posterior mediastinum

Question 1

what is the mediastinum

Answer 1

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

Question 2

contents of the posterior mediastinum

Answer 2

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

Question 3

nerves of the inferior mediastinum

Answer 3

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

Question 4

course of oesophagus

Answer 4

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

Question 5

constrictions of oesophagus

Answer 5

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

Question 6

clinical relevance of constrictions

Answer 6

caustic things damage the oesophagus here and burn it

they sit there for a longer time and damage it

Question 7

arteries of the oesophagus

Answer 7

from the aorta - right next to oesophagus - oesophageal arteries

Question 8

veins of the oesophagus

Answer 8

azygos - from back - loop over hilum and enter SVC

hemiazygos and accessory hemiazygos

Question 9

azygous vessels

Answer 9

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

Question 10

location of azygous vein

Answer 10

above bifurcation of the trachea -T4

posterior to the aorta and the pulmonary trunk

Question 11

course of vagus nerve

Answer 11

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

Question 12

phrenic nerve

Answer 12

anterior to the lung hilum

along the pericardium

Question 13

branches of vagus nerve

Answer 13

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

Question 14

function of sympathetic chains

Answer 14

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

Question 15

splanchnic nerves

Answer 15

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

Question 16

fibres in the sympathetic ganglion

Answer 16

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

Question 17

features of the sympathetic chain

Answer 17

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

Question 18

course of thoracic duct

Answer 18

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

Question 19

horns between T1-L2

Answer 19

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

Question 20

patheyas to viscera - symp chain

Answer 20

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

Question 21

rami in the sympathetic chain

Answer 21

white ramus communicans - myelinated

grey - unmyelinated

Question 22

where do the sympathetic neurons synapse

Answer 22

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

Question 23

what does the vagus nerve synapse in

Answer 23

the ganglia or plexus

plexus - mix of SNS and PNS

Question 24

describe the sympathetic nerves to the lungs and heart

Answer 24

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

Question 25

describe the pulmonary plexus

Answer 25

Sympathetic nerves dilate the bronchioles

Parasympathetic (vagus) nerves constrict the bronchioles

Question 26

relationship between the vagus and the ligamentu, arteriosum

Answer 26

the vagus wraps around the ligamentum arteriosum = recurrent laryngeal nerve

Question 27

describe the cardiac plexus

Answer 27

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

Question 28

summarise the course of the vagal nerves

Answer 28

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

Question 29

describe the oesopjhageal plexus

Answer 29

Sympathetic afferents relay pain sensations from the oesophagus

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

secretory action

Question 30

describe the recurrent laryngeal nerves

Answer 30

L - over aortic arch

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

Question 31

action of vagus nerve

Answer 31

PNS
enteroceptor
no autonomic supply ot the body wall