General Anatomy

• External nose

  Visible component of the face, projecting over and allowing entrance into the nasal cavity

  
• External nose


  • Has 2 elliptical apertures (openings) - Nostrils
  • Nasal septum
  • Ala nasi - Lateral margin, Round/mobile

  
• Skeletal structure of external nose

  • Bony component - Nasal bones, maxillae, frontal bone
  • Cartilaginous component - Lateral cartilages, major alar cartilages, minor alar cartilages, septal cartilage

  
• Internal nasal septum


  Formed by paired bones - Nasal, maxillary, palatine

  Unpaired bones - Ethmoid, vomer

  Septal and greater alar cartilages

  
• Nasal cavity


  • Divided into left and right nasal cavities by nasal septum
  • Seldom placed accurately in median plane, often deviates to one side
  • Covered with yellowish mucous membrane adhering to periosteum

  
• Muscles of external nose

  • Procerus
  • Transverse part of nasalis
  • Alar part of nasalis
  • Depressor septi nasi

  
• Procerus muscle


  Originates in fascia over nasal bone and lateral nasal cartilage, inserts into inferior forehead

  Contracts to depress medial eyebrows and wrinkle skin of superior dorsum
• Transverse part of nasalis

  Originates from maxilla, inserts into aponeurosis across dorsum of nose

  Action: Compresses nasal opening

  
• Alar part of nasalis


  Originates from maxilla over lateral incisor, inserts into alar cartilage

  Action: Widens nasal opening

  
• Depressor septi nasi


  Originates from maxilla above medial incisor, inserts into nasal septum

  Action: Pulls nasal septum inferiorly to widen nasal opening

  
• Blood supply to external nose

  • Skin - Branches of maxillary and ophthalmic arteries

  Septum and alar cartilages - Angular artery and lateral nasal artery (branches of facial artery)

  
• Venous drainage of external nose

  Facial vein, then internal jugular vein

  
• Lymphatic drainage of external nose

  Superficial lymphatic vessels accompanying facial vein, draining to deep cervical lymph nodes

  
• Innervation of external nose

  • Skin - External nasal nerve (branch of ophthalmic nerve, CN V1)

  Lateral aspects - Infraorbital nerve (branch of maxillary nerve, CN V2)

  Nasal muscles - Facial nerve (CN VII)

  
• Nasal cavity


  Extends from anterior nares to posterior nares (choanae)

  Functions: Warms and humidifies inspired air, removes pathogens/particulates, responsible for sense of smell, drains paranasal sinuses and lacrimal ducts

  
• Divisions of nasal cavity

  • Vestibule

  Respiratory region

  Olfactory region

  
• Nasal conchae


  • Inferior, middle, and superior conchae project into nasal cavity, creating meatuses for airflow

  Function: Increase surface area and disrupt airflow to humidify inspired air
• Openings into nasal cavity


  • Paranasal sinuses - Frontal, maxillary, anterior/middle/posterior ethmoidal, sphenoid

  Nasolacrimal duct

  Auditory (Eustachian) tube

  
• Cribriform plate


  Part of ethmoid bone forming roof of nasal cavity, contains perforations for olfactory nerve fibres

  
• Sphenopalatine foramen


  Allows communication between nasal cavity and pterygopalatine fossa, transmits sphenopalatine artery, nasopalatine and superior nasal nerves

  
• Incisive canal


  Pathway between nasal cavity and oral cavity, transmits nasopalatine nerve and greater palatine artery

  
• Arterial supply to nasal cavity

  • Internal carotid branches - Anterior ethmoidal, posterior ethmoidal

  External carotid branches - Sphenopalatine artery

  
• Cribriform plate


  It forms a portion of the roof of the nasal cavity and contains very small perforations, allowing fibres of the olfactory nerve to enter and exit

  
• Sphenopalatine foramen


  This hole allows communication between the nasal cavity and the pterygopalatine fossa

  
• Structures passing through the sphenopalatine foramen


  • Sphenopalatine artery
  • Nasopalatine nerve
  • Superior nasal nerves

  
• Incisive canal


  A pathway between the nasal cavity and the incisive fossa of the oral cavity, transmitting the nasopalatine nerve and greater palatine artery

  
• Arteries supplying the nose

  • Anterior ethmoidal artery (branch of ophthalmic artery)
  • Posterior ethmoidal artery (branch of ophthalmic artery)
  • Sphenopalatine artery (branch of external carotid)
  • Greater palatine artery (branch of external carotid)
  • Superior labial artery (branch of external carotid)
  • Lateral nasal arteries (branch of external carotid)

  
• Veins draining the nose

  • Pterygoid plexus
  • Facial vein
  • Cavernous sinus

  
• In some individuals, a few nasal veins join with the sagittal sinus, representing a potential pathway by which infection can spread from the nose into the cranial cavity

  
• Special sensory innervation of the nose

  Carried out by the olfactory nerves, which originate from the olfactory bulb on the superior surface of the cribriform plate

  
• General sensory innervation of the nose

  Delivered by the nasopalatine nerve (branch of maxillary nerve) and the nasociliary nerve (branch of ophthalmic nerve)

  
• Innervation of the external skin of the nose

  Supplied by the trigeminal nerve

  
• Paranasal sinuses


  Air-filled extensions of the nasal cavity, lined by ciliated pseudostratified epithelium with mucus-secreting goblet cells

  
• Functions of the paranasal sinuses

  • Lightening the weight of the head
  • Supporting immune defence of the nasal cavity
  • Humidifying inspired air
  • Increasing resonance of the voice
• Frontal sinuses


  Located within the frontal bone, triangular in shape, draining via the frontonasal duct into the middle meatus
• Innervation of the frontal sinuses


  Supplied by the supraorbital nerve (branch of ophthalmic nerve), arterial supply from the anterior ethmoidal artery

  
• Sphenoid sinuses


  Open into the nasal cavity in the spheno-ethmoidal recess, innervated by the posterior ethmoidal nerve (branch of ophthalmic nerve) and branches of the maxillary nerve, blood supply from pharyngeal branches of the maxillary arteries

  
• Ethmoidal sinuses


  • Anterior (opens onto the hiatus semilunaris)
  • Middle (opens onto the lateral wall of the middle meatus)
  • Posterior (opens onto the lateral wall of the superior meatus)

  
• Innervation and blood supply of the ethmoidal sinuses

  Innervated by the anterior and posterior ethmoidal branches of the nasociliary nerve and the maxillary nerve, blood supply from the anterior and posterior ethmoidal arteries

  
• Maxillary sinuses


  The largest of the paranasal sinuses, located laterally and slightly inferiorly to the nasal cavities, draining into the nasal cavity at the hiatus semilunaris