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
Where does the Thoracic Duct receive lymph from?
Everything drains inter left thoracic duct except
1) Jugular trunk
2) subclav trunk
3) bronciomedistinal nodes
4) upper intercostal nodes
Thoracic outlet syndrome
Causes
Effects
Symptoms
Thoracic outlet syndrome Cause: 1) Extra rib attaching to the 7th Cervical vertebra and rib 1 2) Muscular abnormalities 3) Trauma, tumor
Leads to compression of axillary inlet components:
• Subclavian artery/vein: thrombosis/embolization
• Nerves (C8-T1): sensory deficit, muscle wasting
Symptoms
1) Neurological: pain, paresthesia, paresis/paralysis
2) Vascular: pallor, pulselessness, poikilothermia (cold),
edema (venous compression)
