Pericardial cavity and heart Flashcards

right ventricle
Terms Definitions
Describe the parietal and viscera parts of serous pericardium
1) parietal - serous mesothelium (inner lining) of the pericardial cavity2)visceral - reflection of the mesothelial layer over the great vessels and surface fo the heart to form the outermost layer of the heart wall; formed by invagination of the pericardial cavity by the developing heart
Explain the source and significance of pericardial fluid
Pericardial fluid is secreted through the serous mesothelium. It keeps the surface layers of the heart moist and slippery-> frictionless beating of the heart within the pericardial cavity. It also develops surface tension between the pericardial layers. This results in slight expansion of the heart during inspiration -> greater bld return to the right side of the heart
Describe the pericardial sinuses
1)oblique sinus - pericardial cavity posterior to the heart. Formed by an arch of reflected parietal pericardium. Is equal to a mesentary, could be called the "cardiac ligament"2)transverse sinus - passage behind the ascending aorta and pulmonary trunk.
Clinical significance of the transverse sinus
During cardiac surgery, ligatures can be passed into the transverse sinus and around the aorta and pulmonary trunk to control hemorrhage or to secure cannulas placed in the great vessels
Explain the significance of pericardial tamponade. What is it? What are its consequences? What are its symptoms?
This is accumulation of fluid (blood or serous) in the pericardial sac. It compromises cardiac expansion -> reduced cardic output but increased heart rate (weak, rapid pulse), and increased venous pressure w/ jugular vein distension, pulsating liver, and edema
Describe the routes for pericardiocentesis and pros and cons of each approach
1)subcostal route - needle introduced via sternocostal angle; inserted on the left side adjacent to the xiphoid process at an upward 45° angle and to the left. pros; avoid pleural cavities, also avoid the anterior descending or right marginal branches of the coronary arteries2) Parasternal - needle introduced into the paricardial cavity through the left 4th or 5th intercostal space immediately adjacent to the sternum. Pros: cardiac notch in the pleura of the lung eliminates chance of inducing pneumothroax. Also avoid the internal thoraci artery if the edge of the sternum is found before plunging into the pericardial sac
Describe the location of the heart and diameter relative to the transverse diameter of the chest
The heart is located in the pericardial sac wiht 1/3 laying to the right and 2/3 laying to the left of the midline. Normally it measures 8-9 cm in diameter. The transverse diameter should not exceed more than 1/2 the diameter of the chest.
Describe the cardiac boundaries
1)Right (acute) border - superior vena cava, right atrium, inferior vena cava2) Inferior border - right ventricle3)Apex - tip of the left ventricle where the inferior and obtuse borders meet4) left (obtuse) border - delineates the right ventricle5) upper border, indistinct radiographically
What is PMI and where is it?
PMI is the point of maximal impulse (apical pulse) which is palpable and sometimes visible at the 5th intercostal space just beneath the nipple
Location/contents of coronary sulcus
Completely encircles the heart and separates the atria from the ventricles Is the location of the annulus fibrosus.Contains the circumflex branch of the left coronary artery, right coronary artery, coronary sinus, and the small cardiac vein
Location/contents of the anterior interventricular sulcus
Runs diagonally along the sternocostal surface close to the left border of the heartSeparates the L/R venriclesContains the anterior interventricular artery (lateral anterior descending ) and the great cardiac vein
Location/contents of the posterior interventricular sulcus
Continuation of the anterior interventricular sulcus around the apex, onto the diaphragmatic surface of the heartContains the posterior interventricular artery and the middle cardiac vein.
Describe the origin, course, branches (5) of the right coronary artery
1) Origin: originates from the right aortic sinus2) Course: runs right within the coronary sulcus, passes beneath the right auriular appendage, and aroudn the right cardiac margin to the posterior aspect of the heart3)Branches: SA nodal branch, right marginal branch, posterior interventricular (descending) branch, atrioventricular nodal artery, terminal branches
Describe the distribution of the right coronary artery
In ~85% of the population, it supplies the right atrium (inc. SA node), superior aspect of the right ventricle, and the posterior 1/3 of the interventricular septum (inc AV node, and right branch of the AV bundle)
Describe the origin, course, branches of the left coronary artery
1)Origin - originates from the left aortic sinus2)Course - runs between the pulmonary trunk and the left auricular appendage before splitting into the LAD and the circumflex artery3) Branches - LAD (left anterior descending) branch (-> diagonal branches, septal branches), circumflex artery (left marginal artery), posterior descending artery in 10-15% of the population, artery of Kugal in 39% of the population (->SA nodal artery)
Discuss the principal variations in cornary circulation
1) Balanced - 60-65%; right coronary artery gives off the posterior descending branch2) Left preponderant - 10-15%; Circumflex branch of the l. coronary artery gives rise to the posterior descening branch. AV node is supplied also. 3) Right preponderant - 20-25% R. coronary artery supplies the posterior descending branch and crosses the posterior interventricular septum to reach the left marginal artery. In this case, the circumflex artery is diminutive
Explain the concept of coronary arteries as end-arteries
These arteries supply discrete volumes of the myocardium. With slow-onset coronary occlusion anastomoses can develop. This is why young people tend to not survive heart attacks when older people do.
Explain the concept of "low margin of safety" for coronary perfusion
This refers to the fact that coronary arteries can only supply the heart with blood during diastole or 50% of the time. Therefore there is a low amount of tolerable perfusion loss before a restriction in blood supply occurs
Describe the course of the coronary sinus
It receives venous supply from the heart, wraps around the heart posteriorly in the coronary sulcus, and dumps into the right atrium between the inferior vena cava and the right AV valve
List the coronary sinus branches
Great cardiac veinMiddle cardiac veinSmall cardiac vein (end=right marginal vein)Olbique vein of Marshall
Describe the anterior cardiac veins
1+ small veins that drain the anterior surface of the right ventricle.They open separately into the right atrium
Describe the distribution of the left coronary artery
in general it supplies the left atrium, the inferior portions of the right ventricle, apex, and the superior portions of the left ventricle. In 10-15% of the population, posterior septum and AV node are supplied by it.
Define epicardium
Epicadium is the visceral layer of the serous pericardium plus fatty tissue
Discuss myocardial organization
The myocardium is composed of 3 layers of cardiac muscle, each originating from the annulus fibrosus. The layers spiral perpendicualarly to each other to produce a wringing motion during systole. The fibers do not cross the coronary sulcus. In the atria, and ventricles, myocardial fibers convey electrical impulses. In the ventricles specialized cells do this as well
Locate the sinoatrial node
It lies between the crista terminalis and the superior vena cava in the right atrium
Discuss S-A node function
The SA node initiates atrial systole and acts as the pacemaker of the heart. It paces the AV node
Locate the atrioventricular node
The AV node is located in the right atrial floor near the interatrial septum and above the septal cusp of the tricuspid valve.
Discuss AV node function
The AV node initiates ventricular systole. It is paced by the SA node
Describe the atrioventricular bundle. Discuss AV bundle funcion
The Av bundle of HIs runs along the anterior ventricular septum through the annulus fibrosis before splitting into right (r. ventricle) and left (l ventricle) bundles. It transmits electrical activity throughout the ventricles
Define endocardium
Endocardium is the inner lining of the cardiac chambers. It is a thin, smooth endothelial layer continuous w/ the endothelium of the great vessels
Describe annulus fibrosus
this is a layer of dense CT arranged in the AV plane that creates the coronary sulcusIt serves as the "skeleton" of the heart by being the site of insertion for myocardium
Discuss annulus fibrosus function
It surrounds and supports each valvular opening and electrically isolates the atria from the ventricles. Only the AV bundle of HIS passes through it
Compare right atrial wall thickness to other chambers
It has the thinnest walls of all the heart chambers
Describe the location and structural characteristics of the sinus venarum of right atrium
The sinus venarum lies to the right of the crista terminalis. It is smooth-walled and receives numerous veins
Lis the veins emptying into the right atrial chamber
Superior vena cavaInferior vena cava (eustachian valve)cardiac sinus (thesbian valve)cardia anterior veins
Discuss the structural chracterisitcs of the right atrium proper
This is the anterior muscular portion of the atrium on the left side of the crista terminalis -> pectinate muscles.Contains the right auricular appendage, the atrial septal wall, and the right AV/tricuspid valve.
Describe the characteristics of the atrial septal wall
The atrial septal wall separates the right and left atria.It contains the fossa ovalis (derived from the foramen ovale). Is the site of atrial septal defect (ASD) when the fossa ovalis is not closed all the way. Effects 10% of the population
Know the most common atrial septal defect
Septum secundum defects; accounts for 10-15% of all cardiac anaomolies.Because the pressure in the left side of the heart is greater than that of the right, it is not a big deal, (left to right shunt), but if blood flows between the atria from right to left, deoxygenated blood can get into the systemic circulation ->cyanosis
Explain possible consequences of atrial septal defect
Because the pressure in the left side of the heart is greater than that of the right, it is not a big deal, (left to right shunt), but if blood flows between the atria from right to left, deoxygenated blood can get into the systemic circulation ->cyanosis
Contrast the right venticular myocardium with the right atrium
Right ventricle muscular walls are thicker than the right atrium. Also hass trabeculae carneae muscles instead of pectinate muscles
Describe the characteristics of the right ventricle proper
Has rough, muscular walls with trabeculae carneae and papillary muscles.Contains the right AV valveContains the interventricular septum
Discuss the structure and function of the right atrioventricular valve and the role of papillary muscles
The AV vlave transmits blood from the r. atrium to the right ventricle. During ventricular systole, the papillary muscles tense up to prevent eversion of the cusps.It is composed of 3 cusps (anterior, posterior, septal) attached to papillary muscles via chordae tnedinae (CT).The papillary muscles shorten during the isotonic phase of ventricular systle to maintain teh competence of valve closure
Explain possible consequences of the ventricular septal defect
1) incosequential left to right shunt2) if pulmonary stenosis is present, will produce a left to right, then right to left shunt resulting in cyanosis or "blue-baby" syndrome
Describe the charactersitics fo the infundibulum of hte right ventricle
Smooth-walled outflow region that leads into the pulmonary orificeIt contains the pulmonary valve
Discuss the structure and function of the pulmonary valve
This valve consists of 3 cusps (right, left, posterior), attached peripherally to the annulus fibrosus. The free edges face upwards into the pulmonary trunkIt prevents backflow during ventricular diastole from the pulmonary trunk back into the right ventricle
Comment on the thickness of the left atrial wall
Thin walled, yet still thicker than the r. atrium because it needs to overcome resistance given by the much thicker left ventricle
Describe the vein entering the left atrium and comment on possible variation
Left and right pulmonary veins enter the left atrium from the lungs. Usually there are two veins to each side, but sometimes three can come from the right or one from the left
Explain why the fossa ovalis appears as a depressed dimple in the interatrial septum of both the right and left atria
During development, blood is shunted from right to left to avoid the lungs. A leaflet is here to help wiht this. Upon birth, the pressure in the left side of the heart becomes greater than that of the right which leads to the shutting of this strucutre (-> dimping on the left)
Discuss and explain left ventricular wall thickness
This chamber has the most muscular (thickest) walls in order to fight against systemic resistance of the entire body
Describe the structure of the left atrioventricular valve
2 cusps (anteror, posterior), with chordae tendinae and papillary muscles. It has more chordae tendineae than the tricuspid valve. Its cusps are also supported by the annulus fibrosis
Discuss the function of the left atrioventricular valve and the role of the papillary muscles
The left atrioventricular valve prevents regurgitation of blood into the left atrium during ventricular systole. During isovolumic (pressure build up), the papillary muscles tense to prevent eversion of the cusps. During isotonic systole, the shortening of themuscles picks up slack from the chordae tendinae in order to keep the valve closed
Explain mitral insufficiency
When the mitral valve doesn't close properly. This is heard as a low-pitched, late systolic blowing murmur. Mitral stenosis is heard as a late diastolic murmur
Describe the structure of the aortic valve
The aortic valve has three cusps (left, right, posterior) that are supported by the annulus fibrosus. The leaflets point upwards into the ascending aorta. Behind each leaflet are the aortic sinuses. These small depressions are the origin of the coronary arteries.
Explain the function of the aortic valve
the aortic valve prevents regurgitation from the aorta into the l. ventricle during diastole.
Describe the aortic sinuses and origins of the coronary arteries
Behind each leaflet are the aortic sinuses. These small depressions are the origin of the coronary arteries.
Explan the role of the aorta in maintaining diastolic pressure
The elastic properites of the aorta accommodate ejcted blod volume and maintain the range of diastolic arterial presure. The stored energy of the elastic stretch maintains a prolonged diastolic arterial pressure (drops slowly rather than precipitously)
Describe the composition of the cardiac conducting system
Specialized cardiac muscle cells are responsible: Sa node, Av node, AV bundle of His, right and left bundles
Understand the function of the SA node
The SA node initiates contraction. The depolarization it causes spreads throught the right and left atria muscles in 0.09 seconds.
Discuss teh location, blood supply and innervation of the SA node
SA node is found in the right atrium between the superior vena cava and the cristae terminalis. It is supplied with blood via the SA nodal branch of the right coronary artery. Occasionally this branch is supplied by the left coronary artery (artery of Kougal).It is influenced mainly by the parasympathetic division of the ANS to slow its autorhythmicity.
Understand the function of the AV node
The AV node synchronizes ventricular depolarization. It conducts at a lower velocity than the SA node which allows the atria to contract fully before the ventricles are stimulated.
Discuss the location, blood supply and innervation of the AV node
The AV node is found in the right atrial floor near the interatrial septum, medial to the coronary sinus, and above the septal cusp of the tricuspid valve.It is supplied by the AV nodal branch of the right coronary artery (occasionally by the left coronary artery)IT is innervated by ? (left vagus nerve)
Discuss the location and branches of the AV bundle
The AV bundle arises from the Av node passes through the annulus fibrosus and descnds along the membranous part of the interventricular septum to enter the muscular part. It branches into left and right bundle branches (crurua) which spread out into the walls of the ventricles
Discuss the AV bundle function
Conducts electrical activity to the ventricles. It consists of Purkinje fiberes which hve a rapid conduction rate
Discuss heart block
Heart block occurs when a pathologic condition interrupts impulse propagation in teh AV bundle. It results in the asynchronous beating of the atria and ventricles. If the depolarization is inititated outside of the nodal system, the individual muscle fibers may contract -> no blood pumped
Generalize motor control to the heart
Heart rate and ejection volume are controlled by the ANS (sympathetic/parasympthetic)
Describe the parasympathetic pathways to the heart
Long, myelinated pre-ganglionic fibers from the brain stem leave the vagus nerves and recurrent laryngeal branches and pass through the cardiac plexus to reach the heart. They synapse with small, unmyelinated postganglionic fibers in the myocardium.
Discuss parasympathetic function
ACh is the neurotransmitter for both the synpase and the neuromuscular junction. It slows down the heart rate and reduces the stroke volume
Describe the sympathetic cervical pathways to the heart
Presynaptic fibers originate in the T1-T2 spinal levels, then travel up the cervical chain to the cervical ganglia. They then leave the cervical sympathetic chain as the superior, middle, and inferir cervical splanchnic (cardiac accelerator) nerves and progress inferiorly in the neck to the small ganglia of Wrisberg in the cardiac plexus. This is where the synapse occurs.
Describe sympathetic function
Norepinephrine or Epinephrine is the neurotransmitter used. it accelerates the heart rate and increases the stroke volume
Describe the afferent pain pathways from the heart
The afferent pain pathways run retrograde up the sympathetic pathways. They must enter the spinal cord through white rami. 1) Cervical pathway - fibers course along the middle and inferior cervical splanchnic nerves to the middle/lower cervical ganglia of the symp. chain. They then descend to the whtie rami communicantes fo the T1-T2 symp. ganglia.2)Thoracic pathways - afferent fibers pass along the thoracic splanchnic nervs directy to ganglia T1-T4 of the symp. chain and travel along the white ramus communicantes for each the spinal cord at those levels.
Discuss the patterns of referred pain of cardiac origin
Pain signals from the heart originate from coronary artery insufficiency. It is perceived as coming from the arm ,shoulder or precordium because of the pathways that visceral afferent fibers take.
Describe the sympathetic thoracic pathways to the heart
Presynaptic fibers originate at levels T1-T4, to the symp. ganglia via white ramus communicantes, pass through becoming thoracic splanchnic nerves and continue to small ganglia in the cardiac plexs where the synapse occurs. The post synaptic neuros then course through the cardiac plexus to the heart
Know the duration and list the phases of the cardiac cycle
Total length of cardiac cycle is .8 secondsAtrial systole, Atrial diastole, Ventricular systole, ventricular diastole
Know the duration of atrial systole
Discuss the role of atrial systole
pumps a small amount of blood (the last bit) into the ventricles to stretch the ventricle walls, placing teh heart muscle at the optimal point of the length-tension curve
Describe the two phases of ventricular systole
Isometric: the AV valves and the semilunar valves are closed. Ejection phase (isotonic contraction): the semilunar vlaves open when the ventricular pressure>pulmonary and aortic diastolic pressure.
Explain the cause and significance of the S1 valve sound
"Lub"The S1 sound is the sound of the AV valves closing. It marks the beginning of the isometric phase of ventricular systole
Know the duration of ventricular diastole
occupies slightly more than half the cardiac cycle. Lasts for ~.5sec.
Explain the cause and signifcance of the S2 valve sound
"Dub" The S2 sound is the sound of the semilunar valves closing. It marks the beginning of Ventricular diastole. Occurs when pulmonary and aortic pressure exceed the end-systolic ventricular pressures
Know normal cardiac ejection volume and pulse rate
Ejection volume = 60-70ml/beat or 5L/minute. Pulse rate = 80 beats/min.
Describe the source of diastolic pressure
Diastolic pressure is a function of heart rate. The slower the rate, the lower the aortic diastolic pressure falls before the subsequent heart beat.
Know normal pulse rate
80 beats/minute
Describe cardiac valve locations
The 4 cardiac heart valves like in the plane of the annulus fibrosus
Know the auscultation area for each cardiac valve
Tricuspid valve - to the right of the sternum around the 5th intercostal space.Mitral valve - at the apex of the heart (PMI), around the 5th intercostal space.Pulmonary valve - to the left of the sternum around the 2nd intercostal space.Aortic valve - to the right of the sternum around the 2nd intercostal space; Also in the neck over the carotid artery
Be able to generalize (from pressure differentials) systolic murmurs and diastolic murmurs with specific valve dysfunction
Atrioventricular insufficiency - During systole, sounds like a low-pitched, rushing murmur.Atrioventricular stenosis - can be heard during diastole as a low murmur before the first heart sound.Semilunar insufficiency - associated with diastolic mumur Semilunar stenosis - produces a high-pitched, musical systolic murmur
Discuss the role of the foramen ovale in fetal circulation
The foramen ovale shuts oxygenated blood from teh umbilical vein from the right atrium into the left atrium to bypass the deflated lungs.
Discuss the role of the ductus arteriousus in fetal circulation
The ductus arteriousus shunts deoxygenated blood from the pulmonary trunk, via the right ventricle, into the descending aorta.
Explain the foramen ovale closure
1) Functional closure - produced by reversal of interatrial pressure; When the lungs inflate postnatally, the pressure in the left side of the heart is greater than that of the right. Pulmonary vascular resistance drops->valve of the foramen ovale closing2) Anatomic closure - results from constant apposition of the valve leaflet with the septumFossa ovalis
Explain the postnatal closure of the ductus venosus
undergoes fibrosis to form the ligamentum venosus
Discuss patent ductus arteriousus
1) Initial closure - results by temprorary muscular contraction mediated by a substance released from the lung, bradykin.2) Complete anatomic obliteration - takes 1-3 monthsLigamentum arteriosum
Discuss atrial vs. ventricular septal defects
VSD is much more serious than ASD. ASD is only a problem is something occurs to create a right to left shunt.
Describe the tetrology of Fallot
1) VSD creates interventricular communication - blood flow between the ventricles2) Right ventricular hypertrophy occurs as the right ventricle enlarges its musculature to accomodate the additional pressure coming from the left ventricle 3) Functional pulmonary stenosis - a result of hypertrophy of the supraventricular crest. During systole the crest blocks the pulmonary outflow track which leads to a right to left shunt4) the opening of the aorta overrides the VSD into the right ventricle ->even more deoxy blood going to systemic circulation
Explain the sequelae of septal defects
Right to left shunt sends deoxygenated blood throughout the body causing an increase in cardiac work in order to provide the same amount of oxygen to the body tissueCardiac decompensation and failure can ensue.
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