Circulation and Gas Exchange

1

• Circulation and Gas Exchange

2
Open and Closed Circulatory Systems

• Both systems have three basic components
• A circulatory fluid (blood or hemolymph)
• A set of tubes (blood vessels)
• A muscular pump (the heart)
• open circulatory system
• In insects, other arthropods, and most molluscs
• blood bathes the organs directly
• no distinction between blood and interstitial
  fluid (hemolymph)

3
LE 42-3
Heart
Heart
Hemolymph in sinuses surrounding organs
Small branch vessels in each organ
Interstitial fluid
Anterior vessel
Lateral vessel
Ostia
Dorsal vessel (main heart)
Tubular heart
Auxiliary hearts
Ventral vessels
An open circulatory system.
A closed circulatory system.
4

• closed circulatory system
• blood is confined to vessels and is distinct from
  the interstitial fluid

5

• Arteries carry blood to capillaries
• where chemical exchange between the blood and
  interstitial fluid
• Veins return blood from capillaries to the heart

6
Fishes

• 2 chambered heart
• one ventricle and one atrium
• Gills for gas exchange

7
Amphibians

• 3 chambered heart
• two atria and one ventricle

8
Reptiles (Except Birds)

• double circulation
• pulmonary circuit (lungs)
• systemic circuit
• 3 chambered heart

9
Mammals and Birds

• 4 chambered heart
• 2 atria and 2 ventricle
• left side receives oxygen-rich blood
• right side receives oxygen-poor blood

10

• A powerful four-chambered heart was an essential
  adaptation of the endothermic way of life
  characteristic of mammals and birds

11
LE 42-4
FISHES
AMPHIBIANS
REPTILES (EXCEPT BIRDS)
MAMMALS AND BIRDS
Gill capillaries
Lung and skin capillaries
Lung capillaries
Lung capillaries
Pulmocutaneous circuit
Pulmonary circuit
Gill circulation
Pulmonary circuit
Right systemic aorta
Artery
Heart Ventricle (V)
Left systemic aorta
A
A
A
A
A
A
Atrium (A)
V
V
V
V
V
Right
Left
Left
Right
Right
Left
Systemic circulation
Systemic circuit
Systemic circuit
Vein
Systemic capillaries
Systemic capillaries
Systemic capillaries
Systemic capillaries
Systemic circuits include all body tissues except
lungs. Note that circulatory systems are depicted
as if the animal is facing you with the right
side of the heart shown at the left and
vice-versa.
12
LE 42-5
Capillaries of head and forelimbs
Anterior vena cava
Pulmonary artery
Pulmonary artery
Aorta
Capillaries of right lung
Capillaries of left lung
Pulmonary vein
Pulmonary vein
Right atrium
Left atrium
Left ventricle
Right ventricle
Posterior vena cava
Aorta
Capillaries of abdominal organs and hind limbs
13
LE 42-6
Pulmonary artery
Aorta
Anterior vena cava
Pulmonary artery
Right atrium
Left atrium
Pulmonary veins
Pulmonary veins
Semilunar valve
Semilunar valve
Atrioventricular valve
Atrioventricular valve
Posterior vena cava
Right ventricle
Left ventricle
14

• The heart contracts and relaxes in a rhythmic
  cycle called the cardiac cycle
• The contraction, or pumping, phase is called
  systole
• The relaxation, or filling, phase is called
  diastole

15
LE 42-7
Atrial systole ventricular diastole
Semilunar valves closed
0.1 sec
Semilunar valves open
AV valves open
0.3 sec
0.4 sec
Atrial and ventricular diastole
AV valves closed
Ventricular systole atrial diastole
16

• The heart rate, also called the pulse, is the
  number of beats per minute
• The cardiac output is the volume of blood pumped
  into the systemic circulation per minute

17
Maintaining the Hearts Rhythmic Beat

• Some cardiac muscle cells are self-excitable,
  meaning they contract without any signal from the
  nervous system

18

• The sinoatrial (SA) node, or pacemaker, sets the
  rate and timing at which cardiac muscle cells
  contract
• 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

19

• Impulses that travel during the cardiac cycle can
  be recorded as an electrocardiogram (ECG or EKG)

20
LE 42-8
Pacemaker generates wave of signals to contract.
Signals are delayed at AV node.
Signals pass to heart apex.
Signals spread throughout ventricles.
SA node (pacemaker)
AV node
Bundle branches
Purkinje fibers
Heart apex
ECG
21

• The pacemaker is influenced by nerves, hormones,
  body temperature, and exercise

22
Concept 42.3 Physical principles govern blood
circulation

• The physical principles that govern movement of
  water in plumbing systems also influence the
  functioning of animal circulatory systems

23
Blood Vessel Structure and Function

• The infrastructure of the circulatory system is
  its network of blood vessels
• All blood vessels are built of similar tissues
  and have three similar layers

24
LE 42-9
Artery
Vein
100 µm
Endothelium
Valve
Basement membrane
Endothelium
Endothelium
Smooth muscle
Smooth muscle
Capillary
Connective tissue
Connective tissue
Vein
Artery
Venule
Arteriole
25

• Structural differences in arteries, veins, and
  capillaries correlate with functions
• Arteries have thicker walls that accommodate the
  high pressure of blood pumped from the heart

26

• In the thinner-walled veins, blood flows back to
  the heart mainly as a result of muscle action

27
LE 42-10
Direction of blood flow in vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)
28
Blood Flow Velocity

• Physical laws governing movement of fluids
  through pipes affect blood flow and blood
  pressure
• Velocity of blood flow is slowest in the
  capillary beds, as a result of the high
  resistance and large total cross-sectional area

29
LE 42-11
5,000
4,000
3,000
Area (cm2)
2,000
1,000
0
50
40
Velocity (cm/sec)
30
20
10
0
120
Systolic pressure
100
80
Pressure (mm Hg)
60
Diastolic pressure
40
20
0
Venae cavae
Veins
Venules
Capillaries
Arterioles
Aorta
Arteries
30
Blood Pressure

• Blood pressure is the hydrostatic pressure that
  blood exerts against the wall of a vessel
• Systolic pressure is the pressure in the arteries
  during ventricular systole it is the highest
  pressure in the arteries
• Diastolic pressure is the pressure in the
  arteries during diastole it is lower than
  systolic pressure
• Blood pressure is determined by cardiac output
  and peripheral resistance due to constriction of
  arterioles

31
LE 42-12_4
Blood pressure reading 120/70
Pressure in cuff below 120
Pressure in cuff above 120
Pressure in cuff below 70
Rubber cuff inflated with air
120
120
70
Sounds audible in stethoscope
Sounds stop
Artery
Artery closed
32
Capillary Function

• Capillaries in major organs are usually filled to
  capacity
• Blood supply varies in many other sites

33

• Two mechanisms regulate distribution of blood in
  capillary beds
• Contraction of the smooth muscle layer in the
  wall of an arteriole constricts the vessel
• Precapillary sphincters control flow of blood
  between arterioles and venules

34
LE 42-13ab
Thoroughfare channel
Precapillary sphincters
Venule
Arteriole
Capillaries
Sphincters relaxed
Venule
Arteriole
Sphincters contracted
35
LE 42-13c
Capillaries and larger vessels (SEM)
20 µm
36

• The critical exchange of substances between the
  blood and interstitial fluid takes place across
  the thin endothelial walls of the capillaries
• The difference between blood pressure and osmotic
  pressure drives fluids out of capillaries at the
  arteriole end and into capillaries at the venule
  end

37
LE 42-14
Tissue cell
INTERSTITIAL FLUID
Net fluid movement out
Net fluid movement in
Capillary
Capillary
Red blood cell
15 µm
Direction of blood flow
Blood pressure
Osmotic pressure
Inward flow
Pressure
Outward flow
Arterial end of capillary
Venous end
38
Fluid Return by the Lymphatic System

• The lymphatic system returns fluid to the body
  from the capillary beds
• This system aids in body defense
• Fluid reenters the circulation directly at the
  venous end of the capillary bed and indirectly
  through the lymphatic system

39
Concept 42.4 Blood is a connective tissue with
cells suspended in plasma

• In invertebrates with open circulation, blood
  (hemolymph) is not different from interstitial
  fluid
• Blood in the circulatory systems of vertebrates
  is a specialized connective tissue

40
Blood Composition and Function

• Plasma
• Fluid
• 55 of blood composition
• Cellular Components
• 45 of blood composition

41
Plasma

• Blood plasma is about 90 water
• Solutes
• inorganic salts
• dissolved ions
• sometimes called electrolytes
• plasma proteins
• influence blood pH, osmotic pressure, and
  viscosity
• lipid transport
• Immunity
• blood clotting
• Ex. albumins, globulins, fibrinogen

42
LE 42-15
Plasma 55
Constituent
Cellular elements 45
Major functions
Cell type
Number
Functions
Water
Solvent for carrying other substances
per µL (mm3) of blood
Erythrocytes (red blood cells)
Ions (blood electrolytes)
56 million
Transport oxygen and help transport carbon dioxide
Sodium Potassium Calcium Magnesium Chloride Bicarb
onate
Osmotic balance, pH buffering, and regulation
of membrane permeability
Separated blood elements
Leukocytes (white blood cells)
Defense and immunity
5,00010,000
Plasma proteins
Albumin
Osmotic balance, pH buffering
Lymphocyte
Basophil
Fibrinogen
Clotting
Immunoglobulins (antibodies)
Defense
Eosinophil
Substances transported by blood
Monocyte
Neutrophil
Nutrients (such as glucose, fatty acids,
vitamins) Waste products of metabolism Respiratory
gases (O2 and CO2) Hormones
Platelets
250,000 400,000
Blood clotting
43
Cellular Elements

• Suspended in blood plasma are two types of cells
• Red blood cells (erythrocytes) transport oxygen
• Most abundant
• White blood cells (leukocytes) function in
  defense
• Include monocytes, neutrophils, basophils,
  eosinophils, and lymphocytes
• defense
• phagocytizing bacteria and debris
• producing antibodies
• Platelets involved in clotting

44

• Erythrocytes, leukocytes, and platelets all
  develop from a common source, pluripotent stem
  cells in the red marrow of bones

45
LE 42-16
Pluripotent stem cells (in bone marrow)
Myeloid stem cells
Lymphoid stem cells
Basophils
B cells
T cells
Lymphocytes
Eosinophils
Neutrophils
Erythrocytes
Monocytes
Platelets
46
Blood Clotting

• When the endothelium of a blood vessel is
  damaged, the clotting mechanism begins
• A cascade of complex reactions converts
  fibrinogen to fibrin, forming a clot

47
LE 42-17
Endothelium of vessel is damaged, exposing
connective tissue platelets adhere
Platelets form a plug
Seal is reinforced by a clot of fibrin
Collagen fibers
Fibrin clot
Red blood cell
Platelet plug
Platelet releases chemicals that make nearby
platelets sticky
Clotting factors from
Platelets Damaged cells Plasma (factors include
calcium, vitamin K)
Prothrombin
Thrombin
Fibrinogen
Fibrin
5 µm
48

• One type of cardiovascular disease,
  atherosclerosis, is caused by the buildup of
  cholesterol within arteries

49
LE 42-18
Connective tissue
Smooth muscle
Endothelium
Plaque
50 µm
Normal artery
Partly clogged artery
250 µm
50

• Hypertension, or high blood pressure, promotes
  atherosclerosis and increases the risk of heart
  attack and stroke
• A heart attack is the death of cardiac muscle
  tissue resulting from blockage of one or more
  coronary arteries
• A stroke is the death of nervous tissue in the
  brain, usually resulting from rupture or blockage
  of arteries in the head

51
Concept 42.5 Gas exchange occurs across
specialized respiratory surfaces

• Gas exchange supplies oxygen for cellular
  respiration and disposes of carbon dioxide
• Animals require large, moist respiratory surfaces
  for adequate diffusion of gases between their
  cells and the respiratory medium, either air or
  water

52
LE 42-19
Respiratory medium (air or water)
Respiratory surface
CO2
O2
Organismal level
Circulatory system
Cellular level
Energy-rich fuel molecules from food
ATP
Cellular respiration
53
Gills in Aquatic Animals

• Gills are outfoldings of the body surface
  specialized for gas exchange

54

• In some invertebrates, gills have a simple shape
  and are distributed over much of the body

55
LE 42-20a
Gills
Coelom
Tube foot
Sea star
56

• Many segmented worms have flaplike gills that
  extend from each segment of their body

57
LE 42-20b
Parapodia
Gill
Marine worm
58

• The gills of clams, crayfish, and many other
  animals are restricted to a local body region

59
LE 42-20c
Gills
Scallop
60
LE 42-20d
Gills
Crayfish
61

• Effectiveness of gas exchange in some gills,
  including those of fishes, is increased by
  ventilation and the countercurrent flow of blood
  and water

62
LE 42-21
Oxygen-poor blood
Lamella
Oxygen-rich blood
Gill arch
Blood vessel
Gill arch
15
40
70
Water flow
5
30
Operculum
60
100
90
Water flow over lamellae showing O2
O2
Blood flow through capillaries in
lamellae showing O2
Gill filaments
Countercurrent exchange
63
Tracheal Systems in Insects

• The tracheal system of insects consists of tiny
  branching tubes that penetrate the body

64
LE 42-22a
Tracheae
Air sacs
Spiracle
65
LE 42-22b
Body cell
Air sac
Tracheole
Trachea
Air
Body wall
Myofibrils
Tracheoles
Mitochondria
2.5 µm
66

• The tracheal tubes supply O2 directly to body
  cells

67
Lungs

• Spiders, land snails, and most terrestrial
  vertebrates have internal lungs

68
Mammalian Respiratory Systems A Closer Look

• A system of branching ducts conveys air to the
  lungs
• Air inhaled through the nostrils passes through
  the pharynx into the trachea, bronchi,
  bronchioles, and dead-end alveoli, where gas
  exchange occurs

69
LE 42-23
Branch from pulmonary artery (oxygen-poor blood)
Branch from pulmonary vein (oxygen-rich blood)
Terminal bronchiole
Nasal cavity
Pharynx
Alveoli
Larynx
Left lung
Esophagus
50 µm
Trachea
Right lung
50 µm
Bronchus
Bronchiole
Diaphragm
Heart
Colorized SEM
SEM
70
How an Amphibian Breathes

• An amphibian such as a frog ventilates its lungs
  by positive pressure breathing, which forces air
  down the trachea

71
How a Mammal Breathes

• Mammals ventilate their lungs by negative
  pressure breathing, which pulls air into the
  lungs
• Lung volume increases as the rib muscles and
  diaphragm contract

72
LE 42-24
Rib cage gets smaller as rib muscles relax
Rib cage expands as rib muscles contract
Air inhaled
Air exhaled
Lung
Diaphragm
INHALATION Diaphragm contracts (moves down)
EXHALATION Diaphragm relaxes (moves up)
73
How a Bird Breathes

• Birds have eight or nine air sacs that function
  as bellows that keep air flowing through the
  lungs
• Air passes through the lungs in one direction
  only
• Every exhalation completely renews the air in the
  lungs

74
LE 42-25
Air
Air
Anterior air sacs
Trachea
Posterior air sacs
Lungs
Lungs
Air tubes (parabronchi) in lung
1 mm
EXHALATION Air sacs empty lungs fill
INHALATION Air sacs fill
75
Control of Breathing in Humans

• In humans, the main breathing control centers are
  in two regions of the brain, the medulla
  oblongata and the pons
• The medulla regulates the rate and depth of
  breathing in response to pH changes in the
  cerebrospinal fluid
• The medulla adjusts breathing rate and depth to
  match metabolic demands

76

• Sensors in the aorta and carotid arteries monitor
  O2 and CO2 concentrations in the blood
• These sensors exert secondary control over
  breathing

77
LE 42-26
Cerebrospinal fluid
Pons
Breathing control centers
Medulla oblongata
Carotid arteries
Aorta
Diaphragm
Rib muscles
78
Concept 42.7 Respiratory pigments bind and
transport gases

• The metabolic demands of many organisms require
  that the blood transport large quantities of O2
  and CO2

79
The Role of Partial Pressure Gradients

• Gases diffuse down pressure gradients in the
  lungs and other organs
• Diffusion of a gas depends on differences in a
  quantity called partial pressure

80

• A gas diffuses from a region of higher partial
  pressure to a region of lower partial pressure
• In the lungs and tissues, O2 and CO2 diffuse from
  where their partial pressures are higher to where
  they are lower

81
LE 42-27
Inhaled air
Exhaled air
120
27
160
0.2
Alveolar spaces
CO2
CO2
O2
O2
104
40
Alveolar epithelial cells
CO2
O2
CO2
O2
Blood leaving alveolar capillaries
Blood entering alveolar capillaries
CO2
O2
Alveolar capillaries of lung
40
45
104
40
CO2
O2
CO2
O2
Pulmonary veins
Pulmonary arteries
Systemic veins
Systemic arteries
Heart
Tissue capillaries
O2
CO2
Blood entering tissue capillaries
Blood leaving tissue capillaries
O2
CO2
40
45
100
40
O2
CO2
CO2
O2
Tissue cells
lt 40
gt 45
CO2
O2
82
Respiratory Pigments

• Respiratory pigments, proteins that transport
  oxygen, greatly increase the amount of oxygen
  that blood can carry

83
Oxygen Transport

• The respiratory pigment of almost all vertebrates
  is the protein hemoglobin, contained in
  erythrocytes
• Like all respiratory pigments, hemoglobin must
  reversibly bind O2, loading O2 in the lungs and
  unloading it in other parts of the body

84
LE 42-28
Iron atom
Heme group
O2 loaded in lungs
O2 unloaded in tissues
Polypeptide chain
85

• Loading and unloading of O2 depend on cooperation
  between the subunits of the hemoglobin molecule
• The binding of O2 to one subunit induces the
  other subunits to bind O2 with more affinity
• Cooperative O2 binding and release is evident in
  the dissociation curve for hemoglobin
• A drop in pH lowers affinity of hemoglobin for O2

86
LE 42-29a
100
O2 unloaded from hemoglobin during
normal metabolism
80
60
O2 saturation of hemoglobin ()
O2 reserve that can be unloaded from hemoglobin
to tissues with high metabolism
40
20
0
100
80
60
40
20
0
Tissues during exercise
Tissues at rest
Lungs
P (mm Hg)
O2
P and hemoglobin dissociation at 37C and pH
7.4
O2
87
LE 42-29b
100
pH 7.4
80
Bohr shift additional O2 released
from hemoglobin at lower pH (higher
CO2 concentration)
O2 saturation of hemoglobin ()
60
pH 7.2
40
20
0
100
80
60
40
20
0
P (mm Hg)
O2
pH and hemoglobin dissociation
88
Carbon Dioxide Transport

• Hemoglobin also helps transport CO2 and assists
  in buffering
• Carbon from respiring cells diffuses into the
  blood plasma and then into erythrocytes and is
  ultimately released in the lungs

89
LE 42-30
Tissue cell
CO2 transport from tissues
CO2 produced
Interstitial fluid
CO2
CO2
Capillary wall
Blood plasma within capillary
CO2
H2O
Hemoglobin picks up CO2 and H
Red blood cell
H2CO3 Carbonic acid
Hb
HCO3 Bicarbonate
H

HCO3
To lungs
CO2 transport to lungs
HCO3
H

HCO3
Hemoglobin releases CO2 and H
Hb
H2CO3
H2O
CO2
CO2
CO2
CO2
Alveolar space in lung
90
Animation O2 From Blood to Tissues
Animation O2 From Tissues to Blood
Animation O2 From Blood to Lungs
Animation O2 From Lungs to Blood
91
Elite Animal Athletes

• Migratory and diving mammals have evolutionary
  adaptations that allow them to perform
  extraordinary feats

92
The Ultimate Endurance Runner

• The extreme O2 consumption of the antelope-like
  pronghorn underlies its ability to run at high
  speed over long distances

93
(No Transcript)
94
Diving Mammals

• Deep-diving air breathers stockpile O2 and
  deplete it slowly