CHAPTER 22 Respiration: The Exchange of Gases

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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

O2
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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
capillaries (circulatory system)

• trachea
• bronchi
• bronchioles
• alveoli

alveoli
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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 dont have to think to breathe!
• medulla pons
• measure blood pH
• ?CO2 ?pH (acid)
• coordinate breathing, heart rate bodys 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

capillaries in lungs
capillaries in muscle
blood
lungs
blood
body
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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
O2 unloadedin tissues
O2
Polypeptide chain
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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 mothers 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 mothers lungs
• At birth, increasing CO2 in the fetal blood
  stimulates the fetuss breathing control centers
  to initiate breathing

Placenta, containingmaternal blood vesselsand
fetal capillaries
Umbilical cord,containing fetalblood vessels
Amnioticfluid
Uterus
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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

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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