Heart Anatomy I and II Flashcards
What are the superior, inferior, anterior, and posterior borders of the mediastinum?
Superior = superior thoracic aperture
Inferior = diaphragm
Anterior = sternum + costal cartilages
Posterior = thoracic vertebrae
The inferior mediastinum is subdivided by the ___________ into 3 parts
Pericardium
The inferior mediastinum is subdivided by the pericardium into anterior, middle, and posterior parts. What structures are found in the middle subdivision?
Pericardium and its contents = heart, ascending aorta, pulmonary trunk, SVC
Is it possible for structures to exist in more than one mediastinal compartment?
Yes, some structures like the esophagus pass vertically and lie in more than one mediastinal compartment
The pericardium covers the heart and beginnings of the great vessels. It is a closed sac composed of what 2 major layers?
Fibrous pericardium = tough external layer
Serous pericardium = composed mainly of mesothelium (single layer of flattened cells)
The fibrous pericardium is continuous with the _____ _____ of the diaphragm. The internal surface is lined with a parietal layer of _______ pericardium, which is also reflected onto the heart at the great vessels.
Central tendon; serous
The fibrous pericardium is continuous superiorly with what 2 layers of named connective tissue?
- Tunica adventitia (perivascular connective tissue of great vessels entering and leaving the heart)
- Pretracheal layer of deep cervical fascia
The fibrous pericardium is attached anteriorly to the posterior surface of the sternum by what structures?
Sternopericardial ligaments (which are highly variable in their development)
The fibrous pericardium is bound posteriorly by _____ _______ to structures in the ______ ______
Loose CT; posterior mediastinum
The fibrous pericardium is continuous inferiorly with the central tendon of the diaphragm. What ligament forms the site of continuity?
Pericardiacophrenic ligament
[however, note that fibrous pericardium and central tendon are NOT separate structures that fused together secondarily, nor are they separable by dissection]
Overall, what connections are involved in tethering the heart inside the fibrous pericardium?
Tunica adventitia, pretracheal layer of deep cervical fascia, sternopericardial ligaments, loose connective tissue, and pericardiacophrenic ligament connecting to the central tendon of the diaphragm
The serous pericardium is composed mainly of mesothelium - a single layer of flattened cells forming an epithelium that lines both the internal surface of the fibrous pericardium and the external surface of the heart. What are the 2 layers of the serous pericardium?
Visceral layer - forms the epicardium (outermost layer of the heart wall)
Parietal layer - where the aorta and pulmonary trunk leave the heart, and where the SVC, IVC, and pulmonary veins enter
Where do the visceral and parietal layers of serous pericardium become continuous?
At the beginning of the great vessels
What provides the main arterial supply to the pericardium?
Pericardiacophrenic a. (slender branch of internal thoracic a.)
The main arterial supply to the pericardium is the pericardiacophrenic a., which is a slender branch of the ______ ______ artery and often accompanies the _______ nerve to the diaphragm
Internal thoracic
Phrenic
The main arterial supply to the pericardium is the pericardiacophrenic a.. What arteries provide smaller contributions?
Musculophrenic a. (Terminal branch of internal thoracic a.)
Bronchial, esophageal, and superior phrenic aa. (Branches of thoracic aorta)
Coronary aa. (First branches of aorta; supply visceral layer of pericardium only!)
Smaller contributions to the arterial supply of the pericardium include the following:
Musculophrenic a.
Bronchial, esophageal, and superior phrenic aa.
Coronary aa.
What arteries do the above branch off of?
Musculophrenic - internal thoracic a.
Bronchial, etc. - thoracic aorta
Coronary aa. - aorta (remember only supplying visceral pericardium)
What provides venous drainage of pericardium?
Pericardiacophrenic veins (tributaries of the brachiocephalic or internal thoracic vv.)
Variable tributaries of the azygous venous system
The pericardiacophrenic veins provide venous drainage to the pericardium. What are these veins tributaries of?
Brachiocephalic or internal thoracic veins
What nerves provide innervation to the pericardium?
Phrenic nerves (C3-5)
Vagus nn.
Sympathetic trunks
Innervation to the pericardium is provided by the phrenic nerves, vagus nerves, and sympathetic trunks. Which of those is the primary source of sensory fibers?
Phrenic nerves (C3-C5)
Pain sensations conveyed are commonly referred to skin (C3-5 dermatomes) of ipsilateral supraclavicular region
Innervation to the pericardium is provided by the phrenic nerves, vagus nerves, and sympathetic trunks. The phrenic nerves are the primary source of sensory innervation. What are the functions of the other 2?
Vagus nerves - function uncertain
Sympathetic trunks - vasomotor
What structure, found posterior to the intrapericardial parts of the pulmonary trunk and ascending aorta, anterior to the SVC, and superior to the heart atria, forms a passage within the pericardial cavity between 2 groups of vessels and the reflections of serous pericardium surrounding them?
Transverse pericardial sinus
The transverse pericardial sinus forms a transversely running passage within the pericardial cavity between what 2 groups of vessels (and the reflections of serous pericardium surrounding them)?
- Aorta and pulmonary trunk
2. SVC, IVC, pulmonary veins
What is the surgical significance of the transverse pericardial sinus?
After the pericardial sac is opened anteriorly, a finger can be passed through this sinus posterior to the ascending aota and pulmonary trunk.
By passing a surgical clamp or ligature around these vessels, inserting the tubes of a coronary bypass machine, then tightening the ligature, surgeons can stop or divert the circulation of blood in these arteries while performing cardiac surgery such as coronary bypass grafting.
What structure forms a wide, pocket-like recess in the pericardial cavity posterior to the base of the heart (formed by left atrium)?
Oblique pericardial sinus
The oblique pericardial sinus is bounded laterally by the pericardial reflections surrounding the pulmonary veins and ______, and posteriorly by the pericardium overlying the anterior aspect of the _________.
It can be entered inferiorly and will admit several fingers, but they cannot pass around any of these structures because the sinus is a ______ sac.
IVC; esophagus
Blind
What is cardiac tamponade its symptoms?
Heart compression due to fluid in the fibrous pericardium, which compromises heart function and therefore circulation fails.
Symptoms: engorged veins in face and neck (due to backup of blood beginning where the SVC enters the pericardium), chest pain, low blood pressure, fainting, lightheadedness, tachycardia, shortness of breath or tachypnea, distant heart sounds, swelling in extremities
Cardiac tamponade is characterized by compression of the heart within the fibrous pericardium. What might cause this compression?
Extensive pericardial effusion (fluid in heart cavity)
Hemopericardium (blood in heart cavity) - results from perforation of weakened area of heart muscle owing to previous myocardial infarction, bleeding into pericardial cavity after cardiac surgery, or from stab wounds
The apex of the heart is directed anteriorly and to the _____. It is formed by the inferolateral part of the ____ _____.
Left; left ventricle
Describe the position of the apex of the heart relative to body landmarks nearby
Lies posterior to the left 5th intercostal space, usually about 9 cm from the median plane
What part of the heart remains motionless throughout the entire cardiac cycle?
Apex
The base of the heart faces most posteriorly. What chambers of the heart make up the base?
Mainly the left atrium, some from right atrium
Where are the sounds of mitral valve closure maximal?
Apex
Describe orientation/position of the base of the heart relative to body landmarks nearby
The base faces posteriorly toward bodies of vertebrae T6-9 and is separated from them by the pericardium, oblique pericardial sinus, esophagus, and aorta
The base of the heart extends superiorly to the bifurcation of the ________ _______, and inferiorly to the ________ ________
It receives ________ _______ on the right and left sides of its left atrial portion, and ________ at the superior and inferior ends of the right atrial portion
Pulmonary trunk; coronary sulcus
Pulmonary veins; IVC
The right atrium forms the right border of the heart. It receives venous blood from what 3 structures?
SVC, IVC, coronary sinus
What structure forms a conical muscular pouch that projects from the right atrium like an add-on room, increasing the capacity of the atrium as it overlaps the ascending aorta?
Right auricle
The interior of the right atrium is characterized by:
_______ ______ = smooth, thin-walled, posterior part which the SVC, IVC, and coronary sinus open into, bringing poorly oxygenated blood into the heart
Rough, muscular anterior wall composed of _______ muscle.
Right _______ orifice through which the right atrium discharges poorly oxygenated blood to the right ventricle.
Sinus venarum
Pectinate
Atrioventricular
What structure, associated with the right atrium, forms the external separation of the rough and smooth atrial wall?
Sulcus terminalis (terminal groove)
What structure, associated with the right atrium, forms the internal separation of rough and smooth atrial wall?
Crista terminalis
What structure separates the right and left atria? What embryologic remnant would you find here?
Interatrial septa
Fossa ovalis = remnant of foramen ovale in fetus
Which heart chamber forms the largest part of the anterior surface and almost the entire inferior border of the heart?
Right ventricle
______ ______ refers to the superior taper of the right ventricle, leading to the pulmonary trunk
Conus arteriosus
_______ ______ are irregular muscular elevations found in the interiors of the right and left ventricles
Trabeculae carnae
Compare the trabeculae carnae found in the right vs. left ventricles
Those in the left ventricle are finer and more numerous than in the right ventricle
What structure associated with the right ventricle separates the ridged muscular wall of the inflow part of the chamber from the smooth wall of the conus arteriosus (outflow part)?
Supraventricular crest
What valve forms the inflow part of the right ventricle?
Right atrioventricular valve (tricuspid valve)
Describe the location of the right AV (tricuspid) valve relative to body landmarks
Right AV valve is located posterior to body of sternum at the level of 4th and 5th intercostal spaces
The right AV (tricuspid) valve is surrounded by fibrous rings of the _____ of the heart.
_______ _______ attach to the free edges and ventricular surfaces of the anterior, posterior, and septal cusps.
Skeleton
Chordae tendinae
Chordae tendinae arise from ______ muscles, which are conical muscular projections with bases attached to the ventricular wall
Papillary
How do papillary muscles prevent right AV valve prolapse?
They begin to contract before RV contraction, tightening the chordae tendinae and drawing the cusps together, thus preventing prolapse
Describe the 3 papillary muscles associated with the right AV valve. Which one is the largest? What do their chordae tendinae attach to?
Anterior - largest, most prominent, found on anterior wall of RV. Chordae tendinae attach to anterior and posterior cusps of tricuspid valve.
Posterior - arises from inferior wall of RV. Chordae tendinae attach to posterior and septal cusps of tricuspid valve.
Septal - arises from interventricular septum. Chordae tendinae attach to anterior and septal cusps of tricuspid valve.
Describe the position/location of the pulmonary valve relative to body landmarks
Pulmonary valve is found at the apex of the conus arteriosus, at the level of the 3rd costal cartilage
The valveless pairs of right and left pulmonary veins will enter which chamber of the heart?
Left atrium
What structure, associated with the left atrium, forms the superior part of the left border of the heart and overlaps the root of the pulmonary trunk?
Left auricle
The interior of the left atrium is characterized by:
Large smooth walled muscle part and smaller muscular auricle with _____ muscle.
4 _____veins (2 superior and 2 inferior)
Slightly ______ wall than that of right atrium
___________ septum that slopes posteriorly and to the right
Pectinate
Pulmonary
Thicker
Interatrial
What chamber of the heart forms the apex, nearly entire left surface, and most of the diaphragmatic surface?
Left ventricle
Describe the wall thickness, trabeculae carnae, conical cavity, and papillary muscles relative to the right ventricle
Walls are 2-3x thicker and covered in trabeculae carnae that are finer and more numerous than RV
Longer conical cavity
Larger anterior and posterior papillary muscles
The left ventricle has a smooth-walled, nonmuscular, superoanterior outflow part called the _____ ______, which leads to the aortic orifice and valve
It also has a ______ valve that guards the left AV orifice
The _____ orifice lies in the right posterosuperior part of the LV.
Aortic vestibule
Mitral (bicuspid)
Aortic
What structure forms as the continuation of the right ventricle and divides into the right and left pulmonary arteries, conducting low-oxygen blood to the lungs for oxygenation?
Pulmonary trunk
Which of the great vessels opens into the superior part of the right atrium at the level of the right 3rd costal cartilage?
SVC
Which of the following is not considered a great vessel of the heart?
A. Pulmonary trunk B. Aorta C. Superior vena cava D. Inferior vena cava E. Left coronary artery
E. Left coronary artery
What demarcates the atria from the venticles?
Coronary sulcus (atrioventricular groove)
What demarcates the right and left ventricles from each other?
Anterior and posterior interventricular sulci (grooves)
What are the 4 named surfaces of the heart? Which one forms the cardiac impression in the left lung?
Anterior (sternocostal) surface: formed mainly by right ventricle
Diaphragmatic (inferior) surface: formed mainly by left ventricle
Right pulmonary surface: formed mainly by right atrium
Left pulmonary surface: formed mainly by left ventricle; forms cardiac impression in left lung
The four borders of the heart:
_______ border = slightly convex, formed by right atrium and extends between the SVC and IVC
_______ border = nearly horizontal, formed mainly by right ventricle and slightly by left ventricle
_______ border = oblique+nearly verticle, formed mainly by left ventricle and slightly by left auricle
______ border = formed by right and left atria and auricles in anterior view; ascending aorta and pulmonary trunk emerge and the SVC enters on the right side. Forms inferior boundary of the transverse pericardial sinus
Right
Inferior
Left
Superior
_______ _______ = short venous trunk receiving most of the cardiac veins; located between right AV orifice and IVC orifice
Coronary sinus
_______ ________ =first branches of the aorta, supply the myocardium and epicardium
Coronary arteries (right coronary artery and left coronary artery)
What artery follows the coronary (atrioventricular) sulcus between the atria and ventricles and anastomoses with the circumflex and anterior interventricular arteries?
Right coronary artery
What 6 structures are typically supplied by the right coronary artery?
Right atrium
Most of right ventricle
Part of left ventricle (diaphragmatic surface)
Part of IV septum, usually posterior 1/3
SA node (60% of people)
AV node (80% of people)
What does the right coronary artery anastomose with?
Circumflex and anterior interventricular branches of the left coronary artery
What are the 4 branches of the right coronary artery (typically)?
SA nodal a.
Right marginal a.
Posterior interventricular a. (Comes off LCA in 33% of people)
AV nodal a.
What branch of the right coronary artery passes to the inferior margin of the heart and apex, supplies the right ventricle and apex, and anastomoses with the interventricular branches?
Right marginal a.
Which branch of the RCA ascends to the SA node and supplies both the SA node and the pulmonary trunk?
SA nodal a.
What branch of the RCA runs in the posterior IV groove to the apex of the heart, supplies the right and left ventricles and posterior 1/3 of IVS, and anastomoses with the anterior IV branch of the LCA?
Posterior interventricular a.
What artery arises from the RCA near the origin of the posterior interventricular a. and supplies the AV node?
AV nodal a.
Where does the left coronary artery originate?
Left aortic sinus
What does the LCA typically supply?
Most of left atrium and left ventricle, part of right ventricle, anterior 2/3 of interventricular septum, and AV bundles
May also supply AV node is some people
What are the 3 primary branches of the left coronary artery (typically)?
Anterior interventricular a. (Commonly called LAD)
Circumflex branch
[Posterior interventricular a. comes off LCA in 33% of people]
What are the 2 possible branches of the circumflex branch of the LCA?
SA nodal a. (In 40% of population, otherwise this is a branch of RCA)
Left marginal a.
Which branch of the LCA passes along the anterior IV groove to the apex of the heart and in many people gives rise to a lateral branch which descends on the anterior surface of the heart?
Anterior IV a. (Aka LAD)
What does the anterior interventricular a. (LAD) anasomose with?
Posterior interventricular branch of the RCA at the apex
Which branch of the LCA passes to the left in the AV sulcus and runs to the posterior surface of the heart, supplying the left atrium and left ventricle?
Circumflex branch
The SA nodal a. typically arises from the RCA, ascending to the SA node and supplying that + the pulmonary trunk.
However, it arises from the circumflex branch of the LCA in 40% of people. In this case, what path does it take?
Ascends on and supplies the posterior surface of left atrium and the SA node
The ______ ______ a. branches from the circumflex branch of the LCA and follows the left border of the heart, supplying the left ventricle and anastomosing with the interventricular branches
Left marginal a.
The posterior interventricular artery usually arises from the RCA, running in the posterior IV groove to the apex of the heart and supplying the right and left ventricles as well as posterior 1/3 of the IVS.
However, it may arise from the LCA. What path does it take and what does it supply in this case?
Same path, supplies same structures
What are the 3 named variations in coronary vasculature? Which one is most common?
Right dominant pattern - most common (67%)
LCA dominant (15%)
Codominant (18%)
T/F: Besides right dominant, LCA dominant, and codominant variations in coronary vasculature, several other variations exist.
A few people have only one coronary artery from the right aortic sinus and 4% of people have an accessory coronary artery.
True
Describe the right dominant pattern of coronary vasculature variation
Most common variation
RCA and LCA share equally in blood supply to heart
Describe the left dominant pattern of coronary vasculature variation
Posterior interventricular branch is a branch of the circumflex branch of LCA
Describe the codominant pattern of coronary vasculature variation
Branches of both right and left coronary arteries reach the crux of the heart and give rise to branches that course in or near the posterior interventricular groove
The heart is drained mainly by veins that empty into the ______ ______ and partly by small veins that empty into the _________ _______
Coronary sinus; right atrium
The _____ ______ is the main vein of the heart, forming a wide venous channel that runs from left to right in the posterior part of the coronary sulcus
Coronary sinus
What veins open into the coronary sinus?
Great cardiac v. Middle cardiac v. Small cardiac vv. Left posterior ventricular v. Left marginal v.
What is the main tributary of the coronary sinus?
Great cardiac v.
The great cardiac vein drains the area of the heart supplied by which artery?
LCA
Which vein, which becomes unimportant postnatally, descends over the posterior wall of the left atrium and merges with the great cardiac vein to form the beginning of the coronary sinus?
Oblique vein of left atrium (of marshall)
[this is a remnant of the embryonic left SVC, and it may persist in some by replacing or augmenting the right SVC]
The first part of the great cardiac vein is made up of the _____ _____ vein which begins near the apex and ascends with the anterior interventricular branch of the LCA. It then runs around the left side of the heart with the ________ branch of the LCA to reach the coronary sinus
Anterior interventricular
Circumflex
[note that this is strange because when running around left side of heart, blood is flowing in same direction in the paired artery and vein]
What vein, also known as the posterior interventricular vein, accompanies the posterior interventricular branch which usually arises from the RCA?
Middle cardiac v.
What vein accompanies the right marginal branch of the RCA, and along with the middle cardiac v., drains most areas commonly supplied by the RCA?
Small cardiac v.
Which cardiac veins do not drain via the coronary sinus? Which paths do they take?
Anterior cardiac vv. (Begin over anterior surface of RV, cross over coronary sulcus, end directly on right atrium)
Smallest cardiac vv. (Minute vessels that begin in capillary beds of myocardium and open directly into chambers of the heart, mostly at atria
_______ ________ = shallow vertical groove that externally separates the smooth and rough parts of the right atrial wall
Sulcus terminalis (aka terminal groove)
______ ____ = thumbprint size depression in the interatrial septum separating the atria
Fossa ovalis
__________ _________ = curved muscular bundle that traverses the right ventricular chamber from the inferior part of the IVS to the base of the anterior papillary muscle
Septomarginal trabeculae (aka moderator band)
Why is the septomarginal trabeculae important?
It carries part of the right branch of the AV bundle, a part of the conducting system of the heart to the anterior papillary muscle
It creates a shortcut circuit across the chamber, seems to facilitate conduction time, allowing coordinated contraction of anterior papillary muscle
_______ _______ = patent foramen ovale revealed when a probe is passed through it; result of incomplete fibrous adhesion of the valve in the postnatal closure
Probe patency
______ _______ = strong, obliquely placed partition between right and left ventricles, forming part of each wall
Interventricular septum
What are the 2 parts to the interventricular septum? Which part makes up the majority?
Muscular parts (majority)
Fibrous (membranous) parts
Describe the muscular part of the interventricular septum
Forms majority of septum; has thickness of remained of left ventricular wall due to higher pressure. Bulges into cavity of right ventricle
Describe the fibrous (membranous) part of the interventricular septum
Located superiorly and posteriorly; thin membrane, part of the fibrous skeleton of the heart
Septal cusp of tricuspid valve attaches to the right side in the middle. (Inferior to the cusp, the membrane is the interventricular septum, superior to the cusp it is the atrioventricular septum separating right atrium from left ventricle)
What valve, located between the left ventricle and ascending aorta, is obliquely placed and posterior to the left side of the sternum at the level of the 3rd intercostal space?
Semilunar aortic valve
What landmarks are present where the IVC passes into the inferior right atrium?
Almost in line with SVC at level of 5th intercostal cartilage
Describe features of the cardiac skeleton
Fibrous, complex framework of dense collagen forming 4 fibrous rings that surround the orifices of valves, right and left fibrous trigone, and membranous parts of the interatrial and interventricular septa
What function does the cardiac skeleton serve in terms of the AV and semilunar valves?
Keeps them patent and prevents them from being overly distended by an increased blood volume pumping through
What function does the cardiac skeleton serve in terms of leaflets and cusps of valves?
Serves as a place of attachment
What function does the cardiac skeleton serve in terms of the myocardium?
Provides attachment site for myocardium, which when uncoiled, forms a continuous ventricular myocardial band that originates primarily from the fibrous ring of the pulmonary valve and inserts primarily into the fibrous ring of the aortic valve
What function does the cardiac skeleton serve in terms of the conduction system of the heart?
Forms electrical insulator by separating the myenterically conducted impulses of the atria and ventricles so that they contract independently, and by surrounding and providing passage of the initial part of the AV bundle of the conducting system of the heart
__________ = multiple, rapid, circuitous contractions or twitchings of muscular fibers
Fibrillation
What are the 3 primary causes of fibrillation?
Ischemia - increasing extracellular K+
Injury current - poor repolarization of injured tissue
Infarction or hypertrophy altering conduction pathways
Describe atrial fibrillation and its effects on circulation
Rapid, irregular, uncoordinated contractions of different parts of atrial walls
Ventricles respond at irregular intervals to dysrhythmic impulses from atria but usually circulation remains satisfactory
Describe ventricular fibrillation and its effect on circulation
Rapid, irregular twitching ventricular movements that do not pump, so they do not maintain systemic circulation (including coronary circulation)
Becomes fatal if it persists because there is no effective cardiac output
What condition is characterized by noxious stimuli originating in the heart being perceived as pain arising from a superficial part of the body like the skin of the upper limb?
Cardiac referred pain
The heart is insensitive to touch, cutting, cold, and heat, so what conditions might lead to cardiac referred pain?
Ischemia and accumulation of metabolic products, which stimulate pain endings in the myocardium
How is visceral referred pain transmitted from the heart?
Via visceral afferent fibers accompanying sympathetic fibers
Typically referred to somatic structures or areas such as a limb having afferent fibers with cell bodies in the same spinal ganglion, and central processes that enter the spinal cord through the same posterior roots
______ pain is commonly felt as radiating from the substernal and left pectoral regions to the left shoulder and medial parts of the left upper limb, which is supplied by the _____ ______ nerve of the arm. That nerve is often overlapped by innervation from the _____ ______ branches of the 2nd and 3rd intercostal (intercostobrachial) nn. in their distribution
Anginal
Medial cutaneous; lateral cutaneous
Anginal pain is commonly felt as radiating from the substernal and left pectoral regions to the left shoulder and medial parts of the left upper limb, which is supplied by the medial cutaneous nerve of the arm. That nerve is often overlapped by innervation from the lateral cutaneous branches of the 2nd and 3rd intercostal (intercostobrachial) nn. in their distribution.
Consequently, cardiac pain is referred to the upper limb because spinal cord segments of these nerves (T1-3 are also common to the visceral afferent terminations for the _______arteries
Synaptic contacts may also be made with _____ neurons which conduct impulses to neurons on the right side of comparable areas of the spinal cord, explaining pain in right limbs or back
Coronary; commissural
The SA node is the pacemaker of the heart. Where is it located?
Anterolaterally, just deep to the epicardium at the junction of the SVC and RA near the superior end of the sulcus terminalis
Describe the composition of the SA node
Small collection of nodal tissue, specialized muscle fibers, and associated fibroelastic CT
The SA node initiates regular impulses about 70x/min, which travel myogenically to both atria. It is supplied by the _____ artery which usually arises from the RCA. It is stimulated by the _____ division of the ANS and inhibited by the _____ division
SA nodal; sympathetic; parasympathetic
The AV node is a smaller collection of nodal tissue than the SA node. Where is it located?
Posteroinferior region of interatrial septum near the opening of the coronary sinus
Describe blood supply to the AV node
Supplied by AV nodal a. (Usually branch of RCA)
Note that the AV bundle traverses the center of the IVS, the anterior 2/3 of which is supplied by septal branches of anterior IV branch of LCA
The AV bundle is the only bridge between the atrial and ventricular myocardium. Describe its course
Passes from AV node through fibrous heart skeleton and along membranous portion of interventricular septum
Divides into right and left bundles at the junction of membranous and muscular parts of the IVS, proceeding on each side of the muscular part deep to the endocardium
Once the right and left bundle branches of the AV bundle split into right and left, they form subendocardial branches also known as ________ _______
Purkinje fibers
The ______ bundle extends into the right ventricular wall and stimulates muscle of IVS, anterior papillary m. through the septomarginal trabecula (moderator band) and wall of RV
Right
The _____ bundle divides near its origin into 6 smaller tracts which give rise to subendocardial branches that stimulate the IVS, anterior, and posterior papillary muscles and wall of left ventricle
Left
What provides basic, primary innervation of the heart?
Autonomic fibers from the cardiac plexus
Where is the cardiac plexus found?
Most commonly described as lying on anterior surface of the bifurcation of the trachea; can be divided into superficial and deep components
The primary relationship of the cardiac plexus is to what 2 heart structures?
Posterior aspect of ascending aorta and pulmonary trunk
The cardiac plexus supplies sympathetic and parasympathetic fibers en route to the heart, as well as ______ ______ fibers from the heart
Visceral afferent
Where are the cell bodies presynaptic sympathetic fibers to the heart located?
Intermediolateral cell columns of the superior 5-6 thoracic segments of spinal cord
What are the cell bodies of postsynaptic sympathetic fibers to the heart located? Describe their relationship to heart structures
Cervical and superior thoracic paravertebral ganglia of sympathetic trunks
[they traverse the cardiopulmonary splanchnic nerves and the cardiac plexus to end in the SA and AV nodes and in relation to the terminations of parasympathetic fibers on the coronary arteries]
What are the general effects of sympathetic stimulation of the heart?
Increased heart rate, impulse conduction, force of contraction, and blood flow through the coronary vessels to support the increased activity
What are the results of adrenergic stimulation from sympathetic fibers + indirect suprarenal (adrenal) hormone stimulation on heart activity?
Increase in atrial and ventricular contractility
[most adrenergic receptors on coronary blood vessels are b2-receptors, which when activitated cause relaxation of vascular smooth muscle and there for dilution of arteries (this supplies more O2 and nutrients during periods of increased activity)]
What provides the presynaptic parasympathetic fibers to the heart? What function do these serve?
Fibers of vagus nerves; act as blood pressure and oxygenation sensors
Where are the cell bodies of postsynaptic parasympathetic fibers to the heart located?
Cell bodies (intrinsic ganglia) located in atrial wall and interatrial septum near the SA and AV nodes and along the coronary arteries
Postsynaptic parasympathetic fibers to the heart release ________, which binds to _________ receptors to slow the rate of depolarization of the pacemaker cells and AV conduction as well as decrease atrial contractility
Acetylcholine; muscarinic
What are the effects of parasympathetic stimulation of the heart?
Slows heart rate, reduces force of contraction, constricts coronary arteries (saving energy between periods of increased demand)
Describe the course of afferent pain fibers from the heart to the spinal cord
Afferent pain fibers run centrally in the middle and inferior cervical branches and especially in the thoracic cardiac branches of the sympathetic trunk
Axons of these primary sensory neurons enter spinal cord segments T1-T4/5, especially on the left side
Which 4 coronary arteries are most commonly occluded?
LAD (most common)
Right coronary artery
Circumflex branch of LCA
Root of left coronary artery
What is the single leading cause of death in the US, affecting 1 in 6 people?
Coronary heart disease
[avg age of first heart attack is 64 in men, 70 in women; one coronary event occurs every 25 seconds and one person dies every minute; 785,000 coronary attacks with 195,000 estimated silent attacks each year; 50% of men and 64% of women who died suddenly of coronary heart disease had no previous symptoms]
Is ischemic heart disease lethal to heart muscle? What condition might cause ischemic heart disease?
Non-lethal to heart muscle; caused by atherosclerosis (different effects at rest vs. strain)
What is angina pectoralis? What is a common treatment?
Referred chest pain, treated with nitroglycerin - which stimulates the release of nitric oxide
Are myocardial infarctions lethal to heart muscle? What are some causes of MI?
Yes; may be caused by thrombus (blood clot) or embolism (dislodged thrombus or broken plaque material)
What vessel is commonly used for grafts in cardiac bypass surgery?
Great saphenous vein
What heart sounds can be heard in the 2nd intercostal space at the right sternal margin?
Aortic and semilunar valve
What heart sounds can be heard at the 2nd intercostal space at the left sternal margin?
Pulmonary semilunar valves
What heart sounds can be heart over the heart apex, in the 5th intercostal space in line with middle of the clavicle?
Mitral valves
What heart sounds can typically be heard in the right sternal margin of the 5th intercostal space? What are some variations in where this heart sound can be heard?
Tricuspid valve
May also be heard over sternum or over left sternal margin in 5th intercostal space
Define normal limits for tachycardia vs. bradycardia
Tachycardia = greater than 100 bpm
Bradycardia = less than 50 bpm
