Download Circulation Chpt. 44

Circulation
Chpt. 44
Transportation, cardiac cycle,
evolution of advanced systems
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Oxygen and nutrients
obtained for simple
organisms by diffusion
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Development of multilayer tissues
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Oxygen and nutrients
transported in liquid via
circulatory system
Open – mollusks,
arthropods,
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cnidarians and flatworms
– bodies only 2 cells
thick
no distinction between
circulating fluid and fluid
of body tissues
Called hemolymph
Closed – blood enclosed
in vessels, transport away
and back to a pump
(heart)
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Some invertebrates
(annelids)
Vertebrate Circulatory Systems
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Transportation
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Regulation
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Respiratory, nutritive,
excretory
Hormone transport
Temperature regulation
(vasoconstriction/dilation,
countercurrent heat
exchange)
Protection
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Blood clotting
Immune defense
Blood
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Composed of fluid plasma
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Interstitial fluid originates from
plasma
Matrix in which blood cells and
platelets are suspended
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Metabolites, wastes, hormones
Ions
Proteins – carriers and clotters
Red Blood Cell/Erythrocytes
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Oxygen transport, 45% of blood
Doughnut shaped – increases
surface area
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Hemoglobin – pigment
Develop from stem cells
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Plasma oxygen levels decrease,
bone marrow creates more
Mammalian – no nucleus, removed
as age
White blood cells and platelets
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Immunological defenses
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Less than 1% of blood
Larger, have nuclei, not confined to blood
Several types, each have specific job
Platelets – pieces of megakaryocytes
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Injury – smooth muscle contracts,
constriction
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Platelets accumulate, stick to each other via
fibrin
Blood vessels
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Blood leaves heart via
arteries which branch to
reach organs,
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Finest branches are
arterioles, enters
capillaries
Collected in venules led
to veins
Arteries, veins = same basic
structure
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Innermost = endothelium,
elastic fibers, smooth
muscle, connective tissue
layer
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Too thick to permit
exchange
Capillaries = only
endothelium
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Diffusion, filtration,
transport
Arteries and arterioles
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Transport blood away from
heart
Larger arteries = more
elastic fibers
Smaller = thick smooth
muscle
Vast “tree” = frictional
resistance
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Narrower vessel = more
resistance to flow
Regulated by constriction and
dilation
Precapillary sphincters – limits
Exchange in capillaries
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Sufficient pressure needed to pump against
resistance
Every cell is within 100 micromteres of a
capillary
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Capillaries 1 millimeter long, 8 micro in diameter
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Slightly wider than erythrocyte, must be flexible
Although narrow, number means greatest total area than any
vessel
Blood has more time in capillaries,
releases/pick-up
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Loses pressure and velocity, is under low pressure in veins
Venules and veins
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Venules-veins-heart
Less muscle because
less pressure
Can expand to hold
additional blood
Skeletal muscles can
contract to move
blood back to heart –
venous pump
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One way back to heart,
venous valves
Lymphatic System
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Closed – all vessels connected with another
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Some water and solutes do filter through capillaries to form
interstitial fluid
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Supplies tissue cells with oxygen and nutrients
Exits near arteriolar end where pressure is higher, reenters by osmosis (oncotic pressure)
Lymphatic is open, returns rest of fluid to cardiovascular
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Capillaries, vessels, nodes, organs including spleen and thymus
Activate some white blood cells
Circulatory and respiratory
adapatations
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Large body size and locomotion of animals
possible because of coevolution of
systems
 Needed
more efficient
ways to transport
 Circulation and respiration
linked
Fish heart
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Early chordates had
simple tubular hearts
Gills of fish required
chamber-pump heart
Peristaltic sequence,
heartbeat initiated by
electrical impulse
Gills oxygenate blood,
but looses pressure
developed by heart
contraction
Amphibian/reptilian
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Lungs – blood is oxygenated then
returned to heart
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Two circulations – pulmonary – heart/lungs
Systemic – heart/body
Separates oxygenated from deoxygenated
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Right atrium – receives deoxygenated
from systemic
Left atrium receives oxygenated from
lungs
Little mixing in ventricle
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Oxygenated blood to aorta, major artery
One ventricle with incomplete
separations
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Separation of pulmonary and systemic is
incomplete
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Amphibians can diffuse extra oxygen
Mammalian and Birds
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Four chambered heart
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Two atria and two ventricles
Right atrium receives deoxygenated blood, delivers to
right ventricle, which pumps to blood to lungs
Left atrium receives oxygenated blood from lungs,
delivers to left ventricle, which pumps blood to body
Occur simultaneously – increased efficiency
Closed system – same amount of blood pumped by
both ventricles at same time
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More pressure generated by left ventricle
Sinus venosus – pacemaker
site of heartbeat impulse
Major chamber in fish
 Reduced through amphibians,
reptiles
 Mammals/birds no longer
separate chamber – tissue remains
in right atrium – sinoatrial (SA)
node
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Cardiac cycle
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Two separate pumping
systems within one organ
Two pairs of valves
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Atrioventricular (AV) valves –
guard openings between atria
and ventricles
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Semilunar valves – guard
openings between ventricles
and arteries
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Ttricuspid valve = exit
of right atrium
Bicuspid valve = exit
of left atrium
Pulmonary – right ventricle
to lungs
Aortic – left ventricle to body
Valves open and close during
cardiac cycle
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rest (diastole) and contraction
(systole)
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Blood returns to resting heart (diastole)
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Deoxygenated blood into right atrium
Oxygenated blood into left atrium
Ventricles contract (systole)
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AV valves close (lub), push semilunar valves open
Ventricles relax, semilunar close (dub)
http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html
Veins and arteries
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Pulmonary arteries to
lungs
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Veins back to heart
Aorta
Superior vena cava
Inferior vena cava
Electrical excitation
Heart contains specialized autogenic
depolarizing cells
 Spreads from SA node to atria to ventricles
 Recorded on EKG
 Largest peak is polarization of ventricles
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http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_electrical.html
Blood Flow and Blood Pressure
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Cardiac output has normal
resting rate (5L/minute)
Increases during exercise
(25L/min)
Vasoconstriction/dilation direct
extra blood to important areas
Increased blood pressure =
increase in heart rate or
vasoconstriction
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Can be regulated by hormones
to increase blood volume
Blood Volume Regulation
ADH – antidiuretic, prevent dehydration
 Aldosterone – vasoconstriction
 Atrial Natriuretic Hormone – release Na+
and water
 Nitric Oxide – gas acts as a hormone vasodilation
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