Transcript The Cardiovascular System - Elmwood Park Memorial High School

The
Cardiovascular
System
The Cardiovascular System
• major function - transportation.
• Uses blood as the vehicle
• the system carries:
–Oxygen
– nutrients
– cell wastes
– hormones
– and other substances vital for body homeostasis
The Heart
• The heart is located in the bony thorax
– its apex is pointed towards the left hip and rests
on the diaphragm.
• Your heart is roughly the size of your fist.
• Divided into four chambers
Heart – Coverings
• The heart is enclosed by a double sac called the
pericardium.
• Parietal Pericardium- loose outer layer, reinforced
with fibrous tissue that helps protect the heart and
anchor it to surrounding structures.
• Visceral Pericardium – tightly hugs the external
surface of the heart and is continuous with the
heart wall.
Heart - Walls
• The heart walls are composed of three layers:
1. Visceral Pericardium (epicardium)
2. Myocardium – thick bundles of cardiac muscle twisted
into ring-like arrangements (the contracting part)
3. Endocardium- thin sheet of epithelium that lines the
chambers and is continuous with the blood vessels
entering and leaving the heart.
Heart - Chambers
• The heart has 4 hollow chambers.
• The superior two “receiving” chambers are
called atria.
• The inferior two “discharging” chambers are
called ventricles.
Heart – Great Vessels
• Blood coming and going to and from the heart
travels in blood vessels.
• Veins carry blood away from the tissues
towards the heart.
• Arteries carry blood away from the heart.
Key Great Vessels
• Superior and Inferior Vena Cava – supply the
right atrium.
• Pulmonary Trunk (with R and L pulmonary
arteries)– drain the right ventricle.
• R and L Pulmonary Veins – supply the left atrium.
• Aorta – drains the left ventricle.
Blood Flow
• The right side of the heart receives oxygen
poor blood from the veins and pumps it
through the pulmonary arteries to the lungs.
• Now oxygen rich blood returns to the left side
of the heart through the pulmonary veins.
• This is Pulmonary Circulation
Blood Flow
• Oxygen rich blood in the left side of the heart
is pumped into the aorta and travels to all the
body’s tissues in systemic arteries.
• It returns to the heart through systemic veins,
and eventually the superior and inferior vena
cava.
• This is Systemic Circulation
Valves
• 4 valves which allow the blood to flow in only
one direction through the chambers.
Atrioventricular Valves
• AV valves are between the atria and ventricles
chambers on either side.
• They prevent backflow into the atria when the
ventricles contract.
• Left AV valve – bicuspid valve
• Right AV valve – tricuspid valve
Semilunar Valves
• The semilunar valves guard the bases of the two
large arteries leaving the ventricular chambers.
• Pulmonary Semilunar Valve – R ventricle to
pulmonary trunk
• Aortic Semilunar Valve – L ventricle to aorta
Coronary Arteries
• The blood supply that nourishes and oxygenates
the heart is provided by the coronary arteries
which stem from base of the aorta and encircle the
heart.
• These arteries fill when the heart is relaxed, and
are compressed when the heart is contracting.
Angina and Heart Attacks
• If the heart beats at a very rapid pace it may
receive inadequate blood supply
• deprives the heart of oxygen and causing chest
pain called angina.
• If angina persists heart cells may die causing a
myocardial infarction or “coronary”, otherwise
known as a heart attack.
Heartbeat
• Unlike skeletal muscle cells, cardiac muscle cells
contract independent of nerve stimulation in a
regular and continuous way.
• However, different areas of the heart beat in
different rhythms.
(Atria 60 bpm, Ventricles20-40 bpm)
Controlling the Heartbeat
• Autonomic nervous system - can increase or
decrease heart rate.
• Intrinsic Conduction System or Nodal System–
causes heart depolarization in one direction (atria
ventricle) and enforces the heart to beat at a
unified contraction rate of approximately 75 beats
per min.
Intrinsic Conduction System
• This nodal system is composed of special
tissue found nowhere else in the body. It is
like a cross between muscle and nervous
tissue.
• One of the most important parts is the
sinoatrial node, located in the right atrium
whose job it is to start each beat and set the
pace for the whole heart. (the pacemaker)
Intrinsic Conduction System
• Form the SA node, the impulse spreads through
the atria to the…
• Atrioventricular (AV) Node where the impulse is
delayed briefly to allow the atria to finish
contracting.
• It then passes rapidly through the AV bundle, the
bundle branches, and the Purkinje fibers
resulting in a contraction of the ventricles starting
from the apex and moving toward the atria.
The Cardiac Cycle
• In a healthy heart the Atria contract together,
then as they start they start to relax, the
ventricles contract.
• Systole- means contraction
• Diastole – means relaxation
• Because the ventricles do the pumping, these
terms refer to the condition of the ventricle.
The Cardiac Cycle
Cardiac Cycle
• Mid to Late Diastole – the heart is completely
relaxed. The AV valves are open and the
ventricles are filling. Then the atria contract.
Cardiac Cycle
• Ventricular Systole – Ventricle contraction
begins and the AV valves close. Pressure builds
in the ventricles, forcing open the semilunar
valves, and blood is pumped out of the
ventricles.
• During this time the atria are relaxed and
filling with blood.
Cardiac Cycle
• Early Diastole- The ventricles relax and the
semilunar valves snap shut. When ventricular
pressure drops below atrium pressure the AV
valves open and blood again begins to fill the
ventricles.
Listening to your heart…
• When you listen to your heart through a
stethoscope you should be able to hear 2
distinct sounds:
• Lub – the first is the longer and louder closing
of the AV valves.
• Dup- the second is the short and sharp closing
of the semilunar valves.
lub dup lub dup lub dup lub dup
Blood Vessels
• From the heart arteries smaller and
smaller arteries arterioles capillary beds
which feed the tissues and are drained by 
venules which empty into  veins  which
empty into the great veins serving the heart.
Blood Vessels
• Blood is moved through the circulatory system
by the elastic expansion and constriction of
the blood vessels.
• Vasoconstriction – reduction in the diameter
of a blood vessel.
• Vasodilation – enlargement of blood vessel
diameter.
Structure of Blood Vessels
Arteries vs. Veins vs. Capillaries
• Artery walls are much thicker than vein walls
because arteries are closer to the pumping
action of the heart and must be able to
expand and recoil with that pumping action.
Arteries vs. Veins vs. Capillaries
• The pressure in veins tends to be low at all
times, so they have thinner walls. Veins have
larger lumen and some have valves to prevent
back flow.
Arteries vs. Veins vs. Capillaries
• Capillary walls are only one cell layer thick and
therefore allow for easy exchanges between
blood and tissues.
Circulation
• The alternating expansion and recoil of an
artery that occurs with each beat of the left
ventricle creates a wave of pressure called a
pulse.
Blood Pressure
• Blood pressure is the pressure the blood
exerts against the inner walls of the blood
vessels.
• Continual blood flow depends on the
stretchiness of the arteries and their ability to
recoil and keep pressure on the blood.
Measuring Blood Pressure
• Two arterial blood pressure measurements
are made.
Systolic Pressure – the pressure in the arteries
at the peak of ventricular contraction
Diastolic Pressure – the pressure when the
ventricles are relaxing
Blood Pressure
• Blood pressure depends on two main factors,
- Cardiac output
- Peripheral resistance
• Anything that increases either of these
factors, raises blood pressure.
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Automatic nervous system
Renal factors
Temperature
Chemicals
Diet
Measuring Blood Pressure