Digestive system overview US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Digestive system overview. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Digestive system overview US Medical PG Question 1: During a surgical procedure to repair an abdominal aortic aneurysm, the surgeon must be careful to avoid injury to which of the following arterial structures that originates near the level of the renal vessels?
- A. Left renal artery (Correct Answer)
- B. Celiac trunk
- C. Right renal artery
- D. Superior mesenteric artery
Digestive system overview Explanation: ***Left renal artery***
- The **left renal artery** arises from the aorta usually just below the superior mesenteric artery, making it susceptible to injury during an **abdominal aortic aneurysm (AAA) repair** if the aneurysm extends proximally.
- Its proximity to the typical location of AAA, often near or involving the **infrarenal aorta**, necessitates careful identification and protection during clamping or graft placement.
*Celiac trunk*
- The **celiac trunk** originates higher up from the aorta, typically at the level of **T12-L1 vertebrae**, well above the common infrarenal AAA repair site.
- While important, it is generally less directly threatened during a typical infrarenal AAA repair compared to arteries immediately adjacent to or within the aneurysm sac.
*Right renal artery*
- The **right renal artery** also originates from the aorta near the level of the renal veins, but it is typically located more posteriorly and usually passes behind the inferior vena cava.
- Although it can be at risk, the left renal artery's course is often more anterior and directly in the field of dissection for the **aortic neck** during AAA repair.
*Superior mesenteric artery*
- The **superior mesenteric artery (SMA)** originates from the aorta proximal to the renal arteries, typically around the L1 vertebral level.
- While crucial, its origin is usually cephalad to the infrarenal aneurysm neck, making it generally less prone to direct injury during infrarenal AAA repair, though flow must be monitored.
Digestive system overview US Medical PG Question 2: An otherwise healthy 45-year-old man comes to the physician because of a painful ulcer on his tongue for 3 days. Examination shows a shallow, tender 5-mm wide ulcer on the lateral aspect of the tongue, adjacent to his left first molar. There is no induration surrounding the ulcer or cervical lymphadenopathy. A lesion of the cranial nerve responsible for the transmission of pain from this ulcer would most likely result in which of the following?
- A. Loss of taste from the supraglottic region
- B. Lateral deviation of the tongue
- C. Inability to wrinkle the forehead
- D. Decreased sensation in the upper lip
- E. Loss of sensation in the anterior two-thirds of the tongue (Correct Answer)
Digestive system overview Explanation: ***Loss of sensation in the anterior two-thirds of the tongue***
- The sensation of pain from the **anterior two-thirds of the tongue** is transmitted by the **lingual nerve**, which is a branch of the mandibular division (V3) of the **trigeminal nerve**. A lesion affecting this nerve would therefore cause loss of sensation in this region.
- The ulcer is located on the **lateral aspect of the tongue**, placing it within the distribution of the lingual nerve.
*Loss of taste from the supraglottic region*
- **Taste sensation** from the **supraglottic region** and epiglottis is primarily mediated by the **superior laryngeal nerve** (a branch of the vagus nerve, CN X), not the nerve responsible for pain sensation from the anterior tongue.
- A lesion of the lingual nerve would affect taste sensation from the **anterior two-thirds of the tongue** (carried by the chorda tympani, a branch of CN VII, which joins the lingual nerve), but not the supraglottic region.
*Lateral deviation of the tongue*
- **Lateral deviation of the tongue** (towards the side of the lesion) occurs due to damage to the **hypoglossal nerve (CN XII)**, which innervates the intrinsic and extrinsic muscles of the tongue.
- This is a motor deficit, whereas the question describes a sensory issue related to pain transmission from an ulcer on the tongue.
*Inability to wrinkle the forehead*
- The **inability to wrinkle the forehead** (along with other facial expressions) results from damage to the **facial nerve (CN VII)**, specifically its temporal branch.
- This is a motor deficit affecting the muscles of facial expression, unrelated to pain sensation from the tongue.
*Decreased sensation in the upper lip*
- **Sensation in the upper lip** is supplied by the **infraorbital nerve**, a branch of the maxillary division (V2) of the **trigeminal nerve**.
- A lesion affecting the nerve responsible for pain from the anterior two-thirds of the tongue (lingual nerve, V3) would not directly impact sensation in the upper lip.
Digestive system overview US Medical PG Question 3: A 35-year-old woman presents with exertional dyspnea and fatigue for the past 3 weeks. She says there has been an acute worsening of her dyspnea in the past 5 days. On physical examination, the mucous membranes show pallor. Cardiac exam is significant for the presence of a mid-systolic murmur loudest in the 2nd left intercostal space. A CBC and peripheral blood smear show evidence of microcytic, hypochromic anemia. Which of the following parts of the GI tract is responsible for the absorption of the nutrient whose deficiency is most likely responsible for this patient’s condition?
- A. Duodenum (Correct Answer)
- B. Jejunum
- C. Terminal ileum
- D. Body of the stomach
- E. Antrum of the stomach
Digestive system overview Explanation: ***Duodenum***
- The patient's presentation with **exertional dyspnea**, **fatigue**, **pallor**, and **microcytic, hypochromic anemia** strongly indicates **iron deficiency anemia**.
- The **duodenum** is the primary site for **iron absorption** in the gastrointestinal tract, specifically in its acidic environment.
*Jejunum*
- The jejunum is primarily responsible for the absorption of most **nutrients** like carbohydrates, proteins, and fats.
- While some minimal iron absorption can occur here, it is not the main site for **dietary iron uptake**.
*Terminal ileum*
- The **terminal ileum** is the key site for the absorption of **vitamin B12** (cobalamin) and **bile salts**.
- Deficiency in vitamin B12 leads to **macrocytic anemia**, which is not consistent with this patient's microcytic anemia.
*Body of the stomach*
- The body of the stomach produces **hydrochloric acid** and **intrinsic factor** from parietal cells.
- While HCl is crucial for releasing iron from food, the stomach itself is not a primary site for **iron absorption**.
*Antrum of the stomach*
- The antrum of the stomach is mainly involved in **grinding food** and initiating digestion, as well as producing **gastrin**.
- It plays no direct role in the absorption of **iron** or other micronutrients responsible for the patient's anemic symptoms.
Digestive system overview US Medical PG Question 4: A 24-year-old woman comes to the emergency department because of abdominal pain, fever, nausea, and vomiting for 12 hours. Her abdominal pain was initially dull and diffuse but has progressed to a sharp pain on the lower right side. Two years ago she had to undergo right salpingo-oophorectomy after an ectopic pregnancy. Her temperature is 38.7°C (101.7°F). Physical examination shows severe right lower quadrant tenderness with rebound tenderness; bowel sounds are decreased. Laboratory studies show leukocytosis with left shift. An abdominal CT scan shows a distended, edematous appendix. The patient is taken to the operating room for an appendectomy. During the surgery, the adhesions from the patient's previous surgery make it difficult for the resident physician to identify the appendix. Her attending mentions that she should use a certain structure for guidance to locate the appendix. The attending is most likely referring to which of the following structures?
- A. Epiploic appendages
- B. Right ureter
- C. Deep inguinal ring
- D. Ileocolic artery
- E. Teniae coli (Correct Answer)
Digestive system overview Explanation: ***Teniae coli***
- The **teniae coli** are three distinct longitudinal bands of smooth muscle that run along the length of the cecum and colon, converging at the base of the **appendix**.
- Following these bands inferiorly from the ascending colon or cecum during surgery is a reliable method to locate the **vermiform appendix**, especially in the presence of adhesions.
*Epiploic appendages*
- These are small, fat-filled sacs that protrude from the surface of the **large intestine** but are not directly used as a reliable landmark for locating the appendix.
- While present in the vicinity, they do not consistently lead to the base of the appendix like the teniae coli.
*Right ureter*
- The **right ureter** is located retroperitoneally, deep to the cecum and appendix, and is not a direct anatomical landmark used for identifying the appendix during an appendectomy.
- Identifying the ureter is important to avoid injury, but not for localizing the appendix.
*Deep inguinal ring*
- The **deep inguinal ring** is an opening in the transversalis fascia, involved in the formation of the inguinal canal, and is located far anterior and inferior to the region of the appendix.
- It has no anatomical relationship that would guide a surgeon to locate the appendix.
*Ileocolic artery*
- The **ileocolic artery** branches from the superior mesenteric artery and supplies the terminal ileum, cecum, and appendix. While it provides blood supply to the appendix, it is not a direct or consistent surface landmark for locating the appendix itself, especially in complex cases with adhesions.
- Locating the artery would be more complex and less reliable for initial identification compared to the teniae coli.
Digestive system overview US Medical PG Question 5: A 75-year-old man presents to the clinic for chronic fatigue of 3 months duration. Past medical history is significant for type 2 diabetes and hypertension, both of which are controlled with medications, as well as constipation. He denies any fever, weight loss, pain, or focal neurologic deficits. A complete blood count reveals microcytic anemia, and a stool guaiac test is positive for blood. He is subsequently evaluated with a colonoscopy. The physician notes some “small pouches” in the colon despite poor visualization due to inadequate bowel prep. What is the blood vessel that supplies the area with the above findings?
- A. Ileocolic artery
- B. Superior mesenteric artery
- C. Inferior mesenteric artery (Correct Answer)
- D. Middle colic artery
- E. Right colic artery
Digestive system overview Explanation: ***Inferior mesenteric artery***
- The patient's **microcytic anemia** and **positive stool guaiac test** indicate chronic gastrointestinal blood loss, highly suggestive of **diverticulosis** presenting as "small pouches" in the colon.
- Diverticulosis commonly affects the **descending colon** and **sigmoid colon**, which are primarily supplied by branches of the **inferior mesenteric artery**.
*Ileocolic artery*
- The ileocolic artery is a branch of the **superior mesenteric artery** and supplies the **ileum**, **cecum**, and **ascending colon**.
- Diverticula are less commonly found in these regions compared to the left colon.
*Superior mesenteric artery*
- The superior mesenteric artery supplies the **midgut derivatives**, including the **small intestine** and the **right half of the large intestine** (up to the distal transverse colon).
- While it supplies a large portion of the GI tract, the typical location of diverticulosis (descending and sigmoid colon) is outside its primary distribution.
*Middle colic artery*
- The middle colic artery is a branch of the **superior mesenteric artery** and supplies the **transverse colon**.
- While diverticula can occur in the transverse colon, it is not the most common location, and the inferior mesenteric artery supplies the areas most frequently affected.
*Right colic artery*
- The right colic artery is a branch of the **superior mesenteric artery** and supplies the **ascending colon**.
- Diverticula are less frequently found in the ascending colon compared to the descending and sigmoid colon.
Digestive system overview US Medical PG Question 6: A 65-year-old man comes to the physician because of progressive abdominal distension and swelling of his legs for 4 months. He has a history of ulcerative colitis. Physical examination shows jaundice. Abdominal examination shows shifting dullness and dilated veins in the periumbilical region. This patient's abdominal findings are most likely caused by increased blood flow in which of the following vessels?
- A. Hepatic vein
- B. Superior rectal vein
- C. Left gastric vein
- D. Superior epigastric vein (Correct Answer)
- E. Superior mesenteric vein
Digestive system overview Explanation: ***Superior epigastric vein***
- This patient presents with signs of **portal hypertension**, including **jaundice**, **abdominal distension** (ascites), and **dilated periumbilical veins** (caput medusae). The **superior epigastric vein** is part of the **portosystemic anastomoses**, specifically connecting the **portal system** (via the paraumbilical veins) to the **systemic circulation** (via the inferior epigastric vein).
- Increased blood flow through these anastomoses, particularly the **paraumbilical veins** that drain into the epigastric veins, causes the characteristic **caput medusae** observed as dilated veins around the umbilicus, due to the shunting of portal blood away from the obstructed liver.
*Hepatic vein*
- Obstruction or increased flow in the **hepatic veins** (e.g., Budd-Chiari syndrome) would typically cause acute liver congestion and ascites but would not cause prominent **caput medusae** from shunting through periumbilical veins.
- While it contributes to hepatic outflow, it is not directly involved in the formation of **caput medusae** through portosystemic shunting at the umbilical level.
*Superior rectal vein*
- Increased blood flow in the **superior rectal vein** would lead to **hemorrhoids** as part of portosystemic anastomoses at the rectoanal junction (portal system via inferior mesenteric vein to systemic via middle and inferior rectal veins).
- This does not explain the **periumbilical dilated veins** or **caput medusae** seen in the patient.
*Left gastric vein*
- The **left gastric vein** is a significant site of portosystemic anastomosis, connecting to the **azygos system**, and increased flow causes **esophageal varices**.
- While a crucial site of shunting in portal hypertension, it does not explain the **dilated periumbilical veins** observed.
*Superior mesenteric vein*
- The **superior mesenteric vein** is a major tributary of the **portal vein**; increased flow within it would lead to increased portal pressure but is not itself a site of portosystemic anastomosis that would result in **caput medusae**.
- Pathologies directly affecting the superior mesenteric vein (e.g., thrombosis) would lead to mesenteric ischemia or bowel congestion, rather than the specific periumbilical venous dilation.
Digestive system overview US Medical PG Question 7: A 55-year-old woman presents with acute onset abdominal pain radiating to her back, nausea, and vomiting. CT scan suggests a diagnosis of acute pancreatitis. The pathogenesis of acute pancreatitis relates to inappropriate activation of trypsinogen to trypsin. Which of the following activates trypsin in normal digestion?
- A. Secretin
- B. Lipase
- C. Cholecystokinin
- D. Enterokinase (Correct Answer)
- E. Amylase
Digestive system overview Explanation: ***Enterokinase***
- **Enterokinase** (also known as enteropeptidase) is a brush border enzyme of the duodenum that specifically cleaves and activates pancreatic **trypsinogen** into its active form, **trypsin**.
- Once activated, **trypsin** then activates other pancreatic proteases (e.g., chymotrypsinogen, procarboxypeptidases, proelastase) within the intestinal lumen.
*Secretin*
- **Secretin** is a hormone released by S cells in the duodenum in response to acidic chyme and acts on the pancreas to stimulate the secretion of **bicarbonate-rich fluid**, which neutralizes gastric acid.
- It does not directly activate digestive enzymes like trypsinogen.
*Lipase*
- **Lipase** is a pancreatic enzyme secreted in its active form that breaks down **dietary fats** (triglycerides) into fatty acids and monoglycerides.
- It plays no role in the activation of trypsinogen.
*Cholecystokinin*
- **Cholecystokinin (CCK)** is a hormone released by I cells in the duodenum in response to fats and proteins, stimulating the contraction of the **gallbladder** and the secretion of **pancreatic enzymes**.
- While it promotes the release of pancreatic enzymes, it does not directly activate trypsinogen.
*Amylase*
- **Amylase** is a pancreatic enzyme secreted in its active form that breaks down **complex carbohydrates** (starches) into simpler sugars (disaccharides and oligosaccharides).
- It is not involved in the activation cascade of pancreatic proteases.
Digestive system overview US Medical PG Question 8: A 54-year-old man presents to his primary care physician with a 2-month-history of diarrhea. He says that he feels the urge to defecate 3-4 times per day and that his stools have changed in character since the diarrhea began. Specifically, they now float, stick to the side of the toilet bowl, and smell extremely foul. His past medical history is significant for several episodes of acute pancreatitis secondary to excessive alcohol consumption. His symptoms are found to be due to a deficiency in an enzyme. Which of the following enzymes is most likely deficient in this patient?
- A. Enterokinase
- B. Amylase
- C. Colipase
- D. Lipase (Correct Answer)
- E. Chymotrypsin
Digestive system overview Explanation: ***Lipase***
- The patient's history of **recurrent pancreatitis** likely led to **exocrine pancreatic insufficiency**, reducing the production of digestive enzymes, particularly **lipase**.
- **Steatorrhea** (foul-smelling, floating, sticky stools) is a classic symptom of **fat malabsorption**, which occurs due to insufficient lipase for triglyceride digestion.
*Enterokinase*
- **Enterokinase** is an enzyme produced in the **duodenum** that activates trypsinogen to trypsin, which then activates other pancreatic proteases.
- A deficiency would primarily cause **protein malabsorption**, not the pronounced fat malabsorption (steatorrhea) seen in this patient.
*Amylase*
- **Amylase** is responsible for **carbohydrate digestion**.
- While chronic pancreatitis can lead to amylase deficiency, the primary symptom of this patient's diarrhea, steatorrhea, points more directly to **fat malabsorption** rather than carbohydrate malabsorption.
*Colipase*
- **Colipase** is a co-enzyme that helps **lipase** bind to the fat-water interface to digest triglycerides.
- While essential for fat digestion, lipase itself is the primary enzyme responsible, and a direct deficiency in colipase alone is less commonly implicated as the sole cause of severe steatorrhea than a general pancreatic enzyme insufficiency affecting lipase production.
*Chymotrypsin*
- **Chymotrypsin** is a **protease** primarily involved in **protein digestion**.
- A deficiency would lead to **protein malabsorption**, which typically presents with symptoms like muscle wasting and edema, rather than the prominent steatorrhea described.
Digestive system overview US Medical PG Question 9: A 45-year-old male is brought to the emergency department by emergency medical services after sustaining a gunshot wound to the abdomen. He is unresponsive. His temperature is 99.0°F (37.2°C), blood pressure is 95/58 mmHg, pulse is 115/min, and respirations are 20/min. Physical examination reveals an entry wound in the left abdominal quadrant just inferior to the left lateral costal border. Abdominal CT shows the bullet trajectory through the left abdominal cavity. Which of the following structures has the bullet most likely penetrated?
- A. Transverse colon
- B. Ascending colon
- C. Descending colon (Correct Answer)
- D. Sigmoid colon
- E. Superior duodenum
Digestive system overview Explanation: ***Descending colon***
- The **descending colon** is located in the left abdominal cavity, specifically in the left upper quadrant and extending into the left lower quadrant, making it highly susceptible to injury from a gunshot wound in the **left abdominal quadrant** just inferior to the left lateral costal border.
- Its position aligns directly with the described entry point and bullet trajectory.
*Transverse colon*
- The **transverse colon** lies more centrally in the upper abdomen, spanning from the right to the left upper quadrants.
- While possible to be hit by a left-sided entry wound, the trajectory described as "inferior to the left lateral costal border" makes the descending colon a more direct and likely target.
*Ascending colon*
- The **ascending colon** is located in the **right abdominal cavity**, specifically in the right upper and lower quadrants.
- A wound inferior to the left lateral costal border would be on the opposite side of the abdomen and thus unlikely to penetrate the ascending colon.
*Sigmoid colon*
- The **sigmoid colon** is located more inferiorly in the **left lower quadrant** and pelvis.
- While on the left side, the entry wound described as "inferior to the left lateral costal border" is generally higher than the typical location of the sigmoid colon.
*Superior duodenum*
- The **superior duodenum** is located in the **right upper quadrant** of the abdomen, anterior to the head of the pancreas.
- Its position on the right side makes it highly unlikely to be penetrated by a gunshot wound to the left abdominal quadrant.
Digestive system overview US Medical PG Question 10: A 62-year-old female presents to her primary care physician complaining of bloody stool. She reports several episodes of bloody stools over the past two months as well as a feeling of a mass near her anus. She has one to two non-painful bowel movements per day. She has a history of alcohol abuse and hypertension. Anoscopy reveals engorged vessels. Which of the following vessels most likely drains blood from the affected region?
- A. Internal pudendal vein
- B. Left colic vein
- C. Inferior rectal vein (Correct Answer)
- D. Middle rectal vein
- E. Superior rectal vein
Digestive system overview Explanation: ***Inferior rectal vein***
- The patient's symptoms (bloody stool, anal mass, engorged vessels on anoscopy) are classic for **external hemorrhoids**.
- **External hemorrhoids** are distended veins located **below the dentate line** in the anal canal, which are drained by the **inferior rectal veins**.
- The inferior rectal veins drain into the **internal pudendal vein**, then to the **internal iliac vein** (part of the **systemic venous circulation**).
*Internal pudendal vein*
- The **internal pudendal vein** drains structures in the perineum and external genitalia, but it is not the **primary/direct drainage** for hemorrhoids.
- It receives blood from the inferior rectal veins but is one step removed from the hemorrhoidal plexus itself.
*Left colic vein*
- The **left colic vein** typically drains the distal transverse colon and descending colon.
- It is part of the **inferior mesenteric venous system** and is anatomically distant from the anorectal region, not involved in draining hemorrhoids.
*Middle rectal vein*
- The **middle rectal vein** drains the middle part of the rectum and connects both portal and systemic circulations.
- It drains the **muscularis layer** of the rectum but is not the primary drainage for the external hemorrhoidal plexus below the dentate line.
*Superior rectal vein*
- The **superior rectal vein** drains the upper part of the rectum and anal canal **above the dentate line**.
- Distention of these veins leads to **internal hemorrhoids**, which are typically painless unless prolapsed or thrombosed.
- It drains into the **inferior mesenteric vein** (part of the **portal venous circulation**).
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