exchange Flashcards
define an exchange surface
a specialised area which is adapted to make gas exchange more efficient
which type of organisms complete gas exchange by diffusion
single celled
how can single-celled organisms use diffusion for gas exchange
they have a very high surface area to volume ratio
why do larger organisms need specialised systems for gas exchnage
because they do not have a high enough surface area to volume ratio to meet the needs of their metabolic rate
volume of a cuboid=
length x width x height
sa of a cuboid=
(4 x length x height) + (2 x height x width)
volume of a cylinder=
πr^2 x height
sa of a cylinder=
(2πr x height) + 2πr^2
volume of a sphere=
4/3πr^3
sa of a sphere=
4πr^2
3 features of a good exchange surface are…
- high sa to volume ratio
- thin walls
- maintain steep concentration gradient
what practical is relevant to exchange surfaces
the agar cube practical
describe the agar cube practical
- pink phenolphthalein dye placed into agar cubes
- agar cubes of varying sizes placed into hydrochloric acid
- pink phenolphthalein turns from pink to colourless in hydrochloric acid
- demonstrates how sa to volume ratio affects rate of diffusion
Fick’s law describes
rate of diffusion
Fick’s law: rate of diffusion=
surface area x concentration / diffusion distance
the 6 levels of the human airway are…
1→ trachea 2→ bronchus 3→ bronchioles 4→ alveolar duct 5→ alveolar sac 6→ alveoli
what is the 1st level of the human airway
trachea
what is the 2nd level of the human airway
bronchus
what is the 3rd level of the human airway
bronchioles
what is the 4th level of the human airway
alveolar duct
what is the 5th level of the human airway
alveolar sac
what is the 6th level of the human airway
alveoli
how many adaptations do alveoli have
5
what are the 5 adaptations of alveoli
1- contain macrophages
2- elastic fibres and collagen with fibroblast cells
3- dense surrounding network of capillaries
4- type 1 epithelial cells make up alveolar wall
5- type 2 epithelial cells secrete surfactant
why do alveoli contain macrophages
to engulf and digest pathogens which have been breathed in and reached the alveoli
which alveoli contain macrophages
large
why do alveoli have elastic fibres and collagen with fibroblast cells
allowing for stretch and recoil in the alveoli to accommodate inhaled air and to expel air
why do alveoli have a dense surrounding network of capillaries
increases the surface area for gas exchange
why are alveolar walls made up of type 1 epithelial cells
they are very thin, so to reduce the distance for gas to exchange over (0.6 micrometers)
why do alveoli have type 2 epithelial cells
to release surfactant, which reduces the surface tension preventing alveoli from collapsing, kills bacteria and speeds up exchange of gases
what is surfactant
a mixture of lipids and proteins
what can surfactant do
reduce surface tension in alveoli, kill bacteria and speed up gas exchange
the trachea function is
a tube for inspired air to travel down
what are the 3 tracheal adaptations
1- c shaped ring of cartilage
2- contains goblet cells
3- contains ciliated epithelium
why does the trachea have a c shaped ring of cartilage
to keep the trachea always open so air can always be inspired
why is the cartilage in the trachea c shaped
so that food can travel down the adjacent oesophagus
why does the trachea have goblet cells
to trap any foreign particles inspired, which could damage delicate alveoli later on
how do goblet cells work
they use sticky mucus to trap particles
why does the trachea have ciliated epithelium
to waft mucus from the goblet cells up into the mouth to be swallowed and broken down
bronchus function
a tube which carries area from the trachea to the smaller bronchioles
bronchus adaptation
a full ring of cartilage
why does the bronchus have a ring of cartilage
to ensure that the tube always stays open so air can reach the lungs
how come the bronchus can have a full ring of cartilage
it doesn’t have to accommodate for the oesophagus
does the bronchus have a smaller or wider diameter than the trachea
smaller
does the trachea have a thinner or thicker diameter than the bronchus
thicker
2 adaptations of bronchioles are
- large bronchioles have goblet cells
2. contain elastic fibres and smooth muscle
why do bronchioles not need a cartilage ring
they are narrow enough to support themselves
why do large bronchioles have goblet cells
to trap foreign particles with sticky mucus
why do smaller bronchioles not have goblet cells
there has been plenty of opportunity already to trap foreign particles
why do bronchioles contain elastic fibres and smooth muscle
to adjust the diameter of airways to increase or decrease airflow as needed
for gas exchange in the alveoli, we must
maintain a steep concentration gradient
co2 concentration must be - in the blood
higher
oxygen concentration must be - in the blood
lower
how do we maintain steep concentration gradients?
by breathing to constantly refresh the blood supply in the alveoli
during inspiration, internal intercostal muscles -
relax
during inspiration, external intercostal muscles
contract
during inspiration, the movement of muscles causes the ribs to move
upwards and outwards
during inspiration, the diaphragm
contracts and moves downwards
during inspiration, the volume of the thorax
increases
during inspiration, the pressure in the thorax
decreases
during inspiration, decreased thoracic pressure causes air
to enter the lungs
inspiration is - process
an active
during expiration, internal intercostal muscles
relax
during expiration, external intercostal muscles
relax
during expiration, ribs move
inwards and down
during expiration, the diaphragm
relaxes and returns to a dome shape
during expiration, the volume of the thorax
decreases
during expiration, the pressure in the thorax
increases
during expiration, increased thoracic pressure causes air
to move out of the lungs
expiration is - process
a passive
during forced expiration, external intercostal muscles
relax
during forced expiration, internal intercostal muscles
contract
during forced expiration, ribs move
even further inwards
during forced expiration, the diaphragm
moves further upwards into a dome shape
during forced expiration, the diaphragm moves with the aid of
abdominal muscles
during forced expiration, the volume of the thorax
decreases further
during forced expiration, the pressure in the thorax
further increases
during forced expiration, the pressure in the thorax causes
even more air to exit the lungs
forced expiration is - process
an active
a spirometer is a device used to
measure and record the volumes of air inspired and expired over time
what records the volume of a spirometer
a kymograph
what is the kymograph
a piece of paper that records volume on a spirometer
what 5 precautions are needed with spirometers?
- healthy subject
- soda lime to absorb co2
- subject wears a nose peg
- sterile mouthpiece
- water chamber not over filled
what absorbs co2 in a spirometer
soda-lime
when inspiring, the trace goes
down
when expiring, the trace goes
up
the peak of expiration to the low of inspiration shows us
the volume of the patient’s single breath
what shows us the volume of the patient’s single breath
the peak of expiration to the low of inspiration
tidal volume (TV)-
the volume of air breathed in and out in one breath at rest
tidal volume (TV) is usually around
500cm3
expiratory reserve volume (ERV)-
the maximum volume of air that can be forced out after a normal tidal expiration
the maximum volume of air that can be forced out after a normal tidal expiration is the
expiratory reserve volume (ERV)
inspiratory reserve volume (IRV)-
the maximum volume of air that can be inspired over and above a tidal respiration
the maximum volume of air that can be inspired over and above a tidal respiration is the
inspiratory reserve volume (IRV)
residual volume (RV)-
the volume of air left in the lungs after breathing out as far as possible
why do we have residual volume in the lungs?
due to surfactants, and to keep the alveoli partly inflated so that gas exchange can still occur between breaths
vital capacity (VC)-
the greatest volume of air you can move into and out of your lungs in one breath
how do we calculate vital capacity (VC)
IRV+ TV + ERV
inspiratory reserve volume + tidal volume + expiratory reserve volume
total lung capacity-
the total amount of air in the lungs at any time
how do we calculate total lung capacity?
vital capacity + reserve volume
pulmonary ventilation rate is a measure of
the volume of air moved into the lungs in one minute
how do we calculate pulmonary ventilation rate?
tidal volume x breathing rate
how do we find the breathing rate?
count how many breaths per minute
insects have an endo/ exoskeleton
exoskeleton
can gases diffuse through the exoskeleton
no
insects have hemolymph, so they don’t have - to carry oxygen
blood pigments
in insects, air enters through
spiracles
spiracles are
small openings on insects
the problem with spiracles is that they
lose water
to reduce water loss, spiracles have
sphincters
sphincters allow insects to
open and close spiracles
why are sphincters needed
to reduce water loss while allowing air to enter insects
what leads away from spiracles
tracheae
tracheae diameter?
1mm
tracheae are lined by
chitin
why do tracheae have chitin?
to keep the tubes always open so air can always move through the insect
chitin is - to gas
impermeable
because chitin is impermeable to gas,
no gas exchange occurs in the tracheae of insects
trachea branch into
tracheoles
tracheoles diameter?
0.6 micrometres
in insects, where does gas exchange occur?
tracheoles
tracheoles run
between cells
tracheoles are spread
throughout tissue in insects
3 tracheoles adaptations:
- small and vast numbers
- moisture along the systems
- tracheal fluid
why is it good that tracheoles are small and vast numbers
high sa to volume ratio
why is it good that tracheoles have moisture along the systems
allows oxygen to dissolve and then diffuse into surrounding cells
why is it good that tracheoles have tracheal fluid
allows lactic acid to diffuse out during anaerobic respiration, exposing a greater surface area for gas exchange when needed
all oxygen needed by the insect’s cells is provided by
the tracheal system
some insects, such as - have higher energy demands
grasshoppers, bees
some larger insects have more
specialised ventilation systems
large insects have 2 extra systems…
- abdominal movement
2. collapsible tracheae and air sacs
why do large insects have abdominal movement
to change internal pressure, causing air to be drawn into or pushed out of the tracheal system
why do large insects have collapsible tracheae and air sacs
to can provide a reserve of air for the insect
what difficulties do fish have to overcome
water is far denser and more viscous than air
what is the organ of gas exchange in fish
gills
3 gill adaptations:
- large surface area
- good blood supply
- thin layers
an operculum is
a bony flap
2 functions of operculum are
protects the gills and maintains water flow over the gills
to maintain flow of water over the gills, the mouth
opens
to maintain flow of water over the gills, the buccal cavity floor
is lowered
to maintain flow of water over the gills, buccal cavity volume
increases
to maintain flow of water over the gills, buccal cavity pressure
decreases
as pressure in the buccal cavity decreases,
water rushes into the buccal cavity
after water flows into the buccal cavity, the opercular valve
shuts
after the opercular valve shuts,
the opercular cavity expands
when the opercular cavity expands, the pressure
decreases
after the opercular cavity expands, the buccal cavity floor -, and the volume -, so the pressure -
moves upwards , decreases, increases
as a result of the buccal cavity pressure increasing and opercular cavity pressure decreasing, water
rushes over the gills into the opercular cavity
3 fish gas exchange specializations
1- mouth opening system
2- gill filaments overlap
3- countercurrent flow
the steps of mouth opening. system are
→ the mouth opens, and the buccal cavity floor is lowered
→ volume of the buccal cavity is increased
→ pressure in the buccal cavity decreases, so water moves in
→ the opercular valve shuts and the opercular cavity expand
→ the opercular cavity pressure decreases
→ the buccal cavity floor moves up, increasing the pressure in the buccal cavity
→ water rushes over the gills into the opercular cavity
why do gill filaments overlap
to increase resistance, which means that water flows slower so there is more time for gas exchange to occur
what does countercurrent flow mean
blood in the gills flows in the opposite direction to the water
countercurrent flow maintains a
very steep concentration gradient
countercurrent flow means that a higher
oxygen saturation can be achieved
