Anatomy of the Mediastinum Quiz

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Questions and Answers

What is the posterior boundary of the anterior mediastinum?

Transversus thoracis muscle

Body of the sternum

Pericardium (correct)

Diaphragm

Which structure is NOT found in the middle mediastinum?

Pulmonary trunk

Heart

Descending thoracic aorta (correct)

Bifurcation of trachea

Which of the following is a component of the posterior mediastinum?

Esophagus (correct)

Sternopericardial ligament

Ascending aorta

Phrenic nerves

What is the inferior boundary of the middle mediastinum?

Diaphragm Signup and view all the answers

Which vein is formed at the root of the neck by the union of the right subclavian and the right internal jugular veins?

Right brachiocephalic vein Signup and view all the answers

Which structure lies anterior to the left brachiocephalic vein?

Manubrium sterni Signup and view all the answers

Which lymph nodes are specifically mentioned in relation to the posterior mediastinum?

Posterior mediastinal lymph nodes Signup and view all the answers

What connects the body of the sternum to the fibrous pericardium?

Sternopericardial ligament Signup and view all the answers

What is the function of the thyroid ima artery?

To contribute to the vascular supply of the thyroid gland Signup and view all the answers

Where does the left common carotid artery originate from?

The aortic arch on the left side Signup and view all the answers

What major region does the left subclavian artery supply?

The left upper limb Signup and view all the answers

At which vertebral level does the descending thoracic aorta begin?

4th thoracic vertebra Signup and view all the answers

Which arteries branch off the descending thoracic aorta?

Posterior intercostal arteries and subcostal arteries Signup and view all the answers

Where does the pulmonary trunk terminate?

In the concavity of the aortic arch Signup and view all the answers

What type of blood does the pulmonary trunk carry?

Deoxygenated blood Signup and view all the answers

Which artery runs alongside and supplies organs such as the esophagus and bronchial tissue?

Descending thoracic aorta Signup and view all the answers

What structures drain into the right brachiocephalic vein?

Vertebral, first posterior intercostal, and internal thoracic veins Signup and view all the answers

What is the main function of the superior vena cava?

To drain blood from the head, neck, and upper limbs Signup and view all the answers

At what anatomical location does the superior vena cava begin?

Posterior to the lower edge of the right first costal cartilage Signup and view all the answers

Which veins drain into the left brachiocephalic vein?

Vertebral, left superior intercostal, and inferior thyroid veins Signup and view all the answers

Where does the superior vena cava enter the pericardium?

At the lower edge of the right third costal cartilage Signup and view all the answers

What is one use of large systemic veins in clinical procedures?

To deliver large volumes of fluid, drugs, and blood Signup and view all the answers

Which veins comprise the azygos venous system?

Hemiazygos, superior hemiazygos, and inferior hemiazygos veins Signup and view all the answers

What anatomical structure does the azygos vein primarily drain into?

Superior vena cava Signup and view all the answers

What is the primary developmental role of the thymus?

Development of T lymphocytes Signup and view all the answers

What happens to the thymus after puberty?

It undergoes involution Signup and view all the answers

Which arteries supply blood to the thymus?

Inferior thyroid and internal thoracic arteries Signup and view all the answers

What is the typical venous drainage for the thymus?

Left brachiocephalic vein and possibly internal thoracic veins Signup and view all the answers

Where does lymphatic drainage from the thymus return?

Tracheal bifurcation, root of the neck, and parasternal nodes Signup and view all the answers

What is a clinical correlation associated with the thymus?

Ectopic parathyroid glands Signup and view all the answers

What kind of innervation do the vagus nerves provide to the thoracic viscera?

Parasympathetic innervation Signup and view all the answers

How do visceral afferents in the vagus nerves function regarding pain sensation?

They relay information about physiological processes but do not transmit pain sensation Signup and view all the answers

What is the primary function of the right phrenic nerve as it descends in the middle mediastinum?

To innervate the diaphragm Signup and view all the answers

Where does the left phrenic nerve pierce the diaphragm?

At the apex of the heart Signup and view all the answers

Which lymph nodes receive drainage from the skin of the anterior thoracic wall?

Anterior axillary nodes Signup and view all the answers

What drains into the thoracic duct from the posterior intercostal nodes?

Lymph from the posterior parts of the intercostal spaces Signup and view all the answers

Which structure lies adjacent and slightly posterior to the left brachiocephalic vein?

Left phrenic nerve Signup and view all the answers

What is true about the intercostal nodes in the upper thorax?

They drain into bronchomediastinal trunks Signup and view all the answers

Which node group collects lymph from the deep vessels of the anterior intercostal spaces?

Internal thoracic nodes Signup and view all the answers

The diaphragmatic nodes are primarily located where?

Posterior to the xiphoid process Signup and view all the answers

Where are the connector cells of the parasympathetic system primarily located?

In the brain and sacral segments of the spinal cord Signup and view all the answers

How many ganglia are present in the thoracic part of the sympathetic trunk?

11 or 12 Signup and view all the answers

What structure does the thoracic part of the sympathetic trunk pass behind to leave the thorax?

The medial arcuate ligament Signup and view all the answers

What is the first ganglion of the thoracic sympathetic trunk often fused with?

Inferior cervical ganglion Signup and view all the answers

What is the primary function of the gray rami communicantes in the thoracic sympathetic trunk?

They distribute fibers to skin structures like sweat glands. Signup and view all the answers

Which structures receive postganglionic fibers from the first five ganglia of the thoracic sympathetic trunk?

Heart, aorta, lungs, and esophagus Signup and view all the answers

What characterizes the lower eight ganglia of the thoracic sympathetic trunk?

They give preganglionic fibers grouped as splanchnic nerves. Signup and view all the answers

Study Notes

Mediastinum

The mediastinum is a thick midline partition between the two lungs
It extends anteriorly to the sternum and posteriorly to the vertebral column
It extends from the superior thoracic aperture to the diaphragm
It contains the remains of the thymus, the heart and major blood vessels, the trachea and esophagus, the thoracic duct and lymph nodes, the vagus and phrenic nerves, and the sympathetic trunks
The mediastinum is divided into superior and inferior mediastina by an imaginary plane passing through the sternal angle, through T4 and T5
The inferior mediastinum is further divided into middle, anterior, and posterior mediastinum
The middle mediastinum contains the pericardium and heart
The anterior mediastinum is the space between the sternum and pericardium
The posterior mediastinum is the space between the pericardium and the spinal column

Superior Mediastinum

Contains the thymus, major blood vessels (superior vena cava, aortic arch, brachiocephalic veins), trachea, esophagus, thoracic duct, and sympathetic trunks.
Boundaries: anteriorly by the manubrium sterni, posteriorly by vertebrae T1-T4, superiorly by the superior thoracic aperture, inferiorly by a plane passing through the sternal angle and T4/T5

Inferior Mediastinum

Contains the heart within the pericardium, phrenic nerves on each side, esophagus and thoracic duct, descending aorta, and sympathetic trunks.
Subdivisions: anterior, middle, and posterior mediastina.

Anterior Mediastinum

Located between the sternum and pericardium.
Contains connective tissue, fat, and remnants of the thymus
Boundaries: anteriorly by the body of the sternum and the transverse thoracic muscle, posteriorly by the pericardium, superiorly by a line between the sternal angle and T4, and inferiorly by the diaphragm

Middle Mediastinum

Contains the heart and pericardial sac.
Also contains the roots of the great vessels—the ascending aorta, superior vena cava, pulmonary trunk, pulmonary veins—and the phrenic nerves.

Posterior Mediastinum

Lies between the pericardium and the vertebral column.
Contains the descending thoracic aorta, the thoracic duct, posterior intercostal vessels, azygos and hemiazygos veins, esophagus, and esophageal plexus, sympathetic trunks and splanchnic nerves.
Boundaries: anteriorly by the pericardium and the diaphragm, posteriorly by the vertebral bodies, superiorly by the level of the sternal angle and T4, and inferiorly by the diaphragm

Azygos Vein

Consists of the main azygos vein, the inferior hemiazygos, and the superior hemiazygos veins
Drains blood from the posterior parts of the intercostal spaces, posterior abdominal wall, pericardium, diaphragm and esophagus.
Azygos vein forms at the level of the right side of the L1 and L2 vertebrae.

Superior Hemiazygos Vein

Fornmed by the union of the fourth to eighth intercostal veins and occasionally left bronchial veins
It joins the azygos vein at the level of the seventh or eighth thoracic vertebrae.
Often connected to the left superior intercostal vein.

Inferior Hemiazygos Vein

Usually formed by the union of the left ascending lumbar vein and left subcostal vein, but may arise from either vein alone.
Ascends the left side of the thoracic cavity, turning posterior to the thoracic duct, aorta and esophageal.

Thoracic Aorta

The descending thoracic aorta is a continuation of the aortic arch that extends down the posterior thoracic cavity
It provides branches for the posterior intercostal spaces, subcoastal spaces, and pericardial, esophageal, and broncial arteries.

Pulmonary Trunk

Carries deoxygenated blood from the right ventricle of the heart into the lungs
It is roughly 2 inches in length and descends to the left. It is divided into the right and left pulmonary artery
Enclosed in the fibrous pericardium, together with the ascending aorta

The Autonomic Nervous System

The autonomic nervous system is responsible for controlling involuntary bodily functions such as heart rate, blood pressure, digestion, and pupil dilation
Divided into two parts: sympathetic and parasympathetic, both with afferent and efferent nerve fibers
The sympathetic division prepares the body for stress or emergency, resulting in increased heart rate and blood pressure, while the parasympathetic division promotes rest and digestion

Phrenic Nerves

Originate in the cervical spine, typically C3-C5.
Descend into the thorax, passing lateral to the vagus nerve and posterior to the origin of the brachiocephalic vein
Provide motor innervation to the diaphragm and sensory innervation to the diaphragm, pericardium, and pleura

Clinical Correlation

Several types of diseases can occur in the thoracic cavity and its structures. Understanding the structures and their function is crucial for diagnosis and treatment

Lymphatic Drainage of the Esophagus

The lymphatic vessels in the superior third of the esophagus drain to the deep cervical lymph nodes
The vessels in the middle third drain to superior and posterior mediastinal lymph nodes
Vessels in the inferior third drain to lymph nodes surrounding the left gastric vessels and the celiac nodes

Lymph Nodes and Vessels of the Thorax

The lymph vessels from the superficial regions of the anterior thoracic wall drain into superior axillary lymph nodes
The lymph vessels from the superficial regions of the posterior thoracic wall drain into posterior axillary lymph nodes

Right Lymphatic Duct

Collects lymph from the right side of the head, neck, right upper limb, and right side of the thorax
Enters the right brachiocephalic vein

Thoracic Duct

Collects lymph from the majority of the body below the diaphragm, left side of the thorax, and the left upper limb
Enters the left brachiocephalic vein

Thymus

Located in the superior mediastinum, posterior to the sternum and anterior to the pericardium
Develops and grows until puberty, then undergoes involution

Esophagus

A muscular tube begins at the level of the cricoid cartilage(C6) at the end of the pharynx and ends at the cardiac orifice of the stomach at the level of the 10th thoracic vertebra reaching the level of T11
It’s the narrowest part of the GIT after the pylorus and appendix

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Description

Test your knowledge on the structures and boundaries of the mediastinum, including anterior, middle, and posterior components. This quiz covers arteries, veins, and lymph nodes associated with the mediastinum. Perfect for students studying human anatomy and physiology.