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Name ________________________
Block ____
CIRCULATORY SYSTEM (p. 989-
)
Blood is tissue composed of fluid, cells, and fragments of
cells.
a) plasma is fluid portion, which contains proteins,
carries red and white blood cells, platelets, nutrients,
enzymes, hormones, gases, and inorganic salts.
b) red blood cells are round, disk-shaped cells which
carry oxygen to body cells.
c) white blood cells are large and defend the body
against disease.
d) platelets are cell fragments which help blood clot.
The 3 types of blood vessels are arteries, capillaries, and
veins.
“Arteries away, veins to.”
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I. Arteries are large, thick-walled, muscular, elastic
vessels that carry oxygenated blood (looks bright red)
away from the heart.
-blood is under great pressure
-elastic walls of arteries expand and shrink, pushing
on the blood so it can continually flow.
-after arteries branch from heart, they eventually
divide into the smallest blood vessels, called
capillaries.
II. Capillaries are microscopic blood vessels with walls
only 1 cell thick.
*This allows nutrients and gases to diffuse between
the blood and tissues.
-As blood leaves the tissues, capillaries join to
eventually merge into veins.
III. Veins are large blood vessels that carry blood from the
tissues back to the heart. (Blood almost always looks
darker b/c less oxygen)
-because blood in veins isn’t under as much pressure
as the arteries, veins have valves that prevent blood
from flowing backward.
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HEART
-The heart is a large organ, about 12 cm by 8 cm, or the
size of your fist.
-It is made of cardiac muscle cells rich in mitochondria (for
constant energy)
-All mammalian hearts have 4 chambers.
-2 upper chambers are atria and 2 lower chambers are
ventricles
BLOOD PATHWAY
a) Right atrium receives oxygen-poor blood from head
and body through 2 large veins called venae cavae.
b) At same time, left atrium receives oxygen-rich blood
from lungs through 4 pulmonary veins (only veins that
carry blood rich in oxygen—look redish).
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c) After atria have filled with blood, the 2 atria contract,
pushing blood into 2 ventricles.
d) When right ventricle contracts, it pushes oxygen-poor
blood from right ventricle (against gravity) out of the heart
and toward the lungs through the pulmonary arteries
(only arteries that carry blood poor in oxygen—look bluish)
e) At same time, left ventricle pushes oxygen-rich blood
out of the heart through aorta into the arteries. *Aorta is
largest blood vessel in body.
**Before blood goes to rest of the body, it has to enter
the lungs to pick up oxygen.
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TRACE OF BLOOD THROUGH HEART
LEFT ATRIUM
LEFT VENTRICLE
SUPERIOR VENA CAVA
RIGHT ATRIUM RIGHT VENTRICLE
INFERIOR VENA CAVA
PULMONARY ARTERY PULMONARY VEIN LEFT LUNG RIGHT LUNG
*Between atria and ventricles, are 1-way valves that
keep blood from flowing back into the atria.
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HEARTBEAT REGULATION
-Each time the heart beats, surge of blood flows from left
ventricle into aorta and then into arteries, called a pulse.
-Heart rate is set by pacemaker, a group of cells at top of
right atrium.
-pacemaker generates electrical impulse that spreads
over both atria and ventricles, causing them to contract
-Medulla oblongata in brain regulates rate of pacemaker.
BLOOD PRESSURE
-blood pressure is force that blood exerts on vessels of the
body. Pressure rises and falls as the heart contracts and
then relaxes.
-Blood pressure rises sharply when ventricles contract.
High pressure is called systolic pressure.
-Blood pressure then drops as ventricles relax. The lower
pressure is just before ventricles contract again and is
called diastolic pressure.
120 mm Hg –systolic pressure
80 mm Hg –diastolic pressure