Exchange Surfaces

Question 1

why do multicellular organisms require specialised gas exchange systems

Answer 1

small surface area:volume means distance that needs to be crossed is larger
substances cannot easily enter cells

Question 2

name three features of an efficient gas exchange system

Answer 2

1. large surface area:volume
2. short diffusion distance
3. good blood supply

Question 3

describe the trachea and its function in the mammalian gas exchange system

Answer 3

wide tube supported by c shaped cartilage rings to stop it collapsing during pressure change
lined by ciliated epitheliul cells which move mucus towards throat to be swallowed preventing infection

Question 4

describe the bronchi and function in mammalian gas exchange

Answer 4

supported by rings of cartilage and lined by ciliated epithelium cells and goblet cells
narrow and allow air into bronchioles

Question 5

describe bronchioles and function in mammalian gas exchange

Answer 5

mostly only smooth muscle and elastic fibres so that they can contract and relax easily during ventilation

Question 6

describe alveoli and function in mammalian gas exchange

Answer 6

mini air sacs lined with epithelium cells
walls only one cell thick covered with network of capillaries
site of gas exchange

Question 7

explain process of inspiration

Answer 7

external intercostal muscles relax
ribs pulled up and out
diaphragm contracts and flattens
volume of thorax increases
air pressure outside lungs is higher than inside so air moves in

Question 8

explain the process of expiration

Answer 8

external intercostal muscles contract
ribs move down and in
diaphragm relaxes and domes
volume of thorax decreases
air pressure outside lungs is lower than inside so air moves out

Question 9

explain how a spirometer works

Answer 9

used to measure lung volume
breathe into air tight chamber which leaves trace on graph showing volume of breaths

Question 10

define vital capacity

Answer 10

maximum volume of air that can be inspired or expired in one breath

Question 11

define tidal volume

Answer 11

amount breathed in and out in one normal breath

Question 12

define breathing rate

Answer 12

number of breaths per minute

Question 13

describe two main features of a fish gas exchange system

Answer 13

gills
supported by arches with multiple projections of gill filaments stacked up in piles
lamellae
right angles to gill filaments giving increased surface area
blood and water flow across them in opposite directions

Question 14

explain the process of gas exchange in fish

Answer 14

buccal cavity volume increases to enable water to flow in
water pumped over lamellae by operculum and oxygen diffuses into blood
waste CO2 diffuses into water and flows back out gills

Question 15

how does counter current system maximise oxygen absorbed

Answer 15

maintains a steep concentration gradient as water is always next to blood of lower oxygen concentration keeps rate of diffusion constant

Question 16

describe three main features of insect’s gas exchange system

Answer 16

spiracles
holes on surface body opened or closed by valve for exchange
tracheae
large tubes extending through body tissues
supported by rings to stop collapsing tracheoles
smaller branches dividing off trachea

Question 17

explain process of gas exchange in insects

Answer 17

gases move in and out of tracheae through spiracles
diffusion gradient allows oxygen to diffuse into body tissue while CO2 diffuses out
contraction of muscle in thorax allows movement of air in and out

Question 18

compare and contrast mechanisms of expiration for normal and forced expiration

Answer 18

normal
-passive
-disaphragm relaxes and domes
-external intercostals relax
-ribs move down and in
-volume of thorax reduced causing pressure to increase
-pressure in thorax greater so air moves out

forced
-active so requires energy
-external intercostal muscles relax
-ribs pulled down hard
-abdominal muscles contract forcing diaphragm up

Question 19

outline how repiratory systems in fish and insects are adapted to maximise ventilation and gas exchange

Answer 19

insect gas exchange
-series of branched tracheoles increase surface area
-has short diffusion distance
insect ventilation
-large SA:V so sufficient diffusion
-size of spiracles controlled

fish ventilation
-water enters mouth which changes volume/pressure
-water pushed out gills
fish gas exchange
-large number of gill filaments increasing surface area
-lots of capillaries so good supply
-tips of gill filaments overlap to slow down water movement

Question 20

describe how trachea of mammal different to insect

Answer 20

mammals only have one
mammal trachea has cartilage but insects have chitin
-mammal trachea has smooth muscle and goblet cells

Question 21

how are gills adapted for efficient gas exchange

Answer 21

many filaments create large SA
central blood vessel provides good blood supply which maintains steep concentration gradient
secondary lamellae provide large surface area
-short diffusion distance between blood and water