Respiration & Gas Exchange
SBI 3U
In memory of William: d.o.d 4.1.08
The needs of All Organisms
• To obtain
oxygen for
cellular
respiration
• To get rid of
carbon dioxide
from cellular
respiration
http://www.lima.ohio-state.edu/academics/biology/images/amoeba.jpg
Single celled organisms
• Usually live in
water (aquatic)
• Are very small
• Have large
surface area
relative to their
volume
• transport O2 and
CO2 by diffusion.
http://www.planet-pets.com/amoeba1.jpg
What about Multi-cellular organisms?
• Still need oxygen
• Still need to remove carbon dioxide
• Need to develop specialized structures
to carry out the process of gas
exchange.
• Sponges and jellyfish use diffusion to exchange
gases from the surrounding water. Flatworms
and worms use their outer surfaces as gas
exchange surfaces.
Insects , worms, and fish use gills; land
vertebrates use internal lungs.
Gas exchange takes place
• At a respiratory surface such as:
•Cell membrane
•Skin surface
•Trachea
•Gills
•lungs
Organisms without respiratory systems
need to be.
• Small
• Flattened
• Tubular
• Aquatic
All respiratory surfaces need to be..
•
•
•
•
Large
Thin
Moist
Well supplied with blood
Gas Exchange in Fish
Gas exchange in Insects
Human Respiratory System
Terminology
•
•
•
•
•
•
•
•
Lungs
Larynx (voice box)
Trachea (windpipe)
Bronchi (sing. Bronchus)
Nose
Epiglottis
Bronchioles
Alveoli (air sacs)
Terminology continued
•
•
•
•
•
•
•
•
•
Ribs
Diaphragm
Intercostal Muscles
Pleural membranes
Thorax (chest)
Inhalation
Exhalation
Ventilation
Lung capacity
http://www.rsdrx.com/images/RespiratorySystemLRes.gif
Nasal cavity
Pharynx
Larynx (voice-box)
Trachea - windpipe
Bronchus (pl bronchi)
Pleural membrane around lung
Bronchiole
Alveoli
Diaphragm
How do gases travel in the blood?
• Some CO2 in the blood is carried bound
to hemoglobin or dissolved in plasma.
Most CO2 is transported as bicarbonate
ion, generated from carbonic acid that
forms when CO2 reacts with water and
ionizes. The Enzyme Carbonic
anhydrase speeds this reaction. The
process reverses in the lungs, releasing
CO2 for expiration.
What happens during breathing?
• Air enters the nose
• Air is warmed, moistened and filtered
• Air passes behind the pharynx over the
voice box
• The epiglottis (a flap of skin) stops the
food going down the trachea when
swallowing
• Air passes down the trachea and
branches to the two bronchi.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookRESPSYS.html
A. Inhalation The intercostal
B. Exhalation The intercostal
muscles contract, lifting
the rib cage up and out. At the
same time, the
diaphragm contracts and pulls
downward. As the
lungs expand, air moves in.
muscles relax, allowing
the rib cage to return to its
normal position. The
diaphragm also moves upward,
resuming its domed
shape. As the lungs contract, air
moves out.
• The trachea and bronchi are kept
open by rings of cartilage.
• The lining of the trachea and
bronchi are covered with cilia
which continually move dirt and
mucus upwards towards the nose
and mouth
• The bronchi divide like the
braches of a tree getting smaller
and smaller
• The bronchioles finally end in
small single celled sacs called
alveoli (air sacs)
• Gas exchange takes place in the
alveoli
http://webanatomy.net/histology/respiratory/alveoli.jpg
In the Alveoli
http://www.dannynicholson.co.uk/learningzone/body/organs/Alveoli.jpg
CO2
Capillary
cell
Plasma
O2
Alveoli
Red blood
cell
Moisture
Exchange of Gases:
Composition of inhaled and exhaled air –
Gas %
Inhaled Air
Exhaled air
Oxygen
20%
16%
Carbon
dioxide
0.04%
4.0%
Nitrogen
79%
79%
Water
Vapour
Varies
Saturated
Regulation of Breathing Movement
When a child, in a temper tantrum,
holds his or her breath, the medulla oblongata in the brain
eventually takes over the control of breathing and the child is
forced to breathe. Breathing is an involuntary activity. It is
controlled by a negative feedback loop that keeps the oxygen
and carbon dioxide concentration in the blood relatively
constant Oxygen is vital to all parts of the body, but the brain is
especially sensitive to a low level of oxygen. If the brain is
deprived of oxygen for more than four minutes, irreversible
brain damage occurs. Possibly for this reason, the medulla
oblongata controls vital mechanisms like breathing and heart
rate.
The mechanism of breathing is coordinated by chemoreceptors
that detect changes in the pH of the blood. These special receptors
are sensitive to the levels of gases in the blood, especially the
level of carbon dioxide.
Levels of CO2 in the blood regulate breathing in the
Medulla Oblongata
Problems of the Respiratory System
Normal Lungs & Heart
Fluid in the Lungs
Cancer in the left lung
Lung Cancer
Cystic Fibrosis