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32 Cards in this Set

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What is Fick's Law? What do the letters stand for?

Rate of diffusion Q = ^P.A.D/ ^X


P is partial pressure grad. of gas


A is surface area for gas


D is diffusion coefficient


X is distance

In Fick's Law, what is the diffusion coefficient?

Theamount of a particular substance that diffuses across a unit area in 1 s underthe influence of a gradient of one unit.


Usually expressed in the unitscm^2s-1.

What is the difference in diffusion into tissues between air and water?


What does this mean for air and water breathers?

Diffusionis much faster in air than in water (by about 8000-times) so diffusion requiresmuch less time for equilibration in air than in water.


Air-breathersexperience fewer problems with depleting the O2 supply but the final aquatic diffusion phase can be rate limiting. However, this can be more of a problem forwater-breathers

For good diffusion you need?

A large surface area


A thin permeable surface


A moist exchangeable surface

How can rate of diffusion be enhanced?

Bybulk transport i.e. ventilating respiratory surface by convection and by circulation of blood - both of which maximise the diffusion gradient

Describe fish gill structures.

Each gill is supported by a gill arch and protected by gill rakers - the gill rakers ensure no extraneous material clogs the gill filaments. Each gill arch supports one set of paired gill filaments.


Each paired gill filament in turn supports numerous lamellae (the actual gas exchange surfaces)

How is gas exchange effected by how active a fish is?

The more active a fish, the more effective the gas exchange

Describe the ventilation process in a standard fishy fish.

Ventilation operates by a cycle of negative and positive pressure gradients. As the mouth opens, the opercula are shut leading to a negative pressure gradient in the buccal and opercular cavities driving “oxygen rich” water into the mouth. As mouth closes the opercular cavity constricts forcing the water over the gills which are at positive pressure to the water outside.When the opercula open the positive pressure gradient forces water outwards across the gills and through the opercular exit.

How is the transfer of gas from water to blood maximised in fish?

The flows of each operate in a counter current system. Blood moving through the lamellae continually encounters water at high partial pressure than that in the capillary. This system maintains a positive partial pressure gradient for diffusion throughout the gill.

What do fish who have lost their respiratory muscles do about the whole breathing business?

Use ram ventilation: bulk transport is created by forward motion whilst the mouth and opercula are held slightly open. Fish cannot stop swimming. Ventilation volume is increased by increasing mouth gape and swim speed.

How is respiration in sharks unique?

They do not have an operculum, or an opercular cavity but have a series of branchial flaps, one for each set of gills. They also have a pair of spiracles in front of their gills that pump water in through and over their gills.

Name at least three non-respiratory functions of the gill, name more if you're feeling clever.

The respiratory system is greatest contact point between external and internal environments.




Gills can be feeding structures -the gill rakers capturing plankton e.g. herring and anchovies.




Gills are important osmoregulatory organs for water levels and ion content any increase in ventilation may also increase ion loss and water intake (FW ) or vice versa (SW).




Gills are also important in acid base balance by transporting H+ or HCO3-.




Gills are also sites of waste product excretion e.g. Ammonia.




Gills play a role in nutrient uptake e.g. calcium.

Describe the process of bucal pumping action in frog respiration.

In adults during inspiration:


a)the frog lowers the floor of the mouth and inhales air through the nostrils into the buccal cavity. The nostrils are then closed


b)the glottis opens and the floor of the mouth raised to force air into thelungs.


c)gas exchange occurs across the lungs. The nostrils open at the end of this phase.


d)air is forced out the lungs when muscles in the body wall above/below the lungs contract and the lungs elastically recoil.


• Lung filling requires several successive inflation cycles, whereas lung deflation is usually accomplished bya single expiration.

As turtles can't use ribs to ventilate lungs, how do turtles respirate?

• Lungs are connected to viscera -muscles thatcontract to force the viscera up to expel air; other muscles increase the volume of the visceral cavity allowing the viscera to settle down, expanding the lungs.


• The pharynx of soft shelled turtles contains fringe-like structures used for underwater respiration.

Describe the method crocodiles use to respirate?

• Crocodilians have lungs with alveoli and possess a unique muscle called the diaphragmaticus that attaches to the liver and viscera and acts as ‘a piston’ to assistin breathing


• Muscles between the ribs are used to both increase and decrease thoracic volume.


• Inspiration involves contraction of the diaphragmaticus muscle - push organs to back of body


• Expiration is accomplished by contracting different muscles - decrease abdominal volume.

How are bird respiratory systems unique?

They have relatively small lungs plus 9 air sacs

What is the purpose of air sacs in a birds respiratory system?

They permit a unidirectional flow of air through lungs and act as 'bellows'. This means that air moving through bird lungs is mostly 'fresh' and has a higher O2 content.

Name the 9 types of air sac found in a birds respiratory system. (Only 5 names as 4 of the sacs have pairs)

Cervical air sacs - 2


Interclavicular air sac - 1


Anterior thoracic air sacs - 2


Posterior thoracic air sacs - 2


Abdominal air sacs - 2

What are the components that make up a birds lung?

Parabronchi are a series of small tubes extending between larger dorsobronchi and ventrobronchi – forming the lung. Both are connected to the intrapulmonary bronchus which is linked to the trachea.

Order the different taxa - reptiles, amphibians, mammals and birds - by comparing the mean thickness of blood-gas barriers starting with the thinnest.

Birds, mammals, reptiles, amphibians

Why is the gas exchange system of mammals designed the way it is?

To sustain high metabolic rates

List at least three non-respiratory functions of the respiratory systems in mammals.

• Alter the pH of blood by facilitating alterations in the partial pressure of CO2.


• Filter out small blood clots formed in veins.


• Filter out gas micro-bubbles occurring in the venous blood stream such as those created during decompression after diving.


• Maintain sterility by producing mucus containing antimicrobial compounds.


• Ciliary escalator action is an important defence system against air-borne infection.

How are dust and other impurities expelled from the respiratory systems of mammals?

•The trachea is lined with mucus secreting goblet cells for lubrication and to trap dust particles and other impurities. Epithelial cells with cilia pushthis material up and out of the trachea

Describe the anatomy of lungs in mammals.

Trachea - supported by cartilage rings- divides into left and right bronchi, each one entering a different lung


Bronchus - supported by cartilage rings- branch out further, into bronchioles


Bronchioles - contain smooth muscles innervated by the ANS - at the ends of these there are alveoli.

What types of cells will you find in the alveoli? Describe their purpose.

Type I epithelial cells: thin wall forming


Types II epithelial cells: secrete pulmonary surfactant, a phospholipoprotein complex that facilities alveolar expansion. It also reduces the surface tension more in small alveoli so that their collapsing pressures match that of large alveoli.

What is the 'Law of LaPlace' and how do alveoli overcome this?

• If 2 alveoli of unequal size, but the same surface tension are connected by a common airway – the smaller one empties into the larger one because it has a larger inward pressure -possible collapse.


• Pulmonary surfactant reduces the surface tension more in the small than large alveolus so that their collapsing pressures are now similar

How can lung volumes be measured?

Using a spirometer

What is the equation used to assess pulmonary ventilation?

Pulmonary ventilation (L/breath) = Tidal volume (L/min) x Respiratory rate (breath/min)

When increasing pulmonary ventilation, it is better to have a greater increase in what? Why is this?

• It is better to have a greater increase intidal volume than respiratory rate because of the presence of anatomic dead space. Dead space is the result of the fact that not all inspired air reaches the site of gas exchange in the alveoli.

How do you calculate alveolar ventilation (or dead space)?

Alveolar Ventilation (AV) = (TV - dead space) x Respiratory Rate (RR)


Tidal vol. (TV) = volume moved in and out with each breath

What is the difference between the proportion of O2 and CO2 in alveolar air compared to the proportion of O2 and CO2 in atmospheric air?




How do these partial pressure gradients affect gas exchange in the mammalian respiratory system?

PO2 is 100mm Hg in alveoli and 160mm Hg in air.


PCO2 is 40mm Hg in alveoli and 0.2mm Hg in air.


These partial pressure gradients promote gas exchange.

How is respiration controlled in mammalian systems?

- Reflexes regulating lung inflation


- Ventilation of lung by diaphragm and muscles between ribs


- These muscles are activated by spinal motorneurons and the phrenic nerve


- Phrenic nerve receives input from neurons which constitute the medullary control centres.


- Basal rhythmic activity is maintained by pneumotaxic centre in pons


- Rate and depth of breathing altered by changes in O2, CO2, pH of blood, sleep, lung irritation, environmental factors - these are integrated by the medullary control centres.


- The medullary control centre senses these changes using chemoreceptors