Space posterior to pericardium; continuous with tissue spaces behind pretracheal fascia and in front of prevertebral fascia.
- posterior boundary is T5-T12
- anterior boundary is pericardium, sloping diaphragm
- contents: oesophagus, thoracic aorta, azygos system, thoracic duct, lymph nodes
Commences at lower border of T4; initially to L of midline ¨ exits posterior mediastinum at T12 level in midline between crura (behind median arcuate ligament)
9 Posterior intercostal arteries given off each side, one pair of subcostal arteries
Visceral branches to bronchi, oesophagus (4-5 total) and some small pericardial / phrenic branches.
From lower border cricoid cart (C6) ¨ via oesophageal hiatus (T10) ¨ ends at T11. Length = 25cm.
Begins in midline -
heads L into
neck/superior mediastinum (but is midline at thoracic
inlet) -->
R below tracheal
bifurcation -->
midline again at T5 -->
deviates L at T7 ¨
2.5 cm L at hiatus
(meets stomach at level of the 7th costal
cartilage). (Pl220 / 228 shows curve)
|
Points
of narrowing: |
Distance
from incisor teeth: |
|
Upper
oesophageal sphincter |
15cm
(narrowest) |
|
Aortic
arch |
22cm ~t3 |
|
L main bronchus |
27cm ~T4-5 |
|
Diaphragm |
38cm T10 |
First 2-3cm closely related to larynx; usually left behind in ÒtotalÓ oesophagectomy.
RLN: in tracheo-oesophageal groove in 50%, behind it in 10%, anterior in 40%.
Laterally: thyroid lobes with deep cervical fascia in between; inferior thyroid arteries. Thoracic duct lies to L at level of thoracic inlet - more lateral higher in neck.
Posteriorly: vertebral bodies,
longus colli with prevertebral fascia in between.
Access: curves to left, so open left chest; divide
omohyoid and middle thyroid vein; approach between carotid
sheath and straps / thyroid; prevertebral fascia is posterior;
beware RLN in traceho-oesophageal groove.
Anteriorly: trachea, L main bronchus and R pulmonary artery; below that pericardium, L atrium.
Laterally: to L = arch & desc aorta (cf in abdo aorta is to R), L RLN above aortic arch, pleura below level of arch;
to R = vertebral
bodies and pleura along whole length, except where aygos
arches forward --> SVC. Hemiazygos to L in lower
chest, then accessory hemiazygos to L in mid to upper chest
(emptyies to L brachiocphalic vein)
Vagus nerves cross laterally to form plexus
around mid-oesophagus -->
anterior (mainly L) and
post (mainly R)
trunks.
Posteriorly: Thoracic duct (from
R -->
L) intimitely related, R intercostal arteries, occasionally
R subclavian
artery may cross posteriorly.
Aorta in lower chest.
Approach: From R side azygos v. is in way; can
divide. Push lung root away by dividing inferior plmonary
ligament
From L, bit more
difficult; but accessible in 2 triangles where beneath
pleuroa only: inferior trianble between diphragm,
pericardium and aorta; superior between subclavian, vertebra
and aorta (fig 20.3 in Jamieson; p108)
Mucosa = non-keratinising strat squamous overlying lamina propria and muscularis mucosa.
- gastric columnar epithelium may line lower oesophagus but if >3cm up ¨ abnormal.
Submucosa = strongest layer of wall.
Muscle layers (222) = outer longitudinal
(connected at top by 2 tendinous bands to inferior constrictor
border) + inner circular (continuation of
cricopharyngeus).
Skeletal muscle in upper oesophagus (voluntary;
allows rapid contraction for safe passage of food); smooth
muscle in lower portion; mixed in the middle (a variable amount
of sm in the proximal oesophagus also).
- shortening of longitudinal layer important in development of sliding HH.
Mucosal and muscle layers are only loosely connected, facilitating myotomy at any level.
3 cm zone of higher pressure acts as a physiological sphincter.
Skeletal muscle: RLN (cell bodies = nucleus ambiguus) and sympathetics from middle cervical ganglia;
Smooth muscle: parasympathetic from vagus (cell bodies = dorsal motor nuclei), secretory-motor; sympathetic from sympathetic trunk, Greater splanchnic nerves (forms a plexus on its surface).
- distally anterior plexus is mainly L vagal fibres, and posterior plexus R fibres.
- Pain runs with both vagal and vasomotor sympathetic supply, referred like cardiac pain.
4 Regions according to supply:
(1) cervical oesophagus: inferior thyroids
(2) thoracic oesophagus above tracheal bifurcation: bronchial arteries
(3) infratracheal oesophagus: 1-3 branches from aorta
(4) abdominal oesophagus by L gastric
Arterial supply anastomoses freely; weakest
b/n aortic and bronchial supplies. Supply vessels are small and branch close
to wall \
dissection close to oesophagus should avoid major bleeding.
Rich intramural network of anastomoses; allows continuos supply
even with mobilisation of 4-5cm of the oesophagus from its bed.\
All these arteries small and many, so tends not to be major
bleeding in oesophagectomy.
Similar to supply above & below;
(1) upper part (cervical): brachiocephalics
(2) middle part (thoracic oesophagus) ¨ azygos system.
(3) Lower part (abdominal) ¨ L gastric vein (porto-systemic anastomosis at C8 level)
Plexus of external veins communicates via perforators with submucosal venous plexuses. Subepithelial plexus of veins in lamina propria gives rise to varices, confined to lower 5cm.
(1) cervical --> deep cervical nodes
(2) thoracic --> tracheobronchial and posterior mediastinal nodes
(3) abdominal --> left gastric and coeliac nodes
Plexuses of channels in wall run
longitudinally; freely communicate. Thus cervical carcinoma may involve
coeliac nodes & lower 1/3 carcinoma
may involve cervical nodes.
Complete lymphadenectomy with oseophagectomy is controversial;
not clear demonstration of benefit for the radical approach.
Cervical approach: through L side of neck between trachea and carotid sheath (65)
Thoracic approach: R side in front of vertebral column after transecting azygous arch
- posterior intercostal vessels and thoracic duct at risk when mobilising posterior oesophagus
Abdominal: from left side above diaphragm
between pericardium in front and oesophagus behind.
Thoracoscopy
Position as for thoracotomy; place trochars close to top
of rib. Easiest between pecs and lats; fewest muscle.
Superficial wall lymph ¨ axillary nodes or parasternal nodes, few to inferior deep cervical nodes.
- deeper tissue flows through to intrathoracic lymph nodes
i) parasternal nodes: at ant ends of upper 5 intercostal spaces ¨ bronchomediastinal trunks
ii) intercostal nodes: at posterior ends of intercostal spaces. Upper ¨ thoracic duct or right lymphatic duct, lower ¨ cisterna chyli.
iii) diaphragmatic nodes: ant, lat, post groups on diaphragm; lat group receives from liver on R, ¨ parasternal and posterior mediastinal nodes
iv) Posterior mediastinal nodes behind everything beside vertebrae ¨ thoracic duct
v) Tracheobronchial nodes: (197) drain lungs, heart sup and inf groups ¨ paratracheals.
vi) Paratracheal nodes: (197) ¨ bronchomediastinal lymph trunks.
vii)
Brachiocephalic nodes: drain thyroid, thymus,
pericardium, heart, join with parasternal and paratracheal
groups to form bronchomediastinal lymph trunks
viii)
Bronchomediastinal lymph trunks: R ¨
R lymphatic trunk; L ¨
thoracic duct (or may
just open into the nearby jx of internal jugular and
subclavian veins.
Arises from union of paired lumbar trunks & single intestinal trunk (= this union is the cisterna chyli, which gives thoracic duct) at T12, between aorta and azygous vein (180)
Passes through R crus to R of aorta --> then to R of oesophagus
Inclines L at T5 (behind oesophagus), reaching L side of oesophagus by sup mediastinum, anterior to intercostal branches of aorta, but posterior to the aortic arch and L subclavian.
Arches over dome of L pleura (superficial to subclavian artery -see 220, lateral to vagus, but medial to phrenic) ¨ enters confluence of IJV and subclavian on L.
Has valves (not effective ones at its termination though). Receives left jugular, subclavian and usually bronchomediastinal lymph trunks.
-
damage during oesophagectomy-->
chylothorax; us. presents after enteral nutrition resumes;
causes immune depletion; can give 100mL of cream to confirm
milky
--> often will need direct repair or ligation above and
below; alternative channels are many so no concern with
ligation.
Right lymphatic duct drains right intercostals, and
right bronchomediastinal, and may receive right jugular and
subclavian trunks. ¨
opening of right brachiocephalic vein (may remain separate)
Drain thoracic region and upper lumbar region. Receives posterior intercostals and lumbar veins
Azygos on R, hemiazygos on L
- formed by union of ascending lumbar and subcostal veins below diaphragm.
Azygos vein enters thorax via right crus at level of aortic opening
- passes upwards on vertebral bodies, posterior to the oesophagus
- arches over hilum of right lung at T4 to enter SVC
- receives lower 8 R intercostal veins, superior intercostal vein, bronchial veins from right lung, and some middle oesophageal veins. Hemiazygos vein meets it at T7-8.
Hemiazygos lies longitudinally on left side of the thoracic vertebra. There are two (inferior = hemiazygos; superior = accessory hemiazygos) that characteristically drain separately into azygos.
- typically receive 8 lower posterior intercostal veins; 4 each
- hemiazygos formed by left ascending lumbar and subcostal (may communicate w L renal)
- passes through crus of diaphragm, and gets veins from lower oesophagus
- accessory hemiazygos receives bronchial veins from left lung.
Not a content of the posterior mediastinum because it lies behind the costovertebral pleura.
- 12 ganglia, lie just anterior to the rib heads (ie lateral to vertebral bodies)
Begins at T1, fused with inferior cervical ganglion in 80% to form stellate lying in front of & below neck of first rib.
- last 3 lie lateral to corresponding vertebral bodies
Each ganglion receives a preganglionic white ramus from corresponding spinal nerve
- postganglionic grey ramus afferents return medial to white rami
- postganglionic sympathetics pass to thoracic structures.
Splanchnic nerves come from lower 8 ganglia; mainly preganglionic nerve fibres.
-
lowest = least splanchnic: leaves 12th ganglion
--> gows to aorticorenal ganglia / renal plexi
-
middle = lesser splanchnic: leaves 10-11th ganglia
--> same as least
- highest = greater splanchnic: leaves 5th-9th ---> coeliac ganglia and aorticorenal
-
each pierces the crus of its own side. (181)
Half fibres are probably sensory from abdoinal viscera.
The thoracic trunk continues downwards by passing behind the medial arcuate ligament (181)
Upper thoracic ganglionectomy is undertaken in RaynaudÕs and palmar hyperhidrosis
- cervical approach via root of neck, or axillary transthoracic through 3rd intercostal space
- cervical approach requires division of suprapleural membrane, separation of pleura from ribs
- thoracic enters pleural cavity, then divides costovertebral pleura to see chain
¨ cut at 3rd ganglion and rami communicantes of 2nd-3rd ganglia divided; these and intervening chain removed.