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Circulation and
Cardiovascular System
5.2 Transport in
Vertebrates
• All vertebrate animals
have a closed
circulatory system,
which is called a
cardiovascular
system.
• It consists of a heart
in which the atria
receive blood and the
muscular ventricles
pump blood through
the blood vessels.
There are three
kinds of blood
vessels:
Arteries, which
carry blood
away from the
heart
Capillaries,
which exchange
materials with
tissue fluid
Veins, which
return blood to
the heart
There are three kinds of blood vessels:
Arteries, which carry blood away from the heart
Capillaries, which exchange materials with tissue
fluid
Veins, which return blood to the heart
5.3 Transport in
Humans
• The human heart
lies within the
pericardium, a
thick, membranous
sac that secretes a
small quantity of
lubricating liquid.
• The inner
surface of the
heart is lined
with
endocardium, a
membrane
composed of
connective tissue
and endothelial
tissue.
Left side
right side
Internally, the
septum
separates the
heart into a right
side and a left
side.
The heart has
four chambers.
The two upper
thin walled called
atria.
The two lower
chambers are
thick walled
called ventricles,
which pump the
blood.
The heart also
has four valves,
which direct
the flow of
blood and
prevent its
backward
movement.
The two valves
that lie
between the
atria and the
ventricles are
called the
atrioventricular
valves.
The
atrioventricular
valve on the
right side is
called the
tricuspid valve
because it has
three flaps, or
cusps.
The valve on
the left side is
called the
bicuspid (or the
mitral) because
it has two flaps.
The
remaining
two valves
are the
semilunar
valves,
whose flaps
resemble
half moons,
between the
ventricles
and their
attached
vessels.
The
pulmonary
semilunar
valve lies
between the
right ventricle
and the
pulmonary
trunk.
The aortic
semilunar
valve lies
between the
left ventricle
and the aorta.
Path of Blood Through the Heart
The superior
vena cava and
inferior vena
cava carry
blood to the
right atrium.
The right atrium
sends blood
through an
atrioventricular
valve (the
tricuspid valve)
to the right
Ventricle.
The right
ventricle sends
blood through
the
pulmonary
semilunar
valve
into the
pulmonary
trunk
and the two
pulmonary
arteries to the
lungs.
From the
lungs, four
pulmonary
veins,
which
carry
oxygen rich
blood,
enter the
left atrium.
The left atrium
sends blood
through an
atrioventricular
valve
(the bicuspid or
mitral valve)
to the left
ventricle.
The left
ventricle sends
blood through
the aortic
semilunar valve
into the aorta
to the body
The normal average human heart beats
are about 70 times per minute.
The term systole refers to contraction
of the heart chambers, and the word
diastole refers to relaxation of these
chambers.
5.4 Blood, a Transport
Medium
Functions of The blood
1. Transports gases, nutrients, waste products, and
hormones throughout the body.
2. Destroy pathogenic microorganisms.
3. Distributes antibodies that are important in immunity.
4. Maintaining water and pH balance.
5. Regulate body temperature.
6. Carries platelets and factors that ensure clotting and
prevent blood loss.
 In humans, blood has two main portions:
1. The liquid portion, called plasma. Plasma
contains many types of molecules,
including nutrients, wastes, salts, and
proteins.
2. The formed elements, which are of three
types: red blood cells, or erythrocytes ;
white blood cells, or leukocytes ; and
platelets, or thrombocytes.
Red
Blood
Cells
• Red blood cells are small, biconcave disks.
• At maturity they lack a nucleus.
• They contain the the respiratory pigment hemoglobin.
Hemoglobin carries oxygen or carbon dioxide. If there
is an insufficient number of red blood cells, or if the
cells do not have enough hemoglobin, the individual
suffers from anemia and has a tired, run down feeling.
Red
Blood
Cells
• Approximately there are 6 million red blood
cells per cubic millimeter.
• They are manufactured continuously in the red
bone marrow of the skull, the ribs, the
vertebrae, and the ends of the long bones.
• There life span about 120 days.
White blood cells differ from red blood cells in that
they are usually larger, have a nucleus, and they
lack hemoglobin. Defense against disease depends
on the various types of white blood cells.
Neutrophils and monocytes are phagocytic and
are very active during the inflammatory reaction.
Lymphocytes are involved in the development of
immunity to disease.
Eosinophils are important in allergic reactions and
parasitic infections
basophils contain the anticoagulant heparin.
Platelets
• Platelets (thrombocytes) result from fragmentation of
certain large cells, called megakaryocytes, in the red
bone marrow.
• The blood contains 150,000 – 300,000 per mm3.
These formed elements are involved in blood clotting,
or coagulation.