Mediastinum Anatomy Overview

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Questions and Answers

Define the mediastinum.

It is the thoracic region between the two lungs, between the sternum and vertebrae. It houses the heart, great vessels, etc.

Where is the superior mediastinum?

Above the sternal angle.

Where is the inferior mediastinum?

Below the sternal angle.

What vertebrae is equivalent to the sternal angle?

T4. Signup and view all the answers

What is the landmark for the division between the superior and inferior mediastinum?

The sternal angle (angle of Louis). Signup and view all the answers

Where is the arch of aorta?

Over the sternal angle. Signup and view all the answers

Where is the bifurcation of the trachea?

The carina is at the sternal angle. Signup and view all the answers

Where is the bifurcation of the pulmonary trunk?

Just under the sternal angle. Signup and view all the answers

Where is the ligamentum arteriosum?

Exactly on the sternal angle. Signup and view all the answers

List the contents of the superior mediastinum, from anterior to posterior.

Thymus, brachiocephalic veins leading to SVC, vagus nerves, cardiac plexus and phrenic nerves, arch of aorta and branches, trachea, esophagus. Signup and view all the answers

What is the venous angle?

It is the site where lymph trunks enter the venous system. Signup and view all the answers

The thymus is most active in , producing .

children, T-lymphocytes. Signup and view all the answers

What is involution?

The process (at puberty) of lymphocytes migrating from the thymus to the rest of the body, leaving only fatty tissue. Signup and view all the answers

Where is the anterior mediastinum and what does it contain?

Between pericardium and sternum. Contains fatty tissue, lymph nodes, and internal thoracic artery. Signup and view all the answers

Where is the middle mediastinum and what does it contain?

Contains pericardial cavity and contents. Includes pericardium, heart, ascending aorta, pulmonary trunk. Signup and view all the answers

Where is the posterior mediastinum and what does it contain?

Posterior to the heart. Contains critical structures: descending thoracic aorta, esophagus, thoracic duct, azygos system of veins. Signup and view all the answers

Describe the positioning of the esophagus in relation to the aorta.

<ol> <li>Starts posterior to the aorta and trachea. 2. Stays medial as the aorta arches to the left. 3. Becomes anterior to the aorta as the aorta moves near to the midline at the diaphragm.</li> </ol> Signup and view all the answers

What is Boerhaave syndrome?

Usually accompanies bulimia. Results in esophageal rupture followed by mediastinitis and in air in the mediastinum (pneumomediastinum), followed by sepsis requiring antibiotics. Signup and view all the answers

Azygos system of veins are towards the side of the body, though often it is in the .

right, middle. Signup and view all the answers

Where does the azygos vein receive its supply superiorly?

From the superior intercostal vein. Signup and view all the answers

Where does the azygos vein begin inferiorly?

At the junction of the subcostal vein with the ascending lumbar vein. Signup and view all the answers

Where is the azygos vein in relation to the esophagus?

Posterior. Signup and view all the answers

Where do the hemiazygos system of veins cross?

Midline to drain into azygos vein around T8. Signup and view all the answers

Where are hemiazygos veins usually found?

Usually far on left side. Signup and view all the answers

The azygos vein receives drainage from the thoracic wall while the hemiazygos system drains the thoracic body wall.

right, left. Signup and view all the answers

If there is an absence of the hepatic portion of the inferior vena cava, where does the IVC go?

It drains into the ascending lumbar vein, to the azygos vein, to the superior vena cava directly (it does not go through the liver). Signup and view all the answers

What lymph trunks drain into venous angles?

Bronchomediastinal, subclavian, jugular. Signup and view all the answers

Where does the thoracic duct drain exclusively into?

The left venous angle. Signup and view all the answers

What is a thoracic duct injury?

A complication of thoracic or neck surgery that results in leakage of lymph (chyle), a milky fluid, and in major nutritional deficiencies. Signup and view all the answers

What is a hiatus hernia?

Happens when part of the stomach breaches through the esophageal hiatus of the diaphragm to lie in the lower posterior mediastinum. Antacids can reduce some of the problems but severe cases require surgery. Can cause GERD and in turn, cancer. Signup and view all the answers

Study Notes

Mediastinum Overview

The mediastinum is the thoracic region located between the lungs, sternum, and vertebrae, housing critical structures like the heart and great vessels.

Superior Mediastinum

Located above the sternal angle.
Contains crucial components such as the thymus, brachiocephalic veins leading to the superior vena cava (SVC), vagus nerves, the arch of the aorta, trachea, and esophagus.

Inferior Mediastinum

Situated below the sternal angle, divided into anterior, middle, and posterior sections.
The division between superior and inferior mediastinum is marked by the sternal angle (angle of Louis).

Anatomical Landmarks

The sternal angle correlates with T4 vertebra.
Important structures associated with the sternal angle include the arch of the aorta and the carina where the trachea bifurcates.

Anterior Mediastinum

Positioned between the pericardium and sternum.
Contains fatty tissue, lymph nodes, and the internal thoracic artery.

Middle Mediastinum

Encloses the pericardial cavity, consisting of the pericardium, heart, ascending aorta, and pulmonary trunk.

Posterior Mediastinum

Located posterior to the heart, housing the descending thoracic aorta, esophagus, thoracic duct, and azygos veins.

Esophagus Positioning

The esophagus begins posterior to the aorta and trachea, remains medial as the aorta arches, and becomes anterior to the aorta at the diaphragm.

Thymus Gland

Most active in children, producing T-lymphocytes.
Involution occurs at puberty, with lymphocytes migrating away, leaving fatty tissue.

Azygos System of Veins

Primarily located on the right side, receiving blood from the right thoracic wall while the hemiazygos system collects from the left.
The azygos vein arises from the superior intercostal vein and starts at the junction of the subcostal vein and ascending lumbar vein, positioned posterior to the esophagus.

Mediastinitis and Boerhaave Syndrome

Boerhaave syndrome commonly follows bulimia, leading to esophageal rupture, mediastinitis, and pneumomediastinum with potential sepsis, necessitating antibiotics.

Hemiazygos Veins

Typically found on the far left side, they cross the midline around T8 to drain into the azygos vein.

Lymphatic Drainage

Venous angles receive lymph trunks: bronchomediastinal, subclavian, and jugular.
The thoracic duct drains exclusively into the left venous angle.

Thoracic Duct Injury

Defined as leakage of lymph (chyle) following thoracic or neck surgery, potentially resulting in major nutritional deficiencies.

Hiatus Hernia

Occurs when stomach portions breach the esophageal hiatus of the diaphragm, lying in the lower posterior mediastinum.
Antacids can alleviate symptoms, but severe cases may require surgery, leading to conditions such as GERD and cancer.

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Description

Explore the anatomy of the mediastinum, which includes important structures located between the lungs, sternum, and vertebrae. This quiz covers the superior and inferior mediastinum, their divisions, and key anatomical landmarks such as the sternal angle. Test your knowledge on the critical components housed in this thoracic region.