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NMSK (Lectures) > Nasal Cavities > Flashcards

Nasal Cavities Flashcards

1
Q

Identify the features of the external nares of different species and explain their role in airway resistance

A
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2
Q

Identify the main features of the external nares

A

Nostrils
Nasal Vestibule

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3
Q

What are nostrils?

A

They are the actual meatus surrounded by hairless skin. This skin can be highly modified depending on species
The meatus/nostrils are surrounded by nasal cartilage dorsally and ventrally

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4
Q

What are the nasal vestibule?

A

The opening of the nasal cavity, and contains the opening of the nasolacrimal duct which is visible just inside of the ventral surface

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5
Q

Outline the species differences of the external nares with regards to cattle

A

Nostrils surrounded by smooth hairless nasolabial plate:
Stratified cornified epithelium
Serous glands create moisture
Nasolabial glands

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6
Q

Outline the species differences of the external nares with regards to Equidae

A

No ventral nasal cartilage

Incomplete cartilaginous ring:
Distensible nostrils

Alar cartilages (plate and horn):
Form comma shaped nostrils.

Ventral ‘true’ nostril

Dorsal ‘false’ nostril

Skin lined diverticulum
Within nasoincisive notch

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7
Q

Outline the species differences of the external nares with regards to Carnivordae

A

Nasal plate:
Divided by median groove (philtrum)

Secretions from lateral nasal gland

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8
Q

Outline the species differences of the external nares with regards to Suidae

A

Small nostrils on snout

Highly sensitive

Contains the os rostrale

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9
Q

Outline the species differences of the external nares with regards to Aves

A

Slit like openings.
Not diving birds eg gannet

Operculum:
Overhanging bony flap

Wide communication between nasal cavity and pharynx:
Choana

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10
Q

Provide an overview of nasal cavity function

A

Conduction and preparation inspired of air:
Moisten air
Warm air
Filters particles
Mucus traps particles -> swallowed

Air flow resistance

Heat exchangers for cooling the brain:
Cooled venous blood passes via the rete mirabalis and cools the arterial blood going to the brain

Olfaction:
Caudal regions of the turbinates covered by olfactory epithelium

Defense mechanisms

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11
Q

Provide an overview of nasal cavity structure

A

Extends from nostrils to cribriform plate of ethmoid bone:

Divided by nasal septum

Further divided into nasal meatuses by nasal conchae:
	Which further increase nasal surface area
	
     Highly vascular structure
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12
Q

List the key landmarks bordering the nasal cavity

A

Dorsally and laterally:
facial bones.

Ventrally:
hard palate.

Rostrally:
nostrils (external nares).

Caudally:
pharynx / ethmoid bone.

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13
Q

Define the term conchae

A

Turbinate bones which project into the nasal cavity and form scrolls and are covered by nasal mucus. They are coiled to increase SA. 3 divisions:

Dorsal
Including the alar fold (small cartilaginous structure at the rostral end of the nasal cavity)
Ventral
Only turbinate which leads to the pharynx
Ethmoidal
Attached to the ethmoidal plate
Rich in sensory nerve endings as it is responsible for sense of smell

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14
Q

Define the term turbinates

A

Delicate Scrolls which can be split into three groups:
Ectoturibinates
In frontal sinus
6 in dogs; 20-30 in horses

Endotubinates
	In nasal cavity
	5-6
	#1 & #2 form dorsa; and middle conchae
	Attach to cribriform plate caudally

Maxilloturbinates  
	In nasal cavity
	Paired
	Attached to medial wall of maxilla
	Forms the ventral concha

Ethmoturbinates in collective term for ecto- and endoturbinates

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15
Q

Define the term meatus

A

Dorsal nasal meatus
The passage between the roof of the nasal cavity and the dorsal nasal concha.

Middle nasal meatus
Between the dorsal and ventral conchae, it communicates with the paranasal sinuses.

Ventral nasal meatus
Main pathway for airflow leading to the pharynx, positioned between ventral nasal concha and
floor of the nasal cavity.
Runs into common

Common nasal meatus

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16
Q

What is the cribriform plate?

A

A part of the ethmoid bone

17
Q

Outline the species differences of the nasal cavity with regards to Equidae

A

Endoturbinates: part of ethmoidal bone which provides support for dorsal (1st endoturbinate) and middle (2nd endoturbinates) conchae

Simple Structure
	4 nasal meatus
		
		Dorsal meatus
			to olfactory mucosa
		
		Middle meatus
			to paranasal sinuses
		
		Ventral meatus
			to the pharynx
		
		Common meatus
                            to the pharynx
18
Q

Outline the species differences of the nasal cavity with regards to Bovidae

A

Very small middle meatus

19
Q

Outline the histology of nasal mucosa

A

Nasal cavity can be split into three separate regions;

Vestibular

Respiritory

Olfactory

20
Q

Describe the histology of the vestibular region of the nasal mucosa

A

Lined by subcutaneous mucus which is composed of stratified squamous epithelium

21
Q

Describe the histology of the respiratory region of the nasal mucosa

A

Lined by respiritory mucus which is composed of epithelium and lamina propria.

The epithelium consists of pseudostratified ciliated columnar cells, with goblet cells embedded.

The laminar propria contains many blood vessels and seromucous glands

22
Q

Outline the functions of the respiratory epithelium

A
  1. Regulation of air flow by erectile tissue
  2. Cleaning (cilia)
  3. Humidification (evaporator)
  4. Warming (variable blood perfusion)
  5. Protecting reflexes (sneeze reflex).

3) and 4) are important for cooling the brain and for saving water from expiratory air in some species e.g. Camels, kangaroos.

23
Q

Describe the overall structure of the olfactory region of the nasal mucosa

A

Lined by olfactory mucosa composed of olfactory epithelium

Overall structure:

The ethmoturbinates extend rostrally from the ethmoid bone

Covered with respiratory epithelium

Also contains olfactory sensory neurones

Sniffing alters the normal airflow to bring the air into contact with the ethmoturbinates

24
Q

Describe the microstructure (histology) of the olfactory region of the nasal mucosa

A

Tall pseudostratified ciliated columnar appearance of olfactory epithelium

Composed of:

Olfactory receptor cells
	    Olfactory cells are bipolar neurones
	    Cell body embedded within the middle of the stratum
		
	      Apical portion extends as thin dendritic processes, which terminated as a swelling known 
                  as the olfactory bulb. This bulb gives rise to non-motile cilia like structures which detects 
                  chemicals
		
		Basal portion is where a single non myelinated axon penetrates the basement membrane 
                    and joins with other axons forming bundles in the lamina propria
	
	
		The axons group into bundles which penetrate the cribriform plate and enter the 
                    olfactory lobe of the brain through the Olfactory N (CN I)
	
	Olfactory neurones continuously renewed due to the presence of neural stem cells in the 
            basal layer

Supporting cells

Basal cells
25
Q

What is the vomeronasal organ

A

Vomeronasal Organ
Accessory olfactory sense organ. Can be known as the Jacobson’s Organ

Contained within hard palate:
-paired, blind ending ducts originating from the incisive ducts, which connect nasal and oral
cavities
-Unique chemoreceptors distinct from other olfactory organs:
-May play a role in pheromone detection
-Lip curling (Flehmen)

26
Q

Outline the transitions of the nasal mucous membranes

A

Vestibule:
Transition from integument (Skin) to mucous membrane

b: Nasal cavity:
respiratory epithelium

c: caudodorsal part of the ethmoidal conchae:
olfactory epithelium

27
Q

Explain the path of airflow along the nasal chambers

A

Inhaled air is warmed and humidified by the rostral portions of the nasal mucosa, and the mucosa itself is cooled by this interaction. At exercise or with high ambient temperature, dilatation of blood vessels that comprise the rich vascular supply to the nasal mucosa enhances heat and moisture exchange

28
Q

Explain how the nasal chamber provide resistance to airflow

A

Resistance = length / radius^4
Resistance to flow also affected by changes in direction

Horses are obligate nasal breathers:

Very hard for them to mouth-breathe

Flow aided by:
Ram air into nostrils

Straighter head-neck-thorax alignment

Compromise flow v air preparation:

Turbinates necessary hindrance

Horses have less complex turbinates to reduce resistance

NMSK (Lectures) (63 decks)

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