Transcript Anatomy of the Heart

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The heart is the organ that supplies blood and oxygen to
all parts of the body. It is about the size of a clenched fist,
weighs about 10.5 ounces and is shaped like a cone. The
heart is located in the chest cavity just posterior to the
breastbone, between the lungs and superior to the
diaphragm. The heart is surrounded by a fluid filled sac
called the pericardium. Blood is pumped away from the
heart through arteries and returns to the heart through
veins. The major artery of the body is the aorta and the
major veins of the body are the vena cava
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The pericardium is the fluid filled sac that
surrounds the heart and the proximal ends of
the aorta, vena cava and the pulmonary
artery
Function:
Keeps the heart contained in the chest cavity.
Prevents the heart from overexpanding when
blood volume increases.
Limits heart motion.
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Blood vessels are intricate networks of tubes
that transport blood throughout the entire
body.
Types of vessels:
Arteries
Veins
Capillaries
Sinusoids
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What is the epicardium?
 The epicardium is the outer layer of the wall
of the heart. It is composed of connective
tissue covered by epithelium. The epicardium
is also known as the visceral pericardium.
 Function:
 Provides an outer protective layer for the
heart
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What is the myocardium?
Myocardium is the muscular middle layer of the
wall of the heart. It is composed of
spontaneously contracting cardiac muscle fibers
which allow the heart to contract.
Function:
Stimulates heart contractions to pump blood
from the ventricles and relaxes the heart to
allow the artria to receive blood.
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What is the endocardium?
The endocardium is the inner layer of the heart.
It consists of epithelial tissue and connective
tissue.
Function:
Lines the inner cavities of the heart, covers heart
valves and is continuous with the inner lining of
blood vessels.
Purkinje fibers are located in the endocardium.
They participate in the contraction of the heart
muscle.
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What are atria?
The heart is divided into four chambers that are
connected by valves. The upper two chambers of
the heart are called the left atrium and the right
atrium.
 Function:
 Right Atrium: Receives blood returning to the
heart from the superior and inferior vena cava.
 Left Atrium: Receives blood returning to the
heart from the pulmonary veins
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What are ventricles?
The heart is divided into four chambers that
are connected by valves. The lower two
chambers of the heart are called the left
ventricle and the right ventricle.
Function:
Right Ventricle: Receives blood from the right
atrium and pumps it to the pulmonary artery.
Left Ventricle: Receives blood from the left
atrium and pumps it to the aorta.
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Valves are flap-like structures that allow
blood to flow in one direction. The heart has
two kinds of valves, atrioventricular and
semilunar valves.
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The atrioventricular valves are thin structures
that are composed of endocardium and
connective tissue. They are located between
the atria and the ventricles
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What is the mitral valve?
Valves are flap-like structures that allow
blood to flow in one direction. The mitral
valve is located between the left atrium and
the left ventricle.
Function:
Prevents the back flow of blood as it is
pumped from the left atrium to the left
ventricle.
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What is the tricuspid valve?
Valves are flap-like structures that allow
blood to flow in one direction. The tricuspid
valve is located between the right atrium and
the right ventricle.
Function:
Prevents the back flow of blood as it is
pumped from the right atrium to the right
ventricle.
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The semilunar valves are flaps of
endocardium and connective tissue
reinforced by fibers which prevent the valves
from turning inside out. They are shaped like
a half moon, hence the name semilunar
(semi-, -lunar). The semilunar valves are
located between the aorta and the left
ventricle and between the pulmonary artery
and the right ventricle.
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What is the aortic valve?
Valves are flap-like structures that allow
blood to flow in one direction. The aortic
valve is located between the left ventricle and
the aorta.
Function:
Prevents the back flow of blood as it is
pumped from the left ventricle to the aorta.
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What is the pulmonary valve?
Valves are flap-like structures that allow
blood to flow in one direction. The pulmonary
valve is located between the right ventricle
and the pulmonary artery.
Function:
Prevents the back flow of blood as it is
pumped from the right ventricle to the
pulmonary artery
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What is the sinoatrial node?
The sinoatrial (SA) node is a section of nodal tissue
that is located in the upper wall of the right atrium.
The SA node is also referred to as the pacemaker of
the heart.
 Function:
 Sets the rate of contraction for the heart.
 Spontaneously contracts and generates nerve
impulses that travel throughout the heart wall
causing both atria to contract.
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The atrioventricular bundle is a bundle of
fibers that are located within the septum of
the heart.
Function:
Carries cardiac impulses down the septum to
the ventricles via the Purkinje fibers
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What is the atrioventricular node?
The atrioventricular (AV) node is a section of nodal
tissue that lies on the right side of the partition that
divides the atria, near the bottom of the right
atrium.
 Function:
 Delays cardiac impulses from the sinoatrial node to
allow the atria to contract and empty their contents
first.
 Relays cardiac impulses to the atrioventricular
bundle
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What are Purkinje fibers?
Purkinje fibers are fiber branches that extend
from the atrioventricular bundle.
Function:
Relays cardiac impulses to the ventricular
cells causing the ventricles to contract
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Cardiac Cycle
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The cardiac cycle is the sequence
of events that occur when the
heart beats. There are two phases
of this cycle:
Diastole - Ventricles are relaxed.
Systole - Ventricles contract.
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Cardiac Cycle
Image courtesy of MedValet
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The cardiac cycle is the sequence of events
that occur when the heart beats. There are
two phases of this cycle:
Diastole - Ventricles are relaxed.
Systole - Ventricles contract
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Early Diastole
Ventricles relax.
Semilunar valves close.
Atrioventricular valves open.
Ventricles fill with blood.
Mid Diastole
Atria and Ventricles are relaxed.
Semilunar valves are closed.
Atrioventricular valves are open.
Ventricles continue to fill with
blood.
Late Diastole
SA node contracts.
Atria contract.
Ventricles fill with more blood.
Contraction reaches AV node.
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The cardiac cycle is the sequence of events
that occur when the heart beats. There are
two phases of this cycle:
Diastole - Ventricles are relaxed.
Systole - Ventricles contract
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Cardiac Cycle
Systole Phase
Systol
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Contraction passes from AV node to
Purkinje fibers and ventricular cells.
Ventricles contract.
Atrioventricular valves close.
Semilunar valves open.
Blood is pumped from the ventricles
to the arteries.
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Arteries
Capillaries
Veins
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Arteries are vessels that carry blood away from the heart.
The aorta is the largest artery in the body. It arises from the
left ventricle of the heart, forms an arch, then extends down
to the abdomen where it branches off into two smaller
arteries.
 Function:
 Carries and distributes oxygen rich blood to all arteries. Most
major arteries branch off from the aorta, with the exception
of the main pulmonary artery.
 Branches:
 (1) Ascending Aorta - Extends from the left ventricle of the
heart.
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The coronary arteries are the first blood
vessels that branch off from the ascending
aorta.
Function:
Carry oxygenated and nutrient filled blood to
the heart muscle
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Function:
Carries de-oxygenated blood from the right
ventricle to the lungs
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Function:
Brings oxygenated blood from the lungs to
the left atrium
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Function:
Superior Vena Cava: Brings de-oxygenated
blood from the head, neck, arm and chest
regions of the body to the right atrium.
Inferior Vena Cava: Brings de-oxygenated
blood from the lower body regions to the
right atrium.
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