Respiratory system

1.4 Higher-level organisation

2.2 Respiration

Respiratory system

  1. Structure

    1. The lungs are in the upper part of the body, known as the thorax, protected by the ribcage and separated from the lower part of the body, known as the abdomen, by the diaphragm
    2. Air enters through the mouth and into the trachea, which splits into two bronchi, one for each lung, which in turn split into several bronchioles and terminating in alveoli
    3. The intercostal muscles are several muscles between the ribs that aid in breathing

  2. Process

    1. The respiratory system continuously takes air into & out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air

    2. Inhalation

      1. The intercostal muscles contract, pulling the rib cage down
      2. At the same time, the diaphragm muscles contract, causing the diaphragm to flatten
      3. These two movements cause an increase in volume of the thorax
      4. The consequent decrease in pressure to below that of the surrounding air causing air to enter the lungs

    3. Exhalation

      1. The intercostal muscles relax, allowing the rib cage to move up
      2. At the same time, the diaphragm muscles relax, allowing the diaphragm to resume its domed shape
      3. These two movements cause a decrease in volume of the thorax
      4. The consequent increase in pressure to above that of the surrounding air causes air to leave the lungs

  3. Breathing problems

    1. Causes

      1. Spontaneous breathing may stop due to disease or injury
      2. The alveoli may be damaged, decreasing the surface area for gas exchange
      3. The respiratory tract may be narrowed, allowing decreasing the amount of air being exchanged
      4. The person may be paralysed, so their muscles cannot move the ribcage

    2. Ventilators

      1. A negative pressure ventilator causes air to be drawn into the lungs by encasing the patient’s chest in a chamber that periodically changes the pressure to mimic the natural act of breathing: it decreases so that the lungs expand causing air to flow into it, and it increases so that the lungs contract causing air to flow out of it
      2. A positive pressure ventilator forces air into the lungs from a container that can contain between 21 to 100% oxygen, increasing the pressure until released and the patient exhales naturally due to the lungs’ elasticity
      3. Positive pressure ventilators are smaller, easier to manage in the home and can be linked to computer for fine control, but often requires someone to be present to monitor it