1. Happy Thursday! 2/24/11
Explain the need for, and the mechanism of, ventilation of the lungs in humans. (Total 8 marks)

2. 8 max (Plus up to [2] for quality)
Need:
draws fresh air / oxygen into the lungs;
removal / excretion of CO2;
maintains concentration gradient of O2 / CO2 / respiratory gases;
Mechanism:
diaphragm contracts;
(external) intercostal muscles contract;
increased volume (of thorax / thoracic cavity);
decreasing air pressure in lungs;
air rushes in down air pressure gradient;
converse of the above causes exhalation;
abdominal muscles contract during active exhalation;
elastic recoil of lungs helps exhalation;

3. Chapter 22
Gas Exchange

4. Surviving in Thin Air Himalayas Have claimed many lives
Air at height of world’s highest peak, Mt. Everest
Is so low in O2 : most people would pass out instantly if exposed to it!

5. Twice a year, flocks of geese migrate over Himalayas
able to fly at such high altitude b/c lung efficiency
have hemoglobin w/very high affinity for oxygen
(Adaptation) carry lg amts oxygen to tissues, to exchange with carbon dioxide

6. The process of gas exchange, often called respiration
interchange of O2 and CO2 between an organism and its environment

7. MECHANISMS OF GAS EXCHANGE
22.1 Overview: Gas exchange involves breathing, transport of gases, and exchange of gases with tissue cells 1
Breathing O2
CO2
Lung
Circulatory
system 2
Transport
of gases by
the circulatory
system
Mitochondria 3
Exchange
of gases
with
body
cells O2
CO2
Capillary
Figure 22.1
Cell

8. Gas exchange
Provides O2 for cellular respiration and
removes its waste product, CO2

9. 22.5 Terrestrial vertebrates have lungs
22.5 Terrestrial vertebrates have lungs
In mammals, air inhaled through the nostrils
Passes through the pharynx and larynx into the trachea, bronchi, and bronchioles
Air tube?
Smaller?
& Smaller?
(Heart)
Diaphragm
Bronchiole
Bronchus
Right lung
Trachea
Larynx
(Esophagus)
Pharynx
Nasal
cavity
Left lung
Figure 22.5A

11. bronchioles end in clusters of tiny sacs called alveoli
Online Review Activity: Labeling Parts
bronchioles end in clusters of tiny sacs called alveoli
Where gas exchange occurs
Process?
Colorized SEM 6,200
Oxygen-rich
blood
Bronchiole
Oxygen-poor
Alveoli
Blood
capillaries
Figure 22.5B, C

13. 22.6 Smoking is a deadly assault on our respiratory system
CONNECTION
22.6 Smoking is a deadly assault on our respiratory system
Mucus and cilia in the respiratory passages
Protect the lungs
Can be destroyed by smoking
Structures, features?

14. Causes lung cancer, heart disease, and emphysema
Smoking
Causes lung cancer, heart disease, and emphysema
Lung
Heart
Figure 22.6

15. 22.7 Breathing ventilates the lungs
22.7 Breathing ventilates the lungs
alternation of inhalation and exhalation

16. The contraction of rib muscles and the diaphragm
Expands chest cavity, reduces air pressure in alveoli (negative pressure breathing)
Names of muscles?
Air
inhaled
Air
exhaled
Rib cage
expands as
rib muscles
contract
Rib cage gets
smaller as
rib muscles
relax
Lung
Diaphragm
Diaphragm relaxes
(moves up)
Diaphragm contracts
(moves down)
Inhalation
Figure 22.7A
Exhalation

17. Vital capacity is the maximum volume of air we can inhale and exhale
Vital capacity is the maximum volume of air we can inhale and exhale
But our lungs still hold a residual volume
Who read last night?

18. Air sacs empty; lungs fill
Air flows in one direction
Through the more efficient lungs of birds!
Air
Anterior
air sacs
Posterior
Trachea
Lungs
tubes
in lung
1 mm
Exhalation:
Air sacs empty; lungs fill
Inhalation:
Air sacs fill
Figure 22.7B

19. 22.9 Breathing is automatically controlled
22.9 Breathing is automatically controlled
Breathing control centers in the brain
Keep breathing in tune with body needs, sensing and responding to the CO2 level in the blood
What gas? Where?
Brain
Cerebrospinal
fluid
Pons
Medulla
Nerve signals
trigger
contraction
of muscles
Breathing
control
centers
stimulated by:
CO2 increase /
pH decrease
in blood
indicating CO2
and O2 levels
CO2 and O2
sensors in
aorta
Diaphragm
Rib muscles
Figure 22.8

20. A drop in blood pH
Triggers an increase in rate & depth of breathing

21. TRANSPORT OF GASES IN THE BODY
22.9 Blood transports respiratory gases
heart pumps O2 - poor blood to lungs
picks up O2 , drops off CO2
heart pumps O2 - rich blood to body cells
drops off O2 , picks up CO2
Where?
Where?

22. Gas transport and exchange in the body
Exhaled air
Inhaled air
Air spaces
Alveolar
epithelial
cells
CO2 O2
CO2-rich,
O2-poor
blood
O2-rich,
CO2-poor
Heart
Tissue
capillaries
Interstitial
fluid
Tissue cells
throughout body
capillaries of lung
Figure 22.9

23. Gases diffuse down partial-pressure gradients
In the lungs and the tissues
Online Animation of Gas Exchange

24. 22.10 Hemoglobin carries O2 and helps transport CO2 and buffer the blood
Hemoglobin in red blood cells
Transports oxygen, helps buffer the blood and carries some CO2
Molecule?
Molecule?
Iron atom
Heme group
O2 loaded
in lungs
O2 unloaded
in tissues
Polypeptide chain
Figure 22.10

25. transported as bicarbonate ions in plasma
Most CO2 in blood
transported as bicarbonate ions in plasma
CO2 +
H2O
H2CO3 H+
HCO3–
Carbon
dioxide
Water
Carbonic
acid
Hydrogen
ions
Bicarbonate

26. CONNECTION
22.11 The human fetus exchanges gases with the mother’s bloodstream
In the
placenta
Placenta, containing
maternal blood vessels
and fetal capillaries
Umbilical cord,
containing fetal
blood vessels
Amniotic
fluid
Uterus
Figure 22.11

27. Fetal hemoglobin
Enhances oxygen transfer from maternal blood
At birth, increased CO2 in fetal blood
Stimulates breathing control centers to initiate breathing

28. To be continued...(Reproduction Unit!)

29. 22.2 Animals exchange O2 and CO2 across moist body surfaces
22.2 Animals exchange O2 and CO2 across moist body surfaces
Respiratory surfaces
Must be thin and moist for diffusion of O2 and CO2 to occur

30. Some animals, like the earthworm
Some animals, like the earthworm
Use their entire skin as a gas-exchange organ
Cut
Cross section
of respiratory
surface (the
skin covering
the body)
CO2
Capillaries O2
Figure 22.2A

31. In most animals
Specialized body parts provide large respiratory surfaces for gas exchange
Body surface
Respiratory
surface
(air tubes)
Body cells
(no capillaries) O2
CO2
Body surface
Respiratory
surface
(gill)
Capillary
CO2 O2
Figure 22.2C
Body surface
Respiratory
surface
(within lung)
Capillary
CO2 O2
Figure 22.2B
Figure 22.2D

32. 22.3 Gills are adapted for gas exchange in aquatic environments
22.3 Gills are adapted for gas exchange in aquatic environments
Gills are extensions of the body
That absorb O2 dissolved in water

33. In a fish, gas exchange
Is enhanced by ventilation and the countercurrent flow of water and blood
Gill arch
Direction
of water flow
Blood
vessels
Gill
filaments
Oxygen-rich
blood
Oxygen-poor
Lamella
15%
40%
70%
100%
60%
80%
30% 5%
% O2 in water
flowing over
lamellae
% O2 in blood
flowing through capillaries
in lamellae
Countercurrent exchange
Figure 22.3

34. 22.4 The tracheal system of insects provides direct exchange between the air and body cells
Land animals
Exchange gases by breathing air

35. Tracheal systems in insects
Tracheal systems in insects
Transport O2 directly to body cells through a network of finely branched tubes
Air sacs
Tracheae
Opening
for air
LM 250
Body
cell
Tracheole
Air
sac
Trachea
Body wall
CO2 O2
Figure 22.4A, B