GL 15 - Anterior and Superior Mediastinum

Mediastinum

This is the area between the sternum and the pleural cavities

F

T/F: The mediastinum is not a movable partition

Thoracic outlet and root of the neck

The mediastinum extends superiorly to what structure?

Diaphragm

The mediastinum extends inferiorly to what structure?

Sternum

The mediastinum extends anteriorly to what structure?

Vertebral column

The mediastinum extends posteriorly to what structure?

Heart, Remnant of thymus, trachea, esophagus, thoracic duct, vagus nerve, phrenic nerve, and sympathetic trunk

Give the structures inside the mediastinum

Sternal Angle of Louis and Lower border of TV4

The mediastinum is divided into superior and inferior by an imaginary line passing through what through what structures (Anteriorly and Posteriorly)?

Manubriosternal Joint, 2nd Sternocostal joint, Demarcation between ascending aorta and aortic arch, Demarcation between aortic arch and descending aorta, Carina, Level of L primary bronchus, TV4 IVD

Give the structures of the mediastinum from anterior to posterior

Manubrium sterni

Anterior boundary of superior mediastinum

TV1-4

Posterior boundary of superior mediastinum

Thymus, Trachea, Esophagus, Thoracic Duct, and Sympathetic trunks

Contents of the superior mediastinum

Thymus

This is a flattened, bilobed structure between the sternum and the pericardium

Puberty

When does the thymus reach its largest size?

Newborn Infant

When does the thymus reach its largest size relative to body size?

Involution

Process that the thymus undergoes after puberty

Development of the T lymphocytes

Function of the thymus

Inferior thyroid and Internal thoracic artery

2 arteries that supply the thymus

Subclavian and internal jugular veins

The brachiocephalic vein is formed via the union of what 2 veins?

Level of the sternoclavicular joint

Commencement of the brachiocephalic veins

1st R chondrosternal junction

Termination of the brachiocephalic veins

1 > 2

QC: Length of (1) L (2) R Brachiocephalic vein

More vertical

Compare the verticality of R brachiocephalic vein against the L brachiocephalic vein

SVC

Structure formed by the union of the 2 brachiocephalic veins

Thoracic duct and Inferior thyroid veins

Tributaries special to the L brachiocephalic compared to R

1st CC

Commencement of the SVC

3rd CC

Termination of the SVC

Brachiocephalic and azygos veins

Tributaries of the SVC

Anterior mediastinum

This subdivision of the inferior mediastinum is the space between the sternum and pericardium

Middle mediastinum

This subdivision of the inferior mediastinum consists of the pericardium and the heart

Posterior mediastinum

This subdivision of the inferior mediastinum is the space between the pericardium and the vertebral column

Upward and Forward

The ascending aorta run in what direction?

Fibrous pericardium

The ascending aorta lies within what part of the medial mediastinum?

Coronary artery

These are the branches of the ascending aorta

Manubrium sterni

The aortic arch lies in the superior mediastinum behind what structure?

Upward, Backward, and to the left

What direction does the aortic arch initially run?

Brachiocephalic trunk, Left Common carotid, Left subclavian artery

3 branches of the aortic arch (In order)

Right subclavian and Right common carotid

2 branches of the brachiocephalic artery

Ligamentum arteriosum

This is the remnant of the structure that connected the aortic arch to the pulmonary trunk

Ductus arteriosus

The ligamentum arteriosum is a remnant of what structure?

Patent Ductus Arteriosus

This is a condition where the aortic blood enters the pulmonary circulation

Pulmonary Plexus

The vagus nerves pass behind the root of the lung to assist in the formation of what structure?

F; The right vagus nerve passes to the posterior surface while the left passes to the anterior surface

T/F: The right vagus nerve passes to the anterior surface of the esophagus while the left vagus nerve passes to the posterior surface of the esophagus and they will both form the esophageal plexus

T

T/F: Both vagus nerves pass through the esophageal opening but the L vagus will reach the anterior surface of the stomach while the R vagus will reach its posterior surface

Right subclavian artery

The right recurrent laryngeal nerve hooks around what structure?

Aortic Arch

The left recurrent laryngeal nerve hooks around what structure?

Higher origin

Compare the origin of the R recurrent laryngeal nerve compared to the L

Recurrent laryngeal nerve

These nerves provide major motor and sensory supply to the larynx

Anterior rami of C3-C5

The phrenic nerve arises from what structure?

Brachiocephalic vein and SVC

The R phrenic nerve descends the thorax along what structure?

In front

Both phrenic nerve pass ____ of the root of the lung

Left Subclavian artery

The L phrenic nerve descends the thorax along what structure?

Right atrium

The R phrenic nerve runs along the R side of the pericardium, separating it from what structure?

Left ventricle

The L phrenic nerve runs along the L side of the pericardium, separating it from what structure?

F; The R passes but the L pierces the muscle

T/F: Both phrenic nerves pass through the caval opening in the diaphragm to supply the central part of the peritoneum on its abdominal aspect

Vagus nerve

The L phrenic nerve crosses the left side of the aortic arch, crossing over that nerve?

T

T/F: The phrenic nerve has both motor and sensory fibers

Sympathetic trunk

This is the most laterally placed structure in the mediastinum and runs downward on the heads of the ribs

TV 12

The sympathetic trunk leaves the thorax on the side of the body on which vertebra

Medial arcuate ligament of the diaphragm

The sympathetic trunk leaves the thorax on the side of the body on a vertebra by passing behind what structure?

1st ganglion of the sympathetic trunk + Inferior cervical ganglion

What forms the stellate ganglion?

Air crackles

During palpation, what can be expected when someone has a subcutaneous emphysema

Boerhaave’s Syndrome

This is a full thickness tear of the esophagus that can cause toxic content to leak out and cause infections

Forceful and repeated vomiting

Most common cause of strain in boerhaave’s syndrome

Pneumomediastinum and subcutaneous edema

2 key features seen in boerhaave’s syndrome

Aortic dissection, aneurysm, enlarged pulmonary arteries, and abnormalities of the great vessels

Vascular causes of mediastinal widening

Upper and middle lobe collapse

Pulmonary causes of mediastinal widening