Anatomy 2 - Equine Head 2

drraythe's version from 2015-06-05 22:55

lips, mouth, teeth, throat

Question Answer
why are horses more difficult to intubate/do an oral exam on?the commissure of their lips is way more rostral so opening the mouth wide is difficult
what muscle of mastication is unique to the horse? what does it do and where does it run? nn supply?occipitomandibularis mm, it opens the mouth, and extends between the paracondylar process of the occipital bone to the caudal border of the mandible. Don't confuse with the digastricus. FACIAL N SUPPLIES IT.
unique tongue structure of the horse?dorsal lingual cartilage
pigmentation of the horse tongue?abnormal! indicative of a malignant tumor.
What type of teeth do horses have? (mult descriptions)ALL teeth but canines and P1 are HYPSODONT. Also, the cheek teeth are anisognathous (jaws unequal size)
Describe the different ways to categorize the crown and root of a horse tooth.Very long crowns (distal part above gum line = clinical crown; proximal part in socket is the reserve crown. Reserve crown + true root = clinical root.
Describe the features of the occlusal/cutting surface of the cheek toothbears one or two infundibula or cups, lined by cementum. The enamel forms raised ridges (enamel crests) on cutting surface
space between incisors and cheek teeth? anything there?diastemata. Canine tooth can be here (it's useless)
Deciduous dental formula?Di (3/3) Dc(1/1) Dp(3/3) X2= 28
permanent dental formula?I(3/3) C(1/1) P(3/3) M(3/3) X2= 40
how common are canine teeth?in the stallion, all 4 are present. in the mare, they are maybe there. (more likely in lower jaw, only 3% chance in both jaws)
describe cutting surface of incisors? how do they change?table is flat, and changes shape with age from oval, rounded, triangular and back to oval. It also has an Infundibulum (cup)-central cleft lined by cementum.
What are dental cups?in the incisors, the infundibula (funnel like center) make a scoopy little bowl (central cleft) filled with cementum
what is the dental star? which teeth does it have to do with?incisors-- is the secondary , darker dentine which fills the pulp cavity as wear causes the occlusal surface to approach it. "dark area by the cup"
do cheek teeth have cups?no, the infundibula (funnel like center) are filled with cementum
explain how cheek teeth touch each other due to anisognathismlingual ⅓ of the cutting surface of the upper archade makes contact with the vestibular half of the lower archade, in centric occlusion. (inside top touch outside bottom, because lower jaw is smaller. They chew in circles)
what is floating, why do we do it?because the horse has anisognathic teeth, and the top teeth's inner surface wears faster and the lower teeth's outer surface wears faster, the teeth wear into points and can cut the tongue and cheek. filing down the teeth so this doesnt happen is floating.
what teeth do we usually use for aging?the lower incisors
define "Wear" of a toothwhen a tooth has risen to the masticatory level and the enamel begins to wear on the occlusal surface
define "level" of a toothwhen the entire outer enamel ring is in wear and is separated from the inner enamel ring by dentine
which tooth is the 7-year hook on?I3
which tooth is Galvayne’s groove on?I3
two unique aging structures on I3?Galvayne’s groove and the 7-year hook
whats up with the horses sublingual caruncle? only duct of mandibular salivary gland opens through this structure *because there is no monostomatic part of the sublingual salivary gland in the horse.
why cant a horse breathe through its mouth?the soft palate of the horse is really long. except when it swallows, the free part is wedged against the base of the epiglottis, and the epiglottis comes up and rests on the dorsal part of the palate, closing off the throat
how would you surgically access the ventricle of the larynx?the thyroid cartilage is ventrally incomplete. The gap is filled with the circothyroid membrane-- this is where you can access it.
what is/where is the laryngeal ventricle? Boundaries?in the lateral wall of the larynx, against the medial wall of the thyroid cartilage. it opens in the larynx between the vestubular fold rostrally, and the vocal fold caudally.
what are the three portions of the larynx?vestibule, glottis, infraglottic cavity
when resting, resp. rate is? rima glottidis (opening) is what shape? movement of the aretynoid cartilages?8-12 BPM. Diamond shape. BArely move.
when exerting, resp. rate is?~150BPM.
what kind of breathers are horses?obligate nasal breathers
since horses have to breathe through their noses, during physical exertion, what happens? (3)(1) Vasoconstriction of the cavernous tissue (dilate nasal meatus) (2) arytenoid cartilages are maximally abducted (bigger rima glottdis) (3) vestibular and vocal folds are in full abduction during both inspiration and expiration.
the auditive (eustacian) tube is supported by what? goes from where to where?a V-shaped piece of cartilage. (also supports the pharyngeal opening). from middle eat to nasopharynx.
the pharyngeal opening opens and closes when?opens when swallowing, closes on inspiration
what is the gutteral pouch?a membranous sac which is a diverticulum of the auditive tube.
boundaries of the gutteral pouch?between base of skull and atlas dorsally, pharynx and commencement of eso. ventrally. ventrolaterally, the medial retropharyngeal lnn. laterally, the ptygeroid mm and parotid and mandibular glands.
medial boundaries of the gutteral pouchesdorsal part of right and left sac are separated by the ventral straight muscles of the head but below this they meet forming a thin median septum
how is each gutteral pouch divided into a M and L portion? which portion bigger?stylohyoid. Small lateral, large medial
what makes contact with the roof of the gutteral pouch? (9ish)roof at foramen lacerum (hole in skull) so meninges of brain actually touch the pouch here! also CN9-12, tympanic bulla, chorda tympani ( a nerve), part of symp. trunk, internal+external carotid aa, and M+L retropharyngeal LN
why would the gutteral pouch be distended? (4)enflamed medial retropharyngeal ln, air, accumulation of secretory material/exudate, malfxn of eustacean tube
what is gutteral pouch tympany?eusteacean tube malfxn, works like a 1-way valve that only lets air in, As a result a fluctuating swelling may be palpated behind the jaw and also in the parotid the region
what is viborg's triangle? what do we do there? borders?can drain the gutteral pouch here. ROSTRAL border= angle of mandible. CAUDO-DORSAL border= tendon of sternocephalicus. VENTRAL= linguofacial vein
signs of gutteral pouch infection?1*= nasal discharge, swelling of parotid region, carry head/neck abnormally. 2* (because of associated structures) middle ear inflammation, epistaxis, Difficulty in swallowing (glossopharyngeal nerve and vagus), roaring (laryengeal hemiplegia), horner's syndrome
natural, surgical, and alternate ways to drain the gutteral pouch?lowering head partially drains. surgical drain through viborgs triangle (must reflect parotic salivary gland rostrally), or put drainage tube through ventral nasal meatus and into auditory tube to drain

eye, vessels, LNs, salivary glands, clinical

Question Answer
does a horse have a third eyelid? what shape is their pupil?yes, and the pupil is transversely elliptical.
which animal lacks a tepetum lucidum?pig
what is the Granula iridica? what does it do?produce aqueous humor; protect eye from bright light – cast shadows on retina. (aka corpora nigra)
what is the common tributary of the external jugular vein?the linguofacial vein
why are there large veins under the massive masseter muscle?assist in venous return when head is lowered below heart. Also maybe equalizing BP as head is lowered or raised.
which veins are associated with the masseter mm? (3)transverse facial vein, deep facial vein, buccal vein
how does the transverse facial vein run? what does it form?embeds in masseter, ventral to the facial crest rostrally, and the zygomatic arch caudally. it is enlarged below the facial crest to form the transverse facial vein sinus and joins the facial vein rostrally.
where does the deep facial vein run? what does it drain? what does it form?arises in the pterygopalatine fossa, runs deep to masseter, drains the nasal cavity, palate, periorbita and its structures, enlarges to form the deep facial vein sinus
where does the buccal vein lie? how does it communicate? what does it form?deep to masseter, Anastomoses with the facial vein, rostrally, and, a main tributary of the maxillary vein, caudally. The part medial to the masseter m. is enlarged, to form the buccal vein sinus.
what are the LNs of the horse head?Parotid ln., Mandibular ln., lateral and medial retropharyngeal lnn.
where is the parotid LN? what does it drain? where do its efferents go?caudal to the angle of the mandible, and ventral to the ear, Drains eye, ear, lips, rostral and dorsal superficial muscles of the head, skin of the head. Efferents go to the retropharyngeal lnn.
where do the mandibular lnn live? how many? drain what? efferents where?in the intermandibular region, there are two rows which join just cranial to the basihyoid bone, and form a V-shaped gland. Drain nostrils, palate, tongue and jaws. Efferents go to *retropharyngeal lnn. and cranial deep cervical lnn.
where do lateral retropharyngeal lnn live? drain what? efferents where?dorsocaudal to the mandibular salivary glands and ventral to the wing of the atlas, A chain of lnn. along the external carotid artery on the lateral wall of the guttural pouch, and medial to the occipito-mandibularis muscle. Drain deep parts of head, efferents to *medial retro. LN, cranial deep cervical and tracheal duct.
medial retrophar. LN where? drain what? drain to?Dorsolateral to the pharynx, and ventral to the guttural pouch. drain all other LNs (MASTER LN OF HEAD!!!!) and efferents form thoracic duct
unique about sublingual salivary gland?has only the minor, polystomatic portion.
diff of secretion in major vs minor salivary gland?minor= everywhere and mucus. major= in distinct glands and seromucus
roaring is caused by what? where is it usually? what happens to the ventricle?paralysis of laryngeal mm. usually on LEFT (bilateral rare). ( Cause still largely speculative(affections of the left tracheobronchal lymph nodes have been implicated, but evidence is not solid) ) Affected muscles are atrophic, therefore, the laryngeal ventricle enlarges.
mm that are paralyzed in roard are supposted to beabducting vocal cords, they arent, so air obstructed when moving in, ventricle fills with air and narrows rima glottidis, cord vibrates to make roar sounds
what kind of operation is done to fix roaring, and what is involved?ventriculectomy operation. Entry into the laryngeal ventricle through the criothyroid membrane inthe ventral notch of the thyroid cartilage. destroy mucosal lining of ventricle. attach arrytnoid cartilage to thyroid cartilage.
why is intubation hard? how do you position horse?Narrow rima oris (rostral opening into mouth). The longitudinal axis of both the head and larynx are at an angle; therefore, extend the head moderately, to align the axis.
how do you prevent/treat cribbing?Prevented or treated by resecting the omohyoid, sternocephalic and sternothyroid muscles.
where are the most common sites of facial nerve damage? (2)(1) Over the caudal border of the mandible (ventral to the temporomandibular joint) (2) where the buccal branches run over the masseter muscle
signs that there is facial nn damage?nostrils cant dilate. cheeks bulge w/food (no buccinator working), blinking lost, corneal drying, eyelids cant close, lower lid droops so tears spill onto cheek, ear hangs/pulled back (auricular n), prehension impeded (no upper lip use) as well as drinking (need lips). If bilateral paralysis, mandibular n affected--> jaw drop.
why doesnt upper eyelid droop in facial n paralysis?upper eyelid does not droop because the occulomotor n. activates the Levator palpebrae superioris m
what nerve to block for dental work?maxillary n.
how do you block maxillary n for dental? (peterson block)PETERSON BLOCK- anesthetises all teeth but only used for last four, as rest can be blocked at infraorbital foramen. needle ventral to the lateral angle of the eye and directed medially and slightly rostro-dorsally. advance needle to reach the maxillary nerve between the maxillary foramen and foramen rotundum.
how do you block maxillary n for dental? (NOT peterson block)All mandibular teeth are blocked (but used for last four teeth; other teeth blocked at mental foramen) Blocked at mandibular foramen region, on medial aspect of the mandible. Foramen lies ventral to lateral canthus of eye, and at the level of the upper cheek teeth (with mouth closed).