The term Great Vessels describes a collection of large-caliber arteries and veins found in the thoracic cavity.<\/div><\/p>\n\n\n\n
List<\/h4>\n<\/span>\n\n\n
The brachiocephalic veins<\/li>
Superior vena cava<\/li>
Pulmonary trunk<\/li>
Aorta<\/li>
The brachiocephalic trunk<\/li>
Left common carotid artery<\/li>
Left subclavian artery<\/li><\/ol>\n\n\n<\/span>\n
Brachiocephalic veins<\/h4>\n<\/span>\n\n\n
Also known as the\u00a0innominate veins<\/strong>, the brachiocephalic veins form by the union of the subclavian and the internal jugular veins. The two vessels join to the superior vena cava (see below).<\/p>\n\n\n\n
Compared to the right brachiocephalic vein, the left brachiocephalic vein is longer, as it has to cross the mediastinum from left to right.<\/p>\n\n\n<\/span>\n
Superior vena cava<\/h4>\n<\/span>\n\n\n
The\u00a0superior vena cava<\/strong> (SVC)\u00a0is formed by the union of the brachiocephalic veins, and terminates at the superior pole of the right atrium. <\/p>\n\n\n\n
The superior vena cava drains blood from all structures above the diaphragm except the lungs and heart.<\/li>
Approximately 6cm in length, it forms at the level of the\u00a01st right rib<\/strong>, and terminates at the right atrium at the level of the 3rd costal cartilage<\/strong>. It is found anterolateral to the trachea and posterolateral to the ascending aorta.<\/li>
The terminal part of the SVC is located within the middle mediastinum, where it resides adjacent to the ascending aorta and forms the posterior border of the transverse pericardial sinus located within the\u00a0pericardium.<\/li>
The azygos vein joins the superior vena cava\u00a0posterior to the right 2nd costal cartilage<\/strong><\/li><\/ul>\n\n\n<\/span>\n
Pulmonary trunk<\/h4>\n<\/span>\n\n\n
The pulmonary trunk arises from the right ventricle, carrying deoxygenated blood to the lungs.<\/p>\n\n\n\n
Divides into the right and left pulmonary arteries at the level of the sternal angle<\/li>
Its size isapproximately 5 cm long and 3 cm wide<\/li>
The only artery in our body which transports deoxygenated blood<\/li>
For more information about the pulmonary vessels and circulation, head over to the lungs lesson<\/li><\/ul>\n\n\n
\nFigure 1. The venous system of the thoracic cavity<\/strong> (Credit: OpenStax, CC BY-SA 4.0)<\/figcaption><\/figure>\n<\/div>\n\n<\/span>\n
Aorta<\/h3>\n<\/span>\n\n\n
The aorta is the largest artery of the human body. It arises from the left ventricle and supplies the whole body with oxygenated blood.<\/p>\n\n\n<\/span>\n
Ascending Aorta<\/h4>\n<\/span>\n\n\n
The ascending aorta is the first segment of the aorta before it exits the pericardium<\/li>
Its only branches are the right<\/strong> and left coronary arteries,<\/strong> arising from the aortic sinuses<\/li>
It begins at the sternal end of the left 3rd intercostal space, moves upward and to the right behind the sternum<\/li>
It ends at the right side of the inferior part of the sternal angle at the level of 2nd intercostal space<\/li>
The ascending aorta is considered as an intrapericardial component<\/strong>, which means that it is contained within the middle mediastinum.<\/li><\/ul>\n\n\n<\/span>\n
Arch of the aorta<\/h4>\n<\/span>\n\n\n
The arch of the aorta begins posterior to the 2nd right sternocostal joint. From there, it runs inferiorly and continues as the descending aorta<\/strong><\/li>
The arch begins anteriorly to both the right pulmonary artery and the bifurcation of the trachea<\/li>
The uppermost part (apex) of the arch<\/strong> is located at the left side of the trachea and the esophagus as it passes over the left main bronchus<\/li>
Surface projection:<\/strong>
Arches posterior to the sternal angle<\/li>
The top part does not reach the 1st ribs<\/li>
Become the descending aorta as it reaches the vertebral column at the level of T4, left side of the midline<\/li><\/ul><\/li>
The ligamentum arteriosum:<\/strong>
The ligamentum arteriosum is an embryology remnant located at the descending part of the arch of the aorta<\/li>
During the intrauterine life, it functions as the ductus arteriosus<\/strong>, which is a blood vessel that connects the pulmonary trunk to the proximal descending aorta, acting as a shunt<\/li>
The ductus arteriosus<\/strong> allows most of the blood from the right ventricle to bypass the non-functioning lungs of the fetus since oxygenation occurs in the placenta and not in the lungs, which are collapsed until birth<\/li>
It closes within three weeks after birth and forms the ligament<\/li><\/ul><\/li><\/ul>\n\n\n\nFigure 2. The ductus arteriosus and foramen ovale before and after birth<\/strong> (Credit: OpenStax, CC BY-SA 4.0)<\/figcaption><\/figure>\n\n\n<\/span>\n
Descending aorta<\/h4>\n<\/span>\n\n\n
Begins at the level of T4<\/li>
Continues as the abdominal aorta at L4<\/li>
In order to find its surface projection we should draw an imaginary line between the sternal end of the 2nd left rib (left edge of the sternal angle) until we reach a point which is located on the left from the intersection of the midsagittal and supracristal planes<\/strong> (anatomical transverse plane lying at the upper most part of the pelvis, the iliac crest)<\/li><\/ul>\n\n\n<\/span>\n
Exam tip<\/h4>\n<\/span>\n\n\n
Sometimes, examiners ask about the branches of the ascending aorta (or to name the first branch of the aorta). Pay attention to their question, because the first branch(es) are the right and left coronary arteries (which are also the branches of the ascending aorta, as mentioned above). Unwary students will answer \u201cbrachiocephalic trunk\u201d, which is a branch of the arch, and not the ascending aorta.<\/p>\n\n\n<\/span>\n
Brachiocephalic trunk<\/h3>\n<\/span>\n\n\n
The first and largest branch of the arch of the aorta <\/strong>\u2014 arises at the highest point of the aortic arch left to the midsagittal plane.<\/p>\n\n\n<\/span>\n
Surface projections<\/h4>\n<\/span>\n\n\n
An oblique line needs to be drawn between the highest point of the aortic arch (located left to the midsagittal plane) and the right sternoclavicular joint \u2014 there, the brachiocephalic trunk gives rise to its two branches (the right common carotid, and the right subclavian arteries)<\/li>
Its branching point<\/strong> is located behind the manubrium of the sternum<\/strong>, between the trachea (anterior to it) and left brachiocephalic vein<\/li>
The brachiocephalic trunk divides into the right common carotid artery<\/strong> and the right subclavian<\/strong> on the right side of the trachea.<\/li><\/ul>\n\n\n<\/span>\n
Left common carotid artery (LCCA)<\/h3>\n<\/span>\n\n\n
The second branch of the arch of the aorta<\/strong>, arising behind the manubrium \u2014 similarly to the brachiocephalic trunk<\/li>
At first, the LCCA starts posterior and to the left of the brachiocephalic trunk, and then it runs superiorly anterior to the left subclavian artery; from there, anteriorly to the trachea, and before entering to the neck, continue to the left of the trachea<\/li>
Surface projection:<\/strong>
An imaginary line needs to be drawn which connecting the point of origin and the left sternoclavicular joint<\/li><\/ul><\/li><\/ul>\n\n\n<\/span>\n
Left subclavian artery (LSCA)<\/h3>\n<\/span>\n\n\n
The third branch of the arch of the aorta<\/strong><\/li>
Arising from the posterior part of the arc<\/li>
Initially, the LSCA ascends laterally to both the trachea and the LCCA<\/li>
The left subclavian does not branch inside the mediastinum, but rather after it exits the thoracic cavity and enters the neck<\/li><\/ul>\n\n\n
\nFigure 3. The great vessels of the superior mediastinum<\/strong> (Credit: Anatomist90, CC BY-SA 4.0)<\/figcaption><\/figure>\n<\/div>\n\n
\nFigure 4. The arch of the aorta and its branches<\/strong> (Credit: OpenStax, CC BY-SA 4.0)<\/figcaption><\/figure>\n<\/div>\n\n<\/span>\n
Thoracic aorta<\/h3>\n<\/span>\n\n\n
The thoracic aorta <\/strong>is the continuation of the arch of the aorta, located within the posterior mediastinum.<\/p>\n\n\n\n
Begins on the\u00a0left side\u00a0<\/strong>on the level of the 4th lumbar vertebra\u00a0and continues inferiorly within the posterior mediastinum on the left side of T5\u2013T12 vertebrae<\/li>
The thoracic aorta pushes the esophagus to the right when it reaches the median line and continues posteriorly to the esophagus, the root of the left lung and the pericardium<\/li>
At the level of T12, it becomes the\u00a0abdominal aorta<\/strong>\u00a0once it enters the abdominal cavity through the\u00a0aortic hiatus\u00a0<\/strong>in the diaphragm, along with the thoracic duct and the azygos vein at its right side<\/li>
The\u00a0thoracic aortic plexus<\/strong>, an autonomic sympathetic nerve network, surround it within the thoracic region<\/li><\/ul>\n\n\n<\/span>\n
Branches<\/h4>\n<\/span>\n\n\n
The branches of the descending aorta arise and continue within three vascular planes:<\/p>\n\n\n\n
They supply the gut and the associated structures within the upper abdominal cavity<\/li><\/ul><\/li>
Lateral<\/strong> plane<\/strong> \u2014 Paired visceral branches \u2014 the bronchial arteries<\/strong>
Most commonly, only the paired left bronchial arteries arise from the aorta while the right bronchial arteries arise indirectly as branches of a right posterior intercostal artery usually the 3rd posterior intercostal artery<\/li><\/ul><\/li>
The subcostal arteries<\/strong> arise from the thoracic aorta at the posterolateral plane as the posterior intercostal arteries, but descend below the diaphragm.<\/li><\/ul><\/li><\/ol>\n\n\n\n
Exceptions for the pattern above:<\/p>\n\n\n\n
Superior phrenic arteries<\/strong>:
Paired parietal branches which are being distributed to the posterior part of the upper surface of the diaphragm and not to the body wall<\/li>
Anastomose with the musculophrenic and pericardiacophrenic branches of the internal thoracic artery<\/li><\/ul><\/li>
Pericardial branches:<\/strong>
Unpaired branches that arise anteriorly<\/li>
Instead of passing to the gut or supply the esophagus, they supply the pericardium.<\/li><\/ul><\/li><\/ol>\n\n\n
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