exchange surfaces

Question 1

what is the need for specialised exchange surfaces

Answer 1

• multi celled organisms have a large diffusion distance between cells and environment
• surface area to volume ratio is too small in larger organisms

Question 2

what are the key features of specialised exchange surfaces

Answer 2

• large surface area
• thin cell wall
• good blood supply/ventilation to maintain a concentration gradient

Question 3

what are the key features of the mammalian gaseous exchange system

Answer 3

nasal cavity
trachea
bronchus
bronchioles
alveoli

Question 4

describe the ciliated epithelium that line most airways

Answer 4

• contain cilia to waft mucus to the mouth be swallowed
• contain goblet cells that produce and secrete viscous mucus that traps dust and microbes and will be destroyed by stomach acid when ingested

Question 5

describe the nasal cavity

Answer 5

-has good blood supply humidifying the air
-ciliated lining trapping dirt and bacteria
-moist surfaces increasing humidity of air and reducing evaporation

Question 6

describe the trachea

Answer 6

• divides into two primary bronchi
• C shaped rings of cartilage joined by connective tissue to keep airway open
• smooth muscle can contract/relax to constrict/dilate airways and change airflow
• elastic tissue contains elastic fibres w/ elastin to allow stretch+recoil
• line w/ ciliated epithelial cells + goblet cells

Question 7

describe the bronchi

Answer 7

• reinforced w/ cartilage (strong flexible tissue) to keep airway open
• smooth muscle to contract/relax to constrict/dilate airway + change airflow
• elastic tissue w/ elastic fibres w/ elastin to allow stretch + recoil
• line with ciliated epithelial cells and goblet cells

Question 8

describe the bronchioles

Answer 8

• no cartilage, can change shape
• smooth muscle to contract/relax to constrict/dilate airway + change airflow
• elastic tissue with elastic fibres w/ elastin to allow stretch + recoil
• lined with ciliated epithelial cells but usually don’t contain goblet cells

Question 9

what are the adaptations of the alveoli

Answer 9

-wall consists of 1 layer of squamous epithelium for rapid diffusion
-large SA to increase rate of gas exchange
-partially permeable
-elastic fibres for stretch+recoil
-collaged fibres to prevent bursting and overstretching
-inner fluid to facilitate diffusion
-surrounded by capillaries bringing blood close for diffusion

Question 10

explain the process of inhalation

Answer 10

• diaphragm contracts
• volume in chest+thorax increase
• lung+thorax pressure decreases
• external intercostal muscles contract, expanding rib cage up + out
• air moves down pressure gradient and rushes into lungs

Question 11

explain the process of exhalation

Answer 11

• diaphragm relaxes
• volume in chest+ thorax decreases
• lung+thorax pressure increases
• abdominal and internal intercostal muscles relax, ribcage drops down + in
• air is forced out the lungs

Question 12

what are the 4 ways breathing can be scientifically measured

Answer 12

tidal volume
vital capacity
breathing rate
oxygen uptake

Question 13

define tidal volume

Answer 13

volume of air breathed in/out during normal breathing ( at rest )

Question 14

define vital capacity

Answer 14

maximum volume of air that can be breathed in/out in one breath

Question 15

define breathing rate and give the calculation

Answer 15

number of breaths taken in one minute
60/time taken for one breath (bpm)

Question 16

what is the equation for ventilation rate

Answer 16

tidal volume X breathing rate (dm3min-1)

Question 17

what is the equation for estimate rate of oxygen uptake

Answer 17

volume used X 60/time (dm3min-1)

Question 18

what is inspiratory/expiratory reserve volume

Answer 18

maximum volume of air that can be inhaled/exhaled above a normal inhalation/exhalation

Question 19

what is residual volume

Answer 19

the volume of air that remains in the lungs after the largest possible exhalation

Question 20

how do you work out total lung capacity

Answer 20

vital capacity + residual volume

Question 21

explain how a spirometer works briefly

Answer 21

-subject wears nose clip and breathes through mouthpiece
-co2 is absorbed by soda lime for safety
-a trace on paper / digital graph is formed

Question 22

what are the key features of an insects gas exchange system

Answer 22

spiracles
trachae
tracheoles

Question 23

what is the exoskeleton in an insect

Answer 23

impermeable waxy coating to prevent water loss
-contain spiracles (holes) along abdomen and thorax allowing airflow into the tracheal system

Question 24

describe the trachae

Answer 24

• air filled tubes branching through the body leading to tracheoles
• have rigid rings of chitin keeping them open and preventing collapse ( + strength )
• multiple trachae increase surface area

Question 25

describe the tracheoles

Answer 25

- smaller branches of trachae one cell thick that deliver gases directly to cells and tissues ( reduces gas diffusion distance ) - highly branches increasing SA - tracheal fluid at the ends for gases to dissolve in

Question 26

how do insects get oxygen when they are at rest and not active

Answer 26

- at rest, diffusion provides enough oxygen to cells so spiracles close to prevent water loss

Question 27

why do insects need gas exchange

Answer 27

- deliver oxygen to cells for aerobic respiration and energy for metabolic reactions - to remove carbon dioxide from cells as it's a waste product reducing pH which can denature enzymes

Question 28

explain inspiration and expiration in insects

Answer 28

- when inhaling, elastic tissue of thorax and abdomen relax altering volume and pressure - when exhaling, muscles contract and flatten body, decreasing volume of tracheal system, air is forced out -during flight some tracheal fluid is removed and put into respiring muscle, reducing diffusion distance

Question 29

why is gas exchange more complex in fish

Answer 29

- water is more dense than air so diffusion is slower - water has less oxygen ( 30x ) than air - fish are active so have high oxygen demands

Question 30

describe the structure of gills

Answer 30

- gills covered by an operculum flap - gills have stacked filaments with gill lamellae at a 90* angle to filaments - gill lamellae are surround a network of capillaries

Question 31

adaptations of the gills for efficient gas exchange

Answer 31

- lamellae membranes are very thin, so short diffusion distance - lots of lamellae provide a large surface area - gills have rich bloody supply maintaining a concentration gradient

Question 32

explain the counter-current flow system in fish

Answer 32

- blood and water flow over lamellae in opposite directions - maintains a steep concentration gradient across the entire lamellae - doesn't reach equilibrium like in concurrent flow

Question 33

explain ventilation in bony fish via the buccal cavity ( mouth and throat area )

Answer 33

- fish open mouth, lowering buccal cavity floor, increasing volume and decreasing pressure and water flows in - fish raises buccal cavity floor, closing mouth increasing pressure by lowering volume moving water into the gill cavity ( lower pressure ) and eventually pressure builds up and operculum is forced open , water exits - operculum pulled shut when buccal floor lowered