posterior mediastinum Flashcards
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
contents of the posterior mediastinum
oesophagus descending aorta thoracic duct azygous venous system posterior mediastinal lymph nodes thoracic sympathetic trunks splancnic nerves
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
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
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
clinical relevance of constrictions
caustic things damage the oesophagus here and burn it
they sit there for a longer time and damage it
arteries of the oesophagus
from the aorta - right next to oesophagus - oesophageal arteries
veins of the oesophagus
azygos - from back - loop over hilum and enter SVC
hemiazygos and accessory hemiazygos
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
location of azygous vein
above bifurcation of the trachea -T4
posterior to the aorta and the pulmonary trunk
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
phrenic nerve
anterior to the lung hilum
along the pericardium
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
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
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
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
features of the sympathetic chain
postganglionic cell bodies in enlargements
superior enlargement - middle cervical enlargement
inferior - stellate ganglion
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
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
patheyas to viscera - symp chain
synapse in unpaired ganglia by the viscera (not in the chain)
rami in the sympathetic chain
white ramus communicans - myelinated
grey - unmyelinated
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
what does the vagus nerve synapse in
the ganglia or plexus
plexus - mix of SNS and PNS
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
describe the pulmonary plexus
Sympathetic nerves dilate the bronchioles
Parasympathetic (vagus) nerves constrict the bronchioles
relationship between the vagus and the ligamentu, arteriosum
the vagus wraps around the ligamentum arteriosum = recurrent laryngeal nerve
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
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
describe the oesopjhageal plexus
Sympathetic afferents relay pain sensations from the oesophagus
Parasympathetic afferents (vagus) senses normal physiological information from the oesophagus
secretory action
describe the recurrent laryngeal nerves
L - over aortic arch
R over R subclavian artery - discrepancy in length R not at level of manubrium
action of vagus nerve
PNS
enteroceptor
no autonomic supply ot the body wall
