Where is the location of the imaginary line that divides the superior and inferior mediastinum by an imaginary transverse plane?
The imaginary line dividing the superior and inferior mediastinum is located from the sternal angle to the disc at T4/T5.
Describe the three compartments of the inferior mediastinum.
Three compartments of the inferior mediastinum:
1) anterior mediastinum - heart to sternum
2) middle mediastinum - contains heart & roots of the great vessels
3) posterior mediastinum - heart to bodies of T5/T6
What are common causes of mediastinal widening typically discovered in chest radiographs?
Common causes of mediastinal widening:
- hemorrhage into the mediastinum from lacerated great vessels (trauma)
- malignant lymphoma (cancer of lymphatic tissues)
- hypertophy of the heart (venous blood retuns to the heart faster rate than cardiac output)
What does the fusion of the pleuropericardial membranes create?
The fusion of the pleuropericardial membranes vertically divides the thoracic cavity into the pericardial cavity and bilateral pleural cavities.
The pleuropericardial membranes then form the fibrous pericardium.
What can be found within the tough fibrous pericardium?
Within the tough fibrous pericardium is the serous pericaridum layer, made up of continuous pluera from visceral and parietal layers (like the lungs) and between these two layers is the pericardial cavity.
Where do the parietal and visceral layers of serous pericardium become continuous?
What does the pericardial sac fuse with?
The parietal and visceral layers of the serous pericardium become continuous at the roots of the great vessels.
The pericardial sac fuses with the central tendon of the diaphragm.
Describe the location and function of the transverse pericardial sinus.
The transverse pericardial sinus is posterior to the intrapericardial parts of the aorta/pulmonary trunks and anterior to the intrapericardial parts of the superior vena cava/pulmonary veins.
It's function is to act as a pathway.
Why can cardiac tamponade be fatal and how is pericardiocentesis normally performed?
A cardiac tamponade is any presence of pressure within the pericardial cavity but outside of the heart itself. It can result from hemorrage of a myocardial muscle following an MI, bleeding from the periardial cavity after cardiac operation or stab wound, or air infiltration due to pneumothorax.
This condition can be fatal because it makes it more difficult for the heart to increase its volume and pump out blood, reducing cardiac output.
The treatment is pericardiocentesis (draining fluid from pericardial cavity) which is perfomed by inserting a wide-bore needle through the left 5th or 6th intercostal space near the sternum. It may also be reached via the infrasternal angle by passing the needle superoposteriorly. This second method steers clear of the lung and pleurae, however you must be careful to not puncture the internal thoracic artery.
How do cardiac surgeons use the transverse pericardial sinus?
Cardiac surgeons can pass a surgical clamp or ligature through this sinus around the ascending aorta and pulmonary trunk to stop or diverty the circulation of blood in these arteries while perfoming cardiac surgery such as coronary artery bypass grafting.