CAMPBELL BIOLOGY IN FOCUS
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
34
Circulation and
Gas Exchange
Lecture Presentations by
Kathleen Fitzpatrick and Nicole Tunbridge
© 2014 Pearson Education, Inc.
Considering animal organ systems, interpret the
following statement:
Structure enables function.
How would this statement apply to a
circulatory and respiratory system in multicelled organisms compared to single-celled
organisms?
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How do life processes differ in single-celled
compared to multi-celled organisms?
§ The resources that animal cells require enter the
cytoplasm by crossing the plasma membrane
By the way, Describe the mechanisms for transport
across the plasma membrane.
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How do life processes differ in single-celled
compared to multi-celled organisms?
§ In unicellular organisms, these exchanges occur
directly with the environment
§ Most multicellular organisms rely on specialized
systems that carry out exchange with the environment
and transport materials through the body
§ (e.g. gills, lungs)
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Transport + Gas Exchange :: Peanut Butter + Jelly
§ Internal transport and gas exchange are functionally
related in most animals
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§ In small or thin animals, cells can exchange
materials (What kinds of materials?) directly with
the surrounding medium
§ In most animals, cells exchange materials with the
environment via a fluid-filled circulatory system
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§ Small, nonpolar molecules such as O2 and CO2
move between cells and their immediate
surroundings by diffusion
§ In some cases, nutrients may enter the cell
through facilitated diffusion (e.g. GlucoseTransport Proteins) or active transport.
§ Diffusion time is proportional to the square of the
distance travelled
§ Diffusion is only efficient over small distances
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Describe the most evolved anatomical components
of a circulatory system (i.e. mammalian).
What parts would you find?
How would they work?
How does the part enable the function
(basically justify its presence)?
What are possible disruptions of homeostasis?
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Comparative Transport
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Gastrovascular Cavities
§ Some animals lack a circulatory system
§ Some cnidarians, such as jellies, have elaborate
gastrovascular cavities
§ A gastrovascular cavity functions in both digestion
and distribution of substances throughout the body
§ The body wall that encloses the gastrovascular
cavity is only two cells thick
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Circulation: Hydra
Points to Consider:
§ Extracellular
digestion of
macronutrients
§ How are digested
nutrients transported
to the tissue layers
of the Hydra?
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Circulation: Hydra
Points to Consider:
§
Extracellular digestion
of macronutrients
§
How are digested
nutrients transported to
the tissue layers of the
Hydra?
Nutrients diffuse
throughout the two
layers of the organism.
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Phylum: Cnidaria
•Circulation
•flagellated cells circulate in GV cavity
circulate materials
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Structure of the Hydra
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Flatworms ( Phyla: Platyhelminthes) have a
gastrovascular cavity and a flat body shape to
optimize diffusional exchange with the
environment
.
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Figure 34.2
Mouth
Gastrovascular
cavity
1 mm
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There are two types of
Circulatory Systems:
Open and Closed
Grasshopper
Open Circulatory
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Earthworm
Closed Circulatory
In Groups:
Compare and Contrast the circulatory systems of the
earthworm and the grasshopper.
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§ All circulatory systems are either open or closed
§ In insects, other arthropods, and some molluscs,
circulatory fluid bathes the organs directly in an
open circulatory system
§ In an open circulatory system, there is no distinction
between circulatory fluid and interstitial fluid, and
this general body fluid is called hemolymph
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Figure 34.3a
(a) An open circulatory system
Heart
Hemolymph in sinuses
Pores
Tubular heart
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§ In closed circulatory systems the circulatory fluid
called blood is confined to vessels and is distinct
from interstitial fluid
§ These systems are found in annelids, most
cephalopods, and all vertebrates
§ One or more hearts pump blood through the vessels
§ Chemical exchange occurs between blood and
interstitial fluid and between interstitial fluid and
body cells
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Figure 34.3b
(b) A closed circulatory system
Blood
Heart
Interstitial
fluid
Branch vessels
in each organ
Dorsal vessel
(main heart)
Auxiliary
hearts
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Ventral vessels
Organization of Vertebrate Circulatory Systems
§ Humans and other vertebrates have a closed
circulatory system called the cardiovascular
system
§ The three main types of blood vessels are arteries,
veins, and capillaries
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Considering the closed circulatory system design,
how could you ensure unidirectional flow of
fluid?
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Considering the closed circulatory system design,
how could you ensure unidirectional flow of
fluid?
Introduce valves to control the flow in one
direction; prevents backflow
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A.
In Groups:
B.
C.
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Label each structure
as an artery, vein or
capillary.
Justify your choice
by explaining how
the structure enables
the vessel’s function.
§ Arteries branch into arterioles and carry blood
away from the heart to capillaries
§ Networks of capillaries called capillary beds are
the sites of chemical exchange between the blood
and interstitial fluid
§ Venules converge into veins and return blood from
capillaries to the heart
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§ Arteries and veins are distinguished by the direction
of blood flow, not by O2 content
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§ Vertebrate hearts contain two or more chambers
§ Blood enters through an atrium and is pumped out
through a ventricle
§ Compare the organization of a two-chambered,
three-chambered, and four-chambered
circulatory system.
§ Which is more evolved? Justify your answer.
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Figure 34.4
(a) Single circulation: fish
Gill capillaries
(b) Double circulation:
amphibian
Vein
Pulmonary
circuit
Pulmocutaneous
circuit
Lung
and skin
capillaries
Artery
Heart:
Atrium (A)
Ventricle (V)
(c) Double circulation:
mammal
A
Right
Lung
capillaries
A
V
A
Left
Right
V
A
V
Left
Systemic
capillaries
Body capillaries
Key
Oxygen-rich blood
Oxygen-poor blood
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Systemic circuit
Systemic
capillaries
Systemic circuit
Single Circulation
§ Bony fishes, rays, and sharks have single circulation
with a two-chambered heart
§ In single circulation, blood leaving the heart
passes through two capillary beds before returning
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Double Circulation
§ Amphibians, reptiles, and mammals have double
circulation
§ Oxygen-poor and oxygen-rich blood is pumped
separately from the right and left sides of the heart
§ Having both pumps within a heart simplifies
coordination of the pumping cycle
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§ In reptiles and mammals, oxygen-poor blood flows
through the pulmonary circuit to pick up oxygen
through the lungs
§ In amphibians, oxygen-poor blood flows through a
pulmocutaneous circuit to pick up oxygen through
the lungs and skin
§ Oxygen-rich blood delivers oxygen through the
systemic circuit
§ Double circulation maintains higher blood pressure
in the organs than does single circulation
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Evolutionary Variation in Double Circulation
§ Some vertebrates with double circulation are
intermittent breathers
§ These animals have adaptations that enable the
circulatory system temporarily to bypass the lungs
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§ Frogs and other amphibians have a threechambered heart: two atria and one ventricle
§ The ventricle pumps blood into a forked artery that
splits the ventricle’s output into the pulmocutaneous
circuit and the systemic circuit
§ When underwater, blood flow to the lungs is nearly
shut off
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§ Turtles, snakes, and lizards have a three-chambered
heart: two atria and one ventricle
§ Their circulatory system allows control of relative
amounts of blood flowing to the lungs and body
§ In alligators, caimans, and other crocodilians a
septum divides the ventricle
§ A connection to atrial valves can temporarily shunt
blood away from the lungs, as needed
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§ Mammals and birds have a four-chambered heart
with two atria and two ventricles
§ The left side of the heart pumps and receives only
oxygen-rich blood, while the right side receives and
pumps only oxygen-poor blood
§ There is no mechanism to vary relative blood flow to
the lungs and body
§ Mammals and birds are endotherms and require
more O2 than ectotherms
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Four-chambered heart: How does it work (i.e. to
meet the constant demand for gas exchange?
Describe the flow of blood through the
mammalian system.
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Figure 34.5
Superior
vena cava
Capillaries of
head and
forelimbs
7
Pulmonary
artery
Capillaries
of right lung
Pulmonary artery
Capillaries
of left lung
Aorta
9
6
2
3
3
4
11
Pulmonary
vein
Right atrium
1
Pulmonary
vein
Left atrium
5
10
Left ventricle
Right ventricle
Inferior vena cava
Aorta
8
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Capillaries of
abdominal organs
and hind limbs
Mammalian Circulation
§ Blood begins its flow with the right ventricle pumping
blood to the lungs via the pulmonary arteries
§ The blood loads O2 and unloads CO2 in the capillary
beds of the lungs
§ Oxygen-rich blood from the lungs enters the heart at
the left atrium via the pulmonary veins and is
pumped through the aorta to the body tissues by the
left ventricle
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§ The aorta provides blood to the heart through the
coronary arteries
§ Diffusion of O2 and CO2 takes place in the capillary
beds throughout the body
§ Blood returns to the heart through the superior vena
cava (blood from head, neck, and forelimbs) and
inferior vena cava (blood from trunk and hind limbs)
§ The superior vena cava and inferior vena cava flow
into the right atrium
Animation: Path of Blood Flow
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The Mammalian Heart: A Closer Look
§ A closer look at the mammalian heart provides a
better understanding of double circulation
§ When the heart contracts, it pumps blood; when it
relaxes, its chambers fill with blood
§ One complete sequence of pumping and filling is
called the cardiac cycle
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Structurally, why are atria receiving chambers
and ventricles pumping chambers?
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Figure 34.6
Aorta
Pulmonary artery
Pulmonary
artery
Right
atrium
Left
atrium
Semilunar
valve
Semilunar
valve
Atrioventricular
(AV) valve
Atrioventricular
(AV) valve
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Right
ventricle
Left
ventricle
§ Atria have relatively thin walls and serve as
collection chambers for blood returning to the heart
§ The ventricles are more muscular and contract much
more forcefully than the atria
§ The volume of blood each ventricle pumps per
minute is called the cardiac output
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The cardiac cycle
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Figure 34.7-1
1 Atrial and
ventricular
diastole
0.4
sec
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Figure 34.7-2
2 Atrial systole and
ventricular diastole
1 Atrial and
ventricular
diastole
0.1
sec
0.4
sec
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Figure 34.7-3
2 Atrial systole and
ventricular diastole
1 Atrial and
ventricular
diastole
0.1
sec
0.4
sec
0.3 sec
3 Ventricular systole
and atrial diastole
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§ The heart rate, also called the pulse, is the number
of beats per minute
§ The stroke volume is the amount of blood pumped
in a single contraction
§ Cardiac output depends on both the heart rate and
stroke volume
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List the valves that control blood flow into and out
of the heart.
Where are they located and
Describe their functions.
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§ Four valves prevent backflow of blood in the heart
§ The atrioventricular (AV) valves separate each
atrium and ventricle
§ Bicuspid and Tricuspid
§ The semilunar valves control blood flow to the
aorta and the pulmonary artery
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§ The “lub-dup” sound of a heart beat is caused by
the recoil of blood against the AV valves (lub) then
against the semilunar (dup) valves
§ Backflow of blood through a defective valve causes
a heart murmur
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Where is the pacemaker located and how does it
work?
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Maintaining the Heart’s Rhythmic Beat
§ Some cardiac muscle cells are autorhythmic,
meaning they contract without any signal from the
nervous system
§ The sinoatrial (SA) node, or pacemaker, sets the
rate and timing at which all other cardiac muscle
cells contract
§ The SA node produces electrical impulses that
spread rapidly through the heart and can be
recorded as an electrocardiogram (ECG or EKG)
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Figure 34.8-1
1 Signals (yellow)
from SA node
spread
through atria.
SA node
(pacemaker)
ECG
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Figure 34.8-2
1 Signals (yellow)
from SA node
spread
through atria.
SA node
(pacemaker)
ECG
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2 Signals are
delayed
at AV node.
AV
node
Figure 34.8-3
1 Signals (yellow)
from SA node
spread
through atria.
SA node
(pacemaker)
ECG
© 2014 Pearson Education, Inc.
2 Signals are
delayed
at AV node.
AV
node
3 Bundle
branches
pass signals
to heart apex.
Bundle
branches
Heart
apex
Figure 34.8-4
1 Signals (yellow)
from SA node
spread
through atria.
SA node
(pacemaker)
ECG
© 2014 Pearson Education, Inc.
2 Signals are
delayed
at AV node.
AV
node
3 Bundle
branches
pass signals
to heart apex.
Bundle
branches
Heart
apex
4 Signals
spread
throughout
ventricles.
Purkinje
fibers
§ Impulses from the SA node travel to the
atrioventricular (AV) node
§ At the AV node, the impulses are delayed and
then travel to the Purkinje fibers that make the
ventricles contract
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§ The pacemaker is regulated by two portions of the
nervous system: the sympathetic and
parasympathetic divisions
§ The sympathetic division speeds up the pacemaker
§ The parasympathetic division slows down the
pacemaker
§ The pacemaker is also regulated by hormones and
temperature
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Concept 34.3: Patterns of blood pressure and flow
reflect the structure and arrangement of blood
vessels
§ The physical principles that govern movement of
water in plumbing systems also apply to the
functioning of animal circulatory systems
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Closer look at the physiology of the blood
vessels…
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Blood Vessel Structure and Function
§ A vessel’s cavity is called the central lumen
§ The epithelial layer that lines blood vessels is called
the endothelium
§ The endothelium is smooth and minimizes resistance
to blood flow
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§ Capillaries have thin walls, the endothelium and its
basal lamina, to facilitate the exchange of
substances
§ Arteries and veins have an endothelium, smooth
muscle, and connective tissue
§ Arteries have thicker walls than veins to
accommodate the high pressure of blood pumped
from the heart
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Figure 34.9a
Valve
Connective
tissue
Endothelium
Basal lamina
Smooth
muscle
Smooth
muscle
Capillary
Endothelium
Artery
Vein
Arteriole
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Venule
Connective
tissue
Figure 34.9b
LM
Artery Vein
Red blood
cells
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100 µm
Capillary
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LM
Red blood cell
15 µm
Figure 34.9c
Blood Flow Velocity
§ Blood vessel diameter influences blood flow
§ Velocity of blood flow is slowest in the capillary
beds, as a result of the high resistance and large
total cross-sectional area
§ Blood flow in capillaries is necessarily slow for
exchange of materials
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4,000
2,000
0
40
20
0
120
80
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Venae
cavae
Veins
Arteries
40 Diastolic
pressure
0
Arterioles
Capillaries
Venules
Systolic
pressure
Aorta
Pressure
(mm Hg)
Velocity
(cm/sec)
Area (cm2)
Figure 34.10
Blood Pressure
§ Blood flows from areas of higher pressure to areas
of lower pressure
§ Blood pressure exerts a force in all directions
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Changes in Blood Pressure During the Cardiac
Cycle
§ Systole is the contraction phase of the cardiac cycle
§ Pressure at the time of ventricle contraction is called
systolic pressure
§ Diastole is the the relaxation phase of the cardiac
cycle; diastolic pressure is lower than systolic
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Maintenance of Blood Pressure
§ Blood pressure is determined by cardiac output and
peripheral resistance due to constriction of
arterioles
§ Vasoconstriction is the contraction of smooth
muscle in arteriole walls; it increases blood pressure
§ Vasodilation is the relaxation of smooth muscles in
the arterioles; it causes blood pressure to fall
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§ Vasoconstriction and vasodilation help maintain
adequate blood flow as the body’s demands change
§ Nitric oxide is a major inducer of vasodilation
§ The peptide endothelin is an important inducer of
vasoconstriction
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§ Fainting is caused by inadequate blood flow to the
head
§ Animals with long necks require a higher systolic
pressure to pump blood against gravity
§ Gravity is a consideration for blood flow in veins,
particularly in the legs
§ One-way valves in veins prevent backflow of blood
§ Blood returns to the heart through contraction of
smooth muscle in the walls of veins and venules and
by contraction of skeletal muscles
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Figure 34.11
Direction of blood
flow in vein
(toward heart)
Valve (open)
Skeletal muscle
Valve (closed)
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How is capillary exchange with the
surrounding tissue enabled?
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Capillary Function
§ Blood flows through only 5–10% of the body’s
capillaries at a time
§ Capillaries in major organs are usually filled to
capacity
§ Blood supply varies in many other sites
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§ Two mechanisms alter blood flow in capillary beds
§ Vasoconstriction or vasodilation of the arteriole that
supplies a capillary bed
§ Precapillary sphincters, rings of smooth muscle at the
capillary bed entrance, open and close to regulate
passage of blood
§ Critical exchange of substances takes place across
the thin walls of the capillaries
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Capillary exchange (Express version)
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§ Blood pressure tends to drive fluid out of the
capillaries
§ The difference in solute concentration between blood
and interstitial fluid (the blood’s osmotic pressure)
opposes fluid movement from the capillaries
§ Blood pressure is usually greater than osmotic
pressure
§ Net loss of fluid from capillaries occurs in regions
where blood pressure is highest
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Fluid Return by the Lymphatic System
§ The lymphatic system returns fluid, called lymph,
that leaks out from the capillary beds
§ Lymph has a very similar composition to interstitial
fluid
§ The lymphatic system drains into veins in the neck
§ Valves in lymph vessels prevent the backflow of
fluid
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Figure 34.12
Blood
capillary
Interstitial
fluid
Adenoid
Tonsils
Lymphatic
vessels
Thymus
(immune
system)
Tissue cells
Lymphatic
vessel
Spleen
Lymph
nodes
Appendix
(cecum)
Peyer’s patches
(small intestine)
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Lymphatic
vessel
Lymph node
Masses of
defensive
cells
§ Lymph vessels have valves to prevent backflow
§ Lymph nodes are organs that filter lymph and play
an important role in the body’s defense
§ Edema is swelling caused by disruptions in the flow
of lymph
§ The lymphatic system also plays a role in harmful
immune responses, such as those responsible for
asthma
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Capillary exchange is very important, so review
the next few slides only if you need a step by
step discussion of how capillary exchange at the
tissue level occurs (otherwise skip to slide 112)
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Problem:
How does material move into and out of the
capillaries?
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In Groups:
On which side of the capillaries would there
be the greatest blood pressure ?
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How would you describe the content of the
blood being carried within the arterioles?
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How would you describe the content of the blood
being carried within the arterioles?
-High in O2, high in nutrients and water
-Contains plasma proteins, white blood cells, red
blood cells, platelets
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Considering what we discussed so far, how
would you propose that this dissolved
material (+fluid) gets pushed out of the
capillaries into the surrounding tissue area?
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Considering what we discussed so far, how would
you propose that this dissolved material (+fluid)
gets pushed out of the capillaries into the
surrounding tissue are?
The heart pumps blood with high pressure in the
arteries into the arterioles…fluid is forced out at
the arteriole end.
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Interstitial Fluid (Tissue Fluid)
§Interstitial Fluid:
§ Lymph- bathes the cells
and serves as the
medium for exchange
§ Interstitial fluid consists
of a water solvent
containing amino acids,
sugars, fatty acids,
coenzymes, hormones,
neurotransmitters, salts,
for the cells
§ Carried by lymph
vessels
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How does the necessary material get into the
cells?
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How does the necessary material get into the cells?
Diffusion
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What materials must leave the cell and enter the
capillaries?
Describe the process that enables the movement
of waste into the capillaries.
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What materials must leave the cell and enter the
capillaries?
Carbon dioxide and other metabolic wastes must
enter the capillaries.
Describe the process that enables the movement
of waste into the capillaries.
Diffusion
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Understanding that most of fluid is leaving at the
arteriole end, what problem do we have when
considering blood flow?
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Understanding that most of fluid is leaving at the
arteriole end, what problem do we have when
considering blood flow?
There is more fluid moving from the blood into
the interstitial space. Due to the build-up of
interstitial fluid, the space is swelling.
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Let’s look at the plasma and lymph in more
detail.
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How do these two fluids differ from each
other?
Lymph
§Protein (%)- 2.61
§Non-Protein (mg/100mL)27.2
Plasma
§Protein (%)- 6.85
§Non-Protein (mg/100mL)- 27
§Glucose (mg/100mL)- 12.4
§Glucose (mg/100mL)- 12.3
§Urea (mg/100mL)- 23.5
§Urea (mg/100mL)- 22
§Amino acids (mg/100mL)- 4.8
§Amino acids (mg/100mL)4.9
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§Ca ions (mg/100mL)- 9.2
Lymph does not contain proteins, also there are no
red blood cells in lymph (only in plasma).
Why does lymph have little
protein content?
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Lymph does not contain proteins, also there are no
red blood cells in lymph (only in plasma).
Why does lymph have little
protein content?
The proteins are too large to diffuse out of the
capillaries, therefore they remain dissolved in the
plasma
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Greater concentration of solute is inside the
capillaries, as a result of large amounts of fluid
leaving the capillaries at the arteriole end.
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In Groups:
Where will there be the greatest
concentration of water movement?
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What process enables the movement of water
molecules from an area of high concentration to
low concentration?
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What process enables the movement of water
molecules from an area of high concentration to
low concentration?
Osmosis
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Movement of water into the capillaries is due to
Collodial Osmotic Pressure.
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Blood pressure is lower at the
venule end of the capillaries.
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What is the net movement of molecules in the
beginning?
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What is the next movement of molecules at the
end?
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When the two pressures are equal, material can
diffuse along concentration gradients (passively).
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Concept 34.4: Blood components function in
exchange, transport, and defense
§ With open circulation, the fluid that is pumped
comes into direct contact with all cells and has
the same composition as interstitial fluid
§ The closed circulatory systems of vertebrates
contain blood, which can be much more highly
specialized
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Blood is connective tissue.
Describe its composition and how do the
specialized cells work together for a particular
function?
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Blood Composition and Function
§ Blood is a connective tissue consisting of cells
suspended in a liquid matrix called plasma
§ The cellular elements occupy about 45% of the
volume of blood
Video: Leukocyte Rolling
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Figure 34.13
Cellular elements 45%
Plasma 55%
Constituent
Water
Ions (blood
electrolytes)
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Major functions
Solvent for
carrying other
substances
Osmotic balance,
pH buffering,
and regulation
of membrane
permeability
Leukocytes (white blood cells)
Separated
blood
elements
per µL (mm3)
of blood
Functions
5,000–10,000
Defense
and
immunity
Lymphocytes
Basophils
Eosinophils
Plasma proteins
Neutrophils
Albumin
Osmotic balance,
pH buffering
Fibrinogen
Clotting
Immunoglobulins
(antibodies)
Defense
Substances transported by blood
Nutrients (such as glucose, fatty
acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
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Number
Cell type
Monocytes
Platelets
Erythrocytes (red blood cells)
250,000–400,000
5,000,000–
6,000,000
Blood
clotting
Transport
of O2 and
some CO2
Plasma
§ Blood plasma is about 90% water
§ Among its solutes are inorganic salts in the form of
dissolved ions, sometimes called electrolytes
§ Plasma proteins influence blood pH, osmotic
pressure, and viscosity
§ Particular plasma proteins function in lipid transport,
immunity, and blood clotting
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Cellular Elements
§ Blood contains two classes of cells
§ Red blood cells (erythrocytes) transport O2
§ White blood cells (leukocytes) function in defense
§ Platelets, a third cellular element, are fragments of
cells that are involved in clotting
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Figure 34.14
Stem cells
(in bone marrow)
Lymphoid
stem cells
Myeloid
stem cells
B cells T cells
Erythrocytes
Lymphocytes
Monocytes
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Neutrophils
Platelets
Basophils
Eosinophils
Erythrocytes
§ Red blood cells, or erythrocytes, are by far the most
numerous blood cells
§ They contain hemoglobin, the iron-containing
protein that transports O2
§ Each molecule of hemoglobin binds up to four
molecules of O2
§ In mammals, mature erythrocytes lack nuclei
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§ Sickle-cell disease is caused by abnormal
hemoglobin that polymerizes into aggregates
§ The aggregates can distort an erythrocyte into a
sickle shape
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§ Through a person’s life, multipotent stem cells
replace the worn-out cellular elements of blood
§ Erythrocytes circulate for about 120 days before
they are replaced
§ Stem cells that produce red blood cells and platelets
are located in red marrow of bones like the ribs,
vertebrae, sternum, and pelvis
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Leukocytes
§ There are five major types of white blood cells, or
leukocytes
§ They function in defense by engulfing bacteria and
debris or by mounting immune responses against
foreign substances
§ They are found both in and outside of the circulatory
system
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Platelets
§ Platelets are fragments of cells and function in
blood clotting
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Blood Clotting
§ Coagulation is the formation of a solid clot from
liquid blood
§ A cascade of complex reactions converts inactive
fibrinogen to fibrin, which forms the framework of a
clot
§ A blood clot formed within a blood vessel is called a
thrombus and can block blood flow
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Figure 34.15a
2
1
3
Collagen
fibers
Platelet
Platelet
plug
Clotting factors from:
Platelets
Damaged cells
Plasma (factors include calcium, vitamin K)
Enzymatic cascade
Prothrombin
Thrombin
Fibrinogen
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Fibrin
Fibrin clot
Fibrin clot
formation
Figure 34.15b
Fibrin
clot
Red blood cell
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5 µm
Disruptions of homeostasis in the
cardiovascular system?
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Cardiovascular Disease
§ Cardiovascular diseases are disorders of the heart
and the blood vessels
§ Cardiovascular diseases account for more than half
the deaths in the United States
§ Cholesterol, a steroid, helps maintain normal
membrane fluidity
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§ Low-density lipoprotein (LDL) delivers cholesterol
to cells for membrane production
§ High-density lipoprotein (HDL) scavenges excess
cholesterol for return to the liver
§ Risk for heart disease increases with a high LDL to
HDL ratio
§ Inflammation is also a factor in cardiovascular
disease
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Atherosclerosis, Heart Attacks, and Stroke
§ One type of cardiovascular disease, atherosclerosis,
is caused by the buildup of fatty deposits within
arteries
§ A fatty deposit is called a plaque; as it grows, the
artery walls become thick and stiff and the obstruction
of the artery increases
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Figure 34.16
Endothelium
Lumen
Blood clot
Plaque
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§ A heart attack, or myocardial infarction, is the death
of cardiac muscle tissue resulting from blockage of
one or more coronary arteries
§ Coronary arteries supply oxygen-rich blood to the
heart muscle
§ A stroke is the death of nervous tissue in the brain,
usually resulting from rupture or blockage of arteries
in the head
§ Angina pectoris is caused by partial blockage of the
coronary arteries and may cause chest pain
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Risk Factors and Treatment of Cardiovascular
Disease
§ A high LDL to HDL ratio increases the risk of
cardiovascular disease
§ The proportion of LDL relative to HDL is increased by
smoking and consumption of trans fats and
decreased by exercise
§ Drugs called statins reduce LDL levels and risk of
heart attacks
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§ Inflammation plays a role in atherosclerosis and
thrombus formation
§ Aspirin inhibits inflammation and reduces the risk of
heart attacks and stroke
§ Hypertension (high blood pressure) contributes to
the risk of heart attack and stroke
§ Hypertension can be reduced by dietary changes,
exercise, medication, or some combination of these
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