Transcript 23. Circulation

Chapter 23
Circulation
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
How Does Gravity Affect Blood Circulation?
• Most animals have a circulatory system that
transports O2 and nutrients to cells and takes away
CO2 and other wastes
• The circulatory system of land animals has evolved
adaptations to deal with gravity
–
Strong hearts are able to pump against the
force of gravity
–
Muscles contract around veins and force
blood to the heart through one-way valves
–
In snakes, wriggling contracts muscles,
squeezing veins and increasing circulation
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Video: Giraffe Courtship Ritual
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
23.1 The circulatory system connects with all
body tissues
• A circulatory system transports materials close
enough to cells for diffusion to occur
• Microscopic capillaries form an intricate
network among cells of a tissue
– Molecules from blood cells diffuse into
interstitial fluid and then into body cells
– Waste products diffuse from body cells
through interstitial fluid to capillaries for
transport to disposal organs
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-01b
Red
blood
cell
Capillary
Nuclei of
smooth
muscle
cells
LE 23-01b
Capillary
Interstitial
fluid
Tissue
cell
Diffusion of
molecules
MECHANISMS OF INTERNAL TRANSPORT
23.2 Several types of internal transport have
evolved in animals
• Gastrovascular cavity
– Sufficient for animals in which diffusion can
transport molecules directly to the cells
– Examples: cnidarians, flatworms
• Open circulatory system
– Heart pumps blood through open-ended
vessels to bathe tissue cells directly; no
separate interstitial fluid
– Body movements help circulate blood
– Examples: most molluscs, all arthropods
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LE 23-02a
Mouth
Circular
canal
LE 23-02b
Tubular heart
Pores
• Closed circulatory systems
– Blood is confined to vessels, which keeps it
separate from the interstitial fluid
• Arteries carry blood away from heart to
tissues and organs
• Veins return blood to the heart
• Capillaries convey blood between arteries
and veins within each tissue
– Most arteries carry oxygen-rich blood and most
veins carry oxygen-depleted blood, but there are
important exceptions
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LE 23-02c
Capillary beds
Arteriole
Artery
(O2-rich blood)
Venule
Vein
Atrium
Heart
Ventricle
Gill
capillaries
Artery
(O2-poor blood
23.3 Vertebrate cardiovascular systems reflect
evolution
• The switch from gill breathing to lung breathing in
terrestrial vertebrates was accompanied by
important changes in the cardiovascular system
• Single circuit in aquatic animals
– The two-chambered heart pumps blood from
gill capillaries to systemic capillaries and back
to the heart
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Double circulation in terrestrial vertebrates
– Pulmonary circuit carries blood between heart
and lungs
– Systemic circuit carries blood between heart
and rest of the body
– Amphibians: three-chambered heart
– Reptiles (except birds): three-chambered heart
with partially divided ventricle in most
– Birds and mammals: four-chambered heart
with ventricle completely divided
• Essential adaptation to support high
metabolic rate
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LE 23-03a
Gill capillaries
Heart:
Ventricle (V)
Atrium (A)
Systemic capillaries
LE 23-03b
Lung and skin capillaries
Pulmocutaneous
circuit
A
A
V
Right
Left
Systemic
circuit
Systemic capillaries
LE 23-03c
Lung capillaries
Pulmonary
circuit
A
A
V
V
Right
Left
Systemic
circuit
Systemic capillaries
THE MAMMALIAN CARDIOVASCULAR SYSTEM
23.4 The human heart and cardiovascular system
are typical of mammals
• The mammalian heart
– Formed mostly of cardiac muscle tissue
– Two thin-walled atria receive blood and pump it
into the ventricles
– Thick-walled ventricles pump blood to lungs
and other body organs
– Valves maintain the flow in one direction
Animation: Path of Blood Flow in Mammals
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-04a
Right
atrium
Left
atrium
Semilunar
valve
Semilunar
valve
Atrioventricular
(AV) valve
Atrioventricular
(AV) valve
Right
ventricle
Left
ventricle
• The flow of blood is from the heart to the lungs,
back to the heart, out to the body, and then back
to the heart
– Pulmonary circuit
1. Right ventricle
2. Pulmonary arteries
3. Capillaries in lungs
4. Pulmonary veins
5. Left atrium
6. Left ventricle
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• Systemic circuit
7. Aorta
8. Head, chest, arms, abdominal region, legs
9. Superior and inferior venae cavae
10. Right atrium to right ventricle
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LE 23-04b
Capillaries of
head, chest, and
arms
Superior
vena cava
Pulmonary
artery
Capillaries
of right lung
Pulmonary
vein
Right atrium
Right ventricle
Inferior
vena cava
Pulmonary
artery
Aorta
Capillaries
of left lung
Pulmonary
vein
Left atrium
Left ventricle
Aorta
Capillaries of
abdominal region
and legs
23.5 The structure of blood vessels fits their
functions
• Capillaries
– Thin walls with a single layer of epithelial cells
– Facilitate exchange of materials
• Arteries and veins
– Epithelium reinforced by layers of smooth
muscle and connective tissue
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
– Arteries
• Thicker walls accommodate the rapid
flow of blood and high pressure
• Smooth muscle can regulate blood
flow by constriction or relaxation
– Veins
• Thinner walls, under less pressure and
slower flow
• Valves prevent backflow
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-05
Capillary
Epithelium
Basement
membrane
Valve
Epithelium
Epithelium
Smooth
muscle
Connective
tissue
Smooth
muscle
Connective
tissue
Artery
Vein
Arteriole
Venule
23.6 The heart contracts and relaxes rhythmically
• The cardiac cycle is a complete sequence of
filling and pumping
• Diastole
1. Heart is relaxed; blood flows from the veins
into all four chambers
• Systole
2. Atria contract briefly; ventricles completely fill
with blood
3. Ventricles contract; valves open and close;
blood pumps into the large arteries and then
flows into atria
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-06
Atria
contract.
Heart is
relaxed.
AV valves
are open.
0.1 sec
Systole
0.3 sec
0.4 sec
Diastole
Ventricles
contract.
Semilunar
valves
are open.
• Cardiac output is the amount of blood/minute
pumped into the systemic circuit by the left
ventricle
• Heart valves prevent the backflow of blood
– “Lub-dup” sounds caused by the closing of
valves
– Heart murmur may indicate a valve defect
23.7 The pacemaker sets the tempo of the
heartbeat
• The pacemaker (SA node) maintains the heart’s
pumping rhythm
1. SA node generates electrical signals
2. Signals make atria contract in unison; are
delayed at AV node
3. Specialized muscle fibers relay signals to apex
of heart
4. Signals are relayed through walls of ventricles,
triggering contractions that drive blood out of
the heart
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-07
Pacemaker
(SA node)
AV node
Specialized
muscle fibers
Right
artium
Right
ventricle
ECG
Apex
• An electrocardiogram measures electrical
activity of the heart through changes in the skin
• An artificial pacemaker provides a regular
electrical signal to trigger normal heartbeat
• Heart rate is also influenced by nerves,
hormones, and environmental conditions
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
CONNECTION
23.8 What is a heart attack?
• A heart attack is the death of cardiac muscle cells and the
resulting failure of the heart to deliver enough blood to the
rest of the body
– Results from blockage in coronary arteries
• Cardiovascular disease is a leading cause of death in the
United States
– Atherosclerosis: development of plaques on artery
walls, impeding blood flow
– Tendency may be inherited, but lifestyle changes can
reduce risk
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-08a
Aorta
Superior
vena cava
Pulmonary
artery
Right
coronary
artery
Left
coronary
artery
Blockage
Dead
muscle
tissue
LE 23-08b
Connective
tissue
Smooth
muscle
Epithelium
Plaque
23.9 Blood exerts pressure on vessel walls
• Blood pressure is the force blood exerts against
the walls of blood vessels
– Caused by pumping of the heart
– Can be felt as pulse, the rhythmic stretching of
the arteries
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Blood pressure and velocity depend partly on
cardiac output and partly on the resistance of
vessels
– Highest in the aorta and arteries
– Decrease abruptly as blood enters
arterioles because of friction between
blood and large surface area
– Lowest in capillaries, because crosssectional area is greatest
– Near zero in veins
• Blood returns to the heart with the aid
of muscular contractions and valves
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Pressure (mm Hg)
LE 23-09a
120
Systolic
pressure
100
80
60
Diastolic
pressure
40
20
0
50
40
30
20
Venae cavae
Veins
Venules
Capillaries
Arterioles
0
Arteries
10
Aorta
Velocity (cm/sec)
Relative sizes and
numbers
of blood
vessels
LE 23-09b
Direction of
blood flow
in vein
Valve
(open)
Skeletal
muscle
Valve
(closed)
CONNECTION
23.10 Measuring blood pressure can reveal
cardiovascular problems
• Blood pressure indicates the force of the heart’s beating
during systole and the background pressure of the blood
in arteries during diastole
• Blood pressure is measured as systolic over diastolic
pressure, in mm Hg
– 110/70 is typical for a healthy young adult
• Higher than normal blood pressure may indicate serious
cardiovascular disorder
– Hypertension is persistent blood pressure higher than
140/90
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-10-3
Blood
pressure
110 systolic
70 diastolic
(to be measured)
Rubber cuff
inflated
with air
Artery
Pressure
in cuff
above 110
Pressure
in cuff
at 110
110
110
Pressure
in cuff
at 70
70
Artery
closed
Sounds
audible in
stethoscope
Sounds
stop
23.11 Smooth muscle controls the distribution of
blood
• Except for the brain, liver, kidneys, and heart,
blood supply varies depending on tissue need
• Constriction of arterioles can reduce blood flow
to capillaries
• Contraction and relaxation of precapillary
sphincters controls blood flow through capillary
beds
• Nerves and hormones influence the contraction
of smooth muscles in both mechanisms
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-11a
Precapillary sphincters
Thoroughfare
channel
Capillaries
Arteriole
Sphincters relaxed
Venule
LE 23-11b
Thoroughfare
channel
Arteriole
Sphincters contracted
Venule
23.12 Capillaries allow the transfer of substances
through their walls
• Capillaries are the only vessels with walls thin
enough to allow transfer of substances through
the epithelium
• The transfer of materials between the blood
and interstitial fluid occurs in several ways
– Diffusion
– Endocytosis and exocytosis
– Pressure-driven flow through clefts
between epithelial cells
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Forces driving fluid out of and into capillaries
– Blood pressure forces fluid out of the capillary
at the arterial end
– Osmotic pressure draws fluid in at the venous
end
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-12a
Capillary
lumen
Capillary
wall
Interstitial
fluid
Nucleus of
epithelial
cell
Muscle
cell
Cleft between
two epithelial
cells of the
capillary wall
LE 23-12b
Tissue cells
Osmotic
pressure
Arterial
end of
capillary
Blood
pressure
Interstitial
fluid
Net fluid
movement out
Osmotic
pressure
Blood
pressure
Net fluid
movement in
Venous
end of
capillary
STRUCTURE AND FUNCTION OF BLOOD
23.13 Blood consists of red and white blood cells
suspended in plasma
• Blood is about 55% plasma and 45% cellular
elements
– Plasma
• 90% water
• 10% dissolved inorganic ions, proteins,
nutrients, wastes, gases, and
hormones
– Red blood cells (erythrocytes)
• Transport O2 bound to hemoglobin
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
– White blood cells (leukocytes)
• Function both inside and outside the
circulatory system to fight infections
and cancer
– Platelets
• Cell fragments involved in clotting
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-13a
Plasma (55%)
Constituent
Major functions
Water
Solvent for
carrying other
substances
Salts (ions)
Osmotic balance,
pH buffering, and
nerve and muscle
function
Sodium
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Plasma proteins
Osmotic balance
and pH buffering
Fibrinogen
Clotting
Immunoglobulins
(anitbodies)
Immunity
Substances transported by blood
Nutrients (e.g., glucose, fatty acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones
Centrifuged
blood
sample
LE 23-13b
Cellular elements (45%)
Cell type
Number
Functions
3
per L (mm ) of blood
Erythrocytes
(red blood cells)
5–6 million
Centrifuged
blood
sample
Leukocytes
(white blood cells)
5,000–10,000
Transport of
oxygen (and
carbon dioxide)
Defense and
immunity
Lymphocyte
Basophil
Eosinophil
Neutrophil
Platelets
Monocyte
250,000–
400,000
Blood clotting
CONNECTION
23.14 Too few or too many red blood cells can be
unhealthy
• Red blood cells
– Circulate for 3 to 4 months
– Old cells are broken down and their
components are recycled
• Anemia
– An abnormally low amount of hemoglobin
or red blood cells
– Most commonly caused by iron deficiency
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• Red blood cell production
– Takes place in bone marrow
– Under control of a negative feedback
system
– Mediated by the hormone erythropoietin
• Increased red blood cell production is a
physiological adaptation to living at high
altitudes
– Athletes may try dangerous artificial
methods
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23.15 Blood clots plug leaks when blood vessels
are injured
• Blood clotting involves platelets, the plasma
protein fibrinogen, and clotting factors
• The clotting process
1. Platelets adhere to exposed connective
tissue
2. Platelet plug forms
3. Fibrinogen converted to fibrin, forms clot
that traps blood cells
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-15a
Platelets adhere to exposed
connective tissue
Platelet plug forms
Fibrin clot traps
blood cells
Epithelium
Connective tissue
Platelet
Platelet plug
• Blood-clotting malfunctions
– Hemophelia
• Inherited disease
• Blood doesn’t clot, and bleeding can
be fatal
– Thrombus
• Clot formed in the absence of injury
• Can break free and lodge in a vessel,
causing heart attack, stroke, or
pulmonary embolism
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CONNECTION
23.16 Stem cells offer a potential cure for blood
cell diseases
• Red bone marrow contains unspecialized stem
cells
– Differentiate to produce all blood cells
– Continually produce all the blood cells needed
throughout life
• Stem cells may be used to treat some blood
disorders such as leukemia, cancer of the white
blood cells
– Healthy bone marrow may be transplanted
from a donor
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
LE 23-16
Stem cells
Stem cells
Basophils
Erythrocytes
Platelets
Lymphocytes
Monocytes
Eosinophils
Neutrophils