Transcript lecture16-pulm

Respiratory Physiology
[the Ins and Outs]
Jim Pierce
Bi 145a
Lecture 16, 2009-10
The Lungs
The Lungs
Pulmonary Tree
Trachea and Esophagus
Trachea
Respiratory
Epithelium
Respiratory
Epithelium
Explained
Brush Border and Goblet Cells
Structure of the Distal Airway
Alveoli
Terminal
Bronchioles,
Respiratory
Bronchioles,
and Alveoli
Blood Supply of the Distal Airway
Alveolar Membrane (TEM)
Pulmonary
Circulation
Lungs
in situ
Bronchial Arteries
The
Diaphragm
Accessory Muscles
Upper Airway Development
Upper Airway Development
Upper Airway Development
Airway Budding
Airway Budding
Airway Budding
Growing into the Pleural Cavity
Lower Airway Development
Lower Airway Development
Airway Maturation
Airway Maturation
Airway Maturation
Airway Maturation
Capillary Blood Flow
Lung Physiology
 The Lung has three jobs
 Absorb Oxygen
 Excrete Carbon Dioxide (and affect pH)
 Neurohormal and Hematopoetic Function
 (Remember - it’s a filter that all of
the blood must traverse)
Lung Physiology
 It’s not surprising to find
Neurohormonal Function
 (note that 100% of the Cardiac Output
must cross the lung)
 Thus, the body has placed a variety of enzymes on the
vascular endothelium.
Metabolic Roles
Lung Physiology
 Do Not Forget that the lung is a Neurohormonal Organ
 People do because the gas exchange physiology is very
interesting.
 Perhaps the role of the lung in immunologic dysfunction
is more interesting.
Lung Physiology
 Furthermore, Multipotent Stem Cells, Reticulocytes,
and Megakaryocytes sometimes escape from the bone
marrow and wedge into the lung microvasculature.
 They finish differentiation because of the presence of
Reticular Fibers
Pulmonary Physiology
 So we need to ask:
 1) How do we BREATHE?
 That is, get air in and out of the lungs
 What are the parts of the airway and lungs that allow us to
move the air? What are the muscles that move the air in and out?
What controls them?
Pulmonary Physiology
 2) How do we VENTILATE?
 That is, how do we get air to the alveoli?
 What causes the movement of air to get to the terminal
respiratory tract? What are the volumes of air that are breathed
that make it there? How does the air distribute in the lung?
What factors affect the distribution of air in the lungs?
Pulmonary Physiology
 3) How do we PERFUSE the lung?
 That is, how does blood flow in the lung?
 What brings the blood to the lungs? How is the blood flow
distributed around the lungs? Where does the blood go? Where
does the interstitial fluid go? What factors affect the regulation
of blood flow?
Pulmonary Physiology
 4) How do we EXCHANGE GASES?
 That is, how do we get the O2 in and the CO2 out?
 What factors affect diffusion from the alveoli to the capillary?
How does blood flow affect the balance of gases? How does
ventilation affect the balance of gases? When is the exchange
blood flow limited? When is the exchange ventilation limited?
Pulmonary Physiology
 5) How do we match VENTILATION and PERFUSION?
 That is, how do we make the blood and air go to the same
place?
 What regulatory factors insure that ventilated lung are
perfused? What factors insure that perfused lung is ventilated?
How do we turn off perfusion or ventilation when the lung is
not ventilating or perfusing?
Pulmonary Physiology
 6) How do we adjust pulmonary function to compensate for
changes in the periphery?
 Increase in Oxygen Demand
 Increase in Carbon Dioxide Production
 Change in pH
Breathing
 In the medulla, there is a respiratory center
 This center takes “respiratory inputs”
 Then it produces “respiratory outputs”
 Thus, it is directly responsible for controlling breathing (rate
and depth)
Breathing
 The medullary respiratory assesses
 Local (i.e. brain) pH
 Local pCO2
 Afferent signals from the brain (thinking)
 Afferent signals from the periphery
 carotid bulb
 Heart, Lung
 The primary force on breathing is pCO2
Breathing
 The medullary respiratory center indicates:
 Frequency of Initiation of inspiration
 Duration of inspiration
 Force of inspiration
 Inspiratory / Expiratory pause
 Expiratory duration
 Expiratory force
Breathing
 The respiratory cycle:
 Inspiration
 Inspiratory Pause (usually zero)
 Expiration
 Expiratory Pause
Breathing
 How do we inspire?
 How do we expire?
Breathing
 The brain controls the muscles of breathing indicating the
respiratory rate.
 C3, C4, C5 nerve roots innervate the diaphragm via the
phrenic nerve
 Other Cervical and Thoracic roots innervate the accessory
muscles.
Breathing – ACTIVE FORCE
 Muscles of Breathing:
 Principle Muscles
 Diaphragm
 Intercostal
 Accessory Muscles
 There are no skeletal muscles in the lung
The
Diaphragm
Accessory Muscles
Breathing – PASSIVE FORCE
 The connective tissue of the chest wall
 Determines the minimum and maximum
volume of the chest cavity
 Does not control the minimum or maximum
lung volume
 The connective tissue of the lung
 Primarily is elastic and tends to collapse
 Has some stiffness from connective tissue
Chest Wall
Remember:
Chest wall is
Separate from
Lung
Lungs Grew into the Pleural Cavity
Chest Wall
Lung
Chest Wall and Lung
 The total force from muscles of the chest wall tend to
Expand the Chest
 The lung – with no muscles but lots of elastic tissue – tends
to collapse
Chest Wall and Lung
Chest Wall and Lung
The “negative”
pressure keeps
the lungs
“stuck” to the
chest wall
(it’s not truly negative – it’s actually just 5 below atmospheric)
Breathing
The overall ability
of the chest and lung
to allow a change in
airway pressure based
on volume moved is
COMPLIANCE
Chest Wall and Lung
 When the muscles relax, the equilibrium
is at the end of a comfortable exhale
 It is possible to contract muscles
 To exhale more
 To inhale
 (We have “exhale” and “inhale” reserve)
Chest Wall and Lung
 Why?
 It’s like a garage door opener:
 The balance of the heavy door and
powerful spring keeps the “net mass” very low, making it easy
to open and close
Chest Wall and Lung
 Like the garage door opener:
 The balance of the chest wall expansion
and lung contraction keeps the “net mass” very low, making it
easy to open and close
Inspiration
 When inspiratory muscles contract…
 The Thoracic Cage expands…
Inspiration
 The thoracic
cage expands
both anteriorly
and laterally
Inspiration
 This is done by rib
and sternum
movement
 Ribs move
like a
bucket handle
Inspiration
 Sternum moves like a
water pump
Inspiration
Together, the
thorax expands
Breathing
 When inspiratory muscles contract…
 The Thoracic Cage expands…
 Generating a negative pressure
On the Pleural Space
Breathing
 As the Chest wall expands,
the negative pressure
in the pleural space
actively expands the lung
Breathing
 Thus, the negative inspiratory force is transmitted from chest
wall to lung -TRANSMURAL!
 This leads to a pressure gradient between the mouth and
lung…
 Which leads to gas flow.
Ventilation
 Once we get negative pressure on the lung, we observe a net
flow of air.
 P = Q * R
 Pressure gradient
 Flow
 Resistance (of airways)
Inspiration
 All inspiration is active:
 Force is required to expand the thorax
and draw air into the lungs
Exhalation
 Exhalation can be either active or passive
 Passive exhalation is the “relaxation”
of the inspiratory muscles
 Active exhalation is the contraction
of the axial skeletal muscles
Passive Exhalation
 During passive exhalation
 The inspiratory muscles relax
 The lung recoil is greater than
the chest expansive force
 Thus, the lung and chest contract.
 This increases the pressure inside the lung
 This causes a pressure gradient,
leading to airflow out through the airways
Passive Exhalation
 One can prevent passive exhalation
without continuous use of force.
 By closing the epiglottis, the airways are “disconnected” from
the environment.
 Regardless of the pressure gradient,
no air will flow
Active Exhalation
 During active exhalation
 Intercostal, Abdominal muscles Contract
 This brings the chest to its smallest volume
and braces it while the abdominal organs are
forced upward into the diaphragm
 This increases the pressure in the chest cavity as well as in the
lungs.
 As long as the airways remain open, Air will flow down the
pressure gradient
Active Exhalation
Active Exhalation
 During active exhalation
 As long as the airways remain open, Air will flow down the
pressure gradient
 Active exhalation with a closed epiglottis
prepares you for a cough.
 Active exhalation at the end of passive exhalation produces only
a small, slow exhale because the small airways have collapsed
Chest Wall and Lung
Chest Wall and Lung
Questions?