Transcript Heart PPT

The Heart
Pulmonary Circulation and Systemic
Circulation
The heart is considered to be a
double pump because it pumps
blood through 2 different loops:
1. pulmonary circulatory loop
2. systemic circulatory loop
Pulmonary loop
System loop
1. Pulmonary Circulation – the right
side of the heart is
responsible for the
pulmonary circulation
• it pumps deoxygenated
blood to the lungs (where it
is oxygenated) and back to
the left side of the heart
2. Systemic Circulation – the left
side of the heart is
responsible for the systemic
circulation
• it pumps oxygenated
blood to the entire body
and back to the right side
of the heart
Which side of the heart has to work
the hardest?
the left side, because it has to
pump blood to the entire body
• the right side does not have
to work as hard because it is
only pumping blood to the
lungs
Structure of the Heart:
Your heart is divided into 4
chambers:
2 upper chambers called atria
right atrium and left atrium
right atrium
left atrium
2 lower chambers are called
ventricles
(right ventricle and left
ventricle)
right ventricle
left ventricle
The right side of the heart is
separated from the left side by a
wall of tissue - septum
septum
• it is important that this septum
remain intact because the right
side pumps deoxygenated
blood, while the left side
pumps oxygenated
The right atrium is separated from
the right ventricle by a valve –
tricuspid valve
The left atrium is separated from the
left ventricle by a valve – mitral
(bicuspid) valve
• this valve prevents blood from
flowing backward into the left
atrium once it has entered the
left ventricle
Why do we want to prevent the
backflow of blood in the heart?
• The heart is a pump – for it to
work effectively, it must pump
blood in one direction only
Flow of Blood through the Heart:
• blood re-enters the heart
through the superior and inferior
venae cavae
• the superior vena cava collects
blood returning from the head
and arms, while the inferior vena
cava collects blood returning
from the trunk and legs
vena cavae  enter right atrium 
pass through the tricuspid  enter right ventricle 
pass through the pulmonary valve 
enter the pulmonary arteries (to lungs to get O2) 
exit lungs through the pulmonary veins 
left atrium  pass through the mitral valve 
left ventricle  pass through the aortic valve 
enter the aorta (largest artery) 
pass through entire body
Conduction System of the Heart
The normal rate and rhythm of your
heartbeat is regulated by a
special region of cardiac
muscle cells called the
sinoatrial node (SA-node)
• since the SA-node regulates your
heartbeat it is called the
pacemaker
• the SA-node is located in the
upper portion of the right atrium
• it generates an impulse 60 -75
times per minute (heart rate)
• every time the SA-node
generates an impulse, it spreads
very rapidly to all other cardiac
muscle cells in both atria,
causing them to contract at the
same time
• when both atria contract, blood is
forced into the ventricles
The impulse generated by SA-node
does not stop in the atria – it will
be picked up by another special
region called the atrioventricular
node (AV-node)
• the AV-node is located in the
lower portion of the right atrium
• it receives the impulse and
passes it to a network of fibers
called the Bundle of His
• the Bundle of His spreads the
impulse rapidly to all cardiac
muscle cells of both ventricles,
causing them to contract
• when ventricles contract, blood
is sent from right ventricle to the
lungs, and from the left ventricle
to the body
If the AV-node is damaged, the
impulses generated by the SAnode can not reach the ventricle
• the atria would contract at their
normal rate, but the ventricles
would contract only about 30
times per minute
• this condition is called a heart
block
• it can be treated by installing a
pacemaker
If the SA-node is damaged the
node would take over
AV-
• however, the AV-node would
send out impulses about 50
times per minute
• you can survive a heart rate
this slow; however, in a young
individual, or in older,
extremely active individuals, a
pacemaker would be installed
Devices that Monitor Heart Function
1. Sphygmomanometer – device
that measures blood
pressure
• this device can give you 2
readings: the systolic pressure
and diastolic pressure
Systolic pressure is a measure of
the pressure of the blood
against the wall of the artery
during contraction of the heart
• normal values run from 100 - 130
Diastolic pressure is a measure of
the pressure of the blood
against the wall of the artery
during relaxation of the heart
• normal values run from 70 – 90
Blood pressure readings are
reported as the systolic
pressure written over the
diastolic pressure
• thus, normal blood pressure
reading would be 120/80
If the systolic pressure is
consistently above 200, the
person is said to have
hypertension (high blood
pressure)
• can be dangerous if it is not
controlled
• can lead to heart damage,
stroke (ruptured blood vessels
in the brain), or kidney failure
2. Electrocardiograph (ECG) –
device that measures
electrical changes that
occur in the heart
• every time your heart beats, an
ECG records 3 separate waves:
P wave – measures
contraction of atria
QRS wave – measures
contraction of the
ventricles
T wave – measures relaxation
of the ventricles
• by examining the shape of these
3 waves on the ECG, a doctor
can determine if the heart is
functioning normally
• for example, if the SA-node is
damaged, an ECG would show a
QRS wave and T wave, but no P
wave
• if the heart cannot be repaired by
surgery, a heart transplant is
possible
normal
abnormal
The first human heart transplant was
performed in 1967, by
Dr. Christiaan Barnard, in
Capetown, South Africa
Heart and Blood Vessel Disease
• diseases of the heart and blood
vessels are the leading cause of
death in the US
1. Myocardial infarction = heart
attack
• heart attacks occur because a
portion of the heart dies when
it does not receive enough
blood
• heart attacks are caused by:
fat deposits that build up in,
and close off, the
coronary arteries (arteries
that feed the heart
muscle)
blood clots that form
elsewhere in the body,
break free, and become
lodged in the coronary
arteries
2. Atherosclerosis – build up of fatty
deposits in the inner walls
of arteries in the body
• can cause stroke if it closes off
artery leading to the brain
• can cause a heart attack if it
closes off one of the coronary
arteries
• the fatty deposits are
composed mainly of
cholesterol
3. Arteriosclerosis – hardening of
the arteries
• occurs when calcium is
added to the fatty
deposits caused by
atherosclerosis
• is harmful because it causes
the heart to work harder and
elevates the blood pressure