A 55-year-old man is brought to the emergency department by ambulance from a long term nursing facility complaining of severe shortness of breath. He suffers from amyotrophic lateral sclerosis and lives at the nursing home full time. He has had the disease for 2 years and it has been getting harder to breath over the last month. He is placed on a rebreather mask and responds to questions while gasping for air. He denies cough or any other upper respiratory symptoms and denies a history of cardiovascular or respiratory disease. The blood pressure is 132/70 mm Hg, the heart rate is 98/min, the respiratory rate is 40/min, and the temperature is 37.6°C (99.7°F). During the physical exam, he begs to be placed in a sitting position. After he is repositioned his breathing improves a great deal. On physical examination, his respiratory movements are shallow and labored with paradoxical inward movement of his abdomen during inspiration. Auscultation of the chest reveals a lack of breath sounds in the lower lung bilaterally. At present, which of the following muscles is most important for inspiration in the patient?
Q22
A 56-year-old woman is referred to a plastic surgeon for breast reconstruction approximately 18 months after undergoing right modified radical mastectomy for breast cancer. Physical exam demonstrates atrophy of the lower portion of the pectoralis major muscle. Damage to which of the following nerves during mastectomy is the most likely cause of her atrophy?
Q23
A 55-year-old man visits the clinic with his wife. He has had difficulty swallowing solid foods for the past 2 months. His wife adds that his voice is getting hoarse but they thought it was due to his recent flu. His medical history is significant for type 2 diabetes mellitus for which he is on metformin. He suffered from many childhood diseases due to lack of medical care and poverty. His blood pressure is 125/87 mm Hg, pulse 95/min, respiratory rate 14/min, and temperature 37.1°C (98.7°F). On examination, an opening snap is heard over the cardiac apex. An echocardiogram shows an enlarged cardiac chamber pressing into his esophagus. Changes in which of the following structures is most likely responsible for this patient’s symptoms?
Q24
A 70-year-old woman presents with substernal chest pain. She says that the symptoms began 2 hours ago and have not improved. She describes the pain as severe, episodic, and worse with exertion. She reports that she has had multiple similar episodes that have worsened and increased in frequency over the previous 4 months. Past medical history is significant for diabetes and hypertension, both managed medically. The vital signs include temperature 37.0°C (98.6°F), blood pressure 150/100 mm Hg, pulse 80/min, and respiratory rate 15/min. Her serum total cholesterol is 280 mg/dL and high-density lipoprotein (HDL) is 30 mg/dL. The electrocardiogram (ECG) shows ST-segment depression on multiple chest leads. Coronary angiography reveals 75% narrowing of her left main coronary artery. In which of the following anatomical locations is a mural thrombus most likely to form in this patient?
Q25
A 16-year-old boy presents to the emergency department with abdominal pain and tenderness. The pain began approximately 2 days ago in the area just above his umbilicus and was crampy in nature. Earlier this morning, the pain moved laterally to his right lower abdomen. At that time, the pain in the right lower quadrant became severe and constant and woke him up from sleep. He decided to come to the hospital. The patient is nauseous and had a low-grade fever of 37.8°C (100.1°F). Other vitals are normal. Upon physical examination, the patient has rebound tenderness but a negative psoas sign while the remaining areas of his abdomen are non-tender. His rectal exam is normal. Laboratory tests show a white cell count of 15,000/mm3. Urinalysis and other laboratory findings were negative. What conclusion can be drawn about the nerves involved in the transmission of this patient’s pain during the physical exam?
Q26
A 65-year-old man presents to his primary care provider after noticing increasing fatigue over the past several weeks. He now becomes short of breath after going up 1 flight of stairs. He was previously healthy and has not seen a doctor for several years. He denies any fever or changes to his bowel movements. On exam, his temperature is 98.8°F (37.1°C), blood pressure is 116/76 mmHg, pulse is 74/min, and respirations are 14/min. On basic labs, his hemoglobin is found to be 9.6 g/dL and MCV is 75 fL. Fecal blood testing is positive for occult blood. Imaging is notable for a mass in the cecum that is partially obstructing the lumen, as well as several small lesions in the liver. Which of the following structures is most at risk for involvement in this patient’s disease?
Q27
A 55-year-old man comes to the physician because of a 3-week history of intermittent burning epigastric pain. His pain improves with antacid use and eating but returns approximately 2 hours following meals. He has a history of chronic osteoarthritis and takes ibuprofen daily. Upper endoscopy shows a deep ulcer located on the posterior wall of the duodenal bulb. This ulcer is most likely to erode into which of the following structures?
Q28
A 60-year-old man comes to the clinic complaining of a persistent cough for the last few months. His cough started gradually about a year ago, and it became more severe and persistent despite all his attempts to alleviate it. During the past year, he also noticed some weight loss and a decrease in his appetite. He also complains of progressive shortness of breath. He has a 40-pack-year smoking history but is a nonalcoholic. Physical examination findings are within normal limits. His chest X-ray shows a mass in the right lung. A chest CT shows a 5 cm mass with irregular borders near the lung hilum. A CT guided biopsy is planned. During the procedure, just after insertion of the needle, the patient starts to feel pain in his right shoulder. Which of the following nerves is responsible for his shoulder pain?
Q29
A 50-year-old man presents to the emergency department complaining of chest pain and drooling that started immediately after eating a steak. His past medical history is significant for lye ingestion 5 years ago during a suicidal attempt. He also suffers from hypertension and diabetes mellitus, type 2. He takes fluoxetine, lisinopril, and metformin every day. He also regularly sees a counselor to cope with his previous suicide attempt. Both of his parents are still alive and in good health. His heart rate is 96/min, temperature is 36.7°C (98.1°F).On physical examination, the patient can talk normally and breathes without effort. He is drooling. The chest pain is vague and constant. A chest X-ray shows no subcutaneous emphysema. An endoscopy confirms the presence of a retained bolus of meat 24 cm beyond the incisors where a stricture is identified. The bolus is removed and the stricture is dilated. Which of the following anatomic spaces contains the stricture?
Q30
A 67-year-old man presents to the office complaining of abdominal pain. He was started on a trial of proton pump inhibitors 5 weeks ago but the pain has not improved. He describes the pain as dull, cramping, and worse during meals. Medical history is unremarkable. Physical examination is normal except for tenderness in the epigastric region. Endoscopy reveals an eroding gastric ulcer in the proximal part of the greater curvature of the stomach overlying a large pulsing artery. Which of the following arteries is most likely visible?
Thorax/Abdomen US Medical PG Practice Questions and MCQs
Question 21: A 55-year-old man is brought to the emergency department by ambulance from a long term nursing facility complaining of severe shortness of breath. He suffers from amyotrophic lateral sclerosis and lives at the nursing home full time. He has had the disease for 2 years and it has been getting harder to breath over the last month. He is placed on a rebreather mask and responds to questions while gasping for air. He denies cough or any other upper respiratory symptoms and denies a history of cardiovascular or respiratory disease. The blood pressure is 132/70 mm Hg, the heart rate is 98/min, the respiratory rate is 40/min, and the temperature is 37.6°C (99.7°F). During the physical exam, he begs to be placed in a sitting position. After he is repositioned his breathing improves a great deal. On physical examination, his respiratory movements are shallow and labored with paradoxical inward movement of his abdomen during inspiration. Auscultation of the chest reveals a lack of breath sounds in the lower lung bilaterally. At present, which of the following muscles is most important for inspiration in the patient?
A. Muscles of anterior abdominal wall
B. Sternocleidomastoid muscles (Correct Answer)
C. Internal intercostal muscles
D. Trapezius muscle
E. External intercostal muscles
Explanation: ***Sternocleidomastoid muscles***
- In advanced **amyotrophic lateral sclerosis (ALS)**, progressive motor neuron degeneration affects both the diaphragm and intercostal muscles
- The **paradoxical inward movement of the abdomen** during inspiration indicates severe diaphragmatic weakness or paralysis
- The **shallow respiratory movements** and **severe respiratory distress** (respiratory rate 40/min) suggest that both primary inspiratory muscle groups (diaphragm and external intercostals) are significantly compromised
- At this stage, **accessory muscles of inspiration**, particularly the **sternocleidomastoid muscles**, become critically important for maintaining ventilation by elevating the sternum and upper ribs
- The dramatic improvement when sitting upright (orthopnea relief) supports accessory muscle recruitment, as this position optimizes sternocleidomastoid mechanical advantage
- **Clinical pearl:** In neuromuscular respiratory failure, neck muscle recruitment (visible SCM contraction) is a key sign of impending respiratory failure requiring ventilatory support
*External intercostal muscles*
- The **external intercostal muscles** are normally primary muscles of inspiration that elevate the ribs
- However, in advanced ALS with **2 years of progressive disease** and worsening dyspnea over the past month, these muscles would also be significantly weakened by the neurodegenerative process
- The **lack of breath sounds in the lower lungs bilaterally** suggests poor chest wall expansion, indicating compromised intercostal function
- While they continue to contribute, they are insufficient to maintain adequate ventilation alone at this stage of disease
*Internal intercostal muscles*
- The **internal intercostal muscles** function primarily in **forced expiration** by depressing the ribs
- They do not play a significant role in inspiration
*Muscles of anterior abdominal wall*
- The **anterior abdominal wall muscles** (rectus abdominis, external/internal obliques, transversus abdominis) are **expiratory muscles** used in forced expiration and coughing
- The **paradoxical inward movement** of the abdomen during inspiration is a passive phenomenon resulting from diaphragmatic weakness—the negative intrathoracic pressure pulls the weakened diaphragm upward, which in turn draws the abdominal wall inward
- These muscles are not contributing to inspiration in this patient
*Trapezius muscle*
- The **trapezius** primarily functions in scapular movement and neck stabilization
- While it provides some mechanical stability for the shoulder girdle during accessory muscle breathing, it is not directly involved in rib cage elevation
- It plays a minor supportive role compared to the sternocleidomastoid in respiratory distress
Question 22: A 56-year-old woman is referred to a plastic surgeon for breast reconstruction approximately 18 months after undergoing right modified radical mastectomy for breast cancer. Physical exam demonstrates atrophy of the lower portion of the pectoralis major muscle. Damage to which of the following nerves during mastectomy is the most likely cause of her atrophy?
A. Long thoracic
B. Intercostobrachial
C. Lateral intercostal
D. Lateral pectoral
E. Medial pectoral (Correct Answer)
Explanation: ***Medial pectoral***
- The **medial pectoral nerve** innervates both the pectoralis major and pectoralis minor muscles.
- Damage to this nerve during mastectomy can lead to **atrophy of the lower lateral portion of the pectoralis major**, as this area relies heavily on its innervation.
*Long thoracic*
- The **long thoracic nerve** innervates the **serratus anterior muscle**.
- Damage to this nerve would cause **scapular winging**, not atrophy of the pectoralis major.
*Intercostobrachial*
- The **intercostobrachial nerve** is primarily a **sensory nerve** supplying the skin of the upper medial arm and axilla.
- Damage to this nerve would result in **sensory changes** (numbness, pain) in that area, not muscle atrophy.
*Lateral intercostal*
- The **lateral intercostal nerves** are primarily sensory and motor to the intercostal muscles and overlying skin.
- Damage would typically cause **pain or numbness** along the chest wall or trunk, and possibly weakness of intercostal muscles, not pectoralis major atrophy.
*Lateral pectoral*
- The **lateral pectoral nerve** primarily innervates the **clavicular head** and **upper sternocostal portion** of the pectoralis major.
- Damage to this nerve would cause atrophy in the **upper and medial parts** of the pectoralis major, not specifically the lower lateral portion.
Question 23: A 55-year-old man visits the clinic with his wife. He has had difficulty swallowing solid foods for the past 2 months. His wife adds that his voice is getting hoarse but they thought it was due to his recent flu. His medical history is significant for type 2 diabetes mellitus for which he is on metformin. He suffered from many childhood diseases due to lack of medical care and poverty. His blood pressure is 125/87 mm Hg, pulse 95/min, respiratory rate 14/min, and temperature 37.1°C (98.7°F). On examination, an opening snap is heard over the cardiac apex. An echocardiogram shows an enlarged cardiac chamber pressing into his esophagus. Changes in which of the following structures is most likely responsible for this patient’s symptoms?
A. Patent ductus arteriosus
B. Right ventricle
C. Left ventricle
D. Left atrium (Correct Answer)
E. Right atrium
Explanation: ***Left atrium***
- The patient's symptoms of **dysphagia (difficulty swallowing)** and **hoarseness** suggest compression of anatomical structures by an enlarged cardiac chamber, which the echocardiogram confirms.
- An enlarged **left atrium**, typically due to **mitral stenosis**, can compress the esophagus (leading to dysphagia) and the **recurrent laryngeal nerve** (leading to hoarseness, known as Ortner's syndrome). The **opening snap** at the apex is also highly characteristic of mitral stenosis.
*Patent ductus arteriosus*
- A **patent ductus arteriosus (PDA)** is a congenital heart defect that typically causes a **continuous murmur** and may lead to pulmonary hypertension or heart failure, but not direct compression of the esophagus or recurrent laryngeal nerve.
- The symptoms of PDA are usually present earlier in life, though uncorrected large PDAs can cause symptoms in adulthood, they do not cause dysphagia or hoarseness through direct esophageal compression.
*Right ventricle*
- An enlarged **right ventricle** usually causes symptoms related to right heart failure like **peripheral edema** or **dyspnea** due to pulmonary hypertension.
- It is not anatomically positioned to compress the esophagus or recurrent laryngeal nerve in a way that would cause dysphagia or hoarseness.
*Left ventricle*
- An enlarged **left ventricle** (e.g., due to hypertension or aortic stenosis) primarily causes symptoms like **dyspnea on exertion** or **angina**.
- While a severely dilated left ventricle can displace other structures, it does not typically cause direct esophageal compression leading to dysphagia or recurrent laryngeal nerve compression leading to hoarseness.
*Right atrium*
- An enlarged **right atrium** might be seen in conditions like tricuspid regurgitation or right heart failure but can manifest as **edema** or **jugular venous distention**.
- It is not anatomically positioned to cause dysphagia or hoarseness from esophageal or recurrent laryngeal nerve compression.
Question 24: A 70-year-old woman presents with substernal chest pain. She says that the symptoms began 2 hours ago and have not improved. She describes the pain as severe, episodic, and worse with exertion. She reports that she has had multiple similar episodes that have worsened and increased in frequency over the previous 4 months. Past medical history is significant for diabetes and hypertension, both managed medically. The vital signs include temperature 37.0°C (98.6°F), blood pressure 150/100 mm Hg, pulse 80/min, and respiratory rate 15/min. Her serum total cholesterol is 280 mg/dL and high-density lipoprotein (HDL) is 30 mg/dL. The electrocardiogram (ECG) shows ST-segment depression on multiple chest leads. Coronary angiography reveals 75% narrowing of her left main coronary artery. In which of the following anatomical locations is a mural thrombus most likely to form in this patient?
A. Left ventricle (Correct Answer)
B. Left atrium
C. Aorta
D. Right atrium
E. Right ventricle
Explanation: ***Left ventricle***
- The patient presents with symptoms and ECG findings consistent with **unstable angina** or **non-ST elevation myocardial infarction (NSTEMI)**, indicating myocardial ischemia.
- With **75% left main coronary artery stenosis**, there is high risk of progression to **transmural myocardial infarction (STEMI)**, particularly affecting the anterior wall and septum.
- Mural thrombi in the left ventricle typically form **3-7 days post-infarction** in areas of **dyskinetic or akinetic myocardium** due to blood stasis, endocardial injury, and hypercoagulability (Virchow's triad).
- Left main disease affecting such a large territory makes the **left ventricle the most likely site** for mural thrombus formation.
*Left atrium*
- Mural thrombi in the left atrium are most commonly associated with **atrial fibrillation** due to blood stasis in the **left atrial appendage**.
- This patient's symptoms are characteristic of coronary artery disease affecting the left ventricle, not an atrial arrhythmia.
*Aorta*
- While thrombi can form in the aorta (e.g., in the setting of **atherosclerosis** or **aneurysms**), they are typically mural thrombi associated with specific vascular pathologies.
- The symptoms of **chest pain, ST depression**, and **coronary artery narrowing** point toward a myocardial event, making the left ventricle the most likely site for mural thrombus in this clinical context.
*Right atrium*
- Thrombi in the right atrium are usually associated with conditions leading to **venous stasis, such as deep vein thrombosis**, **central venous catheters**, or **right-sided heart failure**.
- The patient's presentation with exertional chest pain and left main coronary artery narrowing is unrelated to right atrial thrombosis.
*Right ventricle*
- The right ventricle is **much less commonly** affected by ischemic events leading to mural thrombi compared to the left ventricle, due to its **lower oxygen demand** and **different blood supply** (right coronary artery).
- While right ventricular infarction can occur (usually with inferior MI), the **left main coronary artery** supplies the left ventricle, making it the primary concern for mural thrombus formation in this patient.
Question 25: A 16-year-old boy presents to the emergency department with abdominal pain and tenderness. The pain began approximately 2 days ago in the area just above his umbilicus and was crampy in nature. Earlier this morning, the pain moved laterally to his right lower abdomen. At that time, the pain in the right lower quadrant became severe and constant and woke him up from sleep. He decided to come to the hospital. The patient is nauseous and had a low-grade fever of 37.8°C (100.1°F). Other vitals are normal. Upon physical examination, the patient has rebound tenderness but a negative psoas sign while the remaining areas of his abdomen are non-tender. His rectal exam is normal. Laboratory tests show a white cell count of 15,000/mm3. Urinalysis and other laboratory findings were negative. What conclusion can be drawn about the nerves involved in the transmission of this patient’s pain during the physical exam?
A. His pain is transmitted bilaterally by somatic afferent nerve fibers of the abdomen.
B. His pain is transmitted by somatic afferent nerve fibers located in the right flank.
C. His pain is transmitted by the pelvic nerves.
D. His pain is transmitted by right somatic nerve fibers. (Correct Answer)
E. His pain is mainly transmitted by the right splanchnic nerve.
Explanation: ***His pain is transmitted by right somatic nerve fibers.***
- The **migration of pain from the periumbilical region to the right lower quadrant** and becoming **severe and constant** indicates parietal peritoneal irritation.
- **Somatic nerve fibers** innervate the parietal peritoneum and are responsible for transmitting **sharp, localized pain** typically associated with appendicitis in the right lower quadrant.
*His pain is transmitted bilaterally by somatic afferent nerve fibers of the abdomen.*
- While **visceral pain** from the initial appendiceal inflammation can be perceived bilaterally in the periumbilical region due to **bilateral innervation of visceral organs**, the **localized right lower quadrant pain** signifies involvement of **unilaterally innervated parietal peritoneum**.
- The physical exam findings of **rebound tenderness** strongly suggest **localized peritoneal inflammation**, which is transmitted by **unilateral somatic nerves** at the site of inflammation, not bilaterally across the abdomen.
*His pain is transmitted by somatic afferent nerve fibers located in the right flank.*
- The **right flank** refers to the lateral aspect of the abdomen, while the pain is specifically localized to the **right lower quadrant**.
- Although somatic nerves are involved, stating "right flank" is **too broad and imprecise** given the very specific localization of the pain to the right lower quadrant where the inflamed appendix is typically situated.
*His pain is transmitted by the pelvic nerves.*
- **Pelvic nerves** primarily carry parasympathetic fibers and visceral afferent fibers from pelvic organs, not the somatic pain from the parietal peritoneum in the right lower quadrant.
- Pain from **pelvic organs** or **pelvic peritoneum** would be transmitted via these nerves, but the localized pain here is distinctly higher than typical pelvic organ pain.
*His pain is mainly transmitted by the right splanchnic nerve.*
- **Splanchnic nerves** primarily carry **visceral afferent fibers** responsible for the dull, poorly localized, initial periumbilical pain of appendicitis.
- They do not transmit the **sharp, well-localized somatic pain** associated with parietal peritoneal irritation, which is characteristic of the pain migrating to the right lower quadrant.
Question 26: A 65-year-old man presents to his primary care provider after noticing increasing fatigue over the past several weeks. He now becomes short of breath after going up 1 flight of stairs. He was previously healthy and has not seen a doctor for several years. He denies any fever or changes to his bowel movements. On exam, his temperature is 98.8°F (37.1°C), blood pressure is 116/76 mmHg, pulse is 74/min, and respirations are 14/min. On basic labs, his hemoglobin is found to be 9.6 g/dL and MCV is 75 fL. Fecal blood testing is positive for occult blood. Imaging is notable for a mass in the cecum that is partially obstructing the lumen, as well as several small lesions in the liver. Which of the following structures is most at risk for involvement in this patient’s disease?
A. Right gonadal vein
B. Inferior mesenteric vein
C. Inferior rectal vein
D. Right renal vein
E. Superior mesenteric vein (Correct Answer)
Explanation: ***Superior mesenteric vein***
- The patient has a **cecal mass** and **liver lesions** consistent with **colon cancer** with **liver metastasis**. Cancer cells from the cecum drain predominantly into the **superior mesenteric vein**, before traveling to the liver via the **portal vein system**.
- The **superior mesenteric vein (SMV)** drains blood from the cecum, ascending colon, and transverse colon. Metastatic cells from these regions would use this route to reach the liver.
*Right gonadal vein*
- The right gonadal vein drains into the **inferior vena cava (IVC)**, bypassing the portal system.
- Metastasis to the liver would be less direct via this route, and the **cecum** does not primarily drain into the gonadal veins.
*Inferior mesenteric vein*
- The **inferior mesenteric vein (IMV)** drains the descending colon, sigmoid colon, and rectum.
- While it eventually joins the **splenic vein** and then the **portal vein**, it is not the primary drainage for the cecum.
*Inferior rectal vein*
- The **inferior rectal vein** drains the lower rectum and anal canal, primarily into the **internal iliac veins** and then the **IVC**, bypassing the portal system.
- This route is not relevant for metastasis from a **cecal mass**.
*Right renal vein*
- The **right renal vein** drains blood from the right kidney into the **inferior vena cava (IVC)**.
- This vein is unrelated to the drainage of the gastrointestinal tract and would not be involved in metastasis from a **cecal mass**.
Question 27: A 55-year-old man comes to the physician because of a 3-week history of intermittent burning epigastric pain. His pain improves with antacid use and eating but returns approximately 2 hours following meals. He has a history of chronic osteoarthritis and takes ibuprofen daily. Upper endoscopy shows a deep ulcer located on the posterior wall of the duodenal bulb. This ulcer is most likely to erode into which of the following structures?
A. Splenic vein
B. Descending aorta
C. Pancreatic duct
D. Gastroduodenal artery (Correct Answer)
E. Transverse colon
Explanation: ***Gastroduodenal artery***
- A deep ulcer on the **posterior wall of the duodenal bulb** is anatomically very close to the **gastroduodenal artery**.
- Erosion into this artery can lead to **life-threatening upper gastrointestinal bleeding**, a severe complication of peptic ulcer disease.
*Splenic vein*
- The **splenic vein** is located more posteriorly and superiorly, primarily in relation to the pancreas and spleen, making it less likely to be eroded by a duodenal bulb ulcer.
- While erosion into major vessels can occur, the gastroduodenal artery is in a much more direct and immediate proximity to the posterior duodenal bulb.
*Descending aorta*
- The **descending aorta** is a retroperitoneal structure located much more posteriorly and medially, far from the duodenal bulb.
- Erosion into the aorta is an extremely rare and catastrophic event, not typically associated with duodenal ulcers.
*Pancreatic duct*
- The **pancreatic duct** (Wirsung's duct) is located within the pancreas, which lies posterior to the duodenum. While a *deep* ulcer could hypothetically penetrate the pancreas, the primary structure at risk for hemorrhage from a posterior duodenal bulb ulcer is the gastroduodenal artery.
- Erosion into the pancreatic duct would likely cause **pancreatitis** or **fistula formation**, rather than acute hemorrhage.
*Transverse colon*
- The **transverse colon** is located inferior to the duodenum, separated by the greater omentum.
- Ulcers would typically erode anteriorly or directly posteriorly, not inferiorly into the transverse colon, which would involve fistula formation rather than arterial erosion.
Question 28: A 60-year-old man comes to the clinic complaining of a persistent cough for the last few months. His cough started gradually about a year ago, and it became more severe and persistent despite all his attempts to alleviate it. During the past year, he also noticed some weight loss and a decrease in his appetite. He also complains of progressive shortness of breath. He has a 40-pack-year smoking history but is a nonalcoholic. Physical examination findings are within normal limits. His chest X-ray shows a mass in the right lung. A chest CT shows a 5 cm mass with irregular borders near the lung hilum. A CT guided biopsy is planned. During the procedure, just after insertion of the needle, the patient starts to feel pain in his right shoulder. Which of the following nerves is responsible for his shoulder pain?
A. Thoracic spinal nerves
B. Phrenic nerve (Correct Answer)
C. Vagus nerve
D. Pulmonary plexus
E. Intercostal nerves
Explanation: **Phrenic nerve**
- The **phrenic nerve** innervates the diaphragm and also carries sensory fibers from the **mediastinal and diaphragmatic pleura**, as well as the **pericardium**.
- Irritation of the phrenic nerve, due to its **C3-C5 cervical origin**, can cause **referred pain to the ipsilateral shoulder** or neck.
*Thoracic spinal nerves*
- These nerves primarily serve the **intercostal muscles** and skin of the chest wall.
- While they can transmit pain from the chest wall, they are not typically associated with **referred shoulder pain** from intrathoracic structures.
*Vagus nerve*
- The **vagus nerve** provides parasympathetic innervation to many thoracic and abdominal organs and carries visceral afferents.
- It plays a role in regulating lung function but does not transmit sensory information that would be perceived as **shoulder pain** from diaphragmatic irritation.
*Pulmonary plexus*
- The **pulmonary plexus** is formed by branches of the vagus and sympathetic nerves, primarily involved in regulating **bronchial and vascular tone** in the lungs.
- It does not transmit sensory input that would cause referred pain to the shoulder.
*Intercostal nerves*
- These nerves run along the ribs and innervate the **intercostal muscles** and skin of the **thoracic wall**.
- Pain from these nerves would typically be felt along the **rib cage** or chest wall, not as referred shoulder pain.
Question 29: A 50-year-old man presents to the emergency department complaining of chest pain and drooling that started immediately after eating a steak. His past medical history is significant for lye ingestion 5 years ago during a suicidal attempt. He also suffers from hypertension and diabetes mellitus, type 2. He takes fluoxetine, lisinopril, and metformin every day. He also regularly sees a counselor to cope with his previous suicide attempt. Both of his parents are still alive and in good health. His heart rate is 96/min, temperature is 36.7°C (98.1°F).On physical examination, the patient can talk normally and breathes without effort. He is drooling. The chest pain is vague and constant. A chest X-ray shows no subcutaneous emphysema. An endoscopy confirms the presence of a retained bolus of meat 24 cm beyond the incisors where a stricture is identified. The bolus is removed and the stricture is dilated. Which of the following anatomic spaces contains the stricture?
A. The superior mediastinum
B. The epigastrium
C. The posterior mediastinum (Correct Answer)
D. The anterior mediastinum
E. The diaphragm
Explanation: ***The posterior mediastinum***
- The posterior mediastinum contains the **esophagus**, descending aorta, thoracic duct, azygos and hemiazygos veins, and lymph nodes. Given the esophageal stricture, this is the most likely location.
- An esophageal obstruction at **24 cm from the incisors** typically corresponds to the mid-to-distal esophagus, which is located in the posterior mediastinum.
*The superior mediastinum*
- The superior mediastinum extends from the **thoracic inlet** to the level of the sternal angle (T4/T5 vertebrae).
- It contains the **trachea**, great vessels, thymus, and upper esophagus but an obstruction at 24 cm is usually below this region.
*The epigastrium*
- The epigastrium is an **abdominal region** of the upper abdomen, inferior to the xiphoid process and superior to the umbilicus.
- It contains structures like the stomach and pancreas, but not the **thoracic esophagus**.
*The anterior mediastinum*
- The anterior mediastinum contains the **thymus gland**, lymph nodes, and internal mammary vessels.
- The **esophagus is not located** in the anterior mediastinum.
*The diaphragm*
- The diaphragm is a **musculofibrous septum** that separates the thoracic and abdominal cavities.
- While the esophagus passes through an opening in the diaphragm (the **esophageal hiatus**), the stricture itself is within the esophageal tube, not the diaphragm itself, and 24 cm from the incisors is proximal to the hiatus.
Question 30: A 67-year-old man presents to the office complaining of abdominal pain. He was started on a trial of proton pump inhibitors 5 weeks ago but the pain has not improved. He describes the pain as dull, cramping, and worse during meals. Medical history is unremarkable. Physical examination is normal except for tenderness in the epigastric region. Endoscopy reveals an eroding gastric ulcer in the proximal part of the greater curvature of the stomach overlying a large pulsing artery. Which of the following arteries is most likely visible?
A. Left gastric artery
B. Cystic artery
C. Common hepatic artery
D. Left gastro-omental artery (Correct Answer)
E. Right gastro-omental artery
Explanation: ***Left gastro-omental artery***
- This artery runs along the **greater curvature** of the stomach, making it the most probable vessel to be seen pulsing in an ulcer located in the **proximal part of the greater curvature**.
- Its anatomical location directly underlies this area, making it vulnerable to erosion from a penetrating ulcer.
*Left gastric artery*
- The **left gastric artery** supplies the **lesser curvature** of the stomach, which is not the location described for the ulcer.
- An ulcer on the greater curvature would not typically expose this vessel.
*Cystic artery*
- The **cystic artery** supplies the **gallbladder** and is located much further away from the stomach, making it an unlikely vessel to be exposed by a gastric ulcer.
- It arises from the right hepatic artery and is not in close proximity to the stomach's curvature.
*Common hepatic artery*
- The **common hepatic artery** is located **posterior** to the stomach and more superiorly, supplying the liver, pylorus, and duodenum through its branches.
- It is not directly adjacent to the greater curvature of the stomach in a position that would be exposed by an ulcer there.
*Right gastro-omental artery*
- The **right gastro-omental artery** also runs along the **greater curvature**, but it is located more **distally** than the left gastro-omental artery.
- A pulsing artery in the **proximal part** of the greater curvature makes the left gastro-omental artery a more precise and likely answer.
