Superior Mediastinum Flashcards
Where is the mediastinum
Central compartment of thorax, located between left and right pleural cavities
how is the mediastinum divided
superior and inferior at t4/5 (aka sternal angle or transverse thoracic plane)
how is the inferior mediastinum divided
Anterior
Middle
Posterior
Boundaries of superior mediastinum
Superior: superior thoracic aperture (manubrium, 1st rib and costal cartilage, T1 vertebrae)
Inferior: transverse thoracic plane (sternal angle to vertebral level T4/5)
Anterior: manubrium
Posterior: T1-T4/5 vertebral bodies
Lateral: mediastinal pleura
Contents of superior mediastinum
Arteries (arch of aorta and branches) Veins (brachiocephalic veins and superior vena cava) Phrenic and Vagus Nerves Oesophagus Trachea Thoracic duct Thymus gland (part)
where is the thymus gland located
Located immediately deep to the sternum in superior and anterior mediastinum
Supplied by internal thoracic artery
what is the thymus gland
Lymphoid organ
what does the thymus gland do
T and B lymphocytes produced in bone marrow, T’s mature in thymus
Lymph drains through from parasternal, brachiocephalic and tracheobronchial nodes
After puberty it atrophies and replaced by fat
what arteries are in the superior mediastinum
Arch of aortas and 3 branches
1 brachiocephalic trunk (branches into right common carotid and subclavian arteries)
2 left common carotid artery
3 left subclavian artery
Order is alphabetical L to R facing patient
what makes up the branches of the aorta
Ascending Aorta (LCA and RCA) Arch of aorta (1,2,3 in mediastinum) Descending aorta (posterior intercostal, bronchial arteries (branches from intercostal), lumbar arteries)
Veins in the superior mediastinum
Superior vena cava (form by union of two (L and R) brachiocephalic veins)
Each brachiocephalic vein is formed by the union of an internal jugular vein and a subclavian vein
middle, from L brachiocephalic is inferior thyroid vein
what is the ligament arteriosum
Embryological remnant of the ductus arteriosus: an open duct connecting the pulmonary trunk and arch of aorta
Important in fetal circulation allowing blood the bypass the immature lungs
Closes at birth and remains in the adult as ligamentous structure
what is the trachea
tube with C shaped cartilage rings, trachealis muscle runs posteriorly, runs from larynx to bronchi
what is the oesophagus
muscular tube, runs from pharynx to stomach
what does the thoracic duct do
Transports lymph to venous system
Receives multiple branches throughout thorax
Numerous lymph nodes associated with thoracic (descending) aorta
what does the phrenic nerve do
Motor supply to diaphragm
Sensory supply to diaphragm (central region) and parietal pleura (diaphragmatic and mediastinal)
where is the phrenic nerve found
Originates from anterior rami of spinal nerves (C3, C4, C5) (keep the diaphragm alive)
Enters superior mediastinum between brachiocephalic veins and subclavian arteries
Pass anterior to main bronchi
what is the vagus nerve
Cranial Nerve (CNX) originates from brainstem
where is the vagus nerve found
Each (L and R) enters the superior mediastinum just medial to phrenic nerve
Each gives rise to recurrent laryngeal branch to supply larynx (branch under aorta)
Continues into posterior mediastinum coursing posterior to main bronchi
what does the vagus nerve do
Provides parasympathetic supply via pulmonary, cardiac and oesophageal plexi
what is the anterior mediastinum
Narrow cavity containing: Thymus gland in children Pericardial-sternal ligaments Lymph nodes (parasternal) and vessels Internal thoracic artery
what are the boundaries of the anterior mediastinum
Sternum anteriorly
Pericardial sac posteriorly
Diaphragm inferior
Level T4/5 superiorly
where does the heart develop from
Angiogenic structures form in the mesoderm and these canalise for form early blood vessels
how does the heart develop (prior to day 21)
Two large blood vessels known as the heart tubes form in the cardiogenic area
The paired heart tubes grow and fuse at approximately day 21
