Anatomy & Physiology Chapter 20 The Heart

the pump in the cardiovascular system that distributes blood for all functions and to all tissues in the body
the study of the heart and the diseases associated with it
Heat Beats
100,000 times per day, 35 million times a year
Heart Volume
5 liters/min or 5.3 quarts, 14,000 liters a day, or 3,600 gallons
Heart Size
Man’s fist: 5 in long, 3.5 in wide, 2.5 in thick
Heart Mass
8 oz. or 250 grams (female), 10 oz. or 300 grams (male)
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Heart is located in
the mediastinum
Heart apex
is formed by the left ventricle and rests on the diaphragm
Heart Base
formed by the atria (mostly the left) and is the posterior surface
the membrane that surrounds and protects the heart
Fibrous Pericardium
tough connective tissue; prevents overstretching, protects and anchors the heart
Serous Pericardium
thin delicate membrane that forms a double layer around the heart; parietal and visceral
Parietal layer
outer layer fused to the fibrous pericardium
Visceral layer
inner layer; adheres tightly to heart surface; also called the epicardium
Pericardial cavity
space between the parietal and visceral layers containing pericardial fluid
Pericardial fluid
serous fluid; lubricates the heart and prevents friction as the heart moves
3 layers of the heart wall
epicardium, myocardium, endocardium
the visceral layer; thin transparent outer layer of the heart wall
cardiac muscle tissue; 95% of heart mass and responsible for pump action
striated, involuntary muscle that swirls diagonally around the heart in bundles
inner (within); thin layer of endothelium overlying a thin layer of connective tissue
endothelium provides a smooth lining for chambers and valves of the heart
often linked to a viral infection
caused by: viral infection, rheumatic fever, or exposure to chemicals or radiation
typically affects the heart valves; usually bacterially caused: treated with antibiotics
the superior, receiving chambers of the heart
pouch-like structure on the anterior surface of each atrium to increase atrial capacity
the inferior, pumping chambers of the heart`
grooves on the heart surface that mark external boundaries between chambers
Types of Sulci:
coronary sulcus, anterior interventricular sulcus, posterior interventricular sulcus
Coronary sulcus
external boundary between superior atria and inferior ventricles
Anterior interventricular sulcus
anterior groove between right and left ventricles
Posterior interventricular sulcus
posterior groove between right and left ventricles
Right Atrium
forms the right border of the heart and receives blood from veins of the body and heart
Blood enters the atrium through 3 mains veins:
superior vena cava, inferior vena cava, & coronary sinus
Pectinate muscles
muscular ridges in the anterior portion of the right atrium that extend into the auricle
Interatrial septum
thin partition between right and left atrium
Fossa Ovalis
remnant of the foramen ovale of the fetal heart; an opening through the interatrial septum that closes after birth
Tricuspid Valve
“right antrioventricular valve”; 3 cusps; blood passes through this valve from the right atrium to the right ventricle
Tricuspid structure
dense connective tissue overlain with endocardium
Right Ventricle
forms much of the anterior surface of the heart; pumps the blood to the lungs from the heart through pulmonary arteries
Trabeculae Carneae
ridges formed by raised bundles of cardiac muscle fibers
Papillary muscles
cone-shaped trabeculae carneae which anchor the chordae tendinae (tendon-like cords) to the cusps of the tricuspid valve
Interventricular Septum
muscular partition between the right and left ventricle
Blow flow from the right ventricle
Right ventricle contracts and squeezes(pumps) blood out through the *pulmonary semilunar valve* into the *pulmonary trunk* which divides into *right and left pulmonary arteries* which take blood to the lungs
Left Atrium
receives blood from the lungs through the 4 pulmonary veins
Pectinate muscles of the left atrium
are only present in the auricle not the atrium itself
Bicuspid valve
left atrioventricular valve; blood passes from the left atrium into the left ventricle; also called the mitral valve
Left Ventricle
the thickest chamber of the heart averaging 10-15mm, & forms the apex of the heart
Blood flow of the left ventricle
Blood is pumped through the *aortic semilunar valve* into the *ascending aorta*; from there blood flows into the *coronary arteries to the heart wall* and the remainder passes into the *aortic arch* or *descending aorta*
Ductus arteriosis
opening during fetal life that shunts blood from the pulmonary trunk into the aorta, so only small amounts of blood flow to the non-functioning lungs
Ductus arteriosis
closes after birth and forms the ligamentum arteriosum which connects the aortic arch to the pulmonary trunk
Ventricle walls
are thicker than atrial walls
Right ventricle pumps
an equal amount of blood as the left ventricle but over shorter distances and with less resistance to blood flow
Left ventricle lumen shape
Right ventricle lumen shape
crescent sliver
Fibrous skeleton of the heart:
four dense connective tissue rings that surround the valves of the heart, fuse with one another, and join at the interventricular septum
Fibrous skeleton functions
forms foundation for the heart valves; prevents valves from overstrectching; point of insertion for cardiac fibers; and electrical insulators between atria and ventricles
respond to pressure changes by opening to allow flow or closing to prevent backflow
Blood circulation is
dependent on the pumps and valves
Cardiac Cycle
a complete heartbeat consisting of systole and diastole of both atria and both ventricles
Atrioventricular valves
tricuspid & bicuspid
Atrium contracts whil
ventricles, papillary muscles, and chordae tendonae are relaxed
AV valves are held closed by
contracted papillary muscles and tendonae chordae
Semilunar valves
aortic valve & pulmonary valve; contain 3 moon-shaped cusps
narrowing of the heart valve opening restricting blood flow
or incompetence; the failure of a valve to close completely
Mitral stenosis
narrowing of the mitral valve; caused by scar formation or congenital effects
Mitral insufficiency
backflow of blood from the left ventricle back into the left atrium
Mitral valve prolapse (MVP)
one or both cusps of the mitral valve protrude into the right atrium during right ventricle contraction; most common valvular disorders; affects 30% of population and more frequent in women
Aortic stenosis
narrowing of the aortic valve
Aortic insufficency
backflow of blood from the aorta to the left ventricle
Rheumatic fever
acute systemic inflammatory disease; brought on by streptococcal infection of the throat
Systemic Circulation
route; *oxygenated blood* flows from left ventricle through the aorta to all the body and *deoxygenated blood* returns to the right atrium
Pulmonary Circulation
route; *deoxygenated blood* flows from right ventricle through the pulmonary trunk and arteries to the lungs and *oxygenated blood* returns to the left atrium
Right side of heart
pulmonary circulation
Left side of heart
systemic circulation
Conary/Cardiac Circulation
network of blood vessels supplying the myocardium of the heart through coronary arteries
Coronary arteries
branch off the ascending aorta and encircle the heart like a crown; supply blood to the heart myocardium
2 coronary arteries
the left and right
Left coronary artery branches
anterior interventricular branch & the cirumflex branch
Anterior interventricular branch
in anterior interventricular sulcus; supplies both ventricles
Circumflex branch
runs through coronary sulcus; supplies left side (left atrium and left ventricle)
Right coronary artery branches
atrial branches, posterior interventricular branch, marginal branch
Atrial branches
supply right atrium
Posterior interventricular branch
in posterior sulcus; supllies both ventricles
Marginal branch
in coronary sulcus; supplies the right ventricle
Route for supplying the heart
Arteries-> arterioles-> capillaries
Coronary sinus
where deoxygenated blood drains after supplying the heart and empties into the right atrium
Veins that carry deoxygenated blood to the coronary sinus
great cardiac vein, middle cardiac vein, small cardiac vein, & the anterior cardiac veins
Great cardiac vein carries blood
from areas supplied by the left coronary artery including the left atrium and both ventricles
Middle cardiac vein carries blood
from areas supplied by the posterior branch of the right coronary artery including both ventricles
Small cardiac vein
lies in the coronary sulcus; drains the right atrium and right ventricle
Anterior cardiac vein
drains right ventricle; opens directly into the right atrium
connections between arteries that provide alternate routes for blood in case the main route becomes obstructed
Collateral circuits
the name for the alternate routes anastomoses provide to reach organs or tissues
Myocardial ischemia
condition of reduced blood flow to the myocardium due to partial obstruction of blood flow in the coronary arteries; silent myocardial ischemia is deadly
reduced oxygen supply to tissues and cells which does not kill them; can be caused by ischemia
Angina pectoris
“strangled chest”, pain that accompanies myocardial ischemia; may often manifest in the neck, chin, and left arm to elbow
reestablishment of blood flow to tissue in hypoxia, with the result of possible further damage caused by free radicals in the reintroduced oxygen
Myocardial Infarction
a heart attack; complete obstruction of blood flow in a coronary artery
death of an area of tissue because of interrupted blood supply= dead
Treatment for myocardial infarction
clot-dissolving agents, coronary angioplasty, coronary artery bypass grafting
Cardiac Muscle Tissue
tissue of the heart wall composed of branched striated fibers; one or two centrally located nulcei; contain intercalated disc
Intercalated discs
found only in cardiac muscle; irregular transverse thickening of the plasma membrane that connect ends of neighboring muscle fibers
Intercalated discs contain
desmosomes and gap junctions
“glue” that holds the muscle fibers together during rigorous contractions of the heart; spot-weld-like junctions between cardiac muscle cells
Gap junctions
gaps between calls that enable nerve impulses to spread instantly across the myocardium so that the atria or ventricles contract as a single coordinated unit
Cardiac muscle control
involuntary; not consciously controlly
Function of cardiac muscle
pump blood to all parts of the body
Autorhythmic fibers
a network of specialized cardiac muscle fibers that are self-excitable; generate action potentials that trigger heart contractions that will continue even after the heart has been removed from the body
Autorhythmic fibers
constitue about 1% of muscle fibers formed during development; act as a *pacemaker* setting the rhythm of electrical excitation that causes contraction of the heart
Autorhythmic fibers
form the conduction system; a network of specialized cardiac muscle fibers that provide a path for each cycle of cardiac excitation
Step 1 of the Conduction system
excitation begins at the *sinoatrial node* near the opening of the vena cava in the right atrium;
Step 1 of the Conduction system
the SA node repeatedly depolarizes and this depolarization is called the pacemaker potential; when pacemaker potential reaches threshold it triggers an action potential which propagates through gap junctions in both atria and the *atria contract*
Step 2 of the Conduction system
the same action potential from step 1 is conducted to the *atrioventricular node* in the interatrial septum
Step 3 of Conduction system
From the AV node, the action potential enters the *atrioventricular bundle “Bundle of His”*
Bundle of His
the only site where action potentials can conduct from the atria to the ventricles due to the insulation of the fibrous skeleton
Step 4 of Conduction system
action potential propagates along the AV bundle of his and enters the right and left branches down through the interventricular septum toward the apex
Step 5 of Conduction system
large diameter *Purkinje fibers* rapidly conduct the action potential throughout the *ventricular myocardium*; and the *ventricles contract* pushing blood toward the semilunar valves
Timing of the pacemaker can only be modified by
the autonomic nervous system & blood-born horones
The fundamental rhythm is established by
the sinoatrial (SA) node
Artificial pacemakers
used when the SA node becomes damaged or diseased to maintain normal heart rate
Contractile fibers
the working atrial and ventricular muscle fibers that are excited by the *sinoatrial node*
Contraction steps in order
rapid depolarization, plateau, and repolarization
Step 1 of contraction
rapid depolarization; contractile fibers are usually at resting potential- when contractile fibers are subjected to an electrochemical gradient, rapid depolarization is produced and the excitation spreads through the gap junctions and the contractile fibers *contract as a unit*
Step 2 of contraction
plateau; a period of maintained action potential in a contractile fiber; much longer than normal neuron periods being about 250 millisec; is the prolonging of contraction
Step 3 of contraction
repolarization; the recovery of the resting membrane potential, getting ready for the next contraction
Refractory period
period of time in muscle during which a second action potential cannot be triggered; is longer than the contraction
Cardiac muscle produces ATP
by aerobic cellular respiration
Cardiac muscle produces ATP
from creatine phosphate
Creatine Kinase presence indicates
injury of cardiac muscle usually caused by myocardial infarction (heart attack)
a composite record of the action potentials produced by all the heart muscle fibers during each heartbeat; recording can be detected at the surface of the body
During an electrocardogram 3 waves appear
P-wave, QRS complex, and the T-wave
small upward deflection on the EKG at *atrial depolarization* spreading from the *SA node*
QRS complex
*rapid ventricular depolarization* as action potentials spread through * ventricle contractile fibers*;
QRS complex
begins as a downward deflection, continues as a large upward triangular wave, and ends as a downward wave
dome shaped upward deflection that indicated *ventricular repolarization*
occurs just as the ventricles start to relax
Larger P-wave indicates
enlargement of atrium
Enlargement of Q-wave indicates
a myocardial infarction
Enlarged R-wave indicates
enlarged ventricles
Flat T-wave indicates
the heart muscle is receiving insufficient oxygen; sign of coronary artery (heart) disease
Elevated T-wave indicates
hyperkalemia (high potassium level in blood)
Time span between waves are called
intervals and segments
P-Q interval
time from beginning of P-wave to beginning of the QRS complex
P-Q interval
represents conduction time from beginning of atrial excitation to the beginning of ventricle excitation
Lengthened P-Q interval could indicate
coronary artery disease or rheumatic fever produced scar tissue that slowed the impulse
S-T segment
time of depolarization of the ventricular fibers; plateau phase
S-T segment elevated above basline
myocardial infarction
S-T segment depressed below baseline
insufficient oxygen
Q-T interval
time from beginning of ventricular depolarization to the end of ventricular repolarization
Lengthened Q-T interval indicates
myocardial infarction damage, ischemia, or conduction problems
Stress testing
looking for changes from the rest stage of the heart to times of exercise
Continuous ambulatory electrocardiograph
24 hour portable battery operated ECG which a patients wears
phase of contraction
phase of relaxation
ECG can predict
systole and diastole timing
Cardiac cycle
all the events associated with one heartbeat
Cardiac cycle includes
systole and diastole of both atria and both ventricles
A heart rate of 75 beats/min
will produce a cardiac cycle of 0.8 seconds
Step 1 Cardiac cycle
Atrial systole; duration 0.1 seconds
End-diastolic volume
volume of blood in the ventricle at the end of its diastolic period
During atrial systole
atrium contracts forcing 25 ml of blood through the AV valves into the relaxed ventricle
Step 2 cardiac cycle
ventricular systole; duration 0.3 seconds
During ventricular systole
ventricles force blood out the semilunar valves
Each ventricle ejects
70ml of blood into the receiving artery, leaving 60ml in each ventricle
Ventricular ejection
period when SL valves and blood is ejected from the ventricles
End-systolic volume
blood left in ventricle after contraction
Stroke volume
volume of blood ejected per heartbeat from each ventricle
Heart beating at rest formula
Step 3 cardiac cycle
relaxation period where both atria and both ventricles are relaxed; duration 0.4 seconds
The relaxation period shortens
as the heart rate increases; atrial and ventricular systole only slightly shorten
Ventricular repolarization causes
ventricular diastole, where the ventricles are relaxed
During ventricular repoarization
pressure drops in the ventricles; SL valves close because their cusps are filled from the backflow of the aorta and pulmonary arteries
Dicrotic wave
the rebound of blood off the closed cusps of the aortic valve
Step 4 cardiac cycle
ventricular filling
Ventricular filling
as ventricles relax, pressure drops in the ventricles below atria chamber pressure & the AV valves open and fill the ventricles; beings new cycle
the act of listening to sounds within the body
Auscultation instrument
Heartbeat sounds come from
turbulance of blood caused by heart valves closing
Each heartbeat produces how many sounds
four sounds; but only two are normally heard
Heart sound numbers
S1, S2, S3, S4
Which heartbeat sounds are normally heard
S1, & S2
Heart sound S1
“lubb” sound caused by blood turbulence at the closure of the AV valves just after ventricular systole begins; louder and longer than S2
Heart sound S2
“dupp” sound caused by blood turbulence at the closure of the SL valves at the start of ventricular diastole
Heart sound S3
not normally heard; blood turbulence during *rapid ventricular filling*
Heart sound S4
not normally heard; blood turbulence during *atrial systole*
Heart murmur
an abnormal sound consisting of clicking, rushing, or gurgling noise heard during or between beats; common in children
Heart murmur example in adults
mitral incompetence (valve not fully closed); occurs during ventricular systole between S1 and S2
Cardiac Output
the volume of blood per *minute* ejected from the left or right ventricle into the aorta or pulmonary trunk
Cardiac Reserve
the difference between a person’s maximum cardiac output & cardiac output at rest
Two things that can affect cardiac output
stroke volume & heart rate
3 factors that regulate stroke volume
preload, contractility, and afterload
elevated blood pressure
narrowing of the arteries
Increased afterload causes
stroke volume to deecrease
Decreased afterload caused
stroke volume to increase
2 factors that regulate heart rate
ANS & hormones
The cardiovascular center is located in
the medulla oblongata
Cardiac Accelerator Nerves are
sympathetic nerves that extend out to the SA node, VA node, & myocardium
Sympathetic path of cardiac accelerator nerves releases
Parasympathetic path of cardiac accelerator nerves releases
Hormones that regulate the heart rate are released by
the adrenal medullae