SGU SVM Anatomy 2: Equine Head
Changes in Equines during physical exertion
--Nostrils dilate maximally --Vascoconstriction of cavernous tissues in nasal submucosa --Dilation of nasal meatuses (especially middle and ventral) --Arytenoid cartilages are maximally abducted --Increase in size of area of rim glottidis --Vestibular and vocal folds are in full abduction during both inspiration and expiration
Incisive Duct
--Paired tube in the floor of the nasal cavity --Connects nasal cavity with the oral cavity Nasal Opening Ventral meatus at the level of the canine tooth Oral Opening In incisive papilla
Boarders of Viborg's triangle
--Angle of mandible --Tendon of sternocephalicus --Linguofacial vein
Caudal Portion of Vestibule
--Cilated pseudostratified --Contains ethmoidal conchae
UNIQUE: Horse Ventral Nasal Sinus
--Divided into rostral and caudal parts by septum --Caudal part forms ventral conchal sinus
UNIQUE: What makes the dorsal concha different in the horse?
--Entirely coiled --Divided into rostral and caudal parts by a septum --Caudal part is enclosed by the dorsal conchal sinus
What important structures have a relationship with the ventral part of the guttural pouch?
--External carotid artery --Lateral and medial retropharyngeal lymph nodes
What important structures have a relationship with the roof/dorsal part of the guttural pouch?
--Foramen lacerum (part of meninges of brain) --CN 9-12 --Chorda tympani --Sympathetic truck beyond the cranial cervical ganglion --Internal carotid artery
EQUINE DENTITION
--Ideally suited to diet of abrasive grass --40 teeth in total --Anisognathous jaw
CLINICAL: Paranasal sinuses
--Infection prone --Equine dentistry --Dehorning procedures in ruminants
Middle Portion of Vestibule
--Lined by ciliated pseudostratified epithelium --Contains the dorsal and ventral conchae
When does the Galvayne's groove appear?
--Longitudinal depression on the labial surface of the upper corner incisor --First appears at the gum line at 10 years
What is the guttural pouch?
--Membranous sac that is an extension of the auditory tube --Larger medial compartment which folds over stylohyoid bone to create two compartments
Frontal Sinus
--Present in all domestic animals, b/w cranial and nasal cavity and orbit --Extends rostrally into dorsal turbinate bone --Single cavity partly separated by bony lamellae
Why is the horses mouth narrow?
--Roots and crowns of cheek teeth (especially in young animals) --Nasal and ethmoid conchae --Pneumatized bones --Thick mucosa
First Portion of Vestibule
--Stratified squamous epithelium
CLINICAL: Criteria and features used for aging
1. Eruption information 2. Wearing features of incisor teeth --> Cup disappearance --> Dental star appearance --> 7-year hook --> Galvaynes groove
Maxillary Sinus
1. Rostral maxillary sinus 2. Caudal maxillary sinus --Separated by oblique septum, situated about 5cm, from rostral end of facial crest
Eruption of Permanent Canine
4-5 years
Eruption of Permanent 1st premolar
5-6 months
When does the cup disappear generally?
8 years old, and enamel spot forming the bottom of the cup remains
Paranasal Sinuses
Air filled diverticula from nasal cavity lined w/ mucosa --Invaginations of nasal epithelium into adjacent bones and some nasal conchae Conchofrontal Sinus Maxillary Sinus
NOSE
Apex Nasal Septum
Spatulate
Apex of the tongue
CLINICAL: Purpose of floating
As a result of anaisognathism --Vestibular side of lower teeth wear faster than lingual side BUT lingual side of upper teeth wear faster leading to sharp edges Require floating to eliminate them, or they will injure the tongue and cheek
Turbinate vs. Original Part of Sinuses
As the concha run within the sinuses, they create their own little sinuses, making each sinus have both a medial turbinate part, and lateral original part Rostral Maxillary Sinus Incorporates ventral conchal sinus/turbinate Frontal Sinus Incorporates dorsal conchal sinus/turbinate
Enamel spot vs. Dental Star
As the teeth wear away, they show... Enamel Spot Presence of infundibulum or cup, little dark spot Dental Star Secondary darker dentine that fills the pulp cavity, aging mechanism
UNIQUE: What makes the sublingual caruncle different?
At level of canine teeth, it only has one duct because there is no monostamatic duct of the sublingual salivary gland
Respiratory Rate of Equines
At rest 8-12 per minute Exercise 150 per minute
CLINICAL: Why is the horse an obligate nasal breather?
Because the relationship of the soft palate with the oropharynx makes it very difficult to breathe through its mouth
CLINICAL: Wolf teeth
Can be problematic, often removed even if they do erupt
Which teeth have no infundibula?
Canine and Cheek teeth
What teeth are not hyposodont in equines?
Canine and P1
Which teeth only sometimes develop?
Canines Stallion: All 4 canines are present Mares: May be absent or poorly developed First Premolars Usually do not develop in either gender but when they do present in upper arcade called Wolf teeth.
Dorsal lingual cartilage
Cartilage cord beneath the mucosa
Surgical Boundaries of the Maxillary Sinus
Caudal Limit Rostral border of orbit Rostral limit Line from rostral end of facial crest to infraorbital foramen Ventral boundary Facial crest Dorsal boundary Line from infraorbital foramen parallel to facial crest
Infundibulum
Centrally placed depression in the occlusal surface of an incisor
CLINICAL: Differences in Equine Lips
Commissures are rostral, not allowing the the oral cleft to be able to open widely --Clinical exam and intubation are difficult
When the dorsal conchal sinus and frontal sinus combine what do they form?
Conchofrontal sinus
Which type of teeth have cups vs. no cups?
Cups Incisors No Cups --Cheek teeth, molars and premolars --Infundibula are filled with cementum
Nasomaxillary opening
Curved slit b/w the dorsolateral wall of the skull and curved dorsolateral edge of ventral turbinate
What meatuses does the horse have?
Dorsal Middle Ventral Common
Apex: Equine
Dorsal cartilage does not project far laterally and ventrally (may be absent) No lateral support for apex
What supports the dorsal aspect of other species nose?
Dorsal lateral cartilages
Nuchal Crest
Dorsal projection of occipital bone
Location of Guttural Pouch
Dorsally B/w base of skull and atlas Ventrally B/w pharynx and start of esophagus Laterally Covered by pterygoid mm, parotid and mandibular glands
Which method of aging is more accurate?
Eruption dates
UNIQUE: Soft Palate
Exceptionally LONG --Except during deglutition its free border is wedged against the base of epiglottis --Causes rostral surface to lie against dorsal surface of soft palate Horse is unable to raise the soft palate
Landmarks of Skull
External sagittal crest Supraorbital foramen Nuchal crest Facial crest Nasoincisive notch
Eruption of Permanent Incisors
First Incisor 2.5 years Second Incisor 3.5 years Third Incisor 4.5 years
Nasal Septum
Forms a partition b/w nostrils, divides nasal cavity into right and left halves Caudal Portion Formed by perpendicular plate of ethmoid (osseous) Rostral Portion Cartilaginous and becomes more flexible towards the apex
What are the bones of the roof of the cranium in the ox?
Frontal bone only, it displaces the parietal bones laterally and caudally
Incisors
Func: To crop and cut grass --Table is flat, changes shape with age from oval to round, then back to oval
CLINICAL: Trephination Frontal Sinus
Halfway b/w medial angle of the eye and midline --Can also examine caudal maxillary sinus via frontomaxillary aperture
Cheek teeth and Incisors
High crowns, hypsodont Clinical Crown Part above the gum line Reserve Crown Proximal part in socket
How is the conchofrontal sinus drained?
Indirect drainage via the nasomaxillary opening to caudal maxillary sinus, into the nasal cavity
CLINICAL: What else does the longitudinal plate support?
Infraorbital canal, important if performing trephination of maxillary sinus to drain, DO NOT injure the nerve contained.
Frontomaxillary Opening
Large, oval, opening located on floor of sinus b/w median place and orbit Links frontal sinus directly w/ caudal maxillary sinus
CLINICAL: What teeth roots are in the maxillary sinus?
Last three cheek teeth, sockets occupy a greater proportion in younger animal
What supports the ventral and lateral aspect of other species nose?
Lateral accessory cartilage
Facial Crest
Laterally prominent ridge, most important landmark of the skull as it forms the boundaries of various sinuses
Nasoincisive Notch
Lies between the nasal and incisive bones
Supraorbital Foramen
Located in zygomatic process of frontal bone
How are the rostral and caudal sinuses further divided?
Longitudinal plate divides the ventral half of each sinus into a medial and lateral chamber
Equine Lips
Main prehensile organ of horse, mobile and sensitive
Premolars and Molars
Masticatory area is increased, w/ enlargement of premolar and assimilation with molars to create a continuous grinding surface
Compartments of the Guttural Pouch
Medial Walls Separated dorsally by the rectus capitis mm. and longus capitis mm. Caudal Part Folds over stylohyoid bone creating a small lateral compartment, and a large medial compartment
How does the maxillary sinus communicate with the nasal cavity?
Middle nasal meatus via the nasomaxillary opening
CLINICAL: Trephination Maxillary Sinus
Most often done to reach 3 molars for repulsion Dorsal Limit --To avoid nasolacrimal duct --Line b/w infraorbital foramen and medial palpebral commissure of eye Ventral Limit --Stay above root of teeth --Facial Crest
Auditive Tube
Narrow slit-like tube connecting tympanic cavity w/ nasopharynx --Osseous close to tympanic cavity --Cartilagenous towards the pharynx --Ends at nasopharynx w/ pharyngeal opening
What supports the medial aspect of other species nose?
Nasal septum (and rostral bone in pigs)
UNIQUE: Does the incisive duct open into the oral cavity in the horse?
No
Roof of the cranium
Occipital bone Parietal bone Interparietal bone Frontal bone rostrally
UNIQUE: What muscle of mastication is unique to the horse?
Occipitomandibularis, extends b/w paracondylar process of occipital bone to caudal border of mandible (#4') --Is an extra portion of the digastricus Innvervated: By facial nerve
When does the Seven-Year Hook appear?
Occurs as a result of uneven heat on upper corner incisor, and projects from distal aspect of occlusal surface --Appears at 7yrs --Disappears at 9 yrs --Reappears at 11 yrs
Drainage of Sinuses
Only rostral and caudal maxillary communicate directly w/ nasal cavity Ventral Conchal Sinus Drains into rostral maxillary Dorsal Conchal Sinus Drains into frontal sinus, to caudal maxillary sinus Sphenopalatine, and Middle Conchal Sinuses Drains into caudal Maxillary Sinus
What is the purpose of the occipitomandibularis muscle?
Opening the jaw
What is the function of the incisive duct?
Organ that controls sexual reproductive behavior by means of pheromones
Medial accessory cartilage
Other Species Small Horse Large and S-shaped Gives cartilagenous support to alar fold
Apex
Point of nose, supported by various cartilaginous structures, some species bony structures as well
EQUINE TONGUE
Poorly defined and short median sulcus/groove, thick --If pigmentation appears abnormal, indicative of malignant tumor
Apex: Carnivores and Porcine
Protrudes to some extent from face, and nostrils of apex lead into nasal cavity
What makes up the clinical root?
Reserve crown and true root
CLINICAL: Trephination of Rostral Maxillary Sinus and Caudal Maxillary Sinus
Rostral 25 mm dorsal to rostral end of facial crest, can also inspect ventral conchal sinus Caudal Same level, but towards caudal end of facial crest
Boundaries of Frontal Sinus
Rostral Mid-way between medial angle of the eye and rostral end of facial crest Medially Line 2 cm parallel to medial plane Laterally Ling passing through supraorbital foramen and parallel to medial limit Caudally Vertical line through middle of zygomatic arch
What does the ventral conchal sinus communicate with?
Rostral maxillary sinus
Nasal Septum: Carnivores, Procine, and Ruminants
Rostral part widest along dorsal and ventral margins So the dorsal and ventral lateral nasal cartilage will support lateral wall of apex
External Sagittal Crest
Runs cranially along the midline, and forms temoporal line on either side, before joining the zygomatic process of frontal bone
Nasolacrimal Duct
Runs on dorsolateral aspect of maxillary sinus, be careful to not injure it when performing surgical interventions in maxillary sinus
When does the dental star appear?
Starts as oval, moves more centered as cup disappears First Incisor 8 years (as a transverse line on vestibular surface All incisors 13 years it is centered 15 years, all stars are round
What supports the apex of the equine nose?
Support given dorsally, medially and ventrally by means of the alar cartilages, wing-like structure attached to rostral border of nasal septum (#9)
T/F there is NO communication b/w the two parts of the maxillary sinus?
True, they are completely separate
CLINICAL: Nasal diverticulum
Unique to horse --Blind dorsal cutaneous pouch extending rostrocaudally, created from the dorsal part of the alar fold --When passing a tube, can get caught
CLINICAL: Which meatus is used for stomach intubation?
Ventral meatus
CLINICAL: How can you tell the gutteral pouch is infected?
Viborg's triangle is swollen
CLINICAL: Nasomaxillary opening blockage
When inflamed, mucosa will block the slit and prevent drainage