Biology 172

1
Biology 172

• Circulation and Gas Exchange

2

• Multicellular organisms Direct exchanges are
  usually not possible except for some os the
  simplest.
• Gills, lungs and skin are an example of a
  specialized exchange surfaces in animals
• Internal transport systems are usually associated
  with external gas exchange in most animals

3
Fig. 42-1
4
Gastrovascular Cavities

• Simple animals, such as cnidarians, have a body
  wall that is only two cells thick and that
  encloses a gastrovascular cavity.
• Flatworms are a triploblastic group with a
  gastrovascular cavity.
• Gas exchange and the elimination of nitrogenous
  waste occurs between individual cells and the
  environment.

5
Fig. 42-2a
Circular canal
Mouth
Radial canal
5 cm
(a) The moon jelly Aurelia, a cnidarian
6
Figure 42.1x Aurelia (moon jelly)
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Fig. 42-2b
Mouth
Pharynx
2 mm
The planarian Dugesia, a flatworm
(b)
8
Types of Circulatory System

• In insects, other arthropods, and most molluscs,
  blood bathes the organs directly in an open
  circulatory system
• Hemolymph
• Hemocoel
• Most more active animals have a closed
  circulatory system
• More efficient
• Blood and Lymph

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Figure 42.3 Open and closed circulatory systems
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Evolution of the Vertebrate heart

• Two, three and four chambers
• Show greater efficiency and animals move to land.
• Related to the ability of the animal to maintain
  a constant body temperature.

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Fig. 42-4
Gill capillaries
Gill circulation
Artery
Ventricle
Heart
Atrium
Systemic circulation
Vein
Systemic capillaries
12
Fig. 42-5
Amphibians
Reptiles (Except Birds)
Mammals and Birds
Lung and skin capillaries
Lung capillaries
Lung capillaries
Right systemic aorta
Pulmocutaneous circuit
Pulmonary circuit
Pulmonary circuit
Atrium (A)
Atrium (A)
A
A
A
A
V
V
Ventricle (V)
V
V
Left systemic aorta
Left
Right
Left
Right
Right
Left
Systemic circuit
Systemic circuit
Systemic capillaries
Systemic capillaries
Systemic capillaries
13
Double Circulation

• In reptiles and mammals, oxygen-poor blood flows
  through the pulmonary circuit to pick up oxygen
  through the lungs
• In amphibians, oxygen-poor blood flows through a
  pulmocutaneous circuit to pick up oxygen through
  the lungs and skin
• Oxygen-rich blood delivers oxygen through the
  systemic circuit
• Double circulation maintains higher blood
  pressure in the organs than does single
  circulation

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Figure 42.6 The mammalian cardiovascular system
an overview
15
Figure 42.7 The mammalian heart a closer look
16

• 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

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Figure 42.6 The cardiac cycle
18
Cardiac Output

• The heart rate - number of beats per minute
• The stroke volume is the amount of blood pumped
  per contraction
• The cardiac output is the volume of blood pumped
  into the systemic circulation per minute and
  depends on both the heart rate and stroke volume

19
Heart Valves

• Four valves prevent backflow of blood in the
  heart
• The atrioventricular (AV) valves separate each
  atrium and ventricle
• The semilunar valves control blood flow to the
  aorta and the pulmonary artery

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Heart Valve Action

• The lub-dup sound of a heart beat is caused by
  the recoil of blood against the AV valves (lub)
  then against the semilunar (dup) valves
• Backflow of blood through a defective valve
  causes a heart murmur

21
Maintaining the Hearts Rhythmic Beat

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

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• 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

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

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Fig. 42-9-5
1
2
3
Signals spread throughout ventricles.
Pacemaker generates wave of signals to contract.
Signals are delayed at AV node.
Signals pass to heart apex.
4
SA node (pacemaker)
AV node
Purkinje fibers
Bundle branches
Heart apex
ECG
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Fig. 42-10
Artery
Vein
SEM
Valve
100 µm
Basal lamina
Endothelium
Endothelium
Smooth muscle
Smooth muscle
Connective tissue
Connective tissue
Capillary
Artery
Vein
Arteriole
Venule
15 µm
Red blood cell
Capillary
LM
26
Figure 42.9 Blood flow in veins
27
Figure 42.10 The interrelationship of blood flow
velocity, cross-sectional area of blood vessels,
and blood pressure
28
Blood Pressure

• Blood pressure is the hydrostatic pressure that
  blood exerts against the wall of a vessel
• In rigid vessels blood pressure is maintained
  less rigid vessels deform and blood pressure is
  lost

29
Changes in Blood Pressure During the Cardiac Cycle

• Systolic pressure is the pressure in the arteries
  during ventricular systole - highest pressure in
  the arteries
• Diastolic pressure is the pressure in the
  arteries during diastole - lower than systolic
  pressure
• A pulse is the rhythmic bulging of artery walls
  with each heartbeat

30
Regulation of Blood Pressure

• Blood pressure is determined by cardiac output
  and peripheral resistance due to constriction of
  arterioles
• Vasoconstriction is the contraction of smooth
  muscle in arteriole walls -increases blood
  pressure
• Vasodilation is the relaxation of smooth muscles
  in the arterioles decreases blood pressure

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Fig. 42-13-3
Blood pressure reading 120/70
Pressure in cuff greater than 120 mm Hg
Pressure in cuff drops below 120 mm Hg
Pressure in cuff below 70 mm Hg
Rubber cuff inflated with air
120
120
70
Artery closed
Sounds audible in stethoscope
Sounds stop
32
Capillary Function

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

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Fig. 42-15
Thoroughfare channel
Precapillary sphincters
Capillaries
Arteriole
Venule
(a) Sphincters relaxed
Arteriole
Venule
(b) Sphincters contracted
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Capillary Exchanges

• 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

35
Fig. 42-16
Body tissue
INTERSTITIAL FLUID
Capillary
Net fluid movement out
Net fluid movement in
Direction of blood flow
Blood pressure
Inward flow
Pressure
Outward flow
Osmotic pressure
Arterial end of capillary
Venous end
36
Fluid Return by the Lymphatic System

• The lymphatic system returns fluid that leaks out
  in the capillary beds
• This system aids in body defense
• Fluid, called lymph, reenters the circulation
  directly at the venous end of the capillary bed
  and indirectly through the lymphatic system
• The lymphatic system drains into veins in the neck

37
Lymph Nodes

• Lymph nodes are organs that filter lymph and play
  an important role in the bodys defense
• Edema is swelling caused by disruptions in the
  flow of lymph

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Fig. 42-17
Plasma 55
Constituent
Major functions
Cellular elements 45
Cell type
Functions
Number per µL (mm3) of blood
Solvent for carrying other substances
Water
Erythrocytes (red blood cells)
Transport oxygen and help transport carbon dioxide
56 million
Ions (blood electrolytes)
Osmotic balance, pH buffering, and regulation
of membrane permeability
Sodium Potassium Calcium Magnesium Chloride Bicarb
onate
Separated blood elements
Leukocytes (white blood cells)
5,00010,000
Defense and immunity
Plasma proteins
Albumin
Osmotic balance pH buffering
Lymphocyte
Basophil
Fibrinogen
Clotting
Eosinophil
Defense
Immunoglobulins (antibodies)
Neutrophil
Monocyte
Substances transported by blood
Nutrients (such as glucose, fatty acids,
vitamins) Waste products of metabolism Respiratory
gases (O2 and CO2) Hormones
Platelets
Blood clotting
250,000 400,000
39
Plasma

• Blood plasma is about 90 water
• Dissolved ions, sometimes called electrolytes
• Plasma proteins, which influence blood pH,
  osmotic pressure, and viscosity
• Various plasma proteins function in lipid
  transport, immunity, and blood clotting

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Cellular Elements

• Suspended in blood plasma are two types of cells
• Red blood cells (erythrocytes) transport oxygen
  - Hemoglobin
• White blood cells (leukocytes) function in
  defense - Five major types
• Platelets, a third cellular element, are
  fragments of cells that are involved in clotting

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Figure 42.14x Blood smear
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Fig. 42-19
Multipotent Stem cells (in bone marrow)
Myeloid stem cells
Lymphoid stem cells
Lymphocytes
B cells
T cells
Erythrocytes
Neutrophils
Platelets
Eosinophils
Basophils
Monocytes
43
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
• A blood clot formed within a blood vessel is
  called a thrombus and can block blood flow

44
Fig. 42-18-4
Red blood cell
Collagen fibers
Platelet plug
Fibrin clot
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
45
Figure 42.16x Blood clot
46
Cardiovascular Disease

• Cardiovascular diseases are disorders of the
  heart and the blood vessels
• They account for more than half the deaths in the
  United States
• One type of cardiovascular disease,
  atherosclerosis, is caused by the buildup of
  plaque deposits within arteries

47
Fig. 42-20
Atherosclerosis normal artery and artery with
plaque
Smooth muscle
Connective tissue
Plaque
Endothelium
(a) Normal artery
(b) Partly clogged artery
50 µm
250 µm
48
Heart Attacks 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

49
Treatment and Diagnosis of Cardiovascular Disease

• Cholesterol is a major contributor to
  atherosclerosis
• Low-density lipoproteins (LDLs) are associated
  with plaque formation these are bad
  cholesterol
• High-density lipoproteins (HDLs) reduce the
  deposition of cholesterol these are good
  cholesterol
• The proportion of LDL relative to HDL can be
  decreased by exercise, not smoking, and avoiding
  foods with trans fats

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• Hypertension, or high blood pressure, promotes
  atherosclerosis and increases the risk of heart
  attack and stroke
• Hypertension can be reduced by dietary changes,
  exercise, and/or medication

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The role of gas exchange in bioenergetics
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Fig. 42-21
Coelom
Gills
Gills
Tube foot
Parapodium (functions as gill)
(a) Marine worm
(c) Sea star
(b) Crayfish
53
Fig. 42-21a
Parapodium (functions as gill)
(a) Marine worm
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Fig. 42-21b
Gills
(b) Crayfish
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Fig. 42-21c
Coelom
Gills
Tube foot
(c) Sea star
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Ventilation

• Ventilation moves the respiratory medium over the
  respiratory surface
• Aquatic animals move through water or move water
  over their gills for ventilation
• Fish gills use a countercurrent exchange system,
  where blood flows in the opposite direction to
  water passing over the gills blood is always
  less saturated with O2 than the water it meets

57
Fig. 42-22
Fluid flow through gill filament
Oxygen-poor blood
Anatomy of gills
Oxygen-rich blood
Gill arch
Lamella
Gill arch
Gill filament organization
Blood vessels
Water flow
Operculum
Water flow between lamellae
Blood flow through capillaries in lamella
Countercurrent exchange
PO2 (mm Hg) in water
150
120
90
60
30
Gill filaments
Net diffu- sion of O2 from water to blood
110
80
20
50
140
PO2 (mm Hg) in blood
58
Figure 42.21 Countercurrent exchange
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Tracheal Systems in Insects

• The tracheal system of insects consists of tiny
  branching tubes that penetrate the body
• The tracheal tubes supply O2 directly to body
  cells
• The respiratory and circulatory systems are
  separate

60
Fig. 42-23
Air sacs
Tracheae
External opening
Tracheoles
Mitochondria
Muscle fiber
Body cell
Air sac
Tracheole
Trachea
Body wall
Air
2.5 µm
61
Lungs

• Lungs are an infolding of the body surface
• The circulatory system (open or closed)
  transports gases between the lungs and the rest
  of the body
• The size and complexity of lungs correlate with
  an animals metabolic rate

62
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 via the larynx, trachea, bronchi,
  bronchioles, and alveoli, where gas exchange
  occurs
• Exhaled air passes over the vocal cords to create
  sounds
• Secretions called surfactants coat the surface of
  the alveoli

63
Fig. 42-24
Branch of pulmonary vein (oxygen-rich blood)
Branch of pulmonary artery (oxygen-poor blood)
Terminal bronchiole
Nasal cavity
Pharynx
Larynx
Alveoli
(Esophagus)
Left lung
Trachea
Right lung
Bronchus
Bronchiole
Diaphragm
Heart
SEM
Colorized SEM
50 µm
50 µm
64
Figure 42.23c Alveoli
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Figure 42.23cx1 Alveolar structure of mouse lung
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Concept 42.6 Breathing Ventilates the Lungs

• The process that ventilates the lungs is
  breathing, the alternate inhalation and
  exhalation of air
• An amphibian such as a frog ventilates its lungs
  by positive pressure breathing, which forces air
  down the trachea
• Mammals ventilate their lungs by negative
  pressure breathing, which pulls air into the lungs

67
Fig. 42-25
Rib cage expands as rib muscles contract
Rib cage gets smaller as rib muscles relax
Air inhaled
Air exhaled
Lung
Diaphragm
EXHALATION Diaphragm relaxes (moves up)
INHALATION Diaphragm contracts (moves down)
68
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

69
Fig. 42-26
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
70
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
• The pons regulates the tempo

71

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

72
Fig. 42-27
Cerebrospinal fluid
Pons
Breathing control centers
Medulla oblongata
Carotid arteries
Aorta
Diaphragm
Rib muscles
73
Coordination of Circulation and Gas Exchange

• Blood arriving in the lungs has a low partial
  pressure of O2 and a high partial pressure of CO2
  relative to air in the alveoli
• In the alveoli, O2 diffuses into the blood and
  CO2 diffuses into the air
• In tissue capillaries, partial pressure gradients
  favor diffusion of O2 into the interstitial
  fluids and CO2 into the blood

74
Fig. 42-28
Alveolus
Alveolus
PO2 100 mm Hg
PCO2 40 mm Hg
PO2 40
PO2 100
PCO2 40
PCO2 46
Circulatory system
Circulatory system
PO2 40
PO2 100
PCO2 46
PCO2 40
PO2 40 mm Hg
PCO2 46 mm Hg
Body tissue
Body tissue
(b) Carbon dioxide
(a) Oxygen
75
Respiratory Pigments

• Respiratory pigments, proteins that transport
  oxygen, greatly increase the amount of oxygen
  that blood can carry
• Arthropods and many molluscs have hemocyanin with
  copper as the oxygen-binding component
• Most vertebrates and some invertebrates use
  hemoglobin contained within erythrocytes

76
Hemoglobin

• A single hemoglobin molecule can carry four
  molecules of O2
• The hemoglobin dissociation curve shows that a
  small change in the partial pressure of oxygen
  can result in a large change in delivery of O2
• CO2 produced during cellular respiration lowers
  blood pH and decreases the affinity of hemoglobin
  for O2 this is called the Bohr shift

77
Fig. 42-UN1
? Chains
Iron
Heme
? Chains
Hemoglobin
78
Carbon Dioxide Transport

• Hemoglobin also helps transport CO2 and assists
  in buffering
• CO2 from respiring cells diffuses into the blood
  and is transported either in blood plasma, bound
  to hemoglobin, or as bicarbonate ions (HCO3)

79
Fig. 42-30a
Body tissue
CO2 transport from tissues
CO2 produced
Interstitial fluid
CO2
Capillary wall
CO2
Plasma within capillary
CO2
H2O
Hemoglobin picks up CO2 and H
Red blood cell
H2CO3
Hb
Carbonic acid
H
HCO3 Bicarbonate

HCO3
To lungs
80
Fig. 42-30b
CO2 transport to lungs
HCO3
HCO3
H

Hemoglobin releases CO2 and H
Hb
H2CO3
H2O
CO2
Plasma within lung capillary
CO2
CO2
CO2
Alveolar space in lung
81
Elite Animal Athletes

• Migratory and diving mammals have evolutionary
  adaptations that allow them to perform
  extraordinary feats
• The extreme O2 consumption of the antelope-like
  pronghorn underlies its ability to run at high
  speed over long distances

82
Fig. 42-31
RESULTS
Goat
Pronghorn
100
90
80
70
60
Relative values ()
50
40
30
20
10
0
VO2 max
Lung capacity
Cardiac output
Muscle mass
Mitochon- drial volume
83
Diving Mammals

• Deep-diving air breathers stockpile O2 and
  deplete it slowly
• Weddell seals have a high blood to body volume
  ratio and can store oxygen in their muscles in
  myoglobin proteins

84
Fig. 42-UN2
Inhaled air
Exhaled air
Alveolar spaces
Alveolar epithelial cells
CO2
O2
CO2
O2
Alveolar capillaries of lung
Pulmonary veins
Pulmonary arteries
Systemic veins
Systemic arteries
Heart
Systemic capillaries
O2
CO2
CO2
O2
Body tissue