External Nose:

External / anterior nasal openings = Nares
Dorsum of the nose = where the two lateral aspects of the nose meet
Root of the nose = the part of the nose that is continuous with the forehead.
Tip of the nose = apex
The Ala = the flared lateral portions
Bony parts: make up the bridge
- A process from frontal bone = the nasal portion of the frontal bone
- Inferior, find maxilla bone
- Nasal bones meet in midline
Cartilage: 5 paired cartilages
Most lateral aspect of nose has no cartilage, it is fibrofatty tissue.
Shape / size of nose is determined by shape / size of bony / cartilaginous parts.

Innervation to skin of nose:

Nasal cavity:

Is divided into two portions by the nasal septum
Nares are anterior air aperture, choanae are posterior air aperture
Vestibule: the entry way into the nasal cavity
- Is area of transition between skin of face and mucous membrane lining nasal cavity
- Has hair due to skin that has wrapped around into vestibule
- Innervated by V2
Mucous membrane lining the nasal cavity is also mucoperiosteum
- If fuses with the periosteum of the bones in the nasal cavity
- The bones of the nasal cavity are very frail, may break if try to remove membrane.
- Respiratory mucous membrane has:
Mucous glands: humidify the air- use parasympathetics
A dense vascular network: warm the air- use sympathetics

Nasal septum:

Made up of bony components
- Perpendicular plate of the Ethmoid bone (has distinct midline presence in nasal cavity)
- Vomer: Triangular bone only found in nasal cavity, inferior to perpendicular plate
- Nasal Crests of Palatine bone and of maxilla which contribute to most inferior aspect of septum
- Septal cartilage: the anterior portion of the septum. Aka Nasal septal cartilage.
Innervation to Mucous membrane of septum
- Part of the mucous membrane is olfactory
Upper third of nasal cavity in crescent shape
Innervated by CN I (Olfactory)
Neurosensory cells have specialized receptors (chemoreceptors) embedded in the mucous membrane.
- Are bipolar cells
- Sends information back toward somaà sends central process up through cribiform plate→to the olfactory bulb sitting on superior aspect of cribiform plate.

V1 branch (internal nasal) innervates sensation for anterior aspect
V2 (Nasopalatine nerve) innervates sensation for posterior aspect
- Nasopalatine nerve then goes through incisive foramen
- Goes on to supply part of palate
Blood supply to Mucous membrane of septum
- Continuation of anterior ethmoidal artery supplies same region as V1
- Posterior ethmoidal artery supplies same region as CN I
- Sphenopalatine artery supplies same region as V2
- Ethmoidal branches are from ophthalmic artery, sphenopalatine artery is termination of the maxillary artery.

Lateral Nasal wall:

In this passage way, have openings of several structures:
Inferior nasal meatus: Opening of nasolactimal duct- the passageway for tears

Middle nasal meatus:
- Ethmoidal Bulla: a bulge that is protruding into the middle nasal meatus. Creates a groove = hiatus semilunaris.
  - The hiatus leaves superiorly and expands into a funnel shaped structure called the infundibulum.
  - The infundibulum receives the frontonasal duct (receives fluid from frontal sinus). Frontal sinus uses the frontonasal duct to empty mucus into the middle meatus.
  - Bulla also has openings of Middle ethmoid air cells
- Openings to anterior ethmoid air cells – anterior to Bulla
  - Opening of Maxillary sinus
  - Sometimes in the hiatus
  - Maxillary sinus is the largest sinus
- Superior nasal meatus
  - Openings to posterior ethmoid air cells
  - Superiorly, find opening of sphenoid sinus
Innervation to lateral nasal wall
- Cranial Nerve I: for the olfactory mucosa on the lateral nasal wall (upper third, crescent shape)
- Anterior ethmoidal (from nasociliary) of V1 to anterior aspect
- Multiple nasal branches of V2 to posterior aspect
Blood supply is similar
- Anterior / posterior ethmoidal branchs from ophthalmic artery to anterior / posterior-superior aspects.
- Nasal branches of maxillary artery for posterior aspect

Paranasal sinuses:

Develop as diverticula of the nasal cavity (outgrowths)
Have mucous membrane lining that is continuous with that of the nasal cavity
These continue to develop throughout entire life and enlarge.
- Maxillary sinus comes into contact with molars after time
- May have confounding pain in maxillary premolars / molarsà is coming from maxillary sinus and not teeth.
- May have abscesses of teeth that go right into maxillary sinus.
Are organized into 4 collections:
- Frontal Sinuses
Sometimes fused into one
In the frontal bone

Local inflammatory response causes engorgement of vasculature as well as increased mucous secretion
- May lead to chronic sinusitis
- When in a “face – down” position, sinuses have a better drainage pattern- seems to be more appropriate for grazing animals
- Medicines: made to stop local mucous secretions. Also causes vasoconstriction to vascular bed.
Innervation to sinuses: All by branches of either V1 or V2 of CN V
Purpose of sinuses:
- To lighten the skull
- Change voice resonance (changes with congestion)