Exchange Surfaces Flashcards
why do multicellular organisms require specialised gas exchange systems
small surface area:volume means distance that needs to be crossed is larger
substances cannot easily enter cells
name three features of an efficient gas exchange system
- large surface area:volume
- short diffusion distance
- good blood supply
describe the trachea and its function in the mammalian gas exchange system
wide tube supported by c shaped cartilage rings to stop it collapsing during pressure change
lined by ciliated epitheliul cells which move mucus towards throat to be swallowed preventing infection
describe the bronchi and function in mammalian gas exchange
supported by rings of cartilage and lined by ciliated epithelium cells and goblet cells
narrow and allow air into bronchioles
describe bronchioles and function in mammalian gas exchange
mostly only smooth muscle and elastic fibres so that they can contract and relax easily during ventilation
describe alveoli and function in mammalian gas exchange
mini air sacs lined with epithelium cells
walls only one cell thick covered with network of capillaries
site of gas exchange
explain process of inspiration
external intercostal muscles relax
ribs pulled up and out
diaphragm contracts and flattens
volume of thorax increases
air pressure outside lungs is higher than inside so air moves in
explain the process of expiration
external intercostal muscles contract
ribs move down and in
diaphragm relaxes and domes
volume of thorax decreases
air pressure outside lungs is lower than inside so air moves out
explain how a spirometer works
used to measure lung volume
breathe into air tight chamber which leaves trace on graph showing volume of breaths
define vital capacity
maximum volume of air that can be inspired or expired in one breath
define tidal volume
amount breathed in and out in one normal breath
define breathing rate
number of breaths per minute
describe two main features of a fish gas exchange system
gills
supported by arches with multiple projections of gill filaments stacked up in piles
lamellae
right angles to gill filaments giving increased surface area
blood and water flow across them in opposite directions
explain the process of gas exchange in fish
buccal cavity volume increases to enable water to flow in
water pumped over lamellae by operculum and oxygen diffuses into blood
waste CO2 diffuses into water and flows back out gills
how does counter current system maximise oxygen absorbed
maintains a steep concentration gradient as water is always next to blood of lower oxygen concentration keeps rate of diffusion constant
describe three main features of insect’s gas exchange system
spiracles
holes on surface body opened or closed by valve for exchange
tracheae
large tubes extending through body tissues
supported by rings to stop collapsing tracheoles
smaller branches dividing off trachea
explain process of gas exchange in insects
gases move in and out of tracheae through spiracles
diffusion gradient allows oxygen to diffuse into body tissue while CO2 diffuses out
contraction of muscle in thorax allows movement of air in and out
compare and contrast mechanisms of expiration for normal and forced expiration
normal
-passive
-disaphragm relaxes and domes
-external intercostals relax
-ribs move down and in
-volume of thorax reduced causing pressure to increase
-pressure in thorax greater so air moves out
forced
-active so requires energy
-external intercostal muscles relax
-ribs pulled down hard
-abdominal muscles contract forcing diaphragm up
outline how repiratory systems in fish and insects are adapted to maximise ventilation and gas exchange
insect gas exchange
-series of branched tracheoles increase surface area
-has short diffusion distance
insect ventilation
-large SA:V so sufficient diffusion
-size of spiracles controlled
fish ventilation
-water enters mouth which changes volume/pressure
-water pushed out gills
fish gas exchange
-large number of gill filaments increasing surface area
-lots of capillaries so good supply
-tips of gill filaments overlap to slow down water movement
describe how trachea of mammal different to insect
mammals only have one
mammal trachea has cartilage but insects have chitin
-mammal trachea has smooth muscle and goblet cells
how are gills adapted for efficient gas exchange
many filaments create large SA
central blood vessel provides good blood supply which maintains steep concentration gradient
secondary lamellae provide large surface area
-short diffusion distance between blood and water
