Transcript 6.4 gas Exchange

Gas Exchange
IB Learning Objectives
• Distinguish between ventilation, gas exchange
and cell respiration
All Living things Respire.
Why living things must respire (breathe):
– Cellular Respiration – controlled release of
energy in the form of ATP from organic
processes in the cell
C6H12O6 + O2 ---> 6CO2 + 6H20 + ATP
– Gas Exchange -- Exchange of gases
(Oxygen, Carbon Dioxide) between an
organism and it environments
– Ventilation - process of "changing" or replacing
gas (Oxygen, Carbon Dioxide) in a space (ex:
lungs)
IB Assessment Statement
• Explain the need for a ventilation system
6.4.2 Explain the need for a ventilation system.(3)
•
A ventilation system is needed to maintain concentration gradients in
the alveoli
•
The steep concentration gradient across the respiratory surface is
maintained in two ways: by blood flow on one side and by air flow on
the other side. The ventilation system replaces diffuses oxygen
(keeping the concentration high) and removes carbon dioxide (keeping
the concentration low).
•
This means oxygen can always diffuse down its concentration gradient
from the air to the blood, while at the same time carbon dioxide can
diffuse down its concentration gradient from the blood to the air.
IB Learning Objective
• Draw and label a diagram of the ventilation
system, including trachea, lungs, bronchi,
bronchioles and alveoli
Gas exchange in multicellular animals (i.e.
Mammals)
• A ventilation system is a pumping mechanism
that moves air into and out of the lungs efficiently,
thereby maintaining the concentration gradient for
diffusion.
Ventilation System of Mammals
• Lungs are housed in the thorax
• Thorax – an airtight chamber formed by the rib
cage.
• The thorax is housed by ribs and its muscles
called intercostal muscles.
Ventilation System of Mammals
• Diaphragm – A sheet of muscle that separated
the thorax from the abdomen
• Pleural Membrane- internal surface of thorax,
which secretes pleural fluid
• Pleural Fluid - is a lubricating fluid from blood
plasma that protects the lungs from friction during
breathing movements
LE 42-24
Rib cage
expands as
rib muscles
contract
Air
inhaled
Rib cage gets
smaller as
rib muscles
relax
Air
exhaled
Lung
Diaphragm
INHALATION
Diaphragm contracts
(moves down)
EXHALATION
Diaphragm relaxes
(moves up)
Ventilation System of Mammals
LE 42-23
• Lungs connect to the
mouth via the trachea
• The trachea divides into
2 bronchi, on to each
lung
• Within the lungs the
bronchi divide into even
smaller bronchioles
Branch
from
pulmonary
vein
(oxygen-rich
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Larynx
Left
lung
Esophagus
Trachea
Right
lung
Bronchus
Bronchiole
Diaphragm
Heart
SEM
Ventilation System of Mammals
• The smallest bronchioles end in air sacs called
LE 42-23
alveoli.
Branch
from
pulmonary
vein
(oxygen-rich
blood)
Branch
from
pulmonary
artery
(oxygen-poor
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Alveoli
Larynx
Left
lung
Esophagus
Trachea
Right
lung
Bronchus
Bronchiole
Diaphragm
Heart
SEM
Colorized SEM
The Human Respiratory System
• Bronchioles subdivide
into millions of tiny air
sacs called alveoli.
Alveoli
Bronchiole
The Human Respiratory System
• Alveoli are grouped in
clusters.
• Alveoli have thin,
moist walls
• A network of
capillaries surrounds
each alveolus.
Pulmonary
artery
Pulmonary
vein
Capillaries
• Gas Exchange
• Gas exchange takes place in the alveoli.
LE 42-23
Branch
from
pulmonary
vein
(oxygen-rich
blood)
Branch
from
pulmonary
artery
(oxygen-poor
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Alveoli
Larynx
Left
lung
Esophagus
Trachea
Right
lung
Bronchus
Bronchiole
Capillary
Diaphragm
Heart
SEM
Colorized SEM
IB Learning Objective
• Draw and label a diagram of the ventilation
system, including trachea, lungs, bronchi,
bronchioles and alveoli
IB Learning Objective
• Describe the features of alveoli that adapt them to
gas exchange.
• Gas Exchange
• Gas exchange takes place in the alveoli.
LE 42-23
Branch
from
pulmonary
vein
(oxygen-rich
blood)
Branch
from
pulmonary
artery
(oxygen-poor
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Alveoli
Larynx
Left
lung
Esophagus
Trachea
Right
lung
Bronchus
Bronchiole
Capillary
Diaphragm
Heart
SEM
Colorized SEM
Cellular Respiration and Gas exchange
Diffusion:
–
Gas exchange between an individual cell and
its environment takes place by diffusion
– Gases will diffuse (move) across the cell
membrane from an area of high concentration
to an area of low concentration.
• Gas Exchange
• Gas exchange takes place in the alveoli.
LE 42-23
Branch
from
pulmonary
vein
(oxygen-rich
blood)
Branch
from
pulmonary
artery
(oxygen-poor
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Alveoli
Larynx
Left
lung
Esophagus
Trachea
Right
lung
Bronchus
Bronchiole
Capillary
Diaphragm
Heart
SEM
Colorized SEM
Gas Exchange inside a cell example
• Gas Exchange
O2
• Gas exchange
takes place in the
alveoli.
• Oxygen diffuses
into the blood.
Capillary
Gas Exchange inside a cell example
• Carbon dioxide in
the blood diffuses
into the alveolus.
O2
CO2
Capillary
Features of the Alveolus that make it great for gas
exchange
• Large total surface area – 700 million in our
lungs, providing 70m2 in total surface area. 30-40
times greater than the surface area of our skin
• Surface Area – greater the surface area
faster the rate of diffusion.
Features of the Alveolus that make it great for gas
exchange
• Walls of alveoli very thin, consisting of a single
layer of flattened cells,
• Thin walls decrease the length of the
diffusion path. The shorter the diffusion path
the greater the rate of diffusion
• Thus the respiratory path must be as thin as
possible.
• Walls of the alveoli have elastic properties
meaning they can stretch during inhalation and
then shrink back to their original size during
exhalation.
Features of the Alveolus that make it great for gas
exchange
• Surface of alveoli walls are covered with a film/
layer of moisture
• Oxygen gas dissolves in water lining of
alveoli. Oxygen diffuses into the blood when
it is dissolved in solution.
• Prevents the walls of the alveoli from sticking
together
• Surrounded by a dense network of capillaries.
Features of the Alveolus that make it great for gas
exchange
Alveoli is surrounded by a dense network of
capillaries.
• Network of capillaries around each
alveolus supplied deoxygenated
blood from pulmonary artery and
draining into pulmonary veins.
• This maintains the concentration
gradient of O2 and CO2.
Gas exchange occurs across capillaries,
whose walls are one cell thick
We have 50,000
miles of them
Few human cells are
> 100 μm from a
capillary
Red blood cells
Capillary wall
6.4.3 Describe the features of alveoli that adapt
them to gas exchange.(2)
• Large surface area due to the combined spherical
shape (600 million alveoli = 80 m2)
• Flattened epithelial cells of alveoli and close
association with capillaries
• Short diffusion distance from alveoli to blood (0.51.0 um)
• Dense capillary network
• Moist surface for the solution of gases
Gas exchange Animations
Ventilation
•
http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP15104
Gas exchange:
•
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter25/animation__gas_exchange_during_
respiration.html
Repiratory system tutorials
http://www.getbodysmart.com/ap/respiratorysystem/menu/menu.html
Lung Transplant Ted Talk
https://www.youtube.com/watch?v=T2EmuyHoMAI
Opera Sing with a lung transplant
https://www.youtube.com/watch?v=cvO9i0QkQbE
IB Learning Objective
• Explain the mechanism of ventilation of the lungs
in terms of volume and pressure changes caused
by the internal and external intercostal, muscles,
the diaphragm and abdominal muscles
Breathing ventilates the lungs
The process that ventilates the lungs is breathing,
the alternate inhalation and exhalation of air
LE 42-24
Rib cage
expands as
rib muscles
contract
Air
inhaled
Rib cage gets
smaller as
rib muscles
relax
Air
exhaled
Lung
Diaphragm
INHALATION
Diaphragm contracts
(moves down)
EXHALATION
Diaphragm relaxes
(moves up)
How a Mammal Breathes
• Mammals ventilate their lungs by negative
pressure breathing, which pulls air into the lungs
• The thorax is an air tight chamber, thus as
volume changes in the lungs, so does pressure.
– Boyles Gas Law = P1V1=P2V2
How a Mammal Breathes
Inhalation (inspiration) – Volume increases
•Lung volume increases as the:
–
External rib muscles (external intercostal
muscles) contract and cause the rib cage to
move up.
– and diaphragm contract (moves downs)
– Internal rib muscles (internal intercostal
muscles) relax.
How a Mammal Breathes
Inhalation (inspiration) – Volume increases
•Ribs will move upwards & outwards increasing
volume
•Diaphragm moves down increasing volume
•Increasing Volume, Lowers Pressure (Boyles
Law)
•Air moves from high pressure to low pressure.
Thus air will move from the atmosphere into the
lungs.
How a Mammal Breathes
Exhalation – Expiration – Decreasing Volume
Lung volume decrease as the
– Internal rib muscles ( internal intercostal
muscles) contract moving the rib cage up and
out
– and diaphragm relaxes (moves up)
– Internal rib muscles (external intercostal
muscles) relax.
• Decrease volume/ increases the pressure in the
lungs and air is forced out
How a Mammal Breathes
Exhalation – Expiration – Decreasing Volume
• The ribs move downwards and inwards, and the
diaphragm moves up.
• Volume is decrease
• Decreasing Volume, increasing Pressure (Boyles
Law)
• Air moves from high pressure to low pressure.
Thus, air from the lungs will be pushed towards
the atmosphere.
LE 42-24
Rib cage
expands as
rib muscles
contract
Air
inhaled
Rib cage gets
smaller as
rib muscles
relax
Air
exhaled
Lung
Diaphragm
INHALATION
Diaphragm contracts
(moves down)
EXHALATION
Diaphragm relaxes
(moves up)
The respiratory system
When the diaphragm contracts, the chest
cavity expands, and the lungs fill with air
Fig. 42.24