Respiratory System

• Respiratory system


  Organs include the nose, pharynx, larynx, trachea, bronchi and their smaller branches, and the lungs, which contain alveoli, or terminal air sacs
• Respiratory system structures


  • Gas exchange with the blood happens only in the alveoli
  • Other structures are just conducting passageways that carry air through the lungs
• Respiratory tract divisions


  • Upper respiratory tract (nose to larynx)
  • Lower respiratory tract (trachea to alveoli)
• Upper respiratory tract


  • Purifies, humidifies, and warms incoming air
• Nose


  • The only external visible part of the respiratory system
  • Air enters through the nostrils
• Nasal cavity


  • Divided by a midline nasal septum
  • Olfactory receptors for smell in superior part
  • Respiratory mucosa lines the rest, with a rich network of veins that warm the air
• Nasal conchae


  • Mucosa-covered projections that greatly increase the surface area of the mucosa exposed to air
• Palate


  • Partition separating the nasal and oral cavities
  • Hard palate (anterior, bone-supported)
  • Soft palate (posterior, unsupported)
• Paranasal sinuses


  • Located in the frontal, sphenoid, ethmoid, and maxillary bones
  • Lighten the skull and act as resonance chambers for speech
  • Produce mucus that drains into the nasal cavities
• Cleft palate


  Causes breathing difficulty and problems with oral cavity functions
• Rhinitis (nasal inflammation)


  Causes nasal congestion and postnasal drip
• Sinusitis (sinus inflammation)


  Difficult to treat and can cause marked changes in voice quality
• Pharynx


  Muscular passageway that serves as a common passageway for food and air
• Pharynx regions


  • Nasopharynx (superior, air enters from nasal cavity)
  • Oropharynx (middle, food and air)
  • Laryngopharynx (inferior, air enters larynx, food enters esophagus)
• Tonsils


  • Lymphatic tissue found in the pharynx
  • Pharyngeal tonsil (adenoid) in nasopharynx
  • Palatine tonsils in oropharynx
  • Lingual tonsils at base of tongue
• Larynx


  Routes air and food into proper channels, plays role in speech
• Larynx structure


  • Formed by 8 rigid hyaline cartilages and epiglottis
  • Thyroid cartilage is largest, forms Adam's apple
  • Epiglottis tips to route food into esophagus during swallowing
• Vocal folds/cords


  • Part of larynx mucous membrane, vibrate with expelled air to allow speech
• Trachea


  • Fairly rigid due to C-shaped rings of hyaline cartilage
  • Lined with ciliated mucosa that propels debris upwards
• Tracheal obstruction


  Life-threatening, can cause suffocation
• Bronchi


  Right and left main bronchi formed by division of trachea, plunge into lungs
• Lungs


  • Occupy thoracic cavity except central area with heart, blood vessels, etc.
  • Covered in visceral pleura, walls of thorax lined with parietal pleura
  • Pleural fluid allows easy gliding during breathing
• Airflow through lungs


  1. Main bronchi subdivide into smaller bronchi and bronchioles

  2. Terminal bronchioles lead to respiratory zone (respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli)
• Lung tissues


  • Mainly elastic connective tissue (stroma) that allows stretching and recoil
• Alveoli


  • Walls composed of thin squamous epithelial cells
  • Alveolar pores connect neighboring air sacs
  • Alveolar macrophages ("dust cells") provide defense
  • Surfactant-secreting cells coat alveolar surfaces
• Respiration


  Four distinct events: pulmonary ventilation, external respiration, respiratory gas transport, internal respiration
• Pulmonary ventilation


  Air movement into and out of the lungs, commonly called breathing
• External respiration


  Gas exchange between pulmonary blood and alveoli
• Respiratory gas transport


  Oxygen and carbon dioxide transported to/from lungs and body tissues via bloodstream
• Internal respiration


  Gas exchange between blood and body cells
• Cellular respiration, the use of oxygen to produce ATP and carbon dioxide, occurs in all cells
• Mechanics of breathing


  Volume changes lead to pressure changes, which lead to air flow to equalize pressure
• Tidal volume (TV)


  Normal quiet breathing volume, around 500ml
• Inspiratory reserve volume (IRV)


  Additional air that can be forcibly inhaled above tidal volume, around 3,100ml
• Expiratory reserve volume (ERV)


  Additional air that can be forcibly exhaled beyond tidal expiration, around 1,200ml
• Residual volume


  Air that remains in the lungs after maximum expiration, around 1,200ml
• Vital capacity


  Total amount of exchangeable air, sum of TV, IRV, and ERV
• Tidal volume (TV)


  Normal quiet breathing moves approximately 50ml of air into and out of the lungs with each breath
• Inspiratory reserve volume (IRV)

  The amount of air that can be taken in forcibly above the tidal volume, around 3,100ml
• Expiratory reserve volume (ERV)

  The amount of air that can be forcibly exhaled beyond tidal expiration, approximately 1,200ml