1) Gas exchange occurs through respiratory surfaces where oxygen and carbon dioxide diffuse across thin membranes. Various organisms use different respiratory surfaces like cell membranes in protists, skin in worms, tracheal tubes in insects, gills in aquatic animals, and lungs in humans. 2) In humans, air moves from the nose through the trachea and bronchi to the bronchioles and alveoli in the lungs where oxygen and carbon dioxide diffuse between the alveolar air and blood in capillaries. 3) Oxygen is transported in the blood bound to hemoglobin while carbon dioxide is transported as bicarbonate, carbaminohemoglobin, and dissolved gas, and both gases are exchanged between blood and

1. Gas Exchange/Respiration

2. 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

3. Gas Exchange/Protists
CO2
O2
Respiratory surface is the cell membrane
What drives the diffusion?

4. Gas Exchange/Hydra
• Diffusion through cell membranes
(respiratory surface)
O2
CO2

5. 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 water-
Low O2 levels in water compared to air!)
Oxygen in Air CO2
CO2

6. But how do the gases get
transported to the center of the
worm?

7. Need a transport system
• Need vessels
• Need blood with an oxygen-carrying
molecule, a respiratory pigment (ex.
Hemoglobin)
• 100ml of water can carry 0.2ml of O2
• 100ml of blood can carry 20.0ml of O2

8. Gas Exchange/Grasshopper
Spiracles=
5 pairs of
openings
Allow O2 in
and CO2 out

9. Spiracle
opening
Tracheal Tubes

10. Gas Exchange/Grasshopper
• Tracheal tubes branch through body
• They end with a moist, thin membrane that
butts up against body cells (respiratory
surface)
• Body movements allow for air to come in
and out of tracheal system
• No Hemoglobin in blood and blood not
used for gas transport

11. 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
suffocate
– Gills covered by operculum flap

13. Gas Exchange/Humans
• Respiratory Surface= Lungs

14. Lungs
• Bronchi
part of
respiratory
system but
not part of
lung

15. Air
• 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

16. 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
breathing
2. Pharynx
3. Larynx (Voice Box with
vocal cords made of
cartilage)
Tyler Vid

17. Route of Air
4. Trachea (Windpipe)
– Get open by rings of
cartilage
– Lined with a ciliated
mucus membrane
– Coughing reflex
Tobacco smoke paralyzes cilia (1
cigarette=20min of paralysis)
Also increase mucus production

18. Route of air
5. Bronchi
– Ringed
– 2
– ciliated

19. Route of air
6. Bronchial Tubes
7. Bronchioles
– No rings
– Tiny tubes
– Open into the…
8. Alveoli

20. Lung Volume
• Tidal Volume=500ml of air in
and out during rest (3500ml-
exercise )
12 breaths/min(6L/min)Rest
40 breaths/min(42L/min)Exercise
• Functional Residual
Capacity=always left with
2300ml air after breathing out

21. Alveoli
Like cluster of grapes
300 million alveoli
70 sq meter surface area
Walls of air sacs are one cell thick
Site of gas exchange

22. Problems
• 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
diffusion
• Bronchitis
– Inflammation of bronchial tubes

23. Process of Inhalation (Active)
1. Rib muscles pull ribs up and out
2. Diaphragm muscle pulled down
3. Now low air pressure in chest
4. Air sucked into chest
5. Alveoli expand

24. 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

26. Lung Model

27. 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

28. Planes are pressurized and
pump oxygen into the plane

29. Air pressure and altitude
• What happens to our
blood when we go
suddenly from high
pressure to low
pressure
environments?

30. Nitrogen gas in blood bubbles
out
The “Bends”

31. The Bends

32. Andes Mountains in Peru
Have a high red blood cell count
More red bone marrow
More developed lungs

33. 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

34. External vs. Internal Respiration
• External
– Gas exchange in alveoli with capillaries
• Internal
– Gas exchange in capillaries with body cells

35. Oxygen transport
• In lungs oxygen combines with
Hemoglobin to form oxyhemoglobin

36. Oxygen Transport
• Oxygen released in locations of low O2
concentration
• Carbon monoxide has greater binding
ability to hemoglobin than oxygen

37. Carbon Dioxide Transport
• 70% as Bicarbonate in plasma
CO2 + H20 H2CO3 H++ HCO3
-

38. Carbon Dioxide Transport
• 20% as carbaminohemoglobin
CO2 + Hb HbCO2
(HbCO is carboxyhemoglobin)

39. Carbon Dioxide Transport
• 10% as free CO2 in plasma

40. Carbon Dioxide Transport

41. • Video 1
• video 2