Animal Gas Exchange and Transport Flashcards
Gas Exchange Basics
- eukaryotic cells continually produce CO2 as a waste product, and require O2 as the terminal e- acceptor in mito for cellular respiration
- multicellular eukaryotes use a system to exchange gases
- gas exchange during respiration occurs primarily through diffusion (from high to low concentrations)
Partial Pressure
a measure of the concentration of each individual component within the overall mixture of gases
- the TOTAL pressure exerted by the mixture is the sum of the individual pressures of the mixture components
PP: Rate of Diffusion
the rate of diffusion is proportional to its PP within the total gas mixture
- a gas with strong PP gradient (high PP on one side + low on the other) diffuses faster than a gas will low PP gradient
PP Formula
P = (Patm) x (% content in mixture)
- Patm is atmospheric pressure at given altitude
- Patm at sea level = 760 mm Hg
- as the altitude increases, the concentration of the gas does not change, but Patm decreases
- As a result, PP of each gas decreases as altitude increases
- these pressures determine gas exchange, or the flow of gas, in the system
Fick’s Law of Diffusion
Gasses move down their PP gradient; the rate of diffusion across a surface is controlled by:
- K (gas diffusion constant)
- A (area for gas exchange)
- P2-P1 (difference in PP of gas on either side of the diffusion barrier)
- D (the distance across which the gas must diffusion - thickness of the barrier)
Fick’s Law of Diffusion: FORMULA
( K X A X (P2-P1))/D
Best Conditions for Gas Diffusion
- the area available for gas exchange is large
- the PP difference is large
- the distance required for the gas to travel is small
Gas Exchange Evolution
optimized respiratory surfaces to have optimal gas diffusion conditions:
- respiratory surface maximizes SA to increase gas diffusion
- extremely thin, minimizing distance to cross
- capillaries bring blood to the surface for gas exchange; since the air in lungs has higher O2 than oxygen-depleted blood and low CO2, this concentration gradient allows for gas exchangw
Respiratory Surface Complex
gas exchange in complex organisms involve 3 steps
1. VENTILATION: air is brought into the organ
2. GAS EXCHANGE: O2 is taken in + CO2 is expelled
3. CIRCULATION: gas is moved to and from the tissues via a circulatory fluid
Respiratory Surface Variation
- Direct Diffusion
- Skin
- Trachea
- Gills
- Lungs
RS: Direct Diffusion
many organisms can diffuse across their outer membrane
- every body cell is close to the external environment
- cells are kept moist
- flat shape of organism increases SA for diffusion
- ensures every cell is close to the outer membrane and has access to O2
- EX: Cnidarians
RS: Skin
used as a respiratory organ in annelids and amphibians; use a sense network of capillaries below the skin to facilitate gas exchange between the external environment and circulatory system
- must be moist for gases to dissolve and diffuse across cell membranes
RS: Trachae
respiratory organs of insects, consisting of a network of small tubes that carries O2 to the entire body
- INDEPENDENT of the circulatory system; blood does not play a direct role in O2 transport
- gas passes directly to the needed tissues
- most direct repiratory system
some insects ventilate this system through body movements
Spiracles
opening in insect bodies that allow O2 to pass through the body + regulate diffusion of CO2 and H2O vapor
- air enters and leaves the tracheal system through these
RS: Gills
outgrowths of the body surface used for gas exchange + present in organisms that live in water (fish, mollusks, annelids, crustaceans)
- thin tissue filaments that are branched and folded
- water passes the gills + dissolved O2 enters into the bloodstream
- the CS can carry oxygenated blood to other body parts
- MOST EFFICIENT OF ALL RESPIRATORY SURFACES DUE TO COUNTERCURRENT EXCHANGE
Gills: Countercurrent Exchange
maximizes gas exchange across the length of the entire respiratory surface:
- because of the constant flow of gas across the gas-exchange membrane + constant PP difference, gills are the most efficient system in exchanging gases
RS: Lungs
infoldings of the throat/body surface used for gas exchange
- present in both vertebrates and invertebrates
Lungs: Amphibians
supplement gas exchange that occurs via the skin
- ventilated by POSITIVE PRESSURE, where air if forced into the lungs
- requires amphibians to gulp air into the mouth, close their mouth and nostrils, and raise the jaw to put air under high pressure and force it into a low pressure lung
Lungs: Birds
under NEGATIVE PRESSURE - a vacuum is created by the movement of muscles in the chest which pulls air into the lungs
- most efficient of vertebrate lung systems because of: unidirectional airflow + cross-current exchange
- allows birds to obtain enough O2 during flight
Bird Lungs: Unidirectional Airflow
accomplished by a series of air sacs that hold air first before and then after gas exchange occurs, so that exchange occurs both during inhalation + exhalation
Bird Lungs: Cross-Current Exchange
between airflow and the bloodstream of the respiratory surface
- helps maintain a CG for more efficient exchange
- not as efficient as CCE in gills
Lungs: Mammals
under NEGATIVE PRESSURE + are more efficient than amphibians but less than birds
- lack unidirectional airflow
- structure does not allow for a CC
- rely on a “web-like” flow that cannot maintain a CG
- contains “dead-space”
- gas exchange only occurs in small spaces called alveoli
Mammal Lungs: Dead Space
locations containing inhaled air that does not take part in gas exchange
Mammal Lungs: Alveoli
small sacs where a web-like arrangement of blood vessels come to close proximity to the inhaled air
- pathway to reach this includes the trachea, bronchi, and bronchioles, each part of the “dead space” of the lungs
