Respiratory System Part 1

• Respiratory system


  Divided into two main components: upper respiratory system and lower respiratory system
• Upper respiratory system


  • Nose
  • Nasal cavity
  • Nasopharynx
  • Larynx
  • Trachea

  
• Lower respiratory system


  • Bronchus
  • Bronchioles
  • Lungs
• Nose


  • Rostral to the eyes and dorsal to the oral regions
  • External nares (nostrils) - external openings of the respiratory tube and they lead to nasal passages
  • Muzzles (snout) - skin around the nares with hairs, and non-haired area (planum nasale, planum rostrale, planum nasolabiale) with numerous eccrine sweat glands

  
• Bony nasal aperture


  • Largest opening into the skull
  • Bounded rostrally by the nasal cartilages
  • Movable portion of the nose ends in a truncated apex

  
• Cartilages of the nose

  • Unpaired cartilaginous septum
  • Paired dorsal lateral nasal cartilage
  • Paired ventral lateral nasal cartilage
  • Paired accessory cartilages

  
• Nasal cavity


  • Located between the nostrils and the choana
  • Choana located at the caudal end of the hard palate mark the boundary between nasal cavity and nasopharynx
  • Separated from the oral cavity by the hard and soft palates

  
• Median nasal septum


  • Separates the nasal cavity into left and right cavities
  • Rostral part is cartilaginous, caudal part is osseous

  
• Nasal conchae


  • Dorsal
  • Ventral
  • Middle
  • Ethmoidal

  
• Nasal conchae


  • Cartilaginous or ossified scrolls covered with nasal mucosa that occupy most of the nasal cavity
  • Help to warm and humidify inspired air
  • Olfactory epithelium covering the ethmoidal conchae contains the sensory endings of the olfactory nerve

  
• Nasal meatuses


  • Dorsal nasal meatus
  • Middle nasal meatus
  • Ventral nasal meatus
  • Common nasal meatus
• Paranasal sinuses


  • Air-filled spaces lined with mucosa that communicate with the nasal cavity
  • Functions include resonating (voice), insulation and cooling of the brain and light weight skull construction
• Paranasal sinuses present


  • Maxillary sinus (or maxillary recess)
  • Frontal sinus
  • Palatine sinus (absent in carnivores and pig)
  • Sphenoid sinus (absent in dog and small ruminant)
  • Lacrimal sinus (present in pig & ruminant)
  • Dorsal conchal sinus (present in pig & ruminant)
• Pharynx


  • Connects the oral cavity to the trachea and esophagus
  • Functions as a passageway for air and food
  • Divided into three regions: nasopharynx, oropharynx and laryngopharynx
• Nasopharynx


  • Part of the respiratory channel
  • Lies dorsal to the soft palate and extends from the choana to the intrapharyngeal opening
  • Roof is concave
• Laryngopharynx


  • Common to the respiratory and the digestive channels
  • Caudal continuation of the oropharynx and extends from the base of the epiglottis to about the level of the cricoid cartilage of the larynx
• Larynx


  • Short cartilaginous tube that connects the pharynx with the trachea
  • Consists of several cartilages lined on the inside with mucous membrane
• Laryngeal cartilages


  • Epiglottic cartilage
  • Thyroid cartilage
  • Cricoid cartilage
  • Arytenoid cartilage (paired)
• Position of the larynx during breathing

  • Normal breathing: larynx forms a direct continuation of the nasopharynx
  • Nasal breathing: nasopharynx is dilated, soft palate lies against the root of the tongue and closes the oropharynx, epiglottis projects through the intrapharyngeal ostium into the nasopharynx
• Hyoid apparatus


  • Holds the larynx in place and supports the pharynx and tongue from the skull
  • Made up of 5 different bones: tympanohyoid cartilage, stylohyoid, epihyoid, ceratohyoid, basihyoid and thyrohyoid