Transcript Structure and Function of the Heart

Cardiovascular System
The Heart
Heart Facts
• The cardiovascular system is composed of the heart and a closed
system of vessels through which blood is circulated.
• Hollow muscular organ
• Tipped slightly so that a part of it sticks out and taps against the left
side of the chest (apex), which is what makes it seem as though it is
located there.
• During an average lifetime, the human heart will beat more than 2.5
billion times.
• Beats over 100,000 times/day and 35 million times/year to pump
blood around the body's 60,000 miles of blood vessels.
• 5 pints of blood pump throughout your entire body with one single
heartbeat.
External Structure of the Heart
• Layers
– Edocardium (inner layer)
– Epicardium (outer layer)
– Myocardium (middle layer)
• Pericardium - the protective membrane surrounding the heart
• Coronary arteries – supply blood to the outside of the heart
External Structure
Internal Structure
•
•
•
Atria and ventricles
atria contract while the ventricles relax
ventricles contract while the atria relax.
•
Atrioventricular (AV) Valves
• Bicuspid (Mitral) Valve –
between left atria and
ventricle
• Tricuspid Valve – between
right atria and ventricle
Semilunar (SL) Valves
• Pulmonary SL Valve –
between right ventricle and
pulmonary artery
• Aortic SL Valve – between left
ventricle and aorta
•
•
Ventricular Septum - right and left
ventricles are divided by a thick
muscular wall
– babies born with "hole in the
heart“
– Why problematic?
Septum
connect papillary muscles to AV valves
“heartstrings”
The Cardiac Cycle
•
The events associated with one heartbeat.
•
A single cardiac cycle lasts 0.8 seconds
•
Described as the contraction and relaxation of the four heart chambers.
– During relaxation, chambers fill with blood (diastole).
– During contraction, chambers expel blood (systole).
Heart Sounds
• The first heart sound (lubb)
– occurs during ventricular contraction
– when the tricuspid and bicuspid valves (AV valves) close.
•
The second heart sound (dubb)
– occurs during ventricular relaxation
– when the pulmonary and aortic valves (SL valves) close.
•The walls of the left ventricle are thicker as it has to pump blood to all the tissues,
compared to the right ventricle which only pumps blood as far as the lungs.
Septum
Blood Pressure
• Blood moves through circulatory system from areas of high pressure
to low pressure. (Contraction of the heart produces the pressure.)
• Blood Pressure is a measurement of the force that blood exerts
against the inner walls of arteries.
• 120/80 is normal = systole/diastole
– systolic pressure - The maximum pressure during ventricular
contraction; systolic pressure is the peak arterial pressure.
– diastolic pressure - The lowest pressure of blood in the arteries
during ventricular relaxation (diastole); the arterial pressure drops.
Blood Pressure vs. Distance From Left Ventricle
Conduction System
• Heart muscle cells contract
without stimulation from the
nervous system in a
continuous, rhythmic pattern.
• Contraction is initiated by the
sinoatrial (SA) node
(pacemaker).
– SA node is located in the right
atrium
– Cells of the SA node can
reach threshold on their own
– SA node initiates one action
potential after another (~70-80
times/min)
• Pathway of electrical impulse
– Sinoatrial (SA) node
– Atrioventricular (AV) node
– Atrioventricular bundle (bundle
of His)
– Bundle branches
– Purkinje fibers
Electrocardiograms (ECG / EKG)
• A recording of the electrical
changes that occur within
the myocardium as the
heart contracts.
R atr cont
Electrocardiograms (ECG / EKG)
Atria repolarized
Ventricle depolarized
Heart relaxed
AV node and
walls depolarize
Atrial walls
completely
depolarized
Atria repolarizes
Ventricle
depolarizes
Ventricular walls
repolarize
Cardiomyopathies
•
Heart Valves
– Stenosed Valves – valves that are
narrower than normal, slowing
blood flow from heart chamber
– Rheumatic Heart Disease –
delayed inflammatory response to
streptococcal infection that occurs
most often in children; valves
become inflammed
– Mitral Valve Prolapse (MVP) –
affects bicuspid or mitral valve;
flaps of valve extend back into the
left atrium causing the valve to
leak; asymptomatic or pain and
fatigue
– Aortic Regurgitation – blood ejects
into aorta and regurgitates back
into left ventricle due to leaky
aortic SL valve; ventricle becomes
too full and can cause MI
Cardiomyopathies
•
Myocardium
–
–
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–
–
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Coronary Artery Disease (CAD) – One of
leading causes of death in US; reduced
blood flow to myocardial tissue; occlusion
causes cells deprived of oxygen and
eventually die
Heart Attack
• Myocardial Infarction (MI)
– myocardial = heart muscle tissue
– infarction = tissue death due to
oxygen starvation
• A blood clot completely blocks a
coronary artery (or one of its branches),
cutting off oxygen supply to that part of
the heart. This results in cardiac tissue
death.
Atherosclerosis – hardening of the arteries
due to fatty build up
Angina pectoris – myocardium deprived of
oxygen causing severe chest pain; warning
that coronary arteries can not supply heart
with necessary oxygen
Coronary Bypass Surgery – treatment for
coronary artery blood flow constriction; veins
are harvested from other areas of body and
used to bypass blockages
Congestive Heart Failure (CHF) – “left-side
heart failure”; inability of left ventricle to pump
blood effectively; could result from MI
caused by CAD
Cardiomyopathies
• Arteries
– Arteriosclerosis – hardening of the arteries causing blockage and
weakening of the arterial walls; calcium deposits form; painful and life
threatening
– Ischemia – decreased blood supply to tissue; gradual cell death
– Necrosis – tissue death
– Gangrene – necrosis that has progressed to having decomposing
bacteria
– Angioplasty – procedure to mechanically open the affected area of an
artery like in atherosclerosis patients; catheter inserts balloon to inflate
and push out plaque; stents can be inserted to keep artery open
– Aneurysm – arterial wall damage due to arteriosclerosis or other factors;
section of artery abnormally widened because of weak arterial wall;
causes clot formation that travels (thrombus) that can cause an
embolism (blockage) in the heart; tendency to burst resulting in death
– Cerebrovascular Accident (CVA) aka Stroke – results from brain tissue
ischemia caused by an embolism or ruptured aneurism; effects range
from hardly noticeable to crippling effects
Balloon Angioplasty
Cardiomyopathies
• Veins
– Varicose Veins – enlarged
veins where blood tends to
pool rather than continuing to
the heart; occur in superficial
veins
– Hemorrhoids – varicose veins
in the anal canal due to
excessive straining
– Phlebitis – vein inflammation
– Thrombophlebitis – acute
phlebitis caused by a
thrombus; pain and discolored
tissue
– Pulmonary Embolism –
embolus lodged in lung; death
quickly
Heart Attack
• In this illustration, a
clot is shown in the
location of #1. Area
#2 shows the portion
of the damaged heart
that is affected by the
clot.
Heart Attack Animation
Heart Transplant
The surgeon will begin by exposing the chest cavity through a cut in the
ribcage. The surgeon will then open the pericardium (a membrane that covers
the entire heart) in order to remove your diseased heart. The back part of your
own left atrium will be left in place, but the rest of the heart will be removed.
Your new heart will be carefully trimmed and sewn to fit the remaining parts of
your old heart. This transplant method is called an "Orthotopic procedure". This
is the most common method used to transplant hearts.
You will be given medications both before and during the operation to prevent you
from rejecting the new heart.
Live heart to be transplanted into patient