L1 Mediastinum and heart coverings Flashcards
what is the mediastinum?
Median septum between the right and left pleural sacs.
Boundaries of mediastinum?
A=sternum. P=vertebral column. S=thoracic inlet. I=diaphragm. L=pleura.
What is the line that divides superior and inferior mediastinum?
Imaginary plane from sternal angle to the 4th thoracic vertebra.
Subdivisions of superior and inferior mediastinum?
A= front of pericardium. P= behind pericardium. Middle= Heart in pericardium.
Contents of superior mediastinum.
Tubes= oesophagus, trachea. Arteries= Arch of aorta, brachiocephalic, left common carotid, left subclavian. Veins= superior vena cava, left and right brachiocephalic. Nerves= Vagus, phrenic, left recurrent laryngeal nerve. Miscellaneous= thymus, thoracic duct, lymph nodes(para-tracheal and tracheo-bronchal).
Contents of anterior mediastinum.
Superior and inferior pericardial ligaments, remains of thymus, internal thoracic vessels.
Contents of posterior mediastinum.
Descending aorta, oesophagus, thoracic duct, azygos,
superior hemiazygos, inferior hemiazygos veins.
Posterior lymph nodes, splanchnic nerves, vagi.
Contents of middle mediastinum.
The heart within its pericardium.
Arteries: ascending aorta and pulmonary trunk.
Veins: Termination of superior vena cava, Termination of azygos vein, Termination of inferior vena cava, Termination of the 4 pulmonary veins.
Nerves: Rt. and left phrenic nerves, The deep cardiac plexus: anterior to the tracheal bifurcation.
Tubes: The right and left main bronchi.
Lymph nodes: tracheo - bronchial lymph nodes.
Mediastinal syndrome.
Compression of mediastinal structures by a tumor.
mediastinal shift.
pleural effusion or pneumothorax- shift to opposite side.
lung collapse or fibrosis- shift to same side.
What is pericardium and where?
it is a fibro-serous sac which encloses heart and roots of major vessels, made up of 2 sacs.
Fibrous pericardium.
its a tough conical single layered outer sac of pericardium.
Bare area of pericardium.
fibrous pericardium is in direct contact with 3rd and 4th intercostal space.
Serous pericardium.
It is the thin transparent double-layered serous sac (parietal and visceral) which lies within the fibrous pericardium.
Contents of pericardium.
Tubular sheath around aorta and pulmonary trunk.
j- shaped tubular sheath around 4 pulmonary veins and vena cava.
space between parietal and visceral sacs filled with fluid to prevent friction.
pericardial cavity.
Transverse sinus.
horizontal gap between aorta, pulmonary trunk (anterior) with superior vena cava ( posterior).
How is the sinus formed?
From absorbed dorsal mesocardium.
Oblique sinus.
inverted U-shaped blind gap behind left atrium, pulmonary veins on each side, below reflection of visceral, and continuous below with pericardial cavity.
Blood supply of pericardium.
fibrous and parietal: pericardio – phrenic, musclo -phrenic arteries, and descending thoracic aorta.
visceral: coronary arteries.
veins: internal thoracic and azygos veins.
Nerve supply of pericardium.
fibrous and parietal: somatic fibers from phrenic nerves (sensitive to pain).
visceral: autonomic nerves from cardiac plexus (insensitive to pain).
Pericarditis.
inflammation > rough serous sac > frictional rub.
Pericardial effusion.
fluid fills pericardial cavity > heart unable to fully expand > fails to pump out blood same rate it receives.
Cardiac tamponade.
persistent pericardial effusion > heart compression > limits blood volume. (heamo:blood/ pneumo:air)
Pericardiocentesis.
Relieves tamponade, wide bore needle in 5th or 6th intercostal space near sternum.
