3.1 Exchange Surfaces and Breathing ✓

-size
-SA:V
-level of activity

Very small organisms: short diffusion pathway (cytoplasm close to environment so diffusion supply enough O and nutrients)
Large multicellular organism: long diffusion pathway (several layers of cells so diffusion can't provide O and nutrients for innermost cells sufficiently)

Very small organisms: large SA:V so SA used as exchange surface
Large multicellular organism: small SA:V so SA not large enough to be used as an exchange surface

Some organisms have higher metabolic activity than others which need more O and nutrients (especially mammals which also keep themselves warm)

-large SA for more space for molecules to pass through (often achieved by folded membrane)
-thin, permeable (to substances exchanged) barrier to reduce diffusion distance
-good blood supply: steep concentration gradient for rapid diffusion (fresh molecule supply at supply side keeping high concentration gradient or remove molecules from demand side to keep concentration low)

tiny folds of lung epithelium to increase SA

muscles between ribs

refreshing air in lungs so higher O concentration than in blood and lower CO2 concentration

nasal passage/ mouth cavity -> trachea -> bronchi -> bronchioles -> alveoli

ribcage

layer of muscle beneath lungs

breathing movements/ ventilation

alveoli

to reduce cohesive forces between water molecules which otherwise collapse alveoli

small and non polar

1 cell

1 cell

-thin alveolus and capillary wall
-both walls consist of squamous cells
-capillaries in close contact with alveolus wall
-capillaries narrow so red blood cell squeezed against capillary wall

flattened/ very thin cell

closer to air and reduces rate of flow

contracts to move down + flatten, displacing digestive organs downwards

relaxes and pushed up by displaced organs beneath

contract to raise ribs

relax and ribs fall

push air out more forcefully (eg sneeze)

increases

decreases

drops below atmospheric pressure

rises above pressure in surrounding atmosphere

form of connective tissue

layer of cells that have hair like extensions called cilia

protein fibres that can deform and recoil to original size

cell that secretes mucus

involuntary muscle contracting without need for conscious thought

squamous epithelium

-large enough to allow air flow without obstruction
-supported to prevent collapse when low pressure
-felxible for movement

ciliated epithelium

release mucus to trap pathogens

move mucus to top of airway where it is swallowed

rings of cartilage

C-shaped to allow flexibility and space for food travelling down oesophagus

no, larger ones have some but smaller ones dont

smooth muscle and elastic fibres

constricts airway making lumen of airway narrower and restricting airflow

if harmful substances in the air or allergic reaction

smooth muscle elongated by elastic fibres recoiling

number of breaths per min

volume of oxygen absorbed by lungs in one min

volume of air inhaled/ exhaled in one breath

at rest

device that measures movement of air in and out of lungs

greatest volume of air that can be expelled from lungs after taking deepest possible breath

chamber of air/ medical grade oxygen floating on tank of water where...
-inspiration: air drawn from chamber so lid moves down
-expiration: air returns to chamber raising lid
Lid movement measured on datalogger

passes through chamber of soda lime where CO2 absorbed to allow measurement of oxygen consumption

-subject should be healthy (in particular not have asthma)
-soda lime fresh and functioning
-no air leaks
-mouthpiece sterilised
-water chamber not overfilled

would lead to inaccurate results

water may enter air tubes

rate of oxygen consumption

vital capacity + residual volume

-size of person
-age and gender
-level of regular exercise

2.5-5dm3

higher

0.5dm3

-CO2 absorbed by lime water causes overall decrease in volume of air chamber in spirometer
-measure gradient of decrease in volume on trace

carbon dioxide exhaled= oxygen inhaled

count number of peaks in each minute

12-14 breaths per min

increase

-increased breathing rate
-deeper breaths

mouth

where 2 fluids move in opposite directions

slender branches of tissue making up gill

primary lamellae

gill plates

folds of primary lamallae to increase SA

bony flap that covers and protects gills

external opening/ pore that allows air in/ out tracheae

fluid found at the ends of tracheoles in tracheal system

system of air-filled tubes in insects

5

2

opposite

Keeps ideal concentration gradient of oxygen consistent between water and blood

space under operculum

buccal-opercular pump

-floor of mouth moves down, drawing water into buccal cavity
-mouth closes
-floor of mouth raises, pushing water through gills
-as water pushed from buccal cavity, operculum moves outwards, reducing pressure in opercular cavity helping water flow through gills

open

yes

tracheal fluid and air in tracheole (some across thin walls of tracheoles)

spiracle -> tracheae -> tracheoles ->tracheal fluid

open and filled with tracheal fluid

tracheal fluid withdrawn into body fluid so SA of tracheole wall exposed to air increased so more oxygen absorbed when insect active

-sections of flexible wall act as air sacs which are squeezed by action of flight muscles
-repetitive expansion and contraction causes ventilation

-movement of wings alter volume of thorax
-thorax volume decreases: air in tracheal system put under pressure and pushed out
-thorax volume increases: pressure inside drops so air pushed into tracheal system

-alter abdomen volume by specialised breathing movements
-abdomen expands: spiracles at front of body open so air enters
-abdomen volume decreases: spiracles near rear open and air leaves