The Lungs

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  • The Lungs
    • Organ of Exchange
      • Air passes into the lungs through thenose and along the trachea, bronchi and bronchioles, and finally to the alveoli
    • Inspiration
      • diaphragm contracts - flatter, pushing digestive organs down
        • External Intercostal muscles contract to raise ribs
          • Volume of chest cavity increases
            • Pressure decreases to below atmospheric pressure
              • Air moves into the lungs, from high to low pressure
    • Expiration
      • Diaphragm relaxes, pushed up by displaced organs underneath
        • External intercostal muscles relax and ribs fall
          • volume ofchest cavity decreases
            • pressure rises above atmospheric pressure
              • Air moves out of lungs
    • Gas Exchange
      • the movement of gases by diffusion between an organism and its environment across a barrier
      • through the walls of the alveoli and capillaries
      • Adaptations
        • Permeable barrier of plasma membranes to O2 and CO2
        • Thin Barrier - reduce diffusion distance: alveoli and capillary wall 1 sqaumous cell thick, narrow capillaries only allow 1 red blood cell through at once, total barrier less then 1micrometre
        • Moisture lines alveoli - evaporates as we breathe out. Lungs must produce surfactant to reduce the cohesive forces between the water molecules and stop the alveolus collapsing
        • alveoli lined with capillaries to decrease diffusion distance
        • Large surface area - so many alveoli(100-300µm) that they combine to make approx. 70m²
    • Concentration Gradient
      • needs to be maintained for quick diffusion - lots of molcules on one side and few on the other
        • so there needs to be a removal system and a fresh supply
      • achieved by the blood bringing CO2 from the tissues to the lungs and carrying O2 away from the lungs
      • the breathing movements of the lungs ventilate the lungs - replacing used air with fresh, oxygen filled air - and removing CO2
    • Roles of Tissue
      • Elastic Fibres
        • smooth muscle cannot reverse the narrowing effect. When it constricts it deforms the elastic fibres
        • as the muscle relaxes, the elastic fibres recoil to their original size and shape - helping to dilate the airway
      • Smooth Muscle
        • can be important if there are harmful substances in the air - involuntary reaction
        • can contract, constricting the airway (narrower lumen) - restricting the air flow
      • Goblet Cells/Glandular tissue
        • under the epithelium the tissue can secrete mucus to trap tiny particles from the air
        • removal can reduce the risk of infection
      • Cartilage
        • structural - holds the trachea and bronchi open, preventing collapse when pressure is low in inhilation
        • C shaped to allow some flexability - movementof neck and expansion of oesophagus
      • Ciliated Epithelium
        • ciliated cells have tiny hair like extensions - cilia - that move in a synchronised pattern
        • waft mucus up airway to back of throat to be swallowed for stomasch acid to destroy bacteria
    • Where are the tissues
      • Bronchioles - much narrower than bronchi, some may have cartilage but many have none. Wall mostly smooth muscle and elastic fibres. Smallest bronchioles have clusters of alveoli at their ends
      • Trachea and Bronchi- lots of cartilage, inside surface of cartilage contains elastic fibres, smooth muscle and blood vessels. Inner lining is epithelium layer containing cilia and goblet cells
        • Bronchi are smaller than Trachea
      • Alveoli - elastic fibres for stretch and recoil function

Comments

sophie

Thank you for this resource it will help me immensely in my revision

Swallowtail

This is a Mind map that contains useful little flow diagrams to help you learn stages of the processes of breathing in and out as well as adaptations of the lungs and lung tissues. This would be helpful to any student studying lung function. Research shows that adding images to Mind Maps aid memory so this would be a useful exercise after download.

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