The Circulatory System Blood, Blood Vessels and the Heart C5: 5 types of Blood Vessels  a.

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The Circulatory System
Blood, Blood Vessels and the
Heart
C5: 5 types of Blood Vessels

a. arteries
b. arterioles
c. veins
d. venules
e. capillaries
Arteries
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Have thick,
muscular walls so
they are able to
withstand the blood
pressure coming
from the heart
Carry blood AWAY
from the heart
Elastic: handle
change in blood
volume after each
ventricular contraction
Arterioles
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Small arteries are
called ARTERIOLES
Not as elastic as
arteries
They relax causing
the arteriole to
dilate, resulting in
the opposite effect:
increase blood
volume, decrease
pressure
Veins
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Carry blood
TOWARDS heart
Have a thin muscle
layer
Contain VALVES to
help the blood
return to the heart
Small veins are
called venules
Valves in Veins
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there is not enough
blood pressure to
make the blood
return all the way to
the heart
One-way valves and
the skeletal muscles
work together to
squish the blood back
heart
Varicose Veins
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If the valves
malfunction in
the legs, a
painful condition
can result
Called Varicose
veins
Allows blood to
pool in the
elastic veins,
causing them to
bulge

Varicose veins in
rectum are called
hemorrhoids.
Capillaries
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Connect the veins and
arteries
Site of gas exchange
between blood and
cells
Oxygen, nutrients and
water diffuse out of
the blood and into the
cells
Carbon dioxide,
wastes and water
diffuse out of the cells
and into the blood

Capillaries have
extremely thin
walls for
diffusion.
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Comparison of
Blood vessels
Most of the bp
that came from
the heart is lost
when the blood
travels through
the capillaries
That is why you
need VALVES in
your veins.
C3: Your Heart – structure and
function
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Mostly Muscle
Beats about 65-75 times
per minute
Is comparable to two
pumps joined together
Has 4 chambers:
Right Atrium, right
ventricle
Left Atrium, Left
Ventricle


Anatomy diagrams are
labelled as if you are
looking down on a
patient (unless otherwise
indicated)
Therefore, the R.A. is
the patient’s right – not
yours!
PIG HEART
Structure of the Heart
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4 One-Way-Valves
between the atria and the
ventricles on both sides =
Atrioventricular valves
at the exit of both
ventricles = semi-lunar
valves
prevent blood from flowing
backwards
If one of your valves is
defective, you might have a
“heart murmur”.

Top View (looking down)
Chordae Tendineae

Anchor AV valves
on ventricles to
prevent valves
from inverting
Chordae Tendineae
Demonstrate the flow of blood
from the aorta through the
body and back to the left
ventricle.
good overview of circulation through heart, nodal control
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Flow of
Blood
through
the
heart
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Blood enters
the R.atrium
via the superior
and inferior
vena cava
When the Atria
contract, blood
moves from the
R.A. to the
R.Ventricle,
passing the AV
valve as it goes
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The ventricles
contract, and
force the
blood through
the semi-lunar
valve and out
to the body
via the AORTA
Blood Flow Video
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Both atria fill and
contract at the same
time.
Both ventricles will
fill and contract at
the same time
occurs when the AV valves
close. The second heart sound
“dub” occurs when the other
valves close.
distinguish between systolic
and diastolic pressures
When the
cardiac muscle
contracts it is
called Systole
 When the
chamber
relaxes it is
called diastole

the SA node, AV node, and
Purkinje fibres
 Our heartbeat is
INTRINSIC.
 SPECIAL TISSUE,
called NODAL TISSUE,
has characteristics of
both nerve and muscle
tissue, controls the
heartbeat.
 There are TWO nodal
regions in the heart:
1. SA (sinoatrial) NODE
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Located upper back
wall of right atrium.
INITIATES THE
HEARTBEAT every
0.85 seconds to make
the ATRIA CONTRACT.
SA Node
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The SA node is
called the
“PACEMAKER”
because it keeps the
beat regular.
ARTIFICIAL
PACEMAKERs, will
send out an electric
signal every 0.85
seconds to stabilize
the heart rate if the
SA node doesn’t
work.
2. AV (atrioventricular) NODE:

SA
Node

AV
Node
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Located base of the R.A.
near the septum.
When the pulse from SA
Node reaches AV node,
the AV node will send out
a signal along conducting
fibers called PURKINJE
FIBERS. They take the
message to the
VENTRICLES, and
cause them to contract.
The contraction of the
ventricles begins at the
Purkinje
base
of theFibers
heart and
moves up like a wave.
Video Clip
autonomic
regulation of the
heartbeat
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Heart under involuntary
control by the brain
MEDULLA
OBLANGATA,
This center can
increase or decrease
the heart rate
Various factors, such as
stress, oxygen levels,
and bp determine how
the ANS will affect heart
rate.
distinguish between pulmonary
and systemic circulation
Heart Beat
Heart in a Box
Flow of Blood: Blood travels in 2
loops
A. The Pulmonary system
- goes from the heart to
the lungs and back to
the heart again

Only place where deoxygenated blood is
in ARTERIES, and oxygenated blood is in
VEINS
Superior Vena
Cava
Aorta
Pulmonary artery
Pulmonary Vein
Inferior Vena Cava
Review
b. Systemic Circuit
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When L. ventricle
pumps to push the
blood to rest of body
This ensures there is
ample blood pressure
for the blood to deliver
it’s oxygen and nutrients
to the cells
The Coronary Arteries
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The heart does not use
the blood inside the
atria or ventricles to
get it’s nutrients and
oxygen
Has own set of arteries
and veins to supply
oxygen and nutrients
= coronary arteries
Circulatory Review
Circulatory rap
Atherosclerosis
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Excess fat and
cholesterol stick to the
arteries, forming a
PLAQUE
Plugs up the arteries,
restricting blood flow
If the blood flow that is
restricted is to the
heart, a heart attack
may occur
Angioplasty –
possible procedure if
the blockage isn’t too severe
Heart Attack
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When the cells of the heart do not get enough
oxygen
The severity of the attack depends on how bad
the coronary artery blockage is, and how many
heart cells die
At first, the victim
may suffer angina
pectoris
(radiating pain in
the left arm).
One cause of
heart attack:
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Smoking
Nicotine causes
heart to pump faster
Also causes some
arteries to contract
(get smaller)
Puts unneeded
strain on the heart
muscle
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Coronary Bypass
Surgery: segments of leg veins
are grafted between the aorta
and coronary vessels, in order to
bypass a blockage. Two to four
such bypasses may be
performed in a single operation.
e.g. three such grafts would be
known as a “triple-bypass”
operation.

Coronary bypass, donor
heart transplants, and artificial
heart implantation (which don’t
work yet!) are surgical methods
that have been used for the
treatment of heart attacks.

More than 50% of all
deaths in Canada & U.S. are
due to hypertension (high blood
pressure), stroke, and heart
attack.
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Heart Attack: when
portion of heart dies due
to lack of oxygen. At
first, the victim may
suffer angina pectoris
(radiating pain in the left
arm). Death may result
if immediate treatment
not given.
Some more nasty circulatory events:
 Thrombus: a stationary clot attached to an arterial
wall. Slows the flow of blood.
 Embolus: a thrombus that has become dislodged
and moves along with the blood. When the vessel
narrows, the embolus gets stuck and entirely
blocks the flow of blood in a small vessel. This is
called an embolism.

Stroke: when
portion of brain dies
due to lack of
oxygen -- usually
when arteriole
bursts or is blocked
by an embolism.
Strokes usually
cause death or
paralysis.

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