Superior and Posterior Mediastinum

Question 1

MS divisions

Answer 1

• superior

- inferior (ant, med, post)

Question 2

extent of superior MS

Answer 2

from the thoracic inlet to diaphragm and from sternum to 12th thor vert
-extends posteriorly to T4-5 post border

Question 3

landmark btwn sup and inf MS

Answer 3

sternomanubrium jt

Question 4

sup MS contents

Answer 4

-thymus gland
SVC and great vv
arch of arota
vagus and phrenic nn
trachea and esophagus
thor duct

Question 5

thymus gland

Answer 5

post to manubrium, ant to brachiocephalic vv, atrophies after puberty

Question 6

where does L brachiocephalic v cross?

Answer 6

anteriorly to trachea

Question 7

aortic arch

Answer 7

• begins and ends at sternal angle (T4-5)
• arches over L main bronchus and pulm tr
• gives rise to
  1. brachiocephalic tr
  2. L common carotid a
  3. L subclavian

Question 8

Vagus N

Answer 8

originates lat to olive in medulla

descends post to root of lung

Question 9

phrenic n

Answer 9

origin C3-C5
travel w/ pericardiacophrenic a and v
motor and sensory (somatic to diaphragm)
descend ant to root of lung

Question 10

trachea

Answer 10

• descends immediately ant to esophagus
• bifurcates at inf limit of sup MS (carina)
• numerous lymph nodes found at the corina

Question 11

carina

Answer 11

• inf stem to bifurcation

- foreign bodies aspirate to R main bronchus (shorter and wider than L)

Question 12

esophagus

Answer 12

• begins C6 (base of pharynx)
• descends immediately post to trachea
• pierces dia at esophageal hiatus

Question 13

esophageal hernias

Answer 13

type I (sliding hiatal hernia): stomach slides freely into thorax, most common, often asymptomatic
type II (paraesophageal hernia): fundus, often fixed in position risking gastric blood supply

Question 14

what creates retropharyngeal space

Answer 14

ant: buccopharyngeal fascia
post: prevertebral fascia

Question 15

post MS contents

Answer 15

• esophagus and esophageal plexus
• aztgos system of vv
• descending aorta
• thor duct
• thoracic splanchnic nn

Question 16

esophagus and esophageal plexus

Answer 16

-vagus nn join to form plexus around eso (near dia plexus reforms vagal trs)
L vagus n: ant vagal tr
R vagus n: post vagal tr
*bc gut rotation

Question 17

azygos system of vv

Answer 17

• venous drainage for thorax
• azygos v: drains intercostal vv from R side of thor, arches over R sup bronchus to drain into SVC
• hemiazygos and accessory hemiazygos vv: drain L thorax

Question 18

descending aorta

Answer 18

• just L of eso
• gives rise to post intercostal aa supplying thorax
• supplies brs to trachea, bronchi, eso

Question 19

thoracic duct

Answer 19

• post to eso and ant to vertebral bodies
• located btwn azygos v and descending aorta (thor)
• passes thru dia w/ desc aorta
• drains lymph from entire body below dia
• enters venous angle btwn L subclavian v and L IJV

Question 20

chylothorax

Answer 20

accumulation of lymph in pleural cavity

• results from torn or leaking thor duct
• often from lymphoma/trauma during thor surgery
• a type of pleural effusion visible on chest films

Question 21

symp chain gang and thor splanchnic nn

Answer 21

symp trs are lat of vert bodies and pass posteriorly to dia to enter abdomen

Question 22

2 types of brs from symp chain gang

Answer 22

1. postgang symp to thor viscera

2. pregang symp innervation to abdomen greater splanchnic nn: synapse at ciliac gang, lesser: SMA, least: aorticorenal

Question 23

thor autonomic nn

Answer 23

symp: originate from T1-T5 (serve thor cavity)
parasymp: originate from CN X
commingle to form thor plexus (cardiac, pulm: along primary bronchi, eso)