topic four - exchange surfaces & the lungs - miss whithouse

Question 1

define an exchange surface?

Answer 1

an exchange surface is a specialised area
that is adapted to make it easier for molecules to
cross from one side of the surface to the other

Question 2

what must all exchange surfaces do to survive and what does this mean?

Answer 2

all organisms must exchange substances with their
environment in order to survive

this means there is a short diffusion pathway for exchange.

the exchange surface in unicellular organisms is the
plasma membrane

Question 3

what happens to the surface areas of single-celled organisms?

Answer 3

single-celled organisms like amoeba and Euglena (and some small multi-cellular organisms) have a large surface area-to volume ratio

Question 4

features of exchange surfaces?

Answer 4

large surface area

thin barrier

short diffusion distance fresh supply of molecules on one side to keep concentration high (e.g. ventilation in lungs)

removal of molecules on the other side to keep concentration low - it is important to maintain a
steep diffusion gradient (e.g. good blood supply)

Question 5

label the human respiratory system?

Answer 5

olc powerpoint

Question 6

adaptations of alveoli?

Answer 6

moist surface – gases dissolve easily

good blood supply – maintains a steep concentration gradient for diffusion

thin walls – shorter distance for gases to travel by diffusion

ventilation helps to maintain a steep
concentration gradient for diffusion

Question 7

what are the walls of alveoli made of?

Answer 7

the walls of alveoli are made up of flattened squamous epithelial cells (~5μm thick) with capillaries in close contact

Question 8

where does elastic fibres lie in the alveoli and what do they do?

Answer 8

elastic fibres lie between alveolar walls to provide strength and flexibility. They enable expansion (as we inhale) and recoil (to force air out of the lungs when we exhale)

Question 9

where is smooth muscle found?

Answer 9

smooth muscle is found in the walls of
the trachea, bronchi and the larger
bronchioles

Question 10

why does smooth muscle contract?

Answer 10

it contracts to constrict the airway and make the lumen narrower to reduce air flow to/from the alveoli

Question 11

where are elastic fibres found?

Answer 11

elastic fibres are also found in the
walls of the trachea, bronchi and the
bronchioles

Question 12

what do elastic fibres do?

Answer 12

it recoils in these tubes to dilate (widen) the airway after smooth muscle contraction had constricted it

Question 13

describe the process of how mucus is pushed back up?

Answer 13

ciliated cells contain many cilia, each of which contains microtubules, allowing cilia to move

goblet cells produce mucus, which traps pathogens to prevent infections, and stops alveoli from drying out

as inhaled pathogens and dust particles become trapped in the mucus, the cilia move in a synchronised motion to push the mucus to the top of the trachea
(coughed up or swallowed)

Question 14

why does cartilage have a c-shape in the trachea?

Answer 14

this allows greater flexibility and space for food to pass down the oesophagus (lies just behind the trachea)

Question 15

cartilage is strong and flexible how does this help?

Answer 15

stops the trachea and bronchi collapsing when you inhale

Question 16

what supports and helps keep airways open in the trachea and bronchi?

Answer 16

rings of cartilage

Question 17

what do external and internal muscles do?

Answer 17

external intercostal muscles

contract and internal intercostal muscles relax

Question 18

what happens when we inhale (inspiration)?

Answer 18

external intercostal muscles
contract and internal
intercostal muscles relax

this moves the ribcage UP
and OUT

diaphragm FLATTENS

volume of chest cavity
(thorax) INCREASES

PRESSURE inside lungs
decreases to below
atmospheric pressure

air rushes IN to lungs

Question 19

what happens when we exhale (expiration)

Answer 19

internal intercostal muscles
contract and external
intercostal muscles relax

this moves the ribcage
DOWN and IN

diaphragm MOVES UP

volume of chest cavity
(thorax) DECREASES

PRESSURE increases to
above atmospheric pressure

air rushes OUT of lungs

Question 20

what happens when the volume of the thorax increases?

Answer 20

the pressure
inside the thorax falls below atmospheric pressure. This
creates a pressure gradient so air moves into the lungs

Question 21

what does a spirometer measure and how does it work?

Answer 21

lungs function & It is a chamber filled with oxygen that floats on a tank of water

a pen tracks movement of the chamber to produce a trace (spirogram)

Question 22

review the spirometer practical?

Answer 22

powerpoint olc

Question 23

ways to use spirometer safely?

Answer 23

disinfect or sterilise the
mouthpiece between each new person

make sure there is sufficient
fresh air/oxygen in the
chamber

carbon dioxide accumulates
during use and could reach a dangerous level – use soda lime to absorb carbon dioxide

make sure that people using the spirometer are healthy e.g. not asthmatic

ensure the water level is below the opening of the tubes

Question 24

define tidal volume?

Answer 24

volume of air moved into and out of lungs in ONE breath at REST

Question 25

define vital capacity?

Answer 25

largest volume of air that can be moved into

and out of the lungs in the deepest breath

Question 26

define residual volume?

Answer 26

the volume of air always left in the lungs, even after the deepest breath

Question 27

define dead space?

Answer 27

Air in the bronchioles, bronchi and trachea that

does not contribute to gas exchange

Question 28

define inspiratory reserve volume?

Answer 28

the extra volume of air that is breathed in during a very DEEP breath in (compared to TV)

Question 29

define expiratory reserve volume?

Answer 29

the extra volume of air that is breathed out during a very DEEP breath out (compared to TV)

Question 30

define tidal volume?

Answer 30

tidal volume is the volume of air moved into and out of lungs in ONE single breath at REST

Question 31

how to work out the tidal volume?

Answer 31

measure the amplitude (height) of at least three waves and calculate the
mean

Question 32

define vital capacity?

Answer 32

the vital capacity is the largest volume of air that can be moved into and out of the lungs in the deepest single breath

Question 33

how to calculate the vital capacity?

Answer 33

measure the difference
between the highest
peak and lowest trough

vital capacity is the ERV
plus the IRV plus the TV

Question 34

how to calculate oxygen consumption?

Answer 34

add soda lime to the spirometer to absorb exhaled carbon dioxide and fill the chamber of the spirometer with oxygen

as you breathe in you take oxygen out of the chamber.

as you breathe out some of the oxygen is returned to the chamber (rises) but carbon dioxide is absorbed by the soda lime – overall drop in volume

the trace drops over time as oxygen is used up

draw a line across the tips of the peaks

measure the drop in trace (gradient) in a given time period

Question 35

what problems do fish have in gas exchange?

Answer 35

water has a lower concentration of oxygen than air

water is much more dense than air

fish can be very active, some swimming at 50+ mph

gases can’t diffuse through their skin

Question 36

adaptations of gills?

Answer 36

large surface area - allows more diffusion

permeable membranes - allows gases to diffuse

in (flattened cells) - short diffusion distance

good blood supply - maintains a steep concentration
gradient for diffusion

Question 37

what are the gills structure?

Answer 37

most bony fish (teleosts) have five pairs of gills

the gills are covered by a bony plate called the
operculum, which protects the gills and also keeps
water flowing in the right direction over the gills

each gill is supported by a bony gill arch which contains
blood vessels, supplying blood to the gill plates

the gill is formed of two rows of many gill filaments
(primary lamellae), which create a very large surface area

each gill filament
is covered in many
tiny structures called gill plates (secondary lamellae), which further increase
the surface area for gas exchange

Question 38

what happens in the fish dissection?

Answer 38

open and close the mouth to observe how the lower part of
the mouth moves (part of the mechanism for changing the
pressure inside the mouth/buccal cavity)

push the forceps into the open mouth and allow them to exit through the operculum at the side of the head - this shows
the path of water flow

lift up the operculum to show the gills below, and then use
the scissors to remove it

cut through the bone at the top and bottom of the gills
where they attach to the inside of the head to remove them

use the forceps to lift up the gill filaments and cut them
away from the skin they are attached to

to see the structure of the gills more clearly, place the gills in a beaker of water

Question 39

what is ram ventilation?

Answer 39

used by active fish species including many sharks and rays (elasmobranchs). The mouth is opened during swimming, such that water is forced through the mouth, across the gills and out of the gill slits

Question 40

what is buccal pumping?

Answer 40

used by many bony fish (teleosts)

Question 41

stages of buccal pumping?

Answer 41

1.the fish’s mouth opens and the operculum closes. The floor of the
buccal cavity drops

2. the volume of the buccal cavity increases and the pressure inside
   the buccal cavity decreases
3. Water flows through the mouth and into the buccal cavity down the
   pressure gradient
4. The mouth closes and the floor of the buccal cavity rises
5. The pressure inside the buccal cavity is now higher than in the
   opercular cavity
6. Water moves down the pressure gradient over the gills into the
   opercular cavity
7. The mouth is closed and the operculum is open
8. The sides of the operculum contract and increase the pressure
9. Water moves out of the opercular cavity and out of the fish’s body

Question 42

what are gill rakers?

Answer 42

As water moves over the gills during the process of buccal
pumping, food is filtered out of the water
This is aided by structures called gill rakers

Question 43

what is counter-current system?

Answer 43

in general terms, a counter-current system is where two
substances flow in opposite directions and there is an
exchange between them

e.g In fish gills, maximising the exchange of oxygen and carbon dioxide between the blood and water

Question 44

what happens in counter-current flow?

Answer 44

in counter-current flow, blood in the gills flows in the opposite direction to the flow of water

this results in the oxygen
concentration gradient between the blood in the gills and the water
being maintained across the entire length of the gill lamella

Question 45

why is a counter-current system for gas exchange

better than a concurrent (parallel flow) system?

Answer 45

because if they flow parallel than the flow creates a equilibrium counter-current

Question 46

gas exchange in insects?

Answer 46

insects do not transport
oxygen to tissues in blood –
they have an open circulatory system where the beating of the heart circulates body fluid around the body cavity

this means that circulation is
slow and is affected by body
movements

Question 47

what are spiracles?

Answer 47

terrestrial (land-living) 
insects have pores in each 
segment of their bodies 
called spiracles, which are 
similar to stomata on a the 
lower surface of a leaf

Question 48

how does ventilation occur?

Answer 48

in many insects, flexible expanded sections of the
tracheal system act as air sacs, which are
squeezed by flight muscles when insects are
active to aid ventilation

insects can use rhythmic abdominal movements
to change the volume of their thorax and force
air in/out of the spiracles

larger insects also use wing movements to change
the pressure gradient between the atmosphere
and the air sacs

Question 49

what are tracheoles characteristics and what does oxygen do in the tracheal?

Answer 49

tracheoles have thin, permeable walls and are filled with tracheal fluid

the ends of the tracheoles are open to individual
cells. Oxygen dissolves in the tracheal fluid and then diffuses from this fluid into body cells (while carbon dioxide diffuses in
the opposite direction)

Question 50

what happens when cells respire very rapidly?

Answer 50

the tracheal fluid can be
withdrawn into the body fluid.

this increases the surface area of the tracheole wall exposed to air so more oxygen can be absorbed when the insect is active

Question 51

two advantages of using tracheal system for gas exchange?

Answer 51

oxygen is transported directly to cells

provides a large surface area for gas exchange

Question 52

why do tracheoles lack a chitinous lining?

Answer 52

so that the respiratory surface is very
thin, making the diffusion of oxygen very
rapid