Mediastinum MCQs

Explanation: The oesophagus has three classical anatomical constrictions , plus a fourth minor one clinically important: Cervical constriction At cricopharyngeus muscle (C6) Thoracic (aortic) constriction At aortic arch (T4) (Option A) Bronchial constriction Where it is crossed by left main bronchus (T5) (Option B) Diaphragmatic constriction Where it passes through diaphragm at T10 (Option C) Key takeaways : The oesophagus shows 4 constrictions : At its beginning, crossed by cricopharyngeus. 15 cm from the incisor teeth Crossed byaortic arch, 22.5 cm from incisor teeth Crossed by left bronchus, 27.5 cm from incisor teeth Pierces the diaphragm, 37.5 cm from incisor teeth

The sternal angle is a very important anatomical landmark which is used when placing the stethoscope and listening for heart sounds. The sternal angle is the location of the attachment of the costal cartilage of the second rib to the sternum. So, once you locate the sternal angle on a patient, you know the location of the second rib, and you can use that landmark to find the right spots to auscultate each valve of the heart. Also remember that a horizontal plane through the sternal angle passes through the T4/T5 intervertebral disc and marks the inferior boundary of the superior mediastinum. Reference: Textbook of Gray's Anatomy for students, 3rd Edition, Thorax, Page number - 127

C i.e. T5 vertebrae Thoracic duct begins as continuation of the upper end of the cisterna chyli near the lower border of T12 vertebra and enters the thorax through the aortic opening of diaphragm (at T12 ). It then ascends through the posterior mediastinum and at T5 level crosses from right side to the left side and ascends along left margin ofoesophagus to enter the neck

The azygos system of veins are indirect descendants of the posterior cardinal veins, although arch of the azygos is old right posterior cardinal. The point at which azygos arch empties into superior vena cava in the adult marks the junction of old anterior cardinal above with old common cardinal below. Reference - Textbook of Langman's, 12th Edition, Cardiovascular System Embryology Page number - 171

The hemiazygos vein crosses from the left to the right side at the level of T8 vertebrae. Reference : Textbook of Gray's Anatomy for students, 3rd Edition, Thorax, Page number - 127

In the given case scenario of an inhaled foreign body, it is most likely to lodge into the right bronchus. The right bronchial veins drain to the azygos vein. Left bronchial veins drain into the accessory hemiazygos Reference : Textbook of Gray's Anatomy for students, 3rd Edition, Thorax, Page number - 180

The thoracic duct lies in the posterior mediastinum between the aorta on its left and the azygos vein on its right. These three structures are all found posterior to the esophagus. The greater thoracic splanchnic nerve lies anterior to the vertebral bodies, behind the azygos, thoracic duct, and aorta. The left recurrent laryngeal nerve is found in the middle mediastinum, looping under the aortic arch before it ascends to the larynx. The right pulmonary artery is also in the middle mediastinum--it leaves the heart and enters the root of the right lung. The sympathetic trunk lies on the heads of the ribs on the posterior wall of the thorax. Reference: Textbook of Gray's Anatomy for students, 3rd Edition, Thorax, Page number - 162

Below the level of the sternal angle, the thoracic duct lies posterior to the esophagus, between the azygos vein and the descending aorta. So, if the azygos vein became dilated, it could impinge on the thoracic duct. The trachea is superior to the azygos vein, which loops over the right bronchus before emptying into the superior vena cava. This means that a dilated azygos vein would have little impact on the trachea. Because the azygos is on the right side of the body, it could not compress anything at the root of the left lung. The right phrenic nerve is anterior to the azygos vein. The descending aorta is much larger and more muscular than the azygos vein, so it is unlikely that it would be compressed by this much smaller structure. Reference: Textbook of Gray's Anatomy for students, 3rd Edition, Thorax, Page number - 206