T1 L4: Posterior Mediastinum Flashcards
What is the anterior border of the posterior mediastinum?
Posterior pericardium
What is the posterior border of the posterior mediastinum?
Vertebrae T5-T12
What is the lateral border of the posterior mediastinum?
Mediastinal pleura
What is the superior border of the posterior mediastinum?
The transverse thoracic plane (T4/5)
What is the inferior border of the posterior mediastinum?
The diaphragm
Name some structures within the posterior mediastinum
Oesophagus, Thoracic aorta, azygous system of veins, Thoracic duct, Vagus nerve, sympathetic trunk, Splanchnic nerves
Which vertebrae contribute to the nervous chain?
T1-L2
Which vertebrae contribute to the thoracolumbar outflow of nerves?
T1-L2
Which vertebrae contribute to the craniosacral outflow of nerves?
Some cranial nerves (like the vagus nerve) and S2,S3 and S4
What type of autonomic nerve has a long pre-ganglionic bit?
Parasympathetic. Sympathetic synapse once they reach the plexus or organ
What is the sympathetic trunk?
A vertical chain of sympathetic nerves along both sides of the length of the vertebral column
How many sympathetic ganglion are there per a thoracic spinal level?
1
All thoracic viscera receive sympathetic supply from which vertebral levels?
T1-T4/5
Through which rami do preganglionic sympathetic fibres leave the sympathetic trunk?
Through the white rami communicantes
What is the white rami communicantes?
It anteriorly connects the spinal nerve to the sympathetic trunk and contains pre-ganglionic fibres of the sympathetic system
What is the grey rami communicantes?
Exist at every level of the spinal cord and contain postganglionic nerve fibres of the sympathetic nervous system
How do postganglionic sympathetic fibres leave the sympathetic chain?
Through the grey rami communicantes
What does efferent mean?
Away
What are somatic nerves?
Ones that don’t synapse. They’re part of the reflex arc
What is the difference between grey and white matter?
Grey matter contains the cell bodies, dendrites and the axon terminals. The white matter is made up of axons, which connect different parts of grey matter to each other
Describe the path of an afferent sensory nerve
They enter through the ventral rami and then travel through the dorsal root ganglia and don’t synapse
What does dorsal mean?
Back
What does ventral mean?
Front
Describe the pathway of a T1-T4/5 sympathetic nerve
They travel from the lateral grey horn, through the white rami communicantes and synapse in the sympathetic chain. They leave through the grey rami communicantes towards the ventral rami
What is a dermatome?
An area supplied by a single spinal level or spinal nerve
Where can pain from the heart be felt?
Down the arm or across chest
Referred pain from the diaphragm can be felt where?
At the shoulder
Where does the phrenic nerve originate?
C3, C4 and C5
Describe how dermatomes are arranged
Like we still walked on all 4’s
Describe the pathway of splanchnic nerves through the sympathetic trunk
Travel from the spinal cord and through the white rami communicantes but don’t synapse. They just leave
Where do greater splanchnic nerves originate?
T5-T9
Where do lesser splanchnic nerves originate?
T10 and T11
Where do least splanchnic nerves originate?
T12
What type of information do splanchinic nerves carry?
Preganglionic sympathetic fibres to viscera and visceral afferent fibres from abdominal viscera
At what level do nerves on the spine all become splanchnic?
Below T4/5
How does the vagus nerve enter the superior medistinum?
Posterior to the sternoclavicular joint
What type of autonomic nervous impulses does the vagus nerve carry?
Parasympathetic
Where does the vagus nerve synapse?
At the target plexus
Where does the right recurrent laryngeal branch of the vagus nerve hook under?
Under the right subclavian artery
Between what structures does the right recurrent laryngeal branch of the vagus nerve ascend?
The trachea and oesophagus
What is the position of the right vagus nerve compared to the hilum of the right lung?
Posterior to the right hilum
How does the vagus nerve continue down the thorax?
Posterior to the trachea, posterior to the brachiocephalic vein and posterior to the hilum (Similar in the left and right)
Where does the left recurrent laryngeal branch of the vagus nerve hook?
Under the arch of the aorta, immediately lateral to the ligamentum arteriosum
Along which vertabrae does the aorta descend?
T5-T12
Where is the oesophagus compared to the thoracic aorta?
To the right of the thoracic aorta
Where does the thoracic aorta terminate?
At T12, where it passes through the diaphragm
Where do the thoracic ducts and azygous veins ascend compared to the thoracic aorta?
To the right of the thoracic aorta
What are the 4 paired branches of the thoracic aorta?
Posterior intercostals, subcostal (under rib 12), bronchial, and superior phrenic
Where does the bronchial paired branch of the thoracic aorta branch?
Off the 3rd intercostal artery on the right. The left is supplied directly by the aorta
What does the superior phrenic branch of the thoracic aorta supply?
Superior surface of the diaphragm
What are the 3 unpaired branches of the thoracic aorta?
pericardial, oesophageal, and mediastinal
What does the azygous system drain from?
Intercostal veins T5-T11
Which intercostal vein forms the azygous vein?
T12
How many pairs of posterior intercostals are there?
12
What veins drain T1-T4 on the right?
T1 drains straight into the right brachiocephalic vein, superior intercostal vein T2-T4 on the right
Where does the azygous vein arch?
Over the right hilum and then joins with the superior vena cava
What is meant by collateral circulation?
When blood can be redirected through a different path if there is a blockage
What vein drains T1-T4 on the left?
The left superior intercostal vein
What intercostal veins does the accessory hemi-azygous vein drain?
T5-T8 on the left
What intercostal veins does the hemi-azygous vein drain?
T9-T11 on the left
What veins join with the subcostal veins on either side?
The ascending lumbar veins
What veins does the superior vena cava split into?
The brachiocephalic veins
What is a tribetury?
A vain that drains into a larger vein
Where is the collateral pathway of the azygous system?
Between the inferior and superior vena cava
Where does the hemi-azygous vein ascend compared to the aorta?
Posterior left to the aorta
What is the largest lymph channel?
The thoracic duct
The thoracic duct conveys lymph from which organs?
All the body except head, neck and upper limb and thorax on the right
Where does the thoracic duct originate?
At the Cicterna Chyli in the abdomen (L2)
How does the thoracic duct ascend compared to the vertebrae?
Anteriorly
What does the thoracic duct drain into?
The left venous angle
Where is the left venous angle?
At the junction between the internal jugular and subclavian veins
How does the oesophagus pass compared to the aorta?
Posterior and to the right of the aorta but then moves to the left and becomes anterior to the abdominal aorta before entering the stomach. This switch happens at T4/5
What is innervation of the oesophagus?
Vagus nerve (CNX) and the sympathetic trunk via the oesophageal plexus
What are the 3 constrictions of the oesophagus?
The arch of the aorta, left main bronchi and the diaphragm
