EXTERNAL ENVIRONMENT
MouthFood
CO2 O2
ANIMAL
Digestivesystem
Respiratorysystem
Circulatorysystem
Urinarysystem
HeartInterstitialfluid
Bodycells
Intestine
Anus
Unabsorbedmatter (feces)
Metabolic wasteproducts (urine)
Nutrients
Blo
od
respiratory system exchanges gases between the external environment and blood.
digestive system acquires food and eliminates wastes
excretory system eliminates metabolic waste
circulatory system- distributes gases,nutrients, and wastesthroughout the body
- exchanges materialsbetween blood andbody cells through theinterstitial fluid
Every organism must exchange energy and nutrients/wastes with surroundings
Function of CV System
Circulatory systems facilitate exchange with all body tissues
All cells must
– receive nutrients,
– exchange gases, and
– remove wastes.
Diffusion alone is inadequate for large and complex bodies.
In most animals, circulatory systems facilitate these exchanges.
– Assists diffusion by moving materials between
– surfaces of the body and Internal tissues.
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Simple Gastrovascular Cavity is Found in Cnidarians and Flatworms
Gastrovascular cavity serves both in digestion and distribution of substances throughout body
This is adequate for these organisms as they are only two layers of cells thick - all cells can exchange materials directly with water.
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medusapolyp
Cnidarians = jellyfish and hydraNotice only one opening in/out!
Flatworms - We’re so flat because we exchange materials directly with environment.
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Gastrovascularcavity
Nerve cords
Bilateral symmetryNervoustissue clusters
Mouth/Anus
Eyecups
Only ONE entrance/exit! YIKES!!
Small organisms have sufficient SA:volume ratio that they do not require a specialized circulatory system.
Diffusion
Mouth
Diffusion
Two cell layersSingle cell
Diffusion
Gastrovascularcavity
Large, more complex organisms require a true circulatory system
Most animals use a true circulatory system that consists of a
– circulatory fluid (blood),
– muscular pump (heart), and
– set of tubes (blood vessels) to carry the fluid.
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EXTERNAL ENVIRONMENT
MouthFood
CO2 O2
ANIMAL
Digestivesystem
Respiratorysystem
Circulatorysystem
Urinarysystem
HeartInterstitialfluid
Bodycells
Intestine
Anus
Unabsorbedmatter (feces)
Metabolic wasteproducts (urine)
Nutrients
Blo
od
But large, complex organisms require true CV system to maintain sufficient SA:volume ratio
2 Types of Circulatory Systems
Open circulatory systems are found in arthropods and many molluscs and consist of
– a heart,
– open-ended vessels, and
– blood that directly bathes the cells and functions as the interstitial fluid.
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PoresTubularheart
LE 42-3
Hemolymph in sinusessurrounding organs
Heart
Anteriorvessel
Ostia
Tubular heart
An open circulatory system.
Lateralvessel
A closed circulatory system.
Auxiliary hearts Ventral vessels
Dorsal vessel(main heart)
Small branch vesselsin each organ
Interstitialfluid
Heart
Two Types of Circulatory Systems
Closed circulatory systems are found in vertebrates, earthworms, squids, and octopuses and consist of
– a heart and
– vessels that confine blood, keeping it distinct from interstitial fluid.
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Three Types of Blood Vessels Found in CV Systems
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Artery(O2-rich blood)
Artery(O2-poor blood)
Capillarybeds
Gillcapillaries
Arteriole
Venule
Vein
HeartAtrium
Ventricle
1. Arteries carry blood away from the heart.
2. Veins return blood to the heart.
3. Capillaries convey blood between arteries and veins.
Vertebrate cardiovascular systems reflect evolution
Closed circulatory systems may exhibit:
In single circulation blood moves
– from gill capillaries,
– to systemic (body) capillaries, and
– back to the heart.
– Blood pressure drops significantly as blood flows thru gill capillaries
– Single circuit would never provide enough pressure to push blood thru the lungs and rest of body in a terresterial (land) animal.
– Characteristic of fish.
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Figure 23.2A
Gillcapillaries
Bodycapillaries
Heart:
Ventricle
Atrium
LE 42-4
FISHES
Gill capillaries
AMPHIBIANS
Lung and skin capillaries
REPTILES (EXCEPT BIRDS)
Lung capillaries
MAMMALS AND BIRDS
Lung capillaries
Gillcirculation
Heart:Ventricle (V)
Atrium (A)
Artery
VeinSystemic
circulation
Systemic capillaries Systemic capillaries
Systemiccircuit
Pulmocutaneouscircuit
Right Left
AA
V
A
V
A
V
Systemic capillaries
Right Left
Pulmonarycircuit
Rightsystemic aorta
V
A
V
Systemic capillaries
Right Left
Pulmonarycircuit
A
Systemiccircuit
Leftsystemic aorta
Systemic circuits include all body tissues except lungs. Note that circulatory systems are depicted as if the animal is facing you: with the right side of the heart shown at the left and vice-versa.
Double circulation
double circulation consists of a separate
– pulmonary circuit (heart to lungs and back to heart)
– systemic circuit (heart to body tissue and back to heart)
– Found in land animals - amphibians, reptiles, birds, mammals
– Allows for a second ‘push’ of blood returning from lungs to provide enough pressure for blood to travel without organism’s body.
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Four Chambered hearts are essential for organism with high metabolic rates (energy demands)
Four-chambered hearts
– are found in crocodilians, birds, and mammals and
– consist of
– two atria and
– two ventricles.
– Birds, mammals and crocodiles are warm-blooded (endotherms) and thus require much greater rates of cellular respiration (thus more O2) to meet energy demands
– Prevents oxygen-rich and oxygen-poor blood from mixing and keeps pulmonary and systemic circuits completely separate
– oxygen-rich and
– oxygen-poor blood.
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Blood flow through the human CV circuits
Blood flow through the double circulatory system of humans
– drains from the superior vena cava (from the head and arms) or inferior vena cava (from the lower trunk and legs) into the right atrium,
– moves out to the lungs via the pulmonary artery,
– returns to the left atrium through the pulmonary vein, and
– leaves the heart through the aorta.
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Animation: Path of Blood Flow in Mammals
Figure 23.3A
Superiorvena cava
Pulmonary artery
Capillaries ofright lung
Pulmonary vein
Right atrium
Right ventricle
Inferior vena cava
Aorta
Capillaries ofhead, chest andarms
Pulmonary artery
Capillariesof left lung
Pulmonary vein
Left atrium
Left ventricle
Aorta
Capillaries ofabdominal regionand legs8
91
6
4
543 3
272
9
8
10
LE 42-6
Right atrium
Posteriorvena cava
Pulmonaryveins
Anteriorvena cava
Pulmonary artery
Pulmonaryveins
Rightventricle
Aorta
Semilunarvalve
Atrioventricularvalve
Pulmonaryartery
Left atrium
Semilunarvalve
Atrioventricularvalve
Leftventricle
The Cardiac Cycle
The repeated contraction and relaxation of pumping blood is called the cardiac cycle. The cycle consists of two main phases.
1. During diastole, heart relaxes and all chambers fill with blood
2. During systole, heart contracts and blood flows
– from atria into ventricles
– Then from ventricles into arteries
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23.4 The heart contracts and relaxes rhythmically
Cardiac output is the amount of blood pumped per minute from the ventricles.
Cardiac output = Heart rate x volume of blood pumped with each contraction
Heart rate = is the number of heart beats per minute.
Heart rate and cardiac output vary with physiological conditions
Athletes have high CO even with low heart rates due to increased blood volume acquired from training
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23.5 The SA node sets the tempo of the heartbeat
The SA (sinoatrial) node
– generates electrical signals in atria and
– sets the rate of heart contractions.
– Called the pacemaker of the heart
– SA Node receives nervous signal info from central nervous system and relays these changes in heart rate to rest of heart to coordinate cardiac cycle and heart rate.
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1
ECG
Rightatrium
SA node(pacemaker)
Signals from theSA node spreadthrough the atria.
STRUCTURE AND FUNCTION OF BLOOD VESSELS
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23.7 The structure of blood vessels fits their functions
Capillaries
– Function:
– only vessels involved in exchange of solutes and fluid between blood and interstitial fluid.
– Structure:
– have thin walls consisting of a single layer of epithelial cells,
– are narrow, about as wide as one red blood cell, and
– Structure allows for increased surface area to facilitate gas and fluid exchange
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Capillary Red bloodcell
Capillary
Interstitialfluid
Tissuecell
Diffusion ofmolecules
23.7 The structure of blood vessels fits their functions
Arteries and veins
– are lined by a single layer of epithelial cells and
– connective tissue layer and smooth muscle that allows these vessels to recoil after stretching.
– Arteries:
– Largest in diameter of all vessels
– thickest layer of smooth muscle in their walls
– Allows them to constrict and reduce blood flow
– Deal with higher blood pressure and exhibit increased elasticity
– Veins:
– have one-way valves that restrict backward flow of blood.
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Figure 23.7C
Capillary
Epithelium
Epithelium
Smoothmuscle
Epithelium
Smoothmuscle
Basal lamina
Connectivetissue Connective
tissueArtery
Arteriole Venule
Vein
Valve
23.8 Blood pressure and velocity
Blood pressure
– is the force blood exerts on vessel walls,
– depends on:
– cardiac output (volume of blood and heart rate)
– resistance of vessels to expansion
– decreases as blood moves away from the heart.
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23.8 Blood pressure and velocity
Blood pressure is
– highest in arteries and
– lowest in veins.
Blood pressure is measured as
– systolic pressure — caused by ventricular contraction,
– diastolic pressure — low pressure between contractions.
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Figure 23.8A
Systolic pressure
Diastolic pressure
Relative sizes andnumbers of bloodvessels
Pre
ssu
re(m
m H
g)
Vel
oci
ty(c
m/s
ec)
Ao
rta
Art
erie
s
Art
erio
les
Cap
illa
ries
Ven
ule
s
Vei
ns
Ven
ae c
avae
120100
806040200
50
3020100
40
23.8 Blood pressure and velocity reflect the structure and arrangement of blood vessels
How does blood travel against gravity, up legs?
– Veins are squeezed by pressure from muscle contractions between
– two muscles or
– muscles and bone or skin.
– One-way valves limit blood flow to one direction, toward the heart.
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Direction ofblood flowin vein
Valve(open)
Contractingskeletalmuscle
Valve(closed)
Measuring blood pressure can reveal cardiovascular problems
A typical blood pressure for a healthy young adult is about 120/70.
Hypertension is a serious cardiovascular problem in which blood pressure is persistent at or above
– 140 systolic and/or
– 90 diastolic.
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23.10 Smooth muscle controls the distribution of blood
Blood flow through capillaries is restricted by precapillary sphincters.
By opening and closing these precapillary sphincters, blood flow to particular regions can be increased or decreased.
Only about 5–10% of capillaries are open at one time.
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Figure 23.10
2
1
Sphincters are contracted.
Sphincters are relaxed.
Precapillarysphincters
Thoroughfarechannel
ArterioleCapillaries
Venule
VenuleArteriole
Thoroughfarechannel
23.11 Exchange of materials between blood and interstitial fluid occurs at capillaries
Substances leave blood and enter interstitial fluid by
– diffusion (following concentration gradient) and
– pressure-driven flow through clefts between epithelial cells.
Blood pressure forces fluid (water) out of capillaries at the arterial end.
Osmotic pressure draws in fluid (water) at the venous end.
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LE 42-14
Capillary Red bloodcell
15 µm
Tissue cell
CapillaryNet fluidmovement out
INTERSTITIAL FLUID
Net fluidmovement in
Blood pressureOsmotic pressure
Inward flow
Direction ofblood flow
Pre
ssu
re
Outward flow
Venous endArterial end of capillary
Glucose, O2, and other nutrients have greatest concentration in blood at arterial end so they move out by diffusion
CO2 and other wastes have greatest concentration in interstitial fluid at venous end so they move in by diffusion
Water moves by net effect of blood versus osmotic pressure
STRUCTURE AND FUNCTION
OF BLOOD
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23.12 Blood consists of red and white blood cells suspended in plasma
Plasma (55%)
Cellular elements (45%)Constituent Major functions
Water Solvent forcarrying othersubstances
Ions (blood electrolytes)
SodiumPotassiumCalciumMagnesiumChlorideBicarbonate
Osmotic balance,pH buffering, andmaintaining ionconcentration ofinterstitial fluid
Plasma proteins
Fibrinogen
Immunoglobulins(antibodies)
Osmotic balanceand pH buffering
Clotting
Defense
Substances transported by blood
Nutrients (e.g., glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)Hormones
Centrifugedblood
sample
Cell type Numberper L (mm3) of blood)
Functions
Transport of O2 and some CO2
5–6 million
Red blood cells(erythrocytes)
White blood cells(leukocytes)
5,000–10,000 Defenseand immunity
Platelets250,000–400,000
Blood clotting
BasophilsEosinophils
Lymphocytes
Neutrophils Monocytes
Figure 23.13
New Blood Cells are generated in bone marrow from stem cells
Multipotent stem cells
– are unspecialized and
– replace themselves throughout the life of an organism.
Multipotent stem cells can differentiate into two main types of stem cells.
1. Lymphoid stem cells can in turn produce two types of lymphocytes (T- and B-cells), which function in the immune system.
2. Myeloid stem cells can differentiate into– erythrocytes,
– other white blood cells, and
– platelets.© 2012 Pearson Education, Inc.
Figure 23.15
Lymphocytes Monocytes Neutrophils
Eosinophils
Basophils
Myeloidstem cells
Platelets
Erythrocytes
Lymphoidstem cells
Multipotentstem cells(in bone marrow)
Figure 50.17 Control of Blood Pressure through Local and Systemic Mechanisms
Figure 50.18 Regulating Cardiac Output