Exchange surfaces Flashcards
1
Q
reasons for exchange systems in large multicellular organisms
A
- large multicellular organisms have a small surface area to volume ratio
- cells in the centre of organisms wouldn’t receive any materials if they relied on diffusion alone - diffusion distance too far
- multicellular organisms have a higher metabolic rate so oxygen demands are higher and more CO2 is produced - they need to exchange lots of materials fast
2
Q
features of efficient gas exchange surfaces
A
- large surface area eg. root hair cells
- thin layers eg. alveoli
- good blood supply - maintains conc. gradient so diffusion can take place faster eg. gills, alveoli
- ventilation - maintains diffusion gradient eg. gills, alveoli
3
Q
features of nasal cavity
A
- larger surface area and good blood supply - warms the air as it passes into the body
- hairy lining which secretes mucus - traps dust and bacteria to prevent them reaching lungs
- moist surfaces - increases humidity of incoming air - reduces evaporation from exchange surfaces
4
Q
trachea features in gas exchange
A
- supported by layer of cartilage holding it open and preventing it collapsing
- rings of cartilage are incomplete to allow it to bend when food is swallowed in the oesophagus behind
- lined with ciliated epithelial cells (beat regularly moving mucus with bacteria along) and goblet cells (secrete mucus) that prevent dust and bacteria entering
5
Q
bronchus
A
- trachea splits into 2, 1 for each lung
- similar structure to trachea
- smaller cartilage rings hold pipe open
6
Q
bronchioles
A
- bronchus split into much smaller tubes - 1mm or less diameter
- no cartilage - held open by smooth muscle
- muscle contracts and bronchioles constrict, muscle relaxes, bronchioles dilate - changes amount of air reaching lungs
- lined with thin layer of epithelium making some gas exchange possible
7
Q
alveoli
A
- little air sacs
- made of thin layer squamous epithelial cells and some collagen and elastic fibres
- epithelium is one cell thick - short diffusion distance
- elastic fibres allow recoil helping air move in and out of alveoli - (elastic recoil) - helps with ventilation
- they secrete lung surfactant coat inner surface of alveoli preventing them from collapsing from the surface tension
- large number of alveoli provide large SA
- good blood supply, good ventilation - maintains steep conc grad for oxygen to diffuse from the lung surface to the blood and for CO2 to diffuse from the blood to the lungs and leave the body
8
Q
inspiration
A
- diaphragm contracts, flattens, lowers
- intercostal muscles contract causing ribs to move up and out
- thoracic volume increases
- thoracic pressure decreases
- air flows into lungs to equalise pressure difference
- active
9
Q
expiration
A
- diaphragm relaxes, moves up
- intercostal muscles relax so ribs move down and in
- thoracic volume decreases
- thoracic pressure increases
- air flows out of lungs to equalise pressure differences
- passive
10
Q
how do you use a spirometer?
A
- lower half of tank filled with water
- upper half full of oxygen
- breathe out into tank and upper half will rise
- breathe in from the tank and upper half will fall
- trace marker attached to mobile upper half
11
Q
why does the overall volume of the tank decline over time?
A
- sod lime absorbs carbon dioxide
- when breathing we use up oxygen from tank while carbon dioxide we breathe out is absorbed by soda lime
- gas volume of tank decreases because oxygen is used up by ppt
12
Q
precautions when using spirometer
A
- patient free from asthma and healthy
- soda lime fresh and functioning
- check for air leaks in apparatus
- sterilise mouthpiece
- don’t overfill water chamber
13
Q
tidal volume
A
- amount of air moving in and out of lungs during breathing at rest (smallest wave)
14
Q
inspiratory reserve volume
A
- how much extra air breathed in during forced inspiration (large wave going down)
- measure inspiratory capacity above tidal volume
- uses extra muscles
15
Q
expiratory reserve volume
A
- how much extra air is breathed out during forced expiration (smaller wave than inspiratory, going upwards)
- measures expiratory capacity beyond tidal volume
- uses different muscles
16
Q
residual volume
A
- volume remaining in lungs after maximum expiration (section below inspiratory residual volume)
17
Q
vital capacity
A
- largest possible volume change in lungs
- from max inspiration to max expiration
18
Q
total lung capacity
A
- vital capacity and residual volume
- everything
19
Q
breathing rate from spirometer
A
count number of breaths (peaks) in a minute
20
Q
rate of oxygen consumption from spirometer
A
- difference between inspiratory volume at start and end (how much has it gone down)
- divide by duration of experiment
21
Q
gas exchange in insects
A
- each segment of insect has pair of spiracles (openings)
- tracheae - connected to spiracles, lined with chitin to keep them open
- branch into tracheoles - divide until numerous microscopic ends penetrate into body cells, no chitin lining
- oxygen moves down conc. gradient into tracheoles and dissolves in moisture on walls
- tracheal fluid at the end of tracheoles limits diffusion, but when oxygen demand is high lactic acid builds up and water moves out tracheoles increasing SA for oxygen
- carbon dioxide moves down conc gradient into air
22
Q
ventilation in insects
A
- rhythmic muscular movements of abdomin/thorax
- changes volume and pressure in tracheoles
- generates mass movements of air in and out of tracheal tubes
- ventilation movements also inflate the collapsible tracheae, increasing air moving in and out
23
Q
structure of gas exchange in fish
A
- gills contained in gill cavity and covered by bony flap called operculum
- each gill consists of rows of gill filaments attached to bony arch
- gill filaments occur in stacks (gill plates) - provides large surface area and require water flow to keep them apart
- capillaries carry oxygenated blood to surface of gill lamellae where gas exchange takes place
24
Q
countercurrent flow in fish
A
- water and blood move in opposite directions
- this maximises amount of oxygen absorbed from water - maintains high conc. gradient
25
Q
ventilation in bony fish
A
so fish don’t have to keep moving for water to flow over gills
- floor of buccal cavity (mouth) moves downwards, increasing volume, lowering pressure and drawing water in
- meanwhile, the opercular valve is shut
- mouth closes and floor is raised, increases pressure, starts pushing water through gills
- operculum opens - opercular cavity walls move inwards, increasing pressure, helping water flow through gills
