superior mediastinum

Question 1

where is the mediastinum divided into superior & inferior?

Answer 1

level T4/5

Question 2

what are the 2 other names T4/5 is known as?

Answer 2

• the sternal angle

- transverse thoracic plane

Question 3

what are the 3 divisions of the inferior mediastinum?

Answer 3

• anterior mediastinum
• middle mediastinum
• posterior mediastinum

Question 4

what are the boundaries of the superior mediastinum?

Answer 4

• superior: superior thoracic aperture
• inferior: transverse thoracic plane
• anterior: manubrium
• posterior: T1-T4/5 vertebral bodies
• lateral: mediastinal pleura

Question 5

what is contained in the superior mediastinum?

Answer 5

• arteries
• veins
• phrenic and vagus nerve
• oesophagus
• trachea
• thoracic duct
• thymus gland

Question 6

where is the thymus gland located?

Answer 6

deep into the sternum and in superior and anterior mediastinum

Question 7

what type of organ is a thymus gland?

Answer 7

lymphoid organ

Question 8

what is the thymus gland supplied by?

Answer 8

supplied by internal thoracic arteries

Question 9

what are the 3 branches of the arch of the aorta?

Answer 9

• brachiocephalic trunk
• left common carotid artery
• left subclavian artery

Question 10

what 2 branches does the brachiocephalic trunk branch into?

Answer 10

• right common carotid

- right subclavian arteries

Question 11

what are the 3 branches of the aorta?

Answer 11

• 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

Question 12

what are the veins of the superior mediastinum?

Answer 12

• superior vena cava
• left brachiocephalic vein
• right brachiocephalic vein
• internal jugular vein
• subclavian vein

Question 13

what is the ligamentum arteriosum?

Answer 13

an embryological remnant of the ductus arteriosus: an open duct connecting the pulmonary trunk end the arch of the aorta

Question 14

what is the function of the ligamentum arteriosum?

Answer 14

important in fetal circulation allowing blood to bypass the immature lungs

Question 15

what muscle runs posteriorly to the trachea?

Answer 15

the trachralis muscle

Question 16

where does the trachea run?

Answer 16

from the larynx to bronchi

Question 17

where does the oesophagus run?

Answer 17

runs from pharynx to stomach

Question 18

what 2 features pass through the posterior and superior mediastinum?

Answer 18

the thoracic duct and oesophagus

Question 19

what is the function of the thoracic duct?

Answer 19

transports lymph to venous system

Question 20

where do the phrenic nerves originate from?

Answer 20

the anterior rami of the spinal nerves C3, C4 and C5

Question 21

where do the phrenic nerves enter the superior mediastinum?

Answer 21

between the brachiocephalic veins and subclavian arteries

Question 22

what is the function of the phrenic nerves?

Answer 22

motor supply and sensory supply to the diaphragm and sensory supply to the parietal pleura

Question 23

what type of nerve is a vagus nerve?

Answer 23

a cranial nerve

Question 24

where do the vagus nerves enter the superior mediastinum?

Answer 24

just medially to the phrenic nerve

Question 25

what do the vagus nerves give rise to?

Answer 25

give rise to a recurrent laryngeal branch to supply the larynx

Question 26

what is the function of the vagus nerve?

Answer 26

provides parasympathetic supply via pulmonary, cardiac and oesophageal plexi

Question 27

what is contained in the anterior mediastinum?

Answer 27

- 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

Question 28

what are the boundaries of the anterior mediastinum?

Answer 28

- sternum anteriorly - pericardial sac posteriorly - diaphragm inferiorly - level T4/5 superiorly

Question 29

how does the heart develop?

Answer 29

- 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

Question 30

what are the regions of the newly formed heart tube called?

Answer 30

- sinus venosus - primordial atrium - primordial ventricle - truncus arteriosus

Question 31

what day is the heart tube too long so then folds?

Answer 31

day 23

Question 32

what does the folding of the heart tube result in?

Answer 32

- ventricles and outflow tracks positioned anteriorly | - arteries and veins posteriorly

Question 33

what grows to divide the heart into 4 chambers?

Answer 33

the septa

Question 34

what are the 2 distinct features of a foetal heart that allows blood to bypass the lungs?

Answer 34

foramen ovals and ductus arteriosus

Question 35

what is the foramen ovale?

Answer 35

opening between the right and left atria in the first us and allow oxygenated blood to bypass the lungs

Question 36

what is the fossa ovalis?

Answer 36

the embryological remain at the foramen ovale which closes after birth

Question 37

what is the ligamentum arteriosum?

Answer 37

the embryological remnant of the ductus arteriosus: an open duct between the pulmonary trunk and aortic arch which fills after birth