lecture 11-12

Question 1

Why do we need respiratory gases ?

Answer 1

animals must exchange respiratory gases -O2 &CO2
-cell needs O2 from environment for cellualr respiration –>to prod ATP
-No O2 :Pyruvate oxidation ,citric acid cyle and oxidative phosphorylation do not function
-Anaerobic function is much less efficient than aerobic respiration as less ATP is made

Question 2

Define External respiration ?

Answer 2

Process by which O2 needed for energy metabolism is obtained CO2 is eliminated
-gas exchanfe pf O2 & CO2 between pumonary blood (mammals)

Question 3

What does gas exchange of animals consist of ?

Answer 3

1.Specialised body surface areas where gases can move between the body internal and external environment
2.Mechanisms that ventilate the environmental/external side of surfaces with air/water
3.Mechanisms that circulate ECF on internal sides

No active transport mechanisms to move respiratory gases across biologic

No active transport mechanisms to move respiratory gases across biological membranes –>gas exchange bwteen an animals internal body fluids and outside medium occurs by diffusion

Question 4

Define solute ?

Answer 4

Solute diffuses from regions of a solution where it is high in concentration to where it is low

Rate of solute diffusion is proportional to its difference in concentration between regions

Question 5

Define Chemical potential ?

Answer 5

strength of the tendancy of a chemical substance to undergo a physical/chemical change study of chemical diffusion

Question 6

Define diffusion

Answer 6

with a single aqeous solution the concentration of a solute is a usefull surrogate for chemical potential)
-However O2 & CO2 exist in both gas mictures and aqeous solutions they diffuse between them
so partial pressure is used to express chemical potential in the study of gases

Question 7

Define universal law

Answer 7

PV=nRT

Question 8

Define Daltons law of partial pressure ?

Answer 8

:The total pressure exerte by mixture of gases is = to the sum of the partial pressures of all the gases of the mixture

Question 9

Define partial pressure ?

Answer 9

the individual pressure exerted by any given gas in gas mixture

Partial pressure of each indivisual gas in a mixture can be calculated from the universal gas law

Question 10

Define Henrys law ?

Answer 10

amount of gas dissolved in a given volume of liquid is proportional to the partial pressure in the gas phase .Proportionally constant is called -solubility coefficient

relates PP and conc in aqeous solutions
-can use absorption coefficient :dissolved concentration of a gas when partial pressure is 1 atm

Question 11

What is solubility of gases ?

Answer 11

amount of O2 that is dissolved is proportional to its partial pressure in the gas phase

Question 12

Diffusion of gases :partial pressure

Answer 12

gas in aqeous solution :not equal to partial pressure but the latter drives diffusion

Ficks law applies to all systems of gas exchange

Question 13

What does Ficks law apply to all ?

Answer 13

all systems of gas exchange :whether in air or water diffusion rates of respiratory gases depend on partial pressure gradients & other factors

Question 14

What is Ficks law ?

Answer 14

rate at which a gas diffuses between 2 locations (Q) depends on
1.diffusion coefficient (D); incorporating temp ,diffusiing substances;medium
2.Area(A) over which gas is diffusing
3.Difference between the gas partial pressure (P1-P2) at 2 locations ;
4.Distance(L) between 2 locations

all tissues ,Ficks law applies to rate of diffusion of any substance in the interstitial fluid
substance moves from plasma to tissue->passive molecules

Question 15

Animal adaptations to rate at which gas diffuses between 2 locations ?

Answer 15

Sponges-body walls contain many channels –>waterr flows into central cavity

Question 16

Specialised respiratory systems

Answer 16

in organs specalised for external respiration thr gas exchange membrane typically has extensive invaginations/evaginations to increase A(influence SA or pressure gradient

Question 17

Brief overview of insect respiratory system ?

Answer 17

Consist of branched air tubes-trachea &tracheoles that end in air capillaries
-insect tracheal systems brings air to all tissues /cells in the body :
-spiracles :enable communication between an insects internal and external environment
spiracles–>trachea,tracheoles–>air capillaries

Question 18

Where does Ventilation & Perfusion occur ?

Answer 18

Venti=(occurs on environmental side)Maintains high PO2 and low PCO2
Perf=(occurs on the internal side ;tissues/fluid)Maintains a low PO2 and high PCO2

Question 19

Define Ventilation ?

Answer 19

Bulk flow of air and water to and from the gas exchange membrane during breathing
-not all animals use ventilation ;breathing can occur by diffusion
active ventilation constantly moves external medium over gas exchange surfaces–>fresh supply of O2 and CO2

may be unidirectional,non or tidal

Question 20

Define Perfusion ?

Answer 20

Actively moves internal medium (blood) side of exchanged surfaces –>CO2 brought to these surfaces exchanged for O2

Question 21

Breathing by Fish ?

Answer 21

Teolasts buccal cavity communicates with environment via mouth and gilll slits
internal gils are supported by gill arches ;opperculum covers gills
4 gill arches :provides structuaral support for gills ;each arch bears 2 rows of gill filaments

gill are composed of gill filaments ;rows of gill filaments seperate the buccal cavity from opperculum cavity

Question 22

Breathing by fish ?

Answer 22

Each gill filament vears a series of folds:secondary lamallae –>richly perfused with blood ;thin welled
lamallae are principle sites of gas exchange in teleosts
gills–>enormous SA for gas exchange highly subdivided
water flows unidirectionally into mouth across gills out opperculum flaps -flow is either :
1.constant swimming wiht mouth open (tuna,sharks) some must to avoid suffocation
2.most fish ventilate their gills via 2 -pump mechanism
-buccal -opperculum pumping :mouth cavity closes& contracts

Question 23

How does countercurrent gas exchange occurs in lamallae of fish ?

Answer 23

Blood flows in via the afferent vessels (deoxy),across lamllae & out via the efferent vessels .
-Blood flows is also unidirectional ;but in the opposite direction to water low –>countercurrent

gas exchange rate is maximised by maintaining the PO2 gradient between water and blood using countercurrent system

Question 24

What is the difference between unidirectional ventilation :concurrent and countercurrent ?

Answer 24

figure show flow of medium and flow of blood along gas exchange membranes
concurrent/cocurrent~:flow of medium and blood occurs in same direction
countercurrent:medium and blood flow in opposite directions
acheives more complete transfer of O2 from medium to blood than ccurrent exchange :thus is more efficient /effective

Question 25

What are adaptations of fish for respiration ?

Answer 25

Fish maximise gas exchange rate (Q)
-highly subdivided and folded SA –> maximise A
-very thin surface
-maintain high P1 through an almost constant unidirectional water flow and low PO2 through constant blood flow
countercurrent system maintains PO2 gradient –>enables fish to obtain adequate O2 supply from meagre sources

Question 26

Any problems that may affect fish and their respiratory adaptations ?

Answer 26

high temperature :
casue respiratory problems for aquatic animals -fishy
-rising water temp increaes the animals metabolic rate thus needs more O2 but warmer water holds less O2Needs to move more water
across gas exchange surface
→ uses more energy…
Recap: air is a better
respiratory medium
than water (slide 17).
Animal needs more O2, but less is
available

Question 27

Breathing by birds ?

Answer 27

allows air to flow unidirectionally:very little dead space freshair does not mix with stale air –>maintains high PO2
-air sacs :part of breathing system but are located outside of the lungs in thoracic cavity
usually 9,2 groups anterior and posterior

Question 28

What are birds air sacs connected with ?

Answer 28

interconnected with each with the lungs and with air spaces in some of ther bones
-non-respiratory :are not gas exchange surfaces
-act as bellows:maintains unidirectional flow of air through lungs

air in through trachea →primary bronchi→secondary bronchi→parabronchu

Question 29

what are parabronchi and what do the do ?

Answer 29

tertiary bronchi
air diffuses into tiny air capillaries which are the gas exchange surfaces
air capillaries: surrounded by blood capillaries
air flows out of lungs to anterior air sacs and finally out of bird via trachea

Question 30

How much breath remains in birds respiratoy system ?

Answer 30

single breath for 2 cycles of inhalation and exhalation
lungs ventilated by bellows action -generated by action,expansion and compressionof air sacs

Question 31

What happens in cycle 1 of bird breathing ?

Answer 31

Inhalation:air enters via trachea and drawn into posterior air sacs as they expand
During exhalation this air is then pushed into lungs
Cycle 2
during next inhalation -lungs is displaced into anterior sacs
during exhalation-air forced out via trachea

Avian lungs are compact, rigid structures: undergo minimal change in volume during a breathing cycle.

Question 32

The cross-current gas exchange occurs in air capillaries in birds ?

Answer 32

cross current (unidirectional) pattern relative to air flow
afferent blood vessel breaks into many vessels that ‘cross’ the path followed by medium merging to form a single efferent blood vessel

Question 33

What are birds respiratory adaptations ?

Answer 33

minimise gas exchange rate
many air capillaries- large SA
Air & blood capillaries -thin walls
maintain high P1-almost unidirectionally air flow through constant blood flow
maintains PO2 gradient-enabling birds to maintain blood PO2 slightly below of environmental air even at high altitude

Question 34

What is tidal ventilation ?

Answer 34

bidirectional so air flows to and from the gas exchange membranes via the same passages
Mixing with stale airs lowers PO2 grad

not as efficient as unidirectional ventilation

Question 35

Breathing by mammals ?

Answer 35

have elaborate animal lungs
densly filled with branching & rebranching :lungs=High gas exchange SA
barrie thickness between blood & environmental medium very thin

Question 36

2 major functions of mamalian areas ?

Answer 36

1.Conducting zone :moving gases to and from the atmosphere and lungs including trachea,bronchi & bronchioles
2.Respiratory zone :where gases are exchanged ->Alveoli are sites of gas exchange across alveolar capillary membrane

Question 37

What do mammals lungs end up in ?

Answer 37

dead end sacs
Trachea,bronchi &bronchioles constitute dead space
Respiratory bronchioles end blindly i alveolar ducts & sacs
Gas occupying final respiratory airways almost motionless –>O2 and CO2
transport must occur by
diffusion

Question 38

What is the role of surfactant ?

Answer 38

In alveolar epithelial type 2 cells = prod surfactant =reduce surface tension of alveoli and prevent alveoli from collapsing during exhalation
compensation for tidal ventilation =adaptations
1. large SA
2. short diffusion pathway