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[ Home ] [ Up ] [ Anterior Body Wall ] [ Embryonic Body Cavity ] [ Lunglecture ] [ Mediastinum ] [ Heart ] [ Autonomic NS ] [ Rotation of the Gut/Abdomen ] [ Abdominal-Peritoneal Cavities ] [ Glands ,Lymphoid Organs and Blood Supply ] [ Pelvic Cavity ] [ Posterior body wall ] [ Perineum ]
The Mediastinum
"Mediastinum" -
medial septum: median region between the two pleural sacs
Boundaries
Superior - superior aperture
of thorax = thoracic inlet
Inferior – diaphragm
Anterior – sternum, manubrium & costal cartilages
Posterior – Bodies of thoracic vertebrae
Lateral-mediastinal pleura
Subdivisions
are in relation to pericardium:
(Pericardium = closed membranous sac enveloping the heart).
Superior mediastinum - region superior to line connecting
sternal angle and T4-T5 disc
Inferior mediastinum - subdivisions:
Anterior mediastinum -
anterior to pericardium
Middle mediastinum - pericardium and contents
Posterior mediastinum - posterior to pericardium
Contents of mediastinum
heart & great vessels
remnant of thymus (in adults)
distal end of trachea & proximal parts of right and left
bronchi
Esophagus
vagus nerves & phrenic nerves
thoracic duct & lymph nodes
fat
Superior Mediastinum
Brachiocephalic veins
internal jugular and subclavian veins combine to
form brachiocephalics
L & R brachiocephalic vv.
combine to form superior vena cava
R. brachiocephalic receives right lymphatic duct (see
lymphatics)
L. brachiocephalic receives left superior intercostal v.
& thoracic duct (lymphatics)
formed by L & R brachiocephalics and empties into right
atrium
also receives Azygous from posterior mediastinum
returns blood from above
diaphragm, except lungs, which returns into left atrium
terminal half of superior vena cava is in the middle
mediastinum (inside pericardium)
Aortic arch begins
posterior to right half of sternal ang le and passes posterior and to left of trachea and
esophagus pushing trachea to right and constricting esophagus
becomes descending aorta at disc between T4 + T5
arches over left bronchus, left pulmonary artery and bifurcation
of pulmonary trunk
Brachiocephalic trunk
divides into right common
carotid and right subclavian
Left common carotid
Left subclavian artery
Nerves
Right vagus nerve
descends between right common carotid
and right subclavian a.
gives R. recurrent laryngeal n. that hooks under
subclavian a. & ascends to larynx
breaks into right pulmonary, posterior esophageal
& anterior cardiac plexi
Left vagus nerve
descends between left common
carotid and left subclavian a.
gives off L. recurrent laryngeal n. that hooks under the
aorta posterior
to ligamentum arteriosum and ascends between trachea & esophagus to larynx
breaks into left pulmonary, anterior esophageal
& posterior cardiac plexi
Phrenic nerves: traveling
inferiorly to diaphragm, between subclavian vv. and aa.
Lymphatics
Thymus: most
superficial structure in mediastinum prominent in early childhood but reduced to fatty
tissue in adults
R. lymphatic duct empties into R. brachiocephalic v. at
subclavian & jugular vv. Union
collects lymph from upper right quadrant of body (half of
head and thorax + right arm)
Thoracic duct empties into L.
brachiocephalic v. at jugular & subclavian vv. Junction
collects
lymph from the rest of the body including abdomen and lower limbs
Trachea & esophagus
Trachea begins at larynx
and branches at level of sternal angle => not in post. Mediastinum
supported by "C" rings opened
posteriorly where they lie against esophagus
Esophagus begins at pharynx
and runs to stomach, lies between trachea and vertebrae
constricted behind
aortic arch & left bronchus (and also in pharynx & diaphragm)
Anterior Mediastinum
Contains fat, lymph nodes
(sternal) and vessels, sternopericardial ligaments
In infants and children it may
contain part of thymus, in adults only fatty tissue
Middle Mediastinum
We will spend a whole lecture
on this
Posterior Mediastinum
Thoracic aorta
continuation of aortic arch;
enters abdomen via aortic hiatus (in diaphragm)
lies against left pleura where it impresses left lung
gives off paired segmental intercostal aa, and unpaired bronchial (lungs),
esophageal,pericardial & diaphragmatic branches
Left and right pulmonary
arteries
Veins
Pulmonary veins
two on both sides: superior and
inferior
Azygos system
azygous receives right intercostal vv
and empties on superior/inferior vena cavae
hemiazygous and accessory hemiazygous receive left intercostal
vv. and join azygos
azygous
system also receives vertebral venous plexus, mediastinal, esophageal and bronchial vv.
Superior intercostal v. (left) empties
directly in L. brachicephalic v.
Lymphatics
Thoracic duct
carries lymph from all body except
upper left quadrant (right side, diaphragm up)
at level of T5 it deviates left and
empties into union of left jugular & subclavian vv.
Splanchnic nerves
from
sympathetic ganglia (autonomics traveling to abdomen)
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