Download Lecture 11 - Heart_kz

The Heart
Cardiovascular System, pt. 1 (Chapter 9)
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The cardiovascular
system includes:
• Heart
• Blood vessels
• Blood
• Blood circulation
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What is the heart?
• Also called the cardiac muscle
• A hollow cone-shaped muscular
organ divided into four
chambers
• Straddles the midline within the
thoracic cavity just dorsal to the
sternum
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What is the heart?
The heart is a
pump that
circulates blood
throughout the
body to nourish
and remove waste
from the tissues.
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What is the heart?
The base of the
heart is located
craniodorsally and
the apex points
ventrally and to the
left. The apex is
free within the
pericardium.
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The Structure of the Heart
Covered by a saclike
membrane with 3 layers:
• Pericardium - tough
external layer
• Parietal – Lines the
pericardium
• Visceral - Covers the
surface of the heart
The pericardial space lies
between the inner layers &
contains pericardial fluid
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The Walls of the Heart
The heart is composed of three layers:
• The outer layer (epicardium)
• The middle layer (myocardium)
• The innermost layer (endocardium)
• Lines the chambers and covers
the valves
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The Walls of the Heart
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The Chambers of the Heart
• The heart is divided into a right
and left side.
• The hollow of the heart is
divided into four chambers.
• Atrium - Cranial chambers
• Ventricle - Ventral chambers
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The Chambers of the Heart
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The Chambers of the Heart
• Interatrial septum – Wall that
divides atria into right and left
sides
• Interventricular septum – Wall
divides ventricles into right and
left sides
• No communication between the
two sides
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The Chambers of the Heart
The atria have thin walls and are
receiving chambers. The ventricles
do the pumping and have thick
walls.
Because the left ventricle pumps
blood to the whole body, its walls
are much thicker.
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The right side of the heart receives deoxygenated blood
from the body and sends it to the lungs to be
oxygenated.
The left side
receives
oxygenated
blood from
the lungs and
sends it to
the tissues.
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Heart Valves
Primary valves in the heart:
• Tricuspid – Divides right atrium & ventricle
• Bicuspid (mitral) – Divides left atrium &
ventricle
• Semilunar –
• Prevent backflow from arteries back into
the ventricles
• Located at the bases of the pulmonary
artery & aorta
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Valves within the heart ensure blood flows
in only one direction.
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Cardiac Conduction System
The heart begins pumping
in utero.
Conduction consists of:
• Sinoatrial node (SA
node):
• The “pacemaker”
• This impulse
contracts the atrium
and forces blood into
the ventricles.
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The atrioventricular node (AV node)
This consists of cells that conduct the
electrical impulses down to the next area…
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The atrioventricular bundle (bundle of his)
This continues on as the Purkinje fibers which
stimulate ventricular contraction.
After a brief
rest, the cycle
repeats…
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Purkinje fibers
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Cardiac Nerve Function
The autonomic nervous system
has two divisions with opposite
actions within the heart.
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The Parasympathetic Division
•
Supplies the SA and
AV nodes
• “Rest & digest”
• Slows the heart
rate
• Reduces impulse
conduction
• Constricts the
coronary arteries
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The Sympathetic Division
Acts through the
same nodes to:
• “Fight or flight”
• Increase heart
rate
• Increase impulse
conduction
• Dilate coronary
arteries
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The Cardiac Cycle
•
•
Includes the contraction (systole) and
relaxation (diastole) of the atria and
ventricles
The two atria contract in unison and as they
relax the two ventricles contract
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The Cardiac Cycle
•
•
Atrial contraction
(systole) forces
blood through the
bicuspid and
tricuspid valves into
the ventricles
The semilunar
valves close to
prevent blood from
entering the arteries
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The Cardiac Cycle
• Atrial relaxation (asystole)
moves blood into the atrial
chambers from the pulmonary
veins (left) and the vena cava
(right) while the ventricles
contract.
• When the ventricles contract,
the bicuspid and tricuspid
valves close to prevent
backflow of blood into the
atria.
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Blood Vessels
Animals have three major types of
blood vessels:
• Arteries
• Capillaries
• Veins
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Arteries
Arteries carry oxygenated blood to all
structures of the body.
Arteries are elastic tubes with thick walls
composed of three layers:
• Tunica intima (inner) - endothelium
• Tunica media (middle) - muscle
• Tunica adventitia (outer) - fibrous
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Arterioles, Capillaries and Venules
• Arteries become smaller and smaller,
becoming arterioles.
• Arterioles feed the blood into
capillaries, which distribute blood to
all tissues.
• Blood returns to the venules, where it
passes into veins and returns to the
heart.
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Veins
• Similar to arteries but have thinner and
less elastic walls
• These transport deoxygenated blood
back to the heart.
• Smallest veins (venules) collect blood
from the capillaries before connecting
to larger veins and finally joining the
vena cava to return to the heart.
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Next up…
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