Lecture 1 CVS: the heart Flashcards
what is the approximate size and wieght of the heart
around the size of a fist, and less than one pound
what is the location of the heart
-within the mediastinum, between the 2nd and 5th intercostal spaces
-superior surface of the diaphragm
-2/3s tilted towards the left midsternal line
-anterior to vertebral column; posterior to the sternum
what are the contents of the mediastinum
great vessels (aorta, pulmonary trunk, SVC, & IVC), thymus, esophagus, and trachea
how much does the heart pump and beat each day
-beats ~100,000 times each day
-pumps ~8000L of blood /day
what are the base and apex of the heart
Base (superior portion)- posterior to the sternum; connection of great vessels
Apex (inferior tip)- pointed tip
what does the heart sit between
sits between two pleural cavities in mediastinum
where do you find the apical pulse
palpated betweeen 5th and 6th ribs, just at the tip
what is the pericardium of the heart
membranous sac covering the heart
what does the pericardium consist of
1) superficial Fibrous Pericardium: protects and anchors the heart, and prevents overfilling
2) Deep Two-layered Serous Pericardium:
-Outer Parietal Layer: lines internal surface of fibrous pericardium
-Inner Visceral Layer: epicardium- on external surface of the heart
what does the pericardial cavity do
it is fluid filled and decreases friction
what are the three layers of the heart
Epicardium, Myocardium, and Endocardium
what is the epicardium
visceral layer of serous pericardium (outermost); covers surface of the heart
what is the myocardium
middle layer, thick layer of cardiac muscle cells and connective tissue, electrical signals flow within cells
what is the endocardium
the innermost layer, continuous with endothelium of blood vessels, simple squamous epithelium and areolar tissue
what are the chambers of the heart
right atrium (RA), right ventricle (RV), left atrium (LA), and left ventricle (LV)
what does the right atrium do
receives blood from the SVC (superior vena cava) and the IVC (inferior vena cava) with is the systemic circuit, & the coronary sinus (which supplies heart tissues themselves with blood and nutrients)
what does the right ventricle do
receives blood from RA; pumps to lungs through pulmonary trunk (pulmonary circuit)
what does the left atrium do
receives blood from lungs through pulmonary veins
what does the left ventricle do
receives blood from LA; pumps blood through aortic valve into systemic circuit
what are sulci in the heart
grooves containing fat and blood vessels
what is the coronary sulcus
marks border between atria and ventricles
what is the anterior interventricular/posterior interventricular sulci
mark boundary between left and right ventricles
difference between atria and auricles
the atria are the two upper chambers of the heart while the auricles are muscular pouches extending from the atria
what is a septa
muscular partitions separating heart chambers
what is the interatrial septum
separates the atria
what is the interventricular septum
separates ventricles; much thicker than interatrial septum
what do the heart valves do
ensure unidirectional blood flow through heart, and open & close in response to pressure changes
what are the two major types of valves in the heart
the atrioventricular valves (AV) and the semilunar valves
what do the atrioventricular valves do
-they are between the atria and ventricles; tricuspid (righht side) and mitral valves/bicuspid valves (left side)
-permit bloodflow from: RA to RV and from LA to LV
what do the semilunar valves do
-they are between ventricles and major arteries
-each consists of three cusps that roughly resemble a half moon
-prevent backflow of blood into the ventricles
where is the pulmonary semilunar valve and what does it do
-between trhe right ventricle and pulmonary trunk
-prevents backflow of blood from the pulmonary trunk into the right ventrical
where is the aortic semilunar valve and what does it do
-between the left ventricle and aorta
-prevents backflow of blood from the aorta into the left ventricle
what is the operation of the atrioventricular valves when blood is coming into ventricles
1) blood returning to heart fills atria, presseing against AV valves, the increased pressure causes AV valves to open
2) as ventricles fill, AV valve flaps handlimply into ventricles
3) atria contract, forcing additional blood into ventricles
what is the operation of the atrioventricular valves when blood is then in the ventricles
1) the ventricles contract, forcing blood against AV valve cusps
2) AV valves close
3) papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria
what are the operations of semilunar valves
1) as ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them to open
2) as ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close
what is the fibrous (cardiac) skeleton of the heart
-four dense bands of tough elastic tissue
-encircle valves and bases of great vessels
what are the functions of the fibrous (cardiac) skeleton of the heart
-stabilise valves and ventricular muscle cells (cardiomyocytes)
-physically support cardiac muscle fibers, blood vessels, and nerves of myocardium
-electrically insulate ventricular cells from atrial cells
-distribute forces of contraction
-add strength and prevent overexpansion of heart
-provide elasticity to return heart to original size and shape after contraction
what are the chordae tendineae
they connect cusps of valve papillary muscles of ventricles, and hold the valve in place
what do papillary muscles do
- they attach to the cusps of the atrioventricular valves
- they prevent inversion or prolapse of these valves on systole (or ventricular contraction)
what are the pectinate muscles and their function
- they are prominent muscular ridges
- they are on the anterior atrial wall and nner surface of auricle
- they increase the power of contraction without increasing heart mass substantially
what is the foramen ovale
connects the two atria of fetal heart
-before birth, it is an opening through the interatrial septum
-closes at birth, eventually forming fossa ovalis
what is atrial septal defect
it is a hole in the interatrial septum (foramen ovale did not close at brith) causes blood to go straight from RA to LA
what is trabeculae carneae
they are muscular ridges on internal surface of both ventricles
what do trabeculae carneae do
they hold valves to prevent inversion into the atria (holds papillary muscles)
what is the moderator band
-a muscular ridge at the apex of the RV; connects interventricular septum to papillary muscles
-delivers stimulus for contraction to papillary muscles
-ONLY IN RV
what is the conus arteriosus
a cone-shaped pouch
- at the superior end of the right ventricle
- the pulmonary trunk emerges from this
what is the ligamentum arteriosum
it attaches the pulmonary trunk to the aortic arch
what is the similarity between the left and right ventricles
they both hold and pump the same amount of blood
what are the differences between the left and right ventricles
- RV is thin-walled becasue it develops less pressure
- RV is more pouch-shaped than round
- LV has no moderator band
- LV is much larger and more muscular, and thicker-walled, due to higher pressures and it has to pump long distances throughout the body whereas the RV only pumps to the lungs
what is coronary circulation
- functional blood supply to the heart muscle itself, the shortest circulation in the body
- delivered when heart is relaxed
- left ventricle receives most of coronary blood supply
what are the arterial anastomoses
- interconnection of anterior and posterior interventricular arteries (vessels)
- they maintain constant blood supply to cardiac muscles
how many coronary arteries are there and what do they do (look at diagram on slide 21)
there are two, the left and right coronary arteries
they supply the cardiac muscles in the heart with oxygenated blood
how many coronary veins are there and what do they do (look at diagram on slide 21)
there are two, the anterior cardiac vein and the coronary sinus
what is the coronary sinus
it is a coronary vein and many cardiac veins merge into this
pathway of blood flow through the heart (check slide 22)
- SVC & IVC
- RA
- RV
- Pulmonary Trunk
- Lungs
- Four Pulmonary Veins
- LA
- LV
- Aorta
- Body
describe the cardiac muscle tissue/ cells
striated, short, branched, fat, interconnected-> they have intercalated discs (only in cardiac)
what types of junctions are in cardiac muscle tissues
-desmosomes: hold fibers together
-gap junctions: permits AP transmission, permits contraction to occur in myocardium at same time
cardiac muscle vs. skeletal muscle (nucleus, mitochondria, triads, & arrangement)
- they are mostly uninucleated, but occasionally binucleated
- the mitochondria are much larger and more abundant than skeletal muscles (need for more energy)
- there are no triads; SR (storage for Ca2+) is simpler than skeletal muscles
- the arrangement of contractile protein is same as skeletal muscles
skeletal vs. cardiac (gap junctions)
- skeletal: no gap junctions between cells
- cardiac: there arer gap junctions between cells
skeletal vs. cardiac (contracts as a unit)
- skeletal: no, motor units must be stimulated individually
- cardiac: yes, gap junctions create a functional syncytium
skeletal vs. cardiac (T-tubules)
- skeletal: abundant
- cardiac: fewer, wider
skeletal vs. cardiac (source of Ca2+ for contraction)
- skeletal: sacroplasmic reticulum only
- cardiac: sacroplasmic reticulum and extracellular fluid
skeletal vs. cardiac (Ca2+ binds to troponin)
yes for both
skeletal vs. cardiac (pacemaker cells)
- skeletal: no
- cardiac: yes
skeletal vs. cardiac (tetanus possible)
- skeletal: yes
- cardiac: no
skeletal vs. cardiac (supply of ATP)
- skeletal: Aerobic and anaerobic (fewer mitochondria)
- cardiac: aerobic only (more mitochondria)
what are the two types of myocytes in the cardiac conduction system
- contractile cells
- pacemaker cells
what do the contractile cells do
responsible for contraction
what are pacemaker cells and what are they responsible for
-non-contractile cells that spontaneously depolarize
-initiate depolarization of the heart
-repeatedly generate spontaneous APs
-trigger contraction of atria and ventricles
-they are self-excitable, without neutral or hormonal stimulation-> autorhythmicity
what are the compnents of thew cardiac conduction system
- sinoatrial node (SA)
- atrioventricular node (AV)
- AV bundle (Bundle of His)
- bundle branches
- purkinje fibers
what are the steps in the cardiac conduction system
- the (SA) sinoatrial node (natural pacemaker) generates impulse
- the impluses pause (0.1s) at the atrioventricular (AV) node
- the atrioventricular (AV) buncle connects the atria to the ventricles
- the bundle branches conduct the impulses through the interventricular septum
- the subendocardial conducting network depolarizes the contractile cells of both ventricles
action potential of pacemaker cells (why?)
pacemaker cells have unstable resting membrane potentials called pacemaker potentials or prepotentials
what are the three parts of the action potential of the pacemaker cells
- pacemaker potential: this slow depolarization is due to both opening of Na+ channels and closing of K+ channels. notice that the membrane potential is never a flat line
- depolarization: the action potential begins when the pacemaker potential reaches threshold. depolarization is due to Ca2+ influx through Ca2+ channels
- repolarization: is due to Ca2+ channels inactivating and K+ channels opening. this allows K+ efflux, which brings the membrane potential back to its most negative voltage
what are the cardiac contractile cells
-form the bulk of atrial and ventricular walls, responsible for pumping
-receive stimulus from purkinje fibers
-RMP (resting membrane potential): ventricular cells is ~-90mV; atrial cell is ~-80mV
-presence of plateau phase
what are the steps in action potential of contractile cardiac cells
- depolarization: is due to Na+ influx through fast voltage-gated Na+ channels. a positive feedback cycle rapidly opens many Na+ channels, reversing the membrane potential. channel inactivation ands this phase
- plateau phase: is due to Ca2+ influx through slow Ca2+ channels. this keeps the cell depolarized because most K+ channels are closed
- repolarization: is due to Ca2+ channels inactivating and K+ channels opening. this allows K+ efflux, which brings the membrane potential back to its resting voltage
what is pericarditis
due to pathogens in the pericardium
- inflamed pericardial surfaces rub against each other
-produces a distinctive scratching sound
what is cardiac tamponade
excess fluid that leaks into pericardial space; compress heart’s pumping ability
what is valvular heart disease (VHD), incompetent valve, and valvular stenosis
the deterioration of valve function
-may develop after carditis (inflammation of heart); -may result from rheumatic fever (inflammatory autoimmune response to streptococcal bacteria)
-incompetent valve: blood backflows so heart repumps same blood voer and over again
-valvular stenosis: stiff flaps that constrict opening, heart needs exert more force to pump blood
what is coronary artery disease (CAD)
areas of partial or complete blockage of coronary circulation; due to formation of a fatty deposit (atherosclerosis) in coronary vessel walls
what is coronary ischemia
-cardiac muscle cells need a constant supply of oxygen and nutrients
-reduction in blood flow to heart muscle reduces cardiac performance
what is a myocardial infarction (MI)
-a heart attack
-part of coronary circulation becomes blocked= coronary thrombosis
-cardiac muscle cells die from lack of oxygen
-death of affected tissue creates a nonfunctional area known as an infract
-most commonly results from severe CAD
