chapter 7 exchange surfaces and breathing

Question 1

what are the 2 main reasons why diffusion alone is enough to supply the needs of single celled organisms?

Answer 1

•metabolic activity of a single-celled organism is low so O2 demands and CO2 production of the cell are relatively low
•SA:V ratio of the organism is large

Question 2

what are the effective features that exchange surfaces have?

Answer 2

•high SA
•thin layers
•good blood supply
•ventilation to maintain diffusion gradient

Question 3

what does increased surface area do for exchange surfaces?

Answer 3

provides the area needed for exchange and to overcome the limitations of SA:V of larger organisms. e.g. villi and alveoli

Question 4

what do thin layers do for exchange surfaces?

Answer 4

provide short diffusion distances making the process fast and efficient.

Question 5

what does a good blood supply do for exchange surfaces?

Answer 5

the steeper the concentration gradient, the faster diffusion takes place. Having a good blood supply ensures substances are constantly delivered to and removed from the exchange surface maintaining steep conc gradient

Question 6

what does ventilation do for exchange surfaces?

Answer 6

for gases, a ventilation system also helps maintain conc gradients and makes the process more efficient. e.g. gills in fish

Question 7

why do mammals need to have a gaseous exchange system rather than just diffusion?

Answer 7

they have a small SA:V, they have a high metabolic rate because they’re active and need to maintain their body temperature. this means they need oxygen for respiration

Question 8

what is the gas exchange area in mammals?

Answer 8

the alveoli in the lungs

Question 9

what are 3 adaptations of the nasal cavity? and why do we have them?

Answer 9

•large SA with good blood supply to warm air to body temp
•hairy lining which secretes mucus to trap dust and bacteria protecting lung tissue
•moist surfaces to increase humidity of incoming air reducing evaporation from exchange surfaces

Question 10

what is the trachea?

Answer 10

the main airway carrying air from the nose to the chest. it is a wide tube supported by cartilage to stop it from collapsing

Question 11

what do goblet cells and ciliated epithelial cells do?

Answer 11

goblet cells produce mucus to trap pathogens and dust.
the cilia on the cillaited epithelium move this mucus away from lungs back to the mouth to be swallowed or spat out

Question 12

what is the order of structure in the respiratory system?

Answer 12

mouth>trachea>bronchi>bronchioles>aleveoli

Question 13

what specialised structures does the trachea have?

Answer 13

cartilage in c-shaped rings, cilliated epithelial cells and goblet cells, smooth muscle and elastic tissue

Question 14

what specialised cells do the bronchi have?

Answer 14

cartilage in irregular blocks to give structural support. Same as trachea

Question 15

what specialised cells do the bronchioles have?

Answer 15

smooth muscle, flattened epithelium, small amounts of cartilage

Question 16

what specialised cells do alveoli have?

Answer 16

thin layer of squamous epithelial cells, some collagen, elastic fibres (to stretch as air is drawn in and squeeze air out when they return to original size)

Question 17

what are the main adaptations of the alveoli for effective gaseous exchange?

Answer 17

•Large surface area- 300~500million alveoli per adult lung giving a combined SA of 50~75m^2.

Question 18

what is ventilation?

Answer 18

mechanism of breathing which involves diaphragm and antagonistic interactions between intercoastal muscles bringing about pressure changes in thoracic cavity

Question 19

why is ventilation important?

Answer 19

maintains steep concentration gradient for gas exchange

Question 20

what is lung surfactant?

Answer 20

chemical mixture containing phospholipids and hydrophilic and phobic proteins which coats the surfaces of the alveoli and prevents them collapsing after every breath

Question 21

what is the thorax?

Answer 21

the chest cavity

Question 22

describe the process of inspiration (energy using process)

Answer 22

•diaphragm contacts, flattening and lowering.
•external intercostal muscles contract moving the ribs upwards and outwards.
•the volume of the thorax increases so pressure in the thorax is reduced to lower than atmospheric pressure.
•air is drawn in down the respiratory tract equalising the pressure inside and outside the lungs

Question 23

describe the process of expiration (passive process)

Answer 23

•muscles of diaphragm relax so it’s moves upwards into a dome shape
•external intercostal muscles relax so ribs move downwards and inwards under gravity.
•elastic fibres in alveoli return to normal length
•volume of thorax decreases so pressure in thorax increases above atmospheric
•air moves out of the lungs until pressure is equal inside and outside

Question 24

what are three common ways of measuring breathing?

Answer 24

•peak flow meter
•vitalographs
•spirometer

Question 25

what is a peak flow meter?

Answer 25

simple device to measure the rate at which air can be expelled from the lungs

Question 26

what is a vitalograph?

Answer 26

the patient breathes out as quickly as possible and the instrument produces a graph of the amount of air they breath out and how quickly it is breathed out

Question 27

what is a spirometer?

Answer 27

measures different aspects of lung volume and investigates breathing patterns

Question 28

what is the tidal volume?

Answer 28

volume of air that moves into and out of the lungs with each rating breath. it is around 500cm3 in most adults at rest (~15% vital capacity)

Question 29

what is the vital capacity?

Answer 29

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

Question 30

what is inspiratory reserve volume?

Answer 30

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

Question 31

what is expiratory reserve volume?

Answer 31

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

Question 32

what is residual volume?

Answer 32

volume of air that is left in the lungs when you have exhaled as hard as possible

Question 33

what is the total lung capacity?

Answer 33

sum of vital capacity and residual volume

Question 34

what is the breathing rate?

Answer 34

number of breaths taken per minute

Question 35

what is ventilation rate and how do you work it out?

Answer 35

•it is the volume of air inhaled in one minute •ventilation rate = tidal volume x breathing rate

Question 36

what are spiracles?

Answer 36

small openings along the thorax and abdomen of an insect that open and close to control the amount of air moving in and out of the gas exchange system and the level of water loss from the exchange surfaces.

Question 37

what are the tracheae of insects?

Answer 37

largest tubes in insect respiratory system up to 1mm in diameter and they carry air into the body

Question 38

what are insect tracheae lined with?why?

Answer 38

spirals of chitin which keep them open if they are bent or pressed, it is relatively impermeable to gases so gaseous exchange cannot occur here

Question 39

what are the tracheoles in insects?

Answer 39

small tubes of 0.6-0.8 micrometres. each tracheole is a single greatly elongated cell with no chitin so they are freely permeable to gaseous exchange(it is the main site)

Question 40

what is tracheal fluid?

Answer 40

fluid located towards the end of the tracheoles in insects that helps control the SA available for gas exchange and water loss.

Question 41

what are some alternative methods of increasing gaseous exchange in insects that isn’t opening and closing of spiracles?

Answer 41

•mechanical ventilation of tracheal system- movements of the abdomen or thorax actively pumping air in out due to pressure changes •collapsible enlarged tracheae or air sacs which act as reservoirs- increase the amount of air moved through the gaseous exchange system.

Question 42

how much more dense and viscous is water than air?

Answer 42

water is 1000x more dense than air and 100x more viscous having a much lower oxygen content

Question 43

how are bony fish adapted for gaseous exchange?

Answer 43

they cannot meet oxygen demands from diffusion alone due to SA:V. they have gills to allow water to move in one direction only

Question 44

how are gills adapted for gaseous exchange exchange?

Answer 44

•large SA •good blood supply •thin layers

Question 45

what are gills?

Answer 45

gaseous exchange organs of fish comprised of gill plates, gill filaments and gill lamellae

Question 46

what is the operculum?

Answer 46

bony flap covering the gills of bony fish. part of the mechanism that maintains a constant flow of water over the gas exchange surfaces

Question 47

what are gill filaments?

Answer 47

they occur in large stacks and need a flow of water to keep them apart, exposing the surface area needed for gaseous exchange

Question 48

what are gill lamellae?

Answer 48

have rich blood supply and large SA and they are the main site of gaseous exchange in fish

Question 49

what is the biggest challenge of gills?

Answer 49

need a continuous flow of water for gas exchange

Question 50

how do cartilaginous fish such as sharks ventilate the gills?

Answer 50

they rely on continuous movement known as ram ventilation.

Question 51

how have bony fish evolved to not rely on movement to ventilate the gills?

Answer 51

pressure changes such as inhalation and exhalation of mammals

Question 52

describe how bony fish intake water when stationary.

Answer 52

Intake of water- mouth is opened and floor of buccal cavity is lowered. this increases the volume and decreases the pressure so water moves in. at the same time the opercular valve is shut and the opercular cavity containing the gills expands. this lowers pressure and the floor of the buccal cavity moves up increasing the pressure there so water from the buccal cavity moves over the gills

Question 53

describe how bony fish maintain a flow of water over the gills.

Answer 53

The mouth closes, the operculum opens and the sides of the opercular cavity move inwards. All of these actions increase the pressure in the opercular cavity and force water over the gills and out of the operculum. The floor of the buccal cavity is steadily moved up, maintaining a flow of water over the gills.

Question 54

what do the tips of adjacent gill filaments overlapping do?

Answer 54

increase resistance to the flow of water over the gill surfaces and slows down the movement of water to create more time for gas exchange to take place

Question 55

what does countercurrent flow in the gils mean? and what does it do?

Answer 55

•blood and water flow in opposite directions •this allows for steeper concentration gradients to be maintained and allows bony fish to remove around 80% of oxygen from water compared to about 50% in cartilaginous fish with parallel systems