Download Ventilation and Alveolar Gas Exchange

Ventilation!
What are the two main functions of
the respiratory system?
1. VENTILATION
2. RESPIRATION
• Today’s topic is PULMONARY VENTILATION
(a.k.a. breathing)
So, what is breathing?
• Movement of air from outside the body into
and out of the bronchial tree and alveoli
1. Inspiration (inhalation)- air flowing into lungs
2. Expiration (exhalation) – air leaving lungs
Bellwork (well after the bell…)
1) Particles move from areas of
concentration to areas of
concentration.
2) What is air pressure or atmospheric
pressure?
3) What causes hiccups?
4) What is the purpose of yawning?
The FORCE behind breathing
• ATMOSPHERIC PRESSURE!
• Rules of thumb:
– Volume changes lead to pressure
changes
– Volume (V) and pressure (P) are
inversely related
• As volume decreases, pressure increases
• As volume increases, pressure decreases.
– Gases flow from areas of high pressure
to areas of low pressure
Steps of Inspiration
1. Diaphragm and
intercostal muscles
contract
2. Thoracic cavity
increases
3. Volume of lungs
increases
4. Pressure within lungs
decreases
5. Air enters lungs
Steps of Expiration
1. Inspiratory muscles
relax
2. Volume of thoracic
cavity and lungs
decreases
3. Pressure in lungs
increases
4. Gases flow out of
lungs
Compare and Contrast
Inspiration
Intercostal
Diaphragm
Thorax
volume
Air pressure
Result
Expiration
Inspiration
Expiration
Intercostals
Contract (out)
Relax (in)
Diaphragm
Contract
(downward)
Relax (upward)
Thorax
volume
Air pressure
Increases
Decreases
Decreases
Increases
Result
Air in
Air out
Misc. ventilation air movements
(Thanks to reflexes!)
•
•
•
•
•
Cough: clear lower respiratory passages
Sneeze: clear upper respiratory passages
Crying: emotional response
Laughing: emotional response
Hiccups: spasms of diaphragm causes air to strike
vocal cords. What’s the function of hiccups?
Don’t know.
• Yawn: ventilates all alveoli in response to low
blood oxygen concentration
Respiratory Air Volumes and Capacities
• Factors affecting lung capacity
– Size
– Sex
– Age
– Physical Condition
– Lifestyle choices
Respiratory Volumes
• Respiratory volumes: four different volumes
of air that move in or out of the lungs based
on breathing intensities
• Respiratory cycle: one inspiration plus the
following expiration
How much air do you think moves
in and out of your lungs when you
breathe normally?
Respiratory Volume and Capacities
1. Tidal Volume
– Amount of air moved in and out during normal
breathing (one cycle) = 500 ml or a pint
2. Inspiratory Reserve Volume
– Amount of air that can be taken in with force
(deep breath)= 3,000 ml
Respiratory Volume and Capacities
3. Expiratory Reserve Volume
– Amount of air that can be forcibly exhaled after a
tidal expiration or in addition to the tidal
expiration = 1200 ml
4. Residual Volume
– Air that cannot be voluntary expelled and remains
in lungs to keep gas exchange continuous (1200
ml)
TRY TO BREATHE ALL THE AIR OUT
OF YOUR LUNGS!
• Oops. You can’t! This is because there is
always a…
4. Residual Volume
– Air that cannot be voluntary expelled and remains
in lungs to keep gas exchange continuous = 1200
ml
Pulmonary Ventilation:
Respiratory Volume and Capacities
1. Vital Capacity (VC)
– Maximum amount of air a person can exhale after
taking the deepest breath possible (4800 ml)
– Tidal volume + inspiratory reserve + expiratory
reserve
– VC = TV + IRV + ERV
2. Total lung capacity
-
Vital Capacity + Residual volume
Alveolar Gas Exchange
Bellwork (round 2!)
1. What is air made of?
2. Gases move from (high/low) pressure to
(high/low) pressure.
3. Describe what simple squamous cells look
like.
4. What is respiration?
Respiratory Membrane: Structure
• Respiration: process of gas exchange between
the atmosphere and the cells
• Wall of the alveoli are made of simple
squamous cells
• Respiratory membrane: squamous epithelial
cells 2 cell layers thick that separate air in the
alveolus from blood in the capillary
– Contains basement membranes and cartilage
Respiratory Membrane: Function
• What is the function of the respiratory
membrane?
– Hint: What is respiration?
– Function: Diffusion of gases
• Gases move from
pressure to
pressure.
• The pressure of a gas determines its rate of
diffusion
Atmospheric/Alveolar Partial Pressure
• So what gases do we breathe?
– 78% Nitrogen
– 21% Oxygen
– .04% Carbon Dioxide
• Atmospheric pressure is 760 mm Hg
• Each gas in the atmosphere/alveoli has a
partial pressure
– PO2 = 760 mm Hg * .21
– PCO2 =
Partial Pressure in Blood
• When gases are dissolved in liquid, the
concentration (or amount) of each gas is
proportional to the partial pressure
• PO2 = 40 mm Hg
• PCO2 = 45 mm Hg
P CO2
P O2
Partial Pressure
in Alveoli
(atmosphere)
40
104
Partial Pressure
in capillaries
(Blood)
45
40
Given the differences in pressure which
direction will each gas move?
• CO2 moves into the alveoli
• O2 moves into the capillaries
• The blood that is delivered to the tissues has
these partial pressures: CO2 = 40 mm Hg, O2 =
104 mm Hg
Steps of RESPIRATION (gas
exchange between atmosphere
and cells)
I. Ventilation
II. Gas exchange between blood and air in the
alveoli  external respiration
III. Gas transport in blood between lungs and
body cells
IV. Gas exchange between blood and body cells
 internal respiration
Review (These are really important
points!)
REALLY IMPORTANT POINTS ABOUT GAS
EXCHANGE:
1. Describe the structure of the respiratory
membrane.
2. How does this structure allow it to perform
its function?
3. Oxygen diffuses from the
to
the
.
Review (These are really important
points!)
REALLY IMPORTANT POINTS ABOUT GAS
EXCHANGE:
4. Carbon dioxide diffuses from the
to the
.
5. What force moves oxygen and carbon dioxide
across the respiratory membrane?
6. The large surface area of alveoli increases the
rate diffusion across the respiratory
membrane.
A. OXYGEN
III. O2 transport in blood between lungs and body cells
1) Once O2 crosses the
respiratory membrane
in the lungs, it binds to
an iron-containing
protein in red blood
cells called
hemoglobin
•
•
“heme” = iron
Globin = type of
protein
•
http://www.nytimes.com/imagepages/2007/08/
01/health/adam/19510Hemoglobin.html
A. OXYGEN
III. O2 transport in blood from lungs to body cells
2) Bound to hemoglobin,
blood delivers O2 to
body cells
A. OXYGEN
IV. O2 exchange between blood and body cells
1) As O2- carrying blood moves from the lungs
(PO2 = 95 mm Hg), the surrounding oxygendepleted tissues have a very low PO2 (40
mmHg)
2) O2 diffuses from (blood/tissues) to
(blood/tissues).
3) After O2 diffuses, PO2 in blood returning to
the lungs is 40 mmHg
B. CO2
IV. CO2 exchange between body cells and blood
1) The PCO2 in tissues is 45 mm Hg while the
PCO2 in blood is 40 mm Hg
2) Thus, CO2 diffuses from (tissues/blood) into
(tissues/blood)
3) The blood returning to the lungs has a PCO2
of 45 mmHg
B. CO2
III. CO2 transport from body cells to lungs
• CO2 is transported in blood as
1) CO2 dissolved in the plasma
2) Bound to hemoglobin
3) As bicarbonate (HCO3-) ion
• Wait, isn’t O2 bound to hemoglobin? How
can hemoglobin bind both molecules?
•
Different binding sites
• Difference in PCO2 at lungs allows CO2 to
diffuse from blood to lungs
Note to Mr. Bell:
Pass out notecards for
pop test!!
Reading Test!
Write your name, date, and period on the index
card and answer these questions.
1) The protein in blood that transports oxygen
from lungs to cells is called
.
2) Name one form in which blood can transport
carbon dioxide from cells to the lungs.
Reading Test!
Write your name, date, and period on the index
card and answer these questions.
1) A deficiency of oxygen reaching the body
tissues is called
.
2) Name one form in which blood can transport
carbon dioxide from cells to the lungs.