Ch 32 & 33 lecture

Copyright © 2009 Pearson Education, Inc..
Lectures by
Gregory Ahearn
University of North Florida
Chapters 32,33
Circulation and
Respiration

Copyright © 2009 Pearson Education Inc.
What Are The Major Features And
Functions Of Circulatory Systems?
 A circulatory system evolved in multicellular
animals to bring the external world to each
metabolizing cell in the animal, so that
nutrients, oxygen, and waste products could
be exchanged.

 Circulatory systems have three main
components:
• Blood
• Blood vessels
• Heart
 Animals have two types of circulatory
systems:
• Open circulatory system
• Closed circulatory system

systems (continued).
• In an open circulatory system, blood flows
through blood vessels, but at some point,
leaves the vessels and moves freely through
tissues and a large space called a hemocoel.

 Open circulatory system
Fig. 20-1a
heart
blood
bathes internal
organs
blood
vessels
hemocoel
opening
with valves
tubular
hearts
Open circulatory system(a)

 Some invertebrates, including earthworms,
and all vertebrates have closed circulatory
systems, where blood is confined to blood
vessels and flows through them in a
continuous circuit.

 Closed circulatory system
Fig. 20-1b
heart
extracellular fluid
vessels branch in
each organ
hearts
vessel
small vessels
Closed circulatory system(b)

PLAYPLAY Animation—Open vs. Closed Circulatory Systems

• In closed circulatory systems of vertebrates,
vessels that carry blood away from the heart
are called arteries.
• Arteries carry blood to the smallest blood
vessels, called capillaries, which are
microscopic vessels that penetrate tissues.

• Dissolved substances in the blood exchange
with those in the fluid surrounding capillaries,
which is called extracellular fluid.
• After passing through capillaries, blood moves
back toward the heart through vessels called
veins.

 The vertebrate circulatory system transports
many substances.
• Transports oxygen from the lungs or gills to
the tissues
• Transports carbon dioxide from the tissues to
the lungs or gills
• Transports nutrients from the digestive system
to the tissues
• Transports waste products and toxic
substances to the liver and the kidney for
excretion

 The vertebrate circulatory system transports
many substances (continued).
• Transports hormones from the glands and
organs that produce them to the tissues on
which they act
• Helps to regulate body temperature by
adjusting blood flow
• Helps to protect the body from bacteria and
viruses by circulating the cells and molecules
of the immune system

How Does The Vertebrate Heart Work?
 The vertebrate heart consists of muscular
chambers.
• In vertebrate hearts, muscular chambers,
called atria, collect blood.
• Blood flows from the atria to the ventricles,
chambers whose contractions circulate blood
through the body.
• The number of atria and ventricles differs
among different classes of vertebrates.

 Fish hearts have two chambers, one atrium,
and one ventricle; blood flows through the
fish body in a single loop.

 Fish heart
Fig. 20-2aFish
gill capillaries
body capillaries
ventricle
atrium
(a)

 Amphibians and most reptiles have three-
chambered hearts and two circulatory loops,
one for the lungs and one for the rest of the
body.
 Blood from both circuits mixes in the heart;
therefore, the two circuits are not completely
separate.

 Amphibian, and most reptiles’ heart
Fig. 20-2b
Amphibians, most reptiles
lung capillaries
atria
ventricle
body capillaries
(b)

 In alligators, crocodiles, birds, and
mammals, the heart has four chambers,
and the two circulatory loops are completely
separate.

 Mammals and birds’ heart
Fig. 20-2cMammals, birds
lung capillaries
body capillaries
atria
ventricle
(c)

Animation—Vertebrate HeartPLAYPLAY

 Four-chambered hearts, like the human
heart, can be thought of as two separate
pumps.
• One pump, consisting of the right atrium and
right ventricle, pumps oxygen-depleted blood
to the lungs.
• The other pump, consisting of the left atrium
and left ventricle, moves oxygen-rich blood
from the lungs and through the aorta to the
rest of the body.

 The human heart and its valves and vessels
Fig. 20-3
aorta
left atrium
pulmonary artery
(to left lung)
semilunar valves
pulmonary veins
(from left lung)
atrioventricular
valve
left ventricle
thicker muscle
of left ventricle
descending aorta
(to lower body)right ventricle
inferior vena cava
atrioventricular valve
superior
vena cava
pulmonary artery
(to right lung)
pulmonary veins
(from right lung)
right atrium

 The atria and ventricles contract in a
coordinated way.
• The chambers of the heart alternatively
contract and relax.
• The two atria contract at the same time,
emptying their contents into the ventricles.
• A fraction of a second later, the two ventricles
contract, forcing blood into arteries that exit
the heart.
• Both atria and ventricles then relax briefly, and
the cycle repeats.

 The cardiac cycle
Fig. 20-4
Atria contract, forcing
blood into the ventricles
Then the ventricles
contract, forcing blood
through the arteries to the
lungs and the rest of the body
The cycle ends
as the heart relaxes
Deoxygenated blood is
pumped to the lungs
Blood fills the
atria and begins
to flow passively
into the ventricles
Deoxygenated
blood from the
body enters the
right ventricle
Oxygenated blood from the
lungs enters the left ventricle
Oxygenated blood
is pumped to the
body

Animation—Function of the Human HeartPLAYPLAY

 The atria and ventricles contract in a
coordinated way (continued).
• At a normal resting heart rate, the cycle lasts
about 1 second.
• Blood pressure changes as the cycle
proceeds.
• Systolic pressure is measured during
ventricular contraction, and diastolic pressure
is measured between contractions.

 Measuring blood pressure
Fig. 20-5
A stethoscope
detects
pulse sounds
The cuff is inflated,
putting pressure
on the artery
cuff

Animation—Measuring Blood PressurePLAYPLAY

 Valves prevent blood from moving in the
wrong direction.
• When the ventricles contract, blood must
move only out through the arteries and not
back into the atria.
• Once blood has left the ventricles and entered
the arteries, it must be prevented from flowing
back as the heart relaxes.

 Valves prevent blood from moving in the
wrong direction (continued).
• These needs are met by four one-way valves.
• Atrioventricular valves separate the atria
from the ventricles.
• Semilunar valves allow blood to enter the
pulmonary artery and the aorta when the
ventricles contract.

 Electrical impulses coordinate the sequence
of contractions.
• Contractions are coordinated by the
pacemaker, a cluster of specialized heart
muscle cells that produce spontaneous
electrical signals.
• The heart’s primary pacemaker is the
sinoatrial (SA) node, located in the wall of the
right atrium.

of contractions (continued).
• From the SA node, an electrical impulse
creates a wave of muscular contraction that
spreads through the right and left atria until it
arrives at the unexcitable tissue between the
atria and ventricles.
• There, the excitation is channeled through the
atrioventricular (AV) node.

of contractions (continued).
• From the AV node, the signal to contract
spreads along excitable fibers to the base of
the two ventricles.
• This signal causes the ventricles to contract in
unison.
• If the pacemaker fails, uncoordinated irregular
contractions, called fibrillation, occurs, and
blood cannot be pumped out of the heart.

 The heart’s pacemaker and its connections
Fig. 20-6
Unexcitable tissue
separates the atria
and ventricles
AV node
The sinoatrial node
electrical signal starts
the atrial contraction
The atrioventricular
node transmits the
signal to the ventricles
with a slight delay
The signal travels to
the base of the ventricles
Excitable fibers transmit
the signals to ventricular
cardiac muscle, causing
contraction from the base
upwards
The signal spreads,
causing the atria to
contract
excitable
fibers

 The heart’s contractions result from
movement of filaments in muscle cells.
• The muscle tissue that makes up the heart
consists of cells known as muscle fibers.
• Each muscle fiber contains many myofilbrils,
cylindrical structures that extend from one end
of the fiber to the other.
• The myofibrils are composed of subunits
called sarcomeres, which are aligned end to
end long the length of the myofibril.

 A muscle fiber
Fig. 20-7a,b
myofibril
membrane
Cross section of fiber(a)
musclefiber
sarcomere
myofibril
thin filament
Z lines
Myofibril and sarcomere
thick filament
(b)

 Within each sarcomere is a precise
arrangement of filaments of the proteins
actin and myosin; actin forms the thin
filaments, and myosin forms the thick
filaments.
Fig. 20-7c
Thick and thin filaments
thin filament
thick filament
(myosin)
cross-bridge
actin
accessory
proteins
(c)

 The heart’s contractions result from
movement of filaments in muscle cells
(continued).
• The thin filaments are attached to fibrous
protein bands called Z lines, which separate
adjacent sarcomeres.
• During contraction, the myosin filaments make
contact with the actin filaments and, using
ATP energy, pull the actin strand past the
myosin strand, shortening the sarcomere and
contracting the muscle.

 Muscle contraction
Fig. 20-8
Relaxed
muscle
Contracted
muscle
z line
sarcomere
A sarcomere shortensCross-bridge attachment and release
thick filament
binding sites
cross-bridge
ATP
thin filament
(b)(a)
When binding
sites are exposed,
cross-bridges
attach to the
binding sites
The cross-
bridges bend,
moving the
filaments past
one another and
shortening the
sarcomere
Using energy from
ATP, the cross-bridges
release, straighten, and
reattach farther along

Muscle Contraction
Suggested Media Enhancement:
Muscle Contraction
To access this animation go to folder C_Animations_and_Video_Files
and open the BioFlix folder.

What Is Blood?
 Blood transports dissolved nutrients, gases,
hormones, and wastes through the body.
• It has two major components:
• A fluid, called plasma
• Cellular components—including red blood
cells, white blood cells, and platelets—
which are suspended in the plasma
• The cellular components are produced in
bone marrow and later move into the blood.

What Is Blood?
 Blood cells
Fig. 20-9
platelets
megakaryocyte
neutrophil neutrophil
basophil
monocyte
eosinophil
lymphocyte
red blood cells
Erythrocytes White blood cells
Megakaryocyte forming platelets
(a) (b)
(c)

What Is Blood?
 Plasma is primarily water and dissolved
substances.
• Plasma is 90% water.
• Dissolved in the plasma are proteins,
hormones, nutrients, salts, and wastes, such
as urea.

What Is Blood?
 Red blood cells carry oxygen from the lungs
to the tissues.
• The most abundant cells in the blood are red
blood cells.
• Red blood cells get their red color from
hemoglobin, an iron-containing protein that
can bind up to four oxygen molecules.
• Hemoglobin picks up oxygen in the lungs,
where oxygen is at high concentration, and
releases it in other tissues of the body, where
the oxygen concentration is low.

What Is Blood?
 White blood cells help defend the body
against disease.
• White blood cells, or leukocytes, make up less
than 1% of blood cells but play a key role in
the body’s resistance to disease.
• There are five types of white blood cells:
• Neutrophils
• Eosinophils
• Basophils
• Lymphocytes
• Monocytes

What Is Blood?
 Lymphocytes are responsible for the
immune response against disease.
• Neutrophils and monocytes engulf foreign
particles.
Fig. 20-10

What Is Blood?
 Platelets are cell fragments that aid in blood
clotting.
• Platelets are pieces of large cells, called
megakaryocytes, that occur in the bone
marrow and enter the blood, playing a key role
in blood clotting.
• Blood clotting starts when platelets contact an
irregular surface, such as a damaged blood
vessel, where they partially block the opening.

What Is Blood?
 The platelets and injured tissue initiate a
complex sequence of reactions among
plasma proteins, which results in a fibrous
network, called fibrin, that traps red blood
cells and closes the wound.
Fig. 20-11
platelets white blood cell
red blood cell
fibrin strands

What Are The Types And Functions Of
Blood Vessels?
 As it leaves the heart, blood travels from
arteries to arterioles to capillaries to venules
to veins, and finally, it returns to the heart.

Fig. 20-12
jugular vein
aorta
superior
vena cava
carotid artery
lung
capillaries
pulmonary
artery
heart
kidney
femoral vein
intestine
inferior
vena cava
liver
femoral artery

 Arteries and arterioles carry blood away
from the heart.
• These vessels have thick walls embedded
with smooth muscle and elastic connective
tissue.
• Arteries branch into
vessels of small
diameter called
arterioles.
precapillary
sphincters
arteriole
venule
artery vein
capillary
valve
smooth muscle
connective tissue
smooth
muscle
cross
section
capillary
network
Blood Vessels?
Fig. 20-13

Blood Vessels?
 Structures and interconnections of blood
vessels
Fig. 20-13
precapillary
sphincters
arteriole
venule
artery vein
capillary
valve
smooth muscle
connective tissue
smooth
muscle
cross
section
capillary
network

Blood Vessels?
 Capillaries are microscopic vessels through
which nutrients and wastes are exchanged.
• Diffusion of nutrients and wastes occurs in
capillaries, the smallest of all blood vessels.
• Because their walls are only one cell thick,
substances can cross a capillary cell’s plasma
membrane and easily move into or out of
capillaries.

Blood Vessels?
 Capillaries are microscopic vessels through
which nutrients and wastes are exchanged
(continued).
• Capillaries are so narrow that red blood cells
pass through them in single file.
• The speed of blood flow drops very quickly as
it moves through this narrow capillary network.
• The flow of blood in capillaires is regulated by
tiny rings of smooth muscle, called
precapillary sphincters, which surround the
junctions between arterioles and capillaries.

Blood Vessels?
 Red blood cells flow through a capillary.
Fig. 20-14
Red blood cells must
pass through capillaries
in single file
Capillary walls are thin
and permeable to gases,
nutrients, and cellular
wastes

Blood Vessels?
 Venules and veins carry blood back to the
heart.
• After picking up carbon dioxide and other
cellular wastes from cells, capillary blood
drains into larger vessels called venules,
which empty into larger veins.
• To prevent blood from flowing away form the
heart, veins are equipped with valves that
allow blood to flow in only one direction.

Blood Vessels?
 Blood pressure is low in veins and
contraction of skeletal muscle during
exercise helps return blood to the heart by
squeezing the veins and forcing blood
through them.

Blood Vessels?
 Valves direct the
flow of blood in
veins.
Fig. 20-15
valve
closed
valve
closed
valve
open
relaxed
muscle
muscle
contraction
compresses
vein

How Does The Lymphatic System Work
With The Circulatory System?
 The lymphatic system consists of:
• A network of lymph vessels that empty into
the circulatory system
• Numerous small lymph nodes
• The thymus
• The spleen

 The lymphatic system removes excess fluid
and dissolved substances that leak from the
capillaries.
• It transports fats from the small intestine to the
blood stream.
• It defends the body by exposing bacteria and
viruses to white blood cells.

Fig. 20-16
thoracic duct enters a
vein to the vena cava
thymus
heart
spleen
thoracic duct
valve prevents
backflow
lymph node
chambers
packed with
white blood cells
superior
vena cava
lymph
vessels
lymph
nodes

 Lymphatic vessels resemble the capillaries
and veins of the circulatory system.
• The smallest lymph vessels are lymph
capillaries.
• Lymph capillary walls have specialized
openings between the cells that act as one-
way valves.
• These openings allow large particles to be
carried into the lymph capillaries along with
fluid.

 Lymphatic vessels resemble the capillaries
and veins of the circulatory system
(continued).
• Materials collected in the lymph flow into
larger lymph vessels.
• The direction of flow in lymph vessels is
regulated by one-way valves.

 Lymph capillary structure
Fig. 20-17
extracellular
fluid
lymph
vessel
Pressure forces
fluid from plasma at
the arteriole end of
the capillary network
Extracellular fluid
enters lymph vessels
and the venous ends
of capillaries
Lymph is transported
into larger lymph vessels
and back to the
bloodstream

 The lymphatic system returns fluids to the
blood.
• The lymphatic system collects excess fluid
that leaks out of the blood capillaries and
returns it to the blood.
• As extracellular fluid accumulates, its pressure
forces the fluid through the one-way opening
in the lymph capillary walls.
• Once inside lymphatic vessels, the excess
fluid taken up is now called lymph.

 The lymphatic system transports fats from
the small intestine to the blood.
• After a fatty meal, the cells of the small
intestine absorb globules of digested fat.
• These globules are too large to diffuse into
blood capillaries, but they easily move into
openings between lymph capillary cells.
• They are later deposited into the superior
vena cava that enters the heart.

 The lymphatic system helps defend the
body against disease.
• In the lymph nodes, lymph is forced through
channels that are lined with masses of white
blood cells that recognize and destroy foreign
particles, such as bacteria or viruses.
• The thymus and spleen are considered part of
the lymphatic system.

 The lymphatic system helps defend the
body against disease (continued).
• Certain types of white cells mature in the
thymus.
• The spleen is another white blood cell-
producing organ, which also filters blood,
exposing it to white blood cells that destroy
foreign particles and aged red blood cells.

How Are Oxygen And Carbon Dioxide
Exchanged In Animal Bodies?
 The process by which the body acquires
oxygen from the environment and delivers
carbon dioxide back to it is called
respiration.
• Although animal respiration systems are
diverse, they all rely on diffusion of gases
across a respiratory surface.
• Respiratory surfaces are large and moist; they
must remain moist because gases must be
dissolved in water in order to diffuse into or
out of cells.

 Aquatic animals may have gills.
• For some small aquatic animals, gases are
exchanged across their body surface.
• Most larger animals have specialized
respiratory structures; many have gills, which
are elaborately folded to increase their surface
area.

 Aquatic animals may have gills (continued).
• Fish pump oxygen-rich water into the mouth
and over the gills, ejecting it through an
opening just behind the gills.
• Fish gills have a series of filaments that are
covered with capillary-filled lamellae where
gases are exchanged.

 Gills exchange gases with water.
Fig. 20-19
Water flows over gills Gill structure Lamella
water
in
gill arch
water out
(protective
flap
removed)
gill filament
gill arch
lamellae
lamella
water flow blood flow
capillaries
deoxygenated
blood
oxygenated
blood
(a) (b) (c)

 Terrestrial animals have internal respiratory
structures.
• In land animals, the respiratory structures are
lungs.
• Lungs are chambers containing moist gas-
exchange membranes that are protected
within the body, where water loss is
minimized.

How Does The Human Respiratory
System Work?
 There are two parts to the human
respiratory system:
• The conducting portion
• The gas exchange portion

System Work?
 The conducting portion brings air to the
lungs.
• Air enters through the nose or mouth, passes
through the nasal cavity or oral cavity into the
pharynx, then travels through the larynx.
• Both food and air pass through the pharynx;
the epiglottis is a flap of tissue that covers the
larynx when food is being swallowed,
preventing it from going into the trachea and
on to the lungs.

System Work?
 The human respiratory system
Fig. 20-20aHuman respiratory system
diaphragm
nasal cavity
pharynx
oral cavity
epiglottis
larynx
esophagus
trachea
rings of
cartilage
pulmonary vein
pulmonary artery
bronchi
bronchioles
(a)

System Work?
 The conducting portion brings air to the
lungs (continued).
• Inhaled air continues past the larynx into the
trachea, which is a flexible tube whose walls
are reinforced with semicircular bands of stiff
cartilage.
• The trachea splits into two bronchi, which
continue to branch more and to get smaller
with each branch until they become
bronchioles.
• Bronchioles are connected to groups of small
air sacs called alveoli.

System Work?
 Alveoli with capillaries
Fig. 20-20b
Alveoli with capillaries
bronchiole
pulmonary venule
alveoli
capillary
network
pulmonary arteriole
(b)

System Work?
 Gas exchange occurs in the alveoli.
• Both the alveolar wall and the adjacent
capillary walls are only one cell thick, so the
air in the lungs is extremely close to the blood
in the capillaries.
• A thin layer of watery fluid lines each alveolus.

from
pulmonary
artery
alveolar
membrane
respiratory
membrane
to pulmonary vein
(air) CO2
O2
capillary
fluid
Oxygen diffuses
into red blood cells
Carbon dioxide
diffuses into alveolus
System Work?
 Gases dissolve in this fluid and diffuse
through the alveolar and capillary
membranes.
Fig. 20-21

System Work?
 Oxygen diffuses from the air in the alveoli,
where its concentration is high, into the
blood, where its concentration is low; the
flow of carbon dioxide is opposite to that of
oxygen.

Air moves in Air moves out
Rib cage
contracts Lungs
compress
Diaphragm
relaxes upward
Diaphragm
contracts downward
Rib cage
expands Lungs
expand
Inhalation Exhalation(a) (b)
Fig. 20-23
System Work?
 The mechanics of breathing

System Work?
 An overview of
gas exchange
Fig. 20-22
CO2
alveoli
(air sacs)
Oxygenated blood
Deoxygenated blood
Gases move in and out
of the lungs by breathing
O2 and
CO2 are
exchanged
in the lungs
by diffusion
Gases
dissolved in
blood are
transported
by the
circulatory
system
O2
left ventricle
O2 and CO2
are exchanged
in the tissues
by diffusion
right
atrium
right
ventricle
left
atrium
O2
O2
O2
CO2
O2
CO2
CO2
CO2
CO2 CO2
O2

System Work?
Animation—Gas ExchangePLAYPLAY

System Work?
 Carbon dioxide and oxygen are transported
in different ways.
• Almost all of the oxygen transported in blood
is bound to hemoglobin molecules in red
blood cells.
• Hemoglobin only carries about 20% of the
carbon dioxide in the blood; the remainder is
carried by two processes.
• About 10% is dissolved in the plasma.
• About 70% is converted to bicarbonate ions
(HCO3
–
) for transport.

System Work?
 Carbon dioxide and oxygen are transported
in different ways (continued).
• Bicarbonate is formed between water and
carbon dioxide in the presence of carbonic
anhydrase, which is in the red blood cells:
CO2 + H2O  H+
+ HCO3
–

System Work?
 The lungs are protected in an airtight cavity.
• The chest cavity that surrounds the lungs is
airtight.
• It is bounded by neck muscles and connective
tissue on top, and by the dome-shaped
muscular diaphragm on the bottom.
• Within the wall of the chest, the rib cage
surrounds and protects the lungs.

System Work?
 Air is inhaled actively and exhaled
passively.
• We breathe in two stages:
• Inhalation, when air is actively drawn into
the lungs
• Exhalation, when it is passively expelled
from the lungs

System Work?
 Inhalation is accomplished by enlarging the
chest cavity.
• The diaphragm muscles contract, drawing the
diaphragm downward.
• The rib muscles also contract, lifting the ribs
up an outward.
• When the chest cavity expands, the lungs
expand with it and increase their volume, but
lower the air pressure inside.
• The air then flows from high pressure outside
to low pressure inside.

System Work?
 Inhalation
Fig. 20-23a
Air moves in
Diaphragm
contracts downward
Rib cage
expands Lungs
expand
Inhalation(a)

System Work?
 Exhalation occurs automatically when the
muscles that cause inhalation are relaxed.
• The relaxed diaphragm domes upward, and
the ribs move down and inward, decreasing
the size of the chest cavity and forcing air out
of the lungs.

System Work?
 Exhalation
Fig. 20-23b
Air moves out
Rib cage
contracts Lungs
compress
Diaphragm
relaxes upward
Exhalation(b)

System Work?
 Breathing rate is controlled by the
respiratory center of the brain.
• Each contraction of the respiratory muscles is
stimulated by impulses from nerve cells.
• The impulses originate in the respiratory
center of the brain, which is located in the
medulla, the part of the brain just above the
spinal cord.

System Work?
 Breathing rate is controlled by the
respiratory center of the brain (continued).
• Nerve cells in the respiratory center generate
cyclic bursts of impulses that cause
alternating contraction and relaxation of the
respiratory muscles.
• The respiratory rate is regulated to maintain a
constant level of carbon dioxide in the blood,
as monitored by carbon dioxide receptors in
the medulla.

Ch 32 & 33 lecture

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