Download Heart

Closed and Open Circulatory Systems
Closed system: Blood never leaves vessels.
Lymph travels
through closed
lymph vessels
Blood travels
through closed
blood vessels
Single heart
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The Evolution of the Vertebrate Circulatory System
Fish
1 circuit
2-chambered heart
Gills
V
A
Frogs
2 circuits
3-chambered heart
2 circuits
“5-chambered” heart
Lung
Lung
A
A
A
V
Body
Turtles, lizards
Body
A
V
Body
Crocodiles
2 circuits
4-chambered heart
Birds
2 circuits
2 circuits
4-chambered heart 4-chambered heart
Lung
A
Mammals
A
V V
Body
Lung
Lung
A
A
A
A
V V
V V
Body
Body
A  Atrium
V  Ventricle
Ventricle divided into chambers
Three-chambered heart
Two circulatory loops
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
The Human Heart
Pulmonary circulation
1. Blood returns to heart
from body, enters right
atrium.
Aorta
Superior
vena cava
Pulmonary
artery
6
3
2. Blood enters
right ventricle.
Pulmonary
vein
3. Blood is pumped
from right ventricle
to lungs.
4
Right
atrium
Left
atrium
1
Systemic circulation
Atrioventricular
valve
Atrioventricular
4. Blood returns to left valve
atrium from lungs.
5
5. Blood enters left
ventricle.
Inferior
vena cava
2
6. Blood is pumped from
left ventricle to body.
Right
ventricle
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Left
ventricle
Semilunar
valves
Partial Pressures of Gases Vary throughout the Human Circulatory System
Tissues
PO2 40 mm Hg
PCO2 45 mm Hg
Blood leaving
tissue capillaries
PO2 40 mm Hg
PCO2 45 mm Hg
Blood entering
tissue capillaries
PO2 140 mm Hg
PCO2 40 mm Hg
Systemic
circulation
Inhaled air
PO2 160 mm Hg
PCO2 0.3 mm Hg
Exhaled air
PO2 120 mm Hg
PCO2 27 mm Hg
Pulmonary Pulmonary
Aorta artery
vein
Pulmonary circulation
Venae
cavae
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
Blood entering
alveolar
capillaries
PO2 40 mm Hg
PCO2 45 mm Hg Alveoli of lungs
PO2 104 mm Hg
PCO2 40 mm Hg
Blood leaving
alveolar
capillaries
PO2 104 mm Hg
PCO2 40 mm Hg
Blood Pressure Changes during the Cardiac Cycle
Cardiac cycle
Ventricular systole
Ventricular diastole
Systolic blood pressure
Aortic valve
opens
Diastolic blood pressure
Aortic valves
closes
Atrioventricular
valves close
Atrioventricular
valves open
Ventricular
pressure
Atrial pressure
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
EKGs Record Electrical Events Associated with Cardiac Muscle Contraction
SA node
activates
atria
AV
node
delay
Electrical Electrical activity
in ventricles
activity
in atria
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
Ventricles recover
Patterns in Blood Pressure and Blood Flow
• Blood pressure is the force that blood exerts on the walls of
arteries, capillaries, and veins.
• Blood pressure drops dramatically as blood moves through the
capillaries, because the total cross-sectional area of blood vessels
in the circulatory system increases greatly.
• The drop in blood pressure decreases the rate of blood flow to
allow sufficient time for gases, nutrients, and wastes to diffuse
between tissues and blood in the capillaries.
• Falling blood pressure is detected by baroreceptors in the walls
of the heart and the major arteries.
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
Blood Pressure Drops Dramatically in the Circulatory System
From heart
Capillaries
Velocity
Total area
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
Return to heart
Patterns in Blood Pressure and Blood Flow
•
When baroreceptors detect a major decrease in blood pressure,
they trigger electrical signals that change the heart’s output and
vessel diameter:
(1)Cardiac output is increased by an increase in both heart rate
and the amount of blood pushed out by the ventricles.
(2)Arterioles serving the capillaries of noncritical tissues such
as the skin and intestines are constricted to divert blood to more
critical organs.
(3)The veins are constricted, shifting blood volume toward the
heart and arteries to maintain blood pressure and flow to vital
organs.
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley