Circulation and Gas Exchange

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Circulation and Gas Exchange

• Chapter 42

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Trading with the Environment

• Every organism must exchange materials with its
  environment
• And this exchange ultimately occurs at the
  cellular level
• In unicellular organisms
• These exchanges occur directly with the
  environment
• For most of the cells making up multicellular
  organisms
• Direct exchange with the environment is not
  possible

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• The feathery gills projecting from a salmon
• Are an example of a specialized exchange system
  found in animals

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Circulatory System

• Internal transport system
• Distributes nutrients
• Removes wastes
• Repairs tissues
• Helps fight infections

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In circulation

• What needs to be transported
• nutritive
• nutrients fuels from digestive system
• respiratory
• O2 CO2 from to gas exchange systems lungs,
  gills
• excretory
• waste products from cells
• water, salts, nitrogenous wastes (urea)
• protection
• blood clotting
• immune defenses
• white blood cells others patrolling body
• regulation
• hormones

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Invertebrate Circulation ?Simple Diffusion

• Body cavity 2-cell layers think
• all cells within easy reach of fluid
• use gastrovascular cavity for exchange

Cnidarians
Hydra
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Circulatory systems

• All animals have
• circulatory fluid blood
• tubes blood vessels
• muscular pump heart
• Open or Closed Systems

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Open circulatory system

• Taxonomy
• invertebrates
• insects, arthropods, mollusks
• Structure
• no distinction between blood extracellular
  (interstitial) fluid
• hemolymph

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Closed circulatory system

• Taxonomy
• invertebrates
• earthworms, squid, octopuses
• vertebrates
• Structure
• blood confined to vessels separate from
  interstitial fluid
• 1 or more hearts
• large vessels to smaller vessels
• material diffuses between vessels interstitial
  fluid

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Vertebrate Circulatory System

• Closed system
• number of heart chambers differs
• Whats the adaptive value of a 4 chamber heart?
• 4 chamber heart is double pump separates
  oxygen-rich oxygen-poor blood

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Survey of Vertebrate Circulation

• Humans and other vertebrates have a closed
  circulatory system
• Often called the cardiovascular system
• Blood flows in a closed cardiovascular system
• Consisting of blood vessels and a two- to
  four-chambered heart
• A powerful four-chambered heart
• Was an essential adaptation of the endothermic
  way of life characteristic of mammals and birds

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Fishes

• A fish heart has two main chambers
• One ventricle and one atrium
• Blood pumped from the ventricle
• Travels to the gills, where it picks up O2 and
  disposes of CO2

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Amphibians

• Frogs and other amphibians
• Have a three-chambered heart, with two atria and
  one ventricle
• The ventricle pumps blood into a forked artery
• That splits the ventricles output into the
  pulmocutaneous circuit and the systemic circuit

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Reptiles (Except Birds)

• Reptiles have double circulation
• With a pulmonary circuit (lungs) and a systemic
  circuit
• Turtles, snakes, and lizards
• Have a three-chambered heart

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Mammals and Birds

• In all mammals and birds
• The ventricle is completely divided into separate
  right and left chambers
• The left side of the heart pumps and receives
  only oxygen-rich blood
• While the right side receives and pumps only
  oxygen-poor blood

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Evolution of vertebrate circulatory system
heart structure increasing body size
fish
amphibian
reptiles
birds mammals
2 chamber
3 chamber
3 chamber
4 chamber
V
A
A
A
A
A
A
A
V
V
V
V
V
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Driving evolution of CV systems

• Metabolic rate
• endothermy higher metabolic rate
• greater need for energy, fuels, O2, waste removal
  
• more complex circulatory system
• more powerful hearts

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The Cardiac Cycle

• A rhythmic cycle ? the heart contracts and
  relaxes
• Systole ? contraction, or pumping, phase of the
  cycle
• Diastole ?relaxation, or filling, phase of the
  cycle

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Pulse and Cardiac Output

• 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

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Maintaining the Hearts Rhythmic Beat

• Some cardiac muscle cells are self-excitable?
  they contract without any signal from the nervous
  system
• A region of the heart called the sinoatrial (SA)
  node, or pacemaker
• Sets the rate and timing at which all 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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Electrocardiograms(ECG or EKG)

• Recorded impulses that travel during the cardiac
  cycle

The control of heart rhythm
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Blood Vessel Structure and Function

• The infrastructure of the circulatory system
• Is its network of blood vessels

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Blood Vessels

• The infrastructure of the circulatory system
• Is its network of blood vessels
• Arteries carry blood to capillaries
• The sites of chemical exchange between the blood
  and interstitial fluid
• Veins
• Return blood from capillaries to the heart

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Blood Vessels
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Structural differences in arteries, veins, and
capillaries

• Correlate with their different functions
• Arteries have thicker walls
• To accommodate the high pressure of blood pumped
  from the heart
• In the thinner-walled veins
• Blood flows back to the heart mainly as a result
  of muscle action

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Blood Pressure

• The hydrostatic pressure that blood exerts
  against the wall of a vessel
• Systolic pressure
• Is the pressure in the arteries during
  ventricular systole
• Is the highest pressure in the arteries
• Diastolic pressure
• Is the pressure in the arteries during diastole
• Is lower than systolic pressure

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Blood Pressure
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Figure 42.13 The movement of fluid between
capillaries and the interstitial fluid
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Figure 43.4 The human lymphatic system
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Blood Composition and Function

• Blood consists of several kinds of cells
• Suspended in a liquid matrix called plasma
• The cellular elements
• Occupy about 45 of the volume of blood

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Plasma

• Blood plasma is about 90 water
• Among its many solutes are
• Inorganic salts in the form of dissolved ions,
  sometimes referred to as electrolytes
• Another important class of solutes is the plasma
  proteins
• Which influence blood pH, osmotic pressure, and
  viscosity
• Various types of plasma proteins
• Function in lipid transport, immunity, and blood
  clotting

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Cellular Elements

• Suspended in blood plasma are two classes of
  cells
• Red blood cells, which transport oxygen, most
  numerous
• White blood cells, which function in defense
• A third cellular element, platelets
• Are fragments of cells that are involved in
  clotting

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Figure 42.14 The composition of mammalian blood
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Figure 42.15 Differentiation of blood cells
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Leukocytes

• The blood contains five major types of white
  blood cells, or leukocytes
• Monocytes, neutrophils, basophils, eosinophils,
  and lymphocytes, which function in defense by
  phagocytizing bacteria and debris or by producing
  antibodies

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Stem Cells and the Replacement of Cellular
Elements

• The cellular elements of blood wear out
• And are replaced constantly throughout a persons
  life

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Erythrocytes, leukocytes, and platelets all
develop from a common source

• A single population of cells called pluripotent
  stem cells in the red marrow of bones

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Blood Clotting

• When the endothelium of a blood vessel is damaged
• The clotting mechanism begins

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Cardiovascular Disease

• Cardiovascular diseases
• Are disorders of the heart and the blood vessels
• Account for more than half the deaths in the
  United States

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

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• 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

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Gas Exchange

• Supplies oxygen for cellular respiration and
  disposes of carbon dioxide

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Gills in Aquatic Animals

• Animals require large, moist respiratory surfaces
  for the adequate diffusion of respiratory gases
• Between their cells and the respiratory medium,
  either air or water

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Gills in Aquatic Animals

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

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In some Invertebrates

• The gills have a simple shape and are distributed
  over much of the body

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Segmented Worms

• Have flaplike gills? extend from each segment of
  their body

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Gills of clams, crayfish, and many other animals

• Are restricted to a local body region

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Fish Gills
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Tracheal Systems in Insects

• Consists of tiny branching tubes that penetrate
  the body

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• The tracheal tubes
• Supply O2 directly to body cells

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Lungs

• Restricted to one location

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Human Anatomy

• Nares
• Pharynx
• Larynx/Epiglottis
• Glottis
• Trachea
• Bronchi
• Bronchioles
• Alveoli
• Lungs
• Diaphragm

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Microscopic Anatomy

• Bronchioles
• Alveoli
• Blood Supply
• Pulmonary A/V
• Bronchial A/V

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Mechanism of Breathing
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When you breathe in . . .
Vagus Nerve
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How an Amphibian Breathes

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

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How a Bird Breathes

• Besides lungs, bird have eight or nine air sacs
• That function as bellows that keep air flowing
  through the lungs

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Autonomic Breathing Control

• Medulla sets rhythm
• Pons moderates rhythm
• Chemoreceptors
• Baroreceptors
• Carotid, aorta

Vagus Nerve
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• 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

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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

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• A gas always diffuses from a region of higher
  partial pressure
• To a region of lower partial pressure

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• In the lungs and in the tissues
• O2 and CO2 diffuse from where their partial
  pressures are higher to where they are lower

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Figure 42.27
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Respiratory Pigments

• Respiratory pigments
• Are proteins that transport oxygen
• Greatly increase the amount of oxygen that blood
  can carry
• Hemoglobin must reversibly bind O2, loading O2 in
  the lungs and unloading it in other parts of the
  body

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Transport of Oxygen

• 98.5 bound to hemoglobin
• 1.5 dissolved in plasma

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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

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Elite Animal Athletes

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

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The Ultimate Endurance Runner

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

Figure 42.31
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Diving Mammals

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