Exchange Surfaces and Breathing

Question 1

How does air get to lungs? Mammals

Answer 1

Air passes into lungs through the nose along the trachea, brionchi and brionchioles finally reaching alveoli
Lungs protected by ribcage which which are held together by the intercostal muscles. Action of muscles helps to produce ventilation

Question 2

Gaseous exchange in lungs

Answer 2

Gases pass by Diffusion through thin walled alveoli
Oxygen passes from air in the alveoli to blood in capillaries
CO2 passes from blood to air in alveoli
Lungs must maintain a steep concentration gradient in each direction to ensure diffusion continues

Question 3

Special features

Answer 3

Alveoli are very small, moist
Alveolus wall one cell thick 
Callipary wall one cell thick 
Consist of squamous tissue 
Capillary in close contract with alveolus walls

Question 4

Ventilation happens how?

Answer 4

Concentration of oxygen in the air of the alveolus remains higher than in blood
The concentration of carbon dioxide in alveoli remains lower than that in blood
Therefore concentration gradient necessary for diffusion is maintained

Question 5

Inspiration happens how

Answer 5

Diagraghm contracts to move down and becomes flatter displacing digestive organs downwards
External intercostal muscles contract to raise the ribs
Volume of chest cavity is increased
Pressure in chest cavity drops below atmospheric pressure
Air is moved into the lungs

Question 6

Expiration

Answer 6

Diaphragm relaxed and is pushed up by the displaced organs underneath
The external intercostal muscles relax and the ribs fall; the intercostal muscles can contract to help push air out more forcefully- this usually only happens during exercise or coughing or sneezing
The volume of chest cavity is decreased
The pressure in the lungs increases and rises above the pressure in the surrounding atmosphere
Air is moved out of the lungs

Question 7

Ciliated epithelium

Answer 7

A layer of cells that have many hair-like extensions called cilia

Question 8

Airways have to be

Answer 8

Large enough to allow sufficient air to flow without obstruction
Be supported to prevent collapse when the air pressure inside is low during inspiration
Be flexible in order to allow movement

Question 9

Ciliated epthileum

Answer 9

Lined with ciliated epthileum
Goblet cells release mucus
Ciliated move mucus up to air war where swallowed
Glandular tissue in loose tissue also produces mucus

Question 10

Trachea and bronchi

Answer 10

Similar structure
Cartilage helps stop collapse during inspiration
Allows flexibility and space for good to pass down the oesophagus

Question 11

Bronchioles

Answer 11

Narrower than bronchi
May have some cartilage
Wall comprised mostly of smooth muscle and elastic fibres
Smallest bronchioles end in clusters of alveoli

Question 12

Smooth muscle and elastic tissue

Answer 12

Smooth tissue can contract and will contrict airway
Makes lumen narrower can restrict flow of air to alveoli
Controlling airflow may be important if there are harmful substances in air
This is what happens in allergic reaction
Once contracted can’t be reversed on its own, smooth muscle is elongated again by elastic fibres
When muscle contracts it deforms elastic fibres. As muscles relax, elastic fibres recoil to original size and shape. Dilutes airway.

Question 13

Spirometer

Answer 13

Device can measure tidal volume, vital capacity, breathing rate and oxygen uptake

Question 14

How does a spirometer work?

Answer 14

Spirometer has oxygen filled chamber with moveable lid
Person breathes in and out lid of chamber moves up and down
Movements can be recorded by pen attached to rotating drum creating spirometer trace. Spirometer can be hooked up to motion sensor- this will use movements to produce electronic signals which are picked up by data logger. Soda lime in tube the subjects breathes into carbon dioxide

Question 15

What are the three important features of an exchange surface?

Answer 15

Size- diffusion only works in smaller animals
surface area to volume ratio- if it too small diffusion is ineffective
Level of activity- the move activity the more oxygen required so more likely not to be able to use diffusion
Good blood supply- allows it to travel to the rest of the body

Question 16

Precautions that must be taken when using spirometer

Answer 16

Subject should be healthy especially free from asthma
Soda lime should be fresh and functioning
No air leaks in appartus as would give invalid/inaccurate results
Mouthpiece should be sterilised
Water chamber must not be overfilled (or water may enter air tubes)

Question 17

Modern spirometer can be

Answer 17

Small and simple hand held devices
Record movement of air in and out of lungs
Can’t be measured by rate of oxygen consumption

Question 18

Vital capacity what is it?

Answer 18

Maximum volume of air that can be moved by the lungs in one breath, measured by taking deep breathe and expiring all air possible from lungs

Question 19

Vital capacity depends upon

Answer 19

Size of person
Age and gender
Level of regular exercise
Usually in region of 2.5-5 but may increase in trained athletes

Question 20

Residual volume is

Answer 20

Volume of air that remains in lungs even after forced expiration. Air remains in airway and alveoli approximately 1.5dm3

Question 21

Tidal volume is

Answer 21

Volume of air moved in and out with each breath normally measured at rest typical tidal volume at rest might be 0.5 dm3. Usually sufficient to supply all oxygen required in the body at rest

Question 22

Oxygen uptake

Answer 22

As person breathes from spirometer oxygen absorbed by blood replaced by CO2. CO2 is absorbed by soda lime in spirometer volume of air decreases
Decrease can be observed and measured on spirometer trace
Assume volume of carbon dioxide released and absorbed by soda lime equals the volume of oxygen absorbed by blood. Meaning gradient of decrease in blood enables us to calculate rate of oxygen uptake.

Question 23

How to measure oxygen uptake?

Answer 23

Draw line down in two places on graph and measure time
Measure difference of volume between points
Divide by time taken for decrease
Rate of oxygen uptake = difference in volume / difference in time

Question 24

Breathing rate can be measured by spirometer how?

Answer 24

Count number of peaks in each minute

Question 25

Oxygen uptake depends upon

Answer 25

Higher demand such as exercise when muscles are realising more

Question 26

Increased oxygen uptake can result from?

Answer 26

Increased breathing rate

Deeper breaths

Question 27

Bony fish respiration works how?

Answer 27

They use gills to absorb oxygen dissolved in water and release carbon dioxide into water
Oxygen concentration typically will be lower than that in air
Most bony fish have five pairs of scales which are covered by bony plate called operculum

Question 28

Describe bony fish gills

Answer 28

Each gills consists of two rows of gill filaments (primary lamellae) attached to bony arch
Filaments are very thin surface attached into many secondary lamellae (Gill plates)
Provides large surface area , blood capillaries carry deoxygenated blood close to the surface of the secondary lamellae where exchanged take place

Question 29

Countercurrent flow

Answer 29

Blood flows along gill arch and out along filaments to secondary lamellae.
Blood flows through capillaries in opposite direction to flow of water over lamellae
Arrangement creates countercurrent flow that absorbs maximum amount of oxygen from water

Question 30

Ventilation in bony fish

Answer 30

Can keep water flowing through gills by using a buccal-operculum pump
Buccal cavity can change volume
Floor of mouth moves downwards drawing water into buccal cavity
Mouth closes and floor is raised again pushing water through gills
Movement of operculum coordinated with movement of buccal cavity
Water pushed from buccal cavity operculum moves outwards
Movement reduces pressure in opercular cavity helping water to flow through gills

Question 31

How do insects transport blood around body

Answer 31

Not in blood
Open circularity system in which body fluid acts as blood and tissue fluid
Circulation flow slow
Affected by body movement

Question 32

How does the insects get air directly to all respiring tissues?

Answer 32

Air filled tracheal system
Air enters the system via a pore called a spiracle (little hole).
Air transported into body through series of tubes called tracheae
Divide into smaller and smaller tubes called tracheoles
Ends of tracheoles are open and filled with tracheal fluid
Gaseous fluid occurs between air in tracheoles and tracheal fluid. Some exchange can occur across thin walls of tracheoles

Question 33

How do insects get more oxygen when moving?

Answer 33

Most insects are very active and need a good supply of oxygen
When tissues are active the tracheal fluid can be withdrawn into body fluid to increase surface area of tracheole wall exposed to air
Means more oxygen can be absorbed when insect is active

Question 34

Ventilation in insects what do parts of tracheal systems act as?

Answer 34

Many insects have sections of tracheal systems expanded have flexible walls. Act as air sacs can be squeezed by action of flight muscles. Repetitive expansion and contraction of sacs ventilate tracheal system

Question 35

Movement of wings affect insect how?

Answer 35

Movement if wings alter volume of thorax
As volume decreases air in tracheal systems under pressure and is pushed out of tracheal system
When thorax increases in volume
Pressure inside drops and air is pushed into tracheal system from outside

Question 36

How have some insects developed ventilation further?

Answer 36

Locusts can alter volume of abdomen by specialised breathing movement
Coordinated with opening and closing valves in spiracles
As abdomen expands spiracle at front end of body open and air enters tracheal system
As abdomen decreases in volume the spiracle at the rear end of the body open and air can leave the tracheal system