superior mediastinum Flashcards
what is the location of the mediastinum? 2
- central compartment of the thorax
- located between the left and right pleural cavities
what is the mediastinum divided into? 2
- superior (normally pass into the posterior)
- inferior (at T4/5)
what is the inferior mediastinum divided into? 3
- anterior
- middle
- posterior
what is the level t4/5 also known as? 2
- the sternal angle
- transverse thoracic plane
what are the boundaries of the superior mediastinum? 5
- superior= thoracic aperture (manubrium, 1st rib, costal cartilage, T1, vertebra)
- inferior= transverse thoracic plate
- anterior=manubrium
- posterior= T1-T4/5 vertebral bodies
- lateral= mediastinal pleura
what are the contents of the superior mediastinum? 8
- arteries (arch of aorta and branches)
- veins (brachiocephalic and superior vena cava)
- phrenic and vagus nerves
- oesophagus
- trachea
- thoracic duct
- thymus gland
what is the thymus gland? 6
- located immediately deep to the sternum and superior and anterior mediastinum
- lymphoid organ
- T cells mature in the thymus gland
- lymph drains from parasternal, brachiocephalic and tracheobronchial nodes
- after puberty it atrophies and is replaced by fat
- supplied by the internal thoracic arteries
what are the arteries in the superior mediastinum? 4
- arch of aorta
- brachiocephalic trunk
- left common carotid artery
- left subclavian artery
what does the brachiocephalic trunk branch into? 2
- right common carotid artery
- right subclavian artery
what are the branches of the ascending aorta? 2
- left coronary artery
- right coronary artery
what are the branches of the descending aorta? 3
- posterior intercostal
- bronchial arteries
- lumbar arteries
what are the veins in the superior mediastinum? 5
- superior vena cava is formed by the union of the
- right brachiocephalic vein
- left brachiocephalic vein- each are formed from
- internal jugular vein
- subclavian vein
what is the ligamentum arteriosum? 4
- important landmark for surgeons
- embryological remnant of ductus arteriosum: open duct containing pulmonary trunk and arch of aorta
- important for foetal circulation allowing the blood to bypass the lungs
- ligamentous structure in adults as it closes at birth
what is the oesophagus? 2
- muscular tube
- runs from the pharynx to the stomach
what is the thoracic duct? 4
- transports lymph to venous system
- received multiple branches throughout thorax
- numerous lymph nodes associated with descending aorta
- thoracic duct and oesophagus pass through superior and posterior mediastinum
what is the phrenic nerve? 5
- originates from anterior rami of spinal nerves C3,4,5
- enters the superior mediastinum between the brachiocephalic veins and the subclavian arteries
- passa anterior to main bronchi along pericardium
- motor supply to diaphragm
- sensory supply to central region of diaphragm and parietal pleura
what is the vagus nerve? 5
- cranial nerve (CNX) so originates from the brainstem
- each enters the superior mediastinum medial to the phrenic nerve
- each gives rise to recurrent laryngeal branches to supply to the larynx
- continues into the posterior mediastinum posterior to the main bronchi
- provide parasympathetic supply via pulmonary, cardia and esophageal plexus
describe the anterior mediastinum? 5
- narrow cavity
- thymus
- pericardial-sternal ligaments
- lymph nodes and vessels
- internal thoracic cavity
what are the boundaries of the anterior mediastinum? 4
- anterior= sternum
- posterior=pericardial sac
- inferior=diaphragm
- superior= level T4/5
explain the beginning of heart development? 5
- angiogenic clusters form in the mesoderm and these canalise to forme early blood vessels
- two large blood vessels known as the heart tubes form in the cardiogenic area
- these grow nad fuse at day 21
- outflow will be arterial end
- inflow will be venous end
describe the heart tube before folding? 5
-newly formed heart tube divided into regions
-sinus venosus
-primordial atrium
primordial ventricle
-truncus arteriosus
-by day 23 it is too long for the pericardial cavity so has to fold
describe the heart tube after folding? 3
- ventricles and outflow are anterior
- atria and inflow are posterior
- septa then grow to divide the heart into 4 chambers
describe the foetal heart and its strange circulation? 4
- needs blood to bypass lungs
- foramen ovale
- ductus arteriosus
- small amount of blood needed for lung development
what is the foramen ovale?
- opening between the left and right atria in the foetus allowing oxygenated blood to bypass the lungs
- driven by higher pressure in the right atrium
