Chapter 19 - Heart Flashcards
The cardiovascular system is made of…
1.) The Heart
2.) Blood vessels
Perfusion
Delivery of blood per unit time per gram of tissue (mL/min/g)
Blood vessels
Conduits of the cardiovascular system that transport blood throughout the body
Arteries
Transport blood AWAY from the heart
Veins
Transport blood toward the heart
Capillaries
Serve as exchange sites, either between the blood and alveoli (air sacs) of the lungs or between blood and systematic cells
Atrium
- A small chamber that receives blood from veins
- Auricle –> a wrinkled, flaplike extension/appendage that increases atrial volume
Ventricle
- A larger chamber that pumps blood into arteries
- Makes up most of the volume of the heart
- The area of the pump itself
- Pump the same amount of blood on each side, just at different pressures
Both atria release…
- Atrial Natriuretic Peptide (ANP)
- Helps to lower blood pressure
Right atrium
- Receives deoxygenated blood from the body
- Thin-walled and small
-3 veins empty into here –> SVC, IVC, coronary sinus - Posterior wall is smooth-walled
- Anterior wall has ridges (pectinate muscles only in right atrium)
- Posterior and anterior regions are separated by crista terminalis (only in right atrium because they’re attachment points for pectinate muscles- like a comb where crista terminalis is comb head)
Right ventricle
- Pumps deoxygenated blood through pulmonary semilunar valves –> pulmonary trunk –> lungs
- On most of anterior surface
- Has trabeculae carneae, papillary muscles, and tendinous cords
- Has moderator band (has to do with electrical conductivity)
- Connects the interventricular septum to the anterior papillary muscle
Left atrium
- Receives oxygenated blood from the lungs
- 4 pulmonary veins empty into left atrium
Left ventricle
- Pumps oxygenated blood to the aortic semilunar valve –> aorta —> body
- The myocardium is 3x thicker than in right because the ventricle works more to pump blood to body
- On posteroinferior surface of the heart
- Has papillary muscles, and tendinous cords
Superior vena cava (SVC)
- Drains deoxygenated blood into the right atrium
- Drains blood from the superior regions of the trunk and superior to the heart (head, neck, upper limbs, superior region of the trunk)
Inferior vena cava (IVC)
- Drains deoxygenated blood into the right atrium
- Drains blood from the inferior regions of the trunk, inferior to the heart, and lower limbs
Pulmonary trunk
- Receives deoxygenated blood pumped from the right ventricle
- Blood is to be transported to the lungs
- Splits into the right and left pulmonary arteries
Pulmonary veins
- Drains oxygenated blood into left atrium
Aorta
- Recieves oxygenated blood pumped from left ventricle
Great vessels
- Large arteries and veins connected directly with specific chambers of the heart
- Helps blood be transported to and from chambers
- Right side –> SVC/IVC, pulmonary trunk
- Left side –> pulmonary veins, aorta
The right side valves are…
- Right atrioventricular valve
- Pulmonary semilunar valve
The left side valves are…
- Left atrioventricular valve
- Aortic semilunar valve
Right atrioventricular (AV) valve
- Between right atrium and right ventricle
- The tricuspid valve (has 3 flaps)
- tRIcuspid, RIght
Pulmonary semilunar valve
- Between the right ventricle and pulmonary trunk
Left atrioventricular (AV) valve
- Between the left atrium and left ventricle
- The bicuspid/ mitral valve (has 2 flaps)
Aortic semilunar valve
- Between left ventricle and aorta
Edema
Accumulation of fluid in the intestinal space surrounding the cells
Describe the location of the heart in general
- In mediastinum between 2nd rib and 5th intercostal space
- On superior surface of diaphragm
- 2/3 of the heart is left to the midsternal line
- Anterior to vertebral column
- Posterior to the sternum
- Close to the stomach –> stomach pain/issues may be mistaken with heart
What is the base and where is it in the body?
- Base is the posterior surface of the heart
- Leans toward right shoulder
What is the apex and where is it in the body?
- The pointed, lower tip of the heart
- Points toward left hip
- Where stimulation of the ventricles begin
Apical impulse
- Palpated between 5th and 6th ribs, just below left nipple
- Closest point where the heart is coming towards thoracic cage –> apex
Where are the boarders of the heart, where are they pointing?
- The right side/boarder is located more anteriorly
- The left side/ boarder is located more posteriorly
What are the boarders of the superior mediastinum?
Superior –> Thoracic inlet
Anterior –> manubrium of the sternum
Inferior –> sternal angle
Posterior –> Bodies of T4-T5 vertebrae
What are the different parts of the inferior mediastinum and what do they contain?
Anterior mediastinum –> has lymph nodes, fat, and connective tissue
Medial mediastinum –> Mainly has the heart and pericardium
Posterior mediastinum –> Has esophagus, blood vessels, and trachea
What makes up the pericardium (the covering of the heart, a double-walled sac)
1.) Superficial fibrous pericardium
2.) Serous pericardium (parietal layer and visceral layer (epicardium)) –> Each layer is separated by a pericardial cavity filled with fluid –> serous fluid is produced by these layers and it’s an oily mixture
Superficial fibrous pericardium
- The outermost covering
- Doesn’t attach to the heart, but is attached superiorly to the bone of the atrial trunks (pulmonary + aorta) and inferiorly to the diaphragm
- Dense irregular connective tissue
- Protects, anchors to surrounding structures, and prevents overfilling
Parietal layer of serous pericardium
- Lines internal surface of fibrous pericardium
- Simple squamous epithelium and delicate areolar connective tissue
- Attaches to inner surface of fibrous pericardium
Visceral layer (epicardium) of serous pericardium
- Lines external surface of the heart
- Simple squamous epithelium and areolar connective tissue
- Most attaches directly to the heart
- THickens as we age as it gets more adipose connective tissue
The pericardial sac is made of…
- Fibrous pericardium
- Parietal layer of serous pericardium
What are the 3 layers of the heart wall
1.) Epicardium (visceral pericardium)
2.) Myocardium
3.) Endocardium
Myocardium
- The middle layer and the thickest one
- Spiral bundles of contractile cardiac muscle cells
Cardiac skeleton: crisscrossing, interlacing layer of connective tissue
–> Anchors cardiac muscle fibers
–> supports great vessels and valves
–> Limits spread of action potentials to specific path
Endocardium
- Epithelial layer is continuous with endolining of blood vessels –> endothelium: Epithelial layers that line both the heart and blood vessels at the inner surface
- Lines heart chambers and covers cardiac skeleton of valves
- Simple squamous epithelium and areolar connective tissue
Fibrous skeleton
A structure composed of dense irregular connective tissue that internally supports the heart
Cardiac muscle cells at rest
- Sarcolemma has K+ leak channels (helps with repolarization, Na+ leak channels (helps with repolarization), Na+/K+ pumps to maintain RMP
- RMP = -90 mV
- Contractile cells
- Slow voltage-gated Ca2+ channels in sarcolemma help with function of cardiac muscle cells
- Outside = >Na+, Ca2+
- Inside = > K+
Interatrial septum
- Separates atria
- Has the fossa ovalis (only visible in right atrium)
- A hole in interatrial septum –> ASD –> atrial septum defect
Fossa ovalis
Remnant of foramen ovale of fetal heart
Interventricular septum
- Separates the ventricles
- Hole in interventricular spetum –> VSD –> ventricular septum defect
Coronary sulcus (atrioventricular groove)
- Separates atria from ventricles
- Anterior interventricular sulcus –> anterior side
- Posterior interventricular sulcus –> posterior side
- Has coronary vessels that supply blood to heart wall
Where are pectinate muscles only found?
Only in auricles
Trabeculae carneae
- Large, smooth, irregular ridges of muscle on walls
- In R/L ventricles
- Join to form papillary muscles
Papillary muscles
- Cone shaped projections extending from internal ventricle wall
- Helps anchor chrodae tendineae
- # can range from 2 to 9
- Works with chordae tendineae to prevent inverting flap into atria
Tendinous cords (chordae tendineae)
- Thin strands of collagen fibers attaching to AV valve
- Holds valve flap in closed position
- Works with papillary muscle to prevent inverting flap into atria
Interventricular sulci
- Separates the ventricles from the outside
- Is over the interventricular septum
Heart valves
- Ensure unidirectional flow of the blood
- Open and close in response to pressure change
- 2 atrioventricular (AV) valves –> close when ventricles contract and force blood superiorly
Semilunar (SL) valves
- No papillary muscles or tendinous cords
- Prevent backflow into the ventricles when the ventricles relax
- Open and close in response to pressure change
- Each of the SL valves has 3 cusps in the shape of a half moon
What 2 conditions could weaken the heart in terms of the valves?
1.) Incompetent valve –> Blood backflows so heart repumps the same blood over and over –> can accumulate CO2 in the body
2.) Valvular stenosis –> stiff flaps constrict opening –> heart must exert more force to pump blood –> muscle will grow because of increased work and will need more blood supply –> not enough blood can lead to cells dying –> heart attack
Pulmonary circulation
- Transports blood from the right side of the heart to the alveoli of the lungs for gas exchange, and back to the left side of the heart
- Short, low-pressure circulation
Systemic circulation/ systemic circuit
- Transports blood from the left side of the heart to the systemic cells of the body for nutrient and gas exchange, and back to the right side of the heart
- Long, high-friction circulation
Coronary circulation
- Because necessities can’t defuse through thick heart wall fast enough
- Main way of how the heart muscle gets its blood supply –> delivered when the heart is relaxed and the left ventricle receives the most blood supply
- Contains anastomoses (junctions between arteries or veins)
- Cannot compensate for coronary artery occlusion
Coronary arteries
- Positioned within coronary sulcus
- Arise from the base of aorta and supply blood to myocardium and open and close (flow is intermittent, not a steady flow)
- Right and left coronary artery plus their branches
Right coronary artery
- Starts at the aorta
- Branches include…
1.) Posterior interventricular artery (posterior descending artery) - Supply posterior interventricular sulcus/ posterior aspect of the heart
2.) Right marginal artery - Supply the lateral wall of the right ventricle/ lateral right side of the heart
Left coronary artery
- Starts at the aorta
- Supplies interventricular septum, anterior ventricular walls, left atrium, and posterior wall of left ventricle
Branches include …
1.) Circumflex artery - Supply left atrium and posterior walls of left ventricle
2.) Anterior interventricular artery (widowmaker) - Supply interventricular septum and anterior walls of both ventricles
- If artery becomes occluded –> risk of heart attack
Body tissues are generally served by _________
- One artery (end artery)
- Some may be served by two or more arteries (arterial anastomoses)
Coronary veins
- Collect blood from capillary beds
- Several anterior cardiac veins empty directly into right atrium anteriorly
- Coronary sinus
–> Formed by merging cardiac veins
–> On posterior aspect - Made of 3 merging veins
1.) Great cardiac vein - Within anterior interventricular sulcus
- Alongside anterior interventricular artery
2.) Middle cardiac vein - Within posterior interventricular sulcus
- Alongside posterior interventricular artery
3.) Small cardiac vein - In right inferior margin
- Alongside right marginal artery
What are some aspects of cardiac muscle cells that are different than skeletal muscle cells?
- Less numerous T tubles (thus, most Ca2+ comes from blood in ECF)
- SR simpler than in skeletal muscle
What are intercalated discs and what are the components?
Intercalated discs: Junctions between cells to anchor cardiac cells, link cells mechanically and electrically
- Components
–> Desmosomes
–> Gap junctions
Desmosomes
- Prevent cells from separating during contraction
- Protein filaments that anchor into a protein plaque located in internal surface of sarcolemma
- Mechanical junctions
Gap junctions
- Allow ions to pass from cell to cell (low resistant pathway)
- Electrically couple adjacent cells (allow heart to be functional syncytium)
Functional syncytium
- A chamber that functions as a single unit
- Synctium: A multinucleated mass that’s transformed by the main unit of originally separate cells
- Ex: heart chamber –> the chamber functions as if it were one cell
Cardiac muscle cells rely on what type of energy method?
- Aerobic cellular respiration
- WIthout it, it may rely on lactic acid (from skeletal muscles) and it may have to rely and that or ketone bodies
Sinoatrial (SA) node
- Posterior wall of right atrium
- Cells initiate the heartbeat
- The pacemaker of the heart
- Noncontractile (autorhythmic) cells
Atrioventricular (AV) node
- On the floor of the right atrium between right AV valve and opening for coronary sinus
Atrioventricular (AV) bundle/ “Bundle of His”
- Extends from AV node into and through interventricular septum
- Divides into left and right bundle branches
Purkinje fibers
- Extend from bundle branges beginning at apex and continue through walls of ventricles
- Large in diameter –> fast action potential to ventricular myocardium –> cardiac muscle cells in both ventricles contract at the same time
Conduction system of parasympathetic innervation
- Cardioinhibitory center sends nerve signals along vagus nerve (CN X - 10) –> results in a decrease in heart rate
- CN X gives off branches that supply the heart, but doesn’t have a direct effect on force of contraction since it doesn’t innervate myocardium
–> Right vagus nerve –> innvervates SA node
–> Left vagus nerve –> innervates AV node
Conduction system of sympathetic innervation
- Cardioacceleratory center sends merve signals along cardiac nerves –> which results in an increase in both heart rate and force of contraction
- Neurons within T1-T5 of spinal cord extend to SA node, AV node, and myocardium
Receptors in the conduction system include…
1.) Baroreceptor
- Some in right atrium
2.) Chemoreceptor
What is the cardiac center and what parts make it up?
Cardiac center
- In the cardiovascular center of medulla oblongata
- Regulated by autonomic system –> Heart rate and strength of contraction and modifies cardiac activity
Made of…
1.) Cardioacceletory center
2.) Cardioinhibitory center
Stimulating heart contraction is organized in two events…
1.) Stimulation of the heart by conduction system
2.) Cardiac muscle cells (contraction)
Events occur TWICE in a heartbeat, first in cardiac muscle cells of the atria and then the cardiac muscle cells of the ventricles
SA Nodal cells at rest…
RMP= -60mV –> maintained by K+ leak channels, Na+ leak channels, and Na+/K+ pumps, but doesn’t have a stable RMP
- Have specific voltage-gated channels
1.) Voltage-gated cation channels (open)
2.) Voltage-gated Ca2+ channels - T-Type and L-Type (closed)
3.) Voltage-gated K+ channels
- Outside > Na+ and Ca2+
- Inside > K+
SA nodal cell stimulation steps
1.) Reaching threshold
- Cation channels open
- Na+ enters nodal cell, T-type Ca2+ channels open and influx of Ca2+
- Threshold reached (-60mV –> -40mV)
- Cation channels close
2.) Depolarization
- Bc of threshold, voltage-gated Ca2+ channels open
- Ca2+ enters nodal cell
- Depolarization (-40mV –> just above 0 mV)
- Voltage-gated Ca2+ channels close
3.) Repolarization
- Voltage gated K+ channels open
- K+ exits nodal cell
- Repolarization (+ mV –> -60 mV) –> triggers reopening of voltage-gated cation channels, which restarts the process
- Voltage-gated K+ channels close
Spread of action potential in the heart (atria and ventricles)
1.) Sinoatrial (SA) node and atrial myocardium
- Action potential is generated at SA node
- Action potential spreads along sarcolemma within atria through gap junctions toward AV node
- Allows for both atria to contract at the same time
2.) Atrioventricular (AV) node
- Action potential is delayed at AV node –> allows atria to finish contracting and force blood into ventricles to complete filling
- Action potential is passed to AV bundle within interventricular septum
3.) AV bundle, bundle branches, and purkinje fibers
- AV bundle conducts the action potential to the left and right bundle branches
- Action potential reaches purkinje fibers
4.) Ventricular myocardium
- Action potential spreads from the purkinje fibers to the ventricles by gap junctions
- Simultaneous contraction of both ventricles
Cardiac muscle cell stimulation steps
1.) Depolarization
- Fast voltage-gated Na+ channels open (by action potential from SA cells)
- Na+ enters cardiac muscle cell
- Depolarization (-90 mV –> +30 mV)
- Fast voltage-gated Na+ channels close to inactivated state
2.) Plateau
- Voltage-gated K+ channels open
- K+ flows out and because this causes a slight membrane potential change –> slow voltage-gated Ca2+ channels open
- Ca2+ enters cell
- B/c of K+ exiting and Ca2+ entering –> no electrical change and depolarization state is maintained
3.) Repolarization
- Voltage-gated K+ channels remain open but voltage-gated Ca2+ are closed to complete repolarization
- K+ moves out of cell
- Voltage-gated Ca2+ channels close
- Repolarization (+30 mV –> -90 mV)
What can cardiac muscles not exhibit?
Tetany (sustained muscle contraction without relaxation)
Autorhythmic (non-contractile) cells
- Have unstable RMP (~ -50-55 mV) due to opening of slow Na+ channels and continuously depolarize
- Threshold ~ -40 mV
- Don’t contract
What do each of the parts of the cardiac center do?
1.) Cardioacceleratory center (sympathetic) –> Affects SA and AV nodes, heart muscle, and coronary arteries
2.) Cardioinhibitory center (parasympathetic) –> Inhibits SA and AV nodes via vagus nerves
Electrocardiogram (ECG/EKG)
- Composite of all action potentials generated by nodal and contractile cells at given time
- 3 waves (indicates electrical changes with depolarization and repolarization within heart regions)
1.) P Wave
2.) QRS complex
3.) T wave
Describe the different electrical events of the heart in an ECG
1.) P wave
- Atrial depolarization that originate at SA node
- Stimulates the sarcomeres within cardiac muscles
2.) P-Q segment
- Atrial plateau
- Prevents the sarcolemma of the atria from repolarizing –> allowing time for sarcomeres within cardiac muscle cells of the atria to contract and relax
3.) QRS complex
- Stimulates the sarcomeres within cardiac muscle cells of the ventricles to contract
- Q = Down AV bundle/septum
- R = Going down right/left bundle branches
- S = Moving up the purkinje fibers
Atrial repolarization –> not visible on ECG because it occurs at the same time as ventricles depolarizing and allows the atrial to be stimulated again
4.) S-T segment
- Ventricular plateau
- Prevents ventricles from repolarizing, allowing time for sarcomeres within ventricles to contract and relax
- Entire ventricular myocardium depolarized
5.) T wave
- Allows ventricles to be repolarized
- Muscles relax
The end of T wave until the beginning of the next P wave = heart resting between beats
What is the P-R interval?
- Goes from the beginning of P wave to beginning of QRS wave (but doesn’t include Q)
- Time required to transmit an action potential through the entire conduction system (SA Node cells –> Purkinje fibers)
- If it’s longer than 0.2 seconds –> slow potential and may be a sign of heart block
What is the Q-T interval?
- Beginning of QRS complex, through ST segment, to end of T wave
- Time required for the action potential to occur within the ventricles
- Between 0.2- 0.4 seconds –> if longer, they may have QT syndrome
Ventricular fibrillation
- Ventricles contract in a chaotic way
- Defibrilizer “tells everyone to be quiet” –> wouldn’t use it on a flatlining patient (they need NE)
What are the two heart sounds and when do they each occur?
Associated with the closing of heart valves
1.) Lubb
- As AV valves close
- Beginning of systole (when blood is ejected from ventricles)
- S1 sound –> Lubb
2.) Dubb
- As SL valves close
- Beginning of diastole (when blood enters ventricles)
- S2 sound –> Dubb
Heart murmurs
- Abnormal heart sounds
- Usually indicates incompetent or stenotic valves
Cardiac cycle
- Blood flow through heart during one complete heartbeat with pressure and blood volume changes
- 1 heartbeat = Atrial systole (AS) –> atrial diastole (AD) –> ventricular systole (VS) –> ventricular diastole (VD)
- Systole = contraction
- Diastole - relaxation
Ventricular balance
- Unequal amounts of blood are pumped by the two ventricles through the two circulations
- Sustained pumping of unequal amounts can lead to edema
What are the names of the cardiac cycle?
1.) Atrial relaxation and ventricular filling
2.) Atrial contraction and ventricular filling
3.) Isovolumic contraction
4.) Ventricular ejection
5.) Isovolumic relaxation
In terms of the atria, ventricles, AV valves, and SL valves, which are open/closed or relaxed/contracted in each of the 5 stages?
1.) Atrial relaxation and ventricular filling
Open: AV
2.) Atrial contraction and ventricular filling
Open: AV
Contracting: Atria
3.) Isovolumic contraction
Contracting: Ventricles
4.) Ventricular ejection
Open: SL
Contracting: Ventricles
5.) Isovolumic relaxation
No valves open
None contracting
What happens in ejection phase?
- Ventricular pressure exceeds pressure in large arteries, forcing SL valves open
Cardiac output (CO)
- Volume of blood pumped by each ventricle in one minute
- A measure of how effective the cardiovascular system is in fulfilling its function
- In a healthy person, it increases during strenuous effort to meet cellular needs
What is the formula for cardiac output (CO)?
CO (mL/min) = Heart rate (HR) x Stroke volume (SV)
Heart rate = Number of beats per minute
Stroke volume = Volume of blood pumped out by one ventricle with each beat
What are the typical amounts for HR and SV and what is the standard CO amount? What is the maximal CO for athletic/nonathletic people?
HR ~75 beats/min
SV ~70 mL/beat
CO ~ 5.25 L/min
Maximum CO (non-athletic): may be 4-5 resting CO
Maximum CO (athletic): May reach 35 L/min resting CO
Cardiac reserve
- Difference between resting and maximal CO
Cardiac reserve = CO during exercise - CO at rest
What is the formula for SV?
Stroke volume (SV) = End diastolic volume (EDV) - End systolic volume (ESV)
End diastolic volume (EDV)
- The volume of blood in each ventricle at the end of ventricular diastole (relaxation)
- How much do you have before you eject
- Affected by length of ventricular diastole and venous pressure
End systolic volume (ESV)
- Volume of blood remaining in each ventricle after systole (contraction)
- At the end of squeezing, how much blood is left
What 3 factors affect SV?
1.) Preload –> how much blood you’re loading the heart with before you eject
2.) Contractility –> How strong myocardium is
3.) Afterload –> The pressure you’re trying to overcome
Preload
- Degree of stretch of cardiac muscle cells before they contract (Frank-Starling law of heart)
- At rest, cardiac muscle cells are shower than optimal length
- Venous return (amount of blood returning to heart) –> most important factor stretching cardiac muscle = EDV
- EDV volume determines preload (slow heartbeat and exercise increases venous return)
Contractility
- (force of contraction) Contractile strength at a given muscle length, independent of muscle stretch and EDV
- Sympathetic stimulation –> More Ca2+ –> more cross bridges
- Increased by positive inotropic agents
- Decreased by negative inotropic agents
What are examples of positive and negative inotropic agents?
Positive inotropic agents –> Thyroxine, glucagon, epinephrine, norepinephrine, digitalis, high extracellular Ca2+
Negative inotropic agents –> Acidosis, increased extracellular K+, Ca2+ channel blockers
Afterload
- Pressure ventricles must overcome to eject blood
- Hypertension increases afterload –> increased ESV and reduced SV
What hormones stimulate heart rate?
1,) Norepinephrine and epinephrine (epinephrine increases heart rate and contractility)
2.) Thyroxine –> increase heart rate by enhancing effects of norepinephrine and epinephrine
What are chronotropic agents and what are the types?
- Factors that can change heart rate
Positive chronotropic agents: Causes an increase in heart rate and include sympathetic stimulation and certain types of hormonal stimulation (ex: thyroid hormone increases about of β1 receptors)
Negative chronotropic agents: Decrease heart rate
Atrial reflex (bainbridge reflex)
- Protects heart from overfilling
- Initiated when baroreceptors (sense blood pressure) in atrial walls are stimulated by an increase in venous return
What is hypocalcemia and what does it do to the heart?
Hypocalcemia: Low Ca2+ levels
- Depresses heart
What is hypercalcemia and what does it do to the heart?
Hypercalcemia: High Ca2+ levels
- Increases HR and contractility
What is hypokalemia and what does it do to the heart?
Hypokalemia: Low K+ levels
- Can result in feeble heartbeat
- Can lead to arrhythmias
What is hyperkalemia and what does it do to the heart?
Hyperkalemia: High K+ levels
- Alters electrical activity –> can lead to heart block and cardiac arrest
Tachycardia vs bradycardia
1.) Tachycardia –> abnormally fast heart rate (>100 beats/min)
2.) Bradycardia –> Heart rate slower (<60 beats/min)
Congestive heart failure (CHF)
- Blood not being pumped –> Blood stays in heart –> heart gets congested –> blood may backflower
- Progressive condition
- CO is so low that blood circulation inadequate to meet tissue needs
- Reflects weakened myocardium
What is pulmonary congestion?
Left side fails –> blood backs up in lungs
What is peripheral congestion?
- Right side fails –> blood pools into body organs –> edema
Moderator band/ septomarginal trabecula
- A muscular band in right ventricle
- extends from interventricular septum to anterior papillary muscles
- main function is to carry part of the right bundle branch of the conduction system
Ligamentum arteriosum
- A small, fibrius band of tissue that connectd the pulmonary trunk to the aortic arch
