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Biology > Module 3.1 - Exchange Surface And Breathing > Flashcards

Module 3.1 - Exchange Surface And Breathing Flashcards

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1
Q

What are the main factors that affect the need for a transport system?

A
  • Size
  • Surface area:volume ratio
  • Level of activity
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2
Q

How does the size of an organism affect its need for a exchange system?

A
  • Small organisms: (e.g. unicellular) cytoplasm is close to environment so simple diffusion will supply enough oxygen + nutrients to survive
  • Multicellular: several layers of cells, making longer diffusion pathway. Too slow for a sufficient supply to innermost cells
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3
Q

How does surface area to volume ratio affect the need for a exchange system?

A

-Higher SA:vol ratio means higher amount of cells exposed to environment so more diffusion across outer cells can take place

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4
Q

What size of organisms have a large surface area to volume ratio?

A

Smaller organisms (small SA and small volume, large SA compared to volume) so diffusion is enough to supply all cells with sufficient oxygen

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5
Q

What size organisms have a small surface area to volume ratio?

A 
Larger organisms (larger SA and larger volume)
As size increases, volume increases faster than SA so have a small SA compared to volume
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6
Q

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

A
  • More metabolic activity = more use of oxygen in aerobic respiration
  • Cells of active organisms need good supplies of nutrients and oxygen to supply energy for movement (and to remove wastes from aerobic respiration)
  • More energy needed for thermoregulation such as mammals
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7
Q

What features make a good exchange surface?

A
  • Large SA: more space for molecules to pass through. Achieved by foldings in walls + membranes involved e.g. root hair cells
  • Thin barrier: reduce diffusion distance. Must be permeable to substance being exchanged e.g. alveoli of lungs
  • Good blood supply: fresh supplies of molecules to one side (supply side) keeping conc high + removes molecules from demand side to keep conc low. Maintains steep conc gradient for rapid diffusion e.g. gills in fish
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8
Q

What are the alveoli?

A

Tiny folds of the lung epithelium to increase SA

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9
Q

What is the diaphragm?

A

A layer of muscle beneath the lungs

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10
Q

What are the intercostal muscles?

A

Muscles between the ribs. Contraction of the external intercostal muscles raises the rib cage

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11
Q

What is ventilation?

A

The refreshing of air in the lungs so that there’s a higher oxygen conc than in the blood and lower CO2 conc

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12
Q

What holds the ribs together?

A

Intercostal muscles

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13
Q

Where does gaseous exchange occur in animals?

A

In the lungs

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14
Q

How does gaseous exchange occur in the lungs of the alveoli?

A
  • In the alveoli
  • Oxygen inhaled into the lungs diffuses from alveoli to capillaries. Capillaries move the oxygen away to maintain low conc to keep a steep concentration gradient. Oxygen replenished in lungs through inhalation (ventilation)
  • CO2 exhaled from lungs to environment, maintaining low conc in alveoli. Capillaries keep high conc in blood to keep steep conc gradient, so CO2 continues to diffuse from capillaries to alveoli
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15
Q

How are alveoli adapted to their function?

A
  • Many of them to give the lungs a large SA
  • Barrier is permeable to O2 and CO2
  • Thin barrier to reduce diffusion distance
  • Good network of capillaries
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16
Q

How do the alveoli give the lungs a large SA?

A
  • Each alveolus has a diameter of 100-300μm
  • Lots of them to give the lungs a large surface area (larger than that of skin)
  • Total SA of exchange surface is about 70m^2
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17
Q

What is the role of the surfactant in the alveoli?

A

Reduces the cohesive forces between water molecules as these forces tend to make the alveoli collapse

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18
Q

How is the barrier in the exchange surface permeable to oxygen and carbon dioxide?

A

Barrier is the wall of the alveolus and the wall of the blood capillary. Plasma membrane allows diffusion of oxygen and carbon dioxide as the molecules are small and non polar

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19
Q

How is the barrier of the exchange surface of the lungs minimised?

A
  • Alveolus wall only one cell thick
  • Capillary wall only one cell thick
  • Both walls consist of squamous cells (flattened or very thin)
  • Capillaries are in close contact with alveolus walls
  • Capillaries are so narrow the RBCs squeezed against capillary wall, making them closer to the air in alveoli + reducing rate of flow (more resistance)
  • Total barrier only 2 flattened cells, less than 1μm thick
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20
Q

Explain the benefit of having a good network of capillaries at the exchange surface of the lungs.

A
  • Blood system transports CO2 from tissues to lungs, ensuring conc in blood is higher than alveoli so CO2 diffuses into alveoli
  • Blood transports O2 away from lungs so conc in blood is lower than alveoli so O2 diffuses into blood
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21
Q

What does ventilation ensure?

A
  • Conc of O2 in air of alveolus is higher than that of the blood
  • Conc of CO2 in alveoli is lower than that of the blood
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22
Q

What is the role of elastic fibres in the alveoli?

A

Stretch during inspiration then recoil to push air out during expiration

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23
Q

What do airways need to be in order to be effective?

A
  • Be large enough to allow sufficient air flow without obstruction
  • Be supported to prevent collapse when air pressure inside is low during expiration
  • Be flexible in order to allow movement
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24
Q

What precautions should be taken when using a spirometer?

A
  • Subject should be healthy, importantly not have asthma
  • Soda lime should be fresh + functioning
  • No air leaks in apparatus as this would give invalid or inaccurate results as air breathed in through leaks/pushed out and oxygen can be replenished from the environment
  • Mouthpiece should be sterilised
  • Water chamber must not be overfilled (or water may enter air tubes)
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25
Q

What factors affect vital capacity?

A
  • Size of person (particularly their height)
  • Age + gender
  • Level of regular exercise
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26
Q

What is the approximate residual volume?

A

1.5dm^3

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27
Q

What is the approximate tidal volume?

A

0.5dm^3

28
Q

How do you calculate oxygen uptake from a spirometer trace?

A
  • Measure the difference between 2 points on the x axis (will be a time, in secs)
  • Measure the difference in volume between these 2 points on the y axis (in dm^3)
  • Divide the volume by the timer taken to decrease
  • Unit: dm^3 s^-1
29
Q

How do you measure breathing rate from a spirometer trace?

A

Count the number of peaks in each minute (should be around 12-14)

30
Q

What causes an increase in oxygen uptake?

A

A higher demand of oxygen which causes increased breathing rate and deeper breaths

31
Q

Describe the structure of the exchange surface in bony fish.

A
  • Most have 5 pairs of gills, covered by a bony plate: operculum
  • Each gill has 2 rows of gill filaments (primary lamellae) attached to a bony arch (gill arch)
  • Filaments are very thin, + their surface is folded into many secondary lamellae (gill plates) providing a large SA
  • Good network of capillaries around the secondary lamellae
32
Q

Describe how to dissect a fish gill.

A
  1. Find the operculum (bony covering on each side of the fish’s head)
  2. Life operculum + observe gills, noting their colour
  3. Cut away one operculum to view the gills, noting gill slits or spaces between the gills
  4. Carefully cut out one gill, noting the bony support (gill arch) + soft gill filaments making up each gill.
33
Q

Describe the countercurrent flow at the exchange surface of bony fish.

A

Blood flows through capillaries in opposite direction to flow of water over lamellae, creating a countercurrent flow to absorb the maximum amount of oxygen from the water

34
Q

Describe the movement of blood in bony fish.

A
  • Heart
  • Gills: flows along gills arch + out along the filaments (primary lamellae) to the secondary lamellae (gill plates) through the capillaries (in opposite direction to flow of water)
  • Body: cells of respiring tissues
  • Heart
35
Q

Why do bony fish need to keep moving?

A

Maintain a high conc of oxygen outside the gills, as if they don’t would have the same water that they have extracted all the oxygen from

36
Q

(MA) Explain why larger organisms need transport systems and specialised surfaces for exchange.

A
  • Large organisms are more active + so have higher demands for oxygen
  • Have smaller SA:vol ratio meaning diffusion is too low
  • Diffusion distance is too great as many cells are deep in the body + not in contact with environment
  • Insufficient wast would be removed
37
Q

(MA) Describe inspiration.

A
  • Diaphragm contracts, flattens + moves downwards
  • External intercostal muscles contract, internal intercostal muscles relax + move the ribs up + out
  • Increases volume inside thorax + lungs
  • Reduces pressure in thorax + lungs below atmospheric pressure
  • Air moves into lungs down a pressure gradient
38
Q

(MA) Describe expiration.

A
  • Diaphragm relaxes + moves upwards
  • External intercostal muscles relax, internal intercostal muscles contract + ribs move down + in
  • Decreasing volume inside thorax + lungs
  • Increases pressure inside thorax + lungs above atmospheric pressure
  • Air moves out of the lungs down a pressure gradient
39
Q

(MA) What are the features of a good exchange surface.

A
  • Large SA: more space for molecules to pass through so more efficient
  • Thin barrier: short diffusion distance
  • Fresh supply of molecules on one side + removal on the other keeping conc gradient steep for quick diffusion
  • Permeable to exchange molecules e.g. has carrier proteins in plasma membrane
40
Q

(MA) How are the lungs efficient as an exchange surface?

A

-Large SA: millions of tiny alveoli gives large SA for O2 + CO2 to diffuse across
-Thin barrier, 2 cells thick
> Walls of alveoli 1 cell thick
> Walls of capillary 1 cell thick
> Walls of alveoli + capillaries are made from squamous epithelial cells
> Alveoli + capillaries in close contact
> Capillaries narrow so RBCs squeezed against wall so closer to air in alveoli + reducing the rate they flow past in the blood
-Permeable: plasma membranes of cells lining alveoli + capillaries are fully permeable to O2 + CO2

41
Q

(MA) What is the role of C shaped cartilage and where is it found?

A

-Keep airways open + prevent collapse during inspiration when there’s low pressure in thorax
(-Also allows some flexibility to move neck without constricting airways)
-Trachea + bronchi (not C shaped in bronchi)

42
Q

(MA) What is the role of the smooth muscle and where is it found?

A
  • Contracts to constrict airways
  • Reduces flow of air (reduces harmful substances going into lungs)
  • Trachea, bronchi, bronchioles
43
Q

(MA) What is the role of the elastic fibres in airways and where are they found in airways?

A
  • Stretch when smooth muscle contracts
  • Recoil (when smooth muscle relax) to help dilate airway again
  • Trachea, bronchi, bronchioles
44
Q

(MA) What is the role of goblet cells and where are they found?

A
  • Secrete mucus which traps bacteria + other particles to be removed from lungs to reduce infection
  • Trachea, bronchi and in larger bronchioles only
45
Q

(MA) What is the role of the ciliated epithelium and where is it found?

A
  • Waft to + fro to remove mucus from airways up to throat

- Trachea, bronchi, bronchioles

46
Q

(MA) What is the role of blood vessels int he respiratory system?

A

-Supply lung tissue e.g. smooth muscle, with oxygen for aerobic respiration

47
Q

(MA) What is the role of the elastic fibres in the alveoli?

A
  • Stretch during inhalation to increase lung volume + prevent alveoli from bursting
  • Recoil during exhalation to expel more air from the alveoli
48
Q

(MA) What is the role of then squamous epithelium in the alveoli?

A

-Alveoli walls one cell thick to provide a short diffusion distance for gaseous exchange

49
Q

(MA) What tissues are found in the trachea?

A
  • Cartilage (C shaped)
  • Ciliated epithelium
  • Goblet cells
  • Smooth muscle
  • Elastic fibres
50
Q

(MA) What tissues are found in bronchi?

A
  • Cartilage
  • Ciliated epithelium
  • Goblet cells
  • Smooth muscle
  • Elastic fibres
51
Q

(MA) What tissues are found in the bronchioles?

A
  • Ciliated epithelium
  • Goblet cells (only in larger ones)
  • Smooth muscle
  • Elastic fibres
52
Q

(MA) What tissues are found in the alveoli?

A
  • Elastic fibres

- Ciliated epithelium

53
Q

(MA) How do use the spirometer to measure the mean tidal volume?

A
  • Don’t breath through nose
  • Patient breathes normally
  • Measure height of waves (tidal volume) at least 3 waves from trace
  • Calculate mean (add volumes together + divide by number of breaths)
54
Q

(MA) Why does the volume of oxygen in the spirometer decrease over time?

A
  • When you exhale into the spirometer, the carbon dioxide is absorbed by the soda lime
  • Decreases volume of gas in spirometer + causes trace to gradually fall
  • Volume of carbon dioxide removed = volume of oxygen used by person
  • Can use this to measure rate of oxygen uptake
55
Q

Describe the role of surfactant in the alveoli of the lungs.

A
  • It’s a water film lining alveoli
  • Breath out: evaporates + leaves lungs
  • Cohesion between water molecules would cause alveoli to collapse
  • Compound (surfactant) produced in alveoli lines them
  • Reduces surface tension + cohesion + stops alveoli collapsing
56
Q

Why is there always a residual volume?

A
  • Lungs can’t be completely compressed
  • Trachea + bronchi held open by cartilage
  • Bronchioles + alveoli held open by elastic fibres
57
Q

Why does the total volume of gas recorded on a spirometer trace decrease over time?

A
  • Soda lime absorbs CO2 breathed out
  • Tells you how much CO2 breathed out so how much O2 taken in for aerobic respiration
  • Volume of CO2 removed = volume of O2 used by person therefore decrease measures oxygen uptake
58
Q

Why do fish have to keep swimming in order to survive?

A
  • Maintains concentration gradient

- Blood flows through capillaries in opposite direction to flow of water over lamellae creating a countercurrent flow

59
Q

What is the buccal cavity?

A

The mouth

60
Q

How do bony fish keep water flowing over their gills?

A

Buccal-opercular pump

61
Q

Describe ventilation in insects.

A
  • Don’t transport oxygen in blood (too slow)
  • Have air filled tracheal system supplying air directly to respiring tissues
  • Air enters via pores (spiracles)
  • Air transported into body through tracheae
  • Trachea divides into smaller tubes: tracheole
  • Ends of tracheoles filled with tracheal fluid
  • Gaseous exchange occurs between air in tracheole + tracheal fluid. Some exchange occurs across thin walls of tracheoles
62
Q

How do insects cope when they have a high level of activity?

A

-When tissues are active, tracheal fluid drawn into respiring cells increasing SA of tracheole exposed to air
-More oxygen can be absorbed
(-Fluid is present at rest to reduce water loss + dehydration of trachea)

63
Q

Why does tracheal fluid get drawn into cells during high levels of activity?

A

Build up of solutes in cells during activity lowers water potential + water moves by osmosis

64
Q

How does ventilation occur in large insects?

A
  • Movement of wings alters volume of thorax
  • When volume of thorax decreases, pressure in tracheal system increases + air is pushed out
  • When volume in thorax increases, pressure in tracheal system decreases + air moves in from outside
65
Q

Describe ventilation in bony fish.

A
  • Mouth opens (operculum is closed)
  • The buccal cavity floor is lowered
  • This increases volume + decreases pressure of buccal cavity compared to outside
  • Water rushes into mouth down a pressure gradient
  • Opercular cavity expands (lowering pressure)
  • Buccal cavity floor is raised (increasing pressure)
  • Pressure inside buccal cavity is now higher than opercular cavity
  • Water moves from buccal cavity over gills into opercular cavity
  • Mouth is now closed + operculum opens
  • Sides of opercular cavity move inwards, increasing pressure
  • Water rushes out of fish through operculum
66
Q

How does ventilation occur in locusts?

A
  • Alter volume of abdomen by specialised breathing movements
  • Coordinated with opening + closing valves of spiracles
  • As abdomen expands, spiracles at front end of body open + air enters tracheal system
  • As abdomen’s volume rescues, spiracles at rear end of body open + air can leave tracheal system

Biology (20 decks)

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