Human Breathing System

Human Breathing System

1. Nose: we breathe in through the nose because it cleans, moistens and warms the air. Air that is warm and moist can diffuse more asily from the lungs into the bloodstream

2. Pharynx: the epiglottis is located in the pharynx at the top of the trachea. The epiglottis closes over the trachea when we swallow to prevent food and drink from passing into the lungs

3. Trachea: along with its subdivisions; bronchi and upper bronchioles are made of muscle, elastic fibres and sections of inflexible cartilage

   • The lower bronchioles don't have cartilage. This allows them to contract and narrow, leading to astma
   • All these tubes are lined with mucus and cilia. Disease-causing organisms stick to the mucus. The cilia beat to create a current that pushes mucus up the epiglottis. Mucus then passes down to stomach

4. Lungs: function is gas exchange. Lungs are enclosed by two pleural membranes

5. Alveolus (plural: alveoli): are tiny sacs that are the site of gas exchange

   • Adaptions
     • Very Numerous
     • Large Surface Area
     • Moist surfaces to increase diffusion
     • Thin walls, allowing diffusion more quickly
   • Gas Exchange
     • Oxygen passes from alveolus into blood cells
       • Carbon dioxide passes from plasma into alveolus
         • Water vapour passes from plasma into alveolus

6. Mechanism of Breathing

   • Inhalation
     • 1: Respiration produces waste gas carbon dioxide. This is slightly acidic
       • 2: Respiratory centres in the medulla oblongata in the brain monitor the acidity of blood. When acidity is too high, electrical impulses are sent from medulla to diaphragm & intercostal muscles
         • 3: Diaphragm & intercostal muscles cotract
           • 4: Ribs move up and out, the diaphragm moves down. Volume of chest increases
             • 5: Pressure in chest falls. The external air pressure is now greater than the air pressure in the chest
               • 6: Air is forced into the lungs, causing them to inflate
     • Active process
     • Exhalation is opposite events to inhalation

7. Asthma

   • Symptoms: noisy, wheezy breathing and feeling of lack of breath
   • Cause is unknown. Can be triggered by inhaling allergens such as pollen
     • Bronchioles narrow and their linings become inflamed. This reduces amount of air that can pass in and out of lungs
   • Treatment: take drugs (bronchodilators in inhalers), that widen the bronchioles & reduce inflammation.

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