posterior to sternum, medial to lungs, anterior to vertebral column, base lies beneath 2nd rib, apex @ 5th intercostal space, just above the diaphragm.
How many liters of blood does the heart pump each day?
How many times in an average lifetime does the heart contract
sends oxygen-depleted (deoxygenated) blood to the lungs to pick up oxygen and unload carbon dioxide
sends oxygen-rich (oxygenated) blood and nutrients to all body cells and removes wasts.
Where would you listen to hear the apical hearbeat?
by listening to the chest wall beween the fifth and sixth ribs about 7.5 cm to left of the midline
pericardium (pericardial sac)
covering that encloses the heart and the proximal ends of the lg blood vessels to which it attaches.
outer fibrous bag of pericardium, surrounds double-layered serous membrane. Tough protective sac largely complosed of dense connective tissue. Attached to the central portion of the diaphragm, the posterior of the sternum, the vertebral column and the lag blood vessels emerging from the heart.
visceral pericardium (epicardium)
innermost layer of serous membrane, covers the heart
where the visceral pericardium turns back upon itself and forms the inner lining of the fibrous pericardium.
between the parietal and visceral layers of the pericardium, contains a small volume of serous fluid that pericardial membranes secrete.
What is the function of the fluid in the pericardial cavity?
reduces friction between the pericardial membranes as the heart moves within them.
what are the 3 layers of the wall of the heart
epicardium, myocardium and endocardium
epicardium (visceral pericardium)
-outer layer of wall of heart
-protects heart by reducing friction.
-secretes ferous fluid
-serous membrane of connective tissue covered with epithelium and including blood capillaries, lymph capillaries and nerve fibers.
-middle layer of heart wall
-contracts to pump blood from the heart chambers
-cardiac muscle tissue separated by connective tissues and including blood capillaries, lymph capillaries and nerve fibers.
-inner layer of heart wall
-forms a protective inner lining of the chambers and valves
-membrane of epithelium and underlying connective tissue, including blood vessels and specialized muscle fibers (Purkinje fibers)
four chambers of the heart
-receives blood from the inferiorvena cava, superior vena cava, and coronary sinus
-right upper chamber of heart
-receives blood from the right atrium
-pumps blood to lungs
-right lower chamber of heart
-left upper chamber of heart
-receives blood from the pulmonary veins
-receives blood from left atrium
-pumps blood to the body
-lower left chamber of heart
-largest chamber of heart
earlike projections extending anteriorly from the atria, slightly increasing atrial volume.
separates right from left atrium
separates two ventricles
-opening where the atrium on each side communicates with its corresponding ventricle
-guarded by atrioventricular (AV) valve
name the orifices between the upper and the lower chambers of the heart
four valves of the heart
-tricuspid and mitral
-pulmonary (pulmonic) and aortc
which blood vessels carry blood into the right atrium
superior and inferior vena cava and coronary sinus
Where does blood go after it leaves the right ventricle
through pulmonary valve to pulmonary trunk to left and right pulmonary arteries
which blood vessels carry blood into the left atrium
four pulmonary veins - 2 from right lung and 2 from left lung
What prevents blood from flowing back into the ventricles when they relax?
-the blood backing up in the pulmonary trunk closing the pulmonary valve, preventing a return flow into right ventricle
-the aortic valve closes and prevents blood from backing up into the left ventricle when the left ventricle realxes.
-strong fibrous strings attaching to av valves
-small mounds of cardiac muscle tissue
-contract when the ventricles contract, pulling on the chordae tendineae and prevent the cusps from opening back into the atriums
-located right av orifice
-functions to prevent blood from backflowing from right ventricle into righ arium during venricular contraction
-location - entrance to pulmonary trunk from right ventricle
- functions to prevent blood from moving from pulmonary trunk into righ ventricle during ventricular relaxation
location - left av orifice
functions to prevent blood from moving from left ventricle into left atrium during ventricular contraction
location-entrance to aorta from left ventricle
functions to prevent blood from moving from aorta into left ventricle during ventricular relaxation
-carry blood away from heart
-usually oxygenated except when carrying blood from right ventricle to lungs (pulmonary arteries)
-carry blood toward heart
-usually deoxygenated, except when bring blood from lungs to left atrium (pulmonary veins)
Path of blood through heart
systemic circuit - superior and inferior vena cava - right atrium - tricuspid valve - right ventricle - pulmonary valve - pulmonary trunk - pulmonary arteries (right and left) - lungs - alveolar capillaries (gas exchange) - pulmonary veins - left atrium - mitral (bicuspid) valve - left ventricle - aortic valve - aorta - systemic circuit.
What structures make up the skeleton of the heart?
The fibrous rings surrounding the pulmonary trunk and the aorta, together with other masses of dense connective tissue in the portion of the septum between the ventricles.
How does blood composition differ in the right and left ventricle?
-right ventricle has blood low in oxygen and high in carbon dioxide
-left ventricle has blood high in oxygen and low in carbon dioxide
Which vessels supply blood to the myocardium
right and left coronary arteries.
How does the blood return from the cardiac tissues to the right atrium
Through the coronary veins that empty into the coronary sinus
state of contraction of the cardiac cycle
state of relaxation of the cardiac cycle
when ventricles relax
when ventricles contrace
the events required to complete a single heartbeat (contractions of both atria and both ventricles.)
atrial systole and ventricular diastole
-blood flows passively into the ventricles
-remaining 30% of blood is pushed into the ventricle
-AV valves open and semilunar valves close
-causes increase in ventricular pressure
ventricular systole and atrial diastole
-av valves close
-chordae tendinae prevent the cusps of the valves from bulging too far into the atria
-blood flows into atria
-ventricular pressure increases and opens semilunar valves
-blood flows into pulmonary trunk and aorta
first heart sound "lubb"
-occurs during ventricular systole
-closing of av valves
second heart sound "dubb"
-occurs during ventricular diastole
-pulmonary and aortic semilunar valves are closing
abnormal heart sound from the cusps not completely closing
What is functional syncytium?
a mass of merging cells that act as a unit
Where are the functional syncytia of the heart?
in the arial walls (atrial syncytium) and the ventricle walls (ventricular syncytium)
cardiac conduction system
system of specialized cardiac muscle fibers that conduct cardiac impluses from the SAnode into the myocardium.
SA (sinoatrial) node
-small elongated mass of specialized cardiac muscle tissue just beneath the epicardium
-in the wall of the right atrium near the opening of the superior vena cava
-fibers are continuous with those of the atrial syncytium
-pacemaker of the heart because it generates the heart's rhythmic contractions.
-initiates each cardiac cycle by generating an electical impulse that spreads over the atria causing it to contract
a compact mass of pace setting cells
Atrioventricular (AV) node
-mass of specialized cardiac muscle tissue in the inferior portion of the interatrial septum and just beneath the endocardium.
-relay signals to the ventricles.
AV bundles (Bundle of His)
-conducting fibers that extend down the interventricular septum sending branches right and left
-divides into the right and left bundle branches that lie just beneath the endocardium
-spread from the interventricular septum into the papillary muscles an then continue downward to the apex of the heart
-carry impulse to distant regions of the ventricular mycardium
-faster than cell-to-cell conduction
-transmit the impulse to the apex of the heart first so contraction begins at the apex and pushes the blood superiorly toward the aortic and pulmonary semilunar valves.
Cardiac Conduction System
SA node - atrial synctium - junctional fibers - av node - av bundle (bundle of his) - bundle branches - purkinje fibers - ventricular syncytium
-clumps of specialized cardiac muscle tissue which initiate and distribute impulses throughout the myocardium
-coordinates the events of the cardiac cycle
-a recording of the electrical changes in the myocardium during a cardiac cycle.
- because body fluids can conduct electrical currents, such changes can be detected on the suface of the body.
-represent the wave of depolarizaion that spreads from the SA node throughout the atria
-repolarization of ventricle muscle to resting state.
-arise from neurons in the medulla oblongata and secrete acetycholine when they reach the effector ends of the SA and AV nodes
secrete norepinephrine and increase and strengthen the contraction of the heart
Additional factors that may influence heart rate
-concentration of various ions including potassium and calcium
-parasympathetic impulses - decrease heart action
-sympathetic impulses - increase heart action
-cardiac center regulates autonomic impulses to the heart
-organs of the cardiovascular system
-form closed circuit to and from the heart
-include: arteries, arterioles, capillaries, venules, and veins
-Thick strong wall (three layers or tunics)
-middle layer of smooth muscle and elastic tissue
-outer layer of connective tissue
-carries blood under relatively high pressure
-thinner wall than an artery (three layers or tunics
-middle and outer layers are thinned
-some smooth muscle tissue
-small amount of connective tissue
-helps control blood flow into a capillary
-smallest diameter blood vessels
-very thin walls - extension of the inner lining of arterioles
-connnect the smallest arteriole and the smallest venule
-ealls are endothelium only
-microscopic vessels that continue from the capillaries and merge to form veins
-thinner walls than arterioles
-less smooth muscle and elastic tissue than arteriole
-thinner walls than arteries (three layers of tunics)
-middle wall poorly developed
-many have flap-like valves
-carry blood under relatively low pressure
-function as blood reservoirs
the force the blood exerts against the inner walls of the blood vessels
arterial blood pressure
-rises when the ventricles contract
-falls when the ventricles relax
the maximum pressure during ventricular contraction