1st Semester Anatomy Ta Week 12 Questions

Chyle, a form of lymphatic fluid that drains in the Thoracic duct. It lays in between the esophagus and azygos vein before it drains into the brachiocephalic trunk in the superior mediastinum.

The left phrenic nerve travels over the pericardium to innervate the left side of the diaphragm. A mass that irritates it is likely to cause a hiccup reflex. The recurrent laryngeal nerves either loop around the right subclavian or the arch of the aorta and do not travel over the pericardium. If one these nerves were compressed, it would result in hoarseness of voice. The vagus nerves dive deep to the pericardium and form a plexus around the esophagus. Hiccup reflex afferents are phrenic, vagus, and sympathetic T6-T12 (Bailey 1943).

the pulmonary arteries receive blood from the right ventricle. The left ventricle shuttles blood into the aorta. The pulmonary veins contain oxygenated blood and fill the left atrium. The left brachiocephalic vein shuttles blood into the SVC and then into the right atrium. Emboli often arise from stagnant blood in the legs (deep vein thrombosis) and can occur during long flight travel or prolonged bed rest. This travels up the IVC and into the right atrium without involving the left brachiocephalic vein.

Of the answer choices listed, only the azygos vein and esophagus are located in the posterior mediastinum. The difficulty in swallowing (dysphagia) suggests it is most likely compressing the esophagus.

the Arch of the aorta is more commonly located at the T4-T5 vertebral level.

the posterior Mediastinum does not contain the cervical ganglia typically associated with Horners. The other choices are correct as they may compress the Recurrent Laryngeal, Esophagous and if large enough, the Left atrium.

all the others may compress the trachea as well, but the RSC doesn't involve the trachea. Double SVC would not necessarily cause dysphagia.

A pericardiocentesis can be done through the 5th or 6th intercostal space at the left sternal border at the cardiac notch of the left lung to avoid puncturing the lungs.

The greater splanchnic nerve contains pre-ganglionic sympathetic fibers that exit the spinal cord from the lateral horn. The lateral horn is associated with sympathetics “thoraco-lumbar”. There is no lateral horn in the “cranio-sacral” (parasympathetic) portions of the spinal cord.
The fibers that exit the spinal cord go through the sympathetic chain, but they do not synapse there. They exit the chain ganglia as the Greater Splanchnic nerve. This nerve the travels to the celiac ganglion (where it synapses) and provides innervation to the abdominal viscera.

This is a classic clinical finding of Superior Vena Cava Syndrome. The enlarged thymus and a confirmatory biopsy most likely indicates a thymoma. Remember, after puberty the thymus undergoes involution and its largely replaced with fat in the adult. Hence, a thymic shadow in adults is considered pathological. Furthermore, SVC Syndrome patients commonly present with dyspnea (shortness of breath), enlarged neck veins, and edema due to compression of enlarged surrounding structure(s) such as a thymoma in this case. Think of it kind of like a backlogged toilet if you will ;). To circumvent the situation, your body naturally develops collateral circulation to return the deoxygenated venous blood back into the right atrium. The most important vein involved in this venous anastomoses, is the azygos vein. Physiologically, the azygos vein drains into the SUPERIOR vena cava. During collateral circulation, the azygos vein follows a different route into the lumbar veins, then into the INFERIOR vena cava, and finally into the right atrium.

There are three pathways of venous collateral circulation: the azygos-hemiazygous pathway, the internal thoracic pathway, and the lateral thoracic pathway. This one is straight from Posterior mediastinum slides.