Mediastinum

Mediastinum Superior mediastinum Inferior mediastinum A. Anterior B. Middle C. Posterior

superior mediastinum: [Green] Inferior Mediastinum: Below the plane passing from Sternal Angle/Angle Luise Inferior mediastinum has 3 parts: Purple: anterior mediastinum; Yellow: middle mediastinum; Blue: posterior mediastinum

Superior mediastinum The superior mediastinum is posterior to the manubrium of the sternum and anterior to the bodies of the first four thoracic vertebrae. The superior mediastinum is continuous with the neck superiorly and with the inferior mediastinum inferiorly.

Major structures found in the superior mediastinum From Posterior to anterior Layer 1: Esophagus Layer 2: Trachea Layer 3: Arch of the aorta with its three large branches Layer 4: Right and left brachiocephalic veins, Superior vena cava Layer 5: Thymus

Major structures found in the superior mediastinum Thymus Right and left brachiocephalic veins Left superior intercostal vein Superior vena cava Arch of the aorta with its three large branches Trachea Esophagus

Phrenic nerves Vagus nerves Left recurrent laryngeal branch of the left vagus nerve Thoracic duct

Superior vena cava The vertically oriented superior vena cava begins posterior to the lower edge of the right first costal cartilage, where the right and left brachiocephalic veins join, and terminates at the lower edge of the right third costal cartilage, where it joins the right atrium. The superior vena cava receives the azygos vein immediately before entering the pericardial sac

Arch of aorta and its branches Only the arch of the aorta is in the superior mediastinum. It begins when the ascending aorta emerges from the pericardial sac and courses upward, backward, and to the left as it passes through the superior mediastinum, ending on the left side at vertebral level TIV/V.

Trachea and esophagus The trachea is a midline structure that is palpable in the jugular notch as it enters the superior mediastinum. Posterior to it is the esophagus, which is immediately anterior to the vertebral column.

Left recurrent laryngeal nerve The left vagus nerve also gives rise to the left recurrent laryngeal nerve, which arises from it at the inferior margin of the arch of aorta just lateral to the ligamentum arteriosum. Entering a groove between the trachea and esophagus, the left recurrent laryngeal nerve continues superiorly to enter the neck and terminate in the larynx.

CT (Computed tomography)

T-3

T-4/T5 Sternal angle

CT scan inferior to T4/T5 Right Atrium. Left Atrium. Right Ventricle. Left Ventricle. Descending Aorta. Transverse Process of T7. Right Bronchus. Left Bronchus

Cardiovascular shadows

MEDIASTINUM In chest PA view, mediastinum has Two borders, left and right

Heart

MEDIASTINAL BORDER Right border is formed by - Form above downwards Right bracheocephalic vessels Ascending aorta and superimposed SVC Right atrium Inferior vena cava

MEDIASTINAL BORDER Left border is formed by - from above downwards Left bracheocephalic vessels Aortic arch Pulmonary trunk Left atrial appendage Left ventricle

Coronary arteriograms

coronary arteriogram

Posterior mediastinum

Posterior mediastinum The posterior mediastinum is posterior to the pericardial sac and diaphragm and anterior to the bodies of the mid and lower thoracic vertebrae

Major structures in the posterior mediastinum Esophagus and its associated nerve plexus Thoracic aorta and its branches Azygos system of veins Thoracic duct and associated lymph nodes Sympathetic trunks Thoracic splanchnic nerves

Esophagus Relationships to important structures in the posterior mediastinum 1. Posterior to the esophagus, the thoracic duct is on the right side inferiorly, but crosses to the left more superiorly. 2. Esophagus passes immediately posteriorly to the left atrium, separated from it only by pericardium

Thoracic aorta The thoracic portion of the descending aorta (thoracic aorta) begins at the lower edge of vertebra TIV. Branches of the thoracic aorta 1. Pericardial branches 2. Bronchial branches 3. Esophageal branches 4. Posterior intercostal arteries 5. Superior phrenic arteries 6. Subcostal artery

Azygos vein The azygos vein arises opposite vertebra LI or LII at the junction between the right ascending lumbar vein and the right subcostal vein. The azygos vein enters the thorax through the aortic hiatus of the diaphragm. At approximately vertebral level TIV, it arches anteriorly, over the root of the right lung, to join the superior vena cava

Thoracic duct in the posterior mediastinum The thoracic duct is the principal channel through which lymph from most of the body is returned to the venous system. It begins as a confluence of lymph trunks in the abdomen, sometimes forming a saccular dilation referred to as the cisterna chyli (chyle cistern), which drains the abdominal viscera and walls, pelvis, perineum, and lower limbs. Thoracic duct empties into the junction of the left subclavian and left internal jugular veins.

Sympathetic trunks Sympathetic trunks consists of two parallel cords punctuated by 11 or 12 ganglia. Thoracic splanchnic nerves 1. Greater splanchnic nerve 2. Lesser splanchnic nerve 3. Least splanchnic nerve (lowest splanchnic nerve)

Anterior mediastinum The anterior mediastinum is posterior to the body of the sternum and anterior to the pericardial sac CONTENTS: Sterno paricardial ligaments Few lymph nodes Branches of the internal thoracic vessels. In infants and children, the anterior mediastinum contains the inferior part of the thymus.