Upper Respiratory System

• Nose - Functions

  provides an airway for respiration

  moistens + warms entering air

  filters + cleans inspired air

  serves as a resonating chamber for speech

  houses the olfactory receptors
• Surface Features of External Nose

  inc the root (area between eyebrows), bridge + dorsum nasi (anterior margin), terminating in the apex (tip of the nose)
• External Openings of the Nose

  the nostrils or nares r bounded laterally by the flare alae
• Skeletal Framework of the External Nose


  skeletal framework of the external nose is fashioned by the nasal + frontal bones superiorly (forming the bridge + root, respectively), the maxillary bones laterally + flexible plates of hyaline cartilage (the alar + septal cartilages + the lateral processes of the spetal cartilage) inferiorly
• Nasal Cavity

  the internal nasal cavity lies in + posterior to the external nose

  during breathing, air enters the cavity by passing thru the nares

  the nasal cavity is divided by the midline nasal septum

  the nasal cavity is continous posteriorly w the nasal portion of the pharynx thru the posterior nasal apertures (chonae)
• Roof of Nasal Cavity

  the roof of the nasal cavity is formed by the ethmoid + sphenoid bones of the skull
• Floor of the Nasal Cavity

  the floor is formed by the palate, which separates the nasal cavity from the oral cavity below
• Hard Palate vs Soft Palate

  anteriorly, where the palate is supported by the palatine bones + processes of the maxillary bones = hard palate

  the unsupported posterior portion = muscular soft palate
• Nasal Vestibule

  the part of the nasal cavity just superior to each nostril = nasal vestibule

  = lined w skin containing sebaceous (glands that produce sebum - oily substance that protects the skin) + sweat glands + numerous hair follicles
• Vibrissae

  the hair folicles of the nasal vestibule = vibrissae

  = filter coarse particles from inspired air
• Two Types of Mucous Membrane

  olfactory mucosa

  respiratory mucosa
• Olfactory Mucosa

  the small patch of olfactory mucosa lines the slitlike superior region of the nasal cavity + contains smell receptors in its olfactory epithelium
• Respiratory Mucosa

  the respiratory mucosa lines most of the nasal cavity

  = a ciliated columnar epithelium, containing scattered goblet cells, which r richlysupplied w seromucous nasal glands
• Seromucous Nasal Glands - Lysozymes

  seromucous nasa glands secrete mucus containing lysoszymes - antibacterial enzymes

  the sticky mucus traps inspired dust, bacteria + other debris, while the lysozymes attack + chemically destroys bacteria
• Seromucous Nasal Glands - Defensins & Humidity

  the epithelial cells of the respiratory mucosa also secrete defensins, natural antibiotics that help kill invading microbes

  the high water content of the mucus film humidifies incoming air
• Nasal Conchae

  protruding medially from each lateral wall of the nasal cavity r 3 scroll-like mucosa-covered projections - the superior, medial + inferior nasal conchae

  the curved conchae greatly increase the mucosal surface are exposed to air + enhance air turbulence in the cavity

  the gases in inhaled air swirl the twists + turns, deflecting heavier, nongaseous particles onto the mucus-coated surfaces, where they become trapped
• Conchae & Nasal Mucosa - Heating & Cooling

  the conchae + nasal mucosa not only function during inspiration to filter, heat + moisten the air but also act during exhalation to reclaim this heat + moisture

  inspired aire cools the conchae, then during exhalation these cooled conchae precipitate moisture + extract heat from the humid air flowing over them

  this reclamation process minimises the amoun of moisture + heat lost from the body thru breathing
• Paranasal Sinuses

  the nasal cavity is surrounded by a ring of paranasal sinsuses

  they r located in the frontal, sphenoid, ethmoid + maxillary bones

  the sinuses lighten the skull + help warm + moisten the air

  the mucus they produce ultimately flows into the nasal cavity + the suctioning effect created by nose blowing helps drain the sinuses
• Nasal Cavity Anatomy

  nasal cavity

  
• Pharynx

  the funnel-shaped pharynx connects the nasal cavity + mouth superiorly to the laryns + oesophagus inferiorly

  from superior to inferior, the pharynx is divided into 3 regions - nasopharynx, oropharynx + laryngopharynx

  the muscular pharynx wall is composed of skeletal muscle thru out its length

  however the cellular composition of its mucosa varies from 1 pharyngeal region to another
• Nasopharynx

  nasopharynx = posterior to the nasal cavity, inferior to the sphenoid bone + superior to the level of the soft palate

  cos it lies above the point where food enters the body, it serves only as an air passageway

  during swallowing, the soft palate + its pendulous uvula move superiorly, an action that closes off the nasopharynx + prevents food from entering the nasal cavity

  
• Oropharynx

  the oropharynx lies posterior to the oral cavity + is continous w it thru an archway = isthmus of the fauces

  cos the oropharynx extends inferiorly from the level of the soft palate to the epiglottis, both swallowed food + inhaled air pass thru it
• Strucutre of the Oropharynx

  as the nasopharynx blends into the orpharynx, the epithelium changes from pseudostratified columnar to a more protective stratified squamous epithelium

  =accomodates the increased friction + chemical trauma (hot +spicy foods) accompanying food passage

  
• Laryngopharynx

  like the oropharynx above it, the laryngopharynx serves as a passageway for food + air + is lined w a stratified squamous epithelium

  it lies directly posterior to the larynx, where the respiratory + digestive pathways diverge + extends to the inferior edge of the cricoid cartilage

  is also continous w the oesophagus posteriorly