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Biology A Level > Exchange Surfaces and Breathing > Flashcards

Exchange Surfaces and Breathing Flashcards

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1
Q

What are the features of a good exchange system?

A
  • A thin barrier to reduce diffusion distance
  • A large surface area to provide a larger space for molecules to pass through
  • A good blood supply, this enables fresh molecules to be brought to the supply side and maintain a steep concentration gradient of the molecules that the cells require, so the diffusion can occur rapidly
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2
Q

Explain how air passes into the lungs?

A

Air enters through the nose or the mouth, along the trachea, bronchi and bronchioles, the air then reaches tiny air-filled sacs in the lungs called alveoli, this is where gaseous exchange takes place

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3
Q

How does oxygen diffuse into the blood?

A

Air arrives at the alveoli and oxygen from the air in the alveoli diffuses into the blood in the capillaries, this is why each alveoli is in close contact with capillaries

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4
Q

How does carbon dioxide leave the blood?

A

Carbon dioxide from the blood diffuses into the air in the alveoli from the capillaries where it is transported to the lungs to be exhaled

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5
Q

How do alveoli provide a large surface area for gaseous exchange?

A

The lungs have many alveoli that are very small but because they are so numerous, they provide a large surface area for the lungs, this makes the surface area of the lungs much greater than the surface area of the skin

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6
Q

What does the barrier of gaseous exchange consist of?

A

The endothelial cells of the capillary and the epithilial cells of the alveolus, the membranes of these cells are permeable to carbon dioxide and oxygen as CO2 and oxygen are small and non-polar

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7
Q

What adaptations does the mammalian gaseous exchange system have to maximise the rate of diffusion?

A
  • Alveolus wall is one cell thick (epithilial cell)
  • Capillary wall is one cell thick (endothelial cell)
  • Both walls consist of squamous cells (flattened/very thin cells)
  • Capillaries are narrow meaning red blood cells are squeezed against the capillary walls making them flow closer to the walls of the alveoli and reducing their rate of flow
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8
Q

How does a good blood supply maximise rate of diffusion?

A
  • Carbon dioxide diffuses into the blood from the tissues, the blood transport CO2 to the lungs where it is exhaled, this ensures there is always a steep concentration gradient of CO2 from the blood to the alveoli
  • When oxygen diffuses into the blood, the oxygenated blood flows away from the lungs to the tissues and is replaced by deoxygenated blood this ensures there is always a steep concentration gradient from the blood to the lungs
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9
Q

How does ventilation of the lungs maintain the steep concentration gradient of CO2 and oxygen?

A

Used air is replaced with fresh air, this brings in oxygen ad gets rid of CO2. Therefore the concentration of O2 in the alveoli is always higher than that in the blood and the concentration of CO2 is always lower in the alveoli than that in the blood

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10
Q

Describe the process of inspiration

A
  • Diaphragm contracts to move down and become flatter, this displaces the digestive organs
  • External intercostal muscles contract to raise the ribcage
  • Volume of chest cavity increases, pressure in the lungs decreases below atmospheric pressure
  • Air moves into the lungs down the pressure gradient
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11
Q

Describe the process of expiration

A
  • Diaphragm relaxes and is pushed up by the displaced organs beneath it
  • External intercostal muscle relax and the ribs fall, the internal intercostal muscles contract to push out air more forcefully
  • The volume of chest cavity decreases and pressure in the lungs increases above atmospheric pressure
  • This causes air to move out down its pressure gradient
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12
Q

What do the alveoli contain to enable the to help contain and push out air during breathing?

A

Elastic fibres that stretch during inspiration to allow the alveoli to hold more air, the elastic fibres then recoil to push out air during expiration

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13
Q

What are the requirements of the trachea, bronchi and bronchioles to allow the passage of air into and out of the lungs?

A
  • Be large enough to allow sufficient airflow without causing obstruction
  • Be supported to prevent collapse when the pressure inside the lungs is low during inspiration
  • Be flexible to allow movement
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14
Q

What is the difference in structure between the trachea and bronchi?

A

The trachea and bronchi have similar structure but the bronchi has thinner walls than the trachea

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15
Q

How is the trachea supported?

A

The trachea has C-shaped cartilage rings that prevent collapse during inspiration , the rings being C-shaped allows flexibility and space for food to pas through the oesophagus

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16
Q

How are the bronchi supported?

A

Bronchi are supported by cartilage

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17
Q

What are the airways lined with to keep the lungs healthy?

A

Ciliated epithelium and goblet cells that secrete mucus. the cilia sweep this mucus to the top of the airways where it is swallowed

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18
Q

Apart from goblet cells, what other cells produce mucus in the airways?

A

The glandular tissue cells

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19
Q

What is the function of smooth muscle in the airways?

A

Smooth muscle can contract to make the lumen of the airway narrower, which reduces the flow of air to and from the alveoli. This may happen as a result of an allergic reaction

20
Q

How does the smooth muscle reverse their contraction?

A

The smooth muscle has to be elongated again by elastic fibres, this cause the smooth muscle to relax and this causes the elastic fibres to recoil to their original shape and size which dilates the airway

21
Q

What happens to the elastic fibres in the airway when the smooth muscle contracts?

A

They are deformed

22
Q

Describe the structure of the bronchioles

A

The bronchioles are much narrower than the bronchi, large bronchioles may have some cartilage but they’re mainly made up of smooth muscle and elastic fibres

23
Q

What do the smallest bronchioles end in?

A

Clusters of alveoli

24
Q

How can lung volumes be measured?

A

Using a spirometer

25
Q

How are lung volumes recorded using a spirometer?

A

The floating chamber lid is connected to a pen that is resting against a data logger, as the subject breathes in and out, the floating chamber lid moves up wards and downwards and this is recorded by the pen on the data logger

26
Q

What precautions should be taken when using a spirometer?

A
  • The soda lime should be functioning and fresh
  • The subject should be healthy and not have asthma
  • There should be no leaks in the apparatus as this would give inaccurate results
  • The mouthpiece should be sterilised
  • Water chamber must not be overfilled as water would get into the air tubes
27
Q

What is the vital capacity of the lungs?

A

The maximum volume of air that can be moved by the lungs in one breath, vital capacity is usually in the region of 2.5-5dm3

28
Q

What is the residual volume of the lungs?

A

The volume of air that remains in the lungs even after forced expiration, this air remains in the airways and the alveoli, the residual volume is approximately 1.5dm3 for most people

29
Q

What is the tidal volume of the lungs?

A

The volume of air that is moved in and out within each breath, this is usually around 0.5dm3

30
Q

What is the total lung capacity?

A

Vital capacity + residual volume

31
Q

What is the function of the soda lime in the spirometer?

A

To absorb carbon dioxide produced in respiration and exhaled by the subject

32
Q

How do we calculate the rate of oxygen uptake using a spirometer?

A
  • We can assume that the volume of CO2 absorbed by the soda lime is equal to the volume of O2 absorbed by the blood
  • Therefore the volume of air in the floating chamber will decrease over time
  • The volume of decrease can be measured on the spirometer graph by measuring the volume of air in the chamber after breathing in first and the volume of air after breathing in last and measuring the distance and dividing this by the time the person was breathing into the spirometer
  • The unit is dm3s-1
33
Q

How can breathing rate be measured using a spirometer?

A

The amount of peaks per minute can be measured, the breathing rate at rest is usually around 12-14 breaths per minute

34
Q

Which factors will affect breathing rate?

A

Breathing rate and deeper breaths

35
Q

What is the operculum of the fish?

A

The bony plate that covers each pair of gills

36
Q

What are gill filaments?

A

Slender branches of tissue that makes up the gill, each gill consists of two rows of filaments, filaments may also be called primary lamellae

37
Q

What are gill plates?

A

Folds of the filament to increase surface area, they’re usually called secondary lamellae

38
Q

Where do the fish’s capillary run deoxygenated blood close to?

A

The secondary lamellae as this is where exchange takes place because surface area is greatest and therefore the rate of diffusion of oxygen into the blood is the fastest

39
Q

What is the buccal cavity of the fish?

A

The fish’s mouth

40
Q

Describe the process of the countercurrent flow

A
  • Blood flows along the gill arch and out along the filaments to the secondary lamellae, here the blood flow is flowing in the opposite direction to the water flowing over the lamellae
  • Blood and water flowing in opposite directions ensures that at any point along the capillary, oxygen is diffusing from the water into the blood, diffusion takes place at the secondary lamellae as they have a large surface area, therefore maximising the rate of oxygen diffusing into the blood
  • The countercurrent flow maximises the amount of oxygen that diffuses into the blood from the water
41
Q

How does ventilation work in fish?

A
  • The floor of the mouth moves downwards and water moves into the buccal cavity, this increases the pressure in the buccal cavity
  • The mouth closes and water is pushed though the gills
  • Movements of the operculum are coordinated with movements of the mouth
  • As water is pushed from the buccal cavity, the operculum moves outwards, reducing the pressure in the opercular cavity (the space under the operculum) this enables water to flow through the gills
42
Q

Do insects have an open or closed circulatory system?

A

An open circulatory system

43
Q

What are spiracles?

A

External pores that allows air into the trachea

44
Q

How does gaseous exchange occur in insects?

A
  • Gaseous exchange occurs between air in the tracheoles and the tissue fluid surrounding the insects cells
  • When the insect is resting, there is more tracheal fluid in the ends of the tracheoles
  • When the insect is active, the tracheal fluid is withdrawn and the tracheoles to increase the surface area for exchange between the air in the tracheoles and the tissue fluid
45
Q

How do insects ventilate their tracheal system?

A
  • Movement of the insects wings alter the volume of the thorax
  • As the volume of the thorax is increased, the pressure of the air inside the tracheal system decreases and air is pushed into the tracheal system from outside through the spiracles
  • As the volume of the thorax decreases, the pressure of the air inside the insect’s tracheal system drops and
46
Q

How do locusts ventilate their tracheal system?

A
  • Locusts can alter the volume of their abdomen by specialised breathing movements
  • As their abdomen expands, pressure in the tracheal system decreases and the spiracles at the front end of their body open to allow air to enter the tracheal system
  • As the abdomen reduces in volume, the pressure of the air inside the tracheal system increases and the spiracles at the rear end of the locust’s body open to allow air to leave the tracheal system
47
Q

What is the role of haemolymph in an insect?

A

Acts as the insects blood and tissue fluid

Biology A Level (21 decks)

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