Nasal cavity, paranasal sinuses and horns

What are the names of the turbinates?

dorsal turbinate

ventral turbinate

ethmoturbinate (most caudal)

what are the spaces between the turbinates called?

Meatus

What does the cribiform plate connect and what goes through it?

Brain and nasal cavity

olfactory nerves

State the main paranasal sinuses (hint: there are 2) What are the functions of paranasal sinuses?

Frontal sinus & Maxillary sinus

They enlarge the skull without adding weight to allow for larger SA for muscle attachment

Allow for larger oral cavity to accommodate large teeth

Where does the frontal sinus lie?

Within frontal bone

Where does the frontal sinus connect with in all domestic species? what species is the exception?

The frontal sinus communicates directly with the Nasal cavity.

Horse

what is the difference btw normal dog and brachycephalic dogs in terms of frontal sinus?

Brachycephalic dogs have reduced/absent frontal sinus.

Where do horns arise from?

Cornual process of frontal bone

Biggest nerve in horn? what cranial nerve is it from? Where is this nerve located?

Cornual nerve of zygomaticotemporal nerve of the opthalmic division of trigeminal nerve

Located under temporal line

State the nerves that innervate the horn

Cornual N.

Cornual branch of infratrochlear N.

Frontal N.

In horse, where does the frontal sinus drain?

into maxillary sinus

What is the difference between maxillary sinus in horse vs dog and cat?

Horse:

• small communication with nasal cavity,

• Maxillary sinus separated ventrally by bony septum into rostral maxillary sinus and caudal maxillary sinus

Dog and cat: wide communication w/ nasal cavity

What is the function of nasal cavity? How are they achieved?

Warm and humidify air going to lungs

• air brought into contact with large SA for water and heat exchange

Filter air going to lungs

• contact surface covered in mucus → trap small particles

• Hairs at entrance trap large particles

Detect odor molecules in air

• Many sensory receptor cells to detect odor molecules

Nasal cavity is divided into 2 fossae by?

Nasal septum (made up of ethmoid bone caudally and cartilagenous sheet)

What is the purpose of turbinate bones? where do they originate from?

increase SA of nasal cavity.

Originate from nasal and maxillary wall

Identify the numbered structures

1. cribiform plate

2. ethmoturbinate

3. Dorsal turbinate

4. Ventral turbinate

In dogs, why are there alot of leaflets arising for ventral trubinate?

Dogs sniff alot, thus lots of air enter the nose.

• air needs to filter out particulate matter and pick up scent

What is special about a horse’s turbinates? What is its clinical significance?

Ventral turbinate bottom scroll lost = large ventral meatus

Tubes can be put up their nose on a regular basis

• endoscopy

• to enter central pouch

Why are paranasal sinuses prone to infection?

they are connected to nasal cavity via narrow opening → blockage by inflammation/congestion

When euthanising by shooting, what do you aim for? Why?

Where would you shoot a horse/ox/sheep?

Aim for medulla obolgata as it is the respiratory and CV centre of brain

Avoid midline on species with strong bony midline septum.

• Ox: Just beside midline

• Sheep/goat: Behind horn if horned / at area where horn is meant to be in unhorned

• Horse: Midline, It has thinner, more fragile midline

How are pigs euthanised? why?

Stun/electrocute/ put them in gas

Cant shoot - Head is big, brain buried deep inside

How can you tell that the horse is young?

Frontal sinus separated from turbinate, boundry removed when horse matures

Maxillary sinus musch smaller due to unerupted cheek teeth occupying maxillary space

Infraorbital canal sits directly on top on teeth (only separated by thin bony plate

Why is the maxillary sinus prone to infection in horse?

Maxillary sinus is separated from teeth by a thin bony plate

• teeth infection can eat away at bony plate and infect maxillary sinus

Sinus also lies ventral to small slit-like communication to nasal cavity → difficult to drain

What are palpable landmarks in horse?

Infraorbital foramen

Nasoincisive notch

In case of infection, sinuses can be opened via trephine points. What are the trephine points?