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• Aerobic respiration

  Highly effective in producing ATP from glucose with a steady supply of oxygen
• Stages of respiration

  1. External respiration

  2. Gas transport

  3. Internal respiration
• External respiration

  Transfers oxygen into the blood from the atmosphere
• Gas transport

  Transport of oxygen and carbon dioxide in the blood
• Internal respiration

  Cellular respiration where there is an oxygen uptake and a carbon dioxide production within the cell
• Functions of respiratory system

  • Supply the body with oxygen
  • Remove carbon dioxide from the body
• Level of respiration

  Oxygen requirement = Index of metabolic activity
• Warm blooded animals, homeotherms


  • Have a high oxygen requirement
• Upper respiratory tract

  • Pharynx
  • Larynx
  • Epiglottis
• Pharynx

  Consists of nasopharynx, oropharynx and laryngopharynx
• 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
• Upper respiratory tract infections can be viral or bacterial
• Upper respiratory tract infections are usually mild but can cause severe complications in young children, elderly people and immunosuppressant patients
• 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
• The trachea consists of rings of hyaline cartilage which reinforces the tube walls
• Bronchus extension

  Bronchus extends into bronchi which then further extends into small bronchioles
• Trachea, bronchi and bronchioles

  Have a ciliated epithelium which consists of cilia that pushes upwards the mucous that is secreted by the goblet cells which is supported by the cough reflex
• Bronchioles

  Lead to alveolar ducts
• 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, which helps the gases to diffuse easily from the alveolar walls to the capillaries
• Cell types in alveolar walls

  • Type I pneumocytes
  • Type II pneumocytes
• Type I pneumocytes

  Extremely thin to allow gas exchange, they are the pulmonary epithelium
• Type II pneumocytes

  Secrete surfactant that is a phospholipid that reduces the surface tension by acting as a detergent
• In premature babies there is a respiratory distress syndrome where the babies do not secrete adequate amounts of surfactant which is due to the lungs having immature type II pneumocytes
• Respiratory distress syndrome leads to the lungs not being able to properly expand which can lead to the alveoli to collapse (atelectasis)
• Treatment for respiratory distress syndrome

  1. Mechanical ventilation

  2. Oxygen therapy

  3. Use of synthetic/natural surfactants
• Respiratory distress syndrome usually manifests itself immediately after birth or within a few hours after birth, but with good patient care, this condition will improve after 3 - 7 days
• Lung lobes

  • Right lung: Upper, middle and lower lobe
  • Left lung: Upper and lower lobe
• The right lung is bigger than the left lung to accommodate the heart
• Lobes

  Further segmented and associated with specific segmental bronchi
• Gas exchange

  1. Oxygen is exchanged from the alveolus into the RBC

  2. Carbon dioxide is exchanged from the RBC to the alveolus
• Components of thoracic cavity

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


  Covered by visceral pleura and the inner thorax wall is covered by parietal pleura, with pleural cavities in between
• Pleural cavity

  Contains fluid that provides lubrication between the chest wall and lungs
• Pleural walls can secrete mucus and when infected can cause pleurisy
• Interpleural space

  Has a negative pressure -4mmHg that acts as a suction to keep the lungs inflated
• Intrapleural pressure always varies due to breathing between the visceral and parietal pleura, ranging from -2mmHg to -6mmHg