Equine Anatomy SG 2
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Describe the relation of the alar cartilage to the anatomy of the nostril
Describe the nasal septum of the horse
Made of hyaline cartilage; divides the nasal cavity into left and right parts
What is the false nostril?
Nasal diverticulum - dorsally located blind-ended pouch in the nostril
What is a nasal meatus? How many are present in the nasal passage of the horse? Where are they located?
- Spaces between the conchal bones
- Four meatuses
- Dorsal - between nasal bone and dorsal conchae
- Middle - between dorsal and ventral conchae
- Ventral - between ventral conchae and hard palette
- Common - top of cavity to bottom, space between conchae bones and septum
What is the significance of the sublingual caruncle and the sublingual fold in a horse?
- Sublingual caruncle - opening of the mandibular salivary gland
- Sublingual fold - openings of polystomatic sublingual salivary glands
Identify the various lingual papillae of the horse
- Filiform - mechanical
- Fungiform - taste, rounded, along lateral edges
- Vallate - taste, large rounded circular, 2 at junction of root and body of tongue
- Foliate - taste, ridges at root of tongue
Describe the lingual and pharyngeal tonsils of horse
- Lingual tonsils - found at root of tongue
- Pharyngeal tonsils - dorsolateral wall of pharynx; diffuse scatterings of tissue under mucosa; cobblestone appearance during inflammatory reaction
Identify the palatoglossal and palatopharyngeal arches on a gross specimen
- Palatopharyngeal arch - dorsal to esophagus
- Palatoglossal arch - soft palate to tongue
What are the divisions of the oral cavity?
- Vestibule - space lateral to teeth between lips and cheek
- Oral cavity proper - medial to teeth
What are the divisions of the pharynx?
Where is the pharyngeal orifice of the auditory tube? Identify the diverticulum of the tube. What is this structure called? Is it present in the dog?
- Pharyngeal orifice is in the nasopharynx
- Diverticulum is the gutteral pouch - not present in the dog
Identify the cartilages of the larynx
- Epiglottis - cuneiform process
- Arytenoid (paired) - corniculate, muscualr, vocal processes
- Thyroid - body (thyroid notch), lamina (rostral cornu, thyroid fissure, caudal cornu)
- Cricoid - lamina, arch
Where are the thyroid foramen and thyroid notch of the thyroid cartilage located?
- Thyroid foramen - space under rostral cornu
- Thyroid notch - space between lamina and body
What is the anatomic significance of the cricothyroid and cricotracheal ligaments or membranes?
- Cricothyroid ligament - passes from cricoid to thyroid cartilage, filling the thyroid notch (incision for laryngostomy)
- Cricotracheal ligament - attaches larynx to trachea
Identify the three processes of the arytenoid cartilage
- Muscular process
- Vocal process
- Corniculate process
Identify the bones of the hyoid aparatus
- Basihyoid - lingual process
- Tympanohyoid (cartilage)
Where is the lingual process of the basihyoid found? Is it present in the dog?
Attached to the basihyoid bone and embedded in the root of the tongue. Not present in dog
Identify the laryngeal ventricle and the folds of mucosa associated with it
- Lateral folds (blind-ended diverticulum)
- -Vestibular fold - more cranial, covers cuneiform process of epiglottis
- -Vocal fold - more caudal, attached to vocal process of arytenoid
- Median fold - caudal to base of epiglottis
An endotracheal tube passes through the rima glottidis. What is this structure?
Cleft (opening) of the glottis
Identify the three extrinsic muscles of the larynx.
Identify the three pharyngeal muscles and two intrinsic laryngeal muscles
- Pharyngeal muscles: cricopharyngeus, thyropharyngeus, hyopharyngeus
- Laryngeal muscles: cricothyroideus, cricoarytenoideus dorsalis
What structures are innervated by the cranial laryngeal nerve and the recurrent laryngeal nerve?
- Cranial laryngeal n. - cricothyroideus m.
- Recurrent laryngeal n. - motor to all intrinsic muscles
Neuromuscular problem (cricoarytenoideus dorsalis m. paralyzed due to disfunction of recurrent laryngeal n.) of left ventral fold causing a 'roaring' sound from vocal fold flapping
What is the rostral opening of the nasal cavity called?
What is the caudal opening of the nasal cavity called?
Where is the supraorbital foramen and what passes through it?
- Above the eye socket
- Supraorbital n. emerges - block for upper eyelid surgery
Where is the infraorbital foramen and what passes through it?
- Rostral portion of the skull
- Infraorbital n. emerges
- Exit of infraorbital canal
Where is the maxillary foramen and what passes through it?
- Rostral portion of eye socket
- Infraorbital n. enters
- Entry of infraorbital canal
Where is the foramen lacerum and what passes through it?
- Caudal part of the skull ventral to the ear
- CN IX, X, XII
- Internal carotid a. and n.
- Middle meningeal a.
- Mandibular n.
Where is the mandibular foramen and what passes through it?
- On medial side of caudal jaw
- Inferior alveolar a., v., and n. enter jaw (to lower teeth)
Where is the mental foramen and what passes through it?
- Rostral portion of lateral jaw
- Inferior alveolar a., v. and n. exit as mental a., v., n. (to chin)
What passes through the vascular groove (notch)?
- Facial a. goes from medial to lateral side (pulse point)
- Facial v.
- Parotid salivary duct
Compare the orbit of the equine skull with that of the canine
- Zygomatic process of the frontal bone + zygomatic process of the temporal bone + temporal process of the zygomatic bone form the lateral socket of the orbit
- vs. a ligament in dogs
Identify the equine mandibular lymph nodes. Number? Location?
V-shaped area in intermandibular space (more rostral than mandibular salivary gland)
What is the generalized innervation provided by the trigeminal nerve?
Sensory innervation (motor to mm. of mastication)
What is the generalized innervation provided by the facial nerve?
Compare the platysma of the dog with its counterpart in the horse
Platysma of dog = cutaneous faciei + cutaneous colli of horse
Which veins unite to form the external jugular vein?
Linguofacial vein + maxillary vein
Describe/identify the venous drainage of the face
- Transverse facial v.* - superficial; under facial crest
- Deep facial v.* - deep; ventral to transverse facial v.
- Buccal v.* - deep; ventral to deep facial v.
- Facial v. - travels with facial a. (from vascular notch)
- Masseteric v. - on caudal part of masseter (drains)
- Lingofacial v. - border of Viborg's triangle
- Maxillary v. - drains dorsal aspect of face
Identify the individual muscles of facial expression. Which CN supplies motor innervation to these muscles as a functional group?
- Innervated by branches of facial n. (mainly dorsal & ventral buccal branches)
- Cutaneous faciei
- Depressor labii inferioris
- Levator nasolabialis
- Caninus - splits levator nasolabialis
- Levator labii superioris
- Orbicularis oris
- Auricular muscles (superficial)
Identify the salivary glands. Where do they open into the rostral cavity. Compare the glands in the horse to those in the dog.
- Parotid - duct opens on parotid papilla (opposite P4)
- Mandibular - deep to mandible and parotid gland; crescent-shaped; opens on sublingual caruncle
- Polystomatic sublingual - openings along sublingual fold (no monostomatic as in dog)
- Buccal (dorsal and ventral) - dorsal buccal is the zygomatic salivary gland in the dog
Identify the individual muscles of mastication. Which CN supplies motor innervation to these muscles as a functional group?
- Innervated by branches of mandibular n.
Identify the primary branches of the trigeminal nerve. Which are sensory and which are motor?
- Opthalmic n. - sensory
- Maxillar n. - sensory
- Mandibular n. - sensory + motor (mm. of mastication)
Identify the superficial branches of the facial nerve
- Dorsal and ventral buccal branches - motor innervation to mm. of facial expression
- Auriculopalpebral n. - motor innervation to upper eyelid and ear
What is the superficial muscle that lies over the parotid gland?
Describe the anatomic arrangement of the digastricus in the horse. What is the motor innervation?
- Rostral: rostral belly of digastricus (innervated by branches of trigeminal n.)
- Caudal (innervated by facial n.):
- -Occipitomandibularis (inserts on angle of mandible)
- -Caudal belly of digastricus - connected to rostral belly via intermediate tendon (passes through tendon of stylohyoideus)
The common carotid a. terminates by splitting into which branches on the left side? Right side?
- Internal carotid a. - into brain
- External carotid a. - supplies deep structures of the head
What are the branches of the external carotid a.?
- Occipital a.
- Linguofacial trunk
- Masseteric a.
- Caudal auricular a.
- Superficial temporal a.
- Maxillary a. (continuation)
What are the branches of the maxillary a.?
- Inferior alveolar a.
- Caudal deep temporal a.
- Rostral deep temporal a.
- External opthalmic a.
- Buccal a.
- Infraorbital a.
- Descending palatine a.
What are the branches of the superficial temporal a.?
- Rostral auricular a.
- Transverse facial a.
Which neural structure can be seen superficially with the transverse facial vessels?
Transverse facial n.
Where does the internal carotid artery enter the cranial cavity?
Which artery branches off the external opthalmic?
Which artery branches off the infraorbital and passes along the floor of the bony orbit?
Identify the paranasal sinuses
- Conchofrontal sinus - dorsal nasal conchae and space of frontal sinus
- (Frontomaxillary opening) - communication of conchofrontal and maxillary sinuses
- Maxillary sinus - lasteral aspect of skull
- Sphenopalatine - immediately under bone
Describe/identify the internal structure of the paranasal sinuses. Which opening provides communication abetween the conchofrontal and maxially sinus?
- Sinuses are hollow spaces in bones of the skull
- Frontomaxillary opening = communication between conchofrontal and maxillary sinus
The maxillary sinus normally drains into which structure through which opening?
Drains into the middle nasal meatus through the nasomaxillary aperture
Which structures produce the compartmentalization of the maxillary sinus?
- Maxillary septum - divide into rostral and caudal compartments
- Infraorbital canal - divide rostral and caudal into medial and lateral
What are the anatomic boundaries of the conchofrontal sinus?
- Caudal - temporomandibular joint
- Rostral - halfway between medial canthus and infraorbital foramen
- Lateral - zygomatic process of frontal bone
- Medial - midline
What are the surgical boundaries of the conchofrontal sinus?
- Caudal - supraorbital foramen
- Rostral - halfway between the canthus and the infraorbital foramen
- Medial - 2 cm lateral to midline
- Lateral - supraorbital foramen to intersection of medial and rostral limits
What are the surgical boundaries of the maxillary sinus?
- Caudal - medial canthus
- Rostral - infraorbital foramen
- Ventral - facial crest
- Dorsal - infraorbital foramen to medial canthus
What are the major surgical procedures that involve entering the sinsuses?
Dentistry, drainage of infection
Where is the infraorbital canal located? What is its association with the paranasal sinuses?
From the maxillary foramen to the infraorbital foramen - divides the rostral and caudal compartments of the maxillary sinus into medial and lateral compartments
Differentiate the auriculotemporal nerve and the auriculopalpebral nerve
- Auriculotemporal n. - br. of the trigeminal n., transverse facial br. of the auriculotemporal n. provides sensory innervation to the lateral side of the face
- Auriculopalpebral n. - supplies motor innervation to upper eyelid and ear
What is a paranasal sinus?
Hollow air-filled space in bones of skull
Appreciate the three dimensional organization of the guttural pouches
- Boundaries: base of cranium and atlas (dorsal) and extends to level of pharynx and esophagus (ventral)
- Compartments: folds over stylohyoid bone (lateral, smaller) and medial (larger) fuse together
Describe the membrane lining the guttural pouch
How are the guttural pouches related at the midline?
Fuse together at the midline
What is the path of the internal carotid artery through the area of the guttural pouches?
The internal carotid a. is wrapped in the membrane at the caudomedial aspect of the guttural pouch
Which vessel passes between the compartments of the guttural pouch
Linguofacial trunk and CN IX
What are the classic signs of guttural pouch disease?
- Nasal discharge
- Epistaxis (nosebleed) - usually caused by fungal infection of pouch where organism errodes internal carotid a.
- Dysphagia (difficulty swallowing) - CN IX and X closely related to pouch (regulate swallowing)
- Tympany - air trapped in guttural pouch
What is guttural pouch empyema?
Guttural pouch fills with pus
Identify operative sites associated with the treatment of guttural pouch disease
- Viborg's triangly - reach ventral part
- Hyovertebrotomy - incision between stylohyoid and atlas to reach dorsal part
Inflammation of the guttural pouches may cause neural damage that manifests itself by signs of pharyngeal paralysis and dysphagea. Why?
CN IX and CN X (glossopharyngeal and vagus) closely related to pouch (regulate swallowing)
What is the structure associated with the equine iris that is not present in the canine?
Iridic granule (corpora nigrans)
Based on their location and anatomic relationship to adjacent structures, how do you differentiate the medial and lateral retropharyngeal lymph nodes?
- Medial retropharyngeal ln - ventral to external carotid a.
- Lateral retropharyngeal ln - dorsal to external carotid a.
What are the differences between hypsodont and brachydont teeth?
- Hypsodont - large crown, late-forming root, grows continuously
- Brachydont - short crown, definite neck, doesn't grow continuously
What are the deciduous and permanent dental formulas for the horse?
- Di 3/3 Dc 0/0 Dp 3/3
- I 3/3 C 1/1 P 3-4/3 M 3/3 = 40 or 42
Which of the permanent teeth of the horse may be vestigial/absent?
Wolf teeth (upper P1)
Give the anatomic explanation for the formation of points
Maxilla wider than mandible - malocclusion creates edges (lateral cusp on upper, medial cusp on lower)
What is Galvayne's groove?
- Permanent upper I3 - groove retains cement (stains brown)
- Appears at 10 years
- 1/2 way down tooth at 15 years
- Occlusal surface at 20 years
What are dental caps?
Retained deciduous teeth (usually cheek teeth)
What is the 7 year hook?
- Upper I3 - malocclusion of upper and lower arcade as arcade angle becomes more accute
- Disappears at 9 years
- Reappears at 11 years
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