Exchange Surfaces

Question 1

why do multicellular organisms require specialised gas exchange surfaces

Answer 1

smaller surface area to volume ratio means the distance needed to cross is larger and substances cannot easily enter cells

Question 2

name three features of an efficient gas exchange surface

Answer 2

large surface area
short diffusion distance
steep concentration gradient

Question 3

describe the trachea and its function in mammalian gas exchange

Answer 3

wide tube supported by c shaped cartilage to keep the air passage open during pressure change
lined by ciliated epithelial cells which move mucus (produced by goblet cells) towards the throat to prevent lung infection
carries air to bronchi

Question 4

describe the bronchi and their function in mammalian gas exchange

Answer 4

supported by rings of cartilage and lined with epithelial and goblet cells
allow passage of air into bronchioles

Question 5

describe the bronchioles and their function in mammalian gas exchange

Answer 5

mostly only smooth muscle and elastic fibres so they can contract and relax
allow passage of air into alveolies

Question 6

describe the alveoli and its function in mammalian gas exchange

Answer 6

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

Question 7

explain the process of inspiration

Answer 7

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

Question 8

explain the process of expiration

Answer 8

external intercostal muscles relax bringing ribs down and in
diaphragm relaxes and domes
volume of thorax decreases
air pressure inside lungs is higher than outside so air forced out

Question 9

explain how a spirometer works

Answer 9

used to measure lung volume
person breathes into airtight chamber leaving a trace on a graph
shows volume of breath

Question 10

define vital capacity

Answer 10

maximum volume of air that can be inhaled or exhaled in one breath

Question 11

define tidal volume

Answer 11

volume of air we breathe in and out in one normal breath

Question 12

define breathing rate

Answer 12

number of breaths we take per minute

Question 13

name and describe the two main features of a fish gas exchange system

Answer 13

gills-located in body and supported by arches
multiple projections of gill filaments that are stacked up
lamellae- at right angles to gill filaments giving an 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 allowing water to flow in
water pumped over lamellae by operculum
oxygen diffuses into bloodstream
waste co2 diffuses into water and flows back out gills

Question 15

how does countercurrent system maximise oxygen absorbed

Answer 15

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

Question 16

name and explain the three main features of insect gas exchange system

Answer 16

spiracles-holes on body’s surface that may be opened or closed
tracheae-large tubes extending through body tissues
Tracheoles - small branches off tracheae

Question 17

explain the process of gas exchange in insects

Answer 17

gas moves in and out of tracheae through spiracles
diffusion gradient allows oxygen to diffuse into waste tissue while waste co2 diffuses out
contraction of muscles in tracheae allows mass movement of gas in and out