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Biology > Exchange Surfaces > Flashcards

Exchange Surfaces Flashcards

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1
Q

Why are exchange surfaces needed?

A
  1. Need substances for growth, survival and chemical reactions
  2. Remove waste
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2
Q

Why do large active animals need a specialised exchange surface?

A

• As size increases the SA:Vol ratio decreases ;
• As size increases the need for a specialised system to exchange oxygen & carbon dioxide increases ;
• Central regions are too far from surface (diffusion pathway too long) ;
• Rate of diffusion is too slow to meet metabolic requirements for metabolic activity ;
• Oxygen delivered too slowly (several layers of cells so long diffusion distance and cannot supply innermost cells sufficiently enough)
• Carbon dioxide removed too slowly ;
• More active organisms need higher rates of respiration to supply their cells with the energy that they
need – faster gas exchange and delivery of oxygen needed to achieve this ;

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3
Q

Why do single-celled organisms not need a specialised exchange surface?

A

Single-celled organisms have a large SA:V ratio so can remove waste/take nutrients straight from the surroundings due to the small diffusion distance

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4
Q

What is the surface area to volume ratio of multicellular organisms?

A

Large SA:V ratio

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5
Q

What are the features of an efficient gas exchange system?

A
  1. Large/increased surface area (i.e. root hair cells) - many exchange surfaces exposed to the air, increased rate of diffusion - often achieved by folding membranes
  2. Thin layer (i.e. alveolar walls are only one cell thick) - reduced diffusion distance
  3. Good blood supply/ventilation to maintain a diffusion gradient (i.e. gills/alveolus) - ensures efficient, rapid diffusion
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6
Q

Briefly describe why the mammalian exchange system is an efficient gas exchange system?

A

• Many alveoli to produce large surface area ;
• Barrier, thin / only two cells thick ;
• Good blood supply / many capillaries ;
‐ To carry dissolved gases to and from the alveoli ;
• Ventilation / air movement to refresh the air in the alveoli
• Elastic tissue to stretch and recoil to help expel air ;

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7
Q

What is the distribution and function of cartilage?

A
  • in trachea / bronchi ;
  • holds airway open / prevents collapse ;
  • prevents bursting (of trachea / bronchi as air pressure changes) ;
  • rings incomplete so food can move down the oesophagus easily
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8
Q

What is the distribution and function of goblet cells?

A
  • secrete mucus;
  • trap bacteria / dust / pollen / particles ;
  • protecting delicate lung tissue from infection and irritation
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9
Q

What is the distribution and function of ciliated epithelium/cilia?

A
  • move mucus ;
  • metachronal rhythm / wave / sweep / waft)
  • remove particles from lungs ;
  • found in bronchi and the trachea
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10
Q

What is the distribution and function of blood vessels?

A
  • supply oxygen / nutrients (to tissues of lung) ;
  • surround alveoli / good blood supply to alveoli ;
  • deliver carbon dioxide / pick up oxygen ;
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11
Q

What is the distribution and function of smooth muscle?

A
  • adjust size of airways (in, exercise / asthma) ;
  • found in the trachea, bronchi and bronchioles
  • contracts without the need for conscious thought
  • contracts to restrict the airway/air flow, making the lumen smaller - important when harmful substances are in the air
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12
Q

What is the distribution and function of elastic tissue?

A
  • stretch (inhalation) ;
  • prevents alveoli bursting ;
  • recoil ; R contract
  • helps exhalation / forces air out (of lungs) ;
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13
Q

What is the distribution and function of squamous epithelium?

A
  • alveolus wall thin ;
  • wall of capillary thin ;
  • ease of / rapid, gaseous exchange or short diffusion pathway ;
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14
Q

Draw the mammalian gas exchange system.

A

See flashcard

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15
Q

Describe the features of the trachea, bronchi and bronchioles.

A

Trachea, bronchioles and bronchi are flexible (allows movement), supported by cartilage (except bronchioles, which are lined with epithelium and have no cartilage) and are a hollow airway.

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16
Q

What is pleural fluid and where does it come from?

A

It acts as a lubricant to protect the epithelium and keep it moist. It is secreted by the pleural membrane.

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17
Q

Plural of bronchus

A

Bronchi

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18
Q

What are alveoli?

A

Tiny air-filled sacs

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19
Q

Describe inhalation/inspiration

A

‐ Diaphragm contracts (flattens), moving it down ;
‐ External intercostal muscles contract, moving the rib cage up and out ;
‐ Volume of the thorax increases ;
‐ Pressure in the thorax drops ;
‐ Air flows in, down a pressure gradient ;

20
Q

Describe exhalation/expiration, when relaxed.

A 
‐ Intercostal muscles and diaphragm relax (return to curve shape) ;
‐ Elastic fibres recoil  ;
‐ Rib cage moves down and in ;
‐ Volume of thorax decreases ;
‐ Pressure in thorax increases ;
‐ Air moves out of the lungs ;
21
Q

Describe exhalation/expiration, when forced (i.e. coughing, sneezing, exercise)

A

‐ Internal intercostal muscles contract ;
‐ Rib cage pulled down and in ;
‐ Abdominal muscles contract (raising diaphragm) ;
‐ Volume of thorax decreases ;
‐ Pressure in thorax increases ;
‐ Air forced out of the lungs ;

22
Q

How do lungs move?

A

Lungs have no muscle so movement is produced by muscles in the diaphragm and the intercostal muscles

23
Q

How does a spirometer work?

A
  • As the volunteer breathes in the lid goes down / breathes out the lid goes up ;
  • Movement of lid recorded on trace / by data logger ;
  • e.g. pen attached to lid moves down / up as volunteer breathes in / out ;
24
Q

Factors that should be considered when carrying out an experiment using a spirometer

A
  • Check health of volunteer ; (e.g. ask about asthma / TB / pneumonia / flu / bronchitis / emphysema)
  • Medical grade oxygen used to fill the air chamber ;
  • Sufficient oxygen in chamber ;
  • Sterilised / disinfected mouthpiece ; (for each volunteer)
  • Fresh soda lime present ; (need to remove CO2)
  • Water level not too high / water must not enter tubes ;
  • Ensure that valves are working correctly ;
  • Maintain constant temperature ; (so that volume of gases is not affected)
25
Q

Tidal volume

A

‐ The volume of air moved into / out of the lungs in a normal breath ;

26
Q

Vital capacity

A

‐ The max. volume of air that can be moved into / out of the lungs in one breath (depends on height, gender, etc)

27
Q

Breathing rate

A

A person’s breathing / ventilation rate is the number of breaths they take during a specific amount of time (minute)

28
Q

Why is soda lime important (in a spirometer)?

A

It is used to absorb carbon dioxide from the exhalation so it does not end up in the chamber, especially if someone is breathing for a long time so the person does not rebreath air with a high concentration of carbon dioxide.

29
Q

What does a spirometer assume?

A

Assumes that the volume of carbon dioxide absorbed is equal to the volume of oxygen taken up.

30
Q

Draw a spirometer.

A

See notes

31
Q

Describe how the spirometer would be used to measure tidal volume

A

‐ idea of not breathing through nose ; (e.g. subject wears nose clip)
‐ subject breathes , evenly / normally / regularly ;
‐ idea of (measure) height / amplitude , of waves (from trace)

32
Q

Explain why the volume of air in the spirometer drops slowly over the first minute

A

‐ oxygen is used in respiration ;
‐ carbon dioxide is released ( in respiration) ;
‐ carbon dioxide is absorbed (by soda lime) ;

33
Q

Describe how you could use a spirometer trace to measure the rate of oxygen uptake:

A

‐ measure , volume of oxygen used / decrease in volume in chamber ;
‐ find difference in height from one , peak / trough , to another ;
‐ measure time taken (to use this oxygen) ;
‐ divide (volume) by time taken ;

34
Q

Oxygen uptake

A

Volume of oxygen taken in from the air

35
Q

Describe the mechanism of ventilation in bony fish.

A
  1. Bony fish are very metabolically active and have a small SA:V ratio
  2. Ram ventilation
  3. Buccal-opercular pump
36
Q

What is ram ventilation?

A

‐ When fish are swimming they can keep water flowing over their gills, simply by opening their mouth and operculum.
‐ More primitive cartilaginous fish (e.g. sharks and rays) often rely on continual movement to ventilate their gills
- Ventilation of the gills is a continuous process, which ensures that water is constantly flowing over the gills (allowing maximum gas exchange)

37
Q

Describe the buccal-opercular pump

A

‐ Mouth opened and floor of the buccal cavity is lowered ;
‐ Volume of the buccal cavity increases / pressure decreases ;
‐ Water moves in to the buccal cavity ;
‐ The opercular cavity expands ;
‐ Volume of the opercular cavity increases / pressure decreases ;
‐ Water starts to move over the gills ; (needed for gas exchange)
‐ Mouth is closed and floor of the buccal cavity is raised ;
‐ More water moved from the buccal cavity into the opercular cavity ;
‐ Water forced over the gills and out via the opercular valve

38
Q

Describe gas exchange in bony fish

A
  • Water containing oxygen enters the fish through its mouth and passes out from the gills
    ‐ Each gill is composed of many filaments (primary lamellae) which provide thin layers and a large surface area (to maximise diffusion / gas exchange)
    ‐ The tips of the gill filaments overlap, increasing the resistance to the flow of water. This slows down the flow over the gills (increasing the time for gas exchange)
    ‐ The lamellae contain capillaries, providing a good blood supply (maintaining a steep concentration gradient for diffusion/short diffusion distance)
    ‐ The blood in the capillaries flows in a different direction to the flow of water over the gills (known as countercurrent exchange) to maximise diffusion / gas exchange.
39
Q

Draw an image of what is beneath the operculum of a fish.

A

See notes

40
Q

What is countercurrent exchange?

A

‐ In countercurrent exchange, the water moving over the gills & the blood in capillaries flow in opposite directions.
‐ This ensures that steep concentration gradients are maintained (i.e. equilibrium is not reached at any point of the exchange surface).
‐ This system allows bony fish to achieve much higher levels of blood oxygen saturation than cartilaginous fish (with parallel systems, where equilibrium is reached).

41
Q

What is the function of the gill plates?

A

Increase surface area

42
Q

Discuss spiracles

A

‐ Along the thorax and abdomen are small openings called spiracles.
‐ These openings are where air enters and exits the body, but also where water is lost.
‐ The insect needs to minimise water loss and maximise gas exchange, so many insects can open or close their spiracles with sphincters / valves.
‐ The spiracles will be closed when the insect is inactive and the oxygen requirement is low. They are opened if carbon dioxide builds up or the oxygen requirement is raised.

43
Q

Why do insects need a gas exchange system?

A

High oxygen requirements

Have a hard chitinous exoskeleton that does not allow gas exchange

44
Q

Describe the tracheal system

A

‐ The tracheae lead away from the spiracles and branch into tracheoles.
‐ Due to the rings of chitin (structural support) the tracheae are relatively impermeable to gases – little gas exchange takes place.
‐ Tracheoles are elongated single cells with no chitin and are freely permeable to gases. They are very small and run between individual cells in the tissues of the insect.
‐ This is where the majority of gas exchange takes place. Air moves through the tracheae and tracheoles by diffusion, and eventually reaches all of the tissues.
‐ Oxygen dissolves in the moist walls of the tracheoles and diffuses into the surrounding cells. The close proximity of the tracheoles and the cells allows for efficient diffusion.

45
Q

Describe the tracheal fluid

A

‐ Tracheal fluid present towards the end of each tracheole (limits penetration of air / gas exchange) ;
‐ When oxygen demand increases / lactic acid synthesis increases (e.g. during flight) water moves out of the
tracheoles by osmosis ;
‐ This exposes a greater surface area for gas exchange ; (increasing oxygen delivery to respiring tissues)

46
Q

Discuss ventilation in insects

A

‐ Air actively pumped into the system by muscular movements ;
‐ Volume & pressure of thorax / abdomen changed by muscle movement ;
‐ Air drawn in / forced out as the pressure changes ;

Biology (11 decks)

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