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The Cardiovascular System
Unit 3 (Ch.15)
Structure of the Heart
• About as big as your fist.
• Located within your thoracic cavity.
– In the mediastinum
– Sits on the diaphragm
• 14 cm long by 9 cm wide.
Coverings of the Heart
• Pericardium encloses the heart
• Layers:
1.fibrous
2.visceral
3.parietal pericardium
Wall of the Heart
• The epicardium protects the heart by
reducing friction.
• The myocardium pumps blood out of the
heart chambers.
• The endocardium is continuous with the
inner linings of blood vessels attached to the
heart.
Heart Chambers and Valves
• The upper chambers, atria, receive blood
returning to the heart.
• The lower chambers, ventricles, receive
blood from the atria and contract to force
blood out of the heart in the arteries.
• The triscuspid valve permits blood to move
from the right atrium to the right ventricle.
• The pulmonary valve allows blood to leave
the right ventricle and prevents backflow
into the ventricular chamber.
• The mitral valve permits blood to move
from the left atrium to the left ventricle.
• The aortic valve allows blood to move
from the left ventricle into the aorta.
Path of Blood Through the Heart
(fig.15.40 on pg. 591)
• Blood enters the right atrium from the venae cavae
and coronary sinus.
• passes though the tricuspid valve
• enters the chamber of the right ventricle, though
the pulmonary valve,
• into the pulmonary arteries,
• then the capillaries,
• back to the pulmonary veins,
• Out the left ventricle into the aorta
Coronary arteries
• Supply blood to the tissues of the heart.
Systol and a Diastole
• Systol- when atria contract (atrial systol)
• Diastole-when ventricle relaxes.
(ventricular diastole)
• = Cardiac cycle – complete heartbeat.
Heart Sounds
• Lubb-dupp or lubb-dubb
Electrocardiogram (ECG)
• Records electrical changes in the
myocardium during a cardiac cycle.
• Pattern contains several waves
– P wave
– QRS wave
– T waves
*Physical exercise, body temperature, and concentration of various
ions affect heartbeat.
Arteries and Arterioles
• Arteries – adapted to carry blood under high
pressure away from the heart.
• A small branch of an artery that
communicates with a capillary network =
arteriole.
Vasoconstriction and Vasodilation
• Vasoconstriction = a decrease in the
diameter of a blood vessel.
• Vasodilation = an increase in the diameter
of a blood vessel.
Capillaries
• A small blood vessel that connects an
arteriole and a venule. (linchpin between arteries
and veins)
Veins and Venules
• Veins are vessels that carry blood toward
the heart.
• Venules are vessels that carries blood from
capillaries to a vein.
Systolic and Diastolic Pressure
• Systolic pressure-arterial blood pressure
during the systolic phase of the cardiac
cycle.
• Diastolic pressure- lowest arterial blood
pressure reaching during diastolic phase of
cardiac phase.
Hypertension
• High blood pressure.
Next Time
• Paths of Circulation
– Pulmonary circuit
– Systemic circuit
• Arterial System
• Venous System
• Life Span Changes