Gas Exchange Flashcards
1
Q
what is the journey of gas from the air into an insect?
A
- spiracles (controlled by sphincters)
–> tracheae
–> tracheoles
–> tracheal fluid
–> respiring tissues
2
Q
three adaptations of tracheoles
A
- located in between cells (short diffusion distance)
- tracheal fluid dissolves the gases
- many long, thin tracheoles (large SA:V ratio)
3
Q
what is a key difference between tracheae and tracheoles?
A
tracheae have chitin spiralled around them for structural support, tracheoles don’t (to increase permeability for gas diffusion)
4
Q
what two things do some insects also have/do?
A
- mechanical ventilation
–> air actively drawn in and expelled by contractions of abdomen and thorax muscles (causing pressure changes) - collapsible enlarged trachea/air sacs
–> act as air reservoirs, inflate and deflate by abdomen and thorax movement
5
Q
how does tracheal fluid affect rate of diffusion?
A
- when a tissue is active and anaerobically respiring, lactic acid builds up
- Ψ of the respiring cells decreases
- tracheal fluid diffuses into repairing tissue via osmosis
- less tracheal fluid in the tracheoles
- gas diffuses quicker through gas than liquid AND this exposes a greater surface area for diffusion
6
Q
what is the journey of gas from the air into a mammal?
A
- nasal/oral cavity
- trachea
- bronchi
- bronchioli
- alveoli
7
Q
where is cartilage found in the mammalian exchange system?
A
- C shaped rings around the trachea
- full rings around the bronchi
8
Q
three nasal cavity adaptations
A
- wrinkled to increase SA:V ratio
- moist to prevent air from drying out lungs
- good blood supply to warm air and maintain body temperature
9
Q
one adaptation of the trachea
A
- lined with ciliated epithelium cells and goblet cells
10
Q
structure of a bronchiole
A
- smooth muscle (to relax and constrict to promote air flow)
- mucous membrane
- 1mm diameter lumen
11
Q
six aeveoli adaptations
A
- squamous epithelial cells containing collagen and elastic fibres (elastic recoil to expell air)
- one cell thick walls (decrease diffusion distance)
- large SA:V ratio
- large network of capillaries (and constant ventilation maintains steep diffusion gradient)
- moist (dissolve gases)
- lung suffocant (prevent alveoli collapsing)
12
Q
how does lung surfactant work?
A
- lipoprotein creates barrier between water molecules on the inner surface of the alveoli (similar to oil)
- this breaks the surface tension and makes it easier for lungs to inflate
13
Q
ventilation
A
the movement of air into and out of the lungs as a result of pressure changes brought about by breathing movements
14
Q
inspiration (mechanism)
A
- diaphragm and the external intercoastal muscles contract
- rib cage moves up and out
- volume in thorax increases
- pressure in thorax decreases
- air moves out of the lungs down a pressure gradient
15
Q
expiration (mechanism)
A
- diaphragm and external intercostal muscles relax
- rib cage moves down and in
- volume in thorax decreases
- pressure in thorax increases
- air moves out of the lungs down a pressure gradient
16
Q
internal vs external intercoastal muscles
A
- internal intercostal muscles are relaxed during both inspiration and expiration (unless air is being forcefully expelled)
- external intercostal muscles contract during inspiration and relax during expiration
17
Q
what is the journey of gas from water to a fish?
A
- buccal cavity
- through gills
- into opercular cavity
- out of opercular valve
18
Q
how is water moved through the gills?
A
- floor of the buccal cavity is lowered
- increases the volume and decreases the pressure of the buccal cavity
- water moves into the buccal cavity down a pressure gradient
- opercular valve closes
- increases the volume and decreased the pressure of the opercular cavity
- water moves through the gills into the operculae cavity down a pressure gradient
- floor of the buccal cavity moves up
- opercular valve opens and sides of operculum move in
- decreases the volume and increases the pressure in the opercular cavity
- water moves out of opercular cavity (out of fish) down a pressure gradient
19
Q
structure of a gill
A
- bone arch
- many gill filaments along bone arch
- gill lamellae (semi-circular plates on top of gill filaments)
- rakers filter out small particles of sediment/food etc
20
Q
adaptations of gills
A
- thin gill filaments close to capillaries (short diffusion distance)
- gill lamellae (increase surface area and slow water flow to allow more time for gas diffusion)
- tips of gills overlap (slow water flow)
- rich blood supply AND countercurrent flow (maintain steep diffusion gradient)
21
Q
what is the problem with gas exchange underwater?
A
the concentration of oxygen in the water is lower than that in the atmosphere so there is a lower concentration gradient (slower diffusion)
22
Q
how does countercurrent flow work?
A
- blood flows in the opposite direction to the water
- maintains a steep diffusion gradient AND avoids oxygen concentrations in water and the blood reaching equilibrium (more than 50% O2 diffuses into blood)
- diffusion can occur along the whole length of the gill
23
Q
five limitations of the bell jar model
A
- nasal and oral cavity aren’t represented
- bornchi and alveoli aren’t represented
- represents ventilation but not gas exchange
- jar is fixed and cannot move up and out (no intercostal muscles)
- jar is filled with air rather than tissue and fluid like the thorax (differences in internal pressure)
24
Q
three ways lung volume can be measured
A
- peak flow (rate at which air can be expelled from lungs)
- vitalograph (more sophisticated peak flow)
- spirometer (measures different aspects of lung volumes and breathing patterns)
25
how to use a spirometer (8 steps)
- calibrate one litre and one minute (create a scale for volume and time on the trace)
- fill drum with fresh air
- subject must be in good health
- subject must wear nose clip (only air inspired comes from spirometer)
- use a sterile mouthpiece
- subject breathes into spirometer (get used to it)
- turn on kymograph (spins paper and moves up and down to draw trace on)
- subject breathes normally for at least three breaths (tidal volume)
26
what must the spirometer contain and why?
soda lime to absorb CO2 and avoid gas poisoning
27
ventilation rate equation (with units)
tidal volume (dm³) x inspiration frequency (min-¹)
28
ventilation rate units
dm³min-¹
29
why does the spirometer trace slope downwards over time?
CO2 is absorbed by the soda lime which decreased the volume in the spirometer
(gas out of spirometer < gas into spirometer)
