2.9 equine respiratory passageways

what does it mean that horses are obligate nasal breathers?
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what does it mean that horses are obligate nasal breathers?
they can't breath from their mouths

this is because their soft palate is elongated and forms a tight cuff around the laryngeal aditus. The aditus is therefore in direct communication with the nasopharynx during breathing
changes of equine air volume depend on?
dilation of nostrils
reduced blood flow
full abduction of the glottis
extension of head and neck
and action of the abdominal viscera against the diaphragm
nasal vestibule in equine
does not communicate directly with the nasal cavity
equine nasal diverticulum
blind ending cutaneous pouch formed by the alar fold
extends caudally to the nasoincisive notch

clinical relevance:
passing tubes
and
hairy skin lining prone to sebaceous cysts
A nasal vestibule
B ventral concha (scrolled)
C ventral meatus
D hard palate
E ethmoidal conchae
F frontal sinus
label
Image: A nasal vestibule B ventral concha (scrolled) C ventral meatus D hard palate E ethmoidal conchae F frontal sinus
clinical significance of paranasal sinus in equine
bacterial infection
nasal tumors
access to upper cheek teeth
complex and extensive
all paranasal sinuses in equine communicate with the nasal cavity through a single opening in the middle meatus called
the nasomaxillary opening
Image: all paranasal sinuses in equine communicate with the nasal cavity through a single opening in the middle meatus called
clinical implications of nasomaxillary opening
drainage of the paranasal sinuses
clinical implications of equine maxillary sinus
increases with age due to teeth wear and growth

tooth decay can lead to sinus infection

position of nasolacrimal duct and infraorbital nerve limit safe surgical field
trephining
alleviation of infection of paranasal sinus by drilling a hole into the skull, allowing fluid drainage and flushing it would
target area for equine euthanasiafrontal sinus1- pharyngeal recess 2- auditory tube openings 3- laryngeal adituslabelguttural pouchesdiverticulum formed by the auditory tube in horses. lined with respiratory epithelium- prone to infection (often fungal). this infection more significant bc important blood vessels course close to the pouch. also, ventral to each pouch are the retropharyngeal lymph nodes, which could trace infection into compartmentschronic infection of guttural pouchpressure on cranial nerves (IX, X)- leads to pharyngeal paralysis and/or laryngeal paralysis damage to facial nerve (VII) Haemorrhage from int. carotid artery- fatalstranglesabscess in retropharyngeal lymph nodes