CGIER

• Aerobic respiration


  Highly effective in producing ATP from glucose with a steady supply of oxygen
• The three distinct stages of respiration are: external respiration, gas transport and internal respiration
• External respiration transfers oxygen into the blood from the atmosphere

  Gas transport is the transport of oxygen and carbon dioxide in the blood

  Internal respiration is the cellular respiration where there is an oxygen uptake and a carbon dioxide production within the cell
• The two main functions of respiratory system is to supply the body with oxygen and to remove carbon dioxide from the body

  Level of respiration = oxygen requirement = index of metabolic activity

  Warm blooded animals, homeotherms have a high oxygen requirement
• The upper respiratory tract consists of the pharynx and larynx and epiglottis
• The pharynx consists of nasopharynx, oropharynx and laryngopharynx

  An opening in the floor of the pharynx leads to the larynx.
• Larynx


  Contains vocal chords and cannot collapse due to the presence of cartilage in its walls
• Epiglottis


  A cartilaginous flap that automatically covers the larynx to prevent the entry of food and liquid into the trachea/windpipe to the lower respiratory tract
• The most common form of infection in the world is related to upper respiratory tracts. It can be sometimes viral or bacterial
• Infections in the upper respiratory tract can cause severe complications in young children, elderly people, and immunosuppressant patients
• Examples of upper respiratory tract infections

  • Nasal congestion
  • Blocked sinuses
  • Sore throat
  • Earache
  • Common cold
• Components of the lower respiratory tract

  • Trachea
  • Bronchus (bronchi and bronchioles)
  • Lungs
• Trachea


  A single tube that branches into the right and left bronchus (one in each lung) which consists of mucous-secreting goblet cells and rings of hyaline cartilage that reinforce the tube walls
• In the trachea, bronchi, and bronchioles

  Ciliated epithelium consists of cilia that push upwards the mucous secreted by the goblet cells, supported by the cough reflex
• Bronchioles lead to alveolar ducts


  At the end of the alveolar ducts, it contains alveoli that is the site of oxygen and carbon dioxide exchange with the blood
• Alveoli


  Surrounded by two thin layered epithelial cells - the epithelium and endothelium of the capillary walls, facilitating gas exchange with the blood
• Type I and Type II pneumocytes

  Type I pneumocytes are extremely thin for gas exchange, while Type II pneumocytes secrete surfactant to reduce surface tension
• In premature babies, respiratory distress syndrome occurs due to inadequate surfactant secretion by immature Type II pneumocytes, leading to atelectasis (alveolar collapse)
• Treatment for respiratory distress syndrome


  Involves mechanical ventilation, oxygen therapy, and use of synthetic/natural surfactants
• Respiratory distress syndrome usually manifests immediately after birth or within a few hours, improving with good patient care after 3 - 7 days
• Lung characteristics


  • Situated in the thoracic cavity
  • Consists of 5 lobes
  • Right lung has three lobes (upper, middle, lower) and is bigger than the left lung
  • Left lung has 2 lobes (upper, lower) and is smaller to accommodate the heart
• The process of gas exchange involves oxygen being exchanged from the alveolus into the RBC and carbon dioxide being exchanged from the RBC to the alveolus
• Components of the thoracic cavity

  • Thoracic cage
  • Anterior sternum
  • Posterior spinal column
  • Rib cage
  • Diaphragm
• Lungs


  Covered by visceral pleura, inner thorax wall covered by parietal pleura, pleural cavities in between
• Fluid in pleural cavity


  Provides lubrication between chest wall and lungs
• Pleural walls can secrete mucus and when infected can cause pleurisy
• Interpleural space

  Has a negative pressure of -4mmHg acting as a suction to keep the lungs inflated
• Pressure always varies due to breathing between visceral and parietal pleura


  Ex = -2mmHg, In = -6mmHg
• Intrapleural pressure

  Always negative to prevent pneumothorax (lung collapse) due to surface tension of alveolar fluids and elastic fibers
• Mechanism of ventilation

  Inspiration and expiration
• Breathing

  Increase and decrease of thorax volume by means of respiratory muscles, intercostal and diaphragm
• Inspiration

  Active process controlled by the brain, involves diaphragm contraction, rib cage movement, and air flow into the lungs
• Expiration

  Passive process, involves relaxation of muscles, air forced out of the lungs
• Expiration can be made active by contraction of abdominal wall muscles
• Intrapleural pressure


  Becomes more negative as chest wall expands during inspiration
• Volume of breath during each breath is 0.5L of air pushed into and out of the lungs due to pressure gradients
• Respiratory centre in the brain stem controls breathing
• Medulla contains dorsal and ventral respiratory groups, Pons contains pontine respiratory group with Pneumotaxic and Apneustic centers
• Chemical regulation of respiration is done through chemosensitive area near the medulla sensitive to CO2 and H+ concentration in the blood
• Carotid and Aortic bodies contain chemoreceptors sensitive to PO2 concentration