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Sylvia S. Mader
Immagini e
concetti
della biologia
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
C8 - Respiratory
system
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Gas exchange
Respiration involves various processes:
•Ventilation - breathing
•External respiration - gas exchange
between the air and the blood in the
lungs
•Internal respiration - gas exchange
between the blood and the tissue fluid
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Gas exchange
Gas exchange needs moist respiratory
surfaces to occur.
Aquatic organisms spend up to 25% of the
energies to extract air from water.
Terrestrial organisms need to moisten
constantly the respiratory surfaces.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Direct respiration through surfaces
Small aquatic animals as cnidarians and plathelminthes
exchange gases directly with the external environment.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Branchial respiration
Aquatic invertebrates (mollusks and crustacean) and
vertebrates (fish) have specialized organs for gas
exchange called gills.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Direct respiration through canals
Insects use tracheae to deliver oxygen directly to
muscles.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Direct respiration through canals
Terrestrial vertebrates and marine mammals usually moist
air before it enters the lungs.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Gills
Water moves across the gills near the mouth. Fish use
countercurrent exchange to transfer oxygen efficiently
to blood.
Countercurrent
exchange
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Lungs
The respiratory system includes all structures that bring
air to the lungs.
The air is warmed and humidified
in the nasal cavity and mouth.
The glottis opens and the trachea
connects the larynx to the two
bronchi.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Bronchioles and alveoli
Bronchi branch into bronchioles that end in alveoli.
Alveoli compose the lung and are the site for gas
exchange with blood.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Smoking is dangerous
Short-term effects: nagging cough, diminished
sense of smell, premature aging of the skin.
Long-term effects: cancer, heart diseases,
aneurysm, pulmonary diseases, stroke.
Other effects: chance of premature birth, low birth
weight and stillbirth.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Inspiration and expiration
Inspiration consists of muscle contractions that lower the
diaphragm and raise the ribs. The negative pressure
causes the air to flow in.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Inspiration and expiration
During expiration the diaphragm muscles relax and air
flows out as the inner pressure increases.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Respiratory centers
Breathing rhythms are automatically controlled by the
respiratory center located in the medulla oblongata, in the
lowermost part of the brain stem.
Changing in blood pH can
cause variation in the
respiration speed rate.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Respiration and physical exercise
During exercise the respiratory system makes
adjustments in response to the duration and
intensity of the effort.
During exercises the amount of O2 needed and
CO2 produced increase. Consequently the blood
flow in both muscles and lungs must also increase.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
External and internal respiration
External and internal respiration take advantage
from the spontaneous gas diffusion between air
and blood.
In the lungs the oxygen partial pressure (PO2) is
higher while PCO2 is lower than in the blood.
Hence CO2 diffuses out of the blood into the lungs
and O2 diffuses out of the lungs into the blood.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Hemoglobin
Hemoglobin (Hb) is a red blood cells
protein involved in the transport of gases.
External respiration
•Hb combines with O2 to form HbO2.
•HCO3- forms H2CO3 which breaks down into H2O and CO2.
Internal respiration
•HbO2 releases O2 into cells.
•Hb combine with CO2.
•CO2 combine with water to form H2CO3 which then
becomes HCO3-.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
External and internal respiration
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Respiratory disorders
In restrictive pulmonary disorders, lung capacity is
reduces as the lugs have lost their elasticity.
In obstructive pulmonary disorders, air does not flow
easily in the airways. Common types are bronchitis,
emphysema and asthma.
Lung cancers are characterized by thickening and
callusing of cells lining the bronchi, loss of cilia,
formation of a tumor that eventually metastasizes.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012