Thorax: Posterior Mediastinum Flashcards
Posterior Mediastinum
- Between pericardium/diaphragm and vertebral bodies
Posterior Mediastinum Boundaries
- Anterior: pericardium
- Posterior: T5-12 vertebral bodies
- Superior: transverse thoracic plane
- Inferior: diaphragm
- Lateral: mediastinal pleura
Posterior Mediastinum Contents
- Descending thoracic aorta
- Lymphatic trunks (thoracic duct)
- Lymph nodes
- Azygos, hemiazygos venous system
- Esophagus
- Vagus nerve
- Esophageal nerve plexus
- Thoracic splanchnic nerves
- Sympathetic trunk (PROBABLY NOT)
Descending Thoracic Aorta
- Travels from T5 – T12 vertebral bodies, left of the median plane
- Posterior to root of left lung, pericardium and esophagus.
- Enters abdomen through aortic hiatus (T12 vertebral level) in the diaphragm
- Supplies viscera and body wall
Branches of Descending Thoracic Aorta
- Esophageal arteries
- Bronchial arteries
- Posterior intercostal arteries
- Subcostal arteries
Esophageal Arteries
- 2-5 branches
Bronchial Arteries
- Left: paried branches from thoracic aorta
- Right: often arises from the left bronchial or the 3rd right posterior intercostal artery
Posterior Intercostal Arteries
- 9 pairs from the aorta
- First 2 pairs come from somewhere else
Esophagus
- Posterior to heart base (pericardium surrounding left atrium)
- Enters abdomen through esophageal hiatus, T10 level
4 Natural Constrictions/Impressions of Esophagus
- Junction with pharynx
- Arch of the aorta
- Left main bronchus
- Esophageal hiatus
Azygos Venous System
- Drains thoracoabdominal wall, mediastinal viscera
- A lot of variation
Azygos Vein
- Collateral pathway between SVC and IVC
formed by right ascending lumber and subcostal vein - Drains into SVC
- Arches over right main bronchus
Tributaries of Azygos Vein
- Bronchial, esophageal mediastinal veins
- Right intercostal veins 5-11
- Right superior intercostal veins
Right Superior Intercostal Veins
- Receives right intercostal veins 2-4
- Hemiazygos
- Accessory hemiazygos veins
Hemi-Azygos Vein
- Left side
- Formed by left ascending lumbar and subcostal veins
- Drains into the azygos vein
Tributaries of Hemi-Azygos Vein
- Esophageal, mediastinal veins
- Receives left intercostal veins 9-11
Accessory Hemi-Azygos Vein
- Left side
- Drains into the azygos vein
Tributaries of the Hemi-Azygos Vein
- Esophageal, mediastinal veins
- Receives left intercostal veins 4 (5)-8
Left Superior Intercostal Vein
- Receives left intercostal veins 2-3(4)
- Drains into left brachiocephalic
- Can drain into accessory hemi-azygos vein
Left and Right 1st Intercostal Veins
- Drain into the brachiocephalic veins
Thoracic Lymphatic Duct
- Receives lymph from most of the body
except right arm, right head neck, right upper quadrant of torso - Originates from the cisterna chyli, level of L1/2
- Passes through aortic hiatus
- Posterior to esophagus, between aorta and azygos
- T5 crosses to the left into superior mediastinum
- Empties in to left venous angle
Thoracic Sympathetic Trunk
- Sympathetic part of autonomic nervous system
- Lie against head of the ribs
- Contains ganglia
Thoracic Splanchnic Nerves
- Arise from sympathetic trunk ganglia
- Convey presynaptic neurons
- Greater splanchnic nerve: T5 – 9
- Lesser splanchnic nerve: T10 – 11
- Least splanchnic nerve: T12
- These supply abdominal organs
T5 – 9
- Greater splanchnic nerve
T10 – 11
- Lesser splanchnic nerve
T12
- Least splanchnic nerve
Diaphragm
- Double-domed musculotendinous structure
- Separates thoracic and abdominal cavities
- Movement changes pressure in the thoracic and abdominal cavities
- Fixed at its periphery
- Right dome reaches 5th rib on expiration
Double-Domed Musculotendinous Structure
- Muscular periphery
- Central tendon
Movement Changes Pressure in the Thoracic and Abdominal Cavities
- Respiration
- Venous return
Right Dome
- Reaches 5th rib on expiration
- Posture dependent (highest when supine)
Left Dome
- Left reaches 5th intercostal space
- Posture dependent (highest when supine)
Dyspnea
- Sitting up makes breathing easier
Parts of the Diaphragm
- Sternal
- Costal
- Lumbar
Sternal Diaphragm
- Attaches to xiphoid process
Costal Diaphragm
- Attaches to inner surface of costal cartilage ribs 7-10
- Attaches to ribs ll & 12
Phrenic Nerve
- Motor innervation of diaphragm
Phrenic Nerve (Central Portion); Intercostal Portion (Periphery)
- Sensory innervation of diaphragm
Major Openings in the Diaphragm
- Caval opening (level of T8)
- Esophageal hiatus (level of T10)
- Aortic Hiatus (level of T12)
Smaller openings of the Diaphragm
- Transmit greater and lesser splanchnic nerves
- Sympathetic trunk and least splanchnic nerve pass posterior to medial arcuate ligament
- Sternocostal foramen
Sternacostal Foramen
- Transmit superior epigastric vessels and lymph
Caval opening (level of T8)
- Inferior vena cava
- Right phrenic nerve
- Lymphatics
Esophageal hiatus (level of T10)
- Esophagus
- Vagus nerves
- Esophageal branches/tributaries of left gastric artery/vein
Aortic Hiatus (level of T12)
- Aorta
- Azygos vein
- Hemiazygos vein
- Thoracic duct
Sternal Angle
- Angle of Louis
Sternal Angle (Angle of Louis)
- Located at manubriosternal junction
- Location of the transverse thoracic plane
- Costal cartilage of rib 2
- T4/5 disc
- Beginning and end of aortic arch
- Bifurcation of trachea, location of carina
- Bifurcation of pulmonary trunk
- Left recurrent laryngeal nerve
- Cardiac plexus
- Ligamentum arteriosum
