Thoracic Anatomy: Mediastinum, Great Vessels, and Cardiac Structures

Comprehensive vocabulary flashcards reviewing the anatomical structures, boundaries, vessels, nerves, and internal features of the mediastinum and heart.

Mediastinum

The central compartment of the thoracic cavity, defined as the space located between the two pleural sacs.

Superior Mediastinum

The division of the mediastinum located above the level of $T4\text{--}T5$ (sternal angle), containing the thymus, aortic arch, brachiocephalic veins, superior vena cava (SVC), trachea, esophagus, vagus and phrenic nerves, and thoracic duct.

Anterior Mediastinum

A small subdivision of the inferior mediastinum situated between the sternum and the pericardium that contains the thymus in children.

Middle Mediastinum

The subdivision of the inferior mediastinum containing the heart, pericardium, and the roots of the great vessels.

Posterior Mediastinum

The subdivision of the inferior mediastinum located between the pericardium and vertebral bodies, containing the descending aorta, esophagus, thoracic duct, and azygos system.

Thoracic Aorta

The continuation of the arch of the aorta that begins at the inferior border of $T4$, descends to the left of $T5\text{--}T12$, and exits the thorax by passing through the aortic hiatus at $T12$.

Azygos Vein

A venous channel that ascends on the right side from $T12$ to $T4$, connecting the superior and inferior venae cavae and draining the posterior thoracic and abdominal walls.

Hemiazygos Vein

A vein that ascends on the left side from $T12$ to $T9$ and crosses over to join the azygos vein near $T9$.

Accessory Hemiazygos Vein

A vein that descends on the left side from $T5$ to $T8$ and joins the azygos vein at the level of $T7/T8$.

Trachea

A fibrocartilaginous tube with C-shaped rings lying anterior to the esophagus, extending from $C6$ to $T4$ where it bifurcates at the carina near the sternal angle ($T4/T5$).

Esophagus

A muscular tube extending from $C6$ to $T9$ within the thorax before passing through the diaphragm via the esophageal hiatus at $T10$.

Esophageal Constrictions

The three anatomical narrowings of the esophagus caused by the arch of aorta, left primary bronchus, and esophageal hiatus.

Thoracic Duct

The major lymphatic trunk ascending between the thoracic aorta and azygos vein from $T5$ to $T12$, draining lymph from both lower extremities, the lower abdomen, left thorax, left head/neck, and left upper limb into the left brachiocephalic vein.

Cisterna Chyli

The dilated sac located anterior to $T12$ that marks the inferior origin of the thoracic duct.

Phrenic Nerve

Nerves arising from spinal segments $C3$, $C4$, and $C5$ that provide the sole motor supply to the diaphragm along with roughly one-third of its sensory innervation.

Pericardium

The fibroserous membrane enclosing the heart, consisting of an outer fibrous layer and an inner serous layer that is further divided into parietal and visceral layers.

Epicardium

The external protective layer of the heart wall, corresponding to the visceral layer of the serous pericardium.

Myocardium

The thick, middle muscular layer of the heart wall responsible for cardiac contraction.

Endocardium

The smooth, innermost endothelial lining of the heart chambers and valves.

Base of the Heart

The posterior cardiac surface, formed mainly by the left atrium receiving the pulmonary veins, facing toward the vertebral column.

Apex of the Heart

The inferolateral tip of the heart, formed by the left ventricle, pointing downward and leftward to the 5th intercostal space at the midclavicular line.

Coronary Sulcus (Atrioventricular Groove)

A surface groove separating the atria from the ventricles; it transmits the right coronary artery, circumflex artery, and coronary sinus.

Anterior Interventricular Sulcus

A groove on the anterior surface of the heart separating the ventricles, containing the anterior interventricular artery (LAD) and great cardiac vein.

Posterior Interventricular Sulcus

A groove located on the diaphragmatic surface of the heart containing the posterior interventricular artery and middle cardiac vein.

Coronary Sinus

The large venous channel that collects deoxygenated blood from the cardiac veins and empties directly into the right atrium.

Great Cardiac Vein

A cardiac vein that ascends within the anterior interventricular sulcus alongside the LAD artery before draining into the coronary sinus.

Middle Cardiac Vein

A cardiac vein running within the posterior interventricular sulcus alongside the posterior interventricular artery.

Small Cardiac Vein

A vein running along the right lower margin of the heart together with the marginal artery.

Anterior Cardiac Veins

Small veins on the anterior surface of the right ventricle that drain directly into the right atrium rather than entering the coronary sinus.

Crista Terminalis

An internal vertical muscular ridge separating the smooth posterior wall (sinus venarum) from the rough anterior pectinate wall of the right atrium.

Fossa Ovalis

An oval depression on the interatrial septum representing the remnant of the fetal foramen ovale.

Trabeculae Carneae

Muscular ridges and columns projecting from the inner myocardial wall of the ventricles.

Moderator Band (Septomarginal Trabecula)

A prominent muscular band in the right ventricle that transmits specialized conduction fibers from the interventricular septum to the anterior papillary muscle.

Conus Arteriosus (Infundibulum)

The smooth-walled, conical outflow tract of the right ventricle leading upward into the pulmonary trunk.