Ch.46 Larynx Flashcards
Cartilages of the larynx
- Cricoid
- Thyroid
- Epiglottic
- Arytenoid x2
- Corniculate processes x2
what inserts on the muscular process of the corniculate process
Cricoarytenoideus Dorsalis CAD
What cartilage are the thyroid, cricoid and arytenoids composed of
Hyaline cartilage which can ossify with age and trauma
How does the hyaline cartilage of the cricoid differ from that of the arytenoid
Cricoid is stiff 2 - 2.5 megapascal (MPa)
Body of Arytenoid less stiff 0.42 MPa
How does the hyaline cartilage of the larynx differ from articular hyaline
Much stiffer with a denser structural arrangement and collagen content
Articular 0.21 MPa
Larynx 0.42 - 2.4 MPa
Which part of the larynx is made from elastic cartilage
Apex of the corniculate process
Epiglottis
What holds the epiglottis to the thyroid cartilage
Thyroepiglottic ligaments
What are the intrinsic muscles of the larynx
PAIRED
1. Cricoarytenoideus Dorsalis
2. Cricoarytenoideus lateralis
3. Cricothyroideus
4. Thyroarytenoideus ventricular and vocalis
UNPAIRED
1. Arytenoideus transversus
Action of CAD
- Abduct the corniculate processes of the arytenoids
- Tense the vocal folds
Action of Arytenoideus transversus
Adducts the arytenoids
Action of the Thyroarytenoideus arytenoideus transversus and cricoarytenoideus lateralis
Adduct the arytenoids
Action of the cricothyroideus
Tense vocal folds during vocalisation
Efferent motor innervation of the intrinsic mm of the larynx
Recurrent laryngeal branch of vagus nerve
Except for cricothyroideus which receives efferent motor innervation from the external branch o the cranial laryngeal nerve
Extrinsic laryngeal muscles
- Sternothyroideus
- Thyrohyoid
- Thyropharyngeus
- Cricopharyngeus
- Hyoepiglottic
Depth and capacity of the ventricles
2.5cm deep
5 - 6ml capacity
Bounded by medial surface of thyroid cartilage
ventricular and vocalis mm
The mechanoreceptors of the laryngeal mucosa receive afferent neural supply from what
Internal branch of the cranial laryngeal nerve a branch of the vagus nerve
What is the source of respiratory reflexes
Sensory mechanoreceptors innervated by the cranial laryngeal nerve
lymphatic drainage of the larynx
Retropharyngeal
Cranial and deep cervical lymph centres
Which grading system is recommended and why
Havemeyer
Validated with a correlation of histopathologic assessment of the CAD and exercising laryngeal grade
Grade II A vs B
II - Arytenoid movements are asynchronous and or larynx is asymmetric at times but full abductiopn can be achieved and maintained
A - Transient asymmetry, flutter or delayed movements
B - Assymmetry much of the time, occasions usually after swallowing or nasal occlusion when full symmetrical abduction is achieved a maintained
Grades III A,B &C
III - Arytenoid movements are asynchronous and or larynx is asymmetric. Full abduction cannot be achieved and maintained.
A - Abduction achieved but not maintained
B - Full abduction never achieved
C - Limited movement. Full abduction never achieved.
Grade IV
Complete immobility
What % of horses with RLN have comorbidities
30%
What % of horses with RLN will show progression o paralysis over 12 months
15%
What is responsible for stabilisation of the vocal cord
Cricothyroid mm innervated by cranial laryngeal n
and CAD
Causes of bilateral laryngeal paralysis
Organophosphate toxicity
CNS disease eg EPM
Hepatic dysfunction
Encephalopathy
Lead toxicity
Australian string halt
What structures are derived from the fourth branchial arch
- Lateral wings of the thyroid cartilage
- Crico-arytenoid articulation
- Cricoid cartilage
- Cricothyroideus
- Cricopharyngeus
- Thyropharyngeus
4th branchial arch defect also known as
Cricopharyngeal-laryngeal dysplasia
What is the reported incidence of 4bad
0.02%
What is evident on palpation of a horse with 4 bad
Deficit of wing of thyroid on one or both sides
Easily palpated gap between cricoid and thyroid cartilages due to absence or atrophy of the cricothyroid muscle
What is observed with rostral displacement fo the soft palate
Margin of the ostium intrapharyngeum is displaced rostral to the dorsal tips of the corniculate processes of the arytenoid cartilages
What can be observed on radiographs of a horse with 4 bad
Air in the proximal oesophagus due to dysfunction of the cranial oesophageal sphincter
What is found in horses with collapse of the apex of the corniculate process
Widening of the transverse arytenoid ligament
What % of mucosal disease and granulomas of the arytenoid cartilages progress to granulomas or arytenoid chondropathy
10% granulomas
5% chondropathy
What % of epiglottic entrapments are ulcerated
45%
What % of horses with epiglottic entrapment have hypo plastic epiglottis
31-36%
Structures associated with epiglottic retroversion
Hyoepigltticus
Geniohyoid m
a. The laryngeal mucosa contains sensory mechanoreceptors for the detection of different stimuli, including transmural pressure changes, airflow, temperature, and laryngeal motion. These mechanoreceptors receive afferent neural supply from the internal branch of the cranial laryngeal nerve, a branch of the vagus nerve
b. The laryngeal mucosa contains sensory mechanoreceptors for the detection of different stimuli, including transmural pressure changes, airflow, temperature, and laryngeal motion. These mechanoreceptors receive efferent neural supply from the internal branch of the cranial laryngeal nerve, a branch of the vagus nerve
c. The laryngeal mucosa contains sensory mechanoreceptors for the detection of different stimuli, including transmural pressure changes, airflow, temperature, and laryngeal motion. These mechanoreceptors receive afferent neural supply from the internal branch of the recurrent laryngeal nerve, a branch of the vagus nerve
d. The laryngeal mucosa contains sensory mechanoreceptors for the detection of different stimuli, including transmural pressure changes, airflow, temperature, and laryngeal motion. These mechanoreceptors receive afferent neural supply from the internal branch of the cranial laryngeal nerve, a branch of the trigeminal nerve
a. The laryngeal mucosa contains sensory mechanoreceptors for the detection of different stimuli, including transmural pressure changes, airflow, temperature, and laryngeal motion. These mechanoreceptors receive afferent neural supply from the internal branch of the cranial laryngeal nerve, a branch of the vagus nerve
a. The larynx receives arterial blood supply from the cranial laryngeal artery and branches of the ascending pharyngeal arteries.
b. The larynx receives arterial blood supply from the caudal laryngeal artery and branches of the ascending pharyngeal arteries.
c. Venous drainage is provided by the cranial laryngeal and ascending pharyngeal veins, which flow to the external jugular vein via the thyroid vein.
d. None of the above
b. The larynx receives arterial blood supply from the caudal laryngeal artery and branches of the ascending pharyngeal arteries.
Venous drainage is provided by the caudal laryngeal and ascending pharyngeal veins, which flow to the external jugular vein via the thyroid vein.
a. Recurrent laryngeal neuropathy is a unilateral mononeuropathy affecting the recurrent laryngeal nerves.
b. The muscle paralysis results from progressive loss of large myelinated axons predominantly in the left recurrent laryngeal nerve
c. The muscle paralysis results from progressive loss of small myelinated axons predominantly in the left recurrent laryngeal nerve
d. Pathologically, neurogenic atrophy of the intrinsic laryngeal musculature results in progressive loss abductor arytenoid function whilst the adductors are uneffected.
b. The muscle paralysis results from progressive loss of large myelinated axons predominantly in the left recurrent laryngeal nerve
Recurrent laryngeal neuropathy is a bilateral mononeuropathy affecting the recurrent laryngeal nerves.
Pathologically, neurogenic atrophy of the intrinsic laryngeal musculature results in progressive loss of both abductor and adductor arytenoid function
The extrinsic muscles of the larynx are
a. thyrohyoideus, hyoepiglotticus, cricopharyngeus, thyropharyngeus, sternothyroideus
b. geniohyoideus, thyrohyoideus, genioglossus, hyoglossus, hyoepiglotticus, styloglossus, sternohyoideus, sternothyroideus
c. geniohyoideus, thyrohyoideus, genioglossus, hyoglossus, hyoepiglotticus, cricopharyngeus, thyropharyngeus
d.thyrohyoideus, hyoepiglotticus, cricopharyngeus,styloglossus, sternohyoideus, sternothyroideus
a. thyrohyoideus, hyoepiglotticus, cricopharyngeus, thyropharyngeus, sternothyroideus
Common
thyrohyoideus
hyoepiglotticus
sternothyroideus
Larynx only
cricopharyngeus
thyropharyngeus
Pharynx only
geniohyoideus
genioglossus
hyoglossus
styloglossus
sternohyoideus
