RS - Vertebrate Adaptations

• Structure of the human respiratory system

  • Nasal cavity
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Lungs
  • Alveoli
• Function of the human respiratory system


  • Inhalation and exhalation
  • Exchange of gases between lungs and bloodstream
  • Exchange of gases between bloodstream and body tissues
  • Vibration of the vocal cords
  • Olfaction or smelling
• Fish respiratory system

  • Aquatic respiration
  • Includes mouth, buccal cavity, pharynx, internal gill slits, gill pouches and external gill slits
  • No internal nares, glottis and laryngotracheal chambers
  • Water enters through mouth and leaves through external gill slits
  • Only gills present for aquatic respiration
  • Lungs absent altogether
  • No buccopharyngeal respiration
  • No cutaneous respiration
  • Highly vascularized gills serve as efficient organs for gaseous exchange in water
• How fish respire

  1. Fish opens mouth, water runs over gills

  2. Blood in capillaries picks up oxygen dissolved in water

  3. Blood moves through fish body to deliver oxygen
• Amphibian respiratory system

  • Aquatic and aerial respiration
  • Includes external nares, nasal chambers, internal nares, buccopharyngeal cavity, glottis and laryngotracheal chamber
  • Gill slits and gill pouches absent
  • Air enters through external nares and leaves also through them
  • Mouth not used for entry of air
  • No epiglottis
  • 3 respiratory surfaces: skin, lungs, lining of mouth
  • Respiration through skin when submerged
  • Gills present in tadpole larva, lungs in adult
  • 2 lungs, ovoid, thin-walled, elastic hollow sacs
  • Lungs have no lobes, completely enclosed by peritoneum
  • Air sacs absent
  • Moist and richly vascular skin facilitates cutaneous respiration
  • Skin must stay wet for oxygen absorption
• How amphibians respire

  1. Buccal pumping powers breathing, promotes air movement into lungs

  2. Air from lungs channeled to air sac which resonates to make sound louder

  3. Larynx more developed in males
• Reptile respiratory system

  • Generally aerial respiration
  • Includes external nares, nasal sacs, internal nares, buccal cavity, pharynx, glottis, trachea and bronchi
  • No gill slits and gill pouches
  • Air enters and leaves through external nares
  • Scales prevent oxygen absorption through skin, so only lung respiration
  • Mouth not used for respiration
  • No epiglottis
  • Larynx and trachea separate, no vocal cords or thyroid cartilage
  • No gills, only lungs in adult
  • Embryo develops temporary pharyngeal gill pouches and gill slits
  • Snakes have 1 functional lung, boas and pythons have 2
  • Air sacs absent, no cutaneous respiration
  • Inspiration and expiration by ribs and intercostal muscles
  • Crocodiles have dorsobronchi that branch near lungs, parabronchi deliver oxygen
• Lizard respiratory system

  • No diaphragm, use chest muscles to inflate and deflate lungs
  • Some use throat muscles for buccal pumping
• Bird respiratory system


  • Aerial or pulmonary respiration
  • Includes external nares, nine air sacs, buccal cavity, pharynx, glottis, trachea, bronchi, syrinx
  • No gill slits and gill pouches
  • Air enters and leaves through external nares
  • Mouth not used for respiration
  • External nares dorsal at base of upper beak
  • No epiglottis
  • Larynx and trachea separate, no vocal cords or thyroid cartilage
  • No gills, only lungs in adult
  • Embryo develops temporary pharyngeal gill pouches and gill slits
  • 2 small, ovoid, compact, inelastic lungs without lobes
  • Birds inhale and exhale twice per respiration, mammals once
  • Lungs have looped airways instead of alveoli
  • System of large, thin-walled, elastic, nonvascular air sacs around and connected to lungs
  • No cutaneous respiration
  • Inspiration and expiration by sternum, intercostal, abdominal muscles
  • Unidirectional airflow requires two full respiratory cycles
  • No diaphragm, air sacs increase respiratory efficiency
• Mammalian respiratory system


  • Generally aerial or pulmonary respiration
  • Includes external nares, nasal sacs, internal nares, buccal cavity, pharynx, glottis, trachea and bronchi
  • Air enters and leaves through external nares, for olfaction and respiration
  • Epiglottis present
  • Larynx and trachea separate, vocal cords and thyroid cartilage in larynx
  • Only lungs present in adult, no gills
  • 2 large, soft, elastic, spongy lungs with lobes, enclosed in pleural cavities
  • Terminal bronchioles and alveoli present, highly vascular
  • Air sacs absent
  • Inspiration and expiration by diaphragm and intercostal muscles
  • Presence of blind alveoli and pores to equalize air pressure