7 Exchange surfaces and breathing

Question 1

Describe the exchange in microscopic organisms

Answer 1

• microscopic organisms such as bacteria have a large SA:V ratio
• substances exchanged directly with their surrounding environment
• this is possible as substances have a short distance to travel

Question 2

Describe the exchange in organisms with greater size

Answer 2

• SA:V ratio decreases
• less surface area for the absorption of nutrients and gases
• greater volume results in a longer diffusion distance
• BMR increases and therefore demand for nutrients and gases increase
• simple diffusion through surface is not enough

Question 3

Describe the exchange in plants

Answer 3

• large organisms have specialised exchange surface
• thin cell walls
• large surface area to volume ratio
• increase rate of water uptake and mineral absorption

Question 4

What makes an effective exchange surface?

Answer 4

• large surface area
• short diffusion distance
• good blood supply
• ventilation mechanism (alveoli)

Question 5

Describe “alveoli”

Answer 5

• small air sacs
• gas exchange takes place
• made of thin, flattened epithelial cells
• contain collagen and elastic tissue for it to stretch and recoil
• exchange of oxygen and carbon dioxide occurs between the alveoli and the capillaries via passive diffusion
• made of 2 types of cells

Question 6

Structure of the lungs?

Answer 6

• trachea
• bronchi
• bronchioles
• alveoli
• parietal pleura
• visceral pleura
• pleural cavity
• diaphragm
• ribs
• intercostal muscles

Question 7

Describe “trachea”

Answer 7

• channel which allows gas to travel in and out
• contains rings of C-shaped cartilage

Question 8

Describe “cartilage”

Answer 8

• strong and flexible tissue
• rings ensure trachea to stay open under low pressure and allow it to move and flex

Question 9

Describe “goblet cells”

Answer 9

Mucus producing cells which traps dust, bacteria and other microorganisms

Question 10

Describe “cilia”

Answer 10

Waft the mucus upwards away from lungs

Question 11

Describe “bronchi”

Answer 11

• similar structure to the trachea but have thinner walls
• cartilage rings are also present but are a full circle

Question 12

Describe “bronchioles”

Answer 12

• each one varies in size and structure, getting smaller as they get closer to the alveoli
• larger bronchioles contain elastic fibres and smooth muscle
• smallest bronchioles do not have smooth muscle but they do have elastic fibres for stretching and recoiling

Question 13

Describe “smooth muscle”

Answer 13

• found throughout the walls of the bronchi and larger bronchioles
• helps to regulate the flow of air into the lungs
• dilated when more air is needed
• constrict when less air is needed

Question 14

Describe “elastic fibres”

Answer 14

• present in all lung tissue
• enable lungs to stretch and recoil
• recoil allows exhalation to be passive

Question 15

Describe “type 1 pneumocytes”

Answer 15

• line the alveolar surface
• squamous and extremely thin
• cover about 95% of alveolar surface
• involved in gas exchange

Question 16

Describe “type 2 pneumocytes”

Answer 16

• granular and roughly cuboidal
• cover about 5% of alveolar surface
• secrete alveolar/pulmonary surfactant which reduces surface tension, stops alveoli collapsing during expiration and dissolves oxygen for ease of diffusion

Question 17

Describe “squamous epithelium”

Answer 17

• a single thin layer of flattened cells with irregular boundaries
• forms the structure of the alveolar wall
• very thin and permeable for easy diffusion

Question 18

Describe “pleural membrane”

Answer 18

• parietal pleura lines inside of chest cavity
• visceral pleura lines the lungs

Question 19

Describe “pleural cavity”

Answer 19

• pleural fluid is a lubrication fluid in the pleural cavity
• reduces friction on the surface of the lungs

Question 20

Steps of inspiration?

Answer 20

1. External intercostal muscles between the ribs contract, moving them upwards and outwards
2. The diaphragm muscle below the lungs contracts and flattens
3. The thorax volume increases
4. Thorax pressure is reduced below atmospheric pressure
5. The outside air is drawn into the lungs

Question 21

Steps of expiration?

Answer 21

1. The external intercostal muscles relax
2. Ribs move inwards and downwards
3. The diaphragm relaxes and becomes dome shaped
4. The volume of thorax is reduced
5. The thorax pressure increases above atmospheric pressure
6. Air is forced outside the lungs

Question 22

Describe “measuring ventilation”

Answer 22

• measure lung function and investigating breathing
• changes in the amount of gas exchanged can happen normally due to physical activity or due to various diseases
• various instruments can be used to measure normal lung activity as well as diagnose lung disorders

Question 23

Describe “peak flow meter”

Answer 23

• simple measurement of how quickly you can blow air out of your lungs
• measuring how fast you’re able to breathe out
• your peak flow score can indicate whether your airways are narrowed

Question 24

Describe “vitalograph”

Answer 24

• used to measure the forced expiratory volume
• advanced version of a peak flow meter
• monitoring of lung function for respiratory conditions including chronic obstructive pulmonary disease (COPD), cystic fibrosis and post-transplant patient

Question 25

Describe “spirometer”

Answer 25

• used to measure different aspects of lung volume
• used to diagnose asthma, COPD and other conditions that affect breathing

Question 26

Define “tidal volume”

Answer 26

Volume of air which moves in and out of lungs with each resting breath

Question 27

Define “inspiratory reserve volume”

Answer 27

Maximum volume of air which can be breathed in

Question 28

Define “expiratory reserve volume”

Answer 28

Extra air which can be forced out of the lungs above normal tidal volume

Question 29

Define “vital capacity”

Answer 29

The maximum volume of air a person can expel from the lungs after a maximum inhalation

Question 30

Define “residual capacity”

Answer 30

Volume of air that remains in a person’s lungs after maximum exhalation

Question 31

Define “forced expiratory volume (FEV)”

Answer 31

Measures how much air a person can exhale upon a forced breath

Question 32

Define “breathing rate”

Answer 32

The number of breaths taken per minute

Question 33

Define “ventilation rate”

Answer 33

The total volume of air inhaled in one minute

Question 34

Describe “oxygen consumption”

Answer 34

• the volume of gas in the spirometer left at the end
• calculated by taking the average slope of the trace

Question 35

Describe “gills”

Answer 35

• organs for gas exchange in bony fish with series of gills on each side of head
• large SA:V with good blood supply
• each gill arch is attached to two stacks of filaments

Question 36

Describe “lamellae”

Answer 36

• microscopic
• full of capillaries
• increase the surface area of gills

Question 37

Describe “counter-current flow”

Answer 37

• blood flows through the gill plates in one direction
• water flows in the other direction
• maintains a large concentration gradient
• makes gas exchange more efficient

Question 38

Inspiration of bony fish?

Answer 38

1. Buccal cavity floor lowers
2. Mouth opens
3. Volume of buccal cavity increases
4. Pressure in buccal cavity decreases
5. Water flows into buccal cavity

Question 39

Expiration of bony fish?

Answer 39

1. Buccal cavity floor moves upwards
2. Mouth closes
3. Volume of buccal cavity decreases
4. Pressure of buccal cavity increases
5. Water flows through the gills and operculum opens due to pressure

Question 40

Describe the gas exchange in insects

Answer 40

• insects are metabolically active and have a high oxygen demand
• rigid exoskeleton made of chitin is impermeable to gases
• no blood present so gas exchange system (tracheal system) delivers oxygen directly to cells

Question 41

Describe “spiracles”

Answer 41

• small openings which line the abdomen or thorax of the insect
• contain sphincter valves which can open and close the spiracle
• dependent on oxygen demand and other factors

Question 42

Describe the insect respiratory system

Answer 42

• leading from the spiracle are trachea
• tracheae are tubes which lead to tracheoles
• rigid rings of chitin keep tracheae open

Question 43

Describe how tracheoles are related to gas exchange

Answer 43

• a large number of tracheoles run between cells and into muscle fibres
• site of gas exchange
• tracheoles are composed of a single elongated cell
• freely permeable to gases

Question 44

Describe “discontinuous gas exchange”

Answer 44

• closed spiracles recycle the oxygen in the tracheae which allows survival without constant breathing
• spiracles open and close rapidly during fluttering to replenish oxygen supplies
• spiracles open when CO₂ levels are very high to allow rapid removal of CO₂

Question 45

Describe “abdominal pumping”

Answer 45

• mechanical ventilation in insects
• larger insects can not rely solely on passive diffusion
• air is moved in to the tracheal system using muscular pumping movement of the thorax/abdomen
• movements change the volume of the body cavity therefore changes the pressure
• allows air to move in and out of

Question 46

Why can the trachea of an insect collapse or enlarge?

Answer 46

• used as a reservoir for some insects
• can be inflated or deflated depending on the need for oxygen

Question 47

Adaptations for gas exchange in insects?

Answer 47

• tracheoles have thin walls so short diffusion distance to cells
• highly branched so large surface area
• tracheae are able to fill with air maintains concentration gradient
• fluid in the end of tracheoles that moves out allows faster diffusion
• abdominal pumping moves air which maintains concentration gradient