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Questions and Answers
What is the primary function of the myocardium in the heart?
What is the primary function of the myocardium in the heart?
The myocardium is responsible for the contraction and pumping of blood throughout the heart and into the circulation.
Describe the significance of epicardial fat in heart health.
Describe the significance of epicardial fat in heart health.
Epicardial fat acts as a cushioning layer and provides energy, but excessive accumulation can lead to increased risk of cardiovascular disease.
What are the main components of the epicardium structure?
What are the main components of the epicardium structure?
The epicardium comprises a layer of serous membrane, connective tissue, and adipose tissue that provides protection and support to the heart.
In histology, how are cardiac muscle cells characterized?
In histology, how are cardiac muscle cells characterized?
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Explain the anatomical course of the right coronary artery.
Explain the anatomical course of the right coronary artery.
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What role do the coronary vessels play in heart function?
What role do the coronary vessels play in heart function?
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What is the significance of the endocardial layer in heart valves?
What is the significance of the endocardial layer in heart valves?
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How does damage to endothelial cells in heart valves lead to complications?
How does damage to endothelial cells in heart valves lead to complications?
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What is the main function of the myocardium?
What is the main function of the myocardium?
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Describe the structural characteristics of the epicardium.
Describe the structural characteristics of the epicardium.
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What is the significance of epicardial fat in heart function?
What is the significance of epicardial fat in heart function?
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Explain the histological features of cardiac muscle.
Explain the histological features of cardiac muscle.
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What are the primary coronary vessels and their roles?
What are the primary coronary vessels and their roles?
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How does the structure of coronary vessels adapt to their function?
How does the structure of coronary vessels adapt to their function?
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In terms of anatomy, where is the heart located within the thorax?
In terms of anatomy, where is the heart located within the thorax?
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What is the role of the pericardium in heart function?
What is the role of the pericardium in heart function?
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What is the significance of co-dominance in coronary circulation regarding the left ventricle?
What is the significance of co-dominance in coronary circulation regarding the left ventricle?
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How does the blood supply differ between the SA node in the majority of people compared to the minority?
How does the blood supply differ between the SA node in the majority of people compared to the minority?
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Why is an arteriogram or angiogram important in assessing coronary circulation?
Why is an arteriogram or angiogram important in assessing coronary circulation?
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What is the primary drainage route for cardiac veins, and into which chamber does it collect?
What is the primary drainage route for cardiac veins, and into which chamber does it collect?
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Identify two variations in the blood supply to the AV node and their prevalence.
Identify two variations in the blood supply to the AV node and their prevalence.
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What role does the Left Anterior Descending Artery play in coronary circulation?
What role does the Left Anterior Descending Artery play in coronary circulation?
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What are the implications of coronary artery obstruction and the surgical solution known as CABG?
What are the implications of coronary artery obstruction and the surgical solution known as CABG?
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Describe the primary function of the myocardium
Describe the primary function of the myocardium
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what nerves carry parasympathetic innervation?
what nerves carry parasympathetic innervation?
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Study Notes
Anatomy of the Heart
- The heart and pericardium are studied.
- The material was adapted from Mr Kris Phillips and lectured by Maryam Rajid.
- Contact information is provided.
Learning Outcomes (LOS)
-
MACRO LOS:
- Describe the anatomy and histology of the heart and major vessels, including innervation.
- Outline the arrangement of the coronary circulation, innervation, and conduction of the heart.
- Understand specific common clinical examples associated with the cardiorespiratory system.
- Recognise the anatomical structures of the cardiovascular system using chest X-ray (CXR), CT and angiogram.
-
MICRO LOS:
- Describe the location of the heart within the thorax and its orientation, relating this to surface anatomy.
- Describe the compartments and contents of the mediastinum.
- Describe the structure of the pericardium and its role in heart function.
- Describe the structure of the heart, heart valves, and heart wall, and recall key anatomical landmarks.
- Describe the key histology features of the heart wall and valve.
- Describe the innervation and structure of the conduction pathway of the heart.
- Describe the arrangement of coronary circulation.
Lecture Overview
-
PART 1: Heart Location
- Surface anatomy
- Mediastinum
- Orientation
-
PART 2: Heart structure
- Pericardium
- The Heart & Pre-lab activity
- Heart valves
- Heart wall histology
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PART 3: Heart vasculature
- Coronary circulation
-
PART 4: Conduction
- Innervation of the Heart
- Conduction of the Heart
Part 1: Heart Location
- Surface Anatomy
- The mediastinum
- Orientation
What is Surface Anatomy?
- The ability to visualise how anatomical structures in the thorax are related to surface features is fundamental to physical examinations.
Surface Anatomy: Palpable Landmarks
- Bony palpable landmarks of the thoracic cage are useful to locate underlying structures.
- Outline of heart can be traced on the anterior surface of the thorax.
Surface Anatomy: Palpable Landmarks
- Clavicle, Second rib, Body of sternum, Nipple, Xiphoid, Suprasternal notch, Manubrium, Manubriosternal junction (angle of Louis), Costal angle.
- Outline of heart can be traced on the anterior surface of the thorax.
Surface Anatomy: Sternal angle
- Sternal angle: Junction between the manubrium and body of the sternum.
- Also known as Angle of Louis.
Surface Anatomy: Sternal angle
- Structures at the sternal angle: Rib 2, Aortic arch, Tracheal bifurcation, Pulmonary trunk, Ligamentum arteriosum, Azygous vein, Nerves, Thoracic duct, Esophagus
Surface Anatomy: Observable Landmarks
- Anterior axillary fold, Posterior axillary fold, Axillary fossa/Axilla, Jugular notch, Pectoralis major
Surface Anatomy: Lines
- Imaginary lines can be drawn on the surface of the thorax to orient yourself.
- Includes mid-sternal line, Mid-clavicular line , Anterior axillary line, Superior lobe, Middle lobe, Inferior lobe, Ribs V-VIII.
- Useful for procedures and identifying anatomical structures.
Surface Anatomy: Lines
- 'Safe Triangle' - Important area for chest drain insertion.
- Bordered by the lateral edge of pectoralis major, line of the fifth intercostal space, base of the axilla, lateral edge of latissimus dorsi.
Surface Anatomy: Heart
- Located usually between ribs 2 and 5th intercostal spaces.
- Extends from the right medial border of the sternum to the left midclavicular line, with the apex near the left midclavicular line.
- Location can change due to pathology (e.g., cardiomegaly, mediastinal or lung conditions) which moves it inferiorly and laterally toward the axilla.
Surface Anatomy: Heart
- The heart is located between vertebral levels T4-T9.
- When supine: T4/T5 - T8; When standing: T6 - T9
- Structures in motion within the thorax can change the heart's location.
Surface Anatomy: Heart
- Heart attached to the diaphragm via its pericardium.
- Heart borders vary depending on diaphragm position (respiration).
- Pericardium is a fibro-serous sac that covers the heart and the roots of the great vessels.
Heart Location: The Mediastinum
- Mediastinum: The mediastinum is a region in the chest between the lungs.
- It is divided into superior and inferior mediastinum.
- The inferior mediastinum is further subdivided into anterior, middle, and posterior mediastinum.
- Heart located within the pericardium in the middle mediastinum.
Thorax: Divisions
- Thorax divided into mediastinum, right pleural cavity, and left pleural cavity.
- Mediastinal pleura encapsulates most of the mediastinum.
- Blends with the parietal pleura of the lungs laterally.
- Blends with the pericardium internally.
Mediastinum: Divisions
- Divided into superior and inferior mediastinum (by sternal angle)
- Imaginary plane that extends from sternal angle to intervertebral disc T4 and T5.
Mediastinum: Contents overview
- Superior: Thymus, Trachea, Oesophagus, Thoracic duct, Aortic arch, Superior vena cava, Vagus nerve, Phrenic nerve, Recurrent laryngeal nerve, Sympathetic trunk
- Inferior -- Anterior: Thymus (child), Adipose tissue, Internal thoracic vessels, Lymph nodes
- Inferior -- Middle: Heart, Ascending aorta, Superior vena cava, Pulmonary trunk.
- Inferior -- Posterior: Descending aorta, Azygos system, Tracheal duct, Oesophagus, Nerves (n. vagus, sympathetic trunk),
Heart Location Orientation
- The heart is generally shaped like a wedge with the base pointing posteriorly.
- Multiple surfaces contact specific structures (Inferior, Anterior, Right, Left pulmonary).
Orientation: Surfaces
- The heart has a base, anterior, inferior (diaphragmatic), right pulmonary, and left pulmonary surfaces
- Inferior (diaphragmatic) surface: In contact with diaphragm.
- Anterior (sternocostal) surface: Orientated towards the anterior thoracic cage (sternum and ribs)
- Right (pulmonary) surface: In contact with the right lung and pleura.
- Left pulmonary surface: In contact with the left lung and pleura.
Orientation: Anterior surface
- The anterior surface of the heart faces anteriorly
- In contact (via pericardium) with the sternum, costal cartilage, and ribs.
- Some parts have contact with the pleura and lungs.
Orientation: Base
- Posterior surface of the heart.
- Includes the whole of the left atrium and part of the right atrium.
- Majority of great heart vessels come in/go out in this area.
Orientation: Inferior Surface
- The diaphragmatic surface of the heart lies inferiorly.
- Projects from the base towards the apex and is in contact with the diaphragm via the pericardium.
- Coronary sinus is a landmark splitting the base and the inferior surface.
Orientation: Pulmonary surface
- The right and left pulmonary surfaces of the heart are in contact with the right and left pleura and lungs, respectively
- Left pulmonary surface is mainly the left ventricle with some left atrium.
- Right pulmonary surface is mainly the right atrium.
Impressions and grooves of lungs
- Anatomical landmarks showing where vessels pass through the lungs
Orientation: Apex
- The apex of the heart is part of the inferolateral portion of the left ventricle.
- Lies deep to the 5th intercostal space along the midclavicular line
- Clinically important in palpating the apex for heart conditions (e.g., cardiomegaly).
Heart: Chambers
- The heart is a four-chambered structure divided by a septum.
- The right side takes deoxygenated blood from the body and sends it to the lungs to be oxygenated (pulmonary circuit)
- The left side takes newly oxygenated blood from the lungs and sends it to the rest of the body (systematic circuit)
- One-way valves (pulmonary artery and aorta) between the chambers prevent backflow.
Heart: Blood Flow Through The Heart
- Blood flow through the heart involves contractions and relaxations creating continuous flow.
- Right atrium receives deoxygenated blood through vena cava and coronary sinus.
- Right atrium contracts to the right ventricle via the atrioventricular (AV) valve.
- The right ventricle contracts, sending blood via semi-lunar valve to pulmonary trunk.
- Blood is then oxygenated in the lungs.
- Left atrium receives oxygenated blood from the lungs through pulmonary veins.
- Left atrium contracts to the left ventricle via AV valve.
- Left ventricle contracts, sending blood via semi-lunar valve to aorta.
Heart: External Features
- Sulci/Grooves: Internally separating chambers, creating external impressions
- Correlates to internal partitions dividing the heart into Chambers
- Creates a passageway for coronary arteries and veins
- Sulci (plural of sulcus) - Coronary, Anterior interventricular, and Posterior interventricular
Heart: Chambers: Right Atrium
- Receives venous blood (poorly oxygenated) from the superior vena cava, inferior vena cava, and coronary sinus.
- Receives small veins along the surface of the atrium.
Pre-lab Activity: Internal features of the heart chambers
- Pre-lab activity tasks on internal heart structures
Heart chambers: Right atrium (blank copy)
- Blank copy for pre-lab activity, no content provided.
Heart chambers: Right atrium
- Sinus venarum, pectinates muscles, crista terminalis, sulcus terminalis, auricle, fossa ovalis, tricuspid valve are part of the internal aspects
Heart chambers: Right ventricle (blank copy)
- Internal structure of right ventricle to be practiced, no content provided.
Heart chambers: Right ventricle
- Trabeculae carneae, papillary muscles, chordae tendineae, septomarginal trabecula, interventricular septum, conus arteriosus, and semilunar valve.
Heart chambers: Left Atrium & Left Ventricle (blank copy)
- Blank copy for pre-lab activity, no content provided
Heart chambers: Left Atrium
- Internal aspect similar to right atrium (smooth posterior, rough anterior)
- Pulmonary veins, left auricle, interatrial septum, valve of foramen ovale, and bicuspid valve (mitral valve)
Heart chambers: Left Ventricle
- Similar internal structures but more tortuous, larger papillary muscles compared to the right ventricle
- Trabeculae carneae, papillary muscles, chordae tendineae, interventricular septum (muscular and membranous parts), aortic vestibule, semilunar valve (aortic valve).
Heart chambers: great vessels (Blank copy)
- Diagram of the heart showing the great vessels, no description.
Heart Structure: Heart valves
- Complex framework of dense collagen forms fibrous rings between atria and great vessels.
- Acts as strut for valve cusp attachment and prevents over-distention.
- Includes atrioventricular rings, bicuspid/mitral valves, tricuspid valves, aortic ring, and pulmonary ring.
Structure: Cardiac skeleton
- Dense collagen framework forming four fibrous rings.
- Located in between the atria and the onward great vessels of the heart.
- Acts as the strut for the attachment of the cusps of the valves.
- Keeps the orifices patent and prevents over-distention
- Includes 2 atrioventricular rings.
- Includes bicuspid (mitral) valve, tricuspid valve
- Includes aortic ring and pulmonary ring
Structure: Cardiac skeleton
- Forms electrical insulator separating the atrial and ventricular muscles.
- Dense connective tissue acts as partitions for separate electrical impulses in atria and ventricles.
- Includes fibrous coronet of pulmonary valve, left fibrous trigone, right fibrous trigone.
Valves: Atrioventricular (AV) valves
- The two AV valves (tricuspid and bicuspid/mitral valves) open and close in response to pressure changes within the heart.
- Opens during atrial contraction to let blood into the ventricles.
- Close during ventricular contraction to prevent backflow into atria.
- Chordae tendineae and papillary muscles prevent valve prolapse during ventricular contraction.
Valves: Semi-lunar valves
- Two semi-lunar valves (pulmonary and aortic valves) responsible for blood flow out of the heart.
- Open as ventricles contract, letting blood into vessels.
- Close as ventricles relax, preventing backflow into ventricles.
Valves: Semi-lunar valves
- Pulmonary valve separates right ventricle and pulmonary trunk
- Aortic valve separates left ventricle and ascending aorta.
- Semi-lunar valves have 3 cusps shaped like crescent moons.
- Aortic valves have openings to the right and left coronary arteries.
Valves: Semi-lunar valves
- Open when ventricles contract, sending blood.
- Pressure causes valves to open.
- Pressure lessens, valves close.
- Closure created the second heart sound ("DUB").
- Prevent backflow into the ventricles
Heart Valves: Review
- Summary of AV and semi-lunar valve function and timing during cardiac cycle.
Heart Valves
- Structures (pulmonary trunk, ascending aorta, left/right atrium, left/right ventricle, superior vena cava, aortic valve, tricuspid valve, mitral valve) diagrammed and shown.
Valves: Abnormalities
- Stenosis: Narrowing of valves (don't open properly)
- Regurgitation/Insufficiency: Valves don't close properly.
- Can cause heart murmurs
Valves: Auscultation
- Murmurs can be heard for valve abnormalities.
- Murmurs can radiate to different locations, depending on vessel direction and heart position.
Heart Structure: Heart Histology
- Study of microscopic anatomy and tissue structure of the heart.
Heart Wall: Layers
- The heart wall comprises the epicardium (outermost), myocardium (middle - thickest layer), and endocardium (innermost).
- Epicardium: Composed of visceral pericardium, adipose tissue, and connective tissue.
- Myocardium: Composed of myocardial cells, a thick layer of cardiac muscle responsible for heart contraction.
- Endocardium: Composed of smooth endothelial tissue that lines the chambers and major vessels.
Histology: Epicardium
- Serous membrane layer of visceral pericardium (outermost)
- Sub-epicardial layer of loose connective, adipose, and elastic tissue around blood vessels.
- Adipose tissue, supporting coronary vessels (important for bypass grafting).
Heart Wall: Epicardial Fat
- Epicardial fat lies between the visceral pericardium and the myocardium.
- Protects, supports, and provides insulation for the heart and its electrical activity.
- More abundant in grooves (atrioventricular and interventricular grooves).
- Associated with factors like age, obesity, diabetes, and more common in females.
Histology: Myocardium
- Myocardium is composed of specialized striated muscle fibers (myocytes)
- Myocytes are branched and interconnected by intercalated disks.
- Myocardium thickness varies between chambers (left thicker than right).
- Myocardial cells are highly vascularized.
Histology: Myocardium
- Myocardium is composed of cardiac muscle cells.
- The amount of myocardium varies between the cardiac chambers according to load required
- Atria are smaller than the right ventricle, left ventricle is larger than the right.
Histology: Myocardium
- Outer surface is smooth, inner surface with trabeculation
- Protrudes into chambers to form papillary muscles (attachment for chordae tendineae).
Histology: Endocardium
- Innermost layer of the heart wall, in direct contact with blood.
- Three layers: endothelial, subendothelial, and layer interacting with myocardium.
- Endothelium (innermost) continuous with vessels.
- Contains collagen and elastic fibers.
- Thickness varies between atria and ventricles (atria thicker because of elastic fibers required for expansion)
Histology: Heart valves
- Heart valves originate from fibrous cardiac skeleton.
- Avascular connective tissue core (collagen and elastic fibers).
- Nutrients diffuse from blood in valve lumen.
- Endocardium covers leaflet/cusps.
- Thickness of valves can vary (AV thicker than semi-lunar valves), left-sided thicker than right-sided valves).
Part 3: Heart vessels
- Coronary circulation is the blood supply to the heart muscle.
Heart Vessels: Coronary Circulation
- Right and left coronary arteries branch off the aorta.
- Coronary arteries travel in coronary sulcus and interventricular sulci toward the apex of the heart.
Circulation: Overview
- The heart's blood supply is from the coronary circulation.
- First branches of the aorta, arising from the right and left aortic sinus.
- Coronary arteries loop around the heart (coronary sulcus) and extend down into the interventricular sulci
- Cardiac veins drain blood from the heart and empty into the coronary sinus.
Circulation: Right Coronary Artery
- Descends vertically in the coronary sulcus (between right atrium and ventricle).
- Branches to the SA node, right marginal artery, right nodal, posterior interventricular artery, anastomosis.
Circulation: Left Coronary Artery
- Enters the coronary sulcus and branches into the anterior interventricular (LAD) and circumflex arteries
- Anterior interventricular (LAD) travels toward the apex.
- Circumflex artery curves around the heart to the posterior interventricular artery branch
- Supplies left atrium, the left ventricle, part of the interventricular septum
Circulation: Coronary dominance & variation
- Coronary dominance refers to major variations in the coronary artery distribution originating from variations in the posterior interventricular artery (PDA).
- Typical: RCA.
- Left: LCA
- Co-dominance: Both, equally.
Coronary circulation: SA & AV node supply
- SA node commonly supplied by right coronary artery(60%); AV node by the right coronary artery (90%).
- Variations in blood supply to the SA and AV node
Coronary circulation: Imaging
- Arteriography/angiography is used to image the coronary arteries.
- Involves inserting a thin tube into an artery and injecting a contrast dye to image the vessels.
Circulation: Venous return
- Coronary sinus is primary drainage.
- Cardiac veins drain into the coronary sinus.
- Anterior cardiac veins drain directly into the right atrium.
Coronary circulation: Review
- Diagram showing a hierarchical summary of the coronary circulation.
Coronary circulation: Distribution
- Diagram showing the distribution of coronary arteries to the different heart chambers
- Right coronary artery, left circumflex artery, left anterior descending artery
Coronary circulation: Clinical correlates
- Coronary artery bypass graft (CABG)
- Procedures, such as grafting, are employed to re-establish blood flow
- Angiogenesis: New blood vessels may grow, aided by factors that promote growth.
Part 4: Conduction
- Heart innervation and conduction pathways
Heart Conduction
- Heart is involuntary, typically 70 beats per minute
- Rate can change with external factors like the nervous system, or hormones
- Sets of rhythmic contractions begin at SA node, into multiple pathways
Overview: Conduction system
- Heart contracts involuntarily with average rate 70 bpm.
- Higher in heart transplant patients (100 bpm)
- Conduction pathway (SA node and heart muscle) controls rhythmic heart contractions.
- Also regulated by the autonomic nervous system and hormones.
Overview: Conduction system
- Begins at the SA node, located in the right atrium near SVC
- Internodal branches carry impulses to AV node.
- Branches from SA node and others stimulate right and left atrium at same time.
- AV node sends impulses into interventricular septum as Bundle of His to stimulate ventricle contraction.
- Collection of nerves in interventricular septum
Conduction: Cardiac cycle
- Cardiac cycle includes atrial systole (contraction), and ventricular diastole (relaxation) and ventricular systole (contraction),
- Cycle begins with atrial systole and ends with ventricular diastole
- Systole (contraction phase) and diastole (relax phase) stages of cycle
Conduction: Cardiac cycle
- Shows steps of atrial and ventricular systoles and diastoles stages, and EKG representation
Innervation of Heart
- Innervation of the heart is from the autonomic nervous system consisting of sympathetic and parasympathetic branches.
Heart: Innervation Overview
- Heart innervation from parasympathetic (vagus nerve) and sympathetic nervous systems
- Parasympathetic: Slows heart rate
- Sympathetic: Increases heart rate (with pre- and post-synaptic fibers)
- Visceral afferent: Travel with sympathetic fibers, transmit noxious stimuli (referred pain).
Heart: Innervation Overview
- Diagram showing the paths of sympathetic, parasympathetic nerve fibers, and ganglia.
Heart: Sympathetic innervation
- Spinal cord levels T1-T4 become cervical cardiac & thoracic cardiac splanchnic nerves.
- Part of the cardiac plexus.
- Branches to SA and AV nodes and to the myocardium.
- Releases norepinephrine/noradrenaline
Heart: Parasympathetic innervation
- Vagus nerve branches to cardiac plexus.
- Branches to the SA and AV nodes.
- Other branches directly to myocardium.
- Releases acetylcholine
Heart: Innervation overview
- Diagram showing vagus nerve, cervical, thoracic branches, and SA and AV node innervation.
Heart: Referred pain
- Visceral sensory neurons enter the spinal cord at the same segmental level as supplying (dermatome)
- Referred pain occurs because the brain cannot distinguish between sensory input from visceral sensory neurons.
- Skin innervation is linked to the area of spinal cord segments T1-T4
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Description
This quiz explores various aspects of heart anatomy and physiology, including the functions of the myocardium, the roles of coronary vessels, and the structure of heart layers. It also addresses the significance of epicardial fat and endothelial health for overall heart function. Test your knowledge on the intricate components that contribute to cardiovascular health.
