3.1 Exchange surfaces

Question 1

Why do we need specialized exchange surfaces ?

Answer 1

. larger organisms have a small SA:V ratio

. need a large SA so that more particles can be can diffuse so diffusion becomes more efficient

.thin for a short diffusion distance so diffusion is quicker

. the high metabolic rate means they have an increased demand for oxygen for respiration

Question 2

what are the features of an efficient exchange surface?

Answer 2

1. increased surface area: increase of uptake in particles so diffusion is efficient
2. short diffusion distance: diffusion happens faster
3. good blood supply/ventilation: to maintain concentration gradient

Question 3

what are the features of the alveoli that assist in gas exchange - 5 marks

Answer 3

1. large SA- covered in lots of alveoli, more diffusion of O2 in blood and CO2 out of blood
2. thin walls- one cell thick, shortens diffusion distance
3. good blood supply - explain
4. permeable walls- allow gases to diffuse through
5. moist- can dissolve gases which aids in diffusion

Question 4

name the structures of the mammalian gaseous exchange system? 8 structures

Answer 4

1. cartilage
2. ciliated epithelium
3. goblet cells
4. squamos epithelium
5. smooth muscle
6. elastic fibres
7. capillaries
8. mucous glands

Question 5

function of ciliated epithelium cells?

Answer 5

. line the trachea to the bronchi

. mucus which sweep dust, bacteria and other microorganisms up and away from the lungs to the mouth where they are swallowed and digested by stomach acid.

Question 6

function of goblet cells?

Answer 6

. embedded throughot the ciliated epithelium and are mucus producing cells.

Question 7

function of mucous glands?

Answer 7

. work with goblet cells in the trachea and bronchi to produce mucus.

Question 8

function and structure of cartilage?

Answer 8

C-shaped rings in trachea

Full rings in bronchus

To prevent it from collapsing, structural support

Question 9

function of smooth muscle?

Answer 9

. found in the walls of the bronchi and large bronchioles

. maintains blood pressure and the flow of air by dilating and widening

Question 10

function of elastic fibres?

Answer 10

. found in the squamous epithelium of the alveolur walls.

. alveoli stretch to fill with air then recoil to force air out.

. have a large surface area.

Question 11

function of squamous epithelium?

Answer 11

. consists of flat, thin cells in the walls of the alveoli.

. because they’re thin that means oxygen and carbon dioxide have a very short diffusion pathway during gas exchange.

Question 12

function of capillaries?

Answer 12

. small which is only wide enough for one red blood cell to travel through at any one time

. lots of capillaries, maintain conc. gradient

Question 13

what are the 6 main components of the gas exchange system?

Answer 13

1. trachea
2. lungs
3. bronchi
4. bronchioles
5. alveoli
6. capillary network

Question 14

describe the trachea:

Answer 14

. the airway that leads from the mouth and nose to the bronchi

. lined with mucus - secreting goblet cells and cilia

. walls contain smooth muscle and elastic fibres.

. C-shaped rings of cartilage to prevent it from collapsing

Question 15

describe the bronchi:

Answer 15

. plural for bronchus

. similar structure to trachea but have thinner walls ad smaller diameter

. cartilage in bronchi form full rings

Question 16

describe the bronchioles:

Answer 16

not supported by cartilage

.lined with ciliated epithelium

. do not contain any goblet cells

. get smaller as they get closer to the alveoli

. larger bronchioles have elastic fibres and smooth muscle that adjust the size of the airway to increase or decrease airflow

. smallest bronchioles do not have any smooth muscle but they do have elastic fibres

Question 17

Describe inspiration

Answer 17

. external intercostal muscles contract

. ribcage moves upwards and outwards

. diaphram contracts and flattens

. volume of thorax increases

. pressure inside thorax decreases

. air is drawn in

Question 18

Describe expiration

Answer 18

. external intercostal muscle relax

. ribcage moves downwards and inwards

. diaphram relaxes and becomes dome-shaped

. volume of thorax decreases

. pressure inside thorax increases

. air is forced out

Question 19

What is a spirometer?

Answer 19

a device that measures the movement of air breathed in and out of the lungs

Question 20

what are the precautions you should take when using a spirometer?

Answer 20

1. subject should be healthy-free of asthma
2. soda lime should be fresh
3. no air leaks in apparatus - gives inaccurate/invalid results
4. mouthpiece should be sterilised
5. water chamber should not be overfilled

Question 21

define vital capacity

Answer 21

The maximum vol of air that can be breathed in and out .

Question 22

define residual volume

Answer 22

the air that cant be expelled (remaining air left after max expiration)

Question 23

define tidal volume

Answer 23

the vol of air in each breath

Question 24

define breathing rate

Answer 24

how many breaths taken usually in a min

Question 25

define O2 uptake

Answer 25

the rate at which and org. uses up O2

Question 26

what is the key features of bony fish?

Answer 26

5 pairs of gills - with 2 rows of gill filaments attached to bony arch.

Filaments thin folded into primary secondary lamellae for a large SA.

Question 27

describe gas exchange in water for fish

Answer 27

. when mouth opens, the floor of the buccal cavity is lowered, volume increases, pressure decreases, water is taken in

. when mouth closes, the floor of the buccal cavity is raised, volume decreases and pressure increases

. the opperculum opens when the pressure increases and water leaves the gills.

Question 28

describe the countercurrent system in fish. (describe with a written diagram aswell)

Answer 28

.conc. of O2 in H20 is always greater than in blood to maintain a conc. gradient

. water flows over gills and blood flows in the lamallae in opposite direction to allow the blood continuosly be rich in oxygen

.so equillibrium is never reached, this is a constant process

Question 29

what are the key features in insects?

Answer 29

1. Internal network of tubes = tracheae
2. Tracheae are supported by strengthened rings to stop them collapsing
3. Tracheae divide into smaller tubes called tracheoles
4. Tracheoles extend throughout the body tissues of the insect = in this way air and the oxygen it contains is brought directly to the respiring tissues. They have thin permeable walls and go to individual cells.

Question 30

how does gas exchange happen in insects? ( 6 marks)

Answer 30

1. Air diffuses into tracheae through spiracles. Respiring cells use O2, so lowers [O2] so O2 diffuses down concentration gradient towards the ends of the tracheoles where respiring cells are
2. CO2 produced by respiring cells move down concentration gradient along tracheoles, into tracheae, towards spiracles to be released into the atmosphere.
3. Insects use rhythmic abdominal movements to move air in and out of spiracles - speeds up gas exchange.

= DIFFUSION IN AIR IS MUCH MORE RAPID THAN IN WATER, GASES EXCHANGED QUICKLY BY THIS METHOD.

Question 31

How are insects adapted to reduce water loss?

Answer 31

1. Waterproof/waxy cuticle all over their body surfaces = reduce evaporation.
2. Small SA:V ratio = minimise area over which water is lost.
3. Spiracles may be open and closed by a valve.
   - When open, water may evaporate from the insect.
   - Much of the time insects keep their spiracles closed to prevent this water loss.
   - Periodically they open them to allow gas exchange.
4. Tiny hairs around spiracles = reduces evaporation.

Question 32

describe the ventilation in insects

Answer 32

Movement of muscles in insects can create mass movements of air in and out of the tracheae.

Speeds up gas exchange

Question 33

Limitations of insects gas exchange system

Answer 33

Relys on exchange of substances between cells and environment

this makes the diffusion distance too long

limits the amount O2 the insect recieves

Question 34

Advantage of liquid in tracheoles passing into muscle fibres during flight?

Answer 34

larger surface area for gaseous exchange

Question 35

Explain why a muscle fibre cannot be large than 20 micrometres in diameter

Answer 35

1. diffusion pathway is too long/related to
   surface area to volume ratio;
2. to supply enough oxygen;

Question 36

Abdominal pumping increases the efficiency of gas exchange between the tracheoles
and muscle tissue of the insect. Explain why.

Answer 36

1. More oxygen enters/oxygen enters more quickly
2. So maintains concentration gradient/greater diffusion gradient

Question 37

The insect opens its spiracles at a lower frequency in very dry conditions.
Suggest one advantage of this

Answer 37

Less/no water lost / (more) water
retained;

Question 38

When flying, water is absorbed into the muscle tissue. Removal of water from the tracheoles increases the rate of diffusion of oxygen between the tracheoles
and muscle tissue. Suggest one reason why

Answer 38

1. Greater surface area exposed to air
2. Gases move/diffuse faster in air than water
3. Increases volume of air