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Circulatory System
Honors Biology
Facilitator: Mr. Lee
Room 320
Objectives:
• Identify the function of the
circulatory system
• Describe the structure and
function of the human heart
• Name the three types of blood
vessels
• Describe the function of the
lymphatic system
Circulatory System
• The Cardiovascular system is
composed of:
– Blood
– Heart
– Blood vessels
• The lymphatic system is composed of:
– Lymph
– Lymph nodes
– Lymph vessels
• The circulatory system is composed of:
– Cardiovascular system
– Lymphatic system
Functions of the Circulatory
System
• Small organisms do not
need a circulatory system.
They can defuse what they
need
• Larger organisms need a
circulatory system
– Most of the cells are not
in direct contact with the
environment
– Functions as a
transportation system
for oxygen, nutrients,
and waste products
The Heart
• The heart is composed
almost entirely of
muscle
• Myocardium is the
thick muscle layer that
surrounds the heart
• The heart is a hollow
organ, about the size of
your fist
• The heart is enclosed
in a protective sac of
tissues called the
pericardium
The Heart…
• The upper chamber that
receives the blood is
called the atrium
• The lower area that pumps
blood out is called the
ventricle
• The heart has four
chambers- two atria and
two ventricles
• The septum divides the
left side of the heart from
the right side
Circulation Through The Heart
• Blood enters the heart
through the right atria,
which pumps it to the
right ventricle
• Right ventricle pumps the
blood to the lungs
• Blood reenters the heart
through the left atria,
which pumps it to the left
ventricle
• Left ventricle pumps the
blood to the body
Heartbeat
• There are two networks
of muscle fibers in the
heart
– One in the atria
– One in the ventricles
• When a single fiber in
either network is
stimulated, all the fibers
are stimulated
Heartbeat…
• Each contraction begins in
the sinoatrial node (SA
node)
– Located in the right
atrium
– Called the pacemaker
• The atrioventricular node
(AV node) sends the
impulse to the ventricles
• There are valves in the
heart that keeps the blood
from flowing backwards
Heartbeat…
• Heartbeat has two
phases:
– Systole:
• Occurs when the
ventricles contract
• Blood pumps out
of the heart
– Diastole:
• Occurs when the
ventricles relax
Blood Vessels
• The oxygen rich blood
leaves the left ventricle of
the heart, passing through
the aorta
• As blood flows through the
circulatory system, it
moves through three types
of blood vessels
– Arteries
– Veins
– Capillaries
Arteries
• Are large blood vessels
that carry blood from the
heart to the body
• Except for the pulmonary
arteries, all arteries carry
oxygen-rich blood
• They have thick walls
(they need because of the
high pressure)
• Arterioles are small
arteries
Veins
• Take the blood from
the capillaries back
to the heart
• Large veins have
valves in them to
help keep the blood
flowing toward the
heart
• Venules are small
veins
Capillaries
• Are the smallest blood
vessels
• The walls of capillaries are
only one cell thick
• They bring nutrients, and
oxygen to the tissues and
absorb carbon dioxide
and waste from them
Circulation Through The Body
• Pulmonary circulation:
– The right side of the
heart pumps blood
from the heart to the
lungs
– In the lungs carbon
dioxide leaves the
blood and oxygen is
absorbed
– The oxygen rich blood
then flows back to the
heart
Circulation Through The Body…
• Systemic circulation:
– The left side of the heart
pumps the oxygen rich
blood to the rest of the
body
– Coronary circulation
supplies blood to the heart
– Renal circulation supplies
blood to the kidneys
Circulatory System
The Lymphatic System
• The lymphatic system is a
network of vessels, nodes,
and organs
• It collects the fluid that is
lost by the blood and
returns it back to the
circulatory system
• Lymph collects in
lymphatic capillaries &
flows to larger lymph
vessels
• Ducts return the lymph to
the circulatory system
Review
• Identify the function of the circulatory
system
– Functions as a transportation
system for oxygen, nutrients, and
waste products
• Describe the structure and
function of the human heart
– The upper chamber that receives the
blood is called the atrium
– The lower area that pumps blood out is
called the ventricle
– The heart pumps blood
Review…
• Name the three types of blood
vessels:
– Arteries
– Veins
– Capillaries
• Describe the role of the lymphatic
system:
– Collects the fluid that is lost by
the blood and returns it back to
the circulatory system
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