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)
what direction does the apex point
what is it composed of
where does it lie (landmark)
a. Directed inferiorly and to the left.
b. Composed entirely of left ventricle.
c. Lies posterior to the left fifth intercostal space (MCL).
where is the base of the heart directed and what forms it
formed by left atrium
points posteriorly
what makes up the anterior surface?
2/3 right ventricle
1/3 left ventricle
what makes up the right surface of the heart
right atrium
what makes up the left surface of the heart as it sits in the cavity
ventricle + auricular appendage
what makes up the diaphragmatic surface of the heart
(in the anatomical position, the heart rests on its diaphragmatic surface)
2/3 left ventricle
1/3 right ventricle.
what is the right border of the heart
right atrium
what is the inferior border of the heart
2/3 right ventricle
1/3 left ventricle
what makes up the left border of the heart
left ventricle + left auricular appendage
what is the function of the fibrous skeleton
a. Provide structural support for heart valves; maintaining patency and preventing distention during heart contraction.
b. Provide attachment sites for the cardiac muscle and for the valve leaflets.
c. Insulates against impulse conduction from atria to ventricles; prevents aberrant spread of impulses.
d. Provides tunnel for passage of the A/V Bundle (of His)
what are the fibrous rings around ?
the orifices of the 4 heart valves
what are the fibrous trigones
connections between the fibrous rings
what does the left fibrous trigone form a link between
aortic and mitral valves
what does the right fibrous trigone form a link between
aortic, mitral and tricuspid valves
what is the flow of blood through the heart
- Deoxygenated blood enters the right atrium through the SVC and IVC.
- Blood passes through the tricuspid valve to enter right ventricle.
- Blood exits right ventricle via pulmonary valve and pulmonary trunk – to lungs.
- Oxygenated blood enters left atrium through pulmonary veins (two left, two right).
- Blood passes through the bicuspid (mitral) valve to enter left ventricle.
- Blood is pumped from the left ventricle to the systemic circulation through the aorta.
what is the sinus venarum and what is it derived from
what does it form the entrance of ?
a. Smooth and thin-walled; derived embrologically from the sinus venosus.
b. Forms the entrances of the IVC, SVC, and coronary veins.
what is the auricle
what is its origin
what is the wall of the auricle lined with
a. Small, ear-like pouch extending anteriorly over the root of the aorta.
b. Represents the embryonic atrium.
c. Wall is lined with pectinate muscles.
what is the ratio of atrial wall: RV wall: LV wall thickness
Ratio 1:3:9
Atrial wall : RV wall : LV wall thickness
what is the crista terminalis?
how is it demarcated externally?
a. Dividing line between sinus venarum and embryonic atrium (auricle).
b. The crista terminalis is demarcated externally by the sulcus terminalis.
what is the fossa ovals and what does it represent?
in the embryo what was its function?
a. Oval depression in interatrial septa representing the embryonic foramen ovale.
b. Embryologically, the foramen ovale allowed deoxygenated blood returning from body to be shunted directly to the left atrium to bypass the fetal lungs.
what is the right atrioventricular orifice?
a. Opening between right atrium and right ventricle with tricuspid valve.
b. Surrounded by a fibrous ring to maintain shape and patency
where is the SA node located
located in the sub-epicardium of the right atrium near the junction of the sulcus (crista) terminalis and the SVC.
where is the AV node located
located in the sub-endocardium of the right atrium, near the opening of coronary sinus.
what is trabeculae carnae
muscular ridges of the ventricular wall
what is the moderator band (septomarginal)
a specialized trabecular muscle passing from the interventricular septum to the anterior papillary muscle.
what is the conus arteriosus
smooth-walled portion of chamber (right ventricle) leading to pulmonary artery.
where is the right atrioventricular valve located (landmark)
how many cusps
what attaches the valve cusps to the papillary muscles
a. Located posterior to the sternum at the 4th or 5th intercostal space.
b. 3 cusps (anterior; posterior; and septal) attach to fibrous ring.
c. Chordae tendineae connect the valve cusps to the papillary muscles.
what do the papillary muscles attach valve cups to?
what happens when papillary muscles contract?
d. Papillary muscles attach valve cusps to ventricle wall.
When papillary muscle contract they pull the valve leaflets centrally and close the AV orifice. This also prevents the valves from everting into right atrium during ventricular contraction.
what are the membranous and muscular interventricular septum?
which one is thicker
- Membranous interventricular septum – very short, thin walled portion of the IV septum
- Muscular interventricular septum – much larger thick, muscular portion of the IV septum
where is the pulmonary valve located
how many cusps
what is the thickened free edge of the cusp form
a. Located posterior to the sternum at the level of the 3rd costal cartilage.
b. 3 cusps (anterior, left, right) attach to fibrous ring.
c. Free edge of the cusp is thickened to form the nodule and lunule.
what are the pulmonary sinuses
what happens when the left ventricles contract (in terms of the pulmonary valve)
dilated portion of the pulmonary trunk that surrounds each cusp
e. When ventricle relaxes, blood in pulmonary trunk reverses its flow. The sinuses fill with blood and the cusps close.
what forms the larger, smooth-walled posterior portion of the left atrium
the proximal portion of the pulmonary vein
what does the left atrium receive
- Receives the 2 superior and 2 inferior pulmonary veins.
what does the left auricle represent and what is it lined with
- The auricle represents the embryonic atrium and is lined with pectinate muscles.
where is the valve of the foramen ovale
in the interatrial septa of the left atrium
what is the left AV orifice
a. Opening between left atrium and left ventricle with bicuspid (mitral) valve.
b. Surrounded by a fibrous ring.
how are the trabeculae carnae muscles in the left ventricle compared with the right?
finer, but more abundant than in the right ventricle.
what is the aortic vestibule
smooth walled portion of the left ventricle leading to the aorta
where is the bicuspid valve located
how many cusps
a. Located posterior to the sternum at the 4th costal cartilage.
b. 2 cusps (anterior; posterior) attach to fibrous ring.
where is the aortic (semilunar) valve located
how many cusps
a. Located posterior to the sternum at the level of the 3rd intercostal space.
b. 3 cusps (posterior, left, right) attach to fibrous ring.
where are the openings for the right and left coronary arteries
in the left and right cusps of the aortic valve
what is valve insufficiency
(regurgitation) is the failure of any of the heart valves to close completely.
what is valve stenosis
narrowing of the valvular orifice
where is the auscultory site for the Pulmonary valve
2nd ICS LEFT of sternum
where is the auscultory site for the aortic valve
2nd ICS RIGHT of sternum
where is the auscultory site for the tricuspid valve
4th ICS LEFT of sternum
where is the auscultory site for the bicuspid valve
5th ICS LEFT MCL (mid clavicular line)
