Introduction to Respiratory system

• Respiratory system


  One of the two systems that work together to ensure a continuous supply of oxygen to all cells of the body and a continual removal of carbon dioxide
• Cardiovascular system


  One of the two systems that work together to ensure a continuous supply of oxygen to all cells of the body and a continual removal of carbon dioxide
• Primary function of the respiratory system

  • Intake of oxygen and elimination of carbon dioxide
• Other functions of the respiratory structures

  • Olfaction
  • Sound production
• Upper respiratory tract


  Includes the nose and pharynx
• Lower respiratory tract


  Includes the larynx, trachea (windpipe), bronchi and bronchioles (air passages), and the lung
• Conducting portion


  All the structures inside and outside the lungs that conduct air to the tissues which take part in gaseous exchange, from the nose to terminal bronchioles
• Respiratory portion


  All the tissues in the lungs that take part in gaseous exchange, from respiratory bronchioles to alveoli
• The nose


  • The external portion is made of cartilage and skin and is lined with mucous
  • The external nares are divided by a cartilaginous septum
  • The front part has coarse hairs which filter out large dust particles
• Functions of the nose

  • Inhaling air
  • Filtering, warming and moistening the air
  • Receiving olfactory stimuli
  • Acting as a resonating chamber for sound
  • Acting as a reservoir for nitrogen
• Nasopharynx


  One of the three regions the pharynx is divided into
• Oropharynx


  One of the three regions the pharynx is divided into
• Laryngopharynx


  One of the three regions the pharynx is divided into
• Tonsils and adenoids


  • Tissues which guard against infection
  • The epiglottis guards against aspiration
• Functions of the pharynx

  • Acting as a passageway for air, food and drink
  • Acting as a resonating chamber for sound
  • Housing the tonsils - function of immunity
• Glottis


  The space between the vocal chords
• Muscles of the pharynx and larynx are responsible for speech and swallowing
• Abnormalities in the muscles of the pharynx and larynx may result in speech deficit, difficulty swallowing and impaired response to stimulation of the roof of the mouth
• Functions of the larynx

  • Routing air and food to the correct channels
  • Producing sound
• Trachea


  • 11 cm long
  • Extends from the larynx to the carina where it divides into the right and left main bronchi
  • Contains cough receptors
  • C shaped
• Functions of the trachea

  • Airflow
  • Mucociliary clearance
• Right primary bronchus


  • Wider and straighter than the left
  • Objects are more easily inhaled
• Primary bronchi


  • Branch to form the secondary bronchi, one to each lobe of the lung
  • Have thick plates of cartilage to prevent them from collapsing
• Secondary bronchi


  • Branch to form the tertiary bronchi (segmental bronchi)
• Bronchioles


  • The segmental bronchi branches into multiple bronchioles
  • Bronchioles then branch into terminal bronchioles and then into respiratory bronchioles
• Bronchial structure


  • The walls of primary, secondary and tertiary bronchi contain progressively less cartilage and more smooth muscle
  • The bronchioles have no cartilage so there is no restriction on the airways
• Alveoli


  • Air-filled pockets within the lungs where gas exchange takes place
  • Each alveolus is surrounded by blood vessels, ready to collect oxygen and give up carbon dioxide
• Alveolar cells


  • Type 1 cells are more numerous and are the main site of gas exchange
  • Type 2 cells are fewer and secrete alveolar fluid which includes a surfactant
• Surfactant


  Lowers the surface tension of alveolar fluid which reduces their tendency to collapse
• Conducting zone


  The function of the conducting portion of the respiratory tract is to transport air to the respiratory bronchioles and lung tissue where gaseous exchange takes place
• Mucociliary escalator


  The cilia beat in a coordinated fashion to help trap and get rid of foreign particles
• Bones of the thorax

  • Sternum
  • 12 pairs of ribs
  • 12 thoracic vertebrae
  • Clavicles and the scapulae form the shoulder girdle
• Parietal pleura


  • Outer layer that lines the chest wall and superior surface of the diaphragm
  • Thicker, more fibrous
  • Innervated by the phrenic and intercostal nerves - sensitive to pain
• Visceral pleura


  • Inner layer that covers the lung and lines the fissures
  • Innervated by the autonomic nervous system - not sensitive to pain
• Pleural cavity

  A potential space containing pleural fluid that allows the two pleural layers to glide over one another and creates a surface tension which keeps the pleurae together
• Muscles of respiration


  • Diaphragm
  • Intercostal muscles
  • Scalenes
  • Sternocleidomastoid