Exchange Flashcards
what are the five characteristics of exchange surfaces?
- large surface area increases rate of exchange
- very thin so short diffusion pathway
- selectively permeable
- movement of environmental medium to maintain a diffusion gradient
- a transport system to maintain a diffusion gradient
how does gas exchange occur within insects?
spiracle > tracheae > tracheoles > to muscles and body tissue
what are three ways in which respiratory gases move in and out of the tracheal system by?
- along a diffusion gradient
- mass transport
- the ends of the tracheoles are filled with water
why are the ends of the tracheoles filled with water?
muscle cells carry out anaerobic respiration, produces lactate which LOWERS water potential.
water in tracheoles decrease in volume and draws air further into them. diffusion is more rapid.
what are the conditions for effective diffusion in insects?
a short diffusion pathway - which is why insects are of such small size.
how does gas exchange occur within fish?
gills > gill filaments > gill lamellae
what is the counter-current exchange principle?
blood and water in opposite directions
diffusion takes place twice
diffusion gradient maintained across entire width of gill lamellae
roughly 80% of oxygen available absorbed
if in same direction, then only 50% of oxygen available would be absorbed (as diffusion gradient would only be maintained across part of the length of the gill lamellae)
what is the structure of a plant leaf?
short, fast diffusion pathway
very large surface area in the air spaces within a leaf
what are leaf adaptations for rapid diffusion?
many stomata
numerous interconnecting air-spaces so that ready contact with mesophyll
large surface area of mesophyll
where can you find stomata?
on the bottom of the leaf, but also a few on the top
what are the adaptations of stomata?
they can open and close to control rate of gaseous exchange as well as conserve water
what are the three adaptations of insects the reduce water loss?
small SA:V ratio - to minimise area where water lost
waterproof coverings - rigid chitin skeleton covered with a waterproof cuticle
spiracles - can be closed to reduce water loss
what are xerophytes?
plants that are adapted to living in areas where water is in short supply
what are five plant adaptations to reduce water loss?
- a thick cuticle
- rolling up of leaves
- hairy leaves
- stomata in pits or grooves
- a reduced SA:V ratio of the leaves
what are the main parts of the human gas exchange system?
lungs > trachea > bronchi > bronchioles > alveoli
what is ventilation?
breathing - when air is constantly moving in and out of the lungs
what is inspiration?
inhalation - when air pressure of the atmosphere is greater than the air pressure inside the lungs, air is forced into the lungs
what is expiration?
exhalation - when the air pressure in the lungs is greater than that of the atmosphere, air is forced out of the lungs
what does the contraction of both sets of intercostal muscles lead to?
internal intercostal muscles - leads to expiration
external intercostal muscles - leads to inspiration
what are the five things that happen during inspiration?
external intercostal muscles contract
ribs upwards and outwards
diaphragm contracts (downwards), increase in volume of thorax
reduction in pressure in lungs
atmospheric pressure now greater than pulmonary pressure, air forced into lungs
what are the five things that happen during expiration?
internal intercostal muscles contract
ribs downwards and inwards
diaphragm relax (upwards), volume of thorax decreases
increase in pressure in lungs
pulmonary pressure now greater than that of the atmosphere, and so air is forced out of the lungs
what are six reasons for diffusion between the alveoli and the blood being rapid?
- rbc slowed as they pass through pulmonary capillaries, allowing more time for diffusion
- distance between the two is reduced
- walls of both alveoli and capillaries are very thin, therefore diffusion distance is short
- alveoli and pulmonary capillaries have a very large total surface area
- steep concentration gradient of gases to be exchanged is maintained
- blood flow through the pulmonary capillaries maintains a concentration gradient
what is the structure of the digestive system?
salivary glands > oesophagus > stomach > ileum (small intestine) > large intestine > rectum
pancreas secretes pancreatic juices
how does physical breakdown occur?
through chewing using teeth
muscles in stomach wall churn the food up
