MEDIASTINUM & THORAX Flashcards
Define the mediastinum and its components.
Defined as the region between the pleural spaces. It is divided into 3 parts: superior, anterior and posterior mediastinum.
List the 5 layers of the mediastinum from anterior to posterior.
- Thymus
- Venous plane - SVC, Right BCV and Left BCV (brachiocephalic)
- Arterial plane - Brachiocephalic trunk, Aortic Arch, Ascending+Descending Aorta, Left Common Carotid, Left subclavian
- Trachea - bifurcates into primary bronchi at T4/5 region
- Esophagus- lies on vertebral colum
Describe the significance of the Aortic Arch Aneurysm.
Can stretch or damage left vagus nerve leading to the sign of a hoarse voice. Especially if the left recurrent laryngeal nerve is compressed
Describe the position of the thoracic aorta in context to surrounding structures.
The thoracic aorta is posterior and left to the esophagus
Describe the location of the Azygos vein and what it does.
The azygos vein is posterior and to the right of the esophagus. It functions to collect venous drainage from muscles in the thoracic wall, such as the intercostal veins.
Describe the significance of Left Atrial Enlargement
Compresses the esophagus leading to dysphagia (difficulty swallowing).
Describe Open “Simple” Pneumothorax. What are some treatment interventions?
This involves a chest wound that opened the thorax but not the lung. During inspiration, the atmospheric pressure shifts the mediastinum TOWARDS unaffected side, so that the intact lung is compressed laterally and the injured lung is displaced medially. Treatments include applying chest strap or gauze to put a closure on the sucking wound.
Describe Tension Pneumothorax. What are measurements can be taken?
A lung wound causes the SAME AFFECTED lung to collapse. During expiration, the affected side collapses BUT the other side is COMPROMISED. Even worse than open pneumothorax since compression occurs at both inspiration and expiration. Treatments include a needle to reduce thorax pressure or an underwater seal suction.
Describe what can cause hemothorax and why it can be lethal.
A punctured blood vessel can cause an internal bleed in the thorax leading to pleural effusion. Bleeding out and compression of the lungs can make this deadly. On a radiograph, this is shown as a fuzzy area at the bottom of the lung.
Describe Paradoxical movement of the diaphragm.
Unilateral loss of phrenic nerve innervation causes the diaphragm to rise on the affected side. This is because contraction on the affected side does not work during attempted inspiration.
Why is tension pneumothorax more dangerous than open pneumothorax?
Tension pneumothorax features cyanosis and causes a problem during inspiration and expiration due to collapse of the damaged lung and a compromised, intact lung
To take out a pleural effusion from the costodiaphragmatic recess, between what ribs would the needle have to be inserted, along the mid-axillary line, without damaging important structures?
Bottom of interspaces between ribs 8-10
A toddler inhales a peanut, without choking, where in the lungs would it get lodged and why?
An inhaled foreign object usually gets lodged in the right main bronchus because it is vertical and narrows significantly as you move to more subsequent structures.
The carotid sheath holds what structures within it?
Common carotid artery (medial), internal jugular vein (lateral) and vagus nerve (posterior)
What pericardial sinus can be exploited by a CT surgeon to get behind the heart from the apex and lift it to see the left atrium?
Oblique pericardial sinus, which is a blind end behind the left atrium where the serous pericardium reflects onto the IVC and pleura.
