Transcript Biology 272b: Comparative Animal Physiology

Biology 2672a:
Comparative Animal
Physiology
Breathing in air
Gas transport in organisms - a
combination of convection and diffusion
Tidal convection
ventilates lungs
Unidirectional
flow (convection)
in circulatory
system
Diffusion
from
capillaries
into tissues
Diffusion into
bloodstream
Concurrent gas exchange
Fig. 21.4a
Countercurrent gas exchange
Concurrent
Fig 21.4b
Countercurrent gas exchange
Concurrent
Fig 21.4b
Cross-current gas exchange
Fig. 21.5
Mammal lungs are inefficient
Fig. 21.19
Fig. 21.3
Breathing Air
 Lots
of Oxygen!
 Not so easy to get rid
of CO2
 Problems with water
loss
 Lungs
(invaginations)
(Most) Fishes Breathing Air
Plecostomus - Gut
Electric Eel - Mouth
Bowfin – Swim bladder
Fig. 23.15
Tracheal system
Fig. 22.29
Construction of the tracheal
system
A branched series of tubes that are
filled with air (except at the very
ends)
 Trachea>Tracheoles
 Terminal tracheoles




Constructed from a single invaginated cell
Distance between lumen & cell = 3 x cell
membranes
Fluid-filled
Tracheal system
 Very
extensive
no cell is more than 2-3 cell
diameters from a tracheole
 Tissues with high metabolism (e.g.
flight muscle) may have at least
one terminal tracheole penetrating
each cell (!)
 On-tap oxygen in every cell!

Gas transport in the tracheal
system
Diffusion works very
well in gases
 Some convection




Thorax & abdomen pumping
Caused by partial pressure gradients?
Tracheal pumping? (see movie on WebCT)
One-way flow systems
 ‘Ram’ ventilation (draft ventilation)

Mammal lungs
Trachea
Bronchus
Alveoli
Alveolar duct
Terminal Bronchiole
Respiratory bronchiole
Fig. 21.18
Breathing air while flying
 Energetic
costs of flying are 2.53 × higher than running
 Two groups of extant flying
vertebrates
Insects -Tracheal system
reaches every cell
Ways to maximise O2 uptake
 Countercurrent
exchange
 Reduce diffusion distance
 Increase flow rate
 Increase absorption of O2
J=K
P1-P2
X
Bird lungs
– a one-way system
Fig. 22.24
The bird lung - orientation
Anterior
Air Sacs
Beak
1° bronchus
Mesobronchus
Posterior
Air Sacs
Butt
Fig. 22.22
Bird lung: Breathe in
Bird lung: Breathe Out
See also Fig 22.22
Bird Lungs: Gas-blood
 Highly

efficient
>37 % of O2 extracted from the air

Mammals: ~25%
 Thin
blood-gas barriers
 Surface area : body size ~ same
as mammals
 Surface area : lung volume ~2×
mammals
Bird Lungs: Cross-current gas
exchange
Fig. 22.23c
Fig. 22.5
Ways to maximise O2 uptake
 Countercurrent
exchange
 Reduce diffusion distance
 Increase flow rate
 Increase absorption of O2
J=K
P1-P2
X
Bat lungs
 Mammalian
– alveolar dead
space (etc)
 ~Equivalent O2 uptake to birds
 Heart size, Heart output
  Haematocrit
 Large lungs
Surface area
 pulmonary blood volume
 thickness of blood-gas barrier

Bats vs birds
 Largest
birds (~18 kg) much
larger than largest bats (~1.5
kg)
 Birds function perfectly well
(fly!) at high altitude
Geese over Mt Everest
 Vulture in jet engine at 11.2 km
 High altitude climbers not plagued
with bats…

Reading for Thursday
 Blood
 Pp581-603