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Cardiovascular system (CVS)
CVS consists of the heart and a series of blood
vessels (arteries, veins and capillaries).
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Introduction
A functional cardiovascular system is vital
for
supplying oxygen and nutrients to tissues
and removing
wastes from them.
The heart is the strongest muscle in the
body
The heart must pump blood throughout
the body day & night
The heart is 2 pumps working side by side.
On your right side is the heart that pumps
blood to your lungs where it picks up O2.
1) On your left side is the heart that
pumps this O2-soaked blood out to your
body.
2) Heart pumps 200,000000L blood in a
lifetime
3) Both pumps are divided into 2 spaces
called chambers so your heart is actually
a 4-chambered pumper
4) The 2 sides do not work independently;
they are precisely timed.
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Main functions of the circulatory system
1) Transport and distribute essential
substances to the tissues.
2) Remove metabolic byproducts.
3) Adjustment of oxygen and nutrient
supply in different physiologic states.
4) Regulation of body temperature.
5) Humoral communication.
Cardiovascular system
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The Blood Vessels
The CVS has three types of blood vessels:
Arteries (and arterioles), Capillaries, Veins (and
veinules)
The Arteries and arterioles take blood away from
the heart.
The largest artery is the aorta.
The middle layer of an artery wall consists of
smooth muscle that can constrict to regulate blood
flow and blood pressure.
Arterioles can constrict or dilate, changing blood
pressure
• Capillaries have walls only one cell thick to allow exchange of
gases and nutrients with tissue fluid.
• Capillary beds are present in all regions of the body but not all
capillary beds are open at the same time.
• Contraction of a sphincter muscle closes off a bed and blood can
flow through an arteriovenous shunt that bypasses the capillary
bed.
• Veins
• Venules drain blood from capillaries, then join to form veins that
take blood to the heart.
• Veins have much less smooth muscle and connective tissue than
arteries.
• Veins often have valves that prevent the backward flow of blood
when closed.
• Veins carry about 70% of the body’s blood and act as a reservoir
during hemorrhage.
Figure 15-3: Metarterioles
The
. heart is divided into 4 hollow chambers-2 atria (upper) &
2 ventricles (lower)
Right chambers & valves:
1) right atrium Receives blood from 2 large veins called the
superior vena cava & the inferior vena cava; coronary sinus
also drains blood into the right atrium from the
myocardium
1) Tricuspid valve (3 cusps) guards the atrioventricular orifice
between the right atrium & the right ventricle; it permits
blood to move from the right atrium into the right ventricle
& doesn’t allow it to move in the opposite direction;
Chambers of the heart
 The atria are smaller with thin walls, while the ventricles are larger
with thick walls (much stronger): The left ventricle has thicker wall
than the right because it needs to pump blood to the whole body.
Right ventricle pumps blood a short distance to the
pulmonary trunk (lungs); blood goes to pulmonary trunk
which divides to form the left & right pulmonary arteries
(deoxygenated blood)
1) Pulmonary valve (3 cusps) – guards the base of the
pulmonary trunk; opens as the right ventricle contracts
Left chambers & valves:
1) left atrium receives blood from the lungs through 4
pulmonary veins – 2 from right & 2 from left lungs
2) The blood passes from the left atrium into the left ventricle
through the atrioventricular orifice; bicuspid or mitral
valve guards the left atrioventricular orifice; it prevents
blood from flowing back into the left atrium from the
ventricle when the ventricle contracts
3) The left ventricle pumps blood by way of the aorta (large
artery) into systemic circulation an aortic valve guards the
base of the aorta
The left ventricle’s myocardium is
thicker than the right ventricle’s
myocardium in order to:
contract with a greater pressure
Heart Valves
- Which blood vessel receives
blood from the left ventricle
during systole?
aorta
Heart Valves
Atrioventricular
• Semilunar
valves
1) Tricuspid
1) Aortic
2) Bicuspid or mitral
2) Pulmonary
Prevent blood from
• Prevent blood
flowing back to Right
or left atrium
from flowing
back to Right or
left Ventricle
When aortic pressure is greater
than the ventricular pressure:
the aortic semilunar valve closes
- When aortic pressure is less than
ventricular pressure, this causes:
. the aortic semilunar valve to
open
The Heart: Pumps
1) The right heart pump:
 receives deoxygenated blood from all parts of the
body except the lungs (through superior & inferior
vena cava)
 pumps deoxygenated blood to the lungs
 Pulmonary circulation
The left heart pump:
 receives oxygenated blood from the lungs (through
pulmonary veins)
 pumps oxygenated blood to the rest of the body
 Systemic circulation
Type of circulation
Blood Flow Through Heart
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Blood Flow Through Heart
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Cardiovascular system
Cardiac cycle
- It is the period which passes from the beginning of
one beat until the beginning of the next one.
- The cardiac cycle takes 0.8 sec. when the heart
rate is 75 beats per minute.
- During the cardiac cycle there are certain stages
which are:
1. Stage of filling of the heart with blood.
2. Stage of contraction of the cardiac muscle.
3. Stage of ejection of blood.
4. -stage of relaxation.
The Heartbeat
Each heartbeat is called a cardiac cycle.
When the heart beats, the two atria contract
together, then the two ventricles contract; then
the whole heart relaxes.
Systole:- is the contraction of heart chambers;
Diastole:- is the relaxation of heart chambers
The heart sounds:- Lub-dup,
 Lub:- is due to the closing of the
atrioventricular valves,
Dup:- is due to closing of the semilunar valves.
The tricuspid valve is normally
closed:
while the ventricles are in systole
The Heart: Systole
Systole:It is the contraction of the
entricles.
• When the ventricles contract
 they force the blood into the
great arteries.
 From the left ventricle into the
aorta
 From the right ventricle into the
pulmonary artery.
The increased pressure that result
due to the contraction of the
ventricles is called systolic
pressure.
The Heart: Diastole
Diastole : It is the relaxation of
the ventricles.
When the ventricles relax
 they receive the blood from
the atria.
The decreased pressure due to
the relaxation of the ventricles
is called diastolic pressure.
Cardiac out put
• Is the volume of blood ejected by the left
ventricle per minute
• The cardiac output=C.O.P= S V x HR
S V : Stroke volume: is the volume of blood ejected
by each ventricle per beat. = 75 ml of blood
HR: = Heart rate: is the number of heart beat per
minute = 72 beat/ minute
COP= 75x 72= 5,400
L/ minute
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Cardiovascular system
Stroke volume
- It is the volume of blood pumped by each ventricle per
beat.
- Normally it is about 70 ml/beat.
- The stroke volume of left ventricle = that of right side ‼
- The stroke volume is determined by the venous return.
- Cardiac output (COP)
- It is the amount of the blood pumped by each ventricle
per minute.
- It is about 6 liters / minute at rest.
- It can increase to 25 liters/min. during violent exercise.
Cardiovascular system
Cardiac output = stroke volume x heart
rate.
- So, the COP is increased by an increase
in stroke volume or heart rate or both.
- Factors affecting cardiac output.
1. Venous return.
2. Force of heart contraction.
3. Frequency of the heart rate.
4. Blood pressure.
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- Excessively high heart rate (>180)
can reduce cardiac output
because:
it reduces the time for ventricular
filling which reduces stroke
volume