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Circulatory System
Materials once taken into the body must be
transported to body tissues.
·
Some of these materials include
·
Gasses (CO2 & O2)
·
Nutrients
·
Hormones
·
This is done via the circulatory system.
Blood
·
Is a liquid tissue
·
Is composed of approx. 55% Plasma
·
Liquid component of blood
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Contains salts, dissolved nutrients
·
Other 45% composed of 3 types of cells
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Red blood cells
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~5 million RBC'c per cc of blood
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Contains hemoglobin which carries O2 to cells,
also carries CO2 away from cells
·
Each red blood cell can carry 1 billion molecules
of O2
·
Live approx. 120 days, and are made in bone marrow
at a rate of ~2 million/second
Red
Blood Cells
·
White Blood Cells
·
Defend the cell from infection
·
Can engulf bacteria, and produce antibodies to
fight viruses
·
Can move through body tissues
·
Are the target cells of HIV.
·
4000-11000 per cc of blood
White
Blood Cell
·
Platelets
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Are actually fragments of cells
·
Act as "plugs" to form clots surrounding
breaks in the blood vessels
Blood
Types:
·
Determined by presence or absence of certain
proteins in blood.
·
These are A, B, O (absence of
A or B) and Rh
(+,-).
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Your body defenses will attack any protein which
it does not have.
·
Since AB+ have all the proteins, they can accept
all blood types, but can only donate to other AB+ persons. They are Universal Recipients.
·
Since O- have no proteins, they can Only receive
blood from O- persons, but can donate blood to anyone. They are Universal Donors.
Note: You cannot
contract HIV or other blood-borne illnesses through donating blood.
Blood Vessels:
Blood is transported throughout the body via blood
vessels - There are many types.
Classified according to if they carry blood to or
away from the heart.
Away:
·
Arteries
·
Largest blood vessels.
·
Very elastic & thick-Surrounded by layers of
smooth muscle.
·
Generally lead away from heart & carry
oxygenated blood.
·
Lead into Arterioles
·
Arterioles
·
Smaller and thinner than arteries
·
Still lead away from heart
·
Lead to capillaries
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Capillaries
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Small thin vessels - usually only 1 RBC wide
·
Pass next to or near every cell in the body
·
Gas (CO2 & O2) &
nutrient exchange occur here.
Blood
Vessel comparison
Towards
Heart
·
Venules
·
Thin walled vessels collect deoxygenated blood
from capillaries.
·
Not as elastic as arteries, have little muscle
surrounding
·
Pass blood into veins
·
Veins
·
Collect blood from venules
·
Thin walled, contain valves which only allow blood
to go one way.
·
Skeletal muscle "squeeze" the veins to
move blood back to the heart.
Veinous
valves
Circulatory Pathways of Animals:
·
Animals have various types of circulatory systems:
·
2 General categories
o
Open circulatory system
§
Usually involves a fluid coined hemolymph
§
Involves blood leaving the vessels to directly
contact individual cells.
o
Closed circulatory system
§
Blood never leaves vessel structures.
§
Is the vertebrate system.
open
vs. closed circulatory systems
·
Closed circulatory systems have 3 general schemes,
each being increasingly efficient.
o Fish
have a 2 chambered system where blood must pass through 2 capillary beds before
returning to the heart.
§
Lowers blood pressure
o Reptiles
have a 3 chambered system which increases blood flow/pressure since blood must
pass through only 1 capillary bed per cycle.
§
Disadvantage: mixes oxygenated & deoxygenated
blood
o Mammals
have a more efficient system with a 4 chambered heart. Blood pressure is increased and there is no
mixing of blood.
Human Circulation
The Cardiac cycle:
·
Vocab.
o Systole = contraction phase
o Diastole = relaxation phase
1. Contraction
impulse originates from sinoatrial (SA) node
(aka. Pacemaker)
2. Induces
systole of atria which empty contents into ventricles.
3. Atrioventricular (AV) node delays impulse ~0.1
second.
4. Impulse
is carried to the base of ventricles stimulating their contraction
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