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B3 > Exchange surfaces and breathing > Flashcards

Exchange surfaces and breathing Flashcards

1
Q

What are the 3 main factors that affect the need for an exchange system?

A
  • size
  • surface area to volume ratio
  • level of activity
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2
Q

How does size affect the need for an exchange system?

A
  • small organisms (single celled) can receive a sufficient supply of oxygen from environment by diffusion
  • for multicellular organisms diffusion is too slow to enable sufficient supply to innermost cells
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3
Q

How does SA:V affect the need for an exchange system?

A
  • small organisms have a large SA:V, SA is large enough for sufficient oxygen to diffuse into all cells.
  • large organisms have small SA:V
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4
Q

How does level of activity affect the need for an exchange system?

A
  • some organisms are more active than others
  • cells of active organism need good supplies of nutrients and oxygen to supply energy for movement
  • organisms (mammals) that keep themselves warm need more energy.
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5
Q

What are the features of a good exchange surface?

A
  • large surface area to provide more space for molecules to pass through. Walls are often folded (root hair cells).
  • permeable and thin barrier to reduce diffusion distance (alveoli)
  • good blood supply to maintain steep conc gradient for fast diffusion ( and removal of metabolic waste products that can be toxic)
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6
Q

What are alveoli?

A

tiny folds of the lung epithelium to increase the SA

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7
Q

What’s the trachea?

A

main airway leading from the back of the mouth to the lungs

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8
Q

What are bronchi and bronchioles?

A

smaller airways leading into the lungs

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9
Q

What’s the diaphragm?

A

layer of muscle beneath the lungs

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10
Q

What are intercostal muscles?

A

muscle between the ribs

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11
Q

What’s ventilation?

A

the refreshing of the air in the lungs so there’s a higher oxygen concentration than in blood, and lower carbon dioxide conc for fast diffusion

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12
Q

Why are alveoli so numerous?

A

large SA to provide more space for molecules to pass through

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13
Q

Why does surfactant coat internal surface of alveoli?

A
  • to reduce the cohesive forces between water molecules as they make alveoli collapse
  • also helps gases dissolve
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14
Q

What the barrier to exchange comprised of?

A
  • wall of alveolus
  • wall of capillary
  • cells readily allow diffusion of oxygen and carbon dioxide as they’re small and non polar
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15
Q

How is the barrier to exchange thin to reduce diffusion distance?

A
  • alveolus and capillary walls are one cell thick
  • both consist of squamous epithelium (flattened or very thin cells)
  • capillary in close contact with alveolus wall
  • capillaries have narrow lumen so RBCs are close to air in alveoli.
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16
Q

Why is it important for blood to carry carbon dioxide from tissues to lungs?

A

ensures conc gradient of CO2 in blood is higher than that in air in alveoli so carbon dioxide diffuses into alveoli

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17
Q

Why is it important for blood to carry oxygen away from lungs?

A

ensures that the conc of oxygen in blood is kept lower than that in alveoli so oxygen diffuses into the blood

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18
Q

Explain inspiration

A
  • diaphragm contracts to move down and becomes flatter (this displaces the digestive organs downwards)
  • external intercostal muscles contract to raise ribs
  • volume of chest cavity increases
  • pressure in chest cavity drops below atmospheric pressure
  • air moves into the lungs
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19
Q

Explain expiration

A
  • diaphragm relaxes and moves upwards (is pushed up by displaced organs underneath)
  • external intercostal muscles relax and ribs fall
  • during exercise, coughing, sneezing, internal intercostal muscle contract to push air out more forcefully
  • volume of chest cavity decreases
  • pressure in lungs rises above atmospheric pressure
  • air is moved out of lungs
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20
Q

What kind of fibres do alveoli contain and why?

A
  • elastic fibres help them stretch during inspiration but then recoil to help push air out doing expiration
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21
Q

What must airways have to be effective?

A
  • be large enough to allow sufficient air to flow in without obstruction
  • be supported to prevent collapse when the air pressure inside is low during inspiration
  • be flexible in order to allow movement
22
Q

What do airways contain?

A
  • lined by ciliated epithelium, keeps lungs healthy
  • goblet cells in epithelium release mucus to trap pathogens
  • cilia move mucus to top of throat where it’s swallowed
  • glandular tissue in the loose tissue also produces mucus
  • supported by C-shaped rings of cartilage to prevent collapse during inspiration
  • C-shaped rings allow flexibility for food to pass down oesophagus
23
Q

Difference between trachea and bronchi?

A
  • similar wall structure but bronchi are narrower
24
Q

Features of bronchioles

A
  • much narrower than bronchi
  • smaller ones don’t have cartilage
  • wall made of smooth muscle and elastic fibres
  • smallest ones end in clusters of alveoli
25
Q

Explain contraction of smooth muscle in airways

A
  • constricts airways
  • lumen becomes narrower
  • restricts airflow to and from alveoli
  • important if there’s a harmful substance in the air
  • not voluntary (may be allergic reaction)
  • can’t be reversed on its own
  • smooth muscle elongated again by elastic fibres
  • elastic fibres deformed (during contraction) then recoil (during muscle relaxation), dilating the airway
26
Q

What’s a spirometer?

A
  • device that can measure the movement of air into and out of the lungs
27
Q

What’s vital capacity?

A

maximum volume of air that can be moved by the lungs in one breath

28
Q

What’s tidal volume?

A

the volume of air inhaled or exhaled in one breath, usually measured at rest

29
Q

What’s oxygen uptake?

A

volume of oxygen absorbed by the lungs in one minute

30
Q

What’s residual volume?

A

volume of air that remains in the lungs even after forced expiration

31
Q

What factors can affect vital capacity?

A
  • size of person (height)
  • age and gender
  • level of regular exercise
32
Q

How to calculate oxygen uptake from a spirometer trace?

A
  • as person breathes from the spirometer, O2 is absorbed by blood and replaced by CO2
  • CO2 absorbed by soda lime in spirometer so volume of air in chamber decreases.
  • assume volume of carbon dioxide released during expiration and absorbed by soda lime equals the volume of oxygen absorbed by blood
  • measure gradient of the decrease in volume
33
Q

How to calculate breathing rate from spirometer trace?

A
  • count number of peaks in each minute
34
Q

What factors can increase oxygen uptake?

A
  • exercise
  • increased breathing rate
  • deeper breaths
35
Q

equation for pulmonary ventilation rate

A

PVR = tidal volume x breathing rate

36
Q

What’s the buccal cavity?

A

the mouth

37
Q

What’s counter current flow?

A

blood flows through capillaries in gill filament in opposite direction to flow of water over lamellae for maximum absorption of oxygen from water as there’s a steep conc gradient

38
Q

what are gill filaments/primary lamellae?

A

slender branches of tissue that make up the gill

39
Q

what is secondary lamellae/gill plate?

A

folds of the gill filament to increase SA

40
Q

what’s the operculum?

A

bony flap that covers and protects gills

41
Q

How many pairs of gills in bony fish?

A

5

42
Q

Structure of gills and advantages of this

A
  • two rows of gill filaments (primary lamellae) attached to a bony arch.
  • filaments are very thin and their surface is folded into many secondary lamellae (or gill plates)
  • provides large SA
  • blood capillaries carry deoxygenated blood close to surface of secondary lamellae where exchange occurs
43
Q

How does ventilation in fish occur?

A
  • floor of buccal cavity moves downward drawing water inside
  • mouth closes, floor raised pushing water through the gills
  • operculum moves outwards which reduces pressure in the opercular cavity (space under the operculum) helping water flow through gills
44
Q

define tracheal system?

A

system of air-filled tubes in insects

45
Q

define tracheal fluid

A

fluid found at the end of tracheoles in the tracheal system

46
Q

what’s a spiracle?

A

pore that allows air in or out of trachea

47
Q

Describe the circulatory system in insects

A
  • open circulatory system where body fluid acts as both blood and tissue fluid
  • circulation is slow and affected by body movements
48
Q

How does gaseous exchange occur in insects?

A
  • occurs between air in tracheole and the tracheal fluid
  • some exchange occurs across thin walls of the tracheoles
    -tracheal fluid withdrawn into body fluid to increase SA of tracheole wall exposed to air for more diffusion of oxygen in very active insects
49
Q

How is the tracheal system ventilated?

A
  • abdominal muscles contract and relax, changing volume of their bodies and move air in and out of spiracles
  • when larger insects are flying, wing movements pump their thoraxes too.
50
Q

adaptations of tracheal system

A
  • large SA:V - many branching tracheoles
  • short diffusion distance - many branching tracheoles reach muscle and thin-walled tracheoles
  • maintaining a conc gradient - when cells respire, they use O2 and produce CO2. Abdominal muscles contract to pump air

B3 (3 decks)

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