L2: Superior mediastinum

Question 1

what attaches to the sternal angle?

Answer 1

2nd rib
*useful landmark

The sternal angle is an important clinical landmark for identifying many other anatomical points: It marks the point at which the costal cartilages of the second rib articulate with the sternum. This is particularly useful when counting ribs to identify landmarks as rib one is often impalpable.

Question 2

boundaries of mediastinum

Answer 2

anterior: manubrium and sternum
posterior: vertebral column(thoracic vertebrae)
superior: superior thoracic aperture
inferior: inferior thoracic aperture

Lateral: lungs

Question 3

what divides superior and inferior mediastinum?

*goes through the sternal angle

Answer 3

transthoracic plane
(transverse thoracic plane)

Question 4

sternal angle is also called…

Answer 4

angle of Louis

Question 5

transthoracic plane is at lvl…?

Answer 5

TIV/V

Question 6

what happens at transthoracic plane (T4-5)

Answer 6

-trachea bifurcates(corena)
-concave arch/surface of the aorta( inferior surface)
-Pulmonary trunk bifurcates into 2 pulmonary arteries

-Arch of azygous vein( joins SVC) at this plane

-Ligamentum arteriosum sits on trans-thoracic plane

-Thoracic duct switching over from right to left to join the left braciocephalic vein junction

-Phrenic and vagus nerves form cardiac plexus at this lvl

Question 7

inferior mediastinum separates into 3 parts:..

Answer 7

Anterior, middle, and posterior mediastinum

Question 8

a lot of “pipes” run through which mediastinum?

Answer 8

posterior

Question 9

are pleural cavities part of the mediastinum?

Answer 9

no

Question 10

what is the sensitive area of trachea at its bifurcation point called?

Answer 10

corena

Question 11

what is the sensitive area of trachea at its bifurcation point called?

Answer 11

corena

Question 12

what is the 1st branch of the aorta?

Answer 12

coronary arteries

Question 13

3 branches coming off the aortic arch

Answer 13

brachiocephalic artery
L. common carotid artery
L. subclavian artery

Question 14

brachiocephalic artery divides into…

Answer 14

R. subclavian a
R. common carotid a

Question 15

R and L subclavian arteries turn into…

Answer 15

axillary arteries

Question 16

what are the 2 arteries commonly targeted for coronary bypass surgery?

Answer 16

RITA: right internal thoracic a
LITA: left internal thoracic a

Question 17

what arteries come off the descending aorta?

Answer 17

posterior intercostal a

Question 18

what 2 veins come together to form SVC?

Answer 18

R. and L brachiocephalic veins

Question 19

R and L brachiocephalic veins split into?

Answer 19

R. internal jugular
R subclavian v

and

L internal jugular
L subclavian v

Question 20

external jugular veins come off…?

Answer 20

(R and L) subclavian veins

Question 21

Answer 21

Question 22

what roots/lvls does the phrenic nerve come from?

Answer 22

C3, C4. C5

Question 23

phrenic nerve

Answer 23

mixed nerve( both somatic and autonomic)

-can control diaphragm ( singing)

but cannot hold breath until you die, as CO2 accumulates in the blood the autonomic side overrides the somatic

Question 24

phrenic nerve runs along which muscle in the neck?

Answer 24

anterior scalene

Question 25

Vagus nerve: relationship to carotid artery and internal jugular vein in the neck

Answer 25

Vagus nerve runs posterior to carotid artery and medial to internal jugular vein

Runs in the carotid sheath
together with the 2 vessels

enters the thoracic cavity together with the carotid artery

Question 26

at what point do the nerves cross over?

Answer 26

~1st rib

Phrenic nerve starts off more posterior than the vagus nerve. Runs along the anterior scalene, enters the thoracic inlet between the subclavian artery and vein.

When in the thoracic cavity: phrenic nerve now runs anterior to vagus. Runs over the aorta( on L side) runs between pericardium and parietal pleura. On top of parietal pericardium. Supplies the pericardium. Eventually the left phrenic nerve pierces through the diaphragm and innervates it.

The right phrenic nerve runs on top of R. brachiocephalic vein and on top of SVC INFRONT OF THE HILUM OF THE LUNG

Vagus nerve comes down on the carotid arteries and pass underneath a vein on both sides( L-superior intercostal vein, R- azygous vein)
Runs behind the hilum of the lung and forms the cardiopulmonary plexus

Question 27

what are the important branches of vagus nerve?

Answer 27

R. and L. recurrent laryngeals

Question 28

voice change: explain clinical importance

Answer 28

people who get aneurisms of aorta: can stretch and affect the recurrent laryngeal branches( coming off the vagus nerve)

Or tumours in the L bronchus can compress as well
mainly the L side affected

Question 29

why use central lines and not peripheral?

Answer 29

Reasons for central venous lines:

Cannot always use peripheral veins
-e.g. infant- small peripheral veins+ dehydration makes them shrink even more-> hard to access peripheral veins

Can administer medicines, equipment (pressure probes, oximeters etc).
Useful when administering cytotoxic medicine-> cytotoxic medicines can destroy the vessels themselves-> by injecting into a big vessel with big flow can dilute the medicines quicker (e.g. chemo dripped in very slowly)

Question 30

things to consider when selecting central veins

Answer 30

Things to consider when selecting a central vein for a central line:
-Ease of access(Ultrasound) and user experience.
-What else is happening(e.g. if CPR administered- body is moving a lot-> cannot always access the best vein)
-Risk of arterial puncture, lungs, nerves( and other surrounding tissues)
-Bleeding containment( need to apply pressure once you have pulled the tube out)
-Infection risk
-Long term placement? (comfort/ clotting)

Question 31

+ and - of external jugular vein( for central lines)

Answer 31

Question 32

+ and - of femoral vein( for central lines)

Answer 32

Question 33

+ and - of internal jugular vein( for central lines)

Answer 33

Question 34

+ and - of subclavian vein( for central lines)

Answer 34