Thoracic inlet and superior mediastinum Flashcards
What are the borders of the thoracic inlet?
- Anterior: Manubrium
- Lateral: 1st rib and costal cartilage
- Posterior: 1st thoracic vertebrae
Why is the 1st rib atypical?
- Head articulates with body and transverse process 1st thoracic vertebrae only.
- 1st chondrosternal joint is immobile primary cartilaginous joint.
What are the structures that pass through the thoracic inlet?
Arteries: - Left/right subclavian artery - Left/right common carotid artery Veins: - Left/right subclavian vein - Left/right internal jugular vein - Left/right brachiocephalic vein Nerves: - Phrenic nerves - Vagus nerves - Recurrent laryngeal nerves - Sympathetic trunks Other structures: - Apex of the lungs - Trachea - Oesophagus - Thoracic duct
What are the boundaries of the superior mediastinum?
- Superior: Thoracic inlet
- Inferior: Plane crossing through the manubriosternal joint and T4/T5 intervertebral disc
What are the origins of the brachiocephalic veins?
- Behind the sternoclavicular joint
- Convergence of the subclavian and internal jugular veins
What is the origin of the SVC?
- Behind lower border of right 1st costal cartilage
- Convergence of the brachiocephalic veins
What is the relationship between the brachiocephalic veins?
The left brachiocephalic vein is longer than the right.
What are the relationships of vessels at the thoracic inlet?
- The subclavian veins lie anterior to the subclavian arteries.
- Scalene anterior lies between the 2 vessels.
- The common carotid arteries lie medial to the internal jugular veins.
What are the veins of the superior mediastinum?
- Left/right brachiocephalic vein
- Superior vena cava
- Superior intercostal veins
Where does the azygos vein join the SVC?
Level of T4 vertebrae
What are the branches of the aortic arch?
- Brachiocephalic trunk
- Left common carotid artery
- Left subclavian vein
What are the boundaries of the aortic arch?
- Beginning/end: T4/T5 level.
- Superior-most extent: T3/T4 level.
What is the ligamentum arteriosum and its attachments?
- The ligamentum arteriosum is the remnants of the ductus arteriosus.
- It is attached to the ishmus of the aortic arch (last section of the arch, where origin of left subclavian artery is), and the pulmonary trunk.
Where is the bifurcation of the brachiocephalic trunk?
Upper border of sternoclavicular joint
What are the branches of the subclavian artery?
- Vertebral artery
- Internal thoracic artery
- Thyrocervical trunk
- Costocervical trunk
What are the relations of the vertebral artery?
- Enters the transverse foraman of C6 vertebrae.
- Ascends up the spinal cord, sending branches to the vertebrae and spinal cord.
- It joins with other vertebral artery to form the basilar artery supplying cerebellum and occipital lobe.
What are the relations of the internal thoracic artery?
- Descends on the internal thoracic wall lateral to the sternum.
- Gives rise to anterior intercostal arteries.
What are the terminal branches of the internal thoracic artery?
- Musculophrenic artery
- Superior epigastric artery
What are the branches of the thyrocervical trunk?
- Inferior thyroid artery
- Ascending cervical artery
- Suprascapular artery
- Transverse cervical artery
What are the branches of the costocervical trunk?
- Posterior intercostal artery: Supplies posterior intercostal arteries to upper 2 intercostal spaces.
- Deep cervical artery: Supplies deep structures of the neck.
What are the terminal branches of the external carotid artery?
- Superficial temporal artery
- Maxillary artery
What are the 2 lymphatic vessels in the thorax?
- Right lymphatic trunk
- Thoracic duct
Where does the thoracic duct drain?
Junction of the left internal jugular and subclavian veins.
What are the relations of the nerves at the thoracic inlet?
- All nerves lie anterior to the subclavian arteries and posterior to the subclavian veins.
- The phrenic nerves lies lateral to the vagus nerves.
What are the relations of the phrenic nerves?
- The right phrenic nerve descends to the right of the SVC, anterior to the right bronchus and on the fibrous pericardium overlying the right atrium.
- The left phrenic nerve descends anterior to the apex of the lungs and the left bronchus, then on the fibrous pericardium overlying the left ventricle.
What are the relationships of the vagus nerves?
- The right vagus nerve descends posterior to the right bronchus and forms the anterior vagal trunk of the oesophageal plexus.
- The left vagus nerve descends posterior to the left bronchus and forms the posterior vagal trunk of the oesophageal plexus.
What are the relationships of the recurrent laryngeal nerves?
- The right recurrent laryngeal nerve originates from the right vagus nerve just inferior to the bifurcation of the brachiocephalic trunk.
- The left recurrent laryngeal nerve originates from the left vagus nerve at the level of the aortic arch and winds around to posterior aspects of the aortic arch.
- Both recurrent laryngeal nerves ascend in the tracheo-oesophageal groove.
What is the function of the recurrent laryngeal nerves?
Innervates all the intrinsic muscles of the larynx (involved with swallowing), except the cricothyroid muscles.
