L13. GA - Superior & Inferior Mediastiana

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Questions and Answers

What structure is formed by the left and right brachiocephalic veins?

Inferior vena cava

Azygos vein

Superior vena cava (correct)

Pulmonary trunk

Which branch does NOT originate from the arch of the aorta?

Right coronary artery (correct)

Left subclavian artery

Left common carotid artery

Brachiocephalic trunk

Where does the left recurrent laryngeal nerve hook below?

Left pulmonary trunk

Right subclavian artery

Ligamentum arteriosum (correct)

Left common carotid artery

Which clinical procedure commonly utilizes the axis of the superior vena cava and inferior vena cava?

Insertion of an IVC filter Signup and view all the answers

How does the arch of the aorta position itself in relation to the trachea?

Runs in front of the trachea Signup and view all the answers

What is the relationship of the right vagus nerve to the first part of the subclavian artery?

Crosses anterior to it Signup and view all the answers

Which structure does the azygos vein drain into before entering the pericardial sac?

Superior vena cava Signup and view all the answers

Which nerve descends on the lateral surface of the superior vena cava?

Phrenic nerve Signup and view all the answers

What is the primary role of the phrenic nerves?

Motor to the diaphragm and sensory to the pericardium Signup and view all the answers

Where does the trachea bifurcate into the left and right main bronchi?

Near the sternal angle and between TV4/TV5 Signup and view all the answers

Which structure is located posterior to the pericardial sac and diaphragm?

Thoracic duct Signup and view all the answers

What is the anatomical starting point of the thoracic aorta?

At TV4 Signup and view all the answers

Which structure primarily contributes to the high-pressure zone of the upper esophageal sphincter?

Cricopharyngeus muscle Signup and view all the answers

How does the thoracic aorta change direction as it descends?

Slants to the right after starting left Signup and view all the answers

Which blood vessels supply arterial blood to the esophagus?

Inferior thyroid artery, aorta, and left gastric artery Signup and view all the answers

Which structure does NOT drain venous blood from the esophagus?

Mesenteric veins Signup and view all the answers

Which of the following is NOT a component of the posterior mediastinum?

Pulmonary arteries Signup and view all the answers

What arteries accompany the phrenic nerves?

Pericardiophrenic arteries Signup and view all the answers

What is a primary function of the esophageal plexus of the vagus nerve?

Increase peristalsis and secretion Signup and view all the answers

In which anatomical location is the lower esophageal sphincter found?

At the junction of the thoracic and abdominal esophagus Signup and view all the answers

At which vertebral level does the thoracic aorta leave the thorax?

TV12 Signup and view all the answers

Which nerve plexus is associated with the esophagus?

Esophageal nerve plexus Signup and view all the answers

Which of the following branches is NOT given off by the thoracic aorta?

Coronary branches Signup and view all the answers

What demarcates the superior mediastinum from the inferior mediastinum?

Imaginary line between the sternal angle and the disc between TV4-TV5 Signup and view all the answers

Which components are found in the middle mediastinum?

Heart and pericardium Signup and view all the answers

Where is the superior mediastinum located?

Behind the manubrium, in front of TV1-TV4 Signup and view all the answers

What is the primary arterial supply to the thymus gland?

Internal thoracic artery via anterior intercostal branches Signup and view all the answers

What notable changes occur to the thymus gland after puberty?

It begins to regress and is replaced by fat Signup and view all the answers

Which structures are NOT part of the principal contents of the superior mediastinum?

Lumbar plexus Signup and view all the answers

How does lymphatic drainage from the thymus gland typically occur?

To parasternal nodes, tracheobronchial nodes, or neck roots Signup and view all the answers

Which mediastinal division is found posterior to the heart and pericardium?

Posterior mediastinum Signup and view all the answers

What is a common clinical significance of the thymus gland?

It can host ectopic parathyroid glands Signup and view all the answers

Which structure is primarily responsible for the production of certain hormones related to calcium homeostasis?

Thymus Signup and view all the answers

What is the primary function of the thoracic duct in the body?

Lymphatic drainage Signup and view all the answers

Which major vessel is directly involved in delivering blood from the heart to the rest of the body?

Thoracic Aorta Signup and view all the answers

Which nerve plays a crucial role in controlling heart rate and other autonomic functions?

Vagus Nerve Signup and view all the answers

Which of the following structures is NOT part of the posterior mediastinum?

Vagus Nerve Signup and view all the answers

In cases of traumatic aortic injury, which anatomical area is crucial for evaluation?

Aortic Isthmus Signup and view all the answers

What is the primary structural role of the trachea within the mediastinum?

Conduct airflow to the lungs Signup and view all the answers

Which of the following is a consequence of injury to the recurrent laryngeal nerve?

Changes in vocal quality Signup and view all the answers

Which structure is primarily responsible for draining venous blood from the thoracic wall into the superior vena cava?

Azygos System of Veins Signup and view all the answers

What is a major function of the esophagus within the posterior mediastinum?

Facilitating digestion Signup and view all the answers

Study Notes

Superior Mediastinum

Located between the manubrium and TV1-TV4.
Contains the arch of the aorta and its branches, brachiocephalic veins and SVC, vagus and phrenic nerves, left recurrent laryngeal nerve, sympathetics, trachea, esophagus, thoracic duct and thymus gland.

Thymus

Bi-lobar organ located behind the manubrium, extends into the anterior mediastinum.
Essential for immune system development, largest at puberty and regresses later in life.
Supplied by the internal thoracic artery and drains into the left brachiocephalic vein.
Parathyroid gland development is associated with the thymus, leading to ectopic parathyroid glands and potentially ectopic hormone production.

Great Vessels

Right and left brachiocephalic veins are located behind the thymus, formed by the junction of the internal jugular and subclavian veins.
The left brachiocephalic vein crosses to the right and joins the right brachiocephalic vein to form the SVC.
SVC carries blood from all structures superior to the diaphragm, except the heart and lungs.
It receives the azygos vein before entering the pericardial sac.
SVC and IVC share a vertical axis, making it possible to pass guidewires/catheters from SVC through the right atrium into the IVC.
Common procedure for inserting IVC filters to catch emboli from lower limbs/pelvis (DVT).

Arch of the Aorta

Ascending aorta exits the pericardial sac, extends to the sternal angle, and continues as the arch of the aorta.
Runs upward, to the left, and backward/downward over the left main bronchus and pulmonary trunk.
Occupies a nearly sagittal plane behind the manubrium.
Branches of the arch include the brachiocephalic trunk, left common carotid artery, and left subclavian artery.
Ligamentum arteriosum connects the pulmonary trunk to the arch distal to the left subclavian artery.

Vagus Nerve

Right vagus nerve crosses anterior to the first part of the subclavian artery, descends on the right side of the trachea, then posterior to the root of the right lung, giving branches to supply the lung.
The right recurrent laryngeal nerve loops posterior to the subclavian artery and ascends in the neck.
Left vagus nerve descends anterior to the arch of the aorta, then posterior to the root of the left lung.
The left recurrent laryngeal nerve leaves the left vagus at the arch of the aorta, loops below the arch, and ascends at the right side of the arch between the trachea and esophagus.

Phrenic Nerve

Right phrenic nerve descends on the lateral surface of the SVC.
Left phrenic nerve crosses the arch of the aorta.
Both nerves descend anterior to the roots of the lungs between the fibrous pericardium and mediastinal pleura.
They supply the diaphragm with motor function and provide sensory innervation to the pericardium and diaphragmatic pleura.

Trachea

Located midline, palpable in the jugular notch as it enters the superior mediastinum.
Lies anterior to the esophagus.
Divides into the left and right main bronchi near the transverse plane between the sternal angle and TV4/TV5.

Posterior Mediastinum

Located behind the pericardial sac and diaphragm.
Lies in front of TV5-TV12.
Contains the thoracic aorta and branches, esophagus and its nerve plexus, thoracic duct, azygos venous system, sympathetic trunks, and thoracic splanchnic nerves.

Thoracic Aorta

The thoracic portion of the descending aorta, continuous with the arch.
Begins at TV4, initially left of the midline, then slants right, and exits the thorax near the midline at TV12 through the aortic hiatus of the diaphragm.
Supplies parietal and visceral branches throughout its course (posterior intercostal, subcostal, superior phrenic, bronchial, esophageal, pericardial).

Esophagus

Located posterior to the trachea.
Supplied by the inferior thyroid artery, thoracic aorta, and left gastric artery.
Venous drainage into the inferior thyroid veins, azygos system, and left gastric vein (LGV).
Lymphatic drainage into posterior mediastinal and left gastric nodes.
Communication between the LGV and azygos system connects the portal system and systemic veins, leading to potential bleeding in portal hypertension.
Narrowing occurs at the upper esophageal sphincter, where the arch of the aorta crosses, at the esophageal opening in the diaphragm, and at the lower esophageal sphincter.
Upper esophageal sphincter prevents air entry during breathing and reflux into the pharynx. The cricopharyngeus muscle contributes to the high-pressure zone.
Lower esophageal sphincter (LOS) generates tonic pressure, preventing reflux of gastric contents.

Thoracic Duct

Begins at the cisterna chyli, as a lymphatic sac between the aorta and right crus of the diaphragm.

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Description

Explore the key structures located within the superior mediastinum, including the thymus, great vessels, and nerves. This quiz covers the anatomy and functions of these critical components of the thoracic cavity. Test your knowledge on their roles and connections in the human body.