Anatomy of the Heart and Coronary Vessels Flashcards
What is the pericardium?
3-layered sac around the heart
What is the fibrous pericardium and what is its function?
Protective layer
Attached to great vessels (aorta, pulmonary artery and veins)
Attached to diaphragm
Anchors heart in place
What is the serous pericardium and what is its function?
Parietal attached to fibrous layer
Visceral attached to surface of heart (epicardium)
What is the function of the pericardium?
Fixes heart in mediastinum and limits movement
Protection from infections coming from other organs (such as lungs)
Prevents excessive dilation of heart in cases of acute volume overload
Lubrication – allows free movement of heart within pericardial sac
What is pericardial effusion, what can it lead to and how is this managed?
Fibrous pericardium normally restricts overexpansion, but if fluid gathers between parietal and visceral pericardium the heart has nowhere to go
This leads to cardiac tamponade
Managed by pericardiocentesis - indicated by a pericardial effusion causing tamponade (RV free wall collapse during diastole)
What happens when fluid accumulates under high pressure?
Compresses cardiac chambers and impairs diastolic filling of BOTH ventricles
Hypotension/shock, reflex tachycardia (down SV and CO)
JVP (systemic)
Rales (pulmonary congestion)
What is the mechanism of right ventricle collapse?
Rate of accumulation and amount of fluid in pericardium and the compliance of the pericardium all affect the severity of the symptoms.
Increased volume of fluid in the pericardia sac compresses the atria, vena cava and pulmonary veins. This causes right ventricle collapse.
Reduced right ventricle filling in diastole decreases stroke volume and decreases cardiac output leading to cardiac arrest.
Right ventricle affected before left because of it does not have a thick muscular wall.
What are the 3 layers of the heart wall?
Epicardium o Visceral layer of serous pericardium Myocardium o Cardiac muscle fibres -> Arranged in bundles and squeezes blood out of heart Endocardium o Continuous with endothelium o Lines chambers and valves
What are the external landmarks of the heart and where are they located?
Coronary groove (atrioventricular sulcus) o Between the atria and ventricles Anterior interventricular sulcus o Between right and left ventricles Posterior interventricular sulcus o Between right and left ventricles
What are the features of the right atrium and ventricle?
Right border and anterior surface SVC, IVC and coronary sinus Smooth walled posteriorly, rough anteriorly Fossa ovalis Tricuspid valve o Valve cusps o Chordae tendineae o Papillary muscles Trabeculae carnae o Trabeculae – pole-like, rod-like Pulmonary trunk o Pulmonary semilunar valve
What are the internal landmarks of the right atrium?
SVC IVC Fossa Ovalis Coronary sinus Tricuspid valve Pectinate muscle Cristae terminalis
What are the internal landmarks of the right ventricle?
Pulmonary trunk Pulmonary valve Septal papillary muscle Moderator band Anterior/posterior papillary muscles Trabeculae carnae Chordae tendinae Anterior/posterior septal Tricuspid
What are the features of the left atrium and ventricle?
Posterior or base of heart 4 pulmonary veins Smooth walls excluding pectinate muscle in left auricle Fossa ovalis Mitral valve o Chordae tendineae o Papillary muscles Trabeculae carnae Thicker myocardium Ascending aorta
What are the features of the coronary blood supply?
Arterial supply
o Coronary arteries (right and left)
Supply both the atria and ventricles
What are features of the coronary arteries?
RCA anastomoses with circumflex branch of LCA
o After RCA has given rise to Post interventricular artery
LAD loops around apex and anastomoses with Post interventricular artery
Dominance
o Determined by the arteries that supply the posterior and inferior wall of left ventricle
o Approximately 60% of general population are right-dominant, 25% are co-dominant, and 15% are left-dominant
The left coronary artery (LCA) initially branches to yield the left anterior descending (LAD), also called the anterior interventricular artery. The LCA also gives off the left marginal artery (LMA) and the left circumflex artery.
In ~20-25% of individuals, the left circumflex artery contributes to the posterior interventricular artery (posterior descending PDA).
The right coronary artery (RCA) one of the first branches goes to the right atria and SA node. Branches to form the right marginal artery (RMA) anteriorly. In 80-85% of individuals, it also branches into the posterior interventricular artery (PDA) posteriorly.
What is the clinical anatomy of the coronary arteries?
Myocardial infarction
o LAD off LCA 40-50%
o RCA 30-40%
o Circumflex of LCA 15-20%
May damage conducting system
o LAD to septal branches supplying AV node
o RCA supplies both SA and AV nodes -> Heart block
What are features of the coronary veins?
Venous drainage from cardiac muscle
Drains into coronary sinus on posterior surface of heart
Coronary sinus empties into right atrium
What is the fibrous skeleton of the heart and what is its function?
Dense connective tissue surrounds AV and outflow vessel valves
Fuse together and merge with interventricular septum
o Support the valves
o Prevents overstretching of the valves
o Insertion point of cardiac muscle bundles
o Electrical insulator between atria and ventricles
What happens to the atrioventricular (bi/tricuspid) valves in diastole?
A-V valves open and allow blood to flow from atria into ventricles when ventricular pressure is lower than atrial pressure
Occurs when ventricles are relaxed, chordae tendinae are slack and papillary muscles are relaxed
What happens to the atrioventricular (bi/tricuspid) valves in systole?
o A-V valves close preventing backflow of blood into atria
Occurs when ventricles contract, pushing valve cusps closed, chordae tendinae are pulled taut and papillary muscles contract to pull cords and prevent cusps from everting
What are the features of the semilunar valves?
Three cusps Prevent backflow from aorta & pulmonary trunk into ventricles Passive action Systole of ventricles opens valves Diastole of ventricles o Decrease in BP o Backflow fills cusps and closes valve
What are the features of the heart conducting system?
Cardiac muscle fibers form 2 networks via gap junctions at intercalated discs
o Atrial network
o Ventricular network
Separated by a fibrous skeleton
What nerve provides innervation to the heart, where is this nerve and what other nervues does it contain?
Heart is supplied by the cardiac plexus
Lies anterior to the bifurcation of the trachea and posterior to the arch of the aorta
Cardiac plexus contains:
o Parasympathetic (from vagus)
o Sympathetic (from sympathetic trunk)
o Visceral sensory afferents (VGA)
Fibres extend from the plexus to the coronary vasculature and to components of the conducting system of the heart (especially SA node)
What are the effects of sympathetic innervation?
Increased heart rate
Increased force of contraction
Cardioacceleratory center
o Medullary reticular formation
Preganglionic sympathetic neurons in thoracic spinal cord
Postganglionic sympathetic neurons to SA & AV node and to coronary VSM
What are the effects of parasympathetic innervation?
Slows heart rate Pathway o Reticular formation in medulla -> Cardioinhibitory center o Vagus nerve (CN X) o To SA & AV nodes
What are some features of cardiac pain?
Pain not felt in heart – referred
Pain caused by ischaemia and damage to cardiac muscle
o Stimulates visceral sensory nerve endings in myocardium
o Visceral afferent nerve fibres ascend to the CNS through cardiac branches of the sympathetic trunk and into CNS
Organ and skin pain fibres travel to spinal cord together
Generally referred (interpreted) as if it came from somatic areas
Skin supplied by T1-5 L side of chest, neck and face and L. arm
o For infarct on inferior wall – referred -> To epigastrium (T7, 8 and 9)
