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Cardiology: 2:00 - 3:00
Monday April 6, 2009
Dr. Zehren
Heart
Abbreviations: RV=right ventricle, RA=right atrium, LV=left ventricle, LA=left atrium
Any of Dr. Zehren’s notes copied and pasted directly from his slides are italicized.
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III.
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V.
Scribe: Taylor Nelson
Proof: Teresa Kilborn
Page 1 of 6
Layers of Pericardial Sac [S3]
a. The pericardium is the sac that surrounds the heart
b. Sagittal sections through the pericardium and heart
c. Pericardium consists of two layers
a. Outer thick layer is the fibrous pericardium
1. made up of fibrous connective tissue
2. fused to the diaphragm below
a. this means that when the diaphragm moves during respiration the pericardial sac and
position of the heart moves with the phases of respiration
b. Serous pericardium lies within the fibrous pericardium
1. Secretes a serous fluid
2. Consists of an outer parietal layer and an inner visceral layer
a. Parietal layer adheres to the surface of the fibrous pericardium
a. The parietal layer of serous pericardium is reflected off the fibrous layer and onto the
surfaces of the large vessels entering and leaving the heart
b. The potential space between the parietal and visceral layers of serous pericardium is the
pericardial cavity at this point the serous pericardium continues onto the outer surface of the
heart where it is termed the visceral layer of serous pericardium
c. Normally only a film of fluid is in the cavity to keep the opposed surfaces moist and to allow
the heart to move without much friction
d. Parietal and visceral layers are continuous with each other at the point where the vessels
enter or leave the heart
d. The outer fibrous layer is not expandable, this will become important when we discuss cardiac tamponade
Interior of the pericardial sac [S4]
a. This is what the pericardium looks like if you remove the heart
b. You see the outer fibrous pericardium fused to the diaphragm
c. The shiny layer is the parietal layer of serous pericardium
a. This is where the vessels are piercing the pericardial sac to enter the heart
b. Note the lines of reflection that have been cut, reflecting the parietal layer of serous pericardium
d. There are two parts of the pericardial cavity which have special names
a. Oblique pericardial sinus – inverted “U” shape, located behind the heart, bounded by the pulmonary veins
on either side; essentially a cul de sac behind the heart
b. Transverse pericardial sinus – runs from side to side, passes behind the large arteries leaving the heart
(the pulmonary trunk and ascending aorta) but in front of the superior vena cava
1. [S5] shows a finger being passed though the transverse pericardial sinus
2. Surgeons sometimes use the sinus as a point of ligation – the ligature is passed through the
transverse pericardial sinus and around the vessels
Blood and nerve supply to pericardium [S5]
a. Pericardium has its own nerve and blood supply
b. Blood supply comes via the pericardiacophrenic artery (branch of the internal thoracic artery)
c. Nerve supply via the phrenic nerve
d. These vessels and nerves are sandwiched between the pericardium and the pleura (lining surround in the lung)
Sites of Pericardiocentesis [S6]
a. If excess fluid accumulates in the pericardial cavity that is very serious as it leads to compression of the heart,
known as cardiac tamponade – can be so serious as to stop the heart from functioning resulting in death
b. Excess fluid, whether it be serous fluid due to inflammation or blood due to a traumatic wound, is called
hemopericardium and must be removed
a. The procedure is called pericardiocentesis, and can be done in one of two places
1. Pleura on the left side is deviated to the left resulting in a bare area of pericardium uncovered by
pleura around the fifth or sixth intercostal space directly adjacent to the sternum
2. May also be done on the left part of the infrasternal angle – with needle directed superiorly and
posterior to enter pericardial sac without penetrating the pleura
3 Layers of Heart Wall [S8]
a. Heart has three layers, as it is essentially a modified blood vessel
a. Endocardium – endothelial lining of the heart
b. Myocardium – musculature, specialized cardiac muscle
Cardiology: 2:00 - 3:00
Scribe: Taylor Nelson
Monday April 6, 2009
Proof: Teresa Kilborn
Dr. Zehren
Heart
Page 2 of 6
c. Epicardium – synonymous with the visceral later of serous pericardium
VI. Cardiac “Skeleton” [S10]
a. No bone in the heart, but there is fibrous tissue
b. Atria have been removed in the drawing
c. Appreciate what the functions of the cardiac skeleton are, DO NOT need to know the names of the different
parts, SHOULD understand what purpose the cardiac skeleton serves – This is all Dr. Z said concerning the
cardiac skeleton; however, he did say to study the slide on your own so I have included all of his notes from the
slide below:
a. The CARDIAC SKELETON consists of connective tissue in the heart which provides for the attachment of
cardiac muscle fibers (myocardium) and supports the valves. The cardiac skeleton also serves to partially
insulate the atria from the ventricles during the conduction of an electrical impulse. The right and left
fibrous trigones and the annulus fibrosus of the tricuspid and bicuspid valves are parts of the cardiac
skeleton.
VII. Surfaces, Borders, and other Landmarks of the Heart [S11]
a. [S12] Heart in Anterior View
a. 2/3 of the heat lies to the left of the midline
b. The heart has three surfaces
1. Sternocostal surface (shown on this slide), related to the sternum and the ribs
a. All four chambers of the heart contribute to this surface but it is primarily the right ventricle
c. There are also some grooves that are major landmarks
1. The coronary groove or sulcus completely surrounds the heart like a ring or crown
a. Branches of the coronary arteries and veins run in the coronary groove
b. Also called the atrioventricular groove as it separates the atria and the ventricles
2. Anterior interventricular groove separates the right and left ventricles
3. Posterior interventricular groove on the posterior diaphragmatic surface of the heart
d. The heart has four margins – right, inferior, left, and superior margins
b. [S13] Heart in Posterior View
a. Viewing the pulmonary surface of the heart, formed by the left ventricle which deeply indents the left lung
b. The diaphragmatic surface is formed by both ventricles and rests on the diaphragm
c. Heart also has a base and an apex
1. The base of the heart is the left atrium, faces posterior and receives the four pulmonary veins
2. The apex is the blunt pointed part of the heart formed by the tip of the left ventricle, points to the left
and inferiorly
d. The long axis of the heart runs from the center of the base (which is posterior) downward and forward to
the left to terminate at the apex
VIII. Pattern of Blood Flow Through the Heart [S15]
a. The heart is a four chambered structure consisting of two atria (right and left) and two ventricles (right and left)
b. The RA receives all the unoxygenated blood from tissues of the body, including heart itself (via the coronary
veins)
a. Superior vena cava drains everything from the upper part of the body
b. Everything from below the diaphragm enters the heart though the inferior vena cava
c. The venous blood then passes to the RV passed the right atrioventricular valve (tricuspid valve)
d. Then blood is pumped from RV passed the pulmonary valve out the pulmonary trunk into the right or left
pulmonary artery and finally to the lungs
e. Following oxygenation the four pulmonary veins return oxygenated blood to the LA
f. From the LA the blood is pumped into the LV passed the bicuspid (mitral) valve
g. Then out of the LV into the ascending aorta passed the aortic valve
h. And from there it is distributed to all parts of the body via the branches of the aorta
IX. Internal Anatomy of the Heart [S16]
a. [S17] Right Atrium
a. The interior of the RA shows a smooth-walled part and a rough-walled part separated by a ridge termed the
crista terminalis
b. Ridges of tissue on the rough-walled part are called pectinate muscles or musculi pectinati because they
resemble the teeth of a comb – unique to the atria
c. The smooth-walled part has the opening of the superior and inferior vena cava
1. The inferior vena cava has a non-functional flap-like valve marking its entrance into the atria
d. The coronary sinus is the major vein that drains the heart also opens into the RA
e. The interatrial septum a thumb shaped fossa ovalis is present
Cardiology: 2:00 - 3:00
Scribe: Taylor Nelson
Monday April 6, 2009
Proof: Teresa Kilborn
Dr. Zehren
Heart
Page 3 of 6
1. In fetal life there was an opening called the foramen ovale which allowed oxygenated blood that is
returning to the fetus form the placenta to be pumped out to the body for use – foramen ovale acts
as a shunt for blood to bypass directly from right to left atria, closes off at birth
f. Blood enter RV via the tricuspid orifice which is guarded by the tricuspid valve
b. [S18] Right Ventricle
a. Smooth-walled part (conus arteriosus) which leads to the pulmonary trunk and a rough-walled part
(showing muscular ridges termed trabeculae carneae or fleshy beams)
b. Cone-shaped papillary muscles spring from the walls of the ventricle and attach to the cusps of the
tricuspid valve via slender strands termed chordae tendineae
1. When the papillary muscles contract, they pull on the chordae tendineae and keep the tricuspid valve
closed so that blood is forced to leave through the pulmonary trunk during the contraction of the
ventricles (systole)
c. The interventricular septum seperates the right and left ventricles, the thick muscular part is shown here
d. Also note the septomarginal trabecula, contains part of the conducting system of the heart and passes from
the muscular part of the interventricular septum to the anterior papillary muscles
c. [S19] Shows diagrammatically the papillary muscles, chordae tendineae
a. Notice the chordae tendinedae attach to two adjacent cusps, tension keep the cusps together and prevent
them from being averted into the atria
d. [S20] Blood flow through the RV takes a somewhat U-shaped course, with the inflow tract being posterior and
the outflow tract being superior and directed to the left out the pulmonary trunk past the pulmonary valve
e. [S21] Left Atrium
a. The interior of the LA shows a smooth-walled part (which receives the four pulmonary veins) and a roughwalled part (left auricle with pectinate muscles)
f. [S22] Left Ventricle
a. The LV shows some features similar to those of the RV, note the papillary muscles and chordae tendineae
which attach to the bicuspid (mitral) valve, the trabeculae carneae are also present
b. Smooth walled part of the LV is called the aortic vestibule and leads into the ascending aorta
c. The wall of the LV is 2-3 times thicker than the wall of the RV due to the fact that the LV must work harder
to pump blood to the entire body
g. [S23] Blood Flow through the LV
a. Blood flow through the LV takes a somewhat U-shaped course
b. The inflow tract is posterior and the outflow tract is superior (through the aortic vestibule)
c. Anterior cusp of the mitral valve separates the inflow tract from the outflow tract
X. Valves [S24]
a. [S25] Names and Functions of Heart Valves
a. Posterior view of the valves with the atria removed
b. During diastole (ventricles relaxing, filling with blood from atria) the tricuspid valve on the right and the
bicuspid valve on the left are open, the pulmonary and aortic valves are closed to prevent the reflux of
blood back into the ventricles
c. During systole (ventricles contracting) tricuspid and bicuspid valve close to prevent reflux of blood into the
atria and the pulmonary and aortic valves are forced open so blood flows out of the pulmonary trunk or
aorta
d. The aortic and pulmonary valves each have three cusps
1. In the aortic valve they are called right, left, and posterior (noncoronary)
a. remember because there is a right and left coronary artery, no coronary artery associated
with the posterior cusp
2. In the pulmonary valve they are called right, left, and anterior
e. [S26] slightly dilated walls of the ascending aorta opposite each of these cusps, known as aortic sinuses
1. Note the cusps are forced apart as blood is ejected from the left ventricle during systole, but the
cusps do not stick to the wall of the aorta because of the blood in the sinuses and the dilated walls
2. During diastole as the ventricles relax there is a tendency for the blood to reflux back into the
ventricles, as this happens the blood fills the aortic sinuses forcing the valve closed and sealing the
ventricle from backflow
3. Heart feeds itself through the coronary arteries as they fill with blood when the myocardium is
relaxed during diastole
4. Elastic recoil of the aorta during diastole will pump blood back toward the heart or farther distally, the
valves prevent the blood from going back to the ventricle
XI. Blood Supply to the Heart [S27]
a. [S28] Blood Supply to Heart (Coronary Arteries)
Cardiology: 2:00 - 3:00
Scribe: Taylor Nelson
Monday April 6, 2009
Proof: Teresa Kilborn
Dr. Zehren
Heart
Page 4 of 6
a. Two coronary arteries supply the heart, both arise from the ascending aorta
b. The left coronary artery divides almost immediately into the circumflex and anterior interventricular
branches
1. The circumflex branch runs in the coronary sulcus and supplies the LA and LV
2. The anterior interventricular branch passes in its corresponding sulcus to supply the anterior 2/3 of
the interventricular septum and most of the right and left bundle branches of the conducting system
a. Clinically, the anterior interventricular branch is also known as the “LAD” (Left Anterior
Descending branch)
c. The right coronary artery passes in the coronary sulcus to reach the diaphragmatic surface
1. It gives off the anterior right atrial branch which in turn gives off the sinuatruial nodal artery
2. The posterior interventricular artery supplies the posterior 1/3 of the interventricular septum
3. The atrioventricular nodal artery (not shown) is a small branch that originates opposite the posterior
interventricular artery
a. It supplies the atrioventricular node and bundle of the conducting system
d. The blood supply to the conducting system is important because if it is compromised the person will
experience cardiac arrhythmia
b. [S29] Sites of Anastomoses Between R and L Coronary Arteries
a. One point is where the terminal point of the right coronary anastomoses with the circumflex branch of the
left coronary
b. Another point is where the anterior interventricular form the left coronary and the posterior interventricular
from the right anasomose
c. Lastly, is the point where the septal branch of the posterior and the anterior interventricular arteries
anastomose
d. This is important because these sites can enlarge and provide collateral circulation and an alternate blood
supply if one of the coronary arteries is obstructed
1. Depends on the amount of time available, if the occlusion is slow developing than the potential for
developing collateral circulation is there
c. [S30] Sites of Coronary Artery Occlusion
a. The three most common sites of coronary artery occlusion are:
1. LAD (40-50%)
2. Beginning of the right coronary artery (30-40%)
3. Circumflex branch of the left coronary artery (15-20%)
b. [S32] If occlusion is detected a CABG operation can be performed, segments of a vein or artery are
harvested and used as a bypass of the occluded artery
1. The Great Saphenous Vein is often used for this graft operation because it is a very long, easily
accessible vein of the correct caliber
a. It also bears a high content of elastic tissue
2. [S33] The graft(s) is sutured into the ascending aorta proximally and the coronary artery distal to its
point of occlusion, the valves of the vein must be removed (or the direction of the graft reversed) in
order to prevent them from blocking blood flow
3. The radial artery and internal thoracic artery can also be used for this procedure [S34]
c. [S35] Percutaneus Transluminal Angioplasty
1. Surgeons pass a catheter with a small inflatable balloon attached to its tip into the obstructed
coronary artery, when the catheter reaches the obstruction, the balloon is inflated, flattening the
atherosclerotic plaque against the vessel’s wall, and the vessel is stretched to increase the size of
the lumen, thus improving blood flow
2. After dilation of the vessel, an intravascular stent may be introduced to keep the lumen open
d. [S36] Cardiac Veins (Anterior View)
a. Most of the cardiac veins drain first into the coronary sinus which is a large vein lying in the posterior part of
the coronary sulcus or groove
b. Most of the cardiac veins accompany the branches of the coronary arteries and tend to lie superficial to
them
c. There are some veins in the heart that drain directly into the right atrium
1. These include the anterior cardiac veins
XII. Conducting System and Nerve Supply to Heart [S37]
a. [S38] Conducting system of Heart
a. The conducting system of the heart is composed of specialized cardiac muscle fibers, not neurons
1. Must use special histological techniques to identify the parts of the conducting system, cannot see
grossly
Cardiology: 2:00 - 3:00
Scribe: Taylor Nelson
Monday April 6, 2009
Proof: Teresa Kilborn
Dr. Zehren
Heart
Page 5 of 6
b. Its function is to initiate and propagate an electrical impulse within the heart and cause the heart to
contract in a sequential fashion
c. The sinoatrial node (SA) lies in the superior part of the crista terminalis
1. The pace maker of the heart, initiates impulse
2. The impulse spreads throughout the musculature of the atria and eventually reaches the AV node
d. The atrioventricular node (AV) located in the interatrial septum, near the opening of the coronary sinus
e. From the AV node the impulse spreads via the atrioventricular bundle (bundle of His)
1. The AV bundle runs along the edge of the membranous part of the interventricular septum
2. The most common congenital defect of the heart is a gap of the membranous part of the
interventricular septum – surgeons must take care not to damage this bundle when repairing defects,
as this would lead to cardiac arrhythmia
f. At the muscular part of the septum the AV bundle branches into right and left bundle branches which
descend (one on either side of the muscular part of the interventricular septum) and ramify to become
purkinje fibers which spread out in the myocardium of the ventricles
g. Part of the right bundle branch passes from the muscular part of the interventricular septum to the anterior
papillary muscles via a bridge of tissue termed the moderator band (septomarginal trabecula)
h. Conducting system can initiate and propagate heart beat but it is still under the influence of the autonomic
nervous system (both sympathetic and parasympathetic)
b. [S39] Superficial and Deep Cardiac Plexus
a. The cardiac plexus is a network of nerve fibers located in the concavity of the aortic arch (superficial part of
plexus) and posterior to the aortic arch (deep part of plexus)
b. The two parts of the plexus are continuous and function together
c. Fibers constituting the cardiac plexus are parasympathetic fibers, sympathetic fibers, and general visceral
afferent fibers (carrying visceral information back to the central nervous system)
d. [S40] Innervation of Heart
e. Have 2 sympathetic trunks, 3 ganglia in the neck (superior, middle, and inferior cervical ganglia), the
thoracic ganglia,
f. Two vagus nerves descending from the brain into the thorax form the neck
g. The parasympathetic fibers are shown in blue, the vagus nerve carries the parasympathetics
1. As the vagus is descending in the neck it gives off cervical and cardiac branches that run down to
the cardiac plexus, in the thorax it gives off thoracic cardiac branches
2. These cardiac branches contain presynaptic parasympathetic fibers that synapse in tiny ganglia
located in the cardiac plexus and even on the walls of the heart
3. Three effects parasympathetic stimulation:
a. slowing heart rate
b. decreasing contraction force
c. constrict the coronary arteries
h. Presynaptic sympathetic neurons lie in the lateral horn of spinal cord segments T1-T4
1. Red fibers in the cartoon
2. Axons leave through spinal nerves T1-T4 and enter the sympathetic trunk via white rami
communicantes
3. Some axons synapse in the upper four thoracic paravertebral ganglia while others turn superiorly
and synapse in the superior, middle or inferior cervical ganglia
4. Postsynaptic axons travel to the cardiac plexus via the cervical and thoracic cardiac branches
5. Three effects of sympathetic stimulation:
a. Increase heart rate
b. Increase contraction force
c. Dilate the coronary arteries
[End 48:11]
Dr. Z was cut off at this point so I am including all of his notes from [S40] and [S41] below:
[S40]:
Refer students to plate 227 (Netter, 4th ed.). Excellent diagram showing innervation of the heart.
1. Point out paired sympathetic trunks (with 3 cervical and first 4 thoracic paravertebral ganglia). Usually, as
shown here, inf. cervical and first thoracic paravertebral ganglia are fused (cervicothoracic = stellate ganglion). Cervical
and thoracic cardiac branches arise from the sympathetic trunks.
2. Point out the vagus (X) cranial nerves arising from the medulla of the brainstem. They too have cervical and
thoracic cardiac branches.
3. Discuss parasympathetic innervation of heart and its effects. (blue fibers, pre- & postsynaptic)
Cardiology: 2:00 - 3:00
Scribe: Taylor Nelson
Monday April 6, 2009
Proof: Teresa Kilborn
Dr. Zehren
Heart
Page 6 of 6
The PARASYMPATHETIC INNERVATION of the heart involves X. Presynaptic parasympathetic neurons have their
somata (cell bodies) in the medulla oblongata. Their axons reach the cardiac plexus via the vagal branches noted
above. Synapse occurs in small ganglia on and near the heart. The EFFECTS on the heart include decrease in the
rate and force of contraction and constriction of the coronary aa.
4. Discuss sympathetic innervation and its effects. (red fibers, pre- & postsynaptic)
The SYMPATHETIC INNERVATION of the heart is as follows. Presynaptic sympathetic neurons lie in the lateral horn of
spinal cord segments T1-T4. Their axons leave through spinal nerves T1-T4 and enter the sympathetic trunk via white
rami communicantes. Some axons synapse in the upper four thoracic paravertebral ganglia while others turn
superiorly and synapse in the superior, middle or inferior cervical ganglia. Postsynaptic axons travel to the cardiac
plexus via the cervical and thoracic cardiac branches. The EFFECTS of sympathetic stimulation of the heart are the
opposite of those noted above.
5. Discuss function of vagal afferents (for cardiac reflexes). (black fibers)
AFFERENT FIBERS ARE ALSO PRESENT IN THE CARDIAC PLEXUS. The AFFERENT FIBERS IN X have their
somata in the inferior ganglion of X. These afferents arise from baroreceptors and chemoreceptors near the heart and
are IMPORTANT IN MEDIATING CARDIAC REFLEXES.
6. Discuss function of afferents travelling with sympathetic fibers (for pain). (green)
AFFERENT FIBERS THAT TRAVEL WITH THE SYMPATHETIC NERVES TRANSMIT PAIN IMPULSES. The somata of
these pain neurons are in the dorsal root ganglia of T1-T4 spinal nerves. Their central processes project into the
dorsal horn of spinal cord segments T1-T4.
[S41]:
1. PAIN FROM A HEART ATTACK MAY BE REFERRED TO DERMATOMES T1-T4 (explain concept of dermatome if
necessary). Afferent fibers from these dermatomes project to the same spinal cord segments (T1-T4) as cardiac pain
afferents. Hence the patient feels pain in the skin of the upper chest (T1-T4) and along the medial side of the upper limb
(T1). Usually the pain is felt on the left side.