Circulation and Respiration
Chapter 44
Open and Closed
Circulatory Systems
Characteristics of
Blood Vessels
The Lymphatic System
The Fish Heart
Amphibian and Reptile
Mammalian and Bird
Cardiac Cycle
How Animals Maximize
Rate of Diffusion
– Gills
– Air-Breathing
– Amphibians and
– Mammals
– Birds
Structures and
Mechanisms of
Open and Closed Circulatory Systems
Open and closed circulatory systems
– open - no distinction between circulating
fluid and extracellular body fluid
 hemolymph
– closed - Circulating fluid is always
enclosed within blood vessels that
transport blood away from, and back to, a
pump (heart).
Open and Closed Circulatory Systems
Functions of vertebrate circulatory system
– Functions in transporting oxygen and
nutrients to tissues by the cardiovascular
 Arteries carry blood away from the
 Veins return blood to the heart.
 Capillaries carry blood from the
arterial to the venous system.
Open and Closed Circulatory Systems
Principal functions
– transportation
 respiratory - erythrocytes transport
oxygen to tissue cells
 nutritive - absorbed food
 excretory - metabolic wastes
Open and Closed Circulatory Systems
 hormone transport
 temperature regulation
 endotherms
 counter-current heat exchange Vessels carrying warm blood from
deep within the body pass next to a
vessel carrying cold blood from the
surface of the body.
Countercurrent Heat Exchange
Open and Closed Circulatory Systems
– blood clotting
– immune defense
Plasma is the matrix in which blood cells and
platelets are suspended.
– Plasma contains solutes:
 metabolites, wastes, and hormones
 ions
 proteins
 albumin
 globulins
 fibrinogen
 serum
Blood Cells
Erythrocytes and oxygen transport
– hematocrit - fraction of total blood volume
occupied by erythrocytes
 Erythrocytes develop from
unspecialized cells (stem cells).
 New erythrocytes are constantly
formed in the bone marrow.
Blood Cells
Leukocytes defend the body
– Less than 1% of the cells in the human body
are leukocytes.
 granular leukocytes
 neutrophils, esinophils, and basophils
 nongranular leukocytes
 monocytes and lymphocytes
Blood Cells
Platelets help blood to clot
– Platelets accumulate at an injured site and
form a plug by sticking to each other and to
the surrounding tissues.
 reinforced by threads of protein (fibrin)
Blood Clotting
Characteristics of Blood Vessels
Blood leaves heart through arteries
– Arterioles are the finest microscopicallysized branches of the arterial tree.
 Blood from arterioles enters capillaries.
 Blood is collected in venules that lead
to larger vessels, veins, that carry
blood back to the heart.
Structure of Blood Vessels
Characteristics of Blood Vessels
Arteries and arterioles
– Contraction of smooth muscle layer of
arterioles results in vasoconstriction which
greatly increases resistance and
decreases blood flow.
– Relaxation of smooth muscle layer results
in vasodilation, decreasing resistance and
increasing blood flow.
 Some organs are regulated by
precapillary sphincters.
Characteristics of Blood Vessels
Venules and veins
– made up of same tissue layers as arteries,
but have thinner layer of smooth muscles
 Pressure in veins is only about onetenth that in arteries.
 Skeletal muscles surrounding veins can
contract to move blood by squeezing the
 venous valves
One-Way Blood Flow
The Lymphatic System
Lymphatic system consists of lymphatic
capillaries, lymphatic vessels, lymph nodes,
and lymphatic organs.
– Excess fluid in the tissues drains into the
blind-end lymph capillaries.
 Lymph passes into progressively larger
vessels with one-way valves.
 encounters lymphocytes
Evolution of Circulatory and Respiratory Systems
Fish heart
– Gills required a more efficient pump.
 First two chambers sinus venosus and
atrium are collection chambers.
 Second two chambers ventricle and
conus arteriosus are pumping
 Heartbeat is peristalic sequence.
The Fish Heart
Greatest advantage is that the blood passing
through the gills is fully oxygenated when it
moves into the tissues.
Greatest limitation is that in passing through
the gills, blood loses much of its pressure
developed by contraction of the heart.
– Limits rate of oxygen delivery to the rest of
the body.
Amphibian and Reptile Circulation
After blood is pumped by the heart through
the pulmonary arteries to the lungs, it is
returned to the heart via pulmonary veins.
– results in two circulations:
 pulmonary circulation - between heart
and lungs
 systemic circulation - between heart and
rest of the body
Heart and Circulation of a Fish
Amphibian and Reptile Circulation
Oxygenated blood from the lungs is kept
relatively separate from the deoxygenated
blood from the rest of the body due to
incomplete divisions within the heart.
– Amphibians in water can obtain additional
oxygen by diffusion through their skin.
 cutaneous respiration
Heart and Circulation of an Amphibian
Mammalian and Bird Hearts
Mammals, birds, and crocodiles have a fourchambered heart with two separate atria and
two separate ventricles.
– Right atrium receives deoxygenated blood
from the body and delivers it to the right
ventricle, which pumps it to the lungs.
– Left atrium receives oxygenated blood
from the lungs and delivers it to the left
ventricle, which pumps the oxygenated
blood to the rest of the body.
Heart and Circulation of Mammals and Birds
The Cardiac Cycle
The heart has two pairs of valves.
Atrioventricular (AV) valves guards the
opening between the atria and the ventricles.
– right - tricuspid valve
– left - bicuspid valve
Semilunar valves guard the exits from the
ventricles to the arterial system.
– right - pulmonary valve
– left - aortic valve
The Cardiac Cycle
Valves open and close as the heart goes
through the cardiac cycle of rest (diastole)
and contraction (systole).
– Right and left pulmonary arteries deliver
oxygenated blood to the right and left
 Return blood to left atrium via
pulmonary veins.
Passage of blood through the heart
Superior and inferior vena cavae bring O2-poor blood to
the right atrium
Blood flows through tricuspid valve to right ventricle
From right ventricle blood passes through the pulmonary
valve to the pulmonary artery
Blood picks up oxygen in the lungs and returns to the
heart through the pulmonary veins
Pulmonary veins empty oxygenated blood into the left
Blood flows through the mitral valve to the left ventricle
From the left ventricle blood flows through the aortic
valve to the aorta
Aorta carries blood out to the body
The Cardiac Cycle
Aorta and all its branches are systemic
arteries, carrying oxygen-rich blood from left
ventricle to the rest of the body.
Coronary arteries supply the heart muscle
Superior vena cava drains the upper body.
Inferior vena cava drains the lower body.
– Empty right atrium and complete
systematic circulation.
The Cardiac Cycle
Measuring arterial blood pressure
– Systolic pressure is peak pressure during
ventricular systole.
– Diastolic pressure is minimum pressure
between heartbeats.
 Blood pressure is written as a ratio of
systolic over diastolic pressure.
Measurement of Blood Pressure
Electrical Excitation and Contraction of the Heart
Contraction of heart muscle is stimulated by
membrane depolarization.
– Depolarization triggered by sinoatrial (SA)
 Acts as a pacemaker for the rest of the
heart by producing depolarization
impulses spontaneously at a particular
Electrical Excitation and Contraction of the Heart
Atrioventricular (AV) node allows
depolarization to pass to the ventricles.
– Depolarization is conducted rapidly over
both ventricles by atrioventricular bundle
(bundle of His).
 transmitted by Purkinje fibers
Electrical Excitation and Contraction of the Heart
Electrical activity recorded on an
electrocardiogram (EKG or ECG).
– First peak (P) is produced by
depolarization of atria (atrial systole).
– Second peak (QRS) produced by
ventricular depolarization (ventricular
– Last peak (T) produces by ventricular
Electrical Excitation in the Heart
Blood Flow and Blood Pressure
Cardiac output
– volume of blood pumped by each ventricle
per minute
 increases during exercise because of an
increase in heart rate and stroke volume
Blood pressure and baroreceptor reflex
– Arterial blood pressure depends on two
 cardiac output
 resistance to flow
Blood Flow and Blood Pressure
Baroreceptors detect changes in arterial
blood pressure.
– Activate sensory neurons that relay
information to cardiovascular control
 When blood pressure falls, they
stimulate neurons causing arteriole to
constrict and raise blood pressure.
Blood Flow and Blood Pressure
Blood volume reflexes involve effects of four
– antidiuretic hormone
– aldosterone
– atrial natriuretic hormone
– nitric oxide
Blood Flow and Blood Pressure
Cardiovascular diseases
– Cardiovascular diseases are the leading
cause of death in the United States.
 insufficient supply of blood reaching one
or more parts of the body
 angina pectoris - chest pain
 heart attacks – MI -blocked arteries
 strokes – CVA - interference with
blood supply to the brain
Blood Flow and Blood Pressure
Atherosclerosis - accumulation within the
arteries of fatty materials and various kinds
of cellular debris
Arteriosclerosis - hardening of the arteries
– occurs when calcium is deposited in
arterial walls
– Aneurysm- ballooning of a blood vessel
 Most often in abdomen or brain
 Athersclerosis and hypertension can
weaken walls of vessels leading to an
aneurysm - Can rupture
Speno is fine. Joe told me FOD was already lined.
Flow through veins cont’d.
Varicose veins
From weakened valves
Develop due to backward pressure of blood
Inflammation of a vein
Can lead to blood clots
Cardiovascular disorders
– Plaque formation in vessels-fats and cholesterol
– Interferes with blood flow
– Can be inherited
– Prevention
 Diet high in fruits and vegetables
 Low in saturated fats and cholesterol
– Plaques can cause clots to form-thrombus
 If clot breaks lose from a plaque it becomes a
Cardiovascular disorders cont’d.
Stroke, heart attack, and aneurysm
– Stroke (CVA)- small cranial arteriole becomes blocked
by an embolism and a portion of the brain dies due to
lack of oxygen.
 Lack of oxygen to brain can cause paralysis or
death Warning signs- numbness in hands or face,
difficulty speaking, temporary blindness in one eye
– Heart attack (MI – Myocardial Infarction)-portion of the
heart muscle deprived of oxygen and dies
 Angina pectoris-chest pain from partially blocked
coronary artery Heart attack occurs when vessel
becomes completely blocked
– Aneurysm- ballooning of a blood vessel
 Most often in abdomen or brain
 Athersclerosis and hypertension can weaken walls
of vessels leading to an aneurysm Can rupture
Cardiovascular disorders cont’d.
Coronary bypass operations
– Bypass blocked areas of coronary arteries
– Can graft another vessel to the aorta and
then to the blocked artery past the point of
blockage of blocked coronary arteries.
– Gene therapy is sometimes used to grow
new vessels
Coronary bypass operation
Fig. 12.17
Cardiovascular disorders cont’d.
Clearing clogged arteries
– Angioplasty
 Catheter is placed in clogged artery
 Balloon attached to catheter is inflated
 Increases the lumen of the vessel
 Stents can be placed to keep vessel open
Dissolving blood clots
– Treatment for thromboembolism includes t-PA
– Converts plasminogen to plasmin
– Dissolves clot
Fig. 12.18
Heart transplants and artificial hearts
– Translpants usually successful but shortage of
– LVAD-left ventricular assist device
 Alternative to heart transplant
 Tube passes blood from left ventricle to the LVAD
 Blood is pumped to the aorta
– TAH-total artificial heart
 Generally only used in very ill patients
 Survival rates are not good but may be because
patients are so ill
– 20% of Americans have hypertension
– Atherosclerosis also can cause hypertension by
narrowing vessels
– Silent killer-may not be diagnosed until person has a
heart attack or stroke
– Causes damage to heart, brain, kidneys, and vessels
– 2 genes may be responsible
 One is a gene for angiotensinogen- powerful
 The other codes for an enzyme that activates
– Monitor blood pressure and adopt lifestyle that lowers
Principle of Gas Exchange in Animals
Rate of diffusion between two regions is
governed by Fick’s Law of Diffusion.
R = D x A ( p/d)
– R = rate of diffusion
– D = diffusion constant
– A = area over which diffusion takes place
– p = differences in concentrations
– d = distance across which diffusion takes
How Animals Maximize the Rate of Diffusion
beating cilia producing water current
respiratory organs that increase surface area
available for diffusion
– bring external environment close to
internal fluid
atmospheric pressure and partial pressures
– one atmosphere is 760 mm Hg
– partial pressure is fraction contributed by a
The Gill as a Respiratory Structure
External gills provide a greatly increased
surface area for gas exchange.
– disadvantages are that they must be
moved constantly and are easily damaged
Gills of bony fish
– located between buccal cavity and
opercular cavity
Bony Fish Respiration
The Gill as a Respiratory Structure
Buccal cavity can be opened and closed by
opening and closing the mouth.
Opercular cavity can be opened and closed
by movements of the operculum.
– ram ventilation
 blood flows in an opposite direction to
the flow of water, thus maximizing
oxygenation of blood
 gill arches
 countercurrent flow
Structure of a Fish Gill
Respiration in Air-Breathing Animals
Gills replaced in terrestrial animals because:
– air is less buoyant than water
– water vapor diffuses into the air through
Two main terrestrial respiratory organs:
– tracheae
– lung
 Lungs use a uniform pool of air in
constant contact with gas exchange
Respiration in Amphibians and Reptiles
Lungs of amphibians are formed as saclike
outpouching of the gut.
– Amphibians force air into their lungs
creating positive pressure.
 fill buccal cavity with air, and then close
mouth and nostrils and elevate floor of
oral cavity
– Reptiles expand their rib cages by
muscular contraction and take air into
lungs via negative pressure breathing.
Amphibian Lungs
Respiration in Mammals
Lungs of mammals packed with alveoli.
– Air brought to alveoli through system of air
 Inhaled air taken to the larynx, passes
through glottis into the trachea.
 Bifurcates into right and left bronchi
which enter each lung and further
subdivide into bronchioles that deliver
air into alveoli.
Human Respiratory System
Respiration in Birds
Bird lung channels air through tiny air
vessels called parabronchi, where gas
exchange occurs.
– unidirectional flow
When air sacs are expanded during
inspiration, they take in air.
When they are compressed during
expiration, they push air into and through the
Respiration in Birds
Avian respiration occurs in two cycles.
– Each cycle has an inspiration and an
expiration phase.
 Cross-current flow has the capacity to
extract more oxygen from the air than a
mammalian lung.
How A Bird Breathes
Structures and Mechanisms of Breathing
The outside of each lung is covered by a
visceral pleural membrane.
– Second parietal pleural membrane lines
inner wall of thoracic cavity.
 pleural cavity between the two
Structures and Mechanisms of Breathing
Mechanics of breathing
– Boyle’s Law - when the volume of a given
quantity of gas increases, its pressure
 When the pressure within the lungs is
lower than the atmospheric pressure, air
enters the lungs.
– Thoracic volume increased by contraction
of external intercostals and the diaphragm.
Gas Exchange
Structures and Mechanisms of Breathing
Breathing measurements
– tidal volume - volume of air moving into
and out of the lungs
– vital capacity - maximum amount of air
that can be expired after a forceful
– hypoventilating - slow breathing - too
much carbon dioxide
– hyperventilating - rapid breathing - not
enough carbon dioxide
Mechanisms That Regulate Breathing
Rise in carbon dioxide causes blood pH to
lower, stimulating neurons in the aortic and
carotid bodies to send impulses to the
control center in the medulla oblongata.
– Sends impulses to diaphragm and
external intercostal muscles, stimulating
them to contract, expanding chest cavity.
Hemoglobin and Oxygen Transport
Hemoglobin is a protein composed of four
polypeptide chains and four organic heme
– iron atom at center of each heme group
Hemoglobin loads up with oxygen in the
lungs, forming oxyhemoglobin.
– As blood passes through the capillaries,
some of the oxyhemoglobin releases
oxygen and become deoxyhemoglobin.
Hemoglobin and Oxygen Transport
Oxygen transport
– Oxygen transport in the blood is affected
by many conditions.
 pH - Bohr effect
Carbon Dioxide and Nitric Oxide Transport
About 8% of CO2 in blood is dissolved in
plasma and another 20% is bound to
– Remaining 72% of CO2 diffuses into red
blood cells where carbonic anhydrase
catalyzes the combination of CO2 with
water to form carbonic acid.
Blood flow and blood pressure are also
regulated by the amount of NO released into
the bloodstream.
Carbon Dioxide Transport by the Blood
Open and Closed
Circulatory Systems
Characteristics of
Blood Vessels
The Lymphatic System
The Fish Heart
Amphibian and Reptile
Mammalian and Bird
Cardiac Cycle
How Animals Maximize
Rate of Diffusion
– Gills
– Air-Breathing
– Amphibians and
– Mammals
– Birds
Structures and
Mechanisms of

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