1. Unit II: Transport Cardiovascular System I
Chapter 18

2. Circulatory System: The Heart
CO2
Circulatory System: The Heart O2
Circulatory system
Cardiovascular system
Two major divisions:
Pulmonary circuit - route to/from lungs
Systemic circuit – route to/from organs
Pulmonary circuit
O2-poor,
CO2-rich
blood
O2-rich,
CO2-poor
blood
Systemic circuit
CO2 O2

3. 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

4. Membranes Surrounding Heart
Pericardial sac (Parietal pericardium)
Fibrous layer
Serous layer
Pericardial cavity
filled with pericardial fluid
Visceral pericardium (a.k.a. epicardium of heart wall)
covers heart surface
Pericardial
cavity Pericardial
sac:
Fibrous
layer
Serous
layer
Epicardium
Myocardium
Endocardium
Epicardium
Pericardial sac

5. (contains serous fluid)
Myocardium
Endocardium
Epicardium
Parietal Pericardium
Dense fibrous layer
Areolar tissue
Mesothelium
Connective tissues
Pericardial cavity
(contains serous fluid)
Fibrous skeleton – network
of collagen and elastic fibers
Cardiac muscle cells
Covers the inner surfaces of
the heart
Endothelium
Outer surface of the
heart; also called
visceral pericardium
The outer wall of the
pericardial cavity
Ventricular
musculature
Atrial
Heart Wall

6. Heart Surface Features
L. Subclavian artery
Brachiocephalic Trunk
L. Common Carotid artery
Aortic arch
Ascending
aorta
Superior vena cava
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

7. Blood Flow Through Heart
Pulmonary
Circulation
veins
Systemic
Circulation

8. Notes on Blood Flow In Pulmonary Circulation:
Deoxygenated blood is carried by arteries
Oxygenated blood is carried by veins
Ascending aorta
Superior vena cava
Right lung
Right
pulmonary
arteries
veins
Inferior vena cava
Descending aorta
Aortic arch
Pulmonary trunk
Left lung
Left
Alveolus
Capillary

9. 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

10. 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

11. Coronary Circulation Great cardiac vein Circumflex branch of LCA
sinus
Right coronary
artery (RCA)
Left marginal branch of LCA
Right marginal
branch of RCA
Left marginal
vein
Posterior
interventricular
branch of RCA
Posterior
interventricular
vein
Left coronary
artery (LCA)
(b) Posterior view
Left auricle
(reflected)
Right
coronary
artery
(RCA)
Circumflex
branch
of LCA
Great cardiac
vein
Right
marginal
branch
of RCA
Anterior
interventricular
branch of LCA
(a) Anterior view

12. 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

13. Cardiac Conduction System
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SA node fires. 2
Excitation spreads through
atrial myocardium.
Right atrium 1 2
Sinoatrial node
(pacemaker)
Left
atrium 3
AV node fires. 2
Purkinje
fibers
Atrioventricular
node 3 4
Excitation spreads down AV
bundle.
Bundle
branches
Atrioventricular
bundle 5
Purkinje fibers distribute
excitation through
ventricular myocardium. 4 5
Purkinje fibers

14. Cardiac Rhythm Systole – Diastole - Sinus rhythm 60 – 100 bpm
Start
Chambers are
relaxed, and the
ventricles are
partially filled with
blood.
Atrial systole
filling the relaxed
ventricles with
Atrial diastole
until the start of
the next cardiac cycle.
As atrial systole
ends, ventricular
systole begins.
Ventricular systole—
first phase:
AV valves close
isovolumetric
contraction
second phase:
ventricular pressure
rises, semilunar
valves open,
ventricular
ejection
Ventricular diastole—
blood flows back
Against the
semilunar valves and forces
them closed.
Blood flows into the
relaxed atria but the
AV valves remain
closed. This is known
as the period of
relaxation.
Ventricular diastole
—All chambers are
relaxed. The ventricles
fill passively to roughly
70% of their final
volume.
800
msec
100
370
Atrial
Cardiac
cycle
systole
diastole
Ventricular
Systole –
Diastole -
Sinus rhythm
60 – 100 bpm
adult at rest is 70 to 80 bpm

15. 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 -

16. Electrocardiogram (ECG or EKG)
P-wave
QRS Complex
T-wave
Cardiac Cycle

17. ECGs, Normal and Abnormal

18. ECGs - Abnormal