Respiratory Tract Flashcards
What are the species differences in nostrils?
Nasal plate/philtrum in carnivores
Nasolabial plate in cows
False nostril in horses, with true nostril more ventral
Os rostrale in pigs, a splanchnic bone supporting the snout
How are nasal cavities divided up?
Divided into meatuses - a series of passages/air spaces.
- Main ones runs along septum and conchae surface
- Dorsal, middle, ventral and common meatuses
- Ventral meatus leads to nasopharynx so is used to stomach tube horses
What are the paranasal sinuses?
Air filled spaces in pneumatic bones, thought to perhaps be for vocalisation, thermal insulation, protecting the brain or reducing weight of the skull.
- Frontal sinus in frontal bone drains into nasal cavity, except in horses.
- Maxillary sinus in maxillary bone is close to the cheek and teeth so are most important. They are poorly developed in dogs and extensive in horses, where they are at risk of infection and complicated drainage to the middle meatus.
Describe the pharynx in the upper respiratory system.
The oropharynx and nasopharynx are separated by a soft palate.
Part of the pharynx that borders the larynx is the laryngopharynx.
Slit like openings link the nasopharynx to the middle ear to allow equalisation of atmospheric pressure.
What is the hyoid apparatus?
A series of small bones, all bilateral except the basihyoid bone. Hyoid apparatus suspends larynx and tongue from the skull.
- Tympanohyoid cartilage articulates with mastoid process of skull.
- Large animal basihyoid has a lingual process to support the tongue.
What is the mnemonic to recall the bones in the hyoid apparatus?
The = tympanohyoid Sick = stylohyoid Elephant = epihyoid Can = ceratohyoid Be = basihyoid Treated = thyrohyoid
Name and describe the 4 pieces of cartilage that suspend the larynx from the skull.
Epiglottis - prevents food entry into trachea in swallowing. Has elastic cartilage for flexibility and is retrovelar in horses so they cannot breathe through their mouths as obligate nasal breathers.
Thyroid - U-shaped part of larynx.
Arytenoid - have processes for intrinsic laryngeal muscles and vocal ligament can attach.
Cricoid - forms a complete ring.
What is the function of the larynx?
Regulates air entry into the trachea and has a role in vocalisation, passing air through glottis to produce sound.
What are the species differences of the larynx?
Cats - sensitive laryngeal muscosa. Incubation may trigger a potentially fatal laryngeal spasm, so anaesthetic sprayed before endotracheal tubing.
Horse and dog - laryngeal ventricle has vocal fold caudal and ventral to it. Has a vocal ligament with mucosal covering, which is attached to arytenoid process and thyroid cartilage floor. Rostral to laryngeal ventricle is false vocal fold.
What are intrinsic laryngeal muscles?
Alter tension in vocal fold via adduction and abduction to alter size of glottis.
Most clinically relevant muscle is dorsal cricoarytenoideus muscle, which is innervated by caudal recurrent laryngeal nerve. Upon contraction, it rotates arytenoid and abducts vocal fold to enlarge glottis.
What is laryngeal hemiplegia?
One sided paralysis of larynx due to damage of recurrent laryngeal nerve, paralysing cricoarytenoideus muscle. No abduction of vocal fold or enlargement of glottis, impeding air flow.
Describe the trachealis muscles and the mucosa of the trachea.
Trachealis muscle bridges gap in cartilage ring and controls diameter of the trachea with smooth muscle.
Mucosa - pseudostratified columnar ciliated epithelium, containing mucous glands to produce mucus ad coughing reflex when irritated.
What is the guttural pouch?
Only in horses and some desert dwelling rodents.
Is a diverticulum of the auditory tube, a pocket that bulges with air. It connects the middle ear to the nasopharynx. May be involved cooling the brain. Pharyngotubal opening is guarded by flaps and has blood vessels and nerves passing through it. Is subject to mycotic infections due to warm and wet environment.
What is the position of the trachea?
Trachea enters thorax with the oesophagus via the thoracic inlet and is right of the oesophagus. Tracheal bifurcation is at the level of the 5th rib.
What is the species differences in the bronchial tree?
Pigs and ruminants - have a tracheal bronchus at the level of the 3rd rib, cranial to the tracheal bifurcation. It is a separate lobar bronchus and aerates cranial lobe of the right lung.
