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Circulation. Chapter 23. Facilitating Exchanges. Circulatory systems ensure O2, CO2, nutrients, and wastes get to their specific sites in the body Important for animals to large to survive by diffusion alone - PowerPoint PPT Presentation
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Chapter 23
Facilitating ExchangesCirculatory systems ensure O2, CO2, nutrients,
and wastes get to their specific sites in the bodyImportant for animals to large to survive by
diffusion aloneCnidarians and flatworms have gastrovascular
cavities that serve in digestion and distributionCells can exchange directly with water surrounding
themAnimals with multiple layers of cells need a true
circulatory systemMuscular pump (heart) and circulatory fluid (blood)
Molecular ExchangeO2 and nutrients must
enter cellsCO2 and wastes must
exitLarger organisms have
smaller outer surfaces than innerAll cells must be in an
aqueous environmentFolds and alternate
structures within to facilitate
Circulatory SystemsDirect exchange not between blood and body
cellsCells bathed in interstitial fluid that diffusion
must passOpen circulatory system
Many invertebrates including molluscs and all arthropods
Closed circulatory system Often called a cardiovascular systemEarthworms, squids, octopuses, and vertebrates
Open Circulatory SystemFluid pumped through
open-ended vessels out to cellsNo distinction between
blood and interstitial fluidBody movements
circulate fluid to allow exchange
Heart with pores that allows fluid return and prevents backflow
Respiratory exchange through tracheal system
Cardiovascular SystemBlood confined to vessels
Separate from interstitial fluid
3 kinds of vesselsArteries (red) blood Away
from heartVeins (blue) blood to heartCapillaries transport
blood between the 2Heart with atrium and
ventricle pumps blood to body cells
Arteries to arterioles to capillaries in capillary beds to venules to veins back to heart
Cardiovascular System EvolutionSingle Circuit pumps blood to capillaries
which diffuses to body tissuesDouble circulation pumps blood a second
time after losing pressure in the capillariesPulmonary circuit carries blood between the
heart and lungsSystemic circuit carries blood between the
heart and rest of the body
Single Circuit2 chambered heartBlood to gill
capillaries where pressure is reduced considerably
Flow maintained by organism’s movements
Pressure to low for complex circulation
Double CirculationAmphibians have 3
chambered heartPulmocutaneous circuit
because gas exchange in lungs and across skin
Mixing occurs, but most blood to proper location
Birds and mammals have 4 chambered heartsSupports higher
metabolic ratesDifferent ancestral
evolution so demonstrates convergent evolution
Human Cardiovascular SystemR. ventricle to lungs via
pulmonary arteriesCO2 and O2 exchange
Pulmonary veins back to L. atria to L. ventricle
Through aorta to systemic circuitBranches to upper body
and lower body separately
O2 poor blood back to R. ventricle via S. and I. vena cava
(heart to lungs to heart to body tissue to heart)
Cardiac CycleSequence of pumping
and filling of the heartHeart pumps O2 poor
blood to lungs and O2 rich blood to body
Diastole=entire heart relaxed, ventricles fill with blood
Systole=atria then ventricle contraction
Left stronger because blood to body, but volume is same in both sides=cardiac output
The Beating HeartHeart rate and cardiac rhythm can vary
Age and fitness can effectBoth increase with increasing activity levelsBlood flow controlled by internal valves
Open when pushed from behind and close when pushed from in front
Heart beat sounds = lub-dub AV and semilunar valves’ closing respectively
Heart murmur sound when blood squirts backwards
Beating to its Own Rhythm
Cardiac muscle tissue cycle without neural input Pacemaker sets the contraction rate AV node coordinates, delay to ventricle
Electric shock can be used to reset pacemaker during a heart attackArtificial pacemaker when self system fails
Cardiovascular diseaseDisorders of heart and blood vessels
Heart attack is the damage or death of cardiac tissue from blockage of coronary arteries
Stroke is death of brain tissue from vessel blockage to the head
Most caused by arterosclerosis, or plaque build up, which narrows vessel openingsClots trapped or blood flow is slowed
Anti-inflammatories, angioplasty, and clot-dissolvingTendency to be inherited, but smoking can increase
while exercise and low cholesterol diets can decrease
Blood Vessel FunctionsMust connect with all
body tissuesRemarkable length,
close enough for diffusion to occur
Into interstitial fluid first
Transport blood, nutrients, and wastes to disposal organs
Role in homeostasis and the environment of cells
Blood Vessel StructureCapillaries
Thin walls of single layer epithelial tissueWrapped in a basal lamina
Larger structuresSame epithelial structure, but reinforcedSupported by elastic fiber layer and smooth muscleArteries and arterioles
Thicker and sturdier to accommodate high pressure from heartVeins and venules
Blood to heart at lower pressure One way valves to prevent backflow
Blood FlowBlood pressure is the force blood exerts against
vessel wallsPumped to arteries faster than it can flow =
stretching of vessels, detected as pulsePressure reduces from arteries to capillaries as
resistance from vessel walls decreasesSmaller, but more numerous vesselsRelaxing muscles allows vessel dilation = drop
pressurePressure almost zero at veins
1 way valves and muscle to propel back to heart
Muscle ControlEvery part of body has
blood supply at all timesCertain areas always
full, others are rationed by need
Smooth muscle controls arteriole flow
Precapillary sphincters controlThoroughfare channel is
always openRelaxed vs. contracted
Digestive System
While eating
While exercising
CapillariesOnly vessels that can allow diffusion between blood
and interstitial fluidExchange of substances by diffusion (O2 and CO2),
carried by endocytosis and released by exocytosis, or leaks in wall (water, sugars, and salts)
Direction of movement depends on osmotic and blood pressure differencesArteriole end blood pressure drives fluid out of capillaryVenous end blood pressure drops so osmotic drives into
Fluid that leaves one end generally reenters at other Rest returned via lymphatic system
Blood Composition
RBC CountSet number needed for healthy organismsBroken down and recycled every 3-4 months
Fe returned to bone marrow to form new RBCsLow RBC count = anemia
Excessive tiredness due to lack of O2Most commonly due to low Fe (women more likely); also
blood loss, vitamin and mineral deficiency, or cancersNegative feedback sensitive to O2
Low O2, kidneys produce erthropoietin (EPO) to stimulate bone marrow production of RBCs
Increased RBC production in individuals at high altitudesConnections to athletic training, blood doping, and
artificial EPO injections
Blood Clots
Blood platelets and plasma protein fibrinogen prevent death from minor cuts, enable clotting
Upon damage vessel constricts to reduce blood lossPlatelets adhere to epithelium and form a sticky plug to halt
blood lossClotting factors released from plug to form reinforced patch
Fibrinogen converted to fibrin which traps other blood cells
Stem CellsUnspecialized cells in red marrow of bones
that can differentiate into different blood cellsLymphoid stem cells produce lymphocytes for
immune systemMyeloid stem cells produce RBCs, WBCs, and
plaeletsFormed in early embryo and make all blood
cells for life
LeukemiaCancer of white blood cells or leukocytes
Protect against infections and cancersCells become cancerous, grow uncontrollably, and
crowd RBCs and plateletsSevere anemia and impaired clotting results
Usually fatal unless treatedNot all responsive to radiation and chemoBone marrow transplant, often from a sibling
Lifelong treatment with drugs to avoid rejection of cells Can treat infected marrow to remove most cancer cells and re-
injectUmbilical cord blood has potential, but unsuccessful
so far