What are the boundaries of the pharynx?
- The boundaries of the pharynx are (pretty good pictures on TVA 117, 118):
a. Nasopharynx: rostrally by soft palate and hard palate, dorsally by nasal septum, caudally by roof of the nasopharynx, ventrally by palatopharyngeal arch
b. Oropharynx: dorsally by soft palate, ventrally by tongue (it ends caudally at the end of the soft palate/start of the epiglottis)
c. Laryngopharynx: dorsally by epiglottis, caudally by the trachea
d. Overall pharynx: dorsally by nasal septum, rostrally by hard palate, caudally by trachea and roof of nasaopharynx, ventrally by tongue
What is/are the alar cartilages, vomer, ostium, orifice, meatus, pharynx, and auditory tube?
- Alar cartilage: cartilage that supports the nasal rim of the nostril (important because horses are obligate nose breathers and the cartilage and muscles can flare them wide)
- Vomer: a gutter-shaped bone supporting the floors of the cartilaginous nasal septum; it is caudal ventral in the septum
- Ostium: mouth or orifice, opening into a tubular organ, area between 2 distinct body cavities (so in this case, I think he is referring to the intrapharyngeal ostium which, in the horse, seals the opening to the nasopharynx from the larynx)
- Orifice: the entrance or outlet if any body cavity; any foramen, meatus, or opening (in the notes, Dr. Cox refers to the auditory tube orifice which opens into the nasapharynx)
- Meatus: an opening or passage; there are 4 nasal passageways (there is a good picture in TVA 486):
i. Ventral meatus: largest, ventral to ventral concha (where a stomach tube is passed)
ii. Middle meatus: between dorsal and ventral conchae
iii. Dorsal meatus: dorsal to dorsal concha
iv. Common nasal meatus: lateral to nasal septum (unites the other meati) - Pharynx: crossroads of the digestive and respiratory tracts (a.k.a. the throat)
- Auditory tube: narrow channel connecting the nasopharynx to the middle ear
What is an obligate nasal breather? What species have this trait?
-An obligate nasal breather is an animal that can only breath through the nostrils and not through the mouth (i.e. horses)
- How do tonsils differ from lymph nodes? Describe the unique anatomy of the bovine palatine tonsil (TVA p.118).
- Tonsils are lymphoepithelial structures made up of aggregations of unencapsulated lymph nodules within various mucosa. Lymph nodes are made up of lymphoid tissue as well, but consist of an outer cortical and an inner medullary part. They are the main source of lymphocytes for the blood. The bovine palatine tonsil has a unique structure. It is sort of like a leaf with the leaf veins opening up into the oropharynx (that’s the best description I can come up with…see TVA 118 for a picture which might make it more clear). This means that it is buried deep and only an orifice is visible from the oropharynx.
What is the piriform recess and what is the functional significance of it?
The piriform recess is a pair of gutters that run beside the rostral projection of the larynx, below the epiglottis, and into the pharynx. They are lateral to the larynx and form the ventral part of the laryngeal pharynx. It is helpful to the ox because it lets saliva “dribble” down the esophagus without swallowing allowing mass amounts of saliva to buffer the rumen.
What is the topography of the equine auditory tube diverticula? What is their clinical significance? What vessels, nerves and lymph nodes lie adjacent to them?
The equine auditory tube diverticula = the guttural pouches. To see the topography, it would probably be most clear to look at TVA 500, but I will give my little description here. It is divided into right and left guttural pounches by a septum. Each side is then divided into medial and lateral compartments by the stylohyoid bone (comes up from ventrally and reaches about half way up the guttural pouch). The medial retropharyngeal lymph nodes bulge into the guttural pouch ventrally to the pouch and medially to the stylohyoid. The longus capitis ventralis bulges into the pouch dorsally along the midline (it connects to the dorsal end of the septum and it kind of looks like the septum comes from the rectus capitis ventralis, but I’m not sure about that). Basically it is ventral to the brain, dorsal to the esophagus and larynx, and medial to the mandible. There are a lot of vulnerable structures lateral to the pouches. These make the pouches clinically significant. They are the internal carotid artery (caudal and then dorsal surface, can hemorrhage into the pouch if eaten away by aspergillus which is a bacterial family), the external carotid artery (lateral surface), retropharyngeal lymph nodes (lateral surface), and cranial nerves IX, X, XI, and XII.
What muscles pull the hyoid apparatus rostral and caudal? How could you pull the larynx forward to aid intubation?
The hyoid apparatus is pulled caudally and ventrally by the sternohyoideus and thyroideus and rostrally by the geniohyoideus. Pulling the tongue will make the larynx move forward to help with intubation.
Which component of the hyoid apparatus is the largest and which bears a lingual process in the horse ? Where is the hyoid apparatus attached to the skull?
stylohyoid bone is the largest
- basihyoid bone(the lingual process is where the base of the tongue attaches)
- at the base of the skull by the cartilage of the auditory tube (tympanohyoid cartilage)
What is the only hyoid bone to cross the midline?
- basihyoid bone
What are 4 functions of the glottis in domestic mammals?
- It acts as a valve to close off the respiratory pathway in order to:
1. Prevent entry of good or other debris into the trachea
2. Create a negative pressure in the thorax by inspiration against a closed glottis. This then allows aspiration of ingesta into the thoracic esophagus for regurgitation
3. Trap air in the chest during the abdominal press in defecation and parturition. The air trapped in the lungs serves to stabilize the diaphragm for the abdominal press.
4. Dislodge foreign matter from the vestibule by coughing and causing a forced expiration against a closed glottis which opens up slightly to release a “blast” of air to dislodge debris.
Differentiate between the glottic cleft and the glottis.
- glottic cleft = the narrow passageway through the glottis
- glottis = vocal folds + arytenoid cartilages and covering mucosa
What is the shape, composition and position of the laryngeal cartilages? Which is paired and which forms a complete ring?
- epiglottis: shape = flap, composition = elastic cartilage, position = entry to larynx
- thyroid cartilages: shape = U shaped and large, composition = hyaline cartilage, position = cradles larynx
- cricoid cartilages: shape = ring, composition = hyaline cartilage, position = surrounds larynx, wide dorsally to furnish attachemtn for the cricoarytenoideus dorsalis m.
- arytenoid cartilage: shape=small and triangular, composition = hyaline cartilage, position = ventral angle is the vocal process to which the vocal ligament and vocalis m. attaches, lateral angle is the muscular process to which the cricoarytenoiodeus dorsalis m. attches, articulates with cricoid cartilage
- arytenoid is paired
- cricoid forms a complete ring
What are 2 unique features of the equine thyroid cartilage and what is their clinical significance?
- There is a prominent thyroid notch of the ventral aspect of the thyroid cartilage. This notch divides the thyroid cartilage into left and right parts which are joined cranially by a narrow connecting portion, which is ossified to strengthen their connection. Clinically, the thyroid notch is a useful location for entry into the larynx for ventriculectomy (aka roaring surgery)
- I guess that there is an ossified portion is the second unique feature. Does anyone have any input?
Why is the respiratory tract lined with cartilage from nostril to small bronchioles.
-The respiratory tract is lined with cartilage from nostril to small bronchioles because it needs to maintain patency (unobstructed; open) of the airways.
What is the relationship of vocal folds to the laryngeal ventricle?
- The vocal folds are related to the laryngeal ventricle b/c animals with true vocal folds have ventricles. The mucosa from the vocal folds must “curve cranially” so it will be able to reach the epiglottis, as it curves forward it creates a laryngeal ventricle.
True vocal folds and laryngeal ventricles are found in which domestic species? What is found in other species and how does this effect phonation (sound production)?
-True vocal folds and laryngeal ventricle: human, dog, horse, pig
Ruminants and cat have vocal ridge=softer vocalization than animals with true vocal folds
What are the major muscles of the larynx, their function, and nerve supply?
-Cricoarytenoidus dorsalis m.
F: dialate the glottis, pulls the vocal folds lateral
N: Reccurent laryngeal nerve
-Cricoarytenoideus lateralis m.
F: constricts the glottis, pulls vocal folds medially
N: Reccurent laryngeal
-Vocalis muscle
F: Relaxes the vocal fold, pulls arytenoid cartilage downward
N: Reccurent laryngeal nerve
-Cricothyroidius muscle
F: ?
N: Cranial laryngeal nerve
What is the afferent nerve of the gag reflex that occurs when foreign material enters the larynx?
-Cranial laryngeal nerve is the afferent nerve of the gag reflex for when foreign material gets in the larynx.
Why is roaring called laryngeal hemiplegia and what anatomic differences in the path of the laryngeal nerve supply accounts for this?
Roaring is paralysis of the larynx due to recurrent laryngeal nerve damage. Most of the cases are left side only (hemiplegia). So…it affects the larynx (laryngeal) and mainly the left side (hemiplegia). It is mostly on the left because the intrathoracic course of the recurrent nerve differs from left to right…the left side is more susceptible.
