A 55-year-old man is brought to the emergency department due to shortness of breath, productive cough, and confusion. His wife mentions that last week he was diagnosed with the flu and his symptoms have progressively worsened. Temperature is 39.4 C (103 F), blood pressure is 80/50 mm Hg, pulse is 120/min, and respiratory rate is 22/min. Pulse oximetry shows 86% on room air. On physical examination, the patient is obtunded and in respiratory distress. He is intubated, given a 2-L bolus of normal saline, and started on broad spectrum antibiotics after blood cultures are obtained. A central line is placed to access a structure embryonically derived from the common cardinal veins. This structure is represented by which of the following labels shown in the chest CT scan below?

Question

A 55-year-old man is brought to the emergency department due to shortness of breath, productive cough, and confusion.  His wife mentions that last week he was diagnosed with the flu and his symptoms have progressively worsened.  Temperature is 39.4 C (103 F), blood pressure is 80/50 mm Hg, pulse is 120/min, and respiratory rate is 22/min.  Pulse oximetry shows 86% on room air.  On physical examination, the patient is obtunded and in respiratory distress.  He is intubated, given a 2-L bolus of normal saline, and started on broad spectrum antibiotics after blood cultures are obtained.  A central line is placed to access a structure embryonically derived from the common cardinal veins.  This structure is represented by which of the following labels shown in the chest CT scan below?

Quizplus · Accepted Answer

11ec160b_3559_03b0_9249_77bcf5c74790_MD0001_00 Patients with hemodynamic instability or shock often have central lines placed into the central venous system to allow rapid infusion of intravenous fluids, blood, and vasopressors. The catheter is usually inserted into the neck (internal jugular vein) or chest (subclavian vein), and is advanced until the catheter tip enters the superior vena cava (SVC). The SVC is derived from the common cardinal veins. On CT scan imaging of the upper thorax, the SVC can be identified to the right of the heart, posterolateral to the ascending aorta, anterior to the right pulmonary artery, and just below the level of the carina. All veins in the developing embryo ultimately drain into the sinus venosus, which drains into the primitive atrium of the developing heart. In early embryonic development, the body's veins fall into 3 main groups: umbilical, vitelline, and cardinal veins. The umbilical vein degenerates, the vitelline veins form the portal system, and the cardinal veins form constituents of the systemic venous circulation. (Choice B) The ascending aorta develops from the truncus arteriosus, which also gives rise to the pulmonary trunk. A portion of the aortic arch develops from the fourth branchial (pharyngeal) arch. (Choice C) The pulmonary trunk is derived from the truncus arteriosus. Neural crest cell migration helps partition the truncus arteriosus into the 2 great arteries (aorta and pulmonary artery) by causing fusion and twisting of the truncal and bulbar ridges. This process results in the normal spiral relation between the aorta and pulmonary artery. Failure of this process results in transposition of the great vessels and tetralogy of Fallot. (Choice D) The esophagus is embryologically derived from the endodermal foregut. In the thoracic cavity, it descends posterior to the trachea and anterior to the vertebrae. (Choice E) The descending aorta is derived from fusion of the embryonic right and left dorsal aortas. In the thoracic cavity, it starts left of the vertebral column and approaches the midline as it descends toward the diaphragm. Educational objective: The common cardinal veins of the developing embryo drain directly into the sinus venosus. These cardinal veins ultimately give rise to the superior vena cava and other constituents of the systemic venous circulation. __________ References: Misplaced central venous catheters: Applied anatomy and practical management. (http://www.ncbi.nlm.nih.gov/pubmed/23384735)

A 55-Year-Old Man Is Brought to the Emergency Department Due