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Gas Exchange/Respiration
Gas Exchange
=Exchange CO2 for O2
=Need Respiratory Surface
– Needs to be thin for diffusion
– Needs to be moist for diffusion
– Needs to be in contact with gases
Gas Exchange/Protists
Respiratory surface is the cell membrane
What drives the diffusion?
Gas Exchange/Hydra
• Diffusion through cell membranes
(respiratory surface)
Gas Exchange/Worm
• Worms live in moist soil
• Oxygen from air goes into soil
• Thin, mucus-coated, skin is their respiratory surface (Gas
exchange across skin)
• If skin dries, they suffocate (Worms can also drown in waterLow O2 levels in water compared to air!)
Oxygen in Air
But how do the gases get
transported to the center of the
Need a transport system
• Need vessels
• Need blood with an oxygen-carrying
molecule, a respiratory pigment (ex.
• 100ml of water can carry 0.2ml of O2
• 100ml of blood can carry 20.0ml of O2
Gas Exchange/Grasshopper
5 pairs of
Allow O2 in
and CO2 out
Tracheal Tubes
Gas Exchange/Grasshopper
• Tracheal tubes branch through body
• They end with a moist, thin membrane that
butts up against body cells (respiratory
• Body movements allow for air to come in
and out of tracheal system
• No Hemoglobin in blood and blood not
used for gas transport
Gas Exchange/Aquatic
• Gills
– layers of tissue rich in blood
– Large surface area
– O2 gas is dissolved in H2O
– H20 with O2 gas washes over gills
– Exchange gases
– Need constant flow of water over gills or they
– Gills covered by operculum flap
Gas Exchange/Humans
• Respiratory Surface= Lungs
• Bronchi
part of
system but
not part of
• Inhaled (Breath In):
– 79% Nitrogen Gas
– 20.9% Oxygen
– 0.04% CO2
– water
• Exhaled (Breath out):
– 79% Nitrogen Gas
– 16.3% Oxygen (CPR)
– 4.5% CO2
– water
Route of Air
1. Nose (Nasal passages)
Hair for filtration
Mucus to moisten air
Blood vessels to warm air
Don’t get this with mouth
2. Pharynx
3. Larynx (Voice Box with
vocal cords made of
Tyler Vid
Route of Air
4. Trachea (Windpipe)
– Get open by rings of
– Lined with a ciliated
mucus membrane
– Coughing reflex
Tobacco smoke paralyzes cilia (1
cigarette=20min of paralysis)
Also increase mucus production
Route of air
5. Bronchi
– Ringed
– ciliated
Route of air
6. Bronchial Tubes
7. Bronchioles
– No rings
– Tiny tubes
– Open into the…
8. Alveoli
Lung Volume
• Tidal Volume=500ml of air in
and out during rest (3500mlexercise )
12 breaths/min(6L/min)Rest
40 breaths/min(42L/min)Exercise
• Functional Residual
Capacity=always left with
2300ml air after breathing out
Like cluster of grapes
300 million alveoli
70 sq meter surface area
Walls of air sacs are one cell thick
Site of gas exchange
• Emphysema
– Destruction of alveoli walls
– Scar tissue from macrophage attack
– Reduced breathing ability
• Asthma
– Allergic reaction in bronchioles with their subsequent closing
– Treat with Epinephrine mist
• Lung Cancer
• Pneumonia
– Fluid in alveoli
• Tuberculosis
– Immune attack leaves scars that thicken alveoli and affect
• Bronchitis
– Inflammation of bronchial tubes
Process of Inhalation (Active)
Rib muscles pull ribs up and out
Diaphragm muscle pulled down
Now low air pressure in chest
Air sucked into chest
Alveoli expand
Process of Exhalation (Passive)
Diaphragm relaxes and goes back up
Rib muscles relax
Ribs go down and in
Increase pressure in chest
Air squeezed out of lungs
Lung Model
Air pressure and altitude
• High altitudes have lower air pressure than
at sea level
• High altitudes have lower concentration of
O2 compared to sea level
Planes are pressurized and
pump oxygen into the plane
Air pressure and altitude
• What happens to our
blood when we go
suddenly from high
pressure to low
Nitrogen gas in blood bubbles
The “Bends”
The Bends
Mountains in
Have a high red blood cell count
More red bone marrow
More developed lungs
Breathing Regulation
• Involuntary
• Have Chemoreceptors in walls of arteries that
detect CO2 levels
• High CO2 levels in blood detected and send
message to respiratory center of brain (Medulla)
• Medulla send message to diaphragm and rib
muscles to increase rate and depth of breath
• Low pH of blood also stimulates medulla
External vs. Internal Respiration
• External
– Gas exchange in alveoli with capillaries
• Internal
– Gas exchange in capillaries with body cells
Oxygen transport
• In lungs oxygen combines with
Hemoglobin to form oxyhemoglobin
Oxygen Transport
• Oxygen released in locations of low O2
• Carbon monoxide has greater binding
ability to hemoglobin than oxygen
Carbon Dioxide Transport
• 70% as Bicarbonate in plasma
CO2 + H20
H++ HCO3-
Carbon Dioxide Transport
• 20% as carbaminohemoglobin
CO2 + Hb
(HbCO is carboxyhemoglobin)
Carbon Dioxide Transport
• 10% as free CO2 in plasma
Carbon Dioxide Transport
• Video 1
• video 2