Thorax Part 4 Flashcards
What are the 4 parts of the mediastinum?
- Superior mediastinum
- Anterior mediastinum
- Middle mediastinum
- Posterior mediastinum
What are the boundaries of the mediastinum?
- Superiorly: Superior thoracic aperture
- Inferiorly: Diaphragm
- Anteriorly: Sternum
- Posteriorly: 12 thoracic vertebrae
Where are the boundaries of the superior mediastinum?
- Superiorly: Superior thoracic aperture
- Inferiorly: Sternal angle
- Anteriorly: Manubrium
- Posteriorly: Thoracic vertebrae (T1 - T4)
Where are the boundaries of the anterior mediastinum?
- Superiorly: Sternal angle
- Inferiorly: Diaphragm
- Anteriorly: Sternum
- Posteriorly: Pericardium
Where are the boundaries of the middle mediastinum?
- Superiorly: Sternal angle
- Inferiorly: Diaphragm
- Anteriorly: Pericardium
- Posteriorly: Pericardium
Where are the boundaries of the posterior mediastinum?
- Superiorly: Sternal angle
- Inferiorly: Diaphragm
- Anteriorly: Pericardium
- Posteriorly: Thoracic vertebrae (T5 - T12)
What important structures are found in the superior mediastinum before adulthood but not after?
Thymus gland
- Prominent before & during puberty
- Turns into a fatty connective tissue that is a residual structure in adults
What important arteries are found in the superior mediastinum? (8)
- Ascending aorta
- Aortic arch
- Brachiocephalic artery
- Right subclavian artery
- Right common carotid artery
- Left common carotid artery
- Left subclavian artery
- First part of the thoracic aorta
What important veins are found in the superior mediastinum? (11)
- Pulmonary trunk
- Right pulmonary artery
- Left pulmonary artery
- Superior vena cava
- Azygous vein
- Right brachiocephalic vein
- Right subclavian vein
- Right internal jugular vein
- Left brachiocephalic vein
- Left subclavian vein
- Left internal jugular vein
What important lymphatic ducts are found in the superior mediastinum?
- Right lymphatic duct
- Thoracic duct
What important pulmonary structures are found in the superior mediastinum?
Trachea
What important digestive structures are found in the superior mediastinum?
Oesophagus
What important neurological structures are found in the superior mediastinum?
- Upper portions of the sympathetic trunk
- Vagus nerves travelling down from the neck:
- Right vagus nerve crossing over right subclavian artery where the right recurrent laryngeal nerve branches off and travels back up to the larynx
- Left vagus nerve crossing over arch of aorta where the left recurrent laryngeal nerve branches off and travels back up to the larynx
- Superficial cardiac plexus lying on the arch of the aorta which is formed by branches from the left and right vagus nerves (parasympathetic), and branches from T1-T4 portions of the sympathetic trunk (see image below)
-
Phrenic nerves travelling down from the neck
- Right and left internal thoracic arteries branching from the right and left subclavian arteries respectively.
- Vagus nerves travelling down from the neck:
What are the functions of the superficial cardiac plexuses?
-
Parasympathetic innervation
- Decreases heart rate
- Reduces force of contraction
- Constricts the coronary arteries
-
Sympathetic innervation
- Increases heart rate
- Increases the force of contraction
What important structures are found in the anterior mediastinum?
-
Thymus gland
- Prominent before & during puberty
- Turns into a fatty connective tissue that is a residual structure in adults
- Arteries:
- Internal thoracic artery
- Lymph nodes:
-
Parasternal nodes
- Drain a small portion of lymph from the breast
-
Prepericardial lymph vessels
- Drain a small portion of lymph from the breast
-
Parasternal nodes
What important structures are found in the middle mediastinum?
- Cardiac structures:
- Pericardium containing the heart
- Ascending aorta
- Pulmonary trunk
- SVC/IVC
- Pulmonary veins
- Pericardiacophrenic artery and vein
- Pulmonary structures:
- Bifurcation of the trachea
- Right and left main bronchi
- Bifurcation of the trachea
- Neurological structures:
- Left and right phrenic nerves
- Deep cardiac plexus formed by cardiac branches of left and right vagus nerves (parasympathetic) and cardiac branches from the sympathetic trunk (T1-T4)
- Lymphatic structures:
- Tracheobronchial lymph nodes lying on main bronchus and inferior trachea
What are the functions of the superficial cardiac plexuses?
-
Parasympathetic innervation
- Decreases heart rate
- Reduces force of contraction
- Constricts the coronary arteries
-
Sympathetic innervation
- Increases heart rate
- Increases the force of contraction
What is the pathological significance of the tracheobronchial lymph nodes?
- These nodes may become enlarged in the case of pathology of the lungs
- Biopsies of these nodes can be taken to determine different disease states
- They can be accessed by making a slit above the jugular notch to enter the superior mediastinum, travel down the trachea until the point of bifurcation where the nodes are located
- This allows access to these nodes without damaging the pleurae or lung tissue itself
- They can be accessed by making a slit above the jugular notch to enter the superior mediastinum, travel down the trachea until the point of bifurcation where the nodes are located
What important structures are found in the posterior mediastinum (More anteriorly)?
- Cardiac structures
-
Descending aorta
- Intercostal arteries
- Mediastinal branches of the descending aorta
- Pericardial branches of the descending aorta
- Oesophageal branches of the descending aorta
- Superior phrenic arteries
-
Descending aorta
- Digestive structures
- Oesophagus
- Neurological structures
-
Vagus nerves (Left & Right) (Parasympathetic)
- Oesophageal plexus
- Anterior vagal trunk
- Posterior vagal trunk
-
Vagus nerves (Left & Right) (Parasympathetic)
What important structures are found in the posterior mediastinum (More posteriorly)?
- Cardiac structures
-
Azygous vein
- Formed by the marching of the right subcostal vein & the right ascending lumbar vein
- Posterior intercostal veins
- Hemiazygos vein
- Accessor hemiazygos vein
- Superior intercostal veins (Left & Right)
-
Azygous vein
- Lymphatic structures
- Thoracic duct (Begins as cisterna chyli)
- Neurological structures:
-
Greater Thoracic Splanchnic Nerve (Left & Right) (Sympathetic)
- Originate from T5 - T9
-
Greater Thoracic Splanchnic Nerve (Left & Right) (Sympathetic)
