Download - Gaseous Exchange System

7/28/2019 Gaseous Exchange System

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Human Respiratory System


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Gaseous Exchange

This process involves the passage of gases

such as oxygen into, and carbon dioxide out of

cells or a transport system.

First, air needs to be in contact with the

gaseous exchange surface

This is achieved by breathing

See picture over the page of the respiratory

system


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http://wikieducator.org/File:Respiratory_system_labelled.JPG


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http://wikieducator.org/File:Respiratory_system_labelled.JPGhttp://wikieducator.org/File:Respiratory_system_labelled.JPG


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Examiners Tip

To remember the sequence of structures

through which air passes when you breathe in

imagine an apple tree:

Trunk Trachea

Bough Bronchus

Branch BronchioleApples Alveoli


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Diffusion

Small invertebrates, such as earthworms, takein oxygen over their skin surface

They need to have a large surface area to

obtain sufficient oxygen, and their skin is thinand moist

Examples of gaseous exchange surfaces are the

alveoli in the lungs of mammals and gills of fish see over page for the structure of thealveolus


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Inspired Air

%

Expired Air

%

Explanation

en 79 79 Not used or produced by body

processes

n 21 16 Used up in the process of

respiration

n Dioxide 0.04 4 Produced in the process of

respiration

Vapour Variable Saturated Produced in the process ofrespiration, moisture evaporate

from the surface of the alveoli


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Testing for Carbon Dioxide

Two chemical reagents can used to test for carbondioxide - they change colour when the gas isbubbled through.

You only need to remember one

1. Limewater changes from colourless to milky

2.Hydrogencarbonate changes from red to yellow

Expired air makes these reagents change colourmore quickly than inspired air because there ismore carbon dioxide present in expired air


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Effects of Physical Activity on

Breathing The volume of air breathed in and out during normal, relaxed

breathing is about 0.5litres

This is the tidal volume

The breathing rate is about 12 breaths per minute

During exercise, the volume inhaled (depth) increases to about 5litres (depending on the age, sex, size and fitness of the person)

The maximum amount of air breathed in or out in one breath is thevital capacity

The breathing rate can increase to over 20 breaths per minute

The total lung volume is greater than the vital capacity becausesome air always remains in the lungs (otherwise the lungs wouldcollapse and the alveoli walls would stick together)


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Answers

1a) (i) Inspired air contains more oxygen, less carbondioxide and less water vapour than expired air

(ii) Three features: 1. the wall of the alveolus is one

cell thick (or very thin) 2. there is a moist surface tothe alveoli 3. there are large numbers of alveoli 4.the air in the alveoli is constantly being replaced

b) (i)The release of energy by cells without the use ofoxygen

(ii) In muscle cells