CHAPTER 22 Respiration: The Exchange of Gases MECHANISMS OF GAS EXCHANGE Gas exchange is the...
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Transcript of CHAPTER 22 Respiration: The Exchange of Gases MECHANISMS OF GAS EXCHANGE Gas exchange is the...
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CHAPTER 22Respiration: The Exchange of
Gases
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MECHANISMS OF GAS EXCHANGE
• Gas exchange is the interchange of O2 and CO2 between an organism and its environment– It is also called respiration
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Overview: Gas exchange involves breathing, the transport of gases, and the servicing of
tissue cells
• Gas exchange is essential because energy metabolism requires O2 and produces CO2
CO2
O2 ATP
food
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Animals exchange O2 and CO2 through moist body surfaces
• O2 enters an animal and CO2 leaves by diffusion through a respiratory surface – Respiratory surfaces are made up of living cells
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Lungs
alveoli
trachea bronchi bronchioles alveoli
capillaries(circulatory system)
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The human respiratory system
• In humans and other mammals, air enters through the nasal cavity – It passes through the
pharynx and larynx into the trachea
– The trachea forks to form two bronchi
– Each bronchus branches into numerous bronchioles
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The human respiratory system
• The bronchioles end in clusters of tiny sacs called alveoli
• Alveoli form the respiratory surface of the lungs– Oxygen diffuses
through the thin walls of the alveoli into the blood
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Connection: Smoking is one of the deadliest assaults on our respiratory system
• Mucus and cilia in the respiratory passages protect the lungs– Pollutants, including
tobacco smoke, can destroy these protections
• Smoking kills about 430,000 Americans each year
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Connection: Smoking is one of the deadliest assaults on our respiratory system
• Smoking causes lung cancer and contributes to heart disease
• Smoking also causes emphysema– Cigarette smoke
makes alveoli brittle, causing them to rupture
– This reduces thelungs’ capacity for gas exchange
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Breathing ventilates the lungs
• Breathing is the alternation of inhalation (active) and exhalation (passive)
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Negative pressure breathing• Diaphragm moves down & expands chest cavity
pulls air into lungs
inhale exhale
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Automatic Brain Control• You don’t have to think to breathe!– medulla & pons– measure blood pH• CO2 = pH (acid)
– coordinate breathing, heart rate & body’s need for energy
– Medulla oblongata will stimulate diaphragm to contract.
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TRANSPORT OF GASES IN THE BODY
• Blood transports the respiratory gases, with hemoglobin carrying the oxygen
• The heart pumps oxygen-poor blood to the lungs– In the lungs it picks up O2 and drops off CO2(external
respiration)
– In the tissues, cells pick up CO2 and drop off O2-(Internal respiration)
– Gases diffuse down pressure gradients in the lungs and the tissues
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Gas exchange: Diffusion of gases• Gases move by diffusion from high to low
concentration– capillaries are thin-walled tubes of circulatory
system– alveoli are thin-walled sacs of respiratory system
blood lungs
CO2
O2
CO2
O2
blood body
CO2
O2
CO2
O2
capillaries in lungs capillaries in muscle
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Gas exchange in the body
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Hemoglobin is a protein in red blood cells
– It carries most of the oxygen in the blood
Hemegroup Iron
atom
O2 loadedin lungs
O2 unloadedin tissues
Polypeptide chain
O2
O2
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Hemoglobin helps transport CO2 and buffer the blood
• Hemoglobin helps buffer the pH of blood and carries some CO2
• Most CO2 in the blood combines with water to form carbonic acid– The carbonic acid breaks down
to form H+ ions and bicarbonate ions
– These help buffer the blood
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Transport of CO2
• Most CO2 is transported to the lungs in the form of bicarbonate ions
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Connection: The human fetus exchanges gases with the mother’s bloodstream
• A human fetus depends on the placenta for gas exchange
• A network of capillaries exchanges O2 and CO2 with maternal blood that carries gases to and from the mother’s lungs
• At birth, increasing CO2 in the fetal blood stimulates the fetus’s breathing control centers to initiate breathing
Placenta, containingmaternal blood vesselsand fetal capillaries
Umbilical cord,containing fetalblood vessels
Uterus
Amnioticfluid
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Breathing and Homeostasis• Homeostasis– keeping the internal environment of the
body balanced– need to balance O2 in and CO2 out
– need to balance energy (ATP) production• Exercise– breathe faster
• need more ATP• bring in more O2 & remove more CO2
• Disease– poor lung or heart function = breathe faster
• need to work harder to bring in O2 & remove CO2
O2
ATP
CO2
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Disorders of the Respiratory system
• Asthma: a severe allergic reaction in which contraction of the bronchioles makes breathing difficult
• Bronchitis: an inflammation of the lining of the bronchial tubes. The passageways to the alveoli become swollen and clogged with mucus
• Emphysema: lungs lose their elasticity, deterioration of the lung structure
• Pneumonia: alveoli become filled with fluid. Caused by bacterial or viral infection
• Lung Cancer: a disease in which tumors form in the lungs as a result of irregular and uncontrolled cell growth