Respiratory 2 PPT

Collin County Community College
BIOL. 2402
Anatomy & Physiology
WEEK 9
Respiratory System
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Respiratory Zone
Respiratory Zone
Starts where the terminal bronchioli feed into the
respiratory bronchioli
Respiratory bronchioli feed into alveolar ducts that end
in clusters of alveolar sacs
There are roughly 300 million alveolar sacs = surface
area for gas exchange
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1
Respiratory Zone
[AIR]
EXCHANGE
[BLOOD]
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Respiratory Zone
Each of the clustered
alveoli includes an
abundance of
pulmonary capillaries,
thereby assuring that
the ventilated air is
brought into close
proximity to the
“pulmonary” blood,
allowing efficient and
thorough gas
exchange between the
air and the blood.
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2
Respiratory Zone
Wall of alveolus is made up from simple squamous epithelial
cells (called Type I cells)
Type II cells
produce
surfactant
Dust cells
(macrophages)
keep alveoli clean
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Respiratory Membrane
The Respiratory Membrane is made up from :
• Squamous epithelial cells of alveoli
• endothelial cells of the capillary wall
• basement membranes of each layer
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3
Respiratory Membrane
The Respiratory Membrane is the area across which gas
exchange occurs
These Alveolar and capillary walls are thin, permitting rapid
diffusion of gases.
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Respiratory Membrane
Fick’s Equation for Diffusion
Rate = A. D. (C2 - C1) / x
(C2 - C1) = Conc. gradient
X = Resp. membrane thickness
A = Total alveolar area
Type II cells produce
surfactant ; this keeps
the alveoli from
collapsing
D = Diff. constant for a molecule
Depends on MW, Temp,
medium
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4
Fick’s Equation for Diffusion
and Respiration !
Rate = A. D. (C2 - C1) / x
So what happens when x increases, A
decreases, C2 decreases, C1 increases ?
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Lungs
Both lungs rest on the diaphragm.
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5
External Lung Anatomy
Left lung has 2 lobes
Right lung has 3 lobes
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Lungs
Just like the heart, the lungs are enclosed by a set of
membranes called the pleura.
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6
Lungs
Diaphragm
Parietal pleura is attached to the thoracic wall and diaphragm.
Visceral pleura is attached to the lungs.
The intrapleural space is between the two pleura and is filled with13fluid
Lung Physiology
Ventilation
The first exchange in
respiratory physiology
is ventilation
It is the movement of air
between the lungs (alveoli)
and the environment =
breathing
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7
Lung Physiology
Inhalation of air occurs through the nasal passage ways or
via the mouth. Breathing through the nose has several
advantages
• Warms air to body temperature before it reaches the
alveoli
• Adds moisture
• Foreign material is filtered out
When air reaches trachea, it is at 37 C and 100% humidity
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Lung Physiology
Additional filtration occurs in trachea and bronchi by ciliated
pseudostratified epithelium
• mucus traps particles
• cilia move mucus upwards towards the pharynx
Smoking paralyzes the
movement of the cilia
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8
Lung Physiology
Cystic fibrosis : the most common lethal inherited disease
among Caucasions from Northern European descent (1 : 2500)
a defective Chloride channel prevents water to be formed by
the glands in the epithelium, resulting in a thick mucus that
clogs the airways.
Due to a mutation in
chromosome 7. It results in
a defective Chloride channel
and prevents water to be
formed by the glands in the
epithelium.
The result is a thickening of
the mucus that clogs the
airways.
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Lung Physiology
Boyle’s law states that the pressure of a fixed
number of molecules is related to the volume
of a container in which they are placed.
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9
Lung Physiology
Air flows because of a Pressure Gradient
Flow = Δ P / R
Airflow (F) is a function of the
pressure differences between
the atmosphere (Patm) and the
alveoli (Palv), divided by airflow
resistance (R).
Air enters the lungs when :Palv< Patm
Air exits the lungs when : Palv > Patm
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Lung Physiology
Obviously, we cannot change atmospheric pressure with
every breath.
The body however adjusts alveolar pressure to start the
process of air intake according to Boyle’s Law
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10
Lung Physiology
Pressure Systems in the lungs
• Pressure in the lungs (alveoli) = intra pulmonary pressure (Palv)
• Pressure within intrapleural cavity = intra pleural pressure (Pip)
• Pressure outside the lungs = atmospheric pressure (Patm)
(Palv) - (Pip) = transpulmonary pressure
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Lung Physiology
In Physics :
(Patm) = 760 mm Hg
In Respiratory Physiology
(Patm) = 0 mm Hg
Changes in the pressure of the intrapleural fluid (Pip) affect the pressure in
the alveolus. The difference between atmospheric pressure (Patm) and
alveolar pressure (Palv) is the major pressure driving ventilation.
Air flows into the lungs when Palv < Patm
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11
Lung Physiology
Forces working on the lungs
• Parietal pleura is attached to the thoracic wall
• The small distance between the two pleural membranes, together with
the adhesive character of fluids, results in a negative transpulmonary
force (outward force)
the two pleural membranes to stick to
each other like two glass plates
• The lungs have an elastic character and want to recoil inward , the
same way an balloon with no air collapses on itself.
At rest ( between breathing), this inward force equals the Pip
Since the parietal pleura is attached to the thoracic wall, it keep the
lungs open.
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Lung Physiology
(Patm) = 0 mm Hg
(Palv) = 0 mm Hg
(Pip) = - 4 mm Hg
Lung recoil = - 4 mm Hg
(Palv - Pip) = + 4 mm Hg
(Net) = 0 mm Hg
When airflow is stopped,the atmospheric pressure (Patm) and alveolar
pressure (Palv) are equal.
Alveolar collapse is prevented because the negative pressure of the
intrapleural fluid (Pip) is exactly offset by the elasticity of the lungs.
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12
Lung Physiology
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Lung Physiology
(Pip) = 0 mm Hg
Atelactasis = collapsed lung
Lung recoil = - 4 mm Hg
(Palv - Pip) = 0 mm Hg
(Net) = - 4 mm Hg
When the outer pleura is punctured, it equilibrates with atmospheric
pressure.
Alveolar collapse occurs because the absence of negative pressure of
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the intrapleural fluid (Pip) cannot offset the elastic recoil of the lungs.
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Lung Physiology
Ventilation Process
Inhalation or Inspiration
Exhalation or Expiration
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Lung Physiology
Inhalation or Inspiration
Initiated by contraction of the diaphragm
Since lungs have now a greater
volume, Palv will decrease !
Air flows into the lungs since now
Palv < Patm
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14
Lung Physiology
Additional help is provided by the
• external intercostal muscles.
• internal intercostal muscles.
They provide uplifting motion of the
ribcage and broaden the lateral and
length-wise dimensions, expanding
the volume of the lung area.
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Lung Physiology
Both actions stretches the lungs open and intrapulmonary
pressure drops.
The stretching of the thoracic cage also causes a drop in
intrapleural pressure.
The final result is that transpulmonary pressure goes
from - 4 mm Hg to about -6 mm Hg, with intrapulmonary
pressure being about 1 mm Hg lower than atmospheric
pressure.
Patm = 760 mm Hg
Palv = 760 mm Hg
Pip = 756 mm Hg
Patm = 760 mm Hg
Palv = 759 mm Hg
Pip = 754 mm Hg
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Inspiration is the result of
the expansion of the thoracic
cage in response to skeletal
muscle contraction.
The expansion reduces
alveolar pressure (Palv) below
atmospheric pressure (Patm),
so air moves into the lungs.
At the end of Inspiration,
equilibrium between inside and
outside is reached and
(Palv) = (Patm)
Air movement into the lungs
stops.
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Lung Physiology
Exhalation or expiration
Is purely a passive action due to the relaxation of the diaphragm
Air flows out of the lungs
because volume decreases and
thus Palv < Patm
Additional forced exhalation
takes place by involving rib
muscles and abdominal
muscles.
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16
Expiration is the result of
reducing the volume of the
thoracic cage; in a resting
person, this occurs in
response to skeletal
muscle relaxation.
The volume reduction increases
alveolar pressure (Palv) above
atmospheric pressure (Patm),
so air moves out of the lungs.
At the end of Expiration,
equilibrium between inside and
outside is reached and once
again, (Palv) = (Patm)
Air movement out of the lungs
stops.
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Lung Physiology
Tidal Volume :
• Amount of air moved in per breath
• Equal to the amount of air moved out
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17
Lung Physiology
inspiration
Cycles of inspiration and expiration result from cycles of pressure
changes. Note that the intrapleural pressure is always sub-atmospheric !
If it were equal to or greater than atmospheric pressure (as in a
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pneumothorax), then the alveoli would collapse, terminating gas exchange.
Lung Physiology
In Trained individuals, pressure differentials in the
alveoli can reach as much as - 30 mm Hg, and
intrapleural pressure can drop as much as - 18 mm
Hg.
This allows for maximum capacity inhalation.
In a similar way, exhalation can create
maximum alveolar pressures of + 100
mm Hg ( with glottis closed).
That’s why it is always a good idea to
exhale when lifting weights in order to
prevent to prevent alveolar damage.
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Lung Physiology
Mechanism of Breathing
• Quiet breathing (eupnea)
– Inhalation uses diaphragm and/or external intercostals muscles
– Exhalation is purely passive relaxation of these muscles
• Deep breathing or diaphragmatic breathing
• Costal breathing or shallow breathing
• Forced breathing (hyperpnea)
– Involves active inspiratory and active expiratory movements
– Uses the accessory muscles such as internal intercostals, abdominal
muscles
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