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  • 1.  
  • 2. Gaseous Exchange
  • 3. Lungs & Thoracic Cavity – Structure
    • Take a copy of a GCSE Lung structure diagram – can your students label it correctly?
    • OR
    • Using the white board get the students to add diagrams and labels to make up the complete Human Thorax – what detail is missing?
    • OR
    • Give your students an A level copy (click the web-link below) of the Human Thorax – can they identify the labels and structures not expressed at GCSE level?
    • For a detailed structure and how to make models of the lungs visit www.smm.org/heart/lessons/lesson7.htm
  • 4. Lungs & Thoracic Cavity – Structure
    • TASKS:
    • Create a Pathway for Air travel from the mouth to the Alveoli naming all the anatomical areas you pass.
    • AND
    • Why is the Double Pleural Membrane and the Pleural fluid so important to Lung Function?
  • 5. Lungs & Thoracic Cavity – Structure
    • To create a larger surface area for DIFFUSION to take place, the lungs contain many small air sacs called ALVEOLI. These air sacs have a thin wall to allow for the diffusion of Respiratory gases (0 2 & CO 2 ) to take place. CAPPILATIES cover these thin walls to allow for efficient DIFFUSION to occur.
    Capillary (less than 1 RBC wide so to distort cell as it travels through to increase its surface area aiding diffusion) Alveolus (thin moist cell wall to assist with diffusion)
  • 6. Diffusion
    • DIFFUSION is the movement of gases from one place to another. Within the Gaseous exchange system this takes place in 2 areas;
    • 1. The ALVEOLI (the lungs)
    • 2. The WORKING MUSCLE
    • In both the above RESPIRATORY GASES are transported into the blood within the capillaries.
  • 7. Diffusion
    • DIFFUSION OCCURS WHEN THERE IS A DIFFERENCE IN CONCENTRATION (the amount) OF A GAS BETWEEN ONE PLACE AND ANOTHER. This is called a DIFFUSION GRADIENT.
    • GASES ALWAYS TRAVEL FROM
    • HIGH CONCENTRATION LOW CONCENTRACTION
    • IMAGINE IF THE GAS WAS REPRESNTED BY FOOTBALLS PLACED HIGH AT THE TOP OF A HILL, THEY WOULD ALWAYS WANT TO GO TO THE LOWEST POINT BY TRAVELLING DOWN.
  • 8. Gases and the Atmosphere
    • AIR – made up of many components
    • Nitrogen (N 2 )
    • Oxygen (O 2 )
    • other gases (e.g. CO 2 )
    • Water (H 2 O)
  • 9. Gases and the Atmosphere
    • Due to atmospheric pressure AIR is thinner at altitude compared to at sea level.
    • This is because as you travel further away from the earth the area that the Air components has to fill is larger thus spreading out the molecules.
    Place a bag of M & M’s in a small plastic box and see how many collisions they have with each other as you move the box. Now transfer the same M & M’s into a larger plastic box – notice that they have more space to move and have less collisions.
  • 10. Gases and the Atmosphere
  • 11. Measurement & Accuracy
    • AIR – as it is made up of many components it is easier and more accurate to compare the amount of each gas if we compare it to the other gases in terms of “pressure” rather than its %. How much pressure (the number of collisions each particle has with others) is called “partial pressure” (pp).
    • Measured in Pascals (Pa), or mm of Mercury (Mg)
  • 12. Measurement & Accuracy
    • To find the pp of a gas we can use a simple equation.
    • pp of a gas = Barometric pressure X Fractional
    • of a gas Concentration
    • pp O2 = 760 X 21 (dry atmospheric Air at sea level) 100
    • = 159.6mmHg ≈ 21 Kpa
    • Now find out the actual barometric pressure today by looking at the Met office website www.metoffice.gov.uk/weather/uk/uk_forecast_pressure.html
    • and work out the pp of O2 and CO2
  • 13. Breathing In - INSPIRATION
    • External Intercostals contract
    • Rib cage lifts up and out
    • Diaphragm contracts and flattens
    • Thoracic Cavity increases Volume
    • Pressure lower inside than out
    • Air rushes in
  • 14. Breathing In – Expiration (at rest)
    • External Intercostals relax
    • Rib cage drops down and in
    • Diaphragm relaxes and domes up
    • Thoracic Cavity decreases Volume
    • Pressure greater inside than out
    • Air pushes out
  • 15. Breathing In – Expiration (during exercise)
    • Often known as FORCED or ACTIVE Expiration
    • Internal Intercostals contract
    • Rib cage drops down and in
    • Diaphragm relaxes and domes up
    • Thoracic Cavity decreases Volume
    • Pressure greater inside than out
    • Air pushed out
  • 16. Breathing – Control of Movements
    • Happens by Nervous Control
    • – influenced by exercise
    • Breathing at rest – INVOLUNTARY, controlled by “Respiratory Control Centre” in Brain
    • DURING INSPIRATION DURING EXPIRATION
    • Inspiratory control centre Impulses stop and Muscles
    • Sends Motor Impulse to Relax.
    • external intercostals
    • & diaphragm.
  • 17. Breathing – Control of Movements
    • Happens by Nervous Control – influenced by exercise
    • Breathing During Exercise – INVOLUNTARY, controlled by “Respiratory Control Centre” in Brain
    • DURING INSPIRATION DURING EXPIRATION
    • Inspiratory control centre Expiratory control centre
    • Sends Motor Impulse to Sends motor impulses to
    • external intercostals internal intercostals
    • & diaphragm.
    • RIBS = UP & OUT RIBS = DOWN & IN
  • 18. Breathing – Control of Movements
    • DECREASES IN BLOOD pH = INCREASES IN VENTILATION
    • Caused by - in LACTIC ACID & CO2 PRODUCTION
    • Ventilation – caused by rate (how often) and depth (how much) of breathing.
    • Start of Exercise – Ventilation increased due to
    • increasing DEPTH
    • Heavier Exercise – Ventilation increased due to
    • increased RATE & Depth
  • 19. Breathing – Control of Movements During INSPIRATION
    • Detected by specialised SENSORSY receptors.
    • BARORECEPTORS – Detect changes in Blood Pressure
    • (Like a “Barometer “detects changes in air pressure)
    • CHEMORECEPTORS – Detect chemical changes in the
    • blood e.g. Increase in Acidity
    • (Like “Chemotherapy” uses chemicals to treat illness and disease)
    • MUSCLE RECEPTORS – Detect movement and therefore
    • exercise is taking place
  • 20. Breathing – Control of Movements During EXPIRATION
    • During FORCED or Active EXPIRATION specialised SENSORY receptors known as STRETCH receptors are stimulated. These are found around the THORAX
    • These STRETCH receptors are stimulated to prevent over-inflation of the lungs.
    • Nerve impulses are sent from the STRETCH receptors to the EXPIRIATORY CONTROL CENTRE which stimulates the contraction of the INTERNAL Intercostals.
    • This is known as the HERING BREUER REFLEX
  • 21. Respiratory System – Volumes and Measurement
    • Accurate measurement of lung volumes and capacities are measured by a SPIROMETER.
    • The volumes measured are;
    • TV = Tidal Volume (at rest)
    • ERV = Expiratory Reserve Volume
    • VC = Vital Capacity
    • IRV = Inspiratory Reserve Volume
    • RV = Residual Volume
    • Total Lung Capacity
  • 22. Respiratory System – Volumes and Measurement
    • SPIROMETER TRACE - AVERAGE VOLUMES
    • TV ≈ 0.5l ERV ≈ >1.0l VC ≈ >4.5l
    • IRV ≈ >3.0l RV ≈ >1.0l Total Lung Capacity ≈ 6l
    RESIDUAL VOLUME IRV ERV TV VC
  • 23. Respiratory System – Volumes and Measurement
    • VC TV IRV ERV
    • Total Lung Capacity VC RV
    • Minute Ventilation volume of air inspired or
    • expired in 1 min
    Commonly Used Equations
  • 24. Gaseous Exchange at the lungs
    • Respiratory gases move from the air in the ALVEOLI into the blood held in the CAPILLARIES and Visa Versa.
    • In the ALVEOLI: pp of O 2
    • pp of CO 2
    • In the CAPILLARY: pp of O 2
    • pp of CO 2
    (ATM AIR MIXED WITH ‘STALE’ AIR) Diffusion Gradient Exists – O 2 moves into the CAPILLARY and CO 2 moves into the ALVEOLI
  • 25. Gaseous Exchange at the Working Muscles
    • Respiratory gases move from the blood in the CAPILLARIES to the MYOGLOBIN in the MUSCLE CELLS and Visa Versa.
    • In the CAPILLARY: pp of O 2
    • pp of CO 2
    • In the MUSCLE: pp of O 2
    • pp of CO 2
    Diffusion Gradient Exists – O 2 moves into the MUSCLE and CO 2 moves into the CAPILLARY MYOBLOBIN IS THE MUSCLES EQUIVELANT OF HEAMOGLOBIN, AN OXYGEN CARRIER
  • 26. Oxygen Dissociation Curve
    • Oxygen is carried in the blood by the carrier HEAMOGLOBIN (Hb). It can be loaded with O2 depending on how much O2 is available;
    • (> ppO2 = > Hb Saturation)
    • Hb can be fully loaded (SATURATED) with O2 at relatively low pp of O2 (≈ 13kPa)
    • MYOGLOBIN IS THE MUSCLE CELLS EQUIVELENT TO Hb however it has a GREATER AFFININTY FOR O2
    • (in other words it attracts it more)
  • 27. Oxygen Dissociation Curve
    • Saturation of the HEAMOGLOBIN can be represented by an ‘S’ shaped curve on a graph.
    % Hb sat. with O 2 pp O 2 (mmHg) = O 2 Dissociation curve at rest = O 2 curve during exercise when temp & acidity increases making it harder for O 2 to attach to Hb. = Myoglobin Dissociation curve. Has greater affinity for O 2 so can saturate easier.