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Biology > 3.1 - Exchange Surfaces and Breathing > Flashcards

3.1 - Exchange Surfaces and Breathing Flashcards

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1
Q

comment on the need for lungs in humans

A

Skin surface area to volume ratio is not large enough, could not supply all oxygen required; lung surface area to
volume ratio is much larger, large enough to supply sufficient oxygen.

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2
Q

explain why plants need a large SA for absorption from roots

A

Roots absorb water from soil by osmosis; also need to absorb mineral ions, by active transport.

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3
Q

explain the importance of maintaining a steep concentration

A

Steep concentration gradient means that absorption can be by diffusion, no metabolic energy needed (ATP)

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4
Q

describe how a steep concentration gradient in oxygen conc. is maintained across the alveolus wall?

A

On supply side (in alveolus), the air is continually replaced by ventilation movements, keeping oxygen
concentration high; on the demand side (in blood), the oxygen is carried away by the flow of blood, keeping the concentration low

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5
Q

describe how a steep concentration gradient in CO2 conc. is maintained across the alveolus wall?

A

On supply side (in blood ), carbon dioxide is brought from the cells by the blood flow, keeping the concentration high; on the demand side (the alveoli), the air in the alveoli is continually replaced by ventilation movements, keeping concentration low.

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6
Q

describe what physiological change takes place and why during exercise?

A

the volume of air breathed in and out increases, the concentration gradient increases, rate increases, muscles respire more

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7
Q

Why can diffusion alone supply the needs of single celled organisms?

A
  • the metabolic activity is relatively low, so oxygen demands and co2 production are low.
  • sa:v ratio is large
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8
Q

Why is diffusion not enough for larger organisms?

A

They have high metabolic activity.

  • oxygen demands are high and lots of co2 is produced.
  • diffusion is in effective as distance between cells is too far.
  • the bigger the organism the smaller the sa:v ratio so gases can’t be exchanged fast enough to survive.
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9
Q

What are the features of effective exchange surfaces?

A
  1. Increased surface area- provides space needed for exchange and overcomes limitation of sa:v ratio in larger organisms.
  2. Thin layers- distances for diffusion are short, so process is faster.
  3. Good blood supply- maintains a steep concentration gradient by ensuring substances are continuously delivered to and removed from the exchange surface.
  4. ventilation- also helps maintain steep concentration gradient, making process more efficient.
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10
Q

What is the need for the human gaseous exchange system?

A
  1. High metabolic rate due to being very active and having to maintain body temperature. There is therefore a greater demand for oxygen and the removal of co2.
  2. Due to the small SA:V ratio and very large volume of cells.
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11
Q

What are the 5 key structures of the human gaseous exchange system?

A
  1. Nasal cavity.
  2. Trachea.
  3. Bronchus.
  4. Bronchioles.
  5. Alveoli.
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12
Q

Nasal cavity.

A
  1. large surface area with good blood supply- warms incoming air to body temperature.
  2. Hairy lining- secretes mucus to trap dust/bacteria, protecting irritation and infection.
  3. Moist surfaces- increase humidity of incoming air, reducing evaporation from exchange surfaces.
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13
Q

Trachea.

A

The trachea is the main airway carrying clean, warm and moist air from the nose down into chest.

  • wide tube supported by C shaped incomplete rings of strong, flexible cartilage which stop it from collapsing.
  • rings are incomplete to allow space for oesophagus.
  • lined with ciliated epithelium, with goblet cells between and below the epithelial cells.
  • goblet cells secrete mucus onto its lining, cilia brush mucus away into the throat. It is then swallowed and digested.
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14
Q

Bronchus

A

In the chest cavity, the trachea divides to for, the left and right bronchus.
Have a similar structure to trachea:
- the same supporting rings of cartilage, however, they are much smaller.

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15
Q

Bronchioles.

A

In the lungs, the bronchi divide to form many small bronchioles.
- they have no cartilage rings.
- walls contain smooth muscle.
- smooth muscle contract= bronchioles constrict.
smooth muscle relaxes= bronchioles dilate.
- this changes the amount of air entering the lungs.
- lined with thin layer of flattened epithelium, making some gaseous exchange possible.

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16
Q

Alveoli.

A

The alveoli are tiny air sacs, which are the main gas exchange surfaces in the body.

  • diameter of 200-300um.
  • consists of layer of thin flattened epithelial cells, along with some collagen and elastic fibres( made from elastin).
  • elastic tissues allow alveoli to stretch as air is drawn in. When they return to resting size, they help squeeze air out. = known as elastic recoil of the lungs.
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17
Q

What are the main adaptations of the alveoli for effective gas exchange?

A
  1. Large SA- there are 300-500 million alveoli per adult lung. Provides space needed for oxygen to diffuse.
  2. Thin layers- alveoli and the capillaries surrounding them are one cell thick. Short diffusion distance.
  3. Good blood supply- constant flow of blood through capillaries maintains steep conc gradient = faster diffusion.
  4. Good ventilation- breathing moves air in and out maintaining steep conc gradient.
  5. Inner surface covered in thin layer of solution os salt, water and lung surfactant.
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18
Q

What is the role of the solution on the inner surface of the alveoli?

A
  • lung surfactant makes it possible for alveoli to remain inflated. It does this by reducing surface tension.
  • oxygen dissolves in the water before diffusing as diffusion can only occur once the gases are dissolved.
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19
Q

What features play a role in ventilating the lungs?

A
  • air is moved in/out due to pressure changes in the thorax (chest cavity).
  • thorax is lined by the pleural membranes which surround the lungs.
    space between them (pleural cavity) filled with thin layer of lubricating fluid so membranes easily slide over each other during breathing.
  • rib cage provides semi-rigid case within which pressure can be lowered.
  • diaphragm is a broad, domed sheet of muscle which forms the floor of the thorax.
  • external/internal intercostal muscles are found between the ribs.
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20
Q

Explain what happens during inspiration.

A

An energy using process.

  • diaphragm contracts, flattens and lowers.
  • external intercostal muscles contract, moving ribs upwards and outwards.
  • volume of thorax increases so pressure in thorax is reduced.
  • pressure is lower than pressure of atmospheric air, so air is drawn into the lungs to equalise the pressures.
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21
Q

Explain what happens during expiration.

A

Passive process.

  • diaphragm relaxes, moves up into resting dome shape.
  • external intercostal muscles relax, ribs move down and inwards.
  • elastic fibres in alveoli return to their normal length.
  • pressure in thorax increases as volume has increased.
  • pressure is greater than atmospheric pressure so air moves out until equilibrium is reached.
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22
Q

What is a peak flow meter?

A

A simple device that measures the rate at which air can be expelled from the lungs. People with asthma often use this to measure how well their lungs are working.

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23
Q

What are vitalographs?

A

More sophisticated version of peak flow meter.

  • patient breathes out as fast as they can through mouthpiece.
  • instrument produces graph of amount and speed of air breathed out.
  • this volume= forced expiratory volume in 1 second.
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24
Q

What is a spirometer?

A

Can be used to measure the volumes of gas breathed in and out under different conditions.

  • commonly used to measure different aspects of the lung volume/ breathing patterns.
  • many different forms of spirometer but all follow a common principle.
25
Q

What is tidal volume?

A

vol of air that moves into and out of the lungs with each resting breath.

26
Q

What is residual volume?

A

vol of air left in the lungs after exhaling as hard as possible.

27
Q

What is vital capacity?

A

vol of air that can be exhaled when the deepest possible intake of breath is followed by the strongest possible exhalation.

28
Q

What is total lung capacity?

A

sum of vital and residual volume

29
Q

What is inspiratory reserve volume?

A

maximum vol of air you can breath in over and above a normal inhalation.

30
Q

What is expiratory reserve volume?

A

extra vol of air you can force out of your lungs over and above the normal tidal volume of air you breathe out.

31
Q

What is breathing rate?

A

Breathing rate= number of breaths taken per minute.

32
Q

what is ventilation rate?

A

Ventilation rate= total volume of air inhaled in one minute.

Ventilation rate= tidal volume x breathing rate per min

33
Q

What happens when oxygen demands increase (mammals) (ventilation-wise)?

A

When they increase, for example during exercise, the tidal volume can increase from 15% to as much as 50% of the vital capacity.

  • breathing rate can also increase.
  • this results in increased ventilation of the lungs and therefore increased oxygen uptake.
34
Q

Why has the insect gas exchange system adapted to the way that it is?

A
  • insects are very active mainly land-dwelling animals with relatively high oxygen requirements.
  • however they have a tough, impermeable exoskeleton through which little or no gaseous exchange can take place.
  • they also don’t have blood pigments that can carry oxygen.
    Their gaseous exchange system has developed to deliver oxygen directly to the cells and remove carbon dioxide in the same way.
35
Q

When air is breathed in by mammals, what is the order of structures it passes through?

A

Nasal cavity - pharynx- larynx- trachea - bronchus - bronchioles- alveoli.

36
Q

What are spiracles and their role (insects)?

A

Small openings found along the thorax and abdomen of most insects.
- air enters and leaves the system through the spiracles, but water is also lost.

37
Q

How is water loss in insects from the spiracles minimised?

A

The spiracles can be open or closed by SPHINCTERS.
-when an insect is inactive and oxygen demands are low, the spiracles will all be closed most of the time.
- when oxygen demand is raised or carbon dioxide levels build up, more spiracles are opened.
This maximises the efficiency of exchange and minimises water loss.

38
Q

What are the tracheae and their role in insects?

A

The largest tubes of the insect respiratory system and lead away from the spiracles

  • they run into and along the body of the insect, carrying air.
  • the tubes are lined with spirals of chitin (a fibrous polysaccharide), which keeps them open if they are bent/pressed.
  • chitin is relatively impermeable to gases so little gas exchange takes place in the trachea.
39
Q

What are the tracheoles and their role in insects?

A

The tracheae branch to form narrower tubes called the tracheoles.

  • each tracheole is a single, greatly elongated cell (squamous epithelium) with no chitin lining so are permeable to gases.
  • they spread throughout the tissues of the insect and this is where most gaseous exchange takes place.
  • vast numbers of tracheoles provides large SA.
  • oxygen dissolves in moisture on the walls and diffuses into surrounding cells.
40
Q

What is tracheal fluid and its role in insects?

A

A fluid towards the end of the tracheoles which limits the penetration of air for diffusion.

  • however when oxygen demands rise (eg. During flight) a lactic acid build-up in the tissues results in water moving out of the tracheoles by osmosis due to a water potential gradient.
  • this exposes more SA for gaseous exchange.
41
Q

What alternative methods do insects with very high energy demands have to increase gaseous exchange?

A
  1. Mechanical ventilation- air is actively pumped into the system by muscular pumping movements of the thorax and abdomen. These movements change the volume or the body which changes the pressure in the tracheae and tracheoles. (As volume decreases, pressure increases, vice versa).
  2. Collapsible air sacs- act as air reservoirs. Usually inflated/deflated by the ventilating movements of the thorax and flight muslces and are used to increase the amount of air moving through the system.
  3. Withdraw tracheal fluid into the body- increase the surface area of tracheole wall exposed to air
42
Q

When air is breathed in by insects, what is the order of structures it passes through?

A

Spiracles- tracheae- tracheoles

43
Q

What are the difficulties bony fish need to overcome?

A
  • water is alot more dense and viscous (thick) than air.
  • water has a much lower oxygen content.
  • it would use up far too much energy to move the dense, viscous water in and out of lung-like respiratory organs.
    Moving water in one direction is much better in energy and simplicity terms.
44
Q

Why do fish need an exchange system?

A

Bony fish such as trout and cod are relatively big, active animals.

  • this means their cells have a high oxygen demand.
  • their high SA:V ratio means diffusion alone is not enough to supply their cells with the oxygen needed.
  • their scaly outer covering does not allow gaseous exchange.
45
Q

What are the gills and their function?

A
  • the organs of gaseous exchange.
  • fish maintain a flow of water in one direction over the gills.
  • gills have a large SA, good blood supply and thin layers for effective gas exchange.
  • in bony fish they are contained in a gill cavity.
46
Q

what does the bony gill arch do?

A
  • bony gill arch supports the structure of the gills.
47
Q

Operculum and its role?

A
  • a protective bony flap that covers the gills.

- it is active in maintaining a flow of water over the gills and so opens and closes accordingly.

48
Q

Gill filaments.

A
  • occur in large stacks called gill plates.
  • need a flow of water to keep them apart, exposing the large SA needed for gaseous exchange.
  • when in air they remain clumped together, with reduced SA but fan out once in water.
49
Q

Gill lamellae?

A
  • folds that cover the gills.
  • are the exact place gas exchange occurs.
  • they have a rich blood supply with a maintained steep concentration gradient.
  • large SA.
  • thin layers.
50
Q

What is the role of the efferent blood vessel in fish?

A

-Efferent blood vessel carries the blood leaving the gills in the opposite direction to incoming water which maintains a steep concentration gradient.

51
Q

Role of afferent blood vessels in fish?

A
  • Afferent blood vessel brings blood into the system. Haemoglobin is used to carry oxygen.
52
Q

why do fish die when placed out in the air?

A

gill filaments stick together, SA for exchange reduced, fish die from lack of oxygen

53
Q

describe ventilation in cartilaginous fish?

A
  • cartilaginous fish (sharks/rays) rely on continual MOVEMENT to ventilate the gills hence why they DONT STAY STILL.
    Buccal pump and operculum flap pump water over gills.
    This is RAM VENTILATION: they just ram water past the gills.
54
Q

describe ventilation in bony fish?

A
  • bony fish don’t rely on movement-generated water flow over the gills. Their exchange system allows them to move water over the gills even when still due to the operculum. They constantly OPEN AND CLOSE their mouths to cause changes in pressure
55
Q

Explain how ventilation of the gills takes place.

A
  1. mouth opened. Floor of buccal cavity lowered.
  2. This increases volume of buccal cavity= decreased pressure so water moves into mouth to create equilibrium.
  3. Opercular valve is shut, opercular cavity containing gills expands.
  4. This lowers pressure in opercular cavity, floor of buccal cavity moves up increasing pressure so water moves from buccal c over the gills.
  5. Mouth closes. Operculum opens. Sides of opercular cavity moves inwards.
  6. This increases pressure in opercular cavity, forcing water over gills and out through operculum.
  7. Floor of buccal cavity moves up, maintaining flow of water over gills.
    This is a continuous process.
56
Q

What are the 2 extra adaptions gills have for effective exchange?

A
  1. Tips of adjacent gill filaments overlap. This increases resistance to flow of water over the gill surfaces and slows down water movement, allowing more time for gaseous exchange.
  2. Countercurrent system: water and blood flow in different directions. This ensures that steep concentration gradients are maintained allowing more efficient gas exchange.
57
Q

Compare the countercurrent and parallel system.

A
  1. Parallel:
    - blood and water flow in same direction, providing an initial steep conc gradient. Diffusion takes place until there is conc equilibrium. Then no net movement of oxygen into blood occurs.
    This allows cartilaginous fish to only extract 50% of oxygen from the water.
  2. Countercurrent:
    - flow in opposite directions so steep gradient between water and blood is maintained along the gill. Oxygen continues to diffuse down the conc gradient so much higher levels of oxygen saturation in blood achieved.
    This allows bony fish to remove 80% of oxygen from the water flowing over them.
58
Q

describe why the trachea would collapse without the C shaped cartilage

A

during inhalation, the pressure in the gaseous exchange system drops below atmospheric pressure

59
Q

explain how and why smoking leads to increased infection?

A

paralyses the cilia, mucus accumulates in lungs, ideal conditions to reproduce

Biology (25 decks)

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