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Biology Year 12 > 7 - Exchange surfaces and breathing > Flashcards

7 - Exchange surfaces and breathing Flashcards

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1
Q

Why are specialised exchange surfaces not needed in single-celled organisms?

A
  • diffusion alone is enough to supply needs.
  • low metabolic activity.
  • large surface area : volume ratio
  • short diffusion distance (cell surface membrane)
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2
Q

Why do large multicellular organisms require specialised exchange surfaces?

A
  • small surface area : volume ratio
  • higher metabolic rate
  • distance between supply of oxygen and cells that require oxygen is too great.
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3
Q

How does SA:V ratio affect rate of diffusion?

A
  • the larger the organism
  • smaller SA:V ratio
  • distance the substances need to travel from outside to reach the cells at centre of body increases.
  • impossible to absorb enough oxygen through available surface area to meet needs of the body.
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4
Q

What are the features of an efficient exchange surface.

A
  • increased surface area: provides for area for diffusion to occur (root hair cells)
  • thin layers: provides a short diffusion distance so process is fast and efficient (alveoli)
  • good blood supply and ventilation: to maintain a steep concentration gradient
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5
Q

features of the nasal cavity

A
  • large surface area
  • good blood supply
  • which warms air to body temperature.
  • moist surfaces: increases humidity of incoming air.
  • hairy lining
  • mucus is secreted to trap dust, microorganisms.
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6
Q

c shaped and incomplete rings of cartilage in trachea and bronchus

A
  • for structure and support

- prevents airways from collapsing

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7
Q

Why are the rings of cartilage in trachea incomplete?

A
  • too allow easy movement of food through oesophagus behind trachea.
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8
Q

role of ciliated epithelium in trachea and branches?

A
  • have cilia which waft and beat mucus with trapped dust and microorganisms to back of throat.
  • goblet cells secrete a sticky substance called mucus which trap dust and microorganisms.
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9
Q

effect of cigarettes on gaseous exchange system?

A
  • stops the cilia from beating.
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10
Q

smooth muscle

A
  • controls the diameter of the airways (trachea, bronchus, bronchioles).
  • during exercise, smooth muscle relaxes, making airways wider.
  • resistance to airflow decreases.
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11
Q

elastic fibres

A
  • aids expiration
  • during inspiration, elastic fibres are stretched.
  • during expiration, the elastic fibres recoil to help push air out during expiration.
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12
Q

features of trachea

A
  • incomplete rings of cartilage: prevents trachea from collapsing.
  • ciliated epithelium
  • goblet cells between and below ciliated epithelial cells.
  • smooth muscle
  • elastic fibres
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13
Q

features of bronchus

A
  • rings of cartilage: prevents bronchus from collapsing.
  • ciliated epithelium
  • goblet cells between and below ciliated epithelial cells.
  • smooth muscle
  • elastic fibres
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14
Q

features of bronchioles

A
  • smaller bronchioles (1mm diameter or less) do not have rings of cartilage.
  • smooth muscle (contract → bronchioles constrict, relax → bronchioles dilate.
  • thin layer of flattened epithelium, for some gaseous exchange.
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15
Q

FEATURES OF ALVEOLI

A
  • squamous epithelial cells (1 cell thick) (thin layers) provides a short diffusion distance.
  • moist lining of lung surfactant. Helps to dissolve oxygen so it can be easily diffused into the capillaries.
  • lots of them provide a large surface area for efficient diffusion.
  • rich network of capillaries means good blood supply. Maintains steep concentration gradient.
  • good ventilation. Maintains steep concentration gradient.
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16
Q

mechanism of INSPIRATION

A
  • diaphragm contracts and flattens.
  • external intercostal muscles contract
  • ribcage moves up and outwards
  • thoracic volume increases
  • pressure decreases
  • air rushes in to lungs to equalise the pressure.
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17
Q

mechanism of EXPIRATION

A
  • diaphragm relaxes and moves up, curves.
  • external intercostal muscles relax.
  • ribcage moves down and inwards.
  • thoracic volume decreases.
  • pressure increases
  • air rushes out of lungs to equalise the pressure.
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18
Q

mechanism of FORCED EXPIRATION

A
  • internal intercostal muscles contract
  • ribcage moves further down and inwards.
  • thoracic volume decreases further.
  • pressure increases
  • air is forced out of the lungs.
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19
Q

Tidal volume

A
  • the volume of air in each resting breath. around 500cm3.
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20
Q

vital capacity

A
  • maximum volume of air that can be breathed in or out.
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21
Q

inspiratory reserve volume

A
  • maximum volume of air that can be breathed in above a normal inhalation.
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22
Q

expiratory reserve volume

A
  • extra amount of air you can force out of your lungs after a normal exhalation.
23
Q

residual volume

A
  • the volume of air left in your lungs after exhaling as hard as possible.
  • cannot be measured directly.
24
Q

total lung capacity

A
  • sum of the vital capacity and the residual volume
25
Q

breathing rate

A

number of breaths taken in a minute.

- breaths are the peaks in a spirometry graph.

26
Q

oxygen uptake

A

the rate at which an organism uses up oxygen.

27
Q

spirometry when exercising?

A
  • tidal volume increases 15 to 50%
  • breathing rate increases
  • ventilation of lungs increases
  • oxygen uptake increases.
  • to meet metabolic demands of tissues.
28
Q

why is a canister of soda lime used in a spirometer?

A
  • to remove carbon dioxide produced.

- to prevent carbon dioxide poisoning.

29
Q

What are spiracles?

A
  • small openings along the thorax and abdomen of an insect.
  • air enters and leaves the gaseous exchange system through them.
  • water is lost from here as well.
30
Q

what controls the opening and closing of spiracles?

A

sphincters

31
Q

why are spiracle sphincters kept closed as much as possible?

A

to minimise water loss.

32
Q

What kind of cartilage does the trachea and bronchi have?

A

trachea: C-shaped rings of cartilage
bronchi: incomplete rings of cartilage.

33
Q

When are spiracles closed and opened? How many?

A
  • inactive and low oxygen demands: spiracles will all be closed most the time.
  • active, higher oxygen demands, increase in CO2 levels, more spiracles open up.
34
Q

What are tracheae in insects?

A
  • largest tubes of the insect respiratory system 1mm diameter.
  • carries air into the body.
  • run into and along the body.
35
Q

What material is the trachea lined with?

A
  • spirals of chitin

- relatively impermeable to gases so little gaseous exchange occurs in the tracheae.

36
Q

What are tracheoles?

A
  • branched from tracheae.
  • minute tubes
  • 0.6-0.8um
  • single greatly elongated cell.
  • no chitin, freely permeable to gases.
  • runs between individual cells.
  • where most of gaseous exchange between air and respiring cells take place.
37
Q

Why do the tracheoles provide a good exchange surface?

A
  • lots of them, provides very large surface area for gaseous exchange.
38
Q

What is tracheal fluid?

A
  • present towards the ends of tracheoles.
  • limits the penetration of air for diffusion.
  • oxygen dissolves in the fluid which is then diffused into the respiring cells.
39
Q

What happens to tracheal fluid when oxygen demands are high?

A
  • lactic acid build-up in tissues
  • water (part of the tracheal fluid) moves out of the tracheoles by osmosis.
  • exposes more surface area in the tracheoles for gaseous exchange to occur.
40
Q

What system provides oxygen needed by cells in insects?

A

tracheal system.

41
Q

What controls the extent of gas exchange in insects?

A

opening and closing of spiracles.

42
Q

what methods do larger insects have to increase levels of gaseous exchange?

A
  • mechanical ventilation of tracheal system

- collapsible enlarged tracheae or air sacs.

43
Q

mechanical ventilation of the tracheal system (insects)

A
  • air is actively pumped into the system
  • muscular pumping movements of the thorax and abdomen.
  • the movements change the volume of the body, changes pressure in tracheae and tracheoles.
  • air is drawn in or forced out the tracheae and tracheoles as pressure changes.
44
Q

collapsible enlarged tracheae or air sacs (insects)

A
  • inflated and deflated by the ventilating movements of the thorax and abdomen.
  • increases the amount of air moved through the gas exchange system.
  • acts as air reservoirs.
45
Q

roles of lung surfactants in alveoli?

A
  • helps to dissolve oxygen so that it can be easily diffused into the capillaries.
  • reduces the surface tension of water, allowing alveoli to expand.
46
Q

Why do bony fish require special adaptations for gaseous exchange?

A
  • small SA:V ratio
  • scaly outer covering does not allow gaseous exchange
  • oxygen concentration in water is much lower than in the air.
47
Q

in how many directions does water flow over the GILLS?

A

one direction

48
Q

features of gills for a successful gaseous exchange surface

A
  • bony gill arch supports structure of gills.
  • lots of gill filaments provide a large surface area for gaseous exchange.
  • gill plates are formed from lots of gill filaments stacked together. Gill plates have thin surfaces to increase rate of diffusion.
  • gill filaments contain lots of gill lamellae. Gill lamellae provide a large surface area and have a rich blood supply. Main site of gaseous exchange.
49
Q

What is operculum

A

The flap that covers the gills.

50
Q

stages of fish ventilation

A
  • mouth opens
  • volume of buccal cavity increases
  • pressure in the buccal cavity decreases
  • water moves into the cavity.
  • at the same time, opercular valve closes.
  • opercular cavity (containing gills) expands.
  • pressure of opercular cavity decreases
  • floor of buccal cavity moves upwards.
  • pressure of buccal cavity increases
  • water moves to opercular cavity and water moves over the gills.
  • mouth closes
  • opercular valves open
  • opercular cavity shrinks
  • pressure in opercular cavity increases.
  • water moves over the gills and out the opercular valves.
  • buccal cavity moves up steadily to maintain a flow of water over the gills.
51
Q

gill characteristics for gaseous exchange

A
  • countercurrent system: maintains an oxygen concentration gradient between water and blood along the entire length of the exchange system.
  • lots of gill filaments covered with gill lamellae: provides a very large surface area for gaseous exchange.
  • thin layers in lamellae and blood capillaries: provides a short diffusion distance.
  • rich blood supply, continual refreshing of oxygenated water: maintains oxygen concentration gradient.
52
Q

explain the counter current flow system?

A
  • blood and water flow in opposite directions.
  • oxygen concentration in water is always greater than in blood.
  • oxygen continues to diffuse down concentration gradient from water to blood.
  • oxygen concentration gradient is maintained all along the gill.
  • a high(er) saturation of oxygen in blood is achieved.
53
Q

why is a parallel flow system bad?

A
  • blood in gills and water flow in the same direction.
  • there is an initial steep oxygen concentration gradient between blood and water.
  • oxygen concentration in blood and water eventually reach equilibrium, no net movement of oxygen in blood occurs.
  • high oxygen saturation in blood cannot be reached.

Biology Year 12 (11 decks)

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