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Questions and Answers
What is the primary role of the annulus fibrosus in the heart?
What is the primary role of the annulus fibrosus in the heart?
Which artery typically supplies the SA node the most effectively?
Which artery typically supplies the SA node the most effectively?
In the context of coronary artery dominance, what is indicated by a 15% occurrence?
In the context of coronary artery dominance, what is indicated by a 15% occurrence?
What can be concluded about the branches of coronary arteries?
What can be concluded about the branches of coronary arteries?
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Which anatomical structure is NOT included in the contents of the middle mediastinum?
Which anatomical structure is NOT included in the contents of the middle mediastinum?
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What is the consequence of slower progression in coronary artery disease regarding the smaller arterial branches?
What is the consequence of slower progression in coronary artery disease regarding the smaller arterial branches?
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What is the primary composition of the fibrous pericardium?
What is the primary composition of the fibrous pericardium?
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In what position do the structures of the middle mediastinum typically sag due to gravity?
In what position do the structures of the middle mediastinum typically sag due to gravity?
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Which statement best describes the relationship of the fibrous pericardium to the diaphragm?
Which statement best describes the relationship of the fibrous pericardium to the diaphragm?
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Which of the following nerves accompany the pericardiacophrenic vessels in the middle mediastinum?
Which of the following nerves accompany the pericardiacophrenic vessels in the middle mediastinum?
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What is the primary consequence of fused valve cusps in pulmonary stenosis?
What is the primary consequence of fused valve cusps in pulmonary stenosis?
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Which component of the heart is primarily responsible for receiving blood from the pulmonary veins?
Which component of the heart is primarily responsible for receiving blood from the pulmonary veins?
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What is the function of the bicuspid valve during ventricular contraction?
What is the function of the bicuspid valve during ventricular contraction?
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Which part of the left atrium serves as the primary reservoir for blood returning from the lungs?
Which part of the left atrium serves as the primary reservoir for blood returning from the lungs?
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What is a possible clinical consequence of thrombi forming in the left atrium?
What is a possible clinical consequence of thrombi forming in the left atrium?
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What structure connects the papillary muscles to the tricuspid valve cusps?
What structure connects the papillary muscles to the tricuspid valve cusps?
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Which component separates the inflow portion from the outflow tract in the right ventricle?
Which component separates the inflow portion from the outflow tract in the right ventricle?
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Which valves prevent backflow of blood into the heart chambers?
Which valves prevent backflow of blood into the heart chambers?
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What is the primary consequence of pericardial effusion on heart function?
What is the primary consequence of pericardial effusion on heart function?
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Which condition results in the accumulation of blood within the pericardial cavity?
Which condition results in the accumulation of blood within the pericardial cavity?
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During ventricular contraction, what action occurs to prevent the tricuspid valve from inverting?
During ventricular contraction, what action occurs to prevent the tricuspid valve from inverting?
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What is the primary role of the pulmonary valve?
What is the primary role of the pulmonary valve?
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What is the function of pericardiocentesis?
What is the function of pericardiocentesis?
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Which part of the right ventricle is responsible for the majority of its anterior surface?
Which part of the right ventricle is responsible for the majority of its anterior surface?
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Where is the apex of the heart located?
Where is the apex of the heart located?
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What structure serves as a shortcut for the right bundle of the AV bundle to the anterior wall of the right ventricle?
What structure serves as a shortcut for the right bundle of the AV bundle to the anterior wall of the right ventricle?
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During which condition does the superior vena cava (SVC) get compressed?
During which condition does the superior vena cava (SVC) get compressed?
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What feature characterizes the valve anatomy of the tricuspid valve?
What feature characterizes the valve anatomy of the tricuspid valve?
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Which statement accurately describes cardiomegaly?
Which statement accurately describes cardiomegaly?
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What structures enter the base of the heart?
What structures enter the base of the heart?
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Which anatomical feature is primarily located at the posterior aspect of the heart?
Which anatomical feature is primarily located at the posterior aspect of the heart?
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What are the primary components controlling heart rate and force of contractions?
What are the primary components controlling heart rate and force of contractions?
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In which spinal cord segments do the axons of afferent pain fibers from the heart primarily enter?
In which spinal cord segments do the axons of afferent pain fibers from the heart primarily enter?
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Which of the following areas is located in the traditional auscultatory area for the mitral valve?
Which of the following areas is located in the traditional auscultatory area for the mitral valve?
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What effect does sympathetic stimulation have on the nodal tissue of the heart?
What effect does sympathetic stimulation have on the nodal tissue of the heart?
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Which statement correctly describes the cardiac plexus?
Which statement correctly describes the cardiac plexus?
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How does parasympathetic stimulation affect the heart?
How does parasympathetic stimulation affect the heart?
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Which vessels are contained within the pericardial sac?
Which vessels are contained within the pericardial sac?
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What phenomenon describes the perception of heart pain in areas outside the heart?
What phenomenon describes the perception of heart pain in areas outside the heart?
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Which structure primarily receives blood from the great cardiac vein, middle cardiac vein, and small cardiac vein?
Which structure primarily receives blood from the great cardiac vein, middle cardiac vein, and small cardiac vein?
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What initiates the electrical impulses that regulate the heartbeat?
What initiates the electrical impulses that regulate the heartbeat?
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Where do the lymphatics of the myocardium primarily drain?
Where do the lymphatics of the myocardium primarily drain?
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What phase of the cardiac cycle begins with the closure of the aortic and pulmonary valves?
What phase of the cardiac cycle begins with the closure of the aortic and pulmonary valves?
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Which characteristic is true of the AV node compared to the SA node?
Which characteristic is true of the AV node compared to the SA node?
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During which part of the cardiac cycle do the atrioventricular valves close?
During which part of the cardiac cycle do the atrioventricular valves close?
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What structure provides collateral circulation to the myocardium?
What structure provides collateral circulation to the myocardium?
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What is the primary function of the cardiac impulse-conducting system?
What is the primary function of the cardiac impulse-conducting system?
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What role does the fibrous trigone play in the structure of the heart?
What role does the fibrous trigone play in the structure of the heart?
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How does the left coronary artery primarily contribute to the heart's blood supply?
How does the left coronary artery primarily contribute to the heart's blood supply?
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What is a key characteristic of the branches of the coronary arteries?
What is a key characteristic of the branches of the coronary arteries?
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Which clinical condition is characterized by sudden occlusion of a major coronary artery?
Which clinical condition is characterized by sudden occlusion of a major coronary artery?
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What percentage of individuals typically exhibit a dominant left coronary artery system?
What percentage of individuals typically exhibit a dominant left coronary artery system?
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What is the significance of a single coronary artery?
What is the significance of a single coronary artery?
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What is the common outcome of atherosclerosis affecting the coronary arteries?
What is the common outcome of atherosclerosis affecting the coronary arteries?
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What anatomical feature separates the atrial musculature from the ventricular musculature?
What anatomical feature separates the atrial musculature from the ventricular musculature?
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Study Notes
Right Ventricle
- Forms the largest part of the anterior surface and inferior border of the heart
- Contains irregular muscular elevations called trabeculae carneae
- Papillary muscles, attaching to the ventricular wall on one end, connect to chordae tendineae on the other end, which attach to the cusps of the tricuspid valve
- There are three papillary muscles: anterior, posterior, and septal
- The septomarginal trabecula, or moderator band, is a specialized trabecula that bridges the inferior interventricular septum to the anterior papillary muscle base.
- It acts as a shortcut for the right bundle of the AV bundle to the anterior wall of the right ventricle
- The conus arteriosus is a smooth-walled outflow tract to the pulmonary trunk.
- The pulmonary valve is located at its apex
- The supraventricular crest separates the muscular inflow part from the smooth-walled conus arteriosus (outflow)
Tricuspid Valve
- Closes off the right atrioventricular orifice during ventricular contraction
- Consists of three cusps: anterior, septal, and posterior
- The base of each cusp is secured to a fibrous ring that maintains the shape of the atrioventricular orifice
- The free margins of the cusps are attached to chordae tendineae
- The cusps project into the ventricle and open the valve while the right ventricle fills
- Papillary muscles contract during ventricular contraction, pulling the cusps closed and preventing backflow into the right atrium
Pulmonary Valve
- Closes the outflow tract between the right ventricle and pulmonary trunk
- Consists of three semilunar cusps: left, anterior, and right, forming pocket-like sinuses
- After ventricular contraction, the sinuses fill with blood, forcing the cusps closed and preventing backflow into the right ventricle
Middle Mediastinum
- Located within the inferior mediastinum, between the transverse thoracic plane (level of the sternal angle and intervertebral disc of T4/T5 vertebra) and the diaphragm
- Contents include:
- Pericardium
- Heart
- Roots of great vessels (ascending aorta, pulmonary trunk, SVC)
- Arch of azygos vein
- Main bronchi
- Phrenic nerves accompanied by pericardiacophrenic vessels
- The levels of viscera within the middle mediastinum can vary depending on the patient's position (supine vs. standing)
Pericardium
- Lies deep to the mediastinal parietal pleura
- Composed of two layers:
-
External sac: Fibrous pericardium
- Outer layer of dense connective tissue
- Bound to the central tendon of the diaphragm
- Fused with the tunica adventitia of great vessels (at the level of the sternal angle)
- Anteriorly attached to the sternum by sternopericardial ligaments
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Internal sac: Serous pericardium
- Consists of two layers: parietal pericardium (fused to fibrous pericardium) and visceral pericardium (epicardium)
- The pericardial cavity is a potential space between the parietal and visceral pericardium, filled with a small amount of serous fluid
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External sac: Fibrous pericardium
Clinical Notes: Pericardium
- The fibrous pericardium, being tough and inelastic, protects the heart against abrupt overfilling.
- Pericardial effusion, the leaking of fluid from pericardial capillaries into the pericardial cavity, can lead to extensive fluid build-up, preventing the heart from expanding and limiting blood inflow to the ventricles, resulting in cardiac tamponade due to the unyielding fibrous sac.
- Cardiomegaly, the slow increase in heart size, allows for enlargement to occur without compression.
- Hemopericardium, the entry of blood into the pericardial cavity (e.g., from a stab wound or weakened area of the heart muscle after a heart attack), can lead to heart compression, circulatory failure, and SVC compression, engorging veins in the face and neck.
- Pericardiocentesis, the drainage of serous fluid from the pericardial cavity, relieves cardiac tamponade.
Heart
- Serves as two muscular pumps propelling blood to the body
- Approximately the size of a clenched fist
- The right side receives low-oxygen blood from the SVC/IVC and sends it to the pulmonary trunk for oxygenation
- The left side receives high-oxygen blood from the pulmonary veins and sends it to the aorta for systemic distribution
- The right and left atria are receiving chambers
- The right and left ventricles are discharging chambers
External Anatomy of the Heart
- Located posterior to the sternum, costal cartilages, and medial ends of ribs 3-5 on the left side
- Sits obliquely, with approximately 2/3 to the left and 1/3 to the right of the median plane
-
Apex:
- Left inferolateral part of the left ventricle
- Posterior to the left 5th intercostal space (8-9 cm from the midsternal line)
- Directed downward and to the left ~45 degrees from the median plane
- More anteriorly located than the base
-
Base:
- Posterior aspect of the heart
- Mainly composed of the left atrium
- Faces posteriorly toward the vertebral bodies of T6-T9
- Between the bifurcation of the pulmonary trunk and the coronary groove
The great veins enter the base of the heart:
- The pulmonary veins enter the right and left sides of the left atrium
- The SVC/IVC enter the upper and lower ends of the right atrium, respectively
Clinical Notes: External Anatomy
- Pulmonary stenosis:
- Valve cusps fuse, narrowing the pulmonary valve
- Infundibular pulmonary stenosis: conus arteriosus is underdeveloped, restricting right ventricular outflow
Left Atrium
- Derived embryologically from two structures: a smooth wall and a muscular portion
- The posterior half receives blood from four pulmonary veins, having smooth walls.
- The smaller muscular auricle is in the anterior half, with no distinct structure to separate it from the smooth-walled portion.
- The interatrial septum forms part of the anterior wall.
- A thin area/depression called the valve of the foramen ovale is present.
- Is the probe patent in your cadaver?
- Blood passes from the left atrium to the left ventricle through the left atrioventricular orifice.
- It is closed during ventricular contraction by the bicuspid valve.
- Blood entering the left ventricle from the left atrium moves forward toward the apex
- Clinical importance: Thrombi (immobile blood clots) form on the wall of the left atrium. When they detach, they become emboli (mobile clots) and can occlude an artery
Left Ventricle
- Forms most of the heart base
- Longer than the right ventricle, with the thickest layer of myocardium
- Lies anterior to the left atrium and forms the apex
- Makes up nearly all of the left surface/border and diaphragmatic surface
- Has a thicker layer of myocardium than the right ventricle since arterial pressure is higher in the systemic circulation compared to the pulmonary circulation
- Contains trabeculae carneae, papillary muscles, and chordae tendineae associated with the bicuspid valve.
- Blood flows from the apex of the ventricle toward the base during ventricular contraction, entering the aorta
Bicuspid Valve
- Closes off the left atrioventricular orifice during ventricular contraction
- Consists of two cusps: anterior and posterior
- The base of each cusp is secured to a fibrous ring that maintains the shape of the atrioventricular orifice
- The free margins of the cusps are attached to chordae tendineae
- The cusps project into the ventricle and open the valve while the left ventricle fills
- Papillary muscles contract during ventricular contraction, pulling the cusps closed and preventing backflow into the left atrium
Aortic Valve
- Closes the outflow tract between the left ventricle and the aorta
- Consists of three semilunar cusps: right, left, and posterior, forming pocket-like sinuses
- After ventricular contraction, the sinuses fill with blood, forcing the cusps closed and preventing backflow into the left ventricle
Internal anatomy of the Heart
- Atrial septum
- Ventricular septum
- 4 fibrous rings
- Right and left fibrous trigone: areas of thickened connective tissue between the rings
- The fibrous rings maintain the integrity of the openings they surround, provide attachment points for cusps and myocardium, separate the atrial from ventricular musculature, and act as a partition of dense connective tissue to electrically isolate the atria from the ventricles, leaving the AV bundle as the single connection between the two groups of myocardium.
Coronary Vasculature
- Arterial blood supply to the heart:
- Right coronary artery
- Supplies the SA node (60%), AV node (80%), right atrium, most of the right ventricle, part of the left ventricle, and part of the interventricular septum
- Branches: SA nodal branch, right marginal branch, AV nodal branch, and posterior interventricular artery
- Left coronary artery
- Supplies the SA node (40%), left atrium, most of the left ventricle, part of the right ventricle, and most of the interventricular septum
- Branches: SA nodal branch, anterior interventricular artery, circumflex branch, and left marginal branch
- Right coronary artery
Clinical Notes: Coronary Vasculature
- Variations of coronary arteries:
- Normally, there is a 50/50 blood supply contribution from the LCA and RCA.
- In 15% of cases, the LCA is dominant, with the posterior interventricular branch arising off of the circumflex.
- A single coronary artery can occur.
- The circumflex can arise directly from the right aortic sinus.
- An accessory coronary artery can occur in 4% of cases.
- The branches of coronary arteries are considered end arteries, supplying myocardium without functional overlap. However, smaller branches do anastomose, and the functional value of this is apparent in slowly progressive coronary artery disease.
Heart Anatomy
- The heart is located in the middle mediastinum, within the pericardial sac
- The fibrous pericardium is a tough, fibrous sac that encloses the heart
- The fibrous pericardium helps to maintain the integrity of the openings it surrounds and provides attachment points for cusps and myocardium.
- The fibrous pericardium separates atrial from ventricular musculature
- The fibrous pericardium serves as a partition of dense connective tissue to electrically isolate the atria from the ventricles, leaving the A/V bundle as the single connection between the two groups of myocardium.
Coronary Vasculature
-
Right coronary artery supplies: right atrium, most of right ventricle, part of left ventricle, part of IV septum, SA node (60%), AV node (80%)
- SA nodal branch supplies the SA node
- Right marginal branch supplies the right border of the heart
- AV nodal branch supplies the AV node
- Posterior IV artery supplies the posterior interventricular artery
-
Left coronary artery supplies : left atrium, most of left ventricle, part of right ventricle, most of IV septum, SA node (40%)
- SA nodal branch supplies the SA node
- Anterior IV artery supplies the anterior interventricular artery
- Circumflex branch supplies the posterior surface
- Left marginal branch branches off the circumflex and supplies the left ventricle
-
Clinical Importance: Variations of coronary arteries:
- Normally, there is a 50/50 blood supply contribution from LCA & RCA
- In 15% of cases, LCA is dominant, and the posterior IV branch comes off the circumflex
- In some cases, there is a single coronary artery
- In some cases, the circumflex arises directly from the right aortic sinus
- In 4% of cases, an accessory coronary artery is present
-
End Arteries: Branches of coronary arteries are considered end arteries, but smaller branches anastomose and functional value of this is apparent in slowly progressive coronary artery disease
-
Clinical Importance: Myocardial infarction (MI) is a major artery that is suddenly occluded by an embolus, myocardium in that region becomes infarcted. MI is an area of myocardium that is necrotic. Atherosclerosis of coronary arteries → coronary insufficiency → ischemic heart disease; often characterized by angina pectoris (pain in substernal region and down medial side of the left arm and forearm).
Venous Drainage
- The heart drains via the coronary sinus (primary) and anterior cardiac veins → right atrium (secondary)
- The coronary sinus receives the great cardiac vein, middle and small cardiac veins
- The left posterior vein and left marginal vein → coronary sinus
- Smallest cardiac veins – capillary beds of myocardium → atria (provide collateral circulation to musculature)
Lymphatic Drainage
- Myocardium and subepicardial connective tissue → subepicardial lymphatic plexus
- The lymphatic plexus travels along the coronary groove → ends in inferior tracheobronchial lymph nodes
Conducting System of Heart
- The impulse-conducting system coordinates the cardiac cycle
- The impulse-conducting system consists of cardiac muscle cells & highly specialized conducting fibers for initializing impulses and conducting them through the heart
- Nodal tissue initiates heartbeat & coordinates contractions
-
SA node:
- Impulse 70x/min
- Pacemaker of heart
- Located just deep to epicardium, junction of SVC & right atrium
-
AV node:
- Smaller collection of nodal tissue
- Just posteroinferior of interatrial septum, near coronary sinus opening
-
SA node:
Cardiac Cycle
- The cardiac cycle is the complete movement of the heart; the period from the beginning of one heartbeat to the beginning of the next.
- The cardiac cycle consists of diastole (ventricular filling) and systole (ventricular emptying).
-
Diastole:
- The aortic and pulmonary valves close
- The atrioventricular valves open during early stages of diastole
- Atrial contraction occurs during the final moments of diastole
-
Systole:
- The atrioventricular valves (tricuspid and mitral) close very soon after systole begins
- The aortic and pulmonary valves open during systole
-
Diastole:
Innervation of the Heart:
-
Cardiac Plexuses
- Located anterior to bifurcation of the trachea, posterior to the ascending aorta, superior to the bifurcation of the pulmonary trunk
- The Autonomic division of the PNS is only in the atria to any specific degree and very little in ventricles. It is therefore directly responsible for regulating heart rate and force of atrial contraction and no direct effect on ventricles.
- Sympathetic stimulation of the nodal tissue increases heart rate and the force of cardiac contractions
- Parasympathetic stimulation slows the heart rate, saving energy
- Branches from both parasympathetic and sympathetic contribute to the cardiac plexus
- Visceral afferents from the heart are also part of the cardiac plexus
Clinical Importance: Cardiac Pain
- The heart is insensitive to touch and temperature
- Ischemia can stimulate pain endings in the myocardium
- Pain fibers enter spinal cord segments T1 – T4/5, especially on the left side
- Referred cardiac pain is a phenomenon whereby stimuli originating in the heart is perceived as pain arising from a superficial body part – e.g., skin on the medial aspect of left upper limb
Auscultatory Areas of the Heart
- The traditional valve areas are not the anatomical positions of the valves, but where they are best heart based on sound projections related to blood flow
- Aortic valve area: 2nd right intercostal space
- Pulmonic valve area: 2nd left intercostal space
- Mitral valve area: 5th intercostal space
- Tricuspid valve area: left lower sternal border
Great Vessels
- The pulmonary trunk is contained within the pericardial sac, along with the ascending aorta.
- The pulmonary trunk arises from the conus arteriosus and divides into left and right pulmonary arteries between TV5-TV6
- The ascending aorta originates at the aortic orifice and moves superiorly to the level of the 2nd right costal cartilage, where it enters the superior mediastinum and becomes the arch of the aorta.
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Description
This quiz explores the anatomy and functions of the right ventricle and the tricuspid valve in the human heart. Participants will learn about important structures such as papillary muscles, trabeculae carneae, and the conus arteriosus. Test your knowledge on how these components work together to facilitate proper blood flow and heart function.
