Transcript Slide 1

The Living World
Fifth Edition
George B. Johnson
Jonathan B. Losos
Chapter 29
Circulation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
29.1 Open and Closed Circulatory
Systems
• Among the unicellular protists, oxygen and
nutrients are obtained directly by simple
diffusion
• Cnidarians and flatworms have cells that
are directly exposed to either the external
environment or to a body cavity that
functions in digestion, the gastrovascular
cavity
29.1 Open and Closed Circulatory
Systems
• Large animals have tissues that are
several cell layers thick so that many cells
are too far away for surface exchange
 instead, oxygen and nutrients are transported
from the environment and digestive cavity to
the body cells by an internal fluid within a
circulatory system
• there are two main types of circulatory systems
– open circulatory system
– closed circulatory system
29.1 Open and Closed Circulatory
Systems
• In open circulatory systems, there is no
distinction between the circulating fluid
(blood) and the extracellular fluid of the
body tissues (interstitial fluid or lymph)
 this fluid is called hemolymph
 insects have a muscular tube that serves as a
heart to pump the hemolymph through a
network of open-ended channels
29.1 Open and Closed Circulatory
Systems
• In a closed circulatory system, the circulating
fluid (blood) is always enclosed within blood
vessels that transport blood away from and back
to a heart
 annelids and all vertebrates have a closed circulatory
system
 as blood plasma passes through capillaries, the
pressure of the blood forces some fluid out of the
capillary walls
• this fluid is called interstitial fluid
– some of it will return to the blood but some becomes lymph
and travels through the lymph vessels
Figure 29.1 Three types of circulatory
systems found in the animal kingdom
29.1 Open and Closed Circulatory
Systems
• The functions of the circulatory system can be
divided into three areas
 transportation
• substances essential for cellular functions are transported by
the circulatory system
 regulation
• the cardiovascular system participates in heat exchange,
such as by countercurrent heat exchange
 protection
• The circulatory system protects again injury and foreign
microbes or toxins introduced into the body
Figure 29.2 Countercurrent heat
exchange
29.2 Architecture of the Vertebrate
Circulatory System
• The vertebrate circulatory system (also
known as the cardiovascular system) is
made up of three elements
 heart—a muscular pump that pushes blood
through the body
 blood vessels—a network of tubes through
which the blood moves
 blood—fluid that circulates through the
vessels
29.2 Architecture of the Vertebrate
Circulatory System
• Blood moves through the body in cycle, from the
heart, through a system of vessels
heart
veins
venules
arteries
arterioles
capillaries
29.2 Architecture of the Vertebrate
Circulatory System
• Although each capillary is very narrow,
there are so many of them that the
capillaries have the greatest total crosssectional area of any other type of blood
vessel
 capillary beds can be opened or closed based
on the physiological needs of the tissues
• precapillary sphincters can contract or relax and
affect whether blood flows into a capillary bed for
exchange of gases and metabolites
Figure 29.3 The capillary network
connects arteries with veins
29.2 Architecture of the Vertebrate
Circulatory System
• An artery is more than a simple pipe
 it needs to be able to expand with the pressure
caused by contraction of the heart
 for this reason, the layers of the arterial wall are
elastic
• Arterioles differ from arteries in that they are
smaller in diameter and respond to nervous and
hormonal stimulation
 they can constrict and limit blood flow during periods
of stress or low temperature
Figure 29.4 (a) The structure of
blood vessels
29.2 Architecture of the Vertebrate
Circulatory System
• Capillaries are where oxygen and food
molecules are transferred from the blood
to the body’s cells
 capillaries are narrow and have thin walls for
exchange
 almost all cells of the vertebrate body are no
more than 100 micrometers from a capillary
 the blood pressure is actually far lower in the
capillaries than in the arteries
Capillary Structure
Figure 29.4 (b) The structure of
blood vessels
Figure 29.5 Red blood cells within
a capillary
29.2 Architecture of the Vertebrate
Circulatory System
• Veins are vessels that return blood to the
heart
 the walls of veins are thinner because the
blood pressure is not great
 veins have unidirectional valves that prevent
the flow of blood backwards
Structure of Veins
Figure 29.4 (c) The structure of
blood vessels
Figure 29.6 Veins and arteries
Figure 29.7 Flow of blood
through veins
29.3 The Lymphatic System:
Recovering Lost Fluid
• The cardiovascular system is very leaky
 from capillary exchange, the body loses about
4 liters of fluid each day
 to collect and recycle this fluid, the body uses
a second circulatory system called the
lymphatic system
• the lymphatic system is also a network of vessels
filled with a fluid called lymph
• ultimately the lymph reenters the bloodstream into
veins in the neck
Figure 29.8 The human lymphatic
system
Figure 29.9 Lymphatic capillaries
reclaim fluid from interstitial fluid
29.3 The Lymphatic System:
Recovering Lost Fluid
• The lymphatic system has three important
functions
 it returns proteins to circulation
• if this protein remains in the tissues, it would cause
swelling or edema
 it transports fats absorbed from the intestine
 it aids in the body’s defense
• swellings along lymph vessels called lymph
nodes where lymph-borne bacteria and dead
blood cells are destroyed
29.4 Blood
• Blood plasma is a complex solution of water
with three kind of substances dissolved in it
 metabolites and wastes
• for example—glucose, vitamins, hormones, etc.
 salts and ions
• the chief plasma ions are sodium, chloride, and bicarbonate
 proteins
• proteins help keep water in the plasma
– serum albumin functions in maintaining osmotic balance
• other plasma proteins include antibodies, globulins, and
fibrinogen
– fibrinogen is required for blood clotting
Figure 29.10 Threads of fibrin
29.4 Blood
• Nearly half the volume of blood is
occupied by cells
 the three principal cell types are
• erythrocytes (red blood cells)
– hematocrit is the fraction of the total volume of the blood
that is occupied by red blood cells
– in humans, the hematocrit is usually about 45%
• leukocytes (white blood cells)
• platelets
29.4 Blood
• Erythrocytes resemble flat disks with a
central depression on both sides
 almost the entire interior is packed with
hemoglobin, which carries oxygen
 because these cells have no nucleus they are
short-lived and must be replaced by new cells
synthesized in the bone marrow
29.4 Blood
• leukocytes contain no hemoglobin and are
essentially colorless
 there are several different kinds, all of which
help defend the body against invading
microorganisms and other foreign substances
• Platelets are cell fragments, pinched from
large cells in the bone marrow, called
megakaryocytes, that play a key role in
clotting
Figure 29.11 Types of blood cells
29.5 Fish Circulation
• The evolution of gills by fishes required a more
efficient pump, a true chamber-pump heart
 the fish heart is essentially a tube with fours
chambers arrayed one after another
• the first two chambers are collecting chambers while the
second two chambers are pumping chambers
• the chambers contract in a peristaltic sequence
• the blood that is pumped to the body is fully oxygenated
because it passes through the gills first
Figure 29.12 The heart and
circulation of a fish
29.6 Amphibian and Reptile
Circulation
• The advent of lungs involved a major
change in the pattern of circulation
 after blood is pumped by the heart to the
lungs, it does not go directly to the tissues of
the body but instead returns to the heart
• pulmonary circulation goes to and from the heart
and lungs
• systemic circulation goes to and from the heart
and the rest of the body
29.6 Amphibian and Reptile
Circulation
• The amphibian heart has structural
features to prevent the mixing of
deoxygenated and oxygenated blood
 the atrium is divided by a septum that
separates the blood coming from the body
and from the lungs
 some species of amphibians have folds in the
ventricle that direct the flow of blood from the
atria
 the conus arteriosus is branched
Figure 29.13 The amphibian heart
and circulation in reptiles
29.6 Amphibian and Reptile
Circulation
• Amphibians in water supplement the
oxygenation of their blood by obtaining
additional oxygen by diffusion across their
skin
 this is called cutaneous respiration
• The reptilian heart is additionally
specialized by having a partial septum in
the ventricle
29.7 Mammalian and Bird
Circulation
• mammals, birds, and crocodiles have a
four-chambered heart with two complete
pumping circuits
 this increased efficiency of the double
circulation in mammals and birds may have
been important in the evolution of endothermy
• more efficient circulation is necessary to support
the high metabolic rate required
Figure 29.14 (a) The heart and
circulation of mammals and birds
29.7 Mammalian and Bird
Circulation
• The contraction of the heart consists of a
carefully orchestrated series of muscle
contractions
 first the atria contract, followed by the ventricles
• The sinoatrial (SA) node in the wall of the right
atrium is the site where each heartbeat
originates
 it is the pacemaker of the heart and determines the
rhythm of the heart’s beating
29.7 Mammalian and Bird
Circulation
• Contraction of the atria is initiated by the
SA node
• The wave of depolarization does not
immediately spread to the ventricles
because it must pass first through the
atrioventricular (AV) node
 this delays the signal for about 0.1 sec until
the atria have finished contracting
29.7 Mammalian and Bird
Circulation
• The ventricles finally contract after the signal
passes from the AV node to an atrioventricular
bundle called the bundle of His
• The bundle branches and divides into fastconducting Purkinje fibers which initiate the
almost simultaneous contraction of the right and
left ventricles
• The electrical activity of the heart can be
measured by a recording called an
electrocardiogram (ECG or EKG)
Figure 29.15 How the mammalian
heart contracts
29.7 Mammalian and Bird
Circulation
• The simplest way to monitor heartbeat is to
listen using a stethoscope
 “lub” is sound made by the closing of the bicuspid
and tricuspid valves at the start of ventricular
contraction
 “dub” is the sound made by the closing of the
pulmonary and aortic valves at the end of ventricular
contraction
• A heart murmur is heard due to turbulence
created by the valves not closing fully
29.7 Mammalian and Bird
Circulation
• Another way to examine the events of the
heartbeat is to monitor the blood pressure
 a device called a sphygmomanometer is used
to measure the blood pressure in the brachial
artery of the arm
 diastolic pressure is the low pressure when
the atria are filling
 systolic pressure is the high pressure
associated with the ventricles contracting
Figure 29.16 Measuring blood
pressure
29.8 Cardiovascular Diseases
• Cardiovascular diseases are the leading
cause of death in the US
 heart attacks result from an insufficient
supply blood reaching one or more parts of
the heart
• angina pectoris, or chest pains, may signal that
the blood supply to the heart is inadequate
 strokes are caused by an interference with
the blood supply to the brain
29.8 Cardiovascular Diseases
• Atherosclerosis is an accumulation within
the arteries that cause a reduction in blood
flow
• Arteriosclerosis is a hardening of the
arteries when calcium is deposited in
arterial walls
 because they are not elastic, the heart has to
work harder
Figure 29.17 The path to a heart
attack
29.8 Cardiovascular Diseases
• There are many possible treatments for
blocked coronary arteries
 non-invasive
• drugs, such as enzymes, that breakdown clots or
anticoagulants that prevent clots from forming
• nitroglycerin to cause blood vessels to dilate
 invasive
• angioplasty/stent
• coronary bypass
• heart transplant
Inquiry & Analysis
• All mammals have the
same size hearts relative
to their body size. Do
their hearts beat at the
same rate?
• What general statement
can be made regarding
the effect of body size on
heart rate in mammals?
Graph of the Effect of Body Size
on Heart Rate in Mammals