Respiratory System

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Respiratory System
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Cellular Respiration

• Most cells utilize cellular respiration to
  convert the chemical energy stored in nutrient
  macromolecules to the chemical energy utilized by
  cells ? ATP
• This process is an oxidation reaction ? a steady
  supply of oxygen is required to combust glucose
  to carbon dioxide and water

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Cellular Respiration
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Cellular Respiration

• Respiratory systems support cellular respiration
  by facilitating gas exchange of oxygen and carbon
  dioxide between the organism and the environment

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Evolution of Respiratory Systems

• Simple Diffusion gases are exchanged across the
  moist exterior surface of the organisms body
• e.g. single cell organisms sponges cnidaria
  and worms
• Gills large surface areas that are richly
  supplied with blood capillaries are in close
  contact with water containing dissolved gases
• e.g. some mollusks and crustacea and fish

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Evolution of Respiratory Systems

• Book Lungs a series of moist, page-like
  membranes within a chamber of the organism that
  facilitate gas exchange
• e.g. spiders and scorpions
• Tracheae system of highly branched tubes that
  extend from the exterior surface of the organism
  to every cell in its body
• e.g. insects

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Book Lungs
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Evolution of Respiratory Systems

• Lungs chambers containing moist, delicate
  respiratory surfaces that are protected within
  the body
• e.g. amphibia through to mammals

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Human Respiratory System

• Four distinct stages in respiration
• Breathing entrance and exit of air into and out
  of lungs
• External respiration gas exchange between air
  and blood
• Internal respiration gas exchange between blood
  and body cells
• Cellular respiration in body cells

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Human Respiratory System

• The human respiratory system consists of two
  distinct parts
• Conducting portion a series of passageways that
  carry air by bulk flow into the gas exchange
  portion
• Gas exchange portion membraneous sacs where
  gases are exchanged between air in sacs and blood
  in capillaries

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Conducting Portion

• Purpose to carry air to the respiratory
  membranes in the lungs
• Nose? Nasal cavity? Pharynx, or Mouth? Oral
  cavity? Pharynx (common chamber)
• Pharynx? Larynx (contain vocal cords)
• Larynx? Trachea (rings of cartilage)
• Trachea? Left or Right Bronchus
• Bronchus? Bronchioles
• Bronchioles? Alveoli (singular alveolus)

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The Lungs

• Paired, cone shaped organs that lie on either
  side of the heart in the thoracic cavity
• Right lung has 3 lobes, the left lung has 2 lobes
  (allowing room for the heart)
• Bronchus, bronchioles and alveoli are contained
  in each lung

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Conducting Portion

• As air travels through the conducting portion, it
  is
• Warmed
• Moistened
• Filtered
• by mucus and cilia (tiny hairs) that line the
  conducting portion

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Gas Exchange Portion - Alveolus

• Each lung contains approximately 300 million
  alveoli
• Individual alveoli are tiny 0.2 mm diameter
  but collectively the alveoli provide 70 square
  meters of surface area for gas exchange
• This surface area is the size of a tennis court,
  and is 40x the surface area of your skin

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Alveolus

• The alveoli cluster together at the end of a
  bronchiole like a cluster of grapes
• The cluster of alveoli are surrounded by an
  intricate network of blood capillaries
• Because the alveolus is only one cell layer
  thick, and the blood capillary is one cell layer
  thick, gases are able to move by diffusion
  between our blood and the air we breathe in
• This diffusion of gases is facilitated by a thin
  layer of water that coats the interior surface of
  each alveolus

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Gas Exchange External Respiration

1. High CO2/ low O2 blood is pumped from the right
   ventricle of the heart, through the pulmonary
   arteries, to the capillaries that surround each
   alveolus
2. The air in the alveoli is high in oxygen, so
   oxygen moves by diffusion into the blood of the
   alveolar capillaries
3. The blood in the lung capillaries is high in
   carbon dioxide, so carbon dioxide moves by
   diffusion into the alveoli sacs
4. High O2/ low CO2 blood leaves the alveolar
   capillaries, through the pulmonary vein, to the
   left atrium of the heart

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Gas Exchange Internal Respiration

1. The left ventricle pumps high O2/ low CO2 blood
   along the aorta and arteries to the capillaries
   that are in contact with individual cells
2. The blood in the body capillaries has more oxygen
   than the body cells, so oxygen diffuses from the
   blood into the body cells
3. The body cells have more carbon dioxide than the
   blood, so carbon dioxide diffuses from the body
   cells into the blood in the body capillaries
4. High CO2/ low O2 blood leaves the body
   capillaries, travels through veins and the vena
   cava to the right atrium

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Chemistry of Gas Exchange

• Oxygen
• lt5 of oxygen travels in blood as a dissolved gas
• gt95 of oxygen travels in blood attached to
  hemoglobin (oxyhemoglobin)

• Carbon Dioxide
• 10 of carbon dioxide travels in blood as
  dissolved gas
• 20 of carbon dioxide travels in blood attached
  to hemoglobin (carbaminohemoglobin)
• 70 of carbon dioxide reacts with water in blood
  plasma to form the bicarbonate ion (HCO3-)

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Hemoglobin

• Hemoglobin preferentially binds oxygen over
  carbon dioxide (but oddly, binds carbon monoxide
  preferentially over oxygen!)
• 1 hemoglobin molecule is able to bind 4 oxygen
  molecules
• Because of hemoglobin our blood can carry 70x
  more oxygen than it would as a dissolved gas in
  plasma

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Bicarbonate Ion

• CO2 H20 ? H2CO3 (carbonic acid)
• H2CO3 ? H HCO3-
• This reaction is catalyzed by carbonic anhydrase
  embedded in the capillary walls
• This reaction is reversible

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External Respiration

• HbCO2 ? Hb CO2 (g)?
• carbaminohemoglobin
• H HCO3- ? H2CO3
• H2CO3 ? H2O CO2 (g)?
• 4. Hb O2(g)? ? HbO2
• deoxyhemoglobin oxyhemoglobin
• HHb ? Hb H
• reduced hemoglobin

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HHb
HbCO2
O2
Hb
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Internal Respiration

1. HbO2 ? Hb O2
2. Hb CO2 ? HbCO2
3. CO2 H2O ? H2CO3
4. H2CO3 ? H HCO3-
5. Hb H ? HHb

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HbCO2
Hb
HHb
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Binding Capacity of Hemoglobin

• pH and temperature affect the binding capacity
  of hemoglobin
• Cooler temperature (37 C) and higher pH (7.40) of
  lungs raises oxygen binding capacity of
  hemoglobin to 98
• Warmer temperature (38 C) and lower pH (7.38) of
  body cells lowers the oxygen binding capacity of
  hemoglobin to 60

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Binding Capacity of Hemoglobin

• This is important as the hemoglobin/RBC in the
  lung capillaries want to be able to bind as much
  oxygen as possible from the air in the alveoli
• The hemoglobin/RBC in the body capillaries want
  to be able to release oxygen to the body cells
  and pick up carbon dioxide from the body cells

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Mechanics of Breathing

• Breathing is the entrance and exit of into and
  out of the lungs
• Exhalation Expiration air exiting the lungs
• Inhalation Inspiration air entering the lungs
• Breathing is a biomechanical process

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Features of Thoracic Cavity

• For breathing to occur, the thoracic cavity must
  be air-tight
• The interior of the thoracic cavity is lined with
  an air-tight membrane called the parietal pleura
• Each lung is surrounded with an air-tight
  membrane called the visceral pleura
• The space between the two pleura (interpleural
  cavity) contains a lubricant
• The muscular diaphragm seals the bottom of the
  thoracic cavity

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Thoracic Cavity
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Inhalation

1. Diaphragm contracts and drops down
2. Intercostal muscles in the rib cage contract and
   push up and out
3. The thoracic cavity increases in volume
4. Pressure in the lungs decreases
5. Air rushes into the lungs

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Inhalation
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Exhalation

• Diaphragm relaxes and moves up
• Intercostal muscles in the rib cage relax and
  move down and in
• The thoracic cavity decreases in volume
• Pressure in the lungs increases
• Air rushes out of the lungs

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Exhalation
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Stimuli for Breathing Inhalation

• Primary stimuli rising CO2 and H ion levels
  trigger the respiratory center in the medulla
  oblongata of the brain ? nerve impulse is sent
  along intercostal nerve to contract intercostal
  muscles and along phrenic nerve to contract
  diaphragm

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Stimuli for Breathing Inhalation

• Secondary stimuli decreasing O2 levels trigger
  chemoreceptors in carotid bodies of carotid
  arteries and aortic bodies of aorta ? nerve
  impulse to respiratory center of medulla oblongata

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Stimuli for Breathing Exhalation

• Primary stimulus as air moves into the lungs
  during inhalation, the alveoli sacs expand ? this
  stimulates stretch receptors around the alveoli ?
  initiates a nerve impulse sent to the respiratory
  center to turn off inhalation nerve impulse