Lecture 2: Superior Mediastinum

Question 1

where does the superior and inferior mediastinum divide

Answer 1

• level T4/5
• aka sternal angle
• aka transverse thoracic plane

Question 2

what is the anterior mediastinum

Answer 2

space between the sternum and heart

Question 3

what is the middle mediastinum

Answer 3

heart and pericardium

Question 4

what is the posterior mediastinum

Answer 4

things from superior mediastinum

Question 5

what is the superior boundary of the superior mediastinum

Answer 5

superior thoracic aperture which is

• manubrium
• costal cartilage of rib 1
• rib 1
• T1

Question 6

what is the anterior border of the superior mediastium

Answer 6

manubrium

Question 7

what is the posterior border of the superior mediastinum

Answer 7

T1 - T4/5 vertebral bodies

Question 8

what is the lateral boundary of the superior mediastinum

Answer 8

mediastinal pleura

Question 9

what are the contents of the superior mediastinum

Answer 9

• arch of aorta and branches
• brachiocephalic veins
• superior vena cava
• vagus and phrenic nerves
• oesophagus
• trachea
• thoracic duct
• part of thymus gland

Question 10

where is the thymus gland located and what is it suppled by

Answer 10

• right underneath sternum, between sternum and heart
• after puberty, it atrophies and is replaced by fat
• supplied by internal thoracic artery

Question 11

what are the branches of the aorta in the superior mediastinum

Answer 11

• brachiocephalic trunk, which bifurcates to right common carotid and subclavian
• left common carotid artery
• left subclavian artery

Question 12

what are the branches of the ascending aorta

Answer 12

left and right coronary artery

Question 13

what are the branches of the descending aorta

Answer 13

• posterior intercostal arteries
• bronchial arteries
• lumbar arteries

Question 14

what is the ligamentum arteriosum

Answer 14

• a ligament that connects the pulmonary trunk to the arch of aorta
• remnant of ductus arteriosus

Question 15

what is the thoracic duct

Answer 15

• longest lymphatic vessel

- in superior and posterior mediastinum

Question 16

what do the phrenic nerve originate from

Answer 16

anterior rami of spinal nerves C3, C4 and C5

Question 17

where do the phrenic nerves enter the superior mediastinum from and travel to

Answer 17

• between brachiocephalic veins and subclavian arteries

- then pass anterior to main bronchi along pericardium to diaphragm

Question 18

what do the phrenic nerves supply

Answer 18

• motor supply to diaphragm

- sensory supply to diaphragm and parietal pleura

Question 19

what is another name for the vagus nerve

Answer 19

cranial nerve X

Question 20

what do the vagus nerves branch into

Answer 20

right and left recurrent laryngeal nerves

Question 21

what do the vagus nerves supply

Answer 21

parasympathetic supply via pulmonary, cardiac and oesophageal plexi

Question 22

what does the anterior mediastinum contain

Answer 22

• thymus gland
• pericardial-sternal ligaments
• parasternal lymph nodes and vessels
• internal thoracic artery

Question 23

what are the boundaries of the anterior mediastinum

Answer 23

anterior: sternum
posterior: pericardial sac
inferior: diaphragm
superior: level T4/5

Question 24

where does the heart develop from

Answer 24

• angiogenic clusters form in the mesoderm and canalise to form early blood vessels
• two heart tubes form in cardiogenic area
• fuse at day 21

Question 25

what are the regions of the heart tube before folding

Answer 25

• sinus venosus
• primordial atrium
• primordial ventricle
• truncus arteriosus

Question 26

when does the heart start to fold

Answer 26

• day 23
• ventricles and outflow tracks positioned anteriorly
• atria and veins posteriorly

Question 27

which features of the foetal heart allow blood to bypass the lungs

Answer 27

• ductus arteriosus

- foramen ovale

Question 28

how does the foramen ovale develop

Answer 28

• 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