Transcript pulmonary semilunar valves

PowerPoint® Lecture Slides
prepared by Vince Austin,
Bluegrass Technical
and Community College
CHAPTER
Elaine N. Marieb
Katja Hoehn
18
PART A
Human
Anatomy
& Physiology
SEVENTH EDITION
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Cardiovascular
System: The Heart
Circulatory System – designed for transportation
of oxygen, nutrients, cell wastes, hormones, and
other substances vital for body homeostasis
• Two major divisions – the cardiovascular system and
lymphatic system
• Heart - major organ of the circulatory system
- hollow, four chambered
- about the size of a person’s fist
Vessels: lymph vessles and arteries, veins, and capillaries
for blood
Blood Vessels – transports blood from the heart
to the capillaries and back to the heart
• Blood leaves heart -> large arteries → smaller arteries ->
arterioles -> capillaries for gas and solute exchange →
venules → veins → heart
• Arteries always carry blood away from heart; veins always
return blood to the heart
• Exchanges between tissue cells and blood occur only in the
capillary beds
Generalized Structure of Blood Vessels
Figure 19.1b
Blood Vessel Structure
•
Tunica intima
–
–
•
Endothelial layer (squamous epithelium) that lines the
lumen
slick surface decreases friction for moving blood
Tunica media
–
–
mostly smooth muscle and elastic tissue
• smooth muscle is controlled by sympathetic nervous
system – changes diameter of vessels
as vessels dilate or constrict, blood pressure increases or
decreases
•
Tunica externa
–
–
outermost tunic
collagen fibers that
protect and reinforce
vessels
Elastic Arteries
• Thick-walled arteries near the heart; the aorta and its
major branches
– Large lumen allow low-resistance conduction of
blood
– Contain elastin to allow for recoil from blood
pressure
– Has the most smooth muscle to allow for dilation and
constriction
Muscular Arteries and Arterioles
• Muscular arteries – distal to elastic arteries; deliver blood
to body organs
• Arterioles – smallest arteries; lead to capillary beds
– Control flow into capillary beds via vasodilation and
constriction
Capillaries
• The smallest blood vessel
– Walls are one cell thick
– Allow only a single RBC to pass at a time
– about 1 mm long (combined length in body = 60,000
miles)
– all cells in body are less than a mm away from any
capillary for exchanges between blood and interstitial
fluid for gases and wastes
Vascular
Components
Figure 19.2a, b
Capillary Beds
Figure 19.4a
Capillary Beds
Figure 19.4b
Venous System: Venules
• Venules are formed when capillary beds unite
– Allow collected fluids and solutes to pass from the
tissues into the circ. system
• low pressure (about 2 mmHg); too low to return blood to
heart against gravity
Veins
• Veins are:
– Formed when venules converge
• Veins have much lower blood pressure and thinner walls than
arteries
• To return blood to the heart, veins have special adaptations
– Large-diameter lumens, which offer little resistance to flow
– Valves which prevent backflow of blood when blood is pushed
up by skeletal muscle contraction
Blood Pressure (BP)
• Force per unit area exerted on the wall of a blood vessel
by its contained blood
– Expressed in mm Hg
– Measured in reference to systemic arterial BP in
large arteries near the heart
– Systolic- when heart contracts, higher BP
– Diastolic- when heart relaxes and fills up with blood
• The differences in BP within the vascular system
provide the driving force that keeps blood moving from
higher to lower pressure areas
Systemic Blood Pressure
Figure 19.5
Factors Aiding Venous Return
• Venous BP alone is too low to
promote adequate blood return and is
aided by the:
– Respiratory “pump” – pressure
changes created during breathing
suck blood toward the heart by
squeezing local veins
– Muscular “pump” – contraction of
skeletal muscles push blood
toward the heart
• Valves prevent backflow during
venous return
Monitoring Circulatory Efficiency
• Efficiency of the circulation can be assessed by taking
pulse and blood pressure measurements
• Vital signs – pulse and blood pressure, along with
respiratory rate and body temperature
• Pulse – pressure wave caused by the expansion and recoil
of elastic arteries
– Radial pulse (taken on the radial artery at the wrist) is
routinely used
– Varies with health, body position, and activity
Palpated Pulse
Figure 19.11
Measuring Blood Pressure
• Systemic arterial BP is measured with auscultation
– A sphygmomanometer is placed on the arm superior to
the elbow
– Pressure is increased in the cuff until it is greater than
systolic pressure in the brachial artery
– Pressure is released slowly and the examiner listens with
a stethoscope
– The first sound heard is recorded as the systolic pressure
– The pressure when sound disappears is recorded as the
diastolic pressure
Variations in Blood Pressure
• Normal is 90-120/60-80 mm Hg
• Affected by age, sex, weight, race, mood, socioeconomic
status, and physical activity
• Hypotension – systolic pressure is below 90 mm Hg, can also
occur from sitting or laying too long and quickly rising
• Hypertension – condition of sustained elevated arterial
pressure of 140/90 or higher
– can be caused by fever, physical exertion, and emotional
upset
– Chronic hypertension can be caused by diet, obesity, age,
race, heredity, stress, smoking, arteriosclerosis, and
endocrine disorders
– Chronic elevation is a major cause of heart failure,
vascular disease, renal failure, and stroke
Heart Anatomy
• Location
– located within the thoracic cavity in the region known as
the mediastinum
– Left of the midline, flanked on both sides by the lungs
– Superior of diaphragm
– Anterior to the vertebral column, posterior to the sternum
– pointed apex is directed toward the left hip and rests on
the diaphragm at the level of the fifth intercostal space
– broader base, from which the great vessels emerge, points
toward the right shoulder and lies beneath the second rib
Coverings of the Heart: Anatomy
• Pericardium – a double-walled sac of serous membrane
around the heart composed of:
– A superficial fibrous pericardium for protection
– A deep two-layer serous pericardium which produces
lubricating fluid which allows frictionless environment
for beating heart
• parietal layer lines the internal surface of the fibrous
pericardium
• visceral layer or epicardium lines the surface of the
heart
• separated by the fluid-filled pericardial cavity
Pericardial Layers of the Heart
• Pericarditis – inflammation of the pericardium; results in
decrease in the amount of serous fluid; causes pericardial
layers to bind & stick to each other, forms painful adhesions
that interfere with heart movements
• Heart Walls – composed of three layers:
1. Epicardium – outside visceral layer; protection
2. Myocardium – thick bundles of cardiac muscle tissue
twisted into ringlike arrangements; forms the bulk of the
heart; responsible for pumping action (contracts)
3. Endocardium – thin, glistening sheet of endothelium that
lines the heart chambers; continuous with endothelium of
blood vessels
Cardiac Muscle Bundles
External Heart: Major Vessels of the
Heart (Anterior View)
• Vessels returning blood to the heart include:
– Superior and inferior venae cavae
– Right and left pulmonary veins
• Vessels conveying blood away from the heart:
– Pulmonary trunk, which splits into right and left
pulmonary arteries
– Ascending aorta (three branches) – brachiocephalic,
left common carotid, and subclavian arteries
Brachiocephalic trunk
Superior vena cava
Left common carotid
artery
Left subclavian artery
Aortic arch
Right pulmonary
artery
Ligamentum arteriosum
Ascending aorta
Left pulmonary artery
Pulmonary trunk
Right
pulmonary veins
Right atrium
Left pulmonary veins
Left atrium
Circumflex artery
Right coronary
artery
Anterior cardiac
vein
Right ventricle
Left coronary artery
Small cardiac vein
Anterior interventricular
artery
Inferior vena cava
Left ventricle
Great cardiac vein
Apex
Figure 18.4b
External Heart: Major Vessels of the
Heart (Posterior View)
• Vessels returning blood to the heart include:
– Right and left pulmonary veins
– Superior and inferior venae cavae
• Vessels conveying blood away from the heart include:
– Aorta
– Right and left pulmonary arteries
Aorta
Superior vena cava
Left pulmonary artery
Right pulmonary artery
Left
pulmonary veins
Right pulmonary veins
Right atrium
Left atrium
Inferior vena cava
Great cardiac vein
Posterior vein
of left ventricle
Right coronary artery
Coronary sinus
Left ventricle
Apex
Posterior interventricular
artery
Middle cardiac vein
Right ventricle
Figure 18.4d
Superior vena cava
Aorta
Right pulmonary
artery
Left pulmonary
artery
Pulmonary trunk
Right atrium
Right
pulmonary veins
Fossa ovalis
Left atrium
Left pulmonary
veins
Mitral (bicuspid)
valve
Aortic valve
Pectinate
muscles
Pulmonary valve
Tricuspid valve
Left ventricle
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior
vena cava
Papillary muscle
Interventricular
septum
Myocardium
Visceral
pericardium
Endocardium
Figure 18.4e
Chambers, Valves, and Vessels
• Heart is a double pump consisting of four hollow chambers –
two atria and two ventricles
-each chamber is lined with endocardium which helps blood
flow smoothly
• Superior left & right atria – receiving chambers; not
important in pumping activity of heart; contract and empty
blood into the ventricles
• Interatrial septum – divides atria longitudinally
• Inferior left & right ventricles – discharging chambers;
pumps of the heart; propels blood out of the heart and into
circulation
• Interventricular septum – divides ventricles longitudinally
•
Double pump consisting of:
1.
right side – works as pulmonary circuit pump
-receives oxygen-poor blood from veins of body through
the superior and inferior venae cavae and coronary sinus
and pumps it out through the pulmonary trunk
-pulmonary trunk splits into the right and left pulmonary
arteries, which carry blood to lungs, where oxygen is
picked up & carbon dioxide is unloaded
-oxygen-rich blood returns to left side of heart through 4
pulmonary veins
1.
Left side – systemic circulation
-blood returns to left side of heart from pulmonary veins
and is pumped out of heart into the aorta to supply all
body tissues
-supplies nutrient-rich blood to all body organs
-oxygen poor blood is returned to the right atrium
through the superior and inferior venae cavae
-walls of left side are thicker than those of right ventricle
because it must pump blood over much longer pathway
through body
Right and Left Ventricles
Pathway of Blood Through the Heart and
Lungs
• Right atrium  tricuspid valve  right ventricle
• Right ventricle  pulmonary semilunar valve 
pulmonary arteries  lungs
• Lungs  pulmonary veins  left atrium
• Left atrium  bicuspid valve  left ventricle
• Left ventricle  aortic semilunar valve  aorta
• Aorta  systemic circulation
Cardiac circulation – flow of blood through
vessels in the myocardium of heart
• Left and right coronary arteries – main coronary vessels;
arise from aorta
• Each artery forms many branches to deliver oxygen &
nutrients to cells of heart wall and to collect wastes from
cells; become compressed when ventricles contract & fill
when ventricles relax
• Myocardium is drained by cardiac veins, which empty into
coronary sinus, which empties into right atrium
Coronary Circulation: Arterial Supply
Figure 18.7a
Coronary Circulation: Venous Supply
Figure 18.7b
•
Valves – allow blood to flow in only one direction through the
heart chambers; 4 valves – 2 types
1.
Atrioventricular, or AV valves are located between the atrial
and ventricular chambers on each side; prevent backflow into
the atria when ventricles contract
-left AV valve – bicuspid or mitral valve – consists of two cusps
-chordae tendineae – “heart strings” – anchor cusps to walls of
ventricles so that they can’t be pushed up into atria
-papillary muscles secure chordae tendineae to
ventricular walls
-right AV valve – tricuspid valve – has three cusps
1.
semilunar valves – guards bases of large arteries leaving
ventricular chambers; both have three cusps; open when
ventricles contract; closed when ventricles relax to
prevent blood from reentering heart
- pulmonary semilunar valves – located between right
ventricle and pulmonary artery
- aortic semilunar valves – located between left ventricle
and aorta
Heart Valves
Heart Valves
Atrioventricular Valve Function
Semilunar Valve Function
Leaky Valves – may be mild or severe
• Mild leaks may be heard as a heart murmur; when a valve
does not close tightly (incompetent), a swishing sound will be
heard as blood flows backwards through a partially open
valve; forces heart to pump and repump same blood, heart
weakens and fails
• Valvular stenosis – valve flaps become stiff, often because of
repeated bacterial infections (endocarditis); compels heart to
contract more forcible than normal, heart weakens and fails
• Valves may be replaced with synthetic valve or valve from a
pig heart
Replacement Mitral Valves
Mechanical Valve
Pig Valve
• Angina pectoris – when heart beats at very rapid rate,
myocardium may receive inadequate blood supply because
relaxation periods (when blood is able to flow to the heart
tissue) are shortened
-results in myocardium being deprived of oxygen which
results in crushing chest pain
-myocardial infarction (heart attack or coronary) may
occur as ischemic (deprived of blood) heart cells die
Conduction system of the Heart may be
controlled in two ways
1. Nerves from autonomic nervous system
- act to decrease (parasympathetic nervous
system) or increase (sympathetic nervous
system) heart rate depending on which
division is activated
2. Intrinsic rhythmicity - cardiac muscle cells can contract
spontaneously and independently from central nervous
system stimulation
- nodal tissues - specialized cardiac muscle tissue which
coordinates contractions
- composed of specialized tissue much like a cross between
muscle and nerve tissue
Parts of intrinsic conduction system
• Sinoatrial (SA) node - located in the right atrium; tiny cell
mass which has highest rate of depolarization in the whole
system
- starts each heartbeat and sets pace of whole heart;
generates impulses about 75 times/minute
-often called the pacemaker
• atrioventricular (AV) node - located at junction of the atria
and ventricles; delays impulse approximately 0.1 second
from atria until contraction is complete
• atrioventricular bundle (bundle of HIS) - receives impulses
from AV node; located in septum
• Bundle branches - located in the interventricular septum;
receives impulses from AV bundle and passes them on to
Purkinje fibers
• Purkinje fibers - spread impulses within muscle of ventricle
walls
-results in “wringing” contraction of the ventricles that
begins at the apex and moves toward atria; effectively
ejects blood superiorly into large arteries leaving the
heart
Cardiac Intrinsic Conduction
• Heart block results in the atria and ventricles beating at
different rates
-atria and ventricles are separated from one another by
“insulating” connective tissue; depolarization waves can
reach the ventricles only by traveling through the AV node
-damage to the AV node can partially or totally release the
ventricles from the control of the SA node
-ventricles beat at their own rate which is much slower
• Fibrillation - rapid uncoordinated shuddering of the heart
muscle (bag of worms); makes heart totally useless as a
pump and is major cause of death from heart attacks in
adults
-usually due to Ischemia - lack of adequate blood supply to
the heart muscle
• damage to SA node - results in slower heart rate; artificial
pacemakers usually installed surgically to correct rhythm
• tachycardia - rapid heart rate (over 100 beats/min); may
progress to fibrillation
• bradycardia - slow heart rate (less than 60 beats/min); not
pathological
Electrocardiology - recording of electrical
currents of the heart
• Impulses can be detected on the body surface and recorded
with an electrocardiograph (ECG)
-two or more electrodes are placed on skin over the heart;
position of electrodes provides different info.
• Typical ECG has three recognizable waves
1. P wave - small and signals the depolarization of the atria
immediately before they contract; missing or abnormal
wave indicates dysfunction of SA node
2. QRS complex - results from the depolarization of the
ventricles; precedes the contraction of the ventricles;
abnormal QRS generally indicates heart problems of the
ventricles; enlarged R spike indicates enlarged ventricles
3. T waves - results from currents flowing during the
repolarization of the ventricles; altered wave may indicate
arteriosclerosis or other heart diseases
- atrial repolarization is generally hidden by the large QRS
complex which is being recorded at the same time
-abnormalities in the shape of the waves and changes in
their timing send signals that something may be wrong
with the intrinsic conduction system or may indicate a
myocardial infarct (present or past)
-myocardial infarct - area of heart tissue in which heart
cells have died
•
during fibrillation, the normal pattern of the ECG is
totally lost and the heart ceases to act as a functioning
pump
Electrocardiography
Heart Excitation Related to ECG
SA node generates impulse;
atrial excitation begins
SA node
Impulse delayed
at AV node
AV node
Impulse passes to
heart apex; ventricular
excitation begins
Bundle
branches
Ventricular excitation
complete
Purkinje
fibers
SA node generates impulse;
atrial excitation begins
SA node
Impulse delayed
at AV node
AV node
Impulse passes to
heart apex; ventricular
excitation begins
Bundle
branches
Ventricular excitation
complete
Purkinje
fibers
Heart Excitation Related to ECG
SA node generates impulse;
atrial excitation begins
SA node
Impulse delayed
at AV node
AV node
Impulse passes to
heart apex; ventricular
excitation begins
Bundle
branches
Ventricular excitation
complete
Purkinje
fibers
Extrinsic Innervation of
the Heart
• Heart is stimulated by the
sympathetic
cardioacceleratory center
• Heart is inhibited by the
parasympathetic
cardioinhibitory center
ECG Tracings
(a) Normal sinus rhythm
(b) Junctional rhythm – SA node nonfunctional – no P waves – pacing by
AV node at 40-60 beats/min
(c) second-degree heart block – some P waves not conducted through AV
node
(d) Ventricular fibrillation – seen in acute heart attack and electrical shock
Cardiac Cycle and Heart Sounds
• Cardiac cycle - events of one complete heartbeat, during
which both atria and ventricles contract and then relax;
usually takes about 0.8 sec.
• systole - heart contraction
• diastole - heart relaxation
(these terms always refer to the contraction and relaxation
of the ventricles unless otherwise stated)
Cardiac cycle may be divided into three periods
1.
Mid-to-late diastole - complete relaxation
-pressure in heart is low blood is flowing passively into
and through the atria into the ventricles from the
pulmonary and systemic circulations
-semilunar valves are closed
-AV valves are open
-atria contract and force blood remaining in their
chambers into the ventricles
2.
-
Ventricular systole - ventricular contraction begins &
pressure builds up rapidly
increasing pressure causes AV valves to close; produces
characteristic “lub” heart sound
-
isovolumetric contraction - contraction of ventricle when
both valves are shut; blood volume in the ventricle is not
changing
-
semilunar valves open when pressure in heart is higher
than pressure in large arteries leaving the heart
-
atria are relaxed and begin filling with blood
3.
-
Early diastole - ventricles relax
pressure in ventricles begins to drop as ventricle relaxes
-
semilunar valves snap shut (prevents backflow of blood
from arteries into ventricles); produces characteristic
“dub” heart sound
-
isovolumetric relaxation - AV and semilunar valves are
shut and ventricles are expanding; volume is not
changing
-
when pressure in ventricles drops below pressure in
atria, AV valves open and ventricles fill with blood
Cardiac Output – amount of blood pumped out
by each side of the heart in 1 minute
• Stroke volume (SV) – volume of blood pumped out by a
ventricle with each heartbeat
-increases as the force of ventricular contraction increases
• cardiac output (CO)
CO = Heart rate (HR) x SV
CO = HR (75 beats/min) x SV(70 ml/beat)
CO = 5250 ml/min
• Average adult blood volume is about 5000 ml; entire blood
supply passes through the body once every minute
Regulation of stroke volume
• Starling’s law of the heart – the critical factor controlling
stroke volume is how much the cardiac muscle cells are
stretched just before they contract
• More stretching = stronger contraction
• More venous return = more stretching
• Anything that increases the volume or speed of venous
return also increases stroke volume and force of contraction
• Severe blood loss or very rapid heart rate decreases venous
return which decreases stroke volume causing the heart to
beat less forcefully
Regulation of Heart Rate – may be influenced
temporarily by the autonomic nerves, and by
various chemicals, hormones, and ions
• Sympathetic division of autonomic nervous system stimulate
the SA and AV nodes and the cardiac muscle itself to beat
more rapidly
-allows blood to reach body cells during periods of stress,
excitement, or exercise (brings more oxygen and glucose)
• Parasympathetic nerves slow and steady the heart when
demand declines during non-crisis times
• Epinephrine – mimics sympathetic nerves
• Thyroxine – increases heart rate
• Electrolyte imbalances pose threat to heart
-low blood calcium = depress heart
-high blood calcium (hypercalcemia) – prolonged
contractions; heart may stop entirely
• Physical factors influence hart rate
-age –
fetus = 140-160 beats/min
- gender - females = 72-80 beats/min
males = 64-72 beats/min
-increased body temperature = increased heart rate (fever,
exercise)
• Congestive heart failure – condition in which the heart is
nearly “worn out” due to age or hypertensive heart disease,
the heart is depressed so that circulation is inadequate to
meet tissue needs; progressive
-reflects weakening by coronary artherosclerosis,
persistent high blood pressure, or multiple myocardial
infarcts
-death due to suffocation (fluid in lungs) or complete
heart failure
-digitalis – drug which simulates parasympathetic nerve;
slows and steadies the heart, resulting in a stronger
heartbeat
Developmental Aspects of the Heart
• Fetal heart structures that bypass pulmonary
circulation
– Foramen ovale connects the two atria
– Ductus arteriosus connects pulmonary trunk
and the aorta
Examples of Congenital Heart Defects
Age-Related Changes Affecting the Heart
• Sclerosis and thickening of valve flaps – occurs where stress of blood
flow is greatest (mitral valve) – results in heart murmurs
• Decline in cardiac reserve – aged heart less able to respond to both
sudden and prolonged stressors that demand increased output;
sympathetic control less efficient, HR becomes more variable & there
is a decline in max HR – less of a problem if physically active
• Fibrosis of cardiac muscle – cardiac cells die & are replaced with
fibrous tissue; heart stiffens & is less efficient; decreased stroke
volume; stiffened nodes result in conduction problems (arrhythmias)
• Atherosclerosis – leads to heart attack and stroke; accelerated by
inactivity, smoking, stress; diet is more important contributor than
age
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Anterior
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Coronary Circulation: Arterial Supply
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Coronary Circulation: Venous Supply
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