Transcript Cardiovascular System

Cardiovascular System
Introduction
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The heart pumps 7000 liters of blood a
day
Contracts 2.5 billion times in a lifetime
This system brings oxygen and nutrients
to all body cells and removes wastes
Functioning system is vital for survival
Structure of the Heart
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Heart is hollow, cone-shaped, muscular
pump in the thoracic cavity and resting on
the diaphragm.
Heart size varies with body size. Average
adult's heart is 14 cm long and 9 cm wide
The pericardium encloses the heart
The pericardial cavity contains serous fluid
to reduce friction between the pericardial
membranes
Walls of the Heart
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Three distinct layers of the heart wall
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Epicardium protects the heart by
reducing friction.
Myocardium middle layer consists of
cardiac muscle tissue to pump blood out
of the heart chambers
The inner endocardium contains blood
vessels and muscle fibers
Heart Chambers and Valves
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Divided into four hollow chambers
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Atria are the upper chambers; thin walls that receive
blood
Ventricles are the lower chambers that receive blood from
the atria and contract to force blood out
 The right ventricle has a thinner wall and pumps
blood to lungs
 The left ventricle has a thicker wall and pumps
blood to other parts of the body
Septum wall separates the atrium and ventricle on right
side from the left side
Atrioventricular valves (AV valve), is a tricuspid valve on
the right; bicuspid valve on the left; ensures one-way
blood flow between atria and ventricles
Semilunar valves: the pulmonary valve prevents backflow
into the right ventricle and aortic valve prevents backflow
in the left ventricle.
Path of Blood through Heart
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Blood low in oxygen and high in CO2 enters right atrium through the
superior and inferior vena cava.
The right atrial wall contracts pushing blood through the tricuspid
valve entering the right ventricle
The right ventricle contracts, the tricuspid valve closes, blood moves
through pulmonary valve into pulmonary arteries towards the lungs.
Gas exchange occurs in the lungs and the blood returns to the heart
through the pulmonary veins to the left atrium.
The left atrium contracts, pushing blood through the bicuspid valve
into the left ventricle.
The left ventricle contracts, closing the bicuspid valve and pushing
blood through the aortic valve into the aorta to the body.
Heart Actions
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Contraction of walls is systole while
relaxation is diastole
Atrial systole (contraction) while
ventricular diastole (relaxation) and vice
versa
The atria and ventricles both relax for a
brief interval.
This series constitutes a heartbeat or
cardiac cycle
Heart Actions
Cardiac Cycle
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Pressure within the heart chamber rises and
falls, controlling the blood flow.
The heartbeat heard through a stethoscope
sounds like “lubb-dupp” These sounds are due
to the vibrations in the heart tissue associated
with the closing of the valves
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Lubb is ventricular contraction and AV valves
closing
Dupp is ventricular relaxation and pulmonary
and aortic valves closing.
Cardiac Conduction System
The sinoatrial node (SA node) is a mass of
specialized cardiac tissue beneath the epicardium.
On the right atrium near the opening of the superior
vena cava.
– This initiates impulses that spread to
stimulate muscle contraction in atria
– Rhythmic, one pulse after another; 70-80
times/minute in adults
– The Pacemaker
ខ The atrioventricular nodes (AV node) is located in
the septum and helps in contraction of ventricles
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Electrocardiogram
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ECG
Recording of the electrical charges during
the cardiac cycle
The SA node triggers an impulse (P wave)
The AV node triggers the QRS complex
Used to assess the heart's ability to
conduct impulses
Show the time period of impulse travel
between nodes
Blood Vessels
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Closed circuit of tubes that carries blood
Includes:
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Arteries
Arterioles
Capillaries
Venules
Veins
Arteries and Arterioles
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Arteries carry blood away from the heart under high
pressure. These are subdivided into thinner tubes called
arterioles.
Vasoconstriction is the contraction of smooth
muscles in the vessel , reducing the diameter
Vasodilation is the relaxation of smooth muscle,
increasing the diameter.
Diameter influence blood flow and blood
pressure
Capillaries
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Smallest-diameter blood vessels
Connect smallest arterioles to the venules
Substances are exchanged within tissues with
capillaries
Diffusion, filtration, or osmosis occurs to/from
capillaries from/to tissues
Veins and Venules
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Venules are microscopic vessels off
of capillaries and merge to form veins
Veins carry blood back to the atria
Veins also function as blood
reservoirs
Blood Pressure
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Force of blood exerted against the inner
walls of blood vessels
Commonly refers to arteries
Systolic Pressure – max pressure during
ventricular contraction
Diastolic pressure – lowest pressure
remaining in arteries before next
ventricular contraction
Factors Influencing BP
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Heart Action
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How much blood enters the arterial system
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Volume of blood from left ventricle with each contraction is stroke volume
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Volume discharged from left ventricle per minute is cardiac output
Blood Volume
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Sum of formed elements and plasma volume in vascular system
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Usually about 5 L for adults
Peripheral Resistance
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Friction between blood and the walls of blood vessels, hindering blood
flow
Blood Viscosity
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Ease at which a fluids molecules flow past one another
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The greater the viscosity, the greater the resistance to blood flow