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1

what is the mediastinum

thick midline partition
anterior to thoracic vertebrae to the sternum
from superior thoracic aperture to inferior thoracic aperture
divided into superior and inferior
inferior: anterior, middle and posterior - divided by the pericardium

2

contents of the posterior mediastinum

oesophagus
descending aorta
thoracic duct
azygous venous system
posterior mediastinal lymph nodes
thoracic sympathetic trunks
splancnic nerves

3

nerves of the inferior mediastinum

phrenic -C3,4,5 - anterior to lung root, cross pericardium to diaphragm
vagi - posterior to lung root form plexus following oesophagus to abdomen, branch to lung and heart on the way
sympathetic trunks - lie on each side of the posterior mediastinum

4

course of oesophagus

runs between pharynx at the back of the throat
begins at C7
ends at stomach - T11
R of aorta above T7
bends anteriorly at T7
deviates to L at T7
anterior to aorta - T7
passes through diaphragm T10

5

constrictions of oesophagus

4
junction of oesophagus with pharynx - C7
when crossed by aortic arch - squashed posteriorly
when compressed by L main bronchus
at oesophageal hiatus - through the diaphragm

6

clinical relevance of constrictions

caustic things damage the oesophagus here and burn it
they sit there for a longer time and damage it

7

arteries of the oesophagus

from the aorta - right next to oesophagus - oesophageal arteries

8

veins of the oesophagus

azygos - from back - loop over hilum and enter SVC
hemiazygos and accessory hemiazygos

9

azygous vessels

sometimes travel in the middle of the chest/to the R
drain posterior wall of the chest and the upper abdomen and posterior mediastinal regions
hemiazygos and accessory hemiazygos on L - cross thoracic vertebral bodies to join azygos on R
arch over R lung root to join SVC

10

location of azygous vein

above bifurcation of the trachea -T4
posterior to the aorta and the pulmonary trunk

11

course of vagus nerve

front of aorta
travels posterior to the lung hilum
R vagus nerve - posterior - becomes posterior vagal trunk
L vagus nerve - anterior - becomes anterior vagal trunk
at ligamentum arteriosum L vagus nerve curves up and becomes L recurrent laryngeal nerves - supplies skeletal muscle of the larynx
for R - goes around the R subclavian artery
from 2/3 along colon to mid and hind gut

12

phrenic nerve

anterior to the lung hilum
along the pericardium

13

branches of vagus nerve

to chest and abdomen - parasympathetic - control smooth and cardiac muscle and glands of gut and airways
sensory from gut and lungs
recurrent laryngeal - voluntary - supply skeletal muscle of pharynx - damage = voice change
contains fibres from different areas of the brainstem

14

function of sympathetic chains

receive branches from spinal nerves T1-L2 - from intermediate horn between posterior, dorsal and ventral horn
distribute fibres to sm and glands through the body
nerves to thoracic wall synapse in the ganglia of trunk
nerves to viscera - pass through, synapse in local ganglia
pain fibres from viscera to CNS
parasympathetic and sympathetic

15

splanchnic nerves

fibres from T5-12 reach abdomen
T5-9 - greater splanchnic nerve
9 and 10 - lesser splanchnic nerve
12 - least splanchnic nerve
sensory to GI

16

fibres in the sympathetic ganglion

nerves can go up or down - may not synapse in the ganglion
for heart and lungs synapse in chain or on way to organ - microganglia, plexus on heart - preaortic ganglia

17

features of the sympathetic chain

postganglionic cell bodies in enlargements
superior enlargement - middle cervical enlargement
inferior - stellate ganglion

18

course of thoracic duct

begins below diaphragm at cisternae chyli - L2
between oesophagus and aorta on R
cross behind oesophagus to L between T7-4
drain into brachiocephalic vein

19

horns between T1-L2

there is an intermediate horn or intermediolateral horn between ventral and dorsal - cell body give rise to symp ns here - fibres go with motor neuron - efferent

20

patheyas to viscera - symp chain

synapse in unpaired ganglia by the viscera (not in the chain)

21

rami in the sympathetic chain

white ramus communicans - myelinated
grey - unmyelinated

22

where do the sympathetic neurons synapse

in chain - then enter peripheral nerve to the skin- grey
in prevertebral gangion - innervate the viscera
move uop or downthe chain

23

what does the vagus nerve synapse in

the ganglia or plexus
plexus - mix of SNS and PNS

24

describe the sympathetic nerves to the lungs and heart

T2-4
cervical and upper thoracic ganglia of sympathetic trunk
synapse in microganglia in pul and cardiac plexuses

25

describe the pulmonary plexus

Sympathetic nerves dilate the bronchioles

Parasympathetic (vagus) nerves constrict the bronchioles

26

relationship between the vagus and the ligamentu, arteriosum

the vagus wraps around the ligamentum arteriosum = recurrent laryngeal nerve

27

describe the cardiac plexus

Sympathetic efferents increase heart rate and force of contraction

Parasympathetic efferents (vagus) decrease heart rate via the pacemaker tissue and constrict coronary arteries

Sympathetic afferents relay pain sensations from the heart

Parasympathetic afferents (vagus) relay blood pressure and chemistry information from the heart

28

summarise the course of the vagal nerves

X - from medulla - leave skull through jugular rforamana
descend neck poterolateral to common carotid
LV anterior to arortic arch, posterior to L lung root
R vagus - posterior to R lung root
separate to form oesophageal plexuses

29

describe the oesopjhageal plexus

Sympathetic afferents relay pain sensations from the oesophagus

Parasympathetic afferents (vagus) senses normal physiological information from the oesophagus

secretory action

30

describe the recurrent laryngeal nerves

L - over aortic arch
R over R subclavian artery - discrepancy in length R not at level of manubrium