Download Unit II – Transport Cardiovascular System

Unit II: Transport
Cardiovascular System I
Chapter 18
CO2
Circulatory System: The Heart
O2
• Circulatory system
Pulmonary circuit
• Cardiovascular system
O2-poor,
CO2-rich
blood
O2-rich,
CO2-poor
blood
Two major divisions:
• Pulmonary circuit - route to/from lungs
Systemic circuit
• Systemic circuit – route to/from organs
CO2
O2
Position, Size, and Shape
• Located in mediastinum, between
lungs
• Base • Apex • 3.5 in. wide at base,
5 in. from base to apex and 2.5 in.
anterior to posterior; weighs 10 oz
Membranes Surrounding Heart
• Pericardial sac (Parietal
pericardium)
– Fibrous layer
– Serous layer
• Pericardial cavity
Epicardium
– filled with pericardial
fluid
Pericardial
cavity
Pericardial
sac:
Fibrous
layer
Serous
layer
Myocardium
Endocardium
Epicardium
Pericardial sac
• Visceral pericardium (a.k.a.
epicardium of heart wall)
– covers heart surface
Heart Wall
Parietal Pericardium
The outer wall of the
pericardial cavity
Atrial
musculature
Pericardial cavity
(contains serous fluid)
Ventricular
musculature
Dense fibrous layer
Areolar tissue
Mesothelium
Myocardium
Fibrous skeleton – network
of collagen and elastic fibers
Cardiac muscle cells
Epicardium
Outer surface of the
heart; also called
visceral pericardium
Mesothelium
Areolar tissue
Endocardium
Covers the inner surfaces of
the heart
Endothelium
Areolar tissue
Connective tissues
Superior vena cava
L. Subclavian
artery
L. Common
Carotid artery
Aortic arch
Brachiocephalic
Trunk
Heart Surface Features
Ascending
aorta
Left pulmonary
artery
Branches of the
right pulmonary
artery
Pulmonary trunk
Left pulmonary
veins
Right pulmonary
veins
Left auricle
Right auricle
Right atrium
Coronary sulcus
Anterior
interventricular
sulcus
Right ventricle
Inferior vena cava
Left ventricle
Apex of heart
(a) Anterior view
Blood Flow Through Heart
Pulmonary
Circulation
veins
Systemic
Circulation
Notes on Blood Flow
In Pulmonary Circulation:
• Deoxygenated blood is carried by arteries
• Oxygenated blood is carried by veins
Aortic arch
Ascending aorta
Pulmonary trunk
Superior vena cava
Left lung
Left
pulmonary
arteries
Left
pulmonary
veins
Right lung
Right
pulmonary
arteries
Right
pulmonary
veins
Alveolus
Capillary
Inferior vena cava
Descending aorta
Coronary Circulation
Arterial Supply
• Left coronary artery (LCA)
– anterior interventricular branch
• interventricular septum and anterior walls of both ventricles
– circumflex branch
• left atrium and posterior wall of left ventricle
• Right coronary artery (RCA)
– marginal branch
• lateral right atrium and ventricle
– posterior interventricular branch
• interventricular septum and posterior walls of both ventricles
Coronary Circulation
Venous Supply
• 10% drains directly into right ventricle via anterior cardiac veins
• 90% returns to right atrium via:
– great cardiac vein
– middle cardiac vein (posterior interventricular)
– coronary sinus
Coronary Circulation
Great cardiac
vein
Circumflex
branch of
LCA
Coronary
sinus
Left marginal
branch of LCA
Left marginal
vein
Right
coronary
artery
(RCA)
Right
marginal
branch
of RCA
(a) Anterior view
Left coronary
artery (LCA)
Left auricle
(reflected)
Circumflex
branch
of LCA
Great cardiac
vein
Anterior
interventricular
branch of LCA
(b) Posterior view
Right coronary
artery (RCA)
Right marginal
branch of RCA
Posterior
interventricular
branch of RCA
Posterior
interventricular
vein
Cardiac Muscle Cells
• Striated, branched cells, one central nucleus
• Intercalated discs join cardiocytes
– interdigitating folds
– mechanical junctions
– electrical junctions
• Metabolism
– Aerobic respiration
– Resistant to fatigue
– Autorhythmic
Cardiac Conduction System
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1
2
Right atrium
2
1
Sinoatrial node
(pacemaker)
2
Atrioventricular
node
Atrioventricular
bundle
Purkinje fibers
3
4
5
SA node fires.
Excitation spreads through
atrial myocardium.
Left
atrium
3
Purkinje
fibers
4
Excitation spreads down AV
bundle.
Bundle
branches
5
Purkinje fibers distribute
excitation through
ventricular myocardium.
AV node fires.
Cardiac Rhythm
Start
• Systole –
• Diastole • Sinus rhythm
– 60 – 100 bpm
– adult at rest is
70 to 80 bpm
Chambers are
relaxed, and the
ventricles are
partially filled with
blood.
800 0
msecmsec
Atrial systole
filling the relaxed
ventricles with
blood.
As atrial systole
ends, ventricular
systole begins.
100
msec
Cardiac
cycle
Ventricular diastole
—All chambers are
relaxed. The ventricles
fill passively to roughly
70% of their final
volume.
Blood flows into the
relaxed atria but the
AV valves remain
closed. This is known
as the period of
isovolumetric
relaxation.
Atrial diastole
until the start of
the next cardiac cycle.
370
msec
Ventricular diastole—
blood flows back
Against the
semilunar valves and forces
them closed.
Ventricular systole—
first phase:
AV valves close
isovolumetric
contraction
Ventricular systole—
second phase:
ventricular pressure
rises, semilunar
valves open,
ventricular
ejection
Abnormal Cardiac Rhythms
• Arrhythmia –
– heart block: failure of conduction system
• Premature ventricular contraction (PVC)
– caused by hypoxia, electrolyte imbalance, stimulants, stress, etc.
• Ectopic foci – nodal rhythm - 40 to 50 bpm
• Fibrillation -
Electrocardiogram (ECG or EKG)
• P-wave
• QRS Complex
• T-wave
• Cardiac Cycle
ECGs, Normal and Abnormal
ECGs - Abnormal