exchange surfaces

Question 1

how does SIZE effect the need for an exchange system ?

Answer 1

in small organisms , cytoplasm is very close to the environment so simple diffusion is enough – short diffusion distance
however
in multicellular organisms with several cell layers there is a greater distance that substances need to travel to reach the centre – diffusion alone would be insufficient to supply innermost cells

Question 2

how does SA:V RATIO effect the need for an exchange system ?

Answer 2

in small organisms they have a larger SA:V ratio so they have a large enough surface to provide the organism with he resources it needs and for waste products to diffuse out
this is the opposite for larger organisms

Question 3

what is an exchange surface ?

Answer 3

specialised area adapted to make it easier for molecules to cross from one side of the surface to another eg. alveoli ,gills ,villi

Question 4

how does LEVEL OF METABOLIC ACTIVITY effect the need for an exchange system ?

Answer 4

this is the amount of energy transferred by that organism within a given period of time
it requires oxygen to release energy from food in aerobic respiration
organisms with a high metabolic rate tend to be:
-larger = higher rate so need to exchange materials fast
-very active = movements mean it need lots of nutrients and O2
-need to keep warm eg. mammals

Question 5

what are the features of effective exchange surfaces ?

Answer 5

larger surface area
good blood supply or ventilation to maintain a steep concentration gradient
short diffusion distance / thin walls

Question 6

what are the adaptations of alveoli ?

Answer 6

1. warm so rate of diffusion is high
2. good blood supply to maintain steep CG
3. ventilated constantly to supply O2 and remove CO2 to maintain steep GC
4. large number of spherical small alveoli to increase SA
5. alveoli walls are made of squamous epithelium which consist of flattered cells that are one cell thick = reduced diffusion distance
6. elastic fibres, alveoli stretch increasing SA, recoil forcing air at, helping conc gradient
7. inner surface of alveoli lined with lung surfactant
   - phosolipids coats the lung surface
   - reduces cohesion between water molecules and prevents alveoli collapsing
   - further increased SA

Question 7

what makes up our respiratory system ?

Answer 7

nasal passage, mouth cavity, trachea, rings of cartilage, bronchi, bronchioles, alveoli –> capillary’s
also has the ribs and diaphragm are involved

Question 8

what is the parts of the lungs ?

Answer 8

pharynx, larynx, trachea, rings of cartilage, bronchus, bronchioles, ribs, intercostal muscle, pleural membranes, diaphragm, pleural cavity lung, sternum, external intercostal muscle, clavicle

Question 9

describe the structure of lungs ?

Answer 9

each lung is enclosed in a double membrane known as the pleural membrane (parietal pleura and visceral pleura)
the space between the two membranes is called the pleural cavity and is filled with a small amount of pleural liquid which lubricates the lungs
it also adheres the lung to the chest well by cohesion so that the lungs expand with the chest while breathing

Question 10

what is the function of ciliated epithelium cells ( in the thorax) ?

Answer 10

line the trachea and bronchi
tiny projections cilila sweep mucus, dust, bacteria, and microorganisms up and away from the lungs

Question 11

what is the function of goblet cells ( in the thorax) ?

Answer 11

embedded throughout the ciliated epithelium
produce mucus

Question 12

what is the function of mucous glands ( in the thorax) ?

Answer 12

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

Question 13

what is the function of cartilage ( in the thorax) ?

Answer 13

rings of cartilage are strong and flexible
hold trachea open
enable it to move and flex as we breath

Question 14

what is the function of smooth muscle ( in the thorax) ?

Answer 14

found in walls of bronchioles and bronchi
unconscious muscle
helps to regulate the flow of air into and out of the lungs by dilating and widening when more air is needed

Question 15

what is the function of elastic fibres ( in the thorax) ?

Answer 15

found in squamous epithelium of the alveolar walls
allow for alveoli to stretch as they fill with air recoil to push air out
allows for a large SA

Question 16

what is the function of squamous epithelium ( in the thorax) ?

Answer 16

flat, thin cells in the walls of alveoli
allows for oxygen and CO2 to have a short diffusion distance

Question 17

what helps to balance between gas exchange and retaining water in land animals ?

Answer 17

the inner surface of alveoli are covered in a thin layer of a solution of water, salts and lung surfactant.
the surfactant reduces the cohesive forces between water molecules making it possible for the alveoli to remain inflated
oxygen dissolves in the water and then into the blood
some water evaporates into the air of the alveoli and is lost in breathing

Question 18

what are 3 features of the nasal cavity ?

Answer 18

1. large surface area and good blood supply - warms the air as it passes into the body
2. mucus and hair - traps dust and bacteria to prevent them from reaching the lungs which would cause infection
3. moist surfaces - increases the humidity of the incoming air this reduces the evaporation of water in the lungs

Question 19

describe the structure of the trachea ?

Answer 19

the airway from the mouth and nose to the bronchi
- supported by a layer of cartilage that holds it open and prevents collapse
- rings are incomplete to allow it to bend when food is swallowed behind it in the oesophagus
- gaps are filled with smooth muscle and elastic fibres which allow for flexibility
- lined with goblet cells to produce mucus
- lined with ciliated epithelium cells to move mucus and trapped dust ect along

Question 20

describe the structure of the bronchus ?

Answer 20

two extensions of the trachea
similar structure to trachea but smaller

Question 21

describe the structure of the bronchioles ?

Answer 21

1mm or less in diameter
no cartilage
held open by smooth muscle which contracts to reduce air flow
lined with a thin layer of epithelial tissue for some gas exchange

Question 22

describe the structure of the alveoli ?

Answer 22

little air sacs where most of gas exchange occurs
200- 300 micrometres in diameter
made from a thin layer of squamous epithelium cells, collagen and elastic fibres which allows for stretch and recoil to more air out
surfactant keeps them open

Question 23

what happens when you inhale ?

Answer 23

active
diaphragm contracts and flattens
external intercoastal muscle contract and shortens which pulls ribs up and out
volume of the thorax increases
pressure of thorax reduces
air is drawn in

Question 24

what happens when you exhale ?

Answer 24

passive
diaphragm relaxes and moves into dome shape
external muscles relax which moves ribs down and in
volume of the thorax reduces
pressure of thorax increases
air is pushed out

Question 25

what happens in forced exhalation ?

Answer 25

active diaphragm relaxes and curves internal intercoastal muscles contract which pulls the ribs down and in external intercoastal muscles relaxed abdominal muscles contract moving the diaphragm up volume of thorax reduces quickly pressure of thorax increases quickly air is pushed out

Question 26

what are advantages and disadvantages of the bell jar model ?

Answer 26

advantages ; - diaphragm moves up and down to change the volume and pressure - it has a trachea and bronchi - elasticity of lungs is similar to elastic recoil of alveoli disadvantages ; - at relaxed state the rubber sheet is flat not domed like the human diaphragm - no intercoastal muscles or rib cage - no alveoli or bronchioles

Question 27

what is a peak flow meter ?

Answer 27

measures the rate a which air is forced out of the lungs - often used by asthmatics

Question 28

what is a vitalograph ?

Answer 28

more sophisticated version of peak flow meter patient breaths out as quickly as possible the volume of air is called forced expiratory volume in 1 second records on a graph

Question 29

what is a spirometer ?

Answer 29

a machine that measures lung volume patient breath in and out and this moves parts which draws a trace on a graph

Question 30

how does a spirometer work ?

Answer 30

- the lower half of the tank is static and filled with water - the upper half of the tank is mobile and full of air - as the patient breaths out, the volume of air in the tank increases and the upper half will rise - as they breath in, air is removed from the tank and the upper half will fall - a marker is attached to the upper half producing a trace on a graph

Question 31

what is soda lime used for in a spirometer ?

Answer 31

it absorbs co2 breathed out by the patient as the oxygen is used up the system is closed so no air can leave or enter so over the experiment the volume of air in the lungs and spirometer will decrease this decrease is equal to the volume of oxygen used up

Question 32

what are the precautions of using a spirometer ?

Answer 32

- use fresh functioning soda lime - mouthpiece sterilized - healthy subject - water chamber should not be overfilled - no air leaks in the apparatus as this would give invalid results

Question 33

what is tidal volume ?

Answer 33

volume of air tract that moves into and out of lungs with each resting breath - 0.5dm3 in the average adult - 15% of vital capacity

Question 34

what is vital lung capacity ?

Answer 34

the largest volume of air that can be breathed out ( when the strongest inhale is followed by the strongest exhale ) -3 to 5 dm3 in average adult

Question 35

what is inspiratory reserve volume ?

Answer 35

the maximum volume of air you can breath in over and above normal inhalation

Question 36

what is expiratory reserve volume ?

Answer 36

the maximum volume of air you can force out over and above the normal exhalation

Question 37

what is residual volume ?

Answer 37

volume of air left in your lungs when you have exhaled as hard as possible - this cannot be directly measured - includes whatever air is held in the trachea , bronchi and larger bronchioles - the alveoli are kept open for continual gas exchange

Question 38

what is total lung capacity ?

Answer 38

the sum of vital capacity and residual volume

Question 39

what is breathing rate ?

Answer 39

number of breaths taken per minute calculated on spirometer ( peaks per minute )

Question 40

what is ventilation rate ?

Answer 40

total volume of air inhaled per minute ventilation rate = tidal volume x breathing rate

Question 41

how does exercise effect breathing and ventilation rate ?

Answer 41

increases both as oxygen demand increases so that it can be supplied to the tissues tidal volume can increase up to 50 %

Question 42

what is an insects exoskeleton made of ?

Answer 42

chitin - it is impermeable to gases, preventing gas exchange across this surface

Question 43

what are spiracles ?

Answer 43

small openings found along the thorax and abdomen of insects - opened and closed by sphincters - the site of water loss and gas exchange - lined bristles which filter unwanted particles of air to prevent damage - trap moist air to reduce water loss

Question 44

when do the spiracles open and close ?

Answer 44

open is they need lots of oxygen or if co2 builds up ; to increase gas exchange closed if oxygen demands are lower or the environment is dry

Question 45

what are an insects tracheae ?

Answer 45

run from the spiracles to the tissues 1mm in diameter covered in chitin to support the tracheae preventing it from collapsing and keeping the airway open

Question 46

what are an insects tracheoles ?

Answer 46

branch into a series of tracheoles which divide until their microscopic ends penetrate between body cells - have tracheole fluid in the ends 0.6 micrometres diameter they provide oxygen to the cells

Question 47

how are tracheoles adapted ?

Answer 47

- each tracheole is an elongated cell with many branches to increase SA - walls are thin to reduce diffusion distance - walls are moist, oxygen dissolves in this moister to then diffuse into cells - not lined with chitin so gas exchange can occur

Question 48

what happens in the tracheoles when an insect has high oxygen demands ?

Answer 48

during strenuous activity insects require more oxygen to meet demand, tracheole fluid build up at the ends of tracheoles reduces the SA - they will carry out more anaerobic respiration with produces lactic acid - lactic acid builds up in tissue cells lowering the water potential of them - this changes the conc gradient and causes water from the tracheal fluid to move into the cells by osmosis - this increases the SA of the tracheoles as there is less fluid build up and more efficient gas exchange can occur

Question 49

how does mechanical ventilation happen in insects ?

Answer 49

- use rhythmic abdominal movements to change the volume of the bodies move air in and out of the spiracles - use wing movements to pump their thoraxes too inspiration ; volume of thorax increases and pressure decreases, air moves in exhalation ; volume of thorax decreases and pressure increases, air moves out

Question 50

how do insects use air sacs for ventilation ?

Answer 50

- flexible areas of the tracheal system that can store extra air until its needed ( when the spiracles are closed ) - they are squeezed by flight muscles - repetitive expansion and contraction of air sacs ventilates the tracheal system to increase the amount of air moved around

Question 51

why cant mammalian ventilation work in fish ?

Answer 51

water is denser and more viscous than air it also has a lower oxygen content than air it is faster and easier for fish to move water over gills in one direction than in and out

Question 52

what is the gill cavity ?

Answer 52

contains the gills , protected by the operculum - have 4 gills on each side

Question 53

what is the operculum ?

Answer 53

gill cover or bony flap that protects the gill cavity and is active in maintaining water flow over the gills

Question 54

what is the gills ?

Answer 54

2 gill plates which are stacks of primary lamellae which have secondary lamellae on them at right angles ( site of gas exchange ) the 2 gill plates are attached by the gill arch - they also have gill rakers which are attached to the arch and stop food passing through the gills

Question 55

what are the adaptations of gills ?

Answer 55

1. the secondary lamellae project at right angles and there are lots of them, this increases surface area 2. water allows the gills filaments to separate, increasing the SA 3. the secondary gill lamellae are a few cells thick to reduce diffusion distance 4. contains lots of blood capillaries to transport oxygen away, this maintains a steep conc gradient

Question 56

explain countercurrent flow ?

Answer 56

blood flows in the opposite direction to the flow of water this results in the oxygen conc gradient between he blood in the gills and the water to be maintained across the whole length of the gills there is always more oxygen in the water than the blood so it moves down the conc gradient into the blood

Question 57

how do fish inhale ?

Answer 57

1. opens its mouth ( buccal cavity ) and floor of buccal cavity lowers 2. increases the volume and decreases the pressure in the buccal cavity 3. the pressure is higher outside the mouth so water flows into it down a conc graident

Question 58

how do fish exhale ?

Answer 58

1. closes it mouth ( buccal cavity) and floor raises 2. this decreases the volume and increases the pressure 3. the fish expands the gill cavity which increases the volume and decreases the pressure here 4. because the pressure is higher in the mouth water moves down the conc gradient into the gills where gas exchange occurs 5. as there is water in the gills the pressure increases and this forces the operculum to open and water flows out