Anatomy of Nose, Nasal Cavity and Paranasal Sinuses - Fill in the Blank Flashcards

External Nose

• The nose comprises external nose (bones and cartilages) and the nasal cavity; septum divides into right and left halves.

• Functions: olfaction, respiration, beautification (appearance).

• External Nose: Morphology

  • Pyramidal in shape; projects from the face.
  • Root directed upwards (continuous with forehead); apex points downwards; dorsum is the part between root and apex.

• External Nose: Features

  • Two elliptical orifices (naris) separated by the nasal septum.
  • Ala nasi (lateral margin) is rounded and mobile.
  • Skin over cartilages is thicker and contains many sebaceous glands.
  • Skin extends into the vestibule with vibrissae (stiff hairs).

• Skeletal framework

  • Above: nasal bones, frontal processes of the maxillae, and nasal part of the frontal bone.
  • Below: hyaline cartilage (two lateral cartilages, two alar cartilages, one septal cartilage).

• Muscular attachments

  • Major alar cartilage; minor alar cartilages;
  • Septal cartilage; Nasalis muscle; Levator labii superioris alaeque nasi; Depressor septi nasi.

• Blood supply (external nose)

  • Skin supplied by branches of ophthalmic and maxillary arteries.
  • Ala and lower part of the septum supplied by the facial artery.

• Nerve supply (external nose)

  • Infratrochlear and external nasal branches of CN V1; infraorbital branch of CN V2.

Nasal Cavity

• Extends from the anterior nares to the posterior nares (choana).

• Mucosa lines most of the cavity; nasal vestibule is lined by skin.

• Regions: Vestibule; Olfactory region (superior \frac{1}{3}); Respiratory region (inferior \frac{2}{3}).

• Boundaries: floor, roof, lateral wall, medial wall (septum).

• Roof of nasal cavity

  • Formed anteriorly by nasal and frontal bones; middle by cribriform plate of ethmoid; posteriorly by downward-sloping body of sphenoid.
  • Located beneath the anterior cranial fossa.

• Floor of nasal cavity

  • Formed by palatine process of maxilla and horizontal plate of palatine bone.

• Medial wall of nasal cavity

  • Nasal septum: perpendicular plate of ethmoid (superior), vomer (inferior), septal cartilage (anterior).
  • Kiesselbach area (anterior part of septum) – common site of epistaxis.

• Lateral walls and conchae

  • Three conchae: superior, middle, inferior.
  • The space below each concha is a meatus (superior, middle, inferior).

• Lateral wall details

  • Inferior meatus: nasolacrimal duct.
  • Middle meatus: drainage from maxillary, frontal, anterior & middle ethmoid sinuses.
  • Superior meatus: drainage from posterior ethmoid sinuses.
  • Sphenoethmoidal recess: sphenoid sinus.

• Openings into the nasal cavity

  • Nasolacrimal canal drains into the inferior meatus.
  • Sphenoid sinus opens into the sphenoethmoidal recess.
  • Posterior ethmoidal air cells open into the superior meatus.
  • Anterior & middle ethmoid air cells, maxillary and frontal sinuses open into the middle meatus.

• Blood supply of the nasal cavity

  • Branches from maxillary artery, facial artery, and ophthalmic arteries.
  • Key arteries: sphenopalatine artery and anterior ethmoidal artery.
  • Kiesselbach (anteroinferior septum) has anastomosis of anterior & posterior ethmoidal, sphenopalatine, greater palatine, and septal branch of superior labial arteries; common site of epistaxis.
  • Venous drainage via a rich submucosal plexus to sphenopalatine, facial, and ophthalmic veins; thermoregulation.

• Nerve supply of the nasal cavity

  • Olfactory nerves (CN I) from olfactory mucosa ascend through the cribriform plate to olfactory bulbs (SVA).
  • General sensation via branches of V1 (ophthalmic) and V2 (maxillary).

• Lymph drainage

  • Vestibule: submandibular nodes.
  • Remainder of nasal cavity: upper deep cervical nodes.

Paranasal Sinuses

• Paranasal sinuses: Frontal, Ethmoidal, Sphenoidal, and Maxillary.

• Characteristics: absent at birth; variable size and often asymmetrical; air-filled; lined with mucoperiosteum; communicate with nasal cavity via small openings.

• Functions and drainage

  • Mucus moved by ciliary action; siphon effect during nose blowing.
  • Functions: voice resonance; reduce skull weight; warm and moisten inhaled air; shock absorption.

• Maxillary sinus

  • Location: within body of maxilla, behind cheek.
  • Roof: orbital floor; floor near roots of the second premolars and first molar; apex near zygomatic process.
  • Opens into the middle meatus.
  • Blood supply: facial, supraorbital, greater palatine.
  • Nerve supply: infraorbital, anterior, middle & posterior superior alveolar.

• Frontal sinuses

  • Within frontal bone; rarely symmetric; separated by a bony septum.
  • Each sinus roughly triangular; extends upward above medial eyebrow and into the orbit roof.
  • Opens into the middle meatus.
  • Blood supply: supraorbital and anterior ethmoidal arteries; nerve supply: supraorbital nerve.

• Sphenoidal sinuses

  • Located within sphenoid bone; near optic chiasm and pituitary.
  • Opens into the sphenoethmoidal recess (above the superior concha).
  • Blood supply and innervation: posterior ethmoidal artery and nerve.

• Ethmoid sinuses

  • Anterior, middle, and posterior cells.
  • Located within ethmoid bone, between nose and orbit.
  • Drainage: anterior & middle cells into middle meatus; posterior cells into superior meatus.
  • Thin bony separation from orbit; infection can spread less readily.
  • Blood supply: sphenopalatine, and anterior & posterior ethmoidal arteries.
  • Nerve supply: anterior & posterior ethmoidal orbital branches of the pterygopalatine ganglion.

• Sinus Drainage Schema (summary)

  • Frontal and anterior ethmoid and maxillary sinuses drain to the middle meatus.
  • Posterior ethmoid drains to the superior meatus.
  • Sphenoid sinus drains to the sphenoethmoidal recess.

Applied Anatomy

• Clinical relevance:
  • Examination of the paranasal sinuses.
  • Sinusitis.
  • Basal skull fracture.

Note: All key structures and relationships are summarized for quick recall and last-minute review.