Lecture 2 Flashcards
What is the mediastinum
The thoracic (Ab-Neck region) compartment between the pleural sac
What is the Plane of Ludwig and what structures does it contain?
-Horizontal plane across thorax
Contains:
1) Superior vena cava
2) Aorta
3) Trachea bifurcation
4) Pulmonary trunk bifurcation
Boundaries of superior mediastum
Superior:
- 1st rib
- T1
- Jugular notch
Inferior:
-Transthoracic plane
Posterior
-T1-4 Vertebrae
Anterior:
-Manubrium
Contents of the superior mediastinum
Structures:
1) Esophagus
2) Thoracic duct
3) Thymus
4) Trachea
5) Aortic arch and major vessels
6) Left and right brachiocephalic veins
7) Superior vena cava
8) Pulmonary arteries
Nerves:
1) Vagus
2) Recurrent laryngeal
3) Phrenic
Thymus
Function:
- Immune function
- Secretes hormones (puberty)
Blood supply:
-Internal thoracic and anterior intercostal
Venous drainage:
-Brachiocephalic, internal thoracic, and inferior thyroid veins
Lymph drainage:
-Into parasternal, brachiocephalic, and tracheobronchial lymph nodes
Trachea
- Continuation of the larynx at C6
- Terminates at transthoracic olane (Bifurcates into right and left bronchi)
- Crossed over by the arches of the aorta and azygos vein
Aortic Arch and Branches
Branches
1) Brachiocephalic trunk
- Right subclavian
- Right common carotid
2) Left common carotid
3) Left subclavian
Brachiocephalic veins
-Formed by the union of the subclavian and internal jugular
Posterior to sternoclavicular joints
Subclavian Artery
• Divided into 3 parts by the anterior
scalene muscle
1st part (VIT)
• Vertebral A.
• Internal thoracic A.
• Thyrocervical trunk
2nd part (C) • Costocervical trunk
3rd part
- Dorsal scapular
- Becomes the axillary artery at the lateral border of rib 1
Nerves of the mediastinum
Vagus
1) Vagus nerve
- Travels along common cartoid artery
-Path:
Esophagus (Esophageal plexus) –> down abs (Anterior vagal trunk-left vagus nerve) and (Posterior vagal trunk-right vagus nerve)
-Carries parasympathetic and visceral afferent to thoracic vertebrae
Nerves of the mediastinum
Recurrent laryngeal nerves
-Branch of vagus nerves on either side
- Left associated with arch of aorta
- Right associated with right subclavian artery
Nerves of the mediastinum
Phrenic nerve
• Enters sup. mediastinum
between the subclavian
artery and the root of the
brachiocephalic vein
• Courses along the pericardium, pierces through the diaphragm (innervates both)
• Sensory and motor
innervation to the diaphragm (C3, 4 , 5)
Inferior Mediastinum Boundaries, divisions, contents
Boundaries:
1) Superior = Transthoracic plane (Plane of ludwig)
2) Inferior = diaphragm
3) Anterior = Body of sternum
4) Posterior = T5-T12
Divisions-made up of all
1) Anterior
2) Middle
3) Posterior
Middle Mediastinum Boundaries and contents
-Fibrous/parietal layers of serous pericardium bind it
Contents:
1) Heart
- Ascending aorta
- Intrapericardial SVC
- Pulmonary trunk
2) Main bronchi
Posterior Mediastinum Boundaries and contents
Boundaries:
1) Anterior = Pericardium
2) Posterior = Vertebrae T5-12
Contents:
1) Sympathetic chain
2) Esophagus
3) Esophageal plexus
4) Azygos venous system
5) Descending thoracic aorta
6) Thoracic Duct
Sympathetic chain and
Splanchnic nerves
• Sympathetic chains are located laterally to the vertebral column
-Contain interconnected sympathetic ganglia
•3 distinct splanchnic nerves
1) Greater
- T5-9 with some variation
- Joins the celiac ganglion
2) Lesser
- T10-11
- Joins aortico-renal ganglion
Least
- T12 but not always present
- Joins the renal plexus
Esophagus Constriction/path of contriction points
- Junctions w pharnx at C6
- Enters the thorax through the superior thoracic aperture
Crossed by left main bronchus (T4/5)
- Pass diaphragm at es. hiatus T10
- Ends at cardiac sphincter
Anterior mediastinum
Divisions:
1) Anterior = Sternum
2) Posterior = Pericardium
Contents:
1) Thymus
2) Lymph node
3) Connective tissue
Esophagus Blood supply, innervation, venous, lymph drainage
Thoracic Portion
Thoracic portion:
• Arterial supply:
-thoracic aortic
-bronchial arteries
• Innervation:
- esophageal plexus,
- sympathetic trunks
• Venous drainage:
- azygos,
- hemiazygos veins
• Lymphatic drainage:
- thoracic duct,
- posterior mediastinal nodes
Esophagus Blood supply, innervation, venous, lymph drainage
Abdominal Portion
Abdominal portion:
• Innervation:
-vagal trunks,
-greater splanchnic nerves
• Arterial supply:
- left gastric artery,
- left inferior phrenic
• Venous drainage:
-left gastric vein
• Lymphatic drainage:
-left gastric
nodes
Azygos system
of veins
- Form a collateral drainage pathway between the IVC and SVC.
- Drain the back, thoracoabdominal wall, and mediastinal viscera
Right side: (Azygos)
Ascending lumbar and subcostal meet up, ascend through and arch over into SVC
Left side: (Hemiazygos)
Ascending lumbar vein and subcostal meet, cross over T5-8 level and meet up with azygos and SVC
Upper left: (Azygos accessory)
-Runs 4-8 intercostal veins/bronchial veins, crosses over T5-8 and reaches azygos and SVC
Descending thoracic aorta
Branches • Posterior intercostal arteries • 1 or 2 bronchial arteries • Pericardial and mediastinal branches • Esophageal branches • Superior phrenic artery • Subcostal artery
Trajectory • Continuation from aortic arch (T4/5) • Travels along the left side of the esophagus in its entire length down the thorax • Pierces aortic hiatus at T12 level to becomes the abdominal aorta
Diaphram hiatus’s
T8 = inferior vena cava (Right T10 = Esophagus (left) T12 = Aorta (Midline)
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Thoracic Duct Path
-Lymphatic vessel
Path:
Cisterna chyli –> Right side –> Diaphragm aortic hiatus –> azygos vein –> T5 crosses to left side –> Enters neck –> drains into junction of Left subclavian and Left internal jugular veins
