1 - Superior and Posterior Mediastinum Flashcards
Superior Mediastinum: Vessels
L/R Brachiocephalic Vein
Aoritic Arch
Brachiocephalic Trunk
Left Common Carotid
Left Subclavian
Superior Vena Cava
Superior Mediastinum: Nerves
Left Recurrent laryngeal Nerve
Phrenic Nerve
Vagus Nerve
Superior Mediastinum: Structures
Trachea
Esophagus
Thoracic Duct
Thymus (degrades with age)
Aoritic Arch: Location
Begins and ends at level of sternal angle (forms arch)
Located entirely in Superior Mediastinum
Courses Right to Left, and Anterior to Posterior
Branches: Braciocephalic Trunk, Left Common Carotid A. , Left Subclavian A.
Aortic Arch: Brachiocephalic Trunk
Largest branch of aortic arch
At right sternoclavicular joint, the trunk divides into: Right Common Carotid Artery, and Right Subclavian Artery
Arteries located slightly superior and posterior to corresponding veins
Aortic Arch: Left Common Carotid
Ascends left side of trachea
Left Head/Neck
Aortic Arch: Left Subclavian Artery
Ascends left side of trachea
Left upper extremity
Descending Thoracic Aorta: Location
Inferior to the level of sternal angle
Starts on left of thoracic vertebrae, gradually moves anterior
Passes through the Aortic Hiatus in the Diaphragm at Level T12
Descending Thoracic Aorta: Paired Branches
Paired Parietal Branches:
a. Nine pairs of Posterior Intercostal arteries supply 3-11 (1-2 supplied from Sup. Intercostal Br. of Costocervial Trunk - Branch of Subclavian)
b. One pair Subcostal Arteries (bellow rib 12)
c. One pair Superior Phrenic Arteries to upper side diaphragm
Descending Thoracic Aorta: Unpaired Branches
Unpaired Branches to Viscera
a. Two Left Bronchial Arteries
b. Two Esophageal Arteries
Veins in Sup/Post Mediastina: Right and left Brachiocephalic Veins
Formed by union of the internal jugular veins (head and neck) and the subclavian veins (upper extremities)
Begins posterior to Sternoclavicular Joints
- - -
Right - Goes basically straight down to Superior Vena Cava
Left - Oblique Cross over to join Right and form Superior Vena Cava; Located between Thymus and Brachiocephalic Truink and L Common Carotid
Veins in Sup/Post Mediastina: Superior Vena Cava
Formed by union of Right and left Brachiocephalic Veins
Extends from levels of right Ribs 1-3
Receives Azygos Vein at Sternal Angle, enters Right Atrium
Contains DEOXYGENATED blood from ALL STRUCTURES ABOVE DIAPHRAGM
Veins in Sup/Post Mediastina: Azygos Vein Location
Lies right of thoracic vertebrae
Superior continuation of right ascending lumbar vein
Passes through Aortic Hiatus of Diaphragm
Arches superior to root of right lung, to empty in Superior Vena Cava @ Sternal Angle
Veins in Sup/Post Mediastina: Azygos Drainage Pattern
Right Thoracic Wall via Posterior Intercostal Veins
Left Thoracic Wall vis Hemiazygos and Accessory Hemiazygos Veins
Esophagus (esophageal veins), lung tissue (bronchial veins), and the vertebral column and spinal cord (vertebral venous plexus)
Veins in Sup/Post Mediastina: Hemiazygos Vein (Inferior Hemiazygos)
Continuation of Left Ascending Lumbar Vein as it passes posterior diaphragm; drains left posterolateral abdominal wall into inferior vena cava (this branch becomes Hemiazygos)
Drains lower left intercostal spaces
Empties into Azygos
Veins in Sup/Post Mediastina: Accessory Hemiazygos Vein (Superior Hemiazygos)
Drains middle left intercostal spaces, empties into Azygos
What is the venous drainage patter for upper intercostals?
Right / Left Superior Intercostal Veins
These are NOT located in the posterior mediastinum, but do dump into veins there (Azygos, Left Brachiocephalic V.)
What provides a collateral pathway to right atrium for venous drainage?
Azygos Vein and Ascending Lumbar Veins provide collateral pathway to right atrium if Superior Vena Cava OR Inferior Vena Cava is blocked.
If they’re both blocked, you’re probably dead.
Clinical: Superior Vena Cava Syndrome
Bronchogenic Tumor of Right Lung can compress Superior Vena Cava
Head/Neck blood as difficulty returning to right atrium
Signs: Distended internal/external jugular veins in neck, subclavian tribs. in R upper limb
Still has collateral pathways (Aygos -> Asc. Lumbar V. -> Lumbar Veins -> Inferior Vena Cava)
Clinical: Liver Tumor Venous Compression
Tumor of Liver can obstruct Inferior Vena Cava
Venous blood can bypass via collaterals:
Lumbar Veins -> R/L Ascending Lumbar Veins -> Hemiazygos -> Azygos -> Superior Vena Cava