Mediastinal Structures Flashcards
What is the mediastinum?
The partition between the two pleural cavities and lungs
What are the two subdivisions of the mediastinum?
Superior mediastinum and inferior mediastinum
What are the three divisions of the inferior mediastinum?
Anterior
middle and posterior mediastinum
Where is the superior mediastinum?
Bounded anteriorly by the manubrium of the sternum and posteriorly by the bodies of T1 to T4 vertebrae
What are the contents of the superior mediastinum?
Thymus
Left brachiocephalic vein
Right brachiocephalic vein
Superior vena cava
How are the veins of the superior mediastinum located?
The two brachiocephalic veins unite to form the superior vena cava
What is the difference in shapes between the left and right brachiocephalic vein?
The left vein is longer and more oblique
The right is more vertical
Where are the aortic branches located?
Superior mediastinum
What are the three aortic branches?
Left common carotid
Left subclavian
Brachiocephalic
Where does the phrenic nerve originate?
C3-C5
Where is the phrenic and vagus nerves related to the root of the lung?
Phrenic nerve is anterior
Vagus nerve is posterior
Where is the left recurrent laryngeal nerve?
Located in the superior mediastinum
Where is the anterior mediastinum located?
Posterior to body of sternum and attached costal cartilages, anterior to heart and pericardium
What are the contents of the anterior mediastinum?
Fat
Remnants of thymus glands
Anterior mediastinal lymph nodes
Where is the location of the middle mediastinum?
Between anterior and mediastinum and posterior mediastinum
What are the contents of the middle mediastinum?
Heart and pericardium Beginning or termination of great vessels Phrenic nerves Pericardiacophrenic vesels Lymph nodes
Where is the posterior mediastinum located?
Posterior to heart and pericardium - anterior to vetebrae T5-T12
What does the posterior mediastinum contain?
Contains 4 tubular structures Oesphagus Thoracic aorta Thoracic duct Azygous venous system
What is the thoracic aorta?
Continuation of the aortic arch at lower border T4
What is the route of the thoracic aorta?
Courses downward on left side of, then in front of the vertebral column
Passes through the aortic hiatus of diaphragm at level of T12 vertebra to enter abdominal cavity
What are the two main branches of the thoracic aorta?
Parietal branches and visceral branches
What is meant by parietal?
The wall
What is meant by visceral?
to the organ
What makes up the parietal branches of the thoracic aorta?
Nine pairs of the posterior intercostal arteries
One pair subcostal artery
What makes up the visceral branches of the thoracic aorta?
Bronchial branches: one or two for each lung
Oesphageal and pericardial branches
What forms the brachiocephalic vein and where?
Formed by the union of internal jugular and subclavian veins posterior to the sternoclavicular joint
What is the angle of union of the brachiocephalic veins known as?
Venous angle
What forms the superior vena cava and where?
Formed by the union of right and left brachiocephalic veins behind the right sternocostal joint of the first rib
Where does the superior vena cava run?
Runs vertically down on the right of the acending aorta
Where does the azgous vein join the superior vena cava?
Level of sternal angle
Where does the SVC enter the right atrium?
Enters at the lower border of the third right sternocostal joint
What is the role of the SVC?
Collects blood from veins of upper half of the body
What does the azgos vein begin as?
Continuation of right ascending lumbar vein
How is the azygos vein formed?
Formed by the union of the ascending lumbar veins with the right subcostal veins at the level of the 12th thoracic vertebrae
What are the two tributaries of the azgous vein?
Hemiazygous vein
Accessory hemiazygous
Where does the thoracic duct begin?
Begins in front of L1 as a dilated sac
What is the dilated sac that forms the thoracic duct known as?
Cisterna chyli
How is the dilated sac formed?
Joining of left and right lumbar trunks and intestinal trunk
Where does the thoracic duct travel?
Enters the thoracic cavity by passing through the aortic hiatus of the diaphragm and ascends along the front of the vertebral column between thoracic aorta and azygous vein
What happens to the thoracic duct at T5?
It veers to the left
What happens to the thoracic nerve at the root of the neck?
Turns laterally and arches fowards and descends to enter the left venous angle
What happens if there is a hole in the thoracic duct?
Forms a chylothorax
What is the role of the thoracic duct?
Drains lymph from lower limbs, pelvic cavity, abdominal cavity, left side of thorax, and left side of the head, neck and left upper limb
What forms the right lymphatic duct?
Formed by the union of the right jugular, subclavian and bronchomedastinal trunks
How does the right lymphatic duct end?
Ends by entering the right venous angle
Where does the phrenic nerve run?
Runs posterior to the subclavian vein
What happens when the phrenic nerve enters the thorax?
Runs anterior to the root of the lung and into the pericardium between the fibrous and parietal layers
What do the phrenic nerves supply?
Supply motor fibres to the diaphragm and sensory fibrous pericardium
medistinal pleura and diaphragmatic peritoneum
Where does the left vagus nerve enter the thoracic inlet?
Between the left common carotid and left subclavian arteries, posterior to the left brachiocephalic vein
What happens to the left vagus nerve as it crosses the aortic arch?
The left recurrent laryngeal nerve branches off
The LVN passes posterior to the left lung
What does the LVN form?
Anterior oesophaegeal plexus
Forms anterior vagal trunk at the hiatus where it leaves thorax and passes into abdominal cavity, then divides anterior gastric and hepatic branches
Where does RVN enter the thoracic inlet?
The right side of the trachea
Where does the RVN travel?
downward posterior to right brachiocephalic vein and superior vena cava
passes posterior to right lung root
What does the RVN form?
Posterior oesophageal plexus
Posterior vagal trunk
Where is the posterior vagal trunk formed and where does it travel
Formed at the oesophagul haitus
Leaves thorax and passes into abdominal cavity and then divides in to posterior gastric and celiac branches
What is the path of the recurrent laryngeal nerve?
Right one hooks around right subclavian artery and left one hooks around the aortic arch
Both ascend in tracheo-oesphageal groove
What do the recurrent laryngeal nerves innervate?
Laryngeal mucosa below fissure of glottis
All laryngeal muscles exceot cricothyroid
What is the oesophagus?
A muscular tube passing through between the pharynx in the neck and stomach in the abdomen
Where does the oesophagus begin?
Begins at the inferior broder of the cricoid cartilage, opposite vertebrae CVI
Where does the oesophagus end?
Ends at the cardiac opening of the stomach opposite T11
Where does the oesophagus travel?
Oesophagus descend on the anterior aspect of the bodies of the vertebrae (midline position)
Approaches the diaphragm, it moves anteriorly
Passes through the oesphageal hiatus ( an opening in the muscular part of the diaphragm, at vertebral level T10)
What are the four locations where the muscular tube that can be compressed or narrowed?
Pharynx
Arch of aorta
Left main bronchus
Oesophageal hiatus
What are the three parts of the oesphagus?
Cervical
Thoracic
Abdominal
What makes up the sympathetic trunk?
Thoracic viscera (T1-T4)
Greater splanchnic nerve
Lesser splanchic nerve
Least splanchnic nerve
What level is the caval opening and what structures are present within it?
T8
inferior vena cava and some branches of the right phrenic nerve
What level is the oesphageal hiatus and what structures are present within it?
T10
oesophagus, the anterior and posterior vagal trunks, and some small oesphageal arteries
What level is the aortic hiatus and what structures are present within it?
T12
aorta, the azygos vein and the thoracic duct
What are the structures within in the two lesser aperture of the right crus?
Greater and lesser right splanchnic nerves
What are the structures of the three leser aperature of left crus?
Greater and lesser left splanchnic nerevs and the hemiazygos vein
What are the structures that go through the opening behind the diagram, under the medial acruate ligament
Sympathetic trunk and the least splanchic nerves
What are the structures that pass through the opening anterior to the diaphragm, just deep to the ribs?
Superior epigastric vessels
What are the structures that pass through the diaphragm?
inferior vena cava
some branches of the right phrenic nerve
oesophagus
the anterior and posterior vagal trunks
some small oesophageal arteries
the aorta
the azygos vein
the thoracic duct
greater and lesser right splanchnic nerves
greater and lesser left splanchnic nerves
the hemiazygos vein
sympathetic trunk
the least splanchnic nerves on both sides
sympathetic trunk
the least splanchnic nerves on both sides
Where do the upper 6 pairs of anterior intercostal arteries arise from?
Internal thoracic artery
Where do the 7th, 8th and 9th pairs of anterior intercostal arteries arise from?
Musculophrenic artery
What is the origin of the internal thoracic artery?
From the first part of the subclavian artery
Where does the internal thoracic artery terminate?
Opposite the sixth intercostal space by dividing into superior epigastric and musculophrenic arteries
What are the 8 branches of the internal thoracic artery?
- Pericardial branches. 2. Pericardiaco-phrenic artery.
- Mediastinal branches. 4. Sternal branches.
- Perforating branches for the mammary gland.
- Anterior intercostal arteries (upper 6 spaces).
- Superior epigastric artery.
- Musculo-phrenic artery.
What forms the internal thoracic vein and where is it formed?
Formed by the union of the two venae comitantes of the internal thoracic artery
Behind the third costal cartilage
Where does the internal thoracic vein ascend and where does it terminate?
Ascends close to the artery and terminates at the corresponding innominate vein
What does each posterior intercostal artery give and where does this structure run?
Gives a collateral branch and is runs over the upper border of the rib below
Were do the upper two posterior intercostal arteries come from?
superior intercostal artery from the second part of the subclavian artery
What do the posterior arteries 3-11 come from?
Descending thoracic aorta
