biology 2672a: comparative animal physiology breathing in air
TRANSCRIPT
Biology 2672a: Comparative Animal
Physiology
Breathing in air
Gas transport in organisms - a combination of convection and diffusion
Tidal convection ventilates lungs
Diffusion into bloodstream
Unidirectional flow (convection) in circulatory system
Diffusion from capillaries into tissues
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 AirLots of Oxygen!Not so easy to get
rid of CO2Problems with water
lossLungs
(invaginations)
(Most) Fishes Breathing Air
Electric Eel - Mouth
Plecostomus - Gut
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 systemVery 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 lungsTrachea
Bronchus
Terminal Bronchiole
Respiratory bronchiole
Alveolar ductAlveolar duct
Alveoli
Fig. 21.18
Breathing air while flyingEnergetic costs of flying are 2.5-
3 × higher than runningTwo groups of extant flying
vertebrates
Insects -Tracheal system reaches every cell
Ways to maximise O2 uptake
Countercurrent exchangeReduce diffusion distance Increase flow rate Increase absorption of O2
J=KP1-P2
X
Bird lungs – a one-way system
Fig. 22.24
The bird lung - orientation
Beak
Butt
Anterior Air Sacs
Posterior Air Sacs1° bronchus Mesobronchus
Parabro
nchiP
osterio
r 2°
bro
nch
us
An
teri
or
2°
bro
nch
us
Fig. 22.22
Bird lung: Breathe in
Bird lung: Breathe Out
See also Fig 22.22
Bird Lungs: Gas-bloodHighly efficient
>37 % of O2 extracted from the air Mammals: ~25%
Thin blood-gas barriersSurface area : body size ~ same
as mammalsSurface area : lung volume ~2×
mammals
Bird Lungs: Cross-current gas exchange
Fig. 22.23c Fig. 22.5
Ways to maximise O2 uptake
Countercurrent exchangeReduce diffusion distance Increase flow rate Increase absorption of O2
J=KP1-P2
X
Bat lungsMammalian – alveolar dead
space (etc)~Equivalent O2 uptake to birds Heart size, Heart output HaematocritLarge lungs
Surface area pulmonary blood volume thickness of blood-gas barrier
Bats vs birdsLargest 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…
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