Thorax 4 - Mediastinum Flashcards
Where is the mediastinum found in the heart?
The area between the two pleural cavities.
What does the superior part of the mediastinum go up to?
The 2nd rib
What forms the anterior, middle and posterior mediastinum?
Anterior - between the sternum and the pericardium.
Middle - pericardium and its contents
Posterior - behind the pericardium, anterior to T5 and T12
What does the posterior mediastinum contain?
The descending aorta Thoracic duct Azygos vein system Oesophagus Sympathetic chain
The descending aorta, trachea and oesophagus lie anterior to the azygos vein system and the thoracic duct.
What are the main things inside the superior mediastinum?
- Aortic arch and its 3 branches
- Brachiocephalic veins
- Sympathetic chain
- Vagus nerves
- Phrenic nerves
- Trachea
- Oesophagus
- Thoracic duct
- Lymph nodes
What are the names of the 3 branches that come off the aorta?
Brachiocephalic trunk
Left common carotid
Left subclavian artery
What do brachiocephalic veins come together to form?
The superior vena cava
What part of the spinal cord does the sympathetic chain come from?
Phrenic nerves?
T1 - L2
C3-C5
Explain where the vagus nerve comes from and what it forms at the heart?
It comes from the brain stem (cervical part of the spinal cord). At the aorta, it forms a cardiac plexus which is important in parasympathetic autonomic control of the heart.
What does the thoracic duct do?
Biggest lymphatic duct draining the lymph back into the venous circulation.
What does the bronchial artery come off and what does it do?
the aorta, it supplies the lungs with blood
Where does the descending aorta emerge?
Behind the diaphragm at T12
What does the right subclavian artery split into?
The anterior intercostal muscles and an internal thoracic artery
What does the pericardiophrenic artery supply?
Blood to the pericardium
Where does the oesophagus pass through the diaphragm?
T10
What is the azygos system?
Lies posterior to the descending aorta, trachea and oesophagus.
The posterior intercostal muscles drain into this system, the veins merge to form accessory veins.
They drain upwards and form the superior vena cava.
Give details on the thoracic duct
- Collects lymph from the intestines and lower limbs
- runs superiorly between the oesophagus and the descending aorta
- crosses from right to left at T4/5, lying between the azygos vein and aorta
- empties into the venous system at the point where the left internal jugular and subclavian veins meet
What is the role of the phrenic nerves?
To keep the diaphragm alive
Where does the intercostal nerve come from?
It is from the ventral ramus of the spinal cord
Explain how the sympathetic nerves leave the spinal cord
They leave via the ventral horn and synapse within the sympathetic chain (a chain of nerves with their ganglia - collection of cell bodies). They have short preganglionic ganglia because they come out the central horn and synapse immediately.
What is the function of the sympathetic chain in the heart and lungs?
Heart - increases rate and contractility
Lung - vasocontriction and bronchiodilation
Explain how the vagus nerve is positoned in the body
It comes out the brain stem and innervates the aorta. It has a branch which innervates the larynx.
Where are the phrenic nerve and vagus nerve positioned in terms of the lungs?
Phrenic nerve is infront and the vagus nerve goes behind
Does the vena cava pass through the muscular or tendon part of the diaphragm?
It passes through the vena cava foramen which is located in the central tendon of T8.
