Nasal Cavity and Paranasal sinuses Flashcards
Components of the nose (nasus)
- External nose (hardly recognizable in domestic animals; will merge with the muzzle)
- Paired nasal cavities
- Paranasal sinuses
Functions of nose
- Olfaction
- Warming
- Humidifying and cleaning of air that is breathed in
Different types of nose/nostrils
- Nostrils
- Nasal plate
- Nasolabial plate
- Rostral plate
Nostrils
- Shape is supported by cartilage
- Usually within specialized skin (except horses)
Horse nostrils
- Within non-modified skin in horses
- Horses are obligate nose breathers so their nostrils can open very wide
Nasal plate
- Dog, sheep, goat
- Modified naked skin with a philtrum
- Moist in dogs. Dry in sheep and goats
Wet nasal plate of dogs
- Moist but no underlying glands
- They are wet due to the overflow of nasal mucous glands, lateral nasal gland, and licking
Nasolabial plate
- Ox
- Extensive modified naked skin
- No philtrum
- Continues with dorsal lip
- Usually moist due to underlying sweat glands
- Pattern of grooves unique to each individual
Rostral plate
- Pig
- Modified naked skin has underlying sweat glands
- Round nostril within a movable strong plate
- Supported by rostral bones (which are attached by some cartilage)
- Good for truffle hunting
Nasal cartilages
- Nasal septum- separates left and right nasal cavity/vestibules
- Free edge of nasal septum attached to cartilages that support margins of the nostrils (dorsolateral and lateral cartilages)
- Shape of cartilages determines the shape of nostril and its opening in different species/individuals
Nasal cartilages in horse
- Alar cartilage- comma shaped (“wing”= ala)
- When raised, nostrils open up
- Determines the shape/size of nostrils
True vs. false nostril (Horse)
Horse nostril is divided into two parts:
- True part= ventral- leads to nasal cavity (brings air)
- False part= dorsal- leads to blind-ended sac called nasal diverticulum. Occupies the nasoincisive notch and when nostrils are fully open during exercise, the nasal diverticulum is minimal or gone
Nasal diverticulum
A skin-lined, blind-ended sac
Nasal conchae
Paired nasal cavities/vestibules are less roomy inside than it appears from outside because the space is partly filled by delicate mucosa-covered, fragile laminate-turbinate bones called the conchae (means “shell”)
Different concha
- Dorsal concha- attached to the nasal bone (project in from dorsal)
- Ventral concha- attached to maxillary bones
- Ethmoidal conchae or Ethmoturbinates- attached to ethmoid bone (can also be called middle concha)
Ethmoturbinates in dog
- Conchae are more extensive and branched in carnivores
- Olfactory mucosa is extensive in this region
Ectoturbinates
When ethmoturbinates grow into the sinuses
Endoturbinate
When ethmoturbinates remain in the nasal cavity
Yellowish colour/regions in dog mouth
Olfactory receptors- modified neurons with dendrites
Nasal meatuses
- Meatuses= cleft
- Small potential spaces between conchae and surrounding structures
Different meatuses
- Dorsal meatus
- Ventral meatus
- Middle meatus
- Common meatus
Dorsal meatus
- Between dorsal concha and ceiling
- Leads to the fundus of nasal cavity and brings air in contact with olfactory mucosa
Ventral meatus
- Between ventral concha and floor of nasal cavity
- Ventral and common meatuses provide the main airway for breathing air
Middle meatus
- Between dorsal and ventral conchae
- Usually give access to the sinuses
Common meatus
- Between nasal septum and other conchae
- Ventral and common meatuses provide the main airway for breathing air
Nasal mucosa
- Thickened by vascular plexuses forming cavernous tissue
- Extended by folds of the conchae (what causes irritation when sick and inflamed)
- Epithelium has cilia to help move mucus toward pharynx for swallowing
Function of nasal mucosa
- Effective olfaction
- Warming
- Humidifying and cleaning air
Intubation
- Need to be careful not to damage mucosa with nasal tubes
- Need to guide instruments down the junction of ventral and common meatuses
Vomeronasal
- Present in all domestic animals
- Arises from the incisive duct and runs caudally
- Involved in the detection of pheromones and results in flehmen reaction
Vomeronasal differences in horse
Incisive ducts do not enter mouth so vomeronasal only communicates with nasal cavity
Paranasal sinuses
- Sinuses are diverticula of nasal cavity that excavate skull bones, largely after birth
- They take their names from bones invaded, especially those invaded first
- Retain a narrow (direct or indirect) connection with nasal cavity BUT they do not communicate with contralateral counterpart
Possible functions of the paranasal sinuses
- Thermal and mechanical protection of skull
- Increase skull size for muscular attachment without increasing its weight
- Resonance of voice
- Other functions
Sinuses in dog
- Limited in dog
- Frontal sinus can have 3 parts
- No true maxillary sinus, instead have an ill-defined recess in maxilla that freely communicates with nasal cavity called a maxillary recess
Lateral nasal gland in dog
- A large gland that lies in lateral nasal wall, close to entrance of maxillary recess
- Has serous secretion that is drained at rostral end of dorsal conchae
Lateral nasal gland secretion
- Serous
- May have a social significance in nose-to-nose sniffing when dogs meet
Lateral nasal gland in cats
- Gland and duct are not visible macroscopically
- Secretion is mucous instead of serous
Sinuses in ox
Frontal sinuses
- Dorsal conchal sinus
Maxillary sinuses
Sphenoid sinuses
Frontal sinuses of ox
- In mature ox
- Can extend caudally as far as occipital, temporal, and more
- Can also extend into cornual process and caudal part of dorsal concha called dorsal conchal sinus
Maxillary sinuses of ox
Involves maxilla first then may extend into palatine, lacrimal, and sphenoids, and ventral concha
Sphenoid sinuses of ox
Often well developed and may be extensions of maxillary sinus or arise independently
Sinuses in pig
Very extensive sinuses
- Especially in mature boars
- Makes it hard to euthanise them
- Frontal sinuses and dorsal conchal sinus
- Maxillary sinuses
- Sphenopalatine sinuses
Sinuses in horse
- Frontal sinus
- Maxillary sinuses
- Sphenopalatine sinuses
Frontal sinus of horse
- Wide extension to dorsal conchal= called conchofrontal sinus
- No direct opening to nasal cavity
- Communicates via maxillary sinus
Maxillary sinuses of horse
- Rostal and caudal maxillary
- Extends to caudal part of ventral conchal sinus
- Nasomaxillary aperture communicates with nasal cavity
- Safe trephination (drilling into bone) can give access to sinuses and tooth roots
Trephination
- Drilling into bone
- Can give access to sinuses and tooth roots
Air flow direction in horse sinuses
Drainage issues because the hole is actually situated up higher so a build up can occur
Developmental and breed differences in sinuses
- The extent of drainage/sinuses differs between species and age
Ex. brachycephalic, mesaticephalic, dolichocephalic
Livestock euthanasia
- Not between the eyes
- Need to be medial and above eyes, more in between ears
