1.3 - The Mediastinum Flashcards
What are the main contents of the mediastinum?
Trachea, Oesophagus, Aorta, Superior Vena Cava, Heart, pericardium, thoracic duct, nerves
What are the different divisions of the mediastinum?
Superior (above sternal angle), Inferior (below the sternal angle)
Inferior is divided into anterior, middle and posterior
Describe the arrangement of the vagus nerve and phrenic nerve in the mediastinum.
Vagus nerve runs posterior to the airways
Phrenic runs anterior to the airways and is embedded in the pericardium
What vertebral level do the phrenic nerves emerge from?
C3, C4, C5
What is the name of the connection between the pulmonary artery and the aorta? What is this a remnant of?
Ligamentum Arteriosum - remnant of the ductus arteriosus
Where does the vagus nerve go through the diaphragm?
T10 - along with the oesophagus
Describe the position and orientation of the azygous vein.
The azygous vein runs along the right side of the vertebral bodies and arches anteriorly over the right main bronchus to join the SVC.
What are the three main branches of the aortic arch?
Brachiocephalic trunk, left common carotid, left subclavian
Describe the arrangement of the veins that drain into the superior vena cava.
Right and Left brachiocephalic veins join together to form the SVC
Each brachiocephalic vein is made up of an internal jugular vein and a subclavian vein
What is the nerve that branches off the vagus in the mediastinum near the left lung?
Left recurrent laryngeal nerve?
What part of the diaphragm and at which vertebral level does the IVC go through the diaphragm?
T8
Where do the right and left coronary arteries arise?
Ascending Aorta - from just above the cusps of the aortic valve
Describe the position of the ascending and descending aorta in relation to the airways.
Ascending aorta is anterior to the airways and the arch loops around the left main bronchus posteriorly and the descending aorta is posterior to the left main bronchus.
What vertebral levels do the IVC, oesophagus and aorta go through the diaphragm?
8, 10 and 12
Other than the internal and external carotid arteries, what other arteries supply the head and neck?
Vertebral arteries from the subclavian arteries
Where does the oesophagus begin and end?
C7 to T11
What happens to the oesophagus at T7?
The oesophagus is to the right of the aorta above T7
Beyond T7 the oesophagus starts moving towards the left
The oesophagus also starts to bend more anteriorly
How many constrictions does the oesophagus have?
4
Where are the four constrictions of the oesophagus?
The junction between the pharynx and the oesophagus
Where the oesophagus is crossed by the arch of the aorta
Where the oesophagus is compressed by the left main bronchus
At the oesophageal hiatus
Describe the azygos venous system.
The azygos vein runs along the right side of the vertebral bodies and drains the right side of the chest wall. The accessory hemiazygos (superior to the hemiazygos) and the hemiazygos drain the left side of the chest wall and drain into the azygos. The azygos then arches anteriorly over the lung root and joins the superior vena cava.
Describe the relations of the azygos vein.
Azygos vein arches anteriorly over the lung root to join the superior vena cava.
What structures do the phrenic nerves provide sensory and motor innervation to?
Motor - diaphragm
Sensory - central tendon of diaphragm, mediastinal pleura, pericardium, peritoneum of central diaphragm
Describe the path of the right phrenic nerve to reach the diaphragm
The right phrenic nerve passes along the right brachiocephalic vein, along the superior vena cava, and along the right side of the heart and pericardium to the diaphragm.
Describe the relations of the vagus nerves to the great arteries.
The vagus nerves run lateral to the two common carotid arteries.
Describe the paths of the left vagus and left phrenic nerves.
The left vagus crosses anteriorly to the aortic arch. The left phrenic nerve crosses more anteriorly in front of the aortic arch.
Describe the path of the left recurrent laryngeal nerve.
The left recurrent laryngeal nerve is a branch of the left vagus nerve, which arches around the ligamentum arteriosum and moves up towards the larynx.
Describe the path of the right recurrent laryngeal nerve.
The right recurrent laryngeal nerve branches off the right vagus nerve more superiorly and loops around the right subclavian artery.
What structure does the right vagus nerve lie on?
Trachea
What are the main branches of the vagus nerve?
Parasympathetic to the heart and lungs (control of smooth and cardiac muscle + glands of gut and airways)
Large sensory from the gut
Recurrent laryngeal nerve is NOT parasympathetic - it runs up the neck to supply most skeletal muscles of the larynx
Which spinal nerves do the sympathetic trunk receive branches from?
T1-L2
Where do the nerves to the body wall synapse?
In the sympathetic ganglia (Sympathetic trunk brings pain fibres to the CNS from the viscera )
Where do the nerves to the internal organs synapse?
In the local ganglia.
What are the fibres in the lower sympathetic trunk called and which vertebral levels do they branch off at?
T5-T12 (Splanchnic nerves)
Describe the arrangement of the thoracic duct.
The thoracic duct begins as the cisterna chyli (L2) below the diaphragm just to the right of the aorta (between aorta and oesophagus).
The thoracic duct then crosses to the left side between T4-T7.
The thoracic duct drains into the left brachiocephalic vein.
What are the borders of the heart?
3rd CC - 1cm from sternal border
6th CC - 1cm from sternal border
2nd ICS/2nd CC - 2.5cm from sternal border
5th ICS to apex beat at MC line
