Block 2; Week 1; Sievert; Heart & Mediastinum Flashcards
What is the landmark that separates the superior mediastinum from the inferior mediastinum?
the sternal angle (separates the manubrium from the sternum).
What is the transverse thoracic plane?
It separates the superior & inferior mediastinum. Its anterior portion is the sternal angle. Its posterior portion is at the level of the T4 & T5 vertebrae.
What are all of the subdivisions of the mediastinum & where is the heart/perciardial sac found?
Superior & Inferior (anterior, middle, posterior).
The pericardial sac/heart is found in the inferior middle portion of the mediastinum.
What is the serous pericardium made up of? Where is it found? What are its 2 layers?
Mesothelium (simple squamous).
Found near the heart. Parietal layer on the inside of the fibrous pericardium. Visceral layer found on top of the heart.
What are the functions of the fibrous pericardium?
Anchors the heart to the diaphragm b/c it is continuous w/ the central tendon of the diaphragm.
B/c it is unyielding it prevents overfilling.
What are the great vessels?
Superior & Inferior Vena Cava
Aorta
Pulmonary trunk–>pulmonary arteries
Pulmonary veins
T/F The blood being pumped b/w both the sides of the heart needs to be approximately equal in volume.
True!!
What phase does the cardiac cycle begin with?
Diastole.
It ends in systole.
Which valves close & which valves open during diastole? What contracts?
Aortic & Pulmonic valves close.
Mitral & Tricuspid valves open.
It is a filling phase.
At the end of the phase: atria contraction takes place.
Which valves close & which valves open during systole?
Mitral & tricuspid valves close during systole.
The aortic & pulmonic valves open during systole.
This is a period of ventricular emptying.
What can happen if the blood on both sides of the heart is not balanced/equal?
Buildup of blood somewhere-often edema.
Where is the cardiac notch located?
On the left lung. Exposes the heart to the undersurface of the sternum.
Sometimes you may need to drain fluid from the heart or the pericardial sac–like with cardiac tamponade. Would the cardiac notch be a good place to insert the needle?
No. B/c even tho the left lung isn’t there…the pleural sac is & it could introduce air or fluid into the pleural sac, which could be dangerous.
Where is the mediastinum located?
Between the 2 pulmoanry cavities.
Are the 2 pulmonary cavities attached?
No. They are separate. This is why they can be moved aside to access the pericardial sac.
Which part of the pericardium fuses with the diaphragm?
The fibrous layer of the pericardium (outer layer) fuses with the central tendon of the diaphragm.
What is the vertebral level that corresponds to where the diaphragm meets the pericardium?
T9 vertebral level.
All of our discussion of mediastinum & its borders & its structures is dependent on the patient being in what position?
If the patient were to stand up–>what might happen to the aortic arch?
Supine position important!
Aortic arch might go from being in the superior mediastinum to the inferior mediastinum.
What are some significant things about the level of the T9 vertebrae?
This is the level of the diaphragm.
This is the level where the fibrous pericardium fuses with the central tendon of the diaphragm.
As the middle mediastinum houses the pericardium…this is necessarily the lower border of the inferior mediastinum.
This is also the area of the xiphosternal junction.
What are some things that can be found in the superior mediastinum?
esophagus; trachea
vagus; phrenic; cardiac nerves
aortic arch; parts of the great vessels
What are the 3 things that the inferior mediastinum can be broken down to? What structures are in each?
Anterior: fat, thymus in kids, branches of internal thoracic artery
Middle: pericardium–>heart, SVC, ascending aorta
Posterior: stuff in front of the vertebrae–vessels, nerves, structures.
Which part of the pericardium makes it on to parts of the great vessels? Which vessels? We’re talking w/i the middle mediastinum.
The parietal layer of the serous membrane (inner part of the fibrous pericardium) is also on parts of the SVC base & pulmonary trunk & aorta.
The phrenic nerves & pericardiacophrenic arteries & veins are considered for the purposes of the course a part of which section of the mediastinum?
The middle mediastinum. Disagreement is b/c they are outside of the pericardial sac. But they are in b/w the 2 pulmonary cavities.
What does the phrenic nerves & pericardiacophrenic arteries & veins supply?
The fibrous portion of the pericardium & the parietal layer of the serous pericardium.
How is invagination related to the pericardial sac?
The heart pushes thru this serous pericardium, causing invagination. You get 2 layers of serous pericardium surrounding the heart. Layer closest to the heart: visceral. Other layer: parietal (fused w/ the fibrous layer).
What is the serous pericardium made out of? What tissue is the fibrous pericardium made out of ?
Serous pericardium: mesothelium
Fibrous pericardium: CT
What is another name for the visceral serous pericardium?
Epicardium.
Is the fibrous pericardium distensible?
Is the serous pericardium distensible?
Fibrous-NO
serous-YES
What is the space b/w the visceral & parietal layers of serous pericardium called?
What is it called when fluid builds up there?
Pericardial cavity.
Cardiac Tamponade.
*dangerous b/c w/ each beat of the heart–less & less fluid can be pumped out of the heart. & more & more leaks into cavity.
If you are doing open heart surgery, what do you want to make sure you don’t cut??
The phrenic nerve!! It runs alongside the pericardial sac.
Where does the phrenic nerve originate?
As a part of the ventral rami of a spinal nerve.
What would a right–left side shunt do? What age of person would this be important in?
What is an important R–>L shunt example?
Would bypass pulmonary circulation, bypass the lung.
Important in fetal development.
Ductus Arteriosis. Snags the left recurrent laryngeal nerve.
What does the ductus arteriosis become & when? What does it do?
Ductus arteriosis becomes the ligamentum arteriosum at birth. It is a R–>L shunt from the pulmonary trunk to the arch of the aorta. Snags the left recurrent laryngeal branch.
What is the transverse sinus?
It is the space that you can stick your finger thru that is b/w the outflow vessels & the inflow vessels of the heart.
The outflow vessels are anterior to the sinus & the inflow structures are posterior to the sinus.
Embryologically: Formed b/c of the folding of the tube.