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Anatomy of Heart (CLINICAL BOX (heart) (Angina pectoris (Pain due to…
Anatomy of Heart
CLINICAL BOX (heart)
Cardiac catheterization
use of radiopaque contrast to view bloodflow
use of radiopqaue catheter record intracardiac pressure
can also use cardiac ultrasonography
embryology of right atrium
primordial atrium represented in adult by right auricle
definitive atrium enlarged by incorporation of most of embryonic sinus venosus
Before birth, blood is directed from the placenta to the ICV and towards the oval foramen into the left atrium
Oval foramen has a valve that allows for right to left flow
Upon birth and first breath, lungs expand and pressure in right atrium falls below left, closing the shunt
IVC valve thus has no function after birth
Septal defects
Atrial septal defects: incomplete closure of oval foramen
Small opening by themselves cause no hemodynamic abnormalities -> no clinical significance
clinical ASD vary widely in size and may occur as a part of a more complex congential heart disease
ASD could cause shunting of oxygen rich blood into the right atrium, cause enlargement of right RA and RV, and dilation of pulmonary trunk
Hypertrophy of right atrium and ventricle and pulmonary arteries
Ventricular Septal defects: usual defects in membranous part of IVS
VSD rank first in cardiac defects
Cause left to right shunt of blood, increase pulmonary blood flow, cause severe pulmonary disease (HBP) and may cause cardiac failure
Rare VSD in muscular part freq closes spontaneously during childhood
Percussion of heart
At 3rd, 4th and 5th intercostal spaces from left anterior axillary line to right anterior axillary line
normally, note changes from resonance to dullness (due to presence of heart) approx 6cm to the left of sternum
Stroke or cerebrovascular accident
thrombi form on walls of LA in certain heart disease
If thrombi detach or pieces break off, they pass into systemic circulation and occlude peripheral arteries
Occlusion of artery supplying the brain results in stroke or CVA, which may affect vision, cognition or motor function
Naming basis for aortic and pulmonary valves
Truncus arteriosus, common arterial trunk for both ventricles of the embryonic heart, has four cusps
Heart undergoes partial rotation so that apex is directed to the left (posterior cusp shifts slight right, anterior shifts slightly left)
Division of truncus valve during development cuts A and P cusps into half
Valvular Heart Disease
Stenosis
failure of valve to open fully (narrowing), slowing blood flow from a chamber
Pulmonary valve stenosis
cusps fused
infundibular : conus arteriosus underdeveloped
Restriction of flow, degree of hypertrophy of right ventricle is variable
Aortic valve stenosis
Most freq valve abnormality
result of degenerative calcification
Extra work of heart, LV hypertrophy
Insufficiency or regurgitation
Failure of valve to close completely, usually due to nodule formation on(or scarring and contraction of) the cusps so that edges do not meet or align
Mitral Valve Prolapse
Insufficient or incompetent valve with one or both leaflets enlarged, redundant or floppy, extends back to atrium during systole
Blood regurgitates back into left atrium
Chest pain and fatigue
Very common
Produce murmur
Pulmonary valve incompetence
Lunules of cusps of semilunar valve thicken, become inflexible or damaged by disease
Valve will not close completely
back rush of blood under high pressure into the right ventricle during diastole
heard as murmur
Aortic valve insufficiency
Heart murmur and a collapsing pulse
Aortic regurgitation
Both results in an increased workload for the heart
Both creates turbulent flow, sets up eddies that produce vibrations and are audible as murmurs
Superficial vibratory sensations may be felt on skin over an area of turbulence
Has different degrees, duration and etiology that could affect heart, BV and other organs,
May be congenital or acquired
May occur acutely or chronically(insufficiency) where as stenosis is essentially a chronic process
usually requires valve replacement (valvuloplasty)
Coronary artery disease or coronary heart disease
Myocardial infarction
Blood vessel infarcted, undergoes necrosis
three most common sites
anterior IV branch of LCA ( 40-50%)
RCA (30--40%)
Circumflex brunch of LCA (15-20%)
Coronoary artherosclerosis
Build up of lipid deposits in the intima
Originally collateral channels connecting coronary arteries expand to compensate
Still not enough blood supply for increased work, and heart attack may occur during strenuous exercise
Slow vs accute coronary artery disease
Angina pectoris
Pain due to ischemia of myocardium that falls short of necrosis
Decreased blood flow, less oxygen, increase anaerobic metabolism, more lactic acid accumulates, decrease pH
Pain receptors stimulation by lactic acid in muscles
normally relieved by period of rest or sublingual nitroglycerin (spray under toungue for absorption through oral mucosa) that dilates coronary arteries
Pain from MI more severe
Coronary bypass graft
Great saphenous vein often harvested as diameter is equal or greater than coronary artery, can be easily dissected from lower limb and offers lengthy portions with minimum occurence of valves or branching
Use of radial artery also becoming common
Shunts blood from aorta to a stenotic coronary artery to increase blood flow to part distal to blockage
Coronary angiolasty|
Use of balloon to open up bloackage
Coronary occlusion and conducting system of heart
Occlusion of blood supply to conducting system of heart, heart block may occur
Ventricles begin to contract independently (25-30x per minute) at a slower pace than normal while atria continue to contract at normal rate if SA node is not affected
impulse generated by SA node no longer reach ventricles
Damage to on of the bundle branches cause bundle branch block
Excitation pass along unaffected branch with normal cycle of ventricle only
Impulse then spread to other ventricle via myogenic conductionm producing a later asynchronous contraction
In most cases, cardiac pacemaker may be implanted to increase ventricular rate (subcutaneously)
Consist of pulse generator or battery pack, a wire and an electrode
electrode with catheter connected to it inserted into a vein and passed through SVC to the right atrium, to the right ventricle and fixed to the trabeculae carneae in the ventricular wall in contact with the endocardium
Restarting heart (during cardiac arrest)
Done through CPR to restore cardiac output and pulmonary ventilation
In surgery, use internal or open chest heart massage
Fibrillation of heart
multiple, rapid, circuitous contraction or twitch of cardiac muscle fibers
Atrial fibrillation
Twitching of atrial walls, ventricles respond at irregular intervals to disrhythmic impulses from the atria
Usually circulation remains satisfactory
Ventricular fibrillation
Irregular pattern of uncoordinated contractions
Most disorganized of all dysrhythmias
no effective cardiac output
Fatal if persists
Defibrillation of heart
Electric shock given to heart through thoracic wall via large electrodes (paddles)
Shock causes cesssation of all cardiac movements, and a few seconds later, heart may begin to beat more normally
re establishment of coordinated contraction may result in some degree of systemic (and coronary) circulation
CLINICAL BOX (mediastinum and pericardium)
Levels of viscera relative to mediastinal divisions
Becomes lower when we stand up due to gravity, and textbooks show anatomical layers when the subject is lying supine.
Mediastinoscopy and mediastinal biopsies
using a endoscope (mediastinoscope) to see much of the mediastinum and conduct minor surgery
Inserted through root of neck, just superior to jagular notch
Biopsy mediastinal lymph nodes
widening of mediastinum
Could be due to hemorrhage into mediastinum from lacerated great vessels, malignant lymphoma (enlargement of mediastinal lymph), hypertrophy of heart (congestive heart failure, where venous blood returns to heart > cardiac output)
Transverse pericardial sinus
finger can be passed through sinus after pericardial sac is opened anteriorly
Can use clamp or ligature around these large vessels, insert tubes of coronary bypass machine, stop and divert the circulation of blood while performing cardiac surgery (coronery artery bypass grafting)
Pericarditis, pericardial rub and pericardial effusion
Percarditis (inflammation of pericardium) cause chest pain and makes the serous pericardium rough
Friction of rough surface will make sound (usually smooth surface wont make sound) like rustle of silk when listening over left sternal border and upper ribs
Chronic inflammation and thickened pericardium may calcify, hampering cardiac efficiency
some inflammatory disease produce pericardial effusion (passage of fluid from pericardial capillaries into pericardial cavity or accumulation of pus)
Heart becomes compressed as a result, cant extend fully
Non inflammatory pericardial effusion often occur with congestive heart failure -> venous return > cardiac output --> right cardiac hypertension
Cardiac tamponade (heart compression)
Fibrous pericardium is tough, inelastic, closed sac that contains only the heart within it
Extensive pericardial effusion compromis volume of sac --> wont allow full expansion of heart and thus limit cardiac output
potentially lethal when heart vol is compromised by increase pericardial cavity|
Blood in pericial cavity (hemopericardium) also produce cardiac tamponade
may result from perforation of a weakened area of heart muscle due to previous myocardial infarc, bleeding into the cavity after cardiac opration or from stab wounds
Especially deadly as it accumulates rapidly
Veins of face and neck become engorged due to backup of blood
Pneumothorax (air in pleural cavity may dissect along CT planes and enter pericardial sac, producing pneumopericardium
Pericadriocentesis
Drainage of fluid to relieve cardiac tamponade
Needle inserted through the left 5th and 6th intercostal space near the sternum (exposed pericardial sac that is not covered by the lungs)
Positional abnormalities of heart
abnormal folding of embryonic heart tube to the left instead of right may cause reversal of sides (dextrocardia)
usually functions normally in situs inversus
isolated dextrocardia may be complicated by severe cardiac anomalies such as transposition of great arteries
Chambers of the Heart
Right Atrium
Receive: SVC, IVC and coronary sinus
right auricle is a conical muscular pouch, acts as add on room
Inferior right atrium:
smooth, thin-walled posterior part (sinus venarum) on which SVC and IVC and coronary sinus open, bring low 02 blood in.
Rough, muscular anterior wall of pectinate muscles
Right AV orifice
Smooth and rough separated by sulcus terminales externally, and crista terminales interior
Coronory sinus: receive most of cardiac veins, is between right AV orifice and IVC orifice
Interatrial septum has an oval fossa, remnant of the oval foramen (a valve in the fetus)
Right Ventricle
Largest anterior part of heart
Tapers superiorly into arterial cone, conus arteriosus, leading to pulmonary trunk
has irregular muscle elevations (trabeculae carneae), a thick muscular ridge (supraventricular crest) that separates rough and smooth (superior) layers
Inflow from right AV orifice
Tricuspid valve
base of valve cusps attached to fibrous ring
Cordinae Tendinae attached to free edges (ventricular surface) of the Anterior, posterior and septal cusps
extends to papillary muscles, which when contract, pulls the cusps together to close it (as it connects to two cusps)
Anterior papillary (biggest) to anterior and posterior cusps
Posterior to Posterior and septal
Septal and anterior and septal
Interventricular Septum is thick to withstand high pressure from the left ventricle
Membranous part of the IVS formed by fibrous skeleton of the heart (superior to the AV valve is the atrioventricular septum)
Septomarginal trabecula (moderater band) connects inferior part of IVS to base of anterior papillary muscle
Important: carries part of the right branch of AV bundle, facilitating conduction time, allow coordinated contraction of anterior papillary muscle
Blood flow
contract atrium, force into ventricle posteriorly
Ventricle contracts, leave superiorly to the left, blood takes a u shape turn (140 degrees)
supraventricular crest help direct flow
Left Atrium
Forms most of base
valveless pulmonary veins enter smooth walled atrium
Left auricle forms superior to atrium, overlaps root of pulmonary trunk
Semilunar depression in IA septum: floor of ovalfossa
Interior of atrium:
Large smooth walled part, and a smaller muscular auricle containing pectinate muscle
4 pulmonary veins entering smooth posterior wall
IA septum that slopes posteriorly and to the right
Left Ventricle
Apex of heart, nearly all of left surface and border and most of diaphragmatic surface
Arterial pressure much high in systematic than pulmonary circulation, myocardium layer is thicker and performs more work
Interior:
Mostly covered with trabeculae carneae that are finer andmore numerous than RV (more muscle)
Longer than RV conical cavity
Anterior and Posterior muscles that are larger than those in RV (mitral/bicuspid valve)
Smooth walled, non muscular superior anterior outflow part: aortic vestibule
Aortic orifice
Mitral valve located posterior to the sternum, attached cords become taught during systole, preventing cusps from being forced into LA.
Bloodflow: 180 degree change, reversal of flow occers anterior to mitral valve
Semilunar valves
Pulmonary valve (anterior, right and left)
Aortic Valve (Posterior, right and left)
Concave when viewed superiorly
No tendon cords, opening and closing is entirely based on flow, closes during diastole due to back flow of blood into concave region, causing the cusps to close
Edge of each cusp is thickened in the region of contact (form lunule) and the apex of the free edge is further thickened as the nodule
Aortic and pulmonary sinuses: space of origin of pulmonary trunk and ascending aorta, immediately superior to the cusps
Blood here prevents the cusps from sticking to the wall
Mouth of right coronary artery is at right aortic sinus (on wall, not on valve),and mouth of left coronary artery is on left aortic sinus
Pericardium
2 layers
Fibrous pericardium
Tough external layer
Continuous inferiorly with central tendon of diaphragm (percardiacophrenic ligament)
Continuous superiorly with tunica adventitia (perivascular CT) of great vessels and with petracheal layer of deep cervical fascia
attached anteriorly to posterior sternum by sternopericardial ligaments
bound posteriorly by loose CT to structure in posterior mediastinum
Serous Pericardium
Parietal (in contact with FP) and visceral (in contact with the heart)
Pericardial cavity in between these two layers
Contains a thin film of fluid that enable heart to move and beat in a frictionless environment
Mainly mesothelium, a single layer of flattened cells
Visceral SP forms the epicardium, continuous and joins with parietal where aorta and pulmonary trunk leave and where both vena cavas and pulmonary veins enter
Transverse pericardial sinus
Runs between the aorta + pulmonary arch and the SVC (includes the serous pericardium)
Oblique pericardial sinus
Between left pulmonary veins and the other veins
Covers the heart and the root of the great vessels
Arterial Supply
Pericardiocophrenic artery, pericardiocophrenic vein and the phrenic nerve runs together down to the diaphragm
"didnt note in smaller vasculatures"
Nerve supply
Phrenic nerves (C3-C5)
Runs along the pericardium between the lungs and the heart due to development of lungs cutting down the pleuropericardial membrane during fetal development (6 weeks)
Vagus nerves
Sympathetic trunks (vasomotor)
Heart
Three layers
Endocardium: thin internal layer (endothelium and subendothelial CT) or lining membrane of heart that also covers valves
Myocardium: thick, double helical middle layer of cardiac muscle
Starts with contraction of outer spiral, narrowing and shortening the heart, followed by contraction of inner spiral, elongating the heart, followed by relaxation (expansion) of heart
wringing motion due to double helical orientation of cardiac muscle
Epicardium: Thin external mesothelial layer (Visceral SP)
Skeleton of the heart
Dense collagen forming 4 fibrous rings that surround orifices of valves (tricuspid, mitral (bicuspid), aortic and pulmonary valve)
Keeps orifices of AV and semilunar valves patent and prevents over distention by an increase in blood volume
Provides attachments for leaflets and cusps of valves
Provides attachment for myocardium, which when uncoiled forms ventricular myocardial band that originates from fibrous ring of pulmonary valves into that of the aortic valve
Forms an electrical insulator to keep signals to the heart
Parts of the heart
Coronary Sulcus (AV groove) separates atrium from ventricle
Anterior and Posterior interventricular sulci separates right and left ventricles
Apex: left inferior tip of the heart, normally remains motionless during cardiac cyle, area where you can heart mitral valve closure
Base: posterior aspect, directly opposite of apex, extend superiorly to bifurcation of pulmonary trunk and inferiorly to coronary sulcus
Four surfaces
Anterior (sternocostal): mainly by RV
Diaphragmatic (inferior): mainly LV partly RV, relation to central tendon of diaphragm
Right pulmonary: mainly RA
Left pulmonary: mainly LV, forms cardiac impression on lung
Four borders
Right border: formed by RA and extend between S and IVC
Inferior (near horizontal): formaed mainly by RV and partly by LV
Left border: mainly by LV and slightly by left auricle
Superior border: formed by RA and LA and auricles in anterior view, SVC enters on right side
Vasculature of heart
Arterial supply
RCA
ascending SA nodal branch, supplies SA node (in approx 60% of people)
then descends in coronary sulcus and gives right marginal branch
Supply blood to right side of heart, and goes towards (but not to) the apex
Continue down coronary sulcus to the posterior, at the crux of heart (cross)
Gives AV nodal branch, which supplies to AV node (in 80%)
Run inferiorly at cross to give posterior IV branch that supplies for posterior one third
Supplies blood to both ventricle (part of LV) and sends perforating IV septal branches
LCA
SA nodal branch in 40%
Anterior IV branch: pass along IV groove to the apex, turns around the inferior border and commonly anastomoses with the posterior IV branch or RCA
Supplies to anterior 2/3 of the IV septum
also gives the lateral branch (diagonal) in many people
smaller circumflex of LCA follows coronary sulcus to the back
Breaks of the left marginal branch
Continues posteriorly but terminates on the coronary sulcus before the crux (commonly) though some (1/3) continue to supply a branch that runs in or adjacent to posterior IV groove
Variations
Most common right dominant pattern (67%), RCA and LCA share bloody supply of heart equally
a few has left circumflex go to posterior IV groove, few has only one coronory artery
Coronary collateral circulation
Usually, branches of coronary arteries considered functional end ateries
However, anastomoses from other large branches/ coronary branch maintain viability of tissue should occlusion occur
Venous drainage of heart
Main vein of heart: coronary sinus, runs from left to right in posterior part of coronary sulcus
Receives great cardiac vein in the left, middle cardiac vein and small cardiac veins on the righ tend
Great cardiac vein
Anterior IV vein starts at apex of heart, ascends with anterior IV branch of LCA
then turns left at coronary sulcus to reach coronary sinus
Drains areas of the heart supplied by LCA
Middle CV (posterior IV vein)
Small IV
Accompanies right marginal branch of RCA
Drain most areas supplied by RCA together with middle CV
Oblique vein of left atrium
Descends over posterior wall of left atrium, joins great CV to form coronary sinus
remnant of embryonic left SVC, occasionally persists in adults
Small anterior cardiac veins
Begin anterior surface of RV, cross over coronary sulcus, end directly in RA or sometimes end in small CV
smallest cardiac veins
More like capillaries, with capillary beds in myocardium and carry from blood chambers to the myocardium
Lymphatic drainage
Lymphatic vessels in myocardium and subendocardial CT pass to subepicardial lymphatic plexus
Pass to coronary sulces, follow coronary arteries
A single lymphatic vessel formed from union of many ascends between pulmonary trunk and LA and ends in inferior tracheobronchial lymphnodes
Stimulating, conducting and regulating systems of the heart
Sino-Atrial node (SA) located anterolaterally, just deep to epicardium at junction of SVC and right atrium.
Pace maker of the heart
signal from SA node spreads myogenically to both atria
stimulated by sympathetic division of autonomic nervous system, inhibited by parasympathetic division
Collection of nodal tissue, specialized cardiac muscle fibers and associated CT
AV node
Smaller collection of nodal tissue
located in posterior inferior region of IA septum near opening of coronary sinus.
Signals generated pass through wall of right atrium, propagated by cardiac muscle (myogenic conduction), transmit signal rapidly from SA to AV
AV then distributes signal to ventricles through AV bundle (passing through fibrous skeleton of the heart) along membranous part of IVS
At junction of membranous and muscular parts of IVS, AV bundle divides right and left, proceed on each sice of the muscular IVS and deep to the endocardium, and then ramify into subendocardial branches (purkinje fibres)
Innervation of the heart
Supplied by autonomic nerve fibres from cardiac plexus
Formed by branches of the vagus nerves and sympathetic trunks, visceral afferent fibers conveying reflexive and nociceptive fibers from the heart.
lying on anterior surface of bifurcation of trachea, posterior to ascending aorta and pulmonary trunk
Fiber extend from plexus along and to coronary vessels and to components of conducting system, especially SA node.
Sympathetic: increase heart rate, impulse conduction, force of contraction and at the same time, increase blood flow through coronary vessels to support increased activity
adrenergic stimulation of SA node and conducting tissues also increases rate of depolarization of pace maker cells while increasing AV conduction
Indirect suprarenal(adrenal) hormone stimulation increases atrial and ventricular contractility
Most adrenergic receptors on coronary blood vessels cause relaxation of the smooth muscle and thus, dilation (activation
Parasympathetic: slows heart rate, reduce force of contaction, constrict coronary arteries, saving energy between periods of increase demand
Fibers release acetylcholine, binds to muscarinic receptors to slow rates of depolarization of pacemaker cells and AV conduction and decrease atrial contractility
Mediastinum
Boundaries: laterally by pleural cavities, anteriorly by sternum and posteriorly by vertebral columns, inferiorly by diaphragm
Superior and inferior mediastinum cut by the transverse thoracic plane
Superior: Superior thoracic aperture to transverse thoracic plane that includes the sternal angle
Trachea, esophagus, thymus, phrenic nervies, azygous vein, SVC, brachiocephalic artery and veins, aortic arch, left common carotid artery, left subclavian artery (runs inferior to the carotid) and thoracic duct
Common pathology: aortic arch aneurysm
R L
Transvarse thoracic plane: Approx at IV disc of T4 and T5
Inferior: Transverse thoracic plane to diaphragm
Further subdivided by pericardium into anterior, middle and posterior mediastinum (middle is where the heart is)
Anterior: Thymus, lymph nodes
common pathology: thymona
Middle: Heart, pericardium, phrenic nerves, ascending aorta, SVC and coronary arteries and veins
Posterior: Descending aorta (after arch) esophagus, vagus nerves
