CIRCULATORY SYSTEM
Chapter 13
INTRODUCTION
 Components: heart and vessels (arteries, capillaries, veins)
 Function: supplies nutrients and removes wastes from tissues
CLOSED CIRCUIT
 Humans have a closed circulatory system (blood confined to
vessels).
 The heart pumps blood into large vessels that branch into
smaller ones leading to tissues and organs .
 Arteries  arterioles  capillaries  venules veins
CIRCUITS
 Pulmonary circuit: carries deoxygenated blood to the lungs
 Dumps C02 and picks up O2
 Systemic circuit: carries oxygenated blood to all body cells
 Brings oxygen and removes wastes
Fig13.01
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The systemic circuit delivers oxygen to all
body cells and carries away wastes.
The pulmonary circuit eliminates carbon
dioxide via the lungs and oxygenates the
blood.
Deoxygenated blood
Oxygenated blood
O2
O2
CO2
Oxygenated
blood pumped to
all body tissues
via aorta
O2
CO2
Deoxygenated
blood pumped
to lungs via
pulmonary arteries
CO2
CO2
CO2
O2
CO2
CO2
O2
O2
CO2
O2
Alveolus
O2
Oxygenated blood returns
to heart via pulmonary veins
Deoxygenated blood returns
to heart via venae cavae
Left atrium
Right atrium
Left ventricle
Right ventricle
5
BLOOD VESSELS
 Arteries, arterioles, capillaries, venules, and veins
 Closed tube that carries blood away from the heart, to the
cells, and back again
ARTERIES




Move blood away from heart
Strong, elastic
Can carry high pressure blood
Can dilate or constrict due to smooth muscle contractions
 Contraction causes vasoconstriction
 Relaxation causes vasodilation
 Arteries  arterioles  capillaries
 Largest artery = aorta (diameter of garden hose)
Fig13.17
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Artery
Vein
Lumen
Valve
Endothelium of
tunica interna
Connective tissue
(elastic and collagenous fibers)
Tunica media
Tunica externa
(a)
(b)
8
CAPILLARIES
 Smallest vessels
 Site of gas/fluid exchange
 Connects arterioles to venules
VENULES  VEINS





Return blood to heart
Thinner than arteries, less muscular than arteries
Carries blood under low pressure
Many have valves that prevent backflow of blood
Largest vein = inferior vena cava
THE HEART
SIZE AND LOCATION
 The average adult heart is 14 cm long and 9 cm wide-about
the size of a fist.
 Located in thoracic cavity.
FUNCTIONS OF THE HEART
 Generating blood pressure
 Routing blood
 Heart separates pulmonary and systemic circulations
 Pumps the equivalent of 7000 liters of blood each day
 Ensuring one-way blood flow
 Heart valves ensure one-way flow
 Regulating blood supply
 Changes in contraction rate and force match blood delivery to
changing metabolic needs
COVERINGS OF THE HEART
 Pericardium: double layered sac (visceral and parietal)
Fig13.04
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pericardial
cavity
Parietal
pericardium
Fibrous
pericardium
Endocardium
Myocardium
Coronary
blood vessel
Epicardium
(visceral pericardium)
16
HEART CHAMBERS
 Four chambers
 2 atria
 2 ventricles
 Septum separates
right and left
 Major veins
 Vena cava
 Pulmonary veins
 Major arteries
 Aorta
 Pulmonary trunk
RIGHT VS. LEFT
 Septum separates right and left portions
 Left ventricle has a thicker wall than the right ventricle.
 The right only has to pump blood to lungs (a smaller distance than
the left, which pumps to the entire body).
HEART VALVES
 Allow blood to flow in only one direction
 4 valves:
 Atrioventricular valves = between atria and ventricles
 Bicuspid (mitral) valve (left)
 Tricuspid valve (right)
 Semilunar valves = between ventricle and artery
 Pulmonary semilunar valve
 Aortic semilunar valve
 Open when pushed against by blood, close to prevent
backflow
Fig13.05
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Superior vena cava
Aortic valve
Right pulmonary
artery
Right pulmonary
veins
Right atrium
Opening of coronary
sinus
Tricuspid valve
Right ventricle
Inferior vena cava
Aorta
Left pulmonary
artery
Pulmonary trunk
Left pulmonary
veins
Left atrium
Mitral (bicuspid)
valve
Chordae tendineae
Left ventricle
Papillary muscle
Interventricular
septum
Fig13.06b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pulmonary valve
Aortic
valve
Opening of
left coronary
artery
Tricuspid
valve
Mitral valve
Fibrous skeleton
(b)
Posterior
PATHWAY OF BLOOD FLOW














1 . Sup/Inf Vena Cava
2. Right Atrium
3. Tricuspid Valve
4. Right Ventricle
5. Pulmonary Semilunar Valve
6. Pulmonary arteries
7. Lungs
8. Pulmonary Veins
9. Left Atrium
10. Bicuspid Valve (mitral valve)
11 . Left Ventricle
12. Aortic Semilunar Valve
13. Aorta
14. To the body’s organs
PATHWAY OF BLOOD FLOW
SYSTEMIC V. PULMONARY CIRCUITS
THE CARDIAC CYCLE
 The events associated with one heartbeat (contraction and
relaxation of the 4 heart chambers)
 Vocab:
 Systole: beating/contraction
 Diastole: relaxation
 A single cardiac cycle lasts 0.8 seconds.
 When the atria contract, the ventricles are relaxed (and vice
versa).
EVENTS OF CARDIAC CYCLE
 1 . Atria contract (atrial systole)
 2. Ventricles contract (ventricle systole)
 3. Entire heart relaxes for brief moment ( cardiac diastole)
 During contraction, pressure increases in chamber until blood
is expelled to next destination (valves open/close)
HEART SOUNDS
 “Lubb Dupp”
 Lubb = ventricles contract and AV valves close
 Dupp = ventricles relax and aortic/pulmonary valves close
 *Longer
CARDIAC CONDUCTION SYSTEM
 Specialized Cardiac muscle conducts impulses
 Similar to the depolarization of neurons (Except Ca +2 instead of Na + )
 Impulses first generated by the sinoatrial (SA) node (the
pacemaker)
 SA node located in right atrium
 Cells can reach threshold on their own
 Initiates one impulse after another (70-80 times/min in an adult)
 Sequential stimulation occurs at other cells
CONDUCTION SYSTEM





1.
2.
3.
4.
5.
Sinoatrial (SA) node
Atrioventricular (AV) node
Atrioventricular bundle (AV bundle)
Bundle branches
Purkinje fibers
Fig13.11
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Interatrial septum
Left
bundle
branch
SA node
AV node
AV bundle
Right bundle
branch
Purkinje fibers
Interventricular
septum
33
ELECTROCARDIOGRAM (ECG OR EKG)
 A recording of the electrical changes that occur within the
heart muscle during a cardiac cycle.
EKG
 P wave: depolarization of the atria; contraction of atria
 QRS complex: depolarization of ventricles; contraction of
ventricles (repolarization of atria is hidden )
 Why is this spike larger than P wave?
 T waves: ventricular repolarization; end of EKG
Fig13.14
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a)
1.0
R
Millivolts
.5
T
P
0
Q
–.5
S
0
(b)
200
400
Milliseconds
600
36
RELATE TO NERVOUS SYSTEM
 Which part of the autonomic nervous system will signal heart
rate to increase?
 Decrease?
 These components of the nervous system innervate the SA
Node
BLOOD PRESSURE
 Force of blood against blood vessel walls (usually refers to
pressure in arteries)
 2 numbers (SYSTOLE/DIASTOLE)
 Refers to ventricle systole (contraction) /ventricle diastole(relaxation)
BLOOD PRESSURE
HEART ATTACK
 Myocardial Infarction (MI)
 myocardial = heart muscle tissue
 infarction = tissue death from oxygen starvation
 A blood clot completely blocks a coronary artery (or one of its
branches), cutting of f oxygen supply to that part of the heart.
This results in cardiac tissue death.
ATHEROSCLEROSIS
 Hardening and narrowing of arteries due to buildup of plaque
(cholesterol)