Surface projections of internal organs US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Surface projections of internal organs. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Surface projections of internal organs US Medical PG Question 1: A 12-year-old boy is brought to the emergency department late at night by his worried mother. She says he has not been feeling well since this morning after breakfast. He skipped both lunch and dinner. He complains of abdominal pain as he points towards his lower abdomen but says that the pain initially started at the center of his belly. His mother adds that he vomited once on the way to the hospital. His past medical history is noncontributory and his vaccinations are up to date. His temperature is 38.1°C (100.6°F), pulse is 98/min, respirations are 20/min, and blood pressure is 110/75 mm Hg. Physical examination reveals right lower quadrant tenderness. The patient is prepared for laparoscopic abdominal surgery. Which of the following structures is most likely to aid the surgeons in finding the source of this patient's pain and fever?
- A. McBurney's point
- B. Linea Semilunaris
- C. Transumbilical plane
- D. Arcuate line
- E. Teniae coli (Correct Answer)
Surface projections of internal organs Explanation: ***Teniae coli***
- The **teniae coli** are three distinct longitudinal bands of smooth muscle that run along the length of the large intestine, converging at the base of the appendix. They serve as reliable anatomical landmarks for locating the appendix during surgery.
- Given the patient's symptoms (periumbilical pain migrating to the right lower quadrant, fever, vomiting, and right lower quadrant tenderness), **acute appendicitis** is highly suspected, making the teniae coli crucial for surgical identification of the inflamed appendix.
*McBurney's point*
- **McBurney's point** is a clinical landmark on the abdominal wall, two-thirds of the way from the umbilicus to the right anterior superior iliac spine, that often corresponds to the base of the appendix. It is used to elicit tenderness during physical examination.
- While tenderness at McBurney's point is a strong indicator of appendicitis, it is a **surface landmark** for diagnosis and not an internal anatomical structure that aids the surgeon in _finding_ the appendix during a laparoscopic procedure.
*Linea Semilunaris*
- The **linea semilunaris** is the curved tendinous intersection found at the lateral border of the rectus abdominis muscle, extending from the costal margin to the pubic tubercle.
- It defines the lateral extent of the rectus sheath but has **no direct anatomical relationship** to the appendix or its surgical identification.
*Transumbilical plane*
- The **transumbilical plane** is an imaginary horizontal plane passing through the umbilicus. It is used in topographical anatomy for abdominal segmentation.
- It is a **surface and arbitrary anatomical plane** for regional description, not an internal structure that guides surgical access to or identification of the appendix.
*Arcuate line*
- The **arcuate line** is a crescent-shaped anatomical landmark located on the posterior wall of the rectus sheath, inferior to the umbilicus, marking the transition where the aponeuroses of the transverse abdominis and internal oblique muscles pass anterior to the rectus abdominis.
- This line is relevant to the integrity of the rectus sheath but is **anatomically distant from the appendix** and does not assist in its surgical localization.
Surface projections of internal organs US Medical PG Question 2: During a thoracotomy procedure, a surgeon needs to access the posterior mediastinum. Which of the following structures forms the anterior boundary of the posterior mediastinum?
- A. Descending thoracic aorta
- B. Pericardial sac (Correct Answer)
- C. Azygos vein
- D. Thoracic vertebrae
- E. Sternum
Surface projections of internal organs Explanation: ***Pericardial sac***
- The **pericardial sac** (and the diaphragm, inferiorly) forms the anterior boundary of the **posterior mediastinum** [1].
- This anatomical relationship is crucial for surgeons during thoracotomy to distinguish between the middle and posterior mediastinal compartments [1].
*Descending thoracic aorta*
- The **descending thoracic aorta** is a large vessel located *within* the posterior mediastinum itself, typically running along its left side [2].
- Therefore, it is a content of the posterior mediastinum, not a boundary.
*Azygos vein*
- The **azygos vein** is also a major structure *within* the posterior mediastinum, running along the right side of the vertebral column.
- It is a content, not a boundary, of this compartment.
*Thoracic vertebrae*
- The **thoracic vertebrae** form the *posterior* boundary of the posterior mediastinum [1].
- This anatomical landmark gives the posterior mediastinum its name and defines its dorsal limit.
Surface projections of internal organs US Medical PG Question 3: 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)
Surface projections of internal organs 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.
Surface projections of internal organs US Medical PG Question 4: A 14-year-old boy is brought to the emergency department because of acute left-sided chest pain and dyspnea following a motor vehicle accident. His pulse is 122/min and blood pressure is 85/45 mm Hg. Physical examination shows distended neck veins and tracheal displacement to the right side. The left chest is hyperresonant to percussion and there are decreased breath sounds. This patient would most benefit from needle insertion at which of the following anatomical sites?
- A. 5th left intercostal space along the midclavicular line
- B. 8th left intercostal space along the posterior axillary line
- C. 2nd left intercostal space along the midclavicular line (Correct Answer)
- D. Subxiphoid space in the left sternocostal margin
- E. 5th left intercostal space along the midaxillary line
Surface projections of internal organs Explanation: ***2nd left intercostal space along the midclavicular line***
- The patient's symptoms (chest pain, dyspnea, hypotension, distended neck veins, tracheal deviation, hyperresonance, and decreased breath sounds on the left) are classic signs of a **tension pneumothorax**.
- Immediate treatment for **tension pneumothorax** involves needle decompression at the **2nd intercostal space** in the midclavicular line to relieve pressure and restore hemodynamic stability.
*5th left intercostal space along the midclavicular line*
- This location is typically used for **chest tube insertion** in a more controlled setting, not for emergent needle decompression of a tension pneumothorax.
- While it's a safe location for pleural access, it is not the **first-line site** for immediate life-saving decompression.
*8th left intercostal space along the posterior axillary line*
- This site is too low and posterior for effective needle decompression of a tension pneumothorax, which requires rapid access to the **apex of the lung**.
- It is more commonly used for **thoracentesis** to drain fluid from the pleural cavity.
*Subxiphoid space in the left sternocostal margin*
- This location is primarily used for **pericardiocentesis** to drain fluid from the pericardial sac in cases of cardiac tamponade.
- It is not appropriate for addressing a **pneumothorax**, which involves air in the pleural space.
*5th left intercostal space along the midaxillary line*
- This site is a common alternative for **chest tube insertion** but is not the preferred or most immediate site for needle decompression of a tension pneumothorax.
- While it offers pleural access, the **2nd intercostal space** anteriorly is chosen for expediency and safety in an emergency.
Surface projections of internal organs US Medical PG Question 5: An 18-year-old man is brought to the emergency department 30 minutes after being stabbed in the chest during a fight. He has no other injuries. His pulse is 120/min, blood pressure is 90/60 mm Hg, and respirations are 22/min. Examination shows a 4-cm deep, straight stab wound in the 4th intercostal space 2 cm medial to the right midclavicular line. The knife most likely passed through which of the following structures?
- A. Serratus anterior muscle, pleura, inferior vena cava
- B. External oblique muscle, superior epigastric artery, azygos vein
- C. Pectoralis minor muscle, dome of the diaphragm, right lobe of the liver
- D. Intercostal muscles, internal thoracic artery, right heart
- E. Pectoral fascia, transversus thoracis muscle, right lung (Correct Answer)
Surface projections of internal organs Explanation: ***Pectoral fascia, transversus thoracis muscle, right lung***
* The stab wound is in the **4th intercostal space**, 2 cm medial to the right midclavicular line, placing it over the anterior chest wall. This trajectory would first penetrate the **pectoral fascia**.
* Deeper structures in this region include the **transversus thoracis muscle** and, given the depth, the **right lung** as it extends superiorly behind the anterior chest wall.
* *Serratus anterior muscle, pleura, inferior vena cava*
* The **serratus anterior muscle** is more laterally positioned, typically covering the side of the rib cage.
* The **inferior vena cava** is located more medially and posteriorly within the mediastinum, deep to the diaphragm, making it an unlikely target for an anterior 4th intercostal stab.
* *External oblique muscle, superior epigastric artery, azygos vein*
* The **external oblique muscle** is part of the abdominal wall and would not be penetrated in the 4th intercostal space.
* The **superior epigastric artery** is lower, typically extending into the abdominal wall, and the **azygos vein** is in the posterior mediastinum, not in the path of this superficial anterior stab wound.
* *Pectoralis minor muscle, dome of the diaphragm, right lobe of the liver*
* The **pectoralis minor muscle** is located deep to the pectoralis major, which would be penetrated. However, a stab at the 4th intercostal space would be too high to directly involve the **dome of the diaphragm** or the **right lobe of the liver**, which are typically below the 5th intercostal space, especially in forced expiration.
* *Intercostal muscles, internal thoracic artery, right heart*
* The **intercostal muscles** would certainly be traversed.
* However, the **internal thoracic artery** runs paramedially (about 1-2 cm from the sternum), and getting to the **right heart** would require a more medial and deeper trajectory, potentially causing immediate tamponade or severe hemorrhage.
Surface projections of internal organs US Medical PG Question 6: A 47-year-old man presents for a routine physical examination as part of an insurance medical assessment. He has no complaints and has no family history of cardiac disease or sudden cardiac death. His blood pressure is 120/80 mm Hg, temperature is 36.7°C (98.1°F), and pulse is 75/min and is regular. On physical examination, he appears slim and his cardiac apex beat is of normal character and non-displaced. On auscultation, he has a midsystolic click followed by a late-systolic high-pitched murmur over the cardiac apex. On standing, the click and murmur occur earlier in systole, and the murmur is of increased intensity. While squatting, the click and murmur occur later in systole, and the murmur is softer in intensity. Echocardiography of this patient will most likely show which of the following findings?
- A. Left atrial mass arising from the region of the septal fossa ovalis
- B. Doming of the mitral valve leaflets in diastole
- C. Prolapse of a mitral valve leaflet of ≥2 mm above the level of the annulus in systole (Correct Answer)
- D. Retrograde blood flow into the right atrium
- E. High pressure gradient across the aortic valve
Surface projections of internal organs Explanation: ***Prolapse of a mitral valve leaflet of ≥2 mm above the level of the annulus in systole***
- The clinical presentation with a **midsystolic click** followed by a **late-systolic high-pitched murmur over the cardiac apex** is characteristic of **mitral valve prolapse (MVP)**.
- The changes in the click and murmur timing and intensity with **standing (earlier, louder)** and **squatting (later, softer)** are classic findings, reflecting changes in left ventricular volume that affect the onset of valve prolapse.
*Left atrial mass arising from the region of the septal fossa ovalis*
- This description is highly suggestive of a **myxoma**, typically found in the left atrium, which can cause symptoms of **obstructive heart failure** or **embolism**.
- A myxoma would not typically present with the characteristic **midsystolic click** and **late-systolic murmur** that changes with position.
*Doming of the mitral valve leaflets in diastole*
- **Doming of the mitral valve leaflets in diastole** is characteristic of **mitral stenosis**, where the valve fails to open properly.
- Mitral stenosis would present with a **diastolic murmur**, not a midsystolic click and late-systolic murmur.
*Retrograde blood flow into the right atrium*
- **Retrograde blood flow into the right atrium** indicates **tricuspid regurgitation**, which would typically manifest as a **holosystolic murmur** best heard at the lower left sternal border, often with prominent jugular venous pulsations.
- This finding is inconsistent with the patient's auscultatory findings at the cardiac apex.
*High pressure gradient across the aortic valve*
- A **high pressure gradient across the aortic valve** signifies **aortic stenosis**, which is characterized by a **systolic ejection murmur** best heard at the right upper sternal border with radiation to the carotids.
- This condition would not produce a midsystolic click or a late-systolic murmur at the apex.
Surface projections of internal organs US Medical PG Question 7: A 23-year-old man is brought to the emergency department by a coworker for an injury sustained at work. He works in construction and accidentally shot himself in the chest with a nail gun. Physical examination shows a bleeding wound in the left hemithorax at the level of the 4th intercostal space at the midclavicular line. Which of the following structures is most likely injured in this patient?
- A. Right atrium of the heart
- B. Inferior vena cava
- C. Left upper lobe of the lung (Correct Answer)
- D. Left atrium of the heart
- E. Superior vena cava
Surface projections of internal organs Explanation: ***Left upper lobe of the lung***
- The **left upper lobe of the lung** extends to the 4th intercostal space at the midclavicular line, making it the most probable structure to be traversed by a penetrating injury at this location.
- The **pleural cavity** and lung tissue are superficially located in this region, making them highly susceptible to injury from a nail gun.
*Right atrium of the heart*
- The **right atrium** is located predominantly on the right side of the sternum, more centrally, and slightly to the right of the midclavicular line.
- An injury at the **left 4th intercostal space at the midclavicular line** would typically be too lateral and superior to directly injure the right atrium.
*Inferior vena cava*
- The **inferior vena cava (IVC)** enters the right atrium from below, primarily located within the abdomen and passing through the diaphragm at the level of T8.
- Its position is far too **inferior and posterior** relative to the 4th intercostal space to be directly injured by this wound.
*Left atrium of the heart*
- The **left atrium** is the most posterior chamber of the heart and is largely covered by the left ventricle.
- Although part of the heart is on the left, an injury at the **4th intercostal space, midclavicular line**, would likely impact the left ventricle or lung tissue before reaching the left atrium, which is located more posteriorly and medially.
*Superior vena cava*
- The **superior vena cava (SVC)** is located to the right of the midline, formed by the brachiocephalic veins behind the right first costal cartilage.
- Its position is too **medial and superior**, on the right side, to be directly injured by a nail penetrating the left 4th intercostal space at the midclavicular line.
Surface projections of internal organs US Medical PG Question 8: A 33-year-old pregnant woman at 38 weeks gestation requires emergency cesarean section. The obstetrician must perform a perimortem procedure due to maternal cardiac arrest. She makes a Pfannenstiel incision but encounters significant bleeding. The patient has a history of previous cesarean section with documented bladder injury. Considering the surface anatomy and previous surgery, evaluate the most likely source of bleeding and the anatomical relationship that increases risk in this scenario.
- A. External iliac vessels exposed due to loss of normal tissue planes from adhesions
- B. Superficial epigastric vessels in the subcutaneous tissue
- C. Inferior epigastric vessels injured due to lateral extension of the incision (Correct Answer)
- D. Uterine vessels injured due to lower segment extension
- E. Superior vesical arteries injured due to abnormal bladder position from scarring
Surface projections of internal organs Explanation: ***Inferior epigastric vessels injured due to lateral extension of the incision***
- A **Pfannenstiel incision** is a transverse incision performed 2-3 cm above the symphysis pubis; extending this incision too far laterally increases the risk of transecting the **inferior epigastric vessels**.
- These vessels are located deep to the **rectus abdominis** muscle but lateral to its midline, making them susceptible during emergency procedures where rapid extension of the surgical field is required.
*Uterine vessels injured due to lower segment extension*
- The **uterine vessels** are located within the **broad ligament** and are typically injured during the hysterotomy (uterine incision) phase rather than the initial abdominal wall approach.
- While heavy bleeding occurs if the uterine incision extends laterally into the **vascular pedicle**, it does not correlate with superficial anatomical landmarks of a Pfannenstiel incision.
*External iliac vessels exposed due to loss of normal tissue planes from adhesions*
- The **external iliac vessels** are retroperitoneal structures and are generally too deep and lateral to be the primary source of bleeding in a standard **Pfannenstiel incision**.
- Although **adhesions** can distort anatomy, injury to these vessels is more common in extensive pelvic lymphadenectomy or oncological surgeries rather than a perimortem C-section.
*Superficial epigastric vessels in the subcutaneous tissue*
- The **superficial epigastric vessels** run in the **Camper's fascia** and are commonly transected during the initial skin incision, but they rarely cause "significant" or life-threatening bleeding compared to deeper vessels.
- Bleeding from these vessels is usually easily controlled with cautery or pressure and does not represent the primary anatomical risk of lateral **Pfannenstiel extension**.
*Superior vesical arteries injured due to abnormal bladder position from scarring*
- The **superior vesical arteries** supply the upper portion of the bladder; while at risk during dissection of a **scarred bladder flap**, they are not the source encountered during the abdominal wall incision.
- Previous **bladder injury** increases the risk of cystotomy, but the vascular supply to the bladder is located deep within the pelvic cavity, not at the level of the **rectus sheath**.
Surface projections of internal organs US Medical PG Question 9: A 71-year-old man with atrial fibrillation presents with sudden onset of severe abdominal pain out of proportion to physical findings. He has mild diffuse tenderness but no peritoneal signs. His lactate is 4.5 mmol/L. CT angiography shows occlusion of a major mesenteric vessel. The surgeon explains that the occluded vessel supplies the midgut from just distal to the second part of the duodenum to the proximal two-thirds of the transverse colon. Based on surface anatomy, at what vertebral level does this vessel originate?
- A. L3
- B. T12
- C. L1 (Correct Answer)
- D. L2
- E. T10
Surface projections of internal organs Explanation: ***L1***
- The clinical presentation describes **acute mesenteric ischemia** involving the **Superior Mesenteric Artery (SMA)**, which supplies the embryologic **midgut**.
- The SMA originates from the **abdominal aorta** behind the neck of the pancreas at the level of the **L1 vertebra**.
*T10*
- The **esophagus** passes through the diaphragm at the **T10 level** via the esophageal hiatus.
- No major abdominal vascular branches supplying the gastrointestinal tract originate at this specific thoracic level.
*T12*
- This is the level of the **celiac trunk**, which supplies the **foregut** structures including the stomach, liver, and spleen.
- It also marks the **aortic hiatus** where the aorta enters the abdominal cavity from the thorax.
*L2*
- This level corresponds to the origin of the **renal arteries** and the site where the **duodenojejunal flexure** is suspended by the ligament of Treitz.
- While the SMA is in close proximity, its distinct origin from the aorta is characteristically at the **L1 level**.
*L3*
- This is the level of origin for the **Inferior Mesenteric Artery (IMA)**, which supplies the **hindgut** including the distal third of the transverse colon.
- Clinical findings in this case point to midgut ischemia, which is associated with the **Superior Mesenteric Artery** rather than the IMA.
Surface projections of internal organs US Medical PG Question 10: A 25-year-old motorcyclist presents after a high-speed collision with facial trauma. Clinical examination reveals cerebrospinal fluid rhinorrhea, periorbital ecchymosis, and numbness over the cheek and upper teeth. CT shows a fracture extending through a foramen at the apex of the orbit. Based on the clinical presentation and surface anatomy, which foramen is most likely involved?
- A. Foramen rotundum (Correct Answer)
- B. Superior orbital fissure
- C. Infraorbital foramen
- D. Inferior orbital fissure
- E. Optic canal
Surface projections of internal organs Explanation: ***Foramen rotundum***
- The **foramen rotundum** transmits the **maxillary nerve (V2)**; trauma here explains the **numbness over the cheek** and **upper teeth** as these are within the V2 sensory distribution.
- Located at the **apex of the orbit**, this foramen communicates with the pterygopalatine fossa and is frequently involved in high-velocity fractures causing **middle cranial fossa** disruption and CSF rhinorrhea.
*Optic canal*
- The **optic canal** transmits the **optic nerve (CN II)** and the **ophthalmic artery**.
- Damage would result in **visual field defects** or blindness and an abnormal **pupillary light reflex**, rather than facial sensory loss.
*Superior orbital fissure*
- This fissure transmits **CN III, IV, VI** and the **ophthalmic nerve (V1)**; damage would cause **ophthalmoplegia** and forehead numbness.
- It does not carry the **V2 branch**, thus it cannot account for the loss of sensation in the **cheek and upper teeth**.
*Infraorbital foramen*
- While the **infraorbital nerve** (a branch of V2) passes here to supply the cheek, this foramen is on the **anterior surface of the maxilla**, not at the **apex of the orbit**.
- Trauma at this superficial site would not typically present with **CSF rhinorrhea**, which indicates a more deep-seated skull base fracture.
*Inferior orbital fissure*
- This fissure is located between the floor and lateral wall of the orbit but is not situated at the **apex** where the injury is described.
- While it transmits the **infraorbital nerve**, it is not a pathway through which a skull base injury leads to **CSF leakage** into the nasal cavity.
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