CHAPTER 7 - EXCHANGE SURFACES AND BREATHING

Question 1

What are the two min reasons why diffusion is enough to supply the needs of a single-celled organism

Answer 1

The metabolic activity of a single celled organism is usually low, so the oxygen demands and carbon dioxide production of the cell are relatively low

The Surface area to volume ratio of the organism is large

Question 2

Why do larger organisms have a higher metabolic activity than most single celled organisms?

Answer 2

Amount of energy used in moving means oxygen demands of the muscle cells deep in the body will be high and they produce more CO2

Distance is too far for diffusion to take place, so exchange surfaces are required

Question 3

What is the usual shape used to calculate SA:V

Answer 3

A sphere - SA: 4 pi r2
V: 4/3 pi r3

Question 4

What are some features of specialised exchange surfaces

Answer 4

Very high SA:V - Diffusion rates
Thin layers - Short diffusion distance
Good blood supply - Ensures gradient is maintained for diffusion
Ventilation to maintain diffusion gradient

Question 5

Explain why single-celled organisms do not need specialised exchanged surfaces

Answer 5

Metabolic activity relatively low

so relatively little oxygen needed or carbon dioxide produced

SA : V is large

so diffusion distances small

Question 6

Describe the main features of any efficient exchange surfaces and explain how the structures relate to their functions

Answer 6

Large SA for exchange to overcome limitations of SA : V ratio of larger organisms

thin layers so
distances substances have to diffuse short, making the process fast and efficient

good blood
supply so substances constantly delivered to and removed from exchange surface which maintains
steep concentration gradient for diffusion

ventilation (for gaseous systems) maintains
concentration gradients and makes process more efficient

Question 7

One roughly spherical organism has a radius of 2au. Another has a radius of 6au. Compare the SA:V ratios of the organisms and use these to explain why the larger organisms need specialised exchange surfaces

Answer 7

Radius 2 au = 3:2 Radius 6 au = 1:2

The SA : V ratio of smaller animal is three times bigger than that of larger animal, this illustrates how
the SA : V ratios of larger animals are much smaller than those of smaller animals

as a result they
need specialised exchange systems to get enough oxygen in, or carbon dioxide out of the system

Question 8

Why do mammals have such a high metabolic rate

Answer 8

They are active and maintain their body temperature independent of the environment

Question 9

Where does exchange of gases occur in a mammal

Answer 9

Lungs

Question 10

What are the key structures in the mammalian gas exchange system

Answer 10

Nasal cavity
Trachea
Broncrhus
Bronchioles
Alveoli

Question 11

What are the important features of the nasal cavity

Answer 11

A large SA with a good blood supply, warms air to body temperature

Hairy lining, secretes mucus to trap dust and bacteria, prevents delicate lung tissue

Moist surfaces, increase humidity of incoming air, reducing evaporation from the exchange surfaces

Question 12

What is the trachea and what is it supported by

Answer 12

The main airway carrying clean, warm and moist air from the nose down into the chest

Wide tube supported by strong flexible incomplete rings of cartilage which stops the trachea from collapsing

Question 13

Why are the cartilage rings of the trachea incomplete

Answer 13

So food can move easily down the oesophagus behind the trachea

Question 13

What are the trachea lined with?

Answer 13

Ciliated epithelium with goblet cells between and below the epithelial cells

Question 14

What are the jobs of cilia and goblet cells lining the trachea and its branches

Answer 14

Goblet: secretes mucus onto lining of trachea to trap dust and microorganisms that have escaped nose lining

Cilia: Waft away microorganisms from the lungs so that they are swallowed and digested

Question 15

What are the bronchi

Answer 15

Divisions of the trachea that go to the separate lungs, with the same supporting rings of cartilage

Question 16

What are Bronchioles and what do they contain

Answer 16

Divisions of the Bronchi, without any cartilage rings.

They contain smooth muscle in the walls that constrict then the muscle contracts, and dilate when the muscle relaxes

Also continue smooth layer of flattened epithelium to allow some gaseous exchange

Question 17

What are Alveoli

Answer 17

Tiny air sacs at the end of bronchioles which are the main gas exchange surfaces of the body

Question 18

What do alveoli contain to allow it to function

Answer 18

Flattened epithelial cells - gas exchange

Collagen and elastin (elastic fibres) to allow the stretch and recoil as air is drawn in

Question 19

What are the main adaptions of the alveoli that allow for effective gaseous exchange

Answer 19

Large Surface area

High number - 300-500 million alveoli per lung

Thin layers

Good blood supply - brings CO2 and takes O2

Ventilation - keeps diffusion gradients for O2 and CO2

Question 20

What are the inner walls of the lungs coated in?

Answer 20

Water, salts and lung surfactant

Question 21

What is the importance of lung surfactant

Answer 21

Makes it possible for the alveoli to remain inflated, so the alveoli don’t stick together

Question 22

What is the job of water on the inside lining of the alveoli

Answer 22

Oxygen dissolves in the water before diffusing into the blood, but water can also evaporate into the air in the alveoli

Question 23

How does air move in and out of the lungs?

Answer 23

Result of pressure changes in thorax (chest cavity) brought about by breathing movements

Question 24

What is ventilation

Answer 24

The movement of air

Question 25

What does the ribcage provide

Answer 25

A semi-rigid case within which the pressure can be lowered compared to the air outside it

Question 26

What is the Diaphragm

Answer 26

A broad domed shaped muscle, which forms the floor of the thorax

Question 27

Where are the intercostal muscles found?

Answer 27

Between the ribs

Question 28

What are the pleural membranes

Answer 28

The membrane that line the thorax

Question 29

What are the pleural cavities and what is it filled with and why

Answer 29

The space between pleural membranes which is filled with a thin layer of lubricating fluid so the membranes can slide easily over each other as you breathe

Question 30

What is inspiration

Answer 30

The taking in of air (also known as Inhalation)

Question 31

Is inspiration an active or passive process?

Answer 31

Active

Question 32

Describe the events in inspiration

Answer 32

Diaphragm contracts, flattening and lowering External intercostal muscles contract, moving ribs upwards and outwards Volume of thorax increases, so pressure reduces in thorax This is lower than outside, so air is drawn into the lungs, so the pressure equalises inside and outside the chest

Question 33

What is Expiration

Answer 33

The breathing out of air (also called exhalation)

Question 34

Is expiration an active or passive process?

Answer 34

passive - most of the time

Question 35

Describe the events in expiration (normal)

Answer 35

Diaphragm relaxes, moves up to its resting domed shape External intercostal muscles relax, so ribs move downwards and inwards under gravity Alveoli return to normal size due to elastic fibres Decreases volume of thorax, increased pressure, greater than outside Air moves out until pressure is equal again

Question 36

Describe the events in forcible expiration

Answer 36

Internal intercostal muscles contract, pulling ribs down hard and fast, and the abdominal muscles contract, Pulling the diaphragm up to increase the pressure in the lungs rapidly

Question 37

Asthma? 161

Question 38

Explain how the nose is adapted to make gaseous exchange possible

Answer 38

large SA with good blood supply warms the air to body temperature hairy lining secretes mucus which traps dust and bacteria, protecting delicate lung tissue from irritation and infection moist surfaces increase humidity of incoming air, reducing evaporation from exchange surfaces produces air at similar temperature and humidity to air already in lungs

Question 39

Explain how the trachea is adapted to make gaseous exchange possible

Answer 39

wide tube, supported by incomplete rings of strong, flexible cartilage that stop tube collapsing rings incomplete so food moves easily down oesophagus behind trachea lined with ciliated epithelium with goblet cells between epithelial cells goblet cells secrete mucus to trap dust and bacteria cilia beat and move mucus and trapped particles away from lungs to throat to be swallowed and digested.

Question 40

Explain how the bronchioles are adapted to make gaseous exchange possible

Answer 40

Small tubes spreading into both lungs the smaller bronchioles (diameter 1mm or less) have no cartilage rings. The walls contain smooth muscle which contracts to close up bronchioles and relaxes to dilate them, changing the amount of air entering the lungs lined with thin layer of flattened epithelium, making some gaseous exchange possible

Question 41

Explain how the alveoli are adapted for gaseous exchange

Answer 41

large SA of (~50–75 m2) for gaseous exchange thin layers so short diffusion distances good blood supply with large capillary network supplying alveoli bringing carbon dioxide and picking up oxygen, maintains steep concentration gradient for carbon dioxide and oxygen between air in alveoli and blood in capillaries good ventilation as breathing moves air in and out of alveoli, helping maintain steep diffusion gradients for oxygen and carbon dioxide between blood and air in lungs

Question 42

In some diseases, the alveoli breaks down to give much bigger air sacs. Explain how this reduces their effectiveness for gaseous exchange

Answer 42

Alveolar structure breaks down giving air sacs with much bigger radii this reduces surface to volume ratio which makes them much less effective for gaseous exchange

Question 43

Smokers get more infections of the breathing system than non-smokers. Suggest Why

Answer 43

Trachea lined with ciliated epithelium with goblet cells that secrete mucus mucus traps dust and bacteria cilia beat to move mucus and trapped particles away from lungs to throat to be swallowed and digested in smokers cilia anaesthetised so do not beat mucus with its load of bacteria and dust moves down into the lungs more pathogens reach lungs so smokers more likely to get infections of breathing system than non-smokers with active cilia

Question 44

What are the different ways to measure the capacity of the lungs

Answer 44

Peak flow meter Vitalograph Spirometer

Question 45

What is a peak flow meter

Answer 45

A simple device that measures the rate at which air can be expelled from the lungs People who have asthma often use these to monitor how well their lungs are working (I HAVE ONE)

Question 46

What are vitalograph and how does it work

Answer 46

A more sophisticated version of the peak flow meter. The patient being tested breathes out as quickly as they can through a mouthpiece, and the instrument produces a graph of the amount of air they breathe out and how quickly it was breathes out. This volume of air is called the first expiratory volume in one .

Question 47

What is a spirometer used to measure

Answer 47

Difference of the lung volume, or to investigate breathing patterns (pg 163)

Question 48

What aspects of the lung volumes can a spirometer measure

Answer 48

Tidal volume Vital capacity Inspiratory reserve volume Expiratory reserve volume Residual volume Total lung capacity

Question 49

What is tidal volume

Answer 49

The volume of air that moves into and out of the lungs with each resting breath

Question 50

What is vital capacity

Answer 50

The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath

Question 51

What is the inspiratory reserve volume

Answer 51

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

Question 52

What is the expiratory reserve volume

Answer 52

The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out

Question 53

What is the residual volume

Answer 53

The volume of air that is left indoor lungs when you have exhaled as hard as possible. This cannot be measured directly

Question 54

What is the total lung capacity

Answer 54

The sum of the vital capacity and the residual volume

Question 55

Read graphs and fill in gaps for lung graphs!!

Question 56

What is breathing rate

Answer 56

The number of breaths taken per minute

Question 57

What is ventilation rate

Answer 57

The total volume of air inhaled in one minute

Question 58

What is the formula to calculate ventilation rate

Answer 58

Ventilation rate = tidal volume x Breathing rate

Question 59

Describe how you could investigate breathing rates in a school laboratory

Answer 59

Record number of breaths for a timed period and repeat calculate means of results under different conditions use spirometer to observe breathing rate

Question 60

Describe the relationships between tidal volume, breathing rate and oxygen uptake

Answer 60

Ventilation rate is tidal volume of air breathed in at each breath, multiplied by number of breaths per minute (breathing rate) units are cm3 or litres per minute. VR = TV × bpm Oxygen uptake closely related to ventilation rate, the more air is moved into the lungs, the more oxygen can be taken up by haemoglobin in blood so as ventilation rate increases oxygen uptake also increases

Question 61

Why can't insects use a similar gas exchange system to mammals

Answer 61

Tough Exoskeleton, very limited diffusion No blood pigments to cary oxygen

Question 62

What are spiracles

Answer 62

Small openings along the thorax and abdomen, in which air enters and leaves the insect, but water is also lost

Question 63

How do insects minimise water loss in gas exchange

Answer 63

have spiracle sphincters which keep spiracles closed as much as possible to minimise water loss

Question 64

What are the tracheae

Answer 64

Largest tubes in the insect respiratory system leading away from the spiracles, up to 1mm in diameter which carry air into the body

Question 65

What are the tracheae lined by and what job does it do

Answer 65

Chitin Keeps them open even if they are bent or pressed

Question 66

What parts of the insect are made from chitin

Answer 66

Exoskeleton and linings of tracheae

Question 67

What do the tracheae branch into

Answer 67

tracheoles

Question 68

What are tracheoles

Answer 68

A branch of the tracheae which is a single elongated cell without any chitin and is permeable to gases

Question 69

Is chitin permeable to gases

Answer 69

no

Question 70

What is gas exchange controlled by in insects

Answer 70

Opening and closing of spiracles

Question 71

In insects that have very high energy demands, how do they supply the extra oxygen necessary

Answer 71

Mechanical ventilation of the tracheal system - air is actively pumped into the system by muscular pumping movements of the thorax. Changes volume of air in the body through pressure changes Collapsible enlarged tracheae - act as reservoirs, increase amount of air moved through the system - inflated and deflated by movements of thorax and abdomen

Question 72

Although animals that get their oxygen from water dont have to prevent water loss, what challenges do they face?

Answer 72

Water is 1000 times denser than air, and 100 times thicker - and has a low oxygen content

Question 73

Why do bony fish, especially big active fish like trout and cod, need specialised exchange systems

Answer 73

As they are active, their cells have a high oxygen demand, and due to their SA:V, diffusion wouldn't be enough to supply their inner cells with the oxygen they need, and their scaly outer covering doesn't allow for gaseous exchange

Question 74

What is the protective structure that protects the gills

Answer 74

Operculum (a bony flap)

Question 75

Aside from protecting the the gills, what job do the operculum have

Answer 75

maintaining a flow of water over the gills

Question 76

What are the components of the gills

Answer 76

Gill operculum Gill cavity Gill arches (and gill rakers) Gill lamellae Gill filaments (and Gill plates) (pg 168)

Question 77

What do the Gill lamellae do

Answer 77

Provide rich blood supply and large surface area, are the main site for gaseous exchange in fish`

Question 78

What do gill filaments need

Answer 78

A constant supply of water to keep them apart, exposing a large surface area needed for gaseous exchange

Question 79

What are gill plates

Answer 79

Stacks of gill filaments

Question 80

How do bony fish maintain moving water over the gills

Answer 80

Simply opening their mouth and operculum, (when moving) but when the fish stops moving, the flow of water also stops (operculum movement)

Question 81

What is ram ventilation

Answer 81

The technique used by more primitive cartilaginous fish eg. sharks and rays which relies on continual movement past the gills Most bony fish dont rely on movement-generated water flow over the gills

Question 82

Describe the operculum movement to allow for oxygen to pass the gills without the fish moving

Answer 82

Mouth (buccal cavity) is lowered, increasing in volume Pressure in cavity drops, drawing water in At the same time, opercular valve shuts and opercular cavity expands This lowers pressure in opercular cavity containing the gills Floor of buccal cavity starts to move up, increasing pressure there so water moves from buccal cavity over the gills Mouth closes and sides of the opercular cavity moves inwards, increasing pressure and forcing water over the gills (pg 169)

Question 83

How do fish have an efficient gas exchange system

Answer 83

USUAL DIFFUSION POINTS PLUS Tips of gill filaments overlap - increasing resistance to flow of water to slow down movement of water, to allow for more gaseous exchange to take place Countercurrent flow - maintains a steep concentration gradient, so oxygen will continue to diffuse quickly into the blood and saturation doesnt occur (pg 170)

Question 84

Suggest why a fish will die when it is left out of water for too long

Answer 84

In air gill filaments all stick together SA for gas exchange is greatly reduced and so fish dies from lack of oxygen

Question 85

Explain how insects that have particularly high energy requirements can increase the amount of gaseous exchange taking place in their bodies

Answer 85

Fluid towards end of tracheole limits penetration of air for diffusion when energy demands high lactic acid build up in tissues, water moves out of tracheoles by osmosis, exposing more surface area for gaseous exchange (1); tracheal system can be mechanically ventilated with air actively pumped into system by muscular pumping movements of thorax and/or the abdomen movements change volume of body, changing pressure in tracheae and tracheoles so air drawn into trachea and tracheoles, or forced out, as pressure changes, making gaseous exchange more efficient Some very active insects have collapsible enlarged tracheae or air sacs which act as air reservoirs, used to increase amount of air moved through gas exchange system they are usually inflated and deflated by ventilating movements of thorax and abdomen

Question 86

Explain how the structure of the gas exchange system of bony fish maximises the amount of oxygen that can be taken from the water

Answer 86

Gills have large stacks of gill filaments carrying gill lamellae that have large surface area good blood supply and thin layers needed for successful gaseous exchange. Constant flow of water maintained over gills so best possible diffusion gradient for the respiratory gases tips of gill filaments overlap – increasing resistance to flow of water, slowing it down for more effective gaseous exchange water and blood flow in opposite directions. Countercurrent exchange system maximises the potential exchange of gases