Lea Lecture Heart/Middle Mediastinum Flashcards
what are the borders of the middle mediastinum?
5
- Superior: transverse thoracic plane – disc between TV4 and TV5
- Inferior: diaphragm
- Lateral: mediastinal pleura
- Anterior: anterior border of pericardium
- Posterior: posterior border of pericardium
What are the contents of the middle mediastinum
5
- Pericardium
- Heart
- Origin of great vessels: pulmonary trunk, ascending aorta, pulmonary veins.
- Phrenic nerve and pericardiophrenic vessels
what are the landmarks of the superior border of the heart
2nd left costal cartilage to 3rd right costal cartilage.
what are the landmarks of the right border of the heart? left?
right–> 3rd right costal cartilage to 6th right costal costal cartilage
left–> left 5th intercostal space MCL to 2nd left costal cartilage
what are the landmarks for the inferior border of the heart?
6th right costal cartilage to tleft 5th intercostal space at MCL apex
what is the pericardium
A. A closed, fibroserous sac surrounding the heart and origins of great vessels.
what is the fibrous pericardium?
what is its function
- Tough external layer composed of dense connective.
2. Anchors heart and prevents overfilling.
what are the anterior, posterior, inferior and superior attachments of the fibrous pericardium
a. anteriorly to the sternum via sternopericardial ligaments.
b. posteriorly to the fascia of the esophagus.
c. Inferiorly to the central tendon of diaphragm via pericardiacophrenic ligaments.
d. Superiorly with the adventitia (outer connective tissue layer) of the great vessels.
what is the function of the serosal pericardium (visceral and parietal)
- A closed sac that provides smooth, frictionless surfaces for the heart to move in during contraction.
what is the parietal pericardium
a. Composed of simple squamous epithelial cells + thin layer of loose connective tissue
b. Adherant to inner surface of fibrous pericardium
what is the visceral pericardium? what is it also called
a. Composed of simple squamous epithelial cells + thin layer of loose connective tissue
b. Lines heart surfaces; continuous with parietal pericardium at great vessels.
c. Forms outer layer of the heart and is called the epicardium.
what is the potential space
between parietal and visceral pericardium; contains only a minimal amount of lubricating serous fluid.
what is cardiac tamponade
what are the symptoms?
If the pericardial space is FILLED with FLUID (due to trauma, inflammation) the heart cannot fill to capacity due to the surrounding fluid and the inflexibility of the fibrous pericardium. This condition can be lethal as filling of the heart is reduced. The maximum capacity of pericardial sac is approximately 300 cc.
Beck’s Triad
Distended neck veins
Hypotension
Muffled heart sounds
what is pericardiocentesis
where is the needle inserted
Pericardiocentesis is a procedure which removes excess pericardial fluid. Typically, a needle is inserted through the bare area of the heart (left of sternum; 5th or 6th intercostal space) to avoid pleural cavity.
what is the function of the pericardial sinuses in the embryo
separate the arterial and venous ends of the embryonic tubular heart
what is the anterior border of the transverse pericardial sinus?
aorta and pulmonary trunk (arteries)
what is the posterior border of the transverse pericardial sinus
SVC and pulmonary veins
why is the transverse pericardial sinus clinically relevant
Clinically important sinus because it allows surgeons to pass a surgical clamp around the major arteries and veins and insert tubes allowing blood to be diverted to a cardiac bypass pump during coronary artery surgery.
what is the oblique pericardial sinus?
what are its borders?
- Pocket-like, cul-de-sac posterior to the heart.
2. Bounded by the pulmonary veins and IVC.
what is the vascular supply to the pericardium?
- Pericardiacophrenic arteries (from internal thoracic artery)
- Pericardiacophrenic veins → internal thoracic veins.
what nerve provides sensory innervation to the fibrous and parietal pericardium
phrenic nerve
what nerve supplies the visceral pericardium?
cardiac plexus
where is pain from the pericardium referred to?
referred to the shoulder/neck region
b/c of dermatomes C3, C4, C5 (phrenic)
what is it called when the pericardial membrane becomes inflamed?
what happens with this?
pericarditis), they become rough and no longer slide easily over one another. Pericarditis can be very painful due to the presence of pain fibers in the fibrous and parietal pericardium
does the visceral pericardium have pain fibers?
no
what is Dressler’s syndrome?
post MI pericarditits
dead muscle leaks fluid into the pericardium
what is the orientation of the heart?
where is the apex and where is the base?
the left portion of the heart lies posteriorly and the right anterior
apex –> directed inferiorly and to the left
base–> directed posteriorly
where does the pulmonary trunk exit?
what does it carry (from where to where)
this artery (exits right ventricle);
carries de-oxygenated blood from heart to lungs;
divides into right and left pulmonary arteries. (i.e. pulmonary circulation)
where do the pulmonary veins enter?
what do they carry
(enter left atrium);
superior and inferior veins from left and right lungs carry oxygenated blood from the lungs to the heart.
where does the ascending aorta exit?
what does it carry?
(exits left ventricle);
transports oxygenated blood to the body (i.e. systemic circulation)
what are the external sulci of the heart?
atrioventricular (coronary sulcus) interventricular (anterior and posterior) sulcus terminalis (on the outside of the right atrium)