Lecture 2: Superior Mediastinum Flashcards
where does the superior and inferior mediastinum divide
- level T4/5
- aka sternal angle
- aka transverse thoracic plane
what is the anterior mediastinum
space between the sternum and heart
what is the middle mediastinum
heart and pericardium
what is the posterior mediastinum
things from superior mediastinum
what is the superior boundary of the superior mediastinum
superior thoracic aperture which is
- manubrium
- costal cartilage of rib 1
- rib 1
- T1
what is the anterior border of the superior mediastium
manubrium
what is the posterior border of the superior mediastinum
T1 - T4/5 vertebral bodies
what is the lateral boundary of the superior mediastinum
mediastinal pleura
what are the contents of the superior mediastinum
- arch of aorta and branches
- brachiocephalic veins
- superior vena cava
- vagus and phrenic nerves
- oesophagus
- trachea
- thoracic duct
- part of thymus gland
where is the thymus gland located and what is it suppled by
- right underneath sternum, between sternum and heart
- after puberty, it atrophies and is replaced by fat
- supplied by internal thoracic artery
what are the branches of the aorta in the superior mediastinum
- brachiocephalic trunk, which bifurcates to right common carotid and subclavian
- left common carotid artery
- left subclavian artery
what are the branches of the ascending aorta
left and right coronary artery
what are the branches of the descending aorta
- posterior intercostal arteries
- bronchial arteries
- lumbar arteries
what is the ligamentum arteriosum
- a ligament that connects the pulmonary trunk to the arch of aorta
- remnant of ductus arteriosus
what is the thoracic duct
- longest lymphatic vessel
- in superior and posterior mediastinum
what do the phrenic nerve originate from
anterior rami of spinal nerves C3, C4 and C5
where do the phrenic nerves enter the superior mediastinum from and travel to
- between brachiocephalic veins and subclavian arteries
- then pass anterior to main bronchi along pericardium to diaphragm
what do the phrenic nerves supply
- motor supply to diaphragm
- sensory supply to diaphragm and parietal pleura
what is another name for the vagus nerve
cranial nerve X
what do the vagus nerves branch into
right and left recurrent laryngeal nerves
what do the vagus nerves supply
parasympathetic supply via pulmonary, cardiac and oesophageal plexi
what does the anterior mediastinum contain
- thymus gland
- pericardial-sternal ligaments
- parasternal lymph nodes and vessels
- internal thoracic artery
what are the boundaries of the anterior mediastinum
anterior: sternum
posterior: pericardial sac
inferior: diaphragm
superior: level T4/5
where does the heart develop from
- angiogenic clusters form in the mesoderm and canalise to form early blood vessels
- two heart tubes form in cardiogenic area
- fuse at day 21
what are the regions of the heart tube before folding
- sinus venosus
- primordial atrium
- primordial ventricle
- truncus arteriosus
when does the heart start to fold
- day 23
- ventricles and outflow tracks positioned anteriorly
- atria and veins posteriorly
which features of the foetal heart allow blood to bypass the lungs
- ductus arteriosus
- foramen ovale
how does the foramen ovale develop
- septum primum forms, leaving osteum primum
- septum primum and osteum primum fuse, leaving ostium secundum
- septum secundum forms, leaving foramen ovale as a hole
- after birth, leaves fossa ovalis
