Mediastinum II Flashcards
what are the major divisions of the mediastinum?
Superior
Inferior (anterior, middle, posterior)
what is in the superficial division of the mediastinum?
Internal thoracic aorta
Thymus
Superior vena cava
Parasternal lymphatics
what is in the middle layer of the mediastinum?
Arch of the aorta
Pulmonary trunk
Vagus nerve
Phrenic nerve
what is in the deep layer of the mediastinum?
Trachea
Esophagus
Recurrent laryngeal n.
Thoracic duct
Azygos vein
Sympathetic trunk
what is contained in the superior mediastinum?
-Thymus, thoracic duct
- Internal thoracic blood vessels, great vessels of the heart, ligamentum arteriosum, azygous veins
- Vagus nerve, phrenic nerve, recurrent laryngeal nerve, sympathetic trunk
- Trachea
- Esophagus
what are the 3 layers of the superior mediastinum?
-superficial
-middle
-Deep
*different on the left and right
what is contained in the superficial layer of the superior mediastinum?
Internal thoracic arteries and veins
- inferior anterior mediastinum
Thymus
Superior vena cava and major branches
Parasternal lymphatics
what are the features of the thymus?
Immediately posterior to sternum
Bi-lobar
what is the role of the thymus?
Early development of the immune system
- T-cells multiply, differentiate into specialised immune cells, prevent autoimmunity
what are the features of the thymus in children?
Root of the neck
- as far superiorly as thyroid cartilage
Inferior anterior mediastinum
- 4th costal cartilage
what are the features of the thymus in adults?
-Atrophies after puberty
- Mostly fatty tissue
what happens if the left BCV is distended?
it can extend above the superior media stinum
- becomes vulnerable to suprasternal incisions
what are the features of the left and right brachiocephalic veins?
-Subclavian vein and internal jugular vein
- Posterior to medial ends of clavicles
The left BCV is longer than the right
- has to pass anterior to the branches of the aorta
what do the brachiocephalic veins drain?
Drainage of the upper limb, head and neck
what is contained within the middle layer of the superior mediastinum?
- Aortic arch and major branches (pulmonary trunk and pulmonary arteries (middle mediastinum))
- Ligamentum arteriosum
- Vagus nerve
-phrenic nerve
what are the features of the arch of the aorta?
- Emerges from pericardial sac as ascending aorta
- Sternal angle=arch
Course
- Superior (mid-manubrium), posterilateral (left)
3 main branches
what are the ABC’s of the Aorta?
Arch
Brachiocephilic arch
left Common carotid artery
left Subclavian artery
what are the features of the Pulmonary trunk and arteries?
- (middle mediastinum)
- Emerges: left of arch
- Passes: posterior to superior vena cava and arch of aorta
where does the vagus nerve emerge from?
10th cranial nerve - brainstem
what is the role of the vagus nerve?
Parasympathetic innervation to thoracic and abdominal organs
where is the vagus nerve?
Lateral to trachea
Left: lateral to arch of aorta
where does the phrenic nerve arise from?
C3, C4, and C5
what does the vagus nerve innervate?
Esophageal plexus, cardiac plexus, pulmonary plexus
what does the phrenic nerve innervate?
Diaphragm, pericardium (parietal serous and fibrous) and pleura
where is the phrenic nerve?
-behind the subclavian vein, in front of the lung root
- Lies as lateral as possible- in contact with mediastinal pleura
- on the lateral aspect of the great vessles
what is contained within the deep layer of the superior mediastinum?
Trachea
Esophagus
Left recurrent laryngeal nerve (vagus)
Thoracic duct
Azygos vein
Sympathetic trunks
what is the function of the lower esophageal sphincter?
Controls entrace into the stomach
what are the narrowings of the esophagus?
- Upper esophageal sphincter (C6, cricoid)
- Aortic arch
- Left main bronchus
- Esophageal hiatus (diaphragm)
where does the esophagus run?
Joins the pharynx to the stomach
- Cervical (skeletal muscle), thoracic, abdominal (smooth muscle)
what is posterior to the esophagus?
Vertebral bodies
what is anterior to the esophagus?
Trachea
what is right to the esophagus?
Azygos vein
what is left to the esophagus?
Arch of the aorta
what is the recurrent laryngeal nerve?
Branch of the vagus nerve
There are left and right
what are the features of the left recurrent laryngeal nerve?
-superior mediastinum
-ligamentum arteriosum
-Arch of the aorta
what are the features of the right recurrent laryngeal nerve?
-neck region
-right subclavian artery
what does the recurrent laryngeal nerve innervate?
Trachea
Esophagus
Larynx
what can happen to the left recurrent laryngeal nerve?
It is susceptible to compression as it passes under the aortic arch
the symptoms: vocal cord paralysis, hoarsenees of voice
where is the thoracic duct?
Posterior infeior mediastinum
- Cisterna chyli (T12)
- Between aorta and azygous vein
- Moves to the left (alongside aorta) behind esophagus
what is the role of the thoracic duct?
Drains into left brachiocephalic vein
- junction between the internal jugular vein and left subclavian vein
Drains body of lymph
- except right upper limb, right half of thorax, head and heck = right lymphatic duct
what are the features of the Azygos vein?
- Right laternal aspect of vertebral bodies
- Venous drainage: posterior thoracic wall (upper lumbar region)- posterior intercostal veins
-Superior aspect is located within superior mediastinum
where does the azygos vein enter?
Superior vena cava
what is the sympathetic trunk of the nervous system?
-Parallel chains of nerves
- Lateral to vertebral column (neck of ribs)
-Sympathetic innervation thoracic and abdominal viscera
Superior mediastinum (pulmonary, esophageal, cardiac plexuses)
