superior mediastinum Flashcards
where is the mediastinum divided into superior & inferior?
level T4/5
what are the 2 other names T4/5 is known as?
- the sternal angle
- transverse thoracic plane
what are the 3 divisions of the inferior mediastinum?
- anterior mediastinum
- middle mediastinum
- posterior mediastinum
what are the boundaries of the superior mediastinum?
- superior: superior thoracic aperture
- inferior: transverse thoracic plane
- anterior: manubrium
- posterior: T1-T4/5 vertebral bodies
- lateral: mediastinal pleura
what is contained in the superior mediastinum?
- arteries
- veins
- phrenic and vagus nerve
- oesophagus
- trachea
- thoracic duct
- thymus gland
where is the thymus gland located?
deep into the sternum and in superior and anterior mediastinum
what type of organ is a thymus gland?
lymphoid organ
what is the thymus gland supplied by?
supplied by internal thoracic arteries
what are the 3 branches of the arch of the aorta?
- brachiocephalic trunk
- left common carotid artery
- left subclavian artery
what 2 branches does the brachiocephalic trunk branch into?
- right common carotid
- right subclavian arteries
what are the 3 branches of the aorta?
- ascending aorta: left coronary artery, right coronary artery
- arch of the aorta: brachiocephalic trunk, left common carotid artery, left subclavian artery
- descending aorta: posterior intercostal, bronchial arteries & lumbar arteries
what are the veins of the superior mediastinum?
- superior vena cava
- left brachiocephalic vein
- right brachiocephalic vein
- internal jugular vein
- subclavian vein
what is the ligamentum arteriosum?
an embryological remnant of the ductus arteriosus: an open duct connecting the pulmonary trunk end the arch of the aorta
what is the function of the ligamentum arteriosum?
important in fetal circulation allowing blood to bypass the immature lungs
what muscle runs posteriorly to the trachea?
the trachralis muscle
where does the trachea run?
from the larynx to bronchi
where does the oesophagus run?
runs from pharynx to stomach
what 2 features pass through the posterior and superior mediastinum?
the thoracic duct and oesophagus
what is the function of the thoracic duct?
transports lymph to venous system
where do the phrenic nerves originate from?
the anterior rami of the spinal nerves C3, C4 and C5
where do the phrenic nerves enter the superior mediastinum?
between the brachiocephalic veins and subclavian arteries
what is the function of the phrenic nerves?
motor supply and sensory supply to the diaphragm and sensory supply to the parietal pleura
what type of nerve is a vagus nerve?
a cranial nerve
where do the vagus nerves enter the superior mediastinum?
just medially to the phrenic nerve
what do the vagus nerves give rise to?
give rise to a recurrent laryngeal branch to supply the larynx
what is the function of the vagus nerve?
provides parasympathetic supply via pulmonary, cardiac and oesophageal plexi
what is contained in the anterior mediastinum?
- thymus gland in children which atrophied in the adult and is replaced by fatty tissue
- pericardial-sternal ligaments
- lymph nodes and vessels
- internal thoracic artery
what are the boundaries of the anterior mediastinum?
- sternum anteriorly
- pericardial sac posteriorly
- diaphragm inferiorly
- level T4/5 superiorly
how does the heart develop?
- angiogenic clusters form in the mesoderm and these canalise to form early blood vessels
- 2 large blood vessels known as the heart tubes form in the cardiogenic area
- the paired heart tubes grow and fuse at approximately day 21
what are the regions of the newly formed heart tube called?
- sinus venosus
- primordial atrium
- primordial ventricle
- truncus arteriosus
what day is the heart tube too long so then folds?
day 23
what does the folding of the heart tube result in?
- ventricles and outflow tracks positioned anteriorly
- arteries and veins posteriorly
what grows to divide the heart into 4 chambers?
the septa
what are the 2 distinct features of a foetal heart that allows blood to bypass the lungs?
foramen ovals and ductus arteriosus
what is the foramen ovale?
opening between the right and left atria in the first us and allow oxygenated blood to bypass the lungs
what is the fossa ovalis?
the embryological remain at the foramen ovale which closes after birth
what is the ligamentum arteriosum?
the embryological remnant of the ductus arteriosus: an open duct between the pulmonary trunk and aortic arch which fills after birth
