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Equine Upper Respiratory Tract - Horse Anatomy (view source)
Revision as of 21:45, 15 November 2012
, 21:45, 15 November 2012→Larynx
==Larynx==
==Larynx==
===Overview===
The larynx is situated below where the [[Pharynx - Anatomy & Physiology|pharynx]] divides into the trachea and the [[Oesophagus - Anatomy & Physiology|oesophagus]]. It is contained partly within the rami of the mandible and extends caudally into the neck. It is important during breathing, vocalisation and deglutition (swallowing). The cartilagenous larynx can be manually palpated in the living animal and is commonly implicated in respiratory conditions such as [[Laryngeal Paralysis|roaring]].
The [[Pharynx - Anatomy & Physiology|pharynx]] is located rostrally to the larynx, whilst the trachea is located caudally. The larynx is suspended from the [[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]]. It is bilaterally symmetrical and 'tube-shaped' and can be described as a '''musculocartilagenous organ'''.
===Laryngeal Cartilages===
====Thyroid Cartilage====
The thyroid cartilage is a [[Cartilage - Anatomy & Physiology#Hyaline Cartilage|hyaline cartilage]] and forms most of the floor of the larynx. The fusion of the two lateral plates varies in different species. The rostral part forms the 'Adam's apple'. The thyroid cartilage articulates with the '''thyrohyoid bone''' and the '''cricoid cartilage'''. It becomes brittle as the animal ages.
====Arytenoid Cartilage====
The arytenoid cartilages are paired, triangular shaped [[Cartilage - Anatomy & Physiology#Hyaline Cartilage|hyaline cartilages]]. They lie either side of the cricoid cartilage and articulate with the rostral part of it. A '''vocal process''' is present on the caudal surface where the vocal folds attach; a '''muscular process''' extends laterally and is the origin of attachment for the ''cricoarytenoideus dorsalis'' muscle. A '''corniculate process''' extends dorsomedially.
====Epiglottic Cartilage====
The epiglottic cartilage is an [[Cartilage - Anatomy & Physiology#Elastic Cartilage|elastic cartilage]], which is the most flexible and most rostral type of cartilage. The thinner stalk-like part, is attached to the root of the [[Tongue - Anatomy & Physiology|tongue]], the body of the '''thyroid cartilage''' and the '''basihyoid bone'''. The larger blade-like part lies behind the soft palate and points dorso-rostrally. During [[Deglutition|deglutition]], the large blade part of the '''epiglottic cartilage''' partially covers the entrance to the trachea.
===Vocal Folds===
The vocal folds are made of (slightly stiffer) elastic ligaments and pass between the '''arytenoid cartilages''' and the '''laryngeal floor'''. They run caudodorsally, with the ligament positioned medially and the '''vocalis muscle''' laterally. Fat surrounds the vocalis muscle. The vocal folds form part of the glottis and secrete mucous. They are used for vocalisation.
===Vestibular Folds===
The vestibular folds are made of (slightly stiffer) elastic ligaments. The '''vestibular ligaments''' are rostral to the '''vocal ligament'''. The vestibular folds run caudodorsally, rostral to the vocal folds with the ligament positioned medially and the '''vocalis muscle''' laterally.
===Intrinsic Musculature===
The intrinsic laryngeal muscles produce changes in caliber of the rima glottis by abducting and adducting the corniculate processes of the arytenoid cartilages and the vocal folds and hence, altering airway resistance. The principle muscle to widen the glottis is the ''cricoarytenoideus dorsalis''. The ''thyroarytenoideus'', ''arytenoideus transversus'', and the c''ricoarytenoideus lateralis'' muscles adduct the corniculate processes of the arytenoid cartilages, narrowing the glottis and therefore protecting the lower airway during swallowing.
====Cricothyroid muscle====
The cricothyroid muscle is innervated by the '''cranial laryngeal nerve''', a branch of the vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]). It moves the '''cricoid''' and '''arytenoid''' cartilages caudally to tense the vocal folds.
====Dorsal cricoarytenoid muscle====
The dorsal cricoarytenoid muscle is innervated by the '''caudal laryngeal nerve''', a branch of the vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]). It runs from the dorsal surface of the '''cricoid cartilage''' to the '''arytenoid cartilage'''. It abducts the vocal process and therefore the vocal fold to widen the glottis and is the principle abductor of the larynx.
====Lateral cricoarytenoid muscle====
The lateral cricoarytenoid muscle is innervated by the '''caudal laryngeal nerve''', a branch of the vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]). It adducts the vocal processes and narrows the glottis.
====Thyroarytenoid muscle====
The thyroarytenoid muscle is innervated by the '''caudal laryngeal nerve''', a branch of the vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]). It runs from the laryngeal floor to the '''thyroid cartilage''' and '''arytenoid cartilage''' and alters the tension of the vocal and vestibular folds. It forms part of the '''sphincter muscular arrangement'''.
====Transverse arytenoid muscle====
The transverse arytenoid muscle is innervated by the '''caudal laryngeal nerve''', a branch of the vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]). It completes the '''muscular sphincter arrangment''' and spans the '''arytenoid cartilages'''.
==Pharynx==
==Pharynx==
==Trachea==
==Trachea==