esophagus and the esophageal plexus
descending aorta
thoracic duct
tracheobronchial lymph nodes
azygos and hemiazygos veins
thoracic sympathetic trunks
thoracic splanchnic nervesStructures in the Mediastinum
a. Thymus gland
plays a central role in the development of the immune system
lies posterior to the manubrium
receives blood from the internal thoracic and anterior intercostal arteries
is gradually replace by adipose tissue after puberty
b. Heart and pericardial sac (Section 3-5: Thorax-Heart)
c. Superior vena cava
Formed by the union of two brachiocephalic veins
Returns blood to the heart from all structures above the diaphragm except the heart and lungs
Descends vertically and terminates in the right atrium
Lies to the right of the ascending aorta and to the left of the right phrenic nerve
Receives azygous veins before piercing fibrous pericardium
d. Brachiocephalic veins
Are formed in the root of the neck posterior to the sternoclavicular joints by union of the internal jugular and subclavian veins.
Right brachiocephalic vein
receives lymph from the right lymph duct.
is accompanied by right phrenic vein.
Left brachiocephalic vein
is twice as long as the right
runs obliquely down and behind the manubrium
crosses the roots of the three major branches of the aorta
receives lymph from the thoracic duct
e. Aorta
Ascending
begins at the aortic orifice
ascends to the 2nd right sternocostal joint
Arch
Begins at the 2nd right sternocostal joint and arches superiorly and to the left
Anterior to the right pulmonary artery and bifurcation of the trachea
Passes over the root of the right lung
Ends at the body of the T4 vertebra
Descending (thoracic)
begins at the body of T4 vertebra
descends on the left side of the bodies of T5-12 vertebrae, posterior to the root of the left lung and the pericardium
enters the abdomen through the aortic hiatus at the T12 vertebral body
has a number of branches:
bronchial (1-2)
pericardial (twigs)
superior phrenic (1 pair)
esophageal (2)
posterior intercostal (9 pairs)
subcostal (1 pair)
f. Trachea
Continues from the larynx
Contains cartilaginous semicircular rings
Is completed by muscle posteriorly
Descends anterior to the esophagus, slightly to the right of the midsagittal plane
Bifurcates into right and left main bronchi at level of T4/T5 (angle of Louis)
Right bronchi divides into upper and lower lobar bronchi before entering the right lung
g. Esophagus
Is a fibromuscular tube from the pharynx to the stomach
Contains both circular and longitudinal muscles, both skeletal and smooth
upper 1/3-skeletal muscle
lower 2/3-smooth muscle
Passes through right crus of diaphragm at T10
Continues for 1-2 cm below diaphragm
Supplied by esophageal plexus of nerves derived from
right and left vagal nerves
sympathetic nerves
Surrounded by a number of lymph nodes:
inferior deep cervical nodes
posterior mediastinal nodes
intercostal nodes
paratracheal nodes
superior and inferior tracheobronchial nodes.
Vascular supply
arterial: esophageal branches of the thoracic aorta venous: azygos, hemiazygos and accessory azygos veins
h. Thoracic duct
Originates from the cisterna chili in the abdomen
Contains valves