Superior Vena Cava, Aorta, Pulmonary Trunk, Thoracic Duct, Azygos and Hemiazygos Veins, and Thoracic Sympathetic Trunks Flashcards
Outline the relational anatomy of the aortic arch.
[Study relational anatomy with an atlas!]
Posterior and to the right:
1. Trachea
2. Esophagus
3. Left recurrent laryngeal nerve
4. Thoracic duct
5. Vertebral column
Anterior and to the left:
1. Left lung and pleura
2. Left phrenic nerve
3. Left vagus nerve
4. Left cardiac nerves (i.e., superior cervical cardiac branch of left sympathetic chain and inferior cardiac branch of left vagus nerve)
5. Left superior intercostal vein
Inferior:
1. Left bronchus
2. Bifurcation of pulmonary trunk
3. Ligamentum arteriosum
4. Left recurrent laryngeal nerve
5. Superficial cardiac plexus
Superior:
1. Brachiocephalic trunk
2. Left common carotid artery
3. Left subclavian artery
4. Left brachiocephalic vein
5. Thymus
a) The ascending aorta arises from the upper end of the left ventricle (i.e. aortic vestibule) and continues as arch of aorta at the _______________________.
b) State the branches of the ascending aorta. These branches are given off at the root of aorta which have aortic sinuses of Valsalva.
a) sternal angle
b) right coronary artery from right aortic or anterior aortic sinus
left coronary artery from left aortic or left posterior aortic sinus
Note: The ascending aorta develops from the truncus arteriosus after its partition by the spiral septum.
State the branches of the arch of aorta.
- Brachiocephalic (innominate) artery.
- Left common carotid artery.
- Left subclavian artery.
Notes:
㊨ Occasionally a fourth branch called thyroidea ima artery may arise from the arch of aorta.
㊨ The arch of aorta arches over the root of left lung.
㊨ The arch of aorta develops from the following sources:
1. Aortic sac.
2. Left horn of aortic sac.
3. Left fourth aortic arch artery.
4. Left dorsal aorta (between the attachment of the fourth aortic arch (artery) and 7th cervical intersegmental artery.
The descending aorta is the continuation of the arch of the aorta in the posterior mediastinum. It is divided into descending thoracic aorta and abdominal aorta.
Describe the course of the descending thoracic aorta.
It begins on the left side of the lower border of the fourth thoracic (T4) vertebra and descends in the posterior mediastinum with an inclination towards the right. As a result it terminates in front of the lower border of the body of 12th thoracic (T12) vertebra.
At its lower end it passes through the aortic opening of the diaphragm to continue as the abdominal aorta.
㊨ Note that the descending thoracic aorta produces a deep vertical groove on the mediastinal surface of the lung posterior to the hilum of the lung.
State the branches of the descending thoracic aorta.
Parietal branches:
㊨ 3rd to 11th posterior intercostal arteries on each side.
㊨ subcostal artery on each side
㊨ superior phrenic artery on each side
Visceral branches:
㊨ pericardial branches to posterior surface of the pericardium
㊨ mediastinal branches to the lymph nodes and areolar tissue of the posterior mediastinum
㊨ two left bronchial arteries (upper and lower)
㊨ esophageal branches, supplying middle one-third of the esophagus
Discuss the formation, course and termination of the superior vena cava.
☛ formed at the lower border of the right 1st costal cartilage by the union of right and left brachiocephalic (innominate) veins
☛ It passes vertically downwards behind the right border of the sternum and pierces the pericardium at the level of the 2nd costal cartilage and terminates into the upper part of the right atrium at the lower border of the right 3rd costal cartilage
Note:
㊨ The SVC has no valves in its lumen because gravity facilitates the blood flow in it.
State the subdivisions of the superior vena cava.
㊨ Extrapericardial part (in superior mediastinum).
㊨ Intrapericardial part (in middle mediastinum).
State the tributaries of the superior vena cava.
㊨ Right and left brachiocephalic veins.
㊨ Azygos vein, which arches over the root of the right lung and opens into SVC just before it pierces fibrous pericardium.
㊨ Mediastinal and pericardial veins.
There are two brachiocephalic veins: right and left. What forms these veins?
Internal jugular and subclavian veins.
㊨ Note that these brachiocephalic veins are devoid of valves.
State the differences between the right and left brachiocephalic veins in terms of length and course.
㊨ The right brachiocephalic vein is shorter than the left brachiocephalic vein.
㊨ The course of the right brachiocephalic vein is vertical while that of the left brachiocephalic vein is oblique.
State the tributaries of the right brachiocephalic vein.
㊨ Right vertebral vein
㊨ Right internal thoracic vein
㊨ Right inferior thyroid vein
㊨ First right posterior intercostal vein
State the tributaries of the left brachiocephalic vein.
㊨ Left vertebral vein
㊨ Left internal thoracic vein
㊨ Left inferior thyroid vein
㊨ First left posterior intercostal vein
㊨ Left superior intercostal vein
The SVC may be obstructed (compressed) at two sites: (a) above the opening of azygos vein (i.e., in superior mediastinum), and (b) below the opening of azygos vein (i.e., in the middle mediastinum). In such cases, collateral pathways may develop. Check out the following images to show this.
[1]
State the origin and course of the pulmonary trunk.
Origin
The pulmonary trunk is about 5 cm long and arises from the upper part (infundibulum/conus arteriosus) of the right ventricle at the level of the sternal end of left 3rd costal cartilage.
Course
After arising from infundibulum in the middle mediastinum, it passes backwards and to the left and terminates below the arch of aorta and in front of left principal bronchus by dividing into right and left pulmonary arteries.
Note:
㊨ The right pulmonary artery is larger than the left and lies slightly at a lower level.