Respiratory System

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Respiratory System

• Gas exchange

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W O R K T O G E T H E R

• Why do we breathe? Think of all the reasons why
  we need a respiratory system.

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Warning terminology!

• Respiration is used several different ways
• Cellular respiration is the aerobic breakdown of
  glucose in the mitochondria to make ATP.
• Respiratory systems are the organs in animals
  that exchange gases with the environment.
• Respiration is an everyday term that is often
  used to mean breathing.

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Respiratory system function

• Respiratory systems allow animals to move oxygen
  (needed for cellular respiration) into body
  tissues and remove carbon dioxide (waste product
  of cellular respiration) from cells.

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Gas exchange by Diffusion

• Some animals simply allow gases to diffuse
  through their skins.
• These animals have a low metabolic rate. Why?
• All of these are aquatic animals. Why?

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Specialized structures

• Structures specialized for gas exchange include
• gills (aquatic animals)
• spiracles (terrestrial insects)
• lungs (most terrestrial vertebrates)

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Countercurrent Exchange

• In a concurrent system, exchange is inefficient.
  Equilibrium is reached at one end.
• In a countercurrent system, equilibrium is not
  reached, so gas exchange continues, increasing
  efficiency.

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Fish Gills

• Fish increase gas exchange efficiency using
  countercurrent exchange.
• Running blood through the system in the opposite
  direction to water keeps a diffusion gradient
  throughout the entire exchange.

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Gills exchange gases in fish. What is the site of
gas exchange in mammals?

1. Alveoli
2. Tracheids
3. Bronchi
4. Esophagus

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W O R K T O G E T H E R

• Why are gills so widely seen in aquatic animals
  but not in land animals?
• One group of land animals that have gills is the
  Isopods (pill bugs and sow bugs). How can
  these organisms survive on land with gills?

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Human respiratory system

• Parts of the respiratory system include
• Trachea
• Bronchi
• Bronchioles
• Alveoli

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Moving air in and out

• During inspiration (inhalation), the diaphragm
  and intercostal muscles contract.
• During exhalation, these muscles relax. The
  diaphragm domes upwards.

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Alveoli

• The alveoli are moist, thin-walled pockets which
  are the site of gas exchange.
• A slightly oily surfactant prevents the alveolar
  walls from collapsing and sticking together.

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Circulation and Gas Exchange

• Recall the interconnection between circulation
  and the respiratory system.
• Gas exchange at the lungs and in the body cells
  moves oxygen into cells and carbon dioxide out.

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What happens when you breathe in?

1. The rib muscles relax.
2. The diaphragm contracts.
3. Air leaves the alveoli.
4. Air moves between the chest wall and the lung.

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W O R K T O G E T H E R

• Premature infants sometimes die of lung collapse
  and other lung problems. What might preemies be
  missing? How could this be remedied?

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In the alveolus

• The respiratory surface is made up of the alveoli
  and capillary walls.
• The walls of the capillaries and the alveoli may
  share the same membrane.

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Gas exchange

• Air entering the lungs contains more oxygen and
  less carbon dioxide than the blood that flows in
  the pulmonary capillaries.
• How do these differences in concentrations assist
  gas exchange?

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Oxygen transport

• Hemoglobin binds to oxygen that diffuses into the
  blood stream.
• What are some advantages to using hemoglobin to
  transport oxygen?

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Carbon dioxide transport

• Carbon dioxide can dissolve in plasma, and about
  70 forms bicarbonate ions.
• Some carbon dioxide can bind to hemoglobin for
  transport.

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At the cells

• Cells use up oxygen quickly for cellular
  respiration. What does this do to the diffusion
  gradient? How does this help cells take up
  oxygen?
• Cells create carbon dioxide during cellular
  respiration, so CO2 levels in the cell are higher
  than in the blood coming to them. How does this
  help cells get rid of oxygen?

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Diffusion of O2 from lungs to blood is rapid
because

1. Active transport moves oxygen.
2. Hemoglobin takes up oxygen, keeping plasma
   concentration low.
3. Blood plasma is oxygen-rich.

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Most of the oxygen in blood is

1. In the white cells.
2. Bound to hemoglobin.
3. Combined with carbon to make carbon dioxide.
4. Dissolved in the plasma.

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Effects of smoking

• Inhaled smoke contains
• CO2, which affects the CO2 diffusion gradient.
• carcinogenic chemicals that can trigger tumors.
• toxic nicotine, which paralyzes cilia that
  normally clean the lungs.

Gross, isnt it?
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Emphysema

• Besides cancer, smoking can also lead to
  emphysema. Alveoli become dry and brittle, and
  eventually rupture.
• Both active and passive smoking (second-hand
  smoke) can lead to can lead to lung problems.

All types of smoke, not just tobacco, can cause
cancers and emphysema.
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Cystic Fibrosis

• Cystic fibrosis is one of the most common
  inherited disorders in the Caucasian population
  in the U.S.
• CF is caused by mutation of a single gene, the
  CFTR gene, which controls salt balance in the
  lungs.

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Cystic Fibrosis

• A normal CFTR protein regulates the amount of
  chloride ions across the cell membrane of lung
  cells.
• If the interior of the cell is too salty, water
  is drawn from lung mucus by osmosis, causing the
  mucus to become thick and sticky.

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Cystic Fibrosis

• At this point there is no cure for CF, though
  there are therapies that have extended the lives
  of CF patients, including lung transplants.
• Gene therapy may one day insert good CFTR genes
  into lung cells to make them operate normally.

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Two lies and a truth which one is true?

1. Cigarette smoke cures colds because it kills
   bacteria in the lungs.
2. Nicotine is one of the most potent neurotoxins on
   earth.
3. Passive smoking is less harmful than regular
   smoking.

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W O R K T O G E T H E R

• When people quit smoking, if the lungs are not
  damaged they can often clean themselves because
  the cilia are no longer paralyzed. People with
  cystic fibrosis have trouble with lung infections
  because their lung mucus is thick and sticky.
  What roles do cilia and mucus play in lung
  health?