, based on the tissue types described in the question, the part of the GI tract under examination is the junction of the sigmoid colon and rectum.
15.
Which of the following statement concerning enteroendocrine cells (EEC) is correct?
Correct Answer
D. G cells are EECs and they produce gastrin
Explanation
G cells are a type of enteroendocrine cells (EEC) and they produce gastrin.
16.
Which of the following structures cannot be found in submandibular gland?
Correct Answer
D. Centroacinar cells
Explanation
Centroacinar cells cannot be found in the submandibular gland. These cells are located in the pancreas and are responsible for producing digestive enzymes. The submandibular gland, on the other hand, is a salivary gland that primarily secretes a mixture of mucus and serous fluid. Therefore, centroacinar cells are not present in the submandibular gland.
17.
Which one of the following statements concerning the histological structures in the fundus/body region of the stomach is correct?
Correct Answer
D. Gastric glands contain APUD cells.
18.
Parietal cells possess receptors for which of the following hormones?
Correct Answer
C. Gastrin
Explanation
Parietal cells possess receptors for gastrin. Gastrin is a hormone that stimulates the release of gastric acid in the stomach. Parietal cells are found in the stomach lining and are responsible for producing and secreting gastric acid. The presence of receptors for gastrin on parietal cells allows for the regulation of gastric acid production in response to the hormone.
19.
Which of the following structures is not a characteristic feature of small intestine?
Correct Answer
C. Rugae
Explanation
Rugae is not a characteristic feature of the small intestine. Rugae are folds or wrinkles that are typically found in the stomach and urinary bladder, not in the small intestine. The small intestine is lined with structures such as plicae circulars, microvilli, villi, and Peyer's patches, which aid in absorption and digestion.