mammalian ventilation

Question 1

outline the path that air takes as it is inhaled

Answer 1

nasal passage - trachea - bronchi - bronchioles - alveoli

Now They Breathe Big ‘Ah’s

Question 2

3 adaptations + functions of the nasal passage

Answer 2

• rich blood supply warms air as it enters nose
• hairy lining + mucus secretion traps dust and pathogens
• moist surface so air is humid, also prevents water loss in alveoli

Question 3

2 adaptations + functions of trachea

Answer 3

• C shaped rings of cartilage ensure air channel is always open, as it is able to bend when swallowing food, also provides support
• lined with ciliated epithelial cells + goblet cells which prevent dust and pathogens from entering body

Question 4

outline the structure of the bronchi

Answer 4

these are extensions of the trachea that split into 2 for the left and right lung
they have similar structures to the trachea only smaller

Question 5

2 adaptations + functions of bronchioles

Answer 5

• diameter is <1mm so short diffusion distance
• lined with a thin layer of squamous epithelial cells that facilitated gas exchange as there is a short diffusion distance - this is the first point where gas can be exchanged

Question 6

7 adaptations + functions of alveoli which make it an efficient exchange surface

Answer 6

• alveoli walls are made of 1 layer of squamous epithelial cells which decreases diffusion distance
• walls also contain collagen + elastic fibres allowing alveoli to recoil, helping air move out of sacs
• lungs contain many alveoli so high SA:V, large SA for O2 to diffuse across which increases diffusion rate
• rich blood supply due to extensive capillary network, blood here has a high [CO2] and a low [O2], concentration gradient increases rate of diffusion - CO2 can diffuse out of blood to be exhaled
• ventilation from breathing also maintains concentration gradient
• moist walls allow gases to dissolve so they can diffuse quickly
• alveoli are coated in liquid surfactant which lowers surface tension at air/liquid interface, ensuring alveoli doesn’t collapse, as well as killing pathogens + preventing them from entering lungs

Question 7

what are alveoli

Answer 7

little sacs of air where most gas exchange occurs
diameter is 200-300 micrometers

Question 8

why are respiratory infections so common

Answer 8

alveoli + lungs are warm, moist environments with high [O2] and rich blood supplies, which is a prime environment for bacteria

Question 9

what occurs during inspiration

Answer 9

• diaphragm moves down
• intercostal muscles move up + out
• thoracic volume increases so thoracic pressure decreases
• air flows into lungs to equalise pressure difference between air outside lungs and inside lungs

Question 10

what occurs during expiration

Answer 10

• diaphragm moves up
• intercostal muscles move down + in
• thoracic volume decreases so thoracic pressure increases
• air flows out of lungs to equalise pressure difference between air inside lungs and air outside lungs

Question 11

ventilation rate definition + calculation

Answer 11

the total amount of air moved into the lungs in 1 minute
tidal volume x breathing rate

Question 12

total lung capacity =

Answer 12

residual volume + vital capacity

Question 13

residual volume definition

Answer 13

the volume that stays in lungs after forced exhalation

Question 14

vital capacity definition

Answer 14

the volume of air exchanged between maximum and minimum inspiration

Question 15

vital capacity =

Answer 15

inspiratory reserve volume + expiratory reserve volume + tidal volume

Question 16

tidal volume definition

Answer 16

volume breathed in and out in a single breath

Question 17

what is a spirometer

Answer 17

these measure the volume and speed of a gas breathed in and out of the lungs
- they can be used to assess asthma, pulmonary fibrosis, cystic fibrosis and COPD
- they produce spirographs

Question 18

why is it not possible to expel all air from the lungs

Answer 18

the thorax cannot be completely flattened, as the trachea and bronchi are held open by cartilage

Question 19

why are specialised exchange surfaces needed by some organisms

Answer 19

• helps to compensate for a low SA:V, as exchange surfaces have very high SA:V
• maximises efficiency of diffusion
• ensures the demand to O2 and glucose is met

Question 20

4 features of an efficient exchange surface

Answer 20

• high SA:V
• thin layers/walls
• good blood supply to maintain conc gradient
• ventilation to maintain a conc gradient

Question 21

breathing definition

Answer 21

the movement of air in and out of the lungs

Question 22

gas exchange definition

Answer 22

the delivery of O2 from lungs into bloodstream and the elimination of CO2 from the blood stream

Question 23

what occurs during forced expiration

Answer 23

• abdominal muscles contract, pushing diaphragm up
• this quickly makes lung pressure less negative
• internal intercostal muscles contract, pulling ribs down hard + fast

Question 24

what is inspiration

Answer 24

movement of air into the lungs
this requires energy

Question 25

what is expiration

Answer 25

the movement of air out of the lungs
this is a passive process

Question 26

3 ways to measure lung capacity

Answer 26

• peak flow metre
• spirometer
• vitalographs

Question 27

how does O2 get from the alveoli into the blood

Answer 27

dissolves into moist walls and diffuses from alveoli into capillaries down a concentration gradient