Transcript Cardiovascular System

Cardiovascular System
Anatomy and Physiology
Cardiovascular System
• Consists of heart—pump
• System of blood vessels --transport
Cardiovascular System
• Heart is covered by
the pericardium
• This is like a thin
membranous sac for
protection
Cardiovascular System
• Heart has four
chambers: 2 atria on
top and 2 ventricles on
the bottom
• Atria are receiving
chambers
• Ventricles are
pumping chambers,
and have thicker walls
Cardiovascular System
• Heart is also divided
into right and left
• Blood on the right side
does not mix with
blood on the left side
Blood which enters the
right atrium goes on to
the right ventricle
Enters left atrium; leaves
left ventricle
Cardiovascular System
• Blood entering the
right side of the body
is coming from the
veins of the body and
is low oxygen
• It is sent from the right
ventricle to the lungs
Cardiovascular System
• Blood entering the left
side of the heart has
come from the lungs
and is oxygenated
• It is sent from the left
ventricle through the
arteries to all parts of
the body
Cardiovascular System
• Valves separate the atria
from the ventricles
• On the right side, it is the
tricuspid valve
• On the left side, it is the
bicuspid valve
• They close to prevent flow
when it should be sealed
off
Label the Heart
Pulmonary vs Systemic
• The pulmonary circuit
goes from the right
atrium to the right
ventricle
• And then to the lungs,
returning to the left
atrium
Pulmonary vs Systemic
• Systemic circulation
goes from the left
atrium into the left
ventricle
• And then to all body
parts (oxygenated)
Initiating the Heartbeat
• The “pacemaker”
system
• Involves specialized
pockets of heart tissue
which can initiate
impulses
• The first pocket is
called the S-A
(sinoatrial) node
S-A node
• Initiates the heartbeat
• Is located in the right
atrium
• Causes both atria to
contract (small
contraction to send blood
into ventricles)
• Impulse also travels on
fibers to the next
specialized pocket
A-V Node
• The A-V node
(atrioventricular)
receives the impulse
from the S-A node
• Located in the septum
where the atrium
meets the ventricle
• Impulse is relatively
slow, allowing time
for the ventricles to fill
A-V Node passes it on
• From the A-V node,
the impulse goes to the
A-V bundle (also
called the Bundle of
His)
• From there is branches
into Purkinje fibers
that enclose both
ventricles
The Big Push
• When all the cardiac
muscle cells receive
the impulse, the
ventricles contract
together and
powerfully.
• This is systole
Steps in Order
•
•
•
•
•
SA node
AV node
AV bundle
Bundle branches
Purkinje fibers
Replacement
• If the SA node fails to
keep a regular rhythm,
an artificial pacemaker
can be inserted.
ECG
• Electrocardiogram
• Sometimes called
EKG
• Recording of electrical
changes
• Records the electrical
impulses of action
potentials
The Blood Vessels
• Arteries lead away from the heart
• Arteries branch into arterioles (smaller
arteries,) then into tiny capillaries
• Capillaries merge together to form venules
(small veins)
• Venules merge to become larger veins
which return blood to the heart
Arteries
• Strong
• Elastic
• Able to withstand the
pumping pressure
• Three layers in the
wall—one layer
contains smooth
muscle
Arteries
• The muscle allows the
artery to constrict
(reduce diameter) and
dilate (increase
diameter)
• This is important in
maintaining body
temperature
Capillaries
• Smallest diameter
• Connect the smallest
arterioles with the
smallest venules
• The wall is only one
layer thick—very thin!
• Exchange of materials
occurs here
Veins
• Venules merge to form
larger veins
• Walls have three
layers, but much
thinner
• Less muscle and
elastic tissue
• Collapse when empty
Artery and Vein Comparison
Artery
Vein
Veins
Valves open
• Contain valves to
prevent back flow
• Most valves are in
veins of the limbs
• Harder to return blood
from these parts, due
to low pressure
Valves closed
Valves
Valves
Veins
• By the time blood gets
to the veins, it has
little force behind it.
• It’s hard to get blood
back to the heart
• Valves help, but also
skeletal muscle
movement and
respiration help
Blood Pressure
• Force blood exerts
against the walls of the
blood vessels.
• Primarily in the
arteries, since they are
subject to the most
force
• Can feel a pulse in
arteries
Blood Pressure
• Systolic pressure is the
pressure during ventricular
contraction
• Diastolic pressure is the
pressure during ventricular
relaxation
• A blood pressure reading
is expressed as
• systolic pressure
diastolic pressure
Blood Pressure
• A normal blood
pressure reading is
120/80.
• Generally, lower is
better
• Hypertension may
result in heart
enlargement, heart
attack, atherosclerosis,
stroke
Exercise, controlling
weight, limiting sodium,
reducing stress, and
medication are treatments
for high blood pressure
Blood Pressure
• Factors affecting blood
pressure include:
• Amount of blood pumped
by the left ventricle and
how often
• Blood volume
• Peripheral resistance
• Blood viscosity