Exchange surfaces and breathing Flashcards
1
Q
What are the 3 main factors that affect the need for an exchange system?
A
- size
- surface area to volume ratio
- level of activity
2
Q
How does size affect the need for an exchange system?
A
- small organisms (single celled) can receive a sufficient supply of oxygen from environment by diffusion
- for multicellular organisms diffusion is too slow to enable sufficient supply to innermost cells
3
Q
How does SA:V affect the need for an exchange system?
A
- small organisms have a large SA:V, SA is large enough for sufficient oxygen to diffuse into all cells.
- large organisms have small SA:V
4
Q
How does level of activity affect the need for an exchange system?
A
- some organisms are more active than others
- cells of active organism need good supplies of nutrients and oxygen to supply energy for movement
- organisms (mammals) that keep themselves warm need more energy.
5
Q
What are the features of a good exchange surface?
A
- large surface area to provide more space for molecules to pass through. Walls are often folded (root hair cells).
- permeable and thin barrier to reduce diffusion distance (alveoli)
- good blood supply to maintain steep conc gradient for fast diffusion ( and removal of metabolic waste products that can be toxic)
6
Q
What are alveoli?
A
tiny folds of the lung epithelium to increase the SA
7
Q
What’s the trachea?
A
main airway leading from the back of the mouth to the lungs
8
Q
What are bronchi and bronchioles?
A
smaller airways leading into the lungs
9
Q
What’s the diaphragm?
A
layer of muscle beneath the lungs
10
Q
What are intercostal muscles?
A
muscle between the ribs
11
Q
What’s ventilation?
A
the refreshing of the air in the lungs so there’s a higher oxygen concentration than in blood, and lower carbon dioxide conc for fast diffusion
12
Q
Why are alveoli so numerous?
A
large SA to provide more space for molecules to pass through
13
Q
Why does surfactant coat internal surface of alveoli?
A
- to reduce the cohesive forces between water molecules as they make alveoli collapse
- also helps gases dissolve
14
Q
What the barrier to exchange comprised of?
A
- wall of alveolus
- wall of capillary
- cells readily allow diffusion of oxygen and carbon dioxide as they’re small and non polar
15
Q
How is the barrier to exchange thin to reduce diffusion distance?
A
- alveolus and capillary walls are one cell thick
- both consist of squamous epithelium (flattened or very thin cells)
- capillary in close contact with alveolus wall
- capillaries have narrow lumen so RBCs are close to air in alveoli.
16
Q
Why is it important for blood to carry carbon dioxide from tissues to lungs?
A
ensures conc gradient of CO2 in blood is higher than that in air in alveoli so carbon dioxide diffuses into alveoli
17
Q
Why is it important for blood to carry oxygen away from lungs?
A
ensures that the conc of oxygen in blood is kept lower than that in alveoli so oxygen diffuses into the blood
18
Q
Explain inspiration
A
- diaphragm contracts to move down and becomes flatter (this displaces the digestive organs downwards)
- external intercostal muscles contract to raise ribs
- volume of chest cavity increases
- pressure in chest cavity drops below atmospheric pressure
- air moves into the lungs
19
Q
Explain expiration
A
- diaphragm relaxes and moves upwards (is pushed up by displaced organs underneath)
- external intercostal muscles relax and ribs fall
- during exercise, coughing, sneezing, internal intercostal muscle contract to push air out more forcefully
- volume of chest cavity decreases
- pressure in lungs rises above atmospheric pressure
- air is moved out of lungs
20
Q
What kind of fibres do alveoli contain and why?
A
- elastic fibres help them stretch during inspiration but then recoil to help push air out doing expiration
21
Q
What must airways have to be effective?
A
- be large enough to allow sufficient air to flow in without obstruction
- be supported to prevent collapse when the air pressure inside is low during inspiration
- be flexible in order to allow movement
22
Q
What do airways contain?
A
- lined by ciliated epithelium, keeps lungs healthy
- goblet cells in epithelium release mucus to trap pathogens
- cilia move mucus to top of throat where it’s swallowed
- glandular tissue in the loose tissue also produces mucus
- supported by C-shaped rings of cartilage to prevent collapse during inspiration
- C-shaped rings allow flexibility for food to pass down oesophagus
23
Q
Difference between trachea and bronchi?
A
- similar wall structure but bronchi are narrower
24
Q
Features of bronchioles
A
- much narrower than bronchi
- smaller ones don’t have cartilage
- wall made of smooth muscle and elastic fibres
- smallest ones end in clusters of alveoli
25
Explain contraction of smooth muscle in airways
- constricts airways
- lumen becomes narrower
- restricts airflow to and from alveoli
- important if there's a harmful substance in the air
- not voluntary (may be allergic reaction)
- can't be reversed on its own
- smooth muscle elongated again by elastic fibres
- elastic fibres **deformed** (during contraction) then **recoil** (during muscle relaxation), dilating the airway
26
What's a spirometer?
- device that can measure the movement of air into and out of the lungs
27
What's vital capacity?
maximum volume of air that can be moved by the lungs in one breath
28
What's tidal volume?
the volume of air inhaled or exhaled in one breath, usually measured at rest
29
What's oxygen uptake?
volume of oxygen absorbed by the lungs in one minute
30
What's residual volume?
volume of air that remains in the lungs even after forced expiration
31
What factors can affect vital capacity?
- size of person (height)
- age and gender
- level of regular exercise
32
How to calculate oxygen uptake from a spirometer trace?
- as person breathes from the spirometer, O2 is absorbed by blood and replaced by CO2
- CO2 absorbed by soda lime in spirometer so volume of air in chamber decreases.
- assume volume of carbon dioxide released during expiration and absorbed by soda lime equals the volume of oxygen absorbed by blood
- measure gradient of the decrease in volume
33
How to calculate breathing rate from spirometer trace?
- count number of peaks in each minute
34
What factors can increase oxygen uptake?
- exercise
- increased breathing rate
- deeper breaths
35
equation for pulmonary ventilation rate
PVR = tidal volume x breathing rate
36
What's the buccal cavity?
the mouth
37
What's counter current flow?
blood flows through capillaries in gill filament in opposite direction to flow of water over lamellae for maximum absorption of oxygen from water as there's a steep conc gradient
38
what are gill filaments/primary lamellae?
slender branches of tissue that make up the gill
39
what is secondary lamellae/gill plate?
folds of the gill filament to increase SA
40
what's the operculum?
bony flap that covers and protects gills
41
How many pairs of gills in bony fish?
5
42
Structure of gills and advantages of this
- two rows of gill filaments (primary lamellae) attached to a bony arch.
- filaments are very thin and their surface is folded into many secondary lamellae (or gill plates)
- provides large SA
- blood capillaries carry deoxygenated blood close to surface of secondary lamellae where exchange occurs
43
How does ventilation in fish occur?
- floor of buccal cavity moves downward drawing water inside
- mouth closes, floor raised pushing water through the gills
- operculum moves outwards which reduces pressure in the **opercular cavity** (space under the operculum) helping water flow through gills
44
define tracheal system?
system of air-filled tubes in insects
45
define tracheal fluid
fluid found at the end of tracheoles in the tracheal system
46
what's a spiracle?
pore that allows air in or out of trachea
47
Describe the circulatory system in insects
- open circulatory system where body fluid acts as both blood and tissue fluid
- circulation is slow and affected by body movements
48
How does gaseous exchange occur in insects?
- occurs between air in tracheole and the tracheal fluid
- some exchange occurs across thin walls of the tracheoles
-tracheal fluid withdrawn into body fluid to increase SA of tracheole wall exposed to air for more diffusion of oxygen in very active insects
49
How is the tracheal system ventilated?
- abdominal muscles contract and relax, changing volume of their bodies and move air in and out of spiracles
- when larger insects are flying, wing movements pump their thoraxes too.
50
adaptations of tracheal system
- large SA:V - many branching tracheoles
- short diffusion distance - many branching tracheoles reach muscle and thin-walled tracheoles
- maintaining a conc gradient - when cells respire, they use O2 and produce CO2. Abdominal muscles contract to pump air
