Skull, Head and Neck Flashcards
What is the clinical relevance of the skull?
Injuries
Regional anaesthesia
Dentistry
Euthanasia of farm species
Dehorning and disbudding
Sinus infections
List the bones of the skull.
Frontal
Occipital
Parietal
Temporal
Zygomatic
Palatine
Maxilla
Incisive
Nasal
Basisphenoid
Pterygoid
Presphenoid
Ethmoconchae
Ethmoidal
Lacrimal
Sphenoid
Vomer
Name and describe the features of the mandible.
- Coronoid process is a large muscle attachment area.
- Ramus leads up to the coronoid process.
- Condylar process articulates with the skull.
- Angular process is also involved in muscle attachment.
Describe how a horse skull differs from a dog’s.
Small braincase area at the very caudal end of the skull.
Palpable landmarks on the outside of the animal’s face:
- Facial crest, laterally to the cheek teeth
- Nasoincisive notch, notch under the nasal bones where soft tissues sit.
How are the holes of the ventral surface of the equine skull different?
On the ventral surface, there is a big hole and several other, instead of many small holes in the base of the skull. So in the horse, a lot of the structures that are passing through the holes are rather larger, and lots of small holes would make the bone between them so thin.
How is the equine mandible different?
Isn’t quite the same angular process but there is a broad attachment for muscles for chewing.
Describe how the bovine skull differs from the canine.
- Relatively small area for brain protection.
- Frontal bone extends all the way back up the top of the head.
- So parietal bones actually pushed caudally on to the back of the skull
Describe how the porcine skull differs from the canine.
- Relatively small area for brain protection.
- Pig has high sloped forehead
Name the 4 main joints of the skull.
Temporomandibular joint (TMJ)
Mandibular symphysis
Atlantooccipital joint
Atlantoaxial joint
What is the function of the temporomandibular joint?
Where chewing motions will take place.
What is the function of the mandibular symphysis?
Secondary cartilaginous (containing fibrocartilage) joint, holding mandible together cranially. Fractures are common in ‘high-rise’ falls, RTAs and dog fight, take care when doing dentistry.
What is the function of the atlantooccipital joint?
1st joint between skull and spine. Allows for flexion and extension at this joint.
What is the function of the atlantoaxial joint?
Between atlas and 2nd vertebrae. Allows rotation.
What are sinuses?
- Diverticula of the nasal cavity that excavate the skull bones. Largely after birth and alters conformation of the head.
- Do retain connection with nasal cavity but generally openings are small.
- All species have frontal and maxillary sinuses.
Describe the species differences of the frontal sinus.
- Frontal sinuses are in all species except the horse.
- The front sinus drains into the back of the nasal cavity via the ethmoidal meatuses.
- In the horse, the frontal sinus drains into the caudal maxillary sinus.
- Considerations for pre-slaughter stunning: in the pig, the extent and bone support of the front sinus means that it is a poor candidate for captive bolt stunning, as bolt will not make it to the brain.
Describe the species differences of the maxillary sinus.
- Maxillary sinus in the dog is called a maxillary recess.
- In the horse there are caudal and rostral compartments.
- Drain into the nose via the nasomaxillary opening.
What is the clinical significance of the maxillary sinus of the horse?
In the horse, the maxillary sinus is really close to the roots of the cheek teeth. Abscesses can invade this sinus and cause sinus infection, which can invade the teeth and cause teeth rot.
Describe the properties of horn.
- Horn is permanent bone covered by horn
- Grows continuously, whereas antlers are shed yearly
- Invaded by frontal sinus early in life at around 6 months
Why is removing horn a serious surgery?
Has cornual diverticulum and epithelium running up the hole itself. So removing a horn is quite a serious surgery as a result, as it interferes with living epithelium.
What are the requirements and risks of dehorning?
- Dehorning must be performed by a veterinary surgeon
- Should not be a routine procedure
- Risks of injury to the vet and other people involved
- Risks to cow include bleeding and infection
What is disbudding?
- Horns are easier to prevent than remove
- Usually done using hot irons
- Local anaesthesia still required at the corneal nerve and is below a ridge, called the temporal line.
Describe the local anaesthetic required for disbudding.
- Block the cornual nerve (branch of V2)
- LA deposited subcutaneously
- Midway between lateral canthus of the eye and base of horn along the temporal ridge
- For larger horns, also infiltrate LA along caudal aspect of the horn to desensitise the subcutaneous branches of the 2nd cervical nerve
What is the shape and clinical significance of horns in goats and sheep?
- Horns cross section determines shape: goat has oval and grow straight dorsally, and sheep have triangle so curl.
- Clinically, these may grow into the head and cause pressure necrosis.
Describe the anaesthetic required to disbud goats.
- Innervation is from cornual branch of zygomaticotemporal nerve (branch of V2)
- Innervation form the cornual branch of the infratrochlear nerve
- Disbudding of kids advised under general anaesthesia
- Must be performed by veterinary surgeon
Define fossae and foramina.
Fossae – the ‘ditches’ in which things sit.
Foramina – the holes through which structures pass, usually nerves, arteries and veins.
What are the cranial nerves?
Many of the nerves passing through the skull in foramina are cranial nerves – a class of nerve which do not go through the spinal cord but instead innervate structures of the head and neck via direct contact with the brain. Cranial nerves, CN, can be numbered I-XII. Most visible on the base of the brain. Vagus = CNX
Describe the facial nerve CNVII and its branches.
Motor innervation to the muscles of facial expression.
- A small cervical branch heading to the neck region
- Auriculopalpebral branch going to structures of the palpebral, the upper eyelid and the acumen around the ear
- Dorsal and ventral buccal branches
Describe the trigeminal nerve CNV and its branches.
Provides motor innervation to muscles for chewing and biting and sensory innervation to surface of the face. They sit much deeper into the pterygopalatine fossa.
- Ophthalmic CNV1
- Maxillary CNV2
- Mandibular CNV3
Where will the facial nerve CNVII emerge?
Facial nerve is going to emerge from the stylomastoid foramen and spread out across the superficial regions of the face and neck.
Where does the ophthalmic branch of the trigeminal nerve emerge?
Orbital fissure – the next structure laterally from the optic nerve. Called fissure, as in some species it is bigger. Ophthalmic nerve emerges here and spreads out across the forehead and innervate structures there, as mostly sensory. Goes from forehead, into skull.
Where does the maxillary branch of the trigeminal nerve emerge?
Maxillary branch passes through the round foramen. Provides sensory information to muscles of the rostrum and structures and teeth in the upper arcade. Round foramen is reached via the rostral alar canal and there is an opening caudally as well. So rostral alar is a little tube running rostrally to caudally and containing in it the round foramen. From here the maxillary nerve will travel across the pterygopalatine fossa and out of the infraorbital foramen. Here it gives off branches that are going to sensory innervate cheek teeth.
Where does the mandibular branch of the trigeminal nerve emerge?
Mandibular branch will exit via the oval foramen, the hole caudal to the caudal opening of the alar canal. Provides motor innervation to the muscles of mastication. Oval foramen will be linked to structures of the mandible by the mandibular branch of the trigeminal nerve.
Describe the additional path of the trigeminal nerve through the mandibular.
- Mandibular foramen to provide sensory innervation to lower arcade of teeth.
- Small cranial tunnel running through the mandible called the mental foramen.
What is the clinical relevance of the facial nerves and muscles?
- Several conditions can affect the muscles of facial expression and mastication
- Knowledge of the paths of the nerves that innervate them is important for localising where damage may have occurred
- Also used for regional anaesthetic
What are the groups of muscles innervated by the facial nerve CNVII?
- Muscles of the ear (also some innervation from elsewhere)
- Muscles of the eyelids
- Muscles of the nose, cheeks and lips
Describe the position and function of the frontalis muscle.
Muscle across the forehead. Muscles fibres contract to rase eyebrows.
Describe the position and function sphincter muscles in the face.
There are 2:
- Orbicularis oculi, which goes around the eye, is a circular/orbital muscle that can be used to close the eye.
- Orbicularis oris which goes around the mouth and allows closing and pursing of the lips.
Describe the function of levator nasolabalis.
In the horse, it is involved in lifting the nose and upper lip, so is an important structure for signalling movement in horses.
Which muscle is obvious in dissections?
Parotidoauricularis
Describe the position of the platysma muscle.
Big muscle that runs across the surface of the face. Runs up through the neck and across the whole surface.
Describe the positions and function of the buccinator muscle.
Accessory muscle of mastication across the cheek. It is a facial muscle that is muscle of facial expression innervated by the facial nerve. It controls the shape and how closed/open the check is.
What is the scutiform catilage?
Cartilage which sits at the base of the pinna and the base of the external ear and has group of muscles that attach to it.
Name the muscles that attach to the scutiform cartilage.
Rostroauricular muscles
Interscutularis
Caudioauricular muscles
What are 2 extra muscles in the equine face and their function?
Levator of the upper lip
Depressor of the lower lip
These are important for lifting and flaring the nostrils to make sure enough oxygen is getting in during high speed locomotion.
What is the clinical cause of an unsymmetrical face in the equine?
1 of the 2 facial nerves isn’t working well. On the side of the face where the nerve is working well, muscles are tensing and are able to move and the other side is floppy and not able to be contracted, so floppy side is always being pulled around towards the functional side. This is important for keeping food inside the mouth and when food is unable to stay inside the mouth, this is known as quidding. This is important for getting headcollars and bridles that fit in horses to avoid trauma or damage to nerves.
What are the branches of the facial nerve and what do they innervate?
Auriculopalpebral branch – muscles of the eyelids, ear and forehead. If there is damage to this branch, there is drooping of the ear, narrowing of the palpebral fissure and an inability to close the eye.
Dorsal buccal branch – muscles of the lips and cheeks
Ventral buccal branch – muscles of the lips and cheeks
Also caudal auricular and colli branches
What does buccal branch damage result in?
Results in paralysis of the lips and cheek muscles, allowing spillage of food in mastication and may lead to deformation of the muzzle.
Where does the facial nerve emerge?
Facial nerve exists the skull at the stylomastoid foramen.
What is TECA surgery?
Total Ear Canal Ablation
- Principle structures at risk: facial nerve, retroauricular vein, parotidoauricularis muscle and parotid salivary gland
- To get rid of recurrent inflamed tissues to restore ability to get sounds and airflow back through the external auditory meatus.
- TECA surgery does have risk factors of other structures around the ear.
Name the muscles of mastication and their innervation.
More deep and involve trigeminal nerve CNV:
Temporalis
Masseter
Pterygoids
Digastricus – also innervated by facial nerve
What are the branches of the trigeminal nerve?
Ophthalmic V1 – sensory to skin between eyes and forehead
Maxillary V2 – sensory to skin over muzzle and to upper teeth
Mandibular V3 – sensory to skin over mandible and cheek and lower teeth and motor to muscles of mastication
Describe the position and function of the temporalis muscle.
Temporalis muscle in the temporal fossa. Involves in biting down so tends to be larger in more carnivorous animals.
Describe the position and function of the masseter.
Masseter laterally on the mandible on the mesenteric fossa and heading to lateral side of the pterygopalatine fossa and medial side of zygomatic arch. Grinding and rolling lower jaw form side to side, so more associated with herbivorous mammals.
Describe the position and function of the digastricus.
Digastricus curves round the mandible. The only muscle of mastication that opens the mouth. It is smaller because mostly opening the mouth uses gravity and so digastricus used for when lying down or opening against a force.
Describe how the pterygoid and masseter muscles work as a functional pair.
There is ipsilateral contraction of masseter alongside contralateral pterygoid. Right masseter will activate left pterygoid and rolls jaw right, and vice versa.
Describe the size arrangements of muscles of mastication in the horse.
Smaller temporalis, as biting down is not a large part of horse mastication
Big masseters and pterygoids for rolling motion of the mandible as herbivores.
Which conditions can limited ability to open the mouth arise?
Masticatory muscle myositis – common idiopathic autoimmune inflammatory myopathy in dogs
Tetanus – trismus/lockjaw/muscle spasm. Reduced opening of jaws due to spasm of masticatory muscles.
What are 3 signs of trigeminal nerve myopathies?
Inflammation
Neoplasia
Trauma
What are the clinical signs of trigeminal nerve myopathies in each branch?
Ophthalmic branch – corneal anaesthesia, loss of sensation to upper eyelid and eye medial canthus
Maxillary branch – loss of sensation to eye lateral canthus, lower eyelid, face including nostril and palate upper teeth.
Mandibular branch – loss sensation to jaw line and lower teeth, unilateral or bilateral paralysis of masticatory muscles, leading to an inability to close the mouth, difficulty eating and drinking.
Give 4 regional nerve blocks in the head.
- Caudal maxillary block – infraorbital nerve V2
- Rostral maxillary block – infraorbital nerve V2
- Caudal mandibular block – inferior alveolar nerve V3
- Rostral mandibular block – inferior alveolar nerve V3 via mental foramen
How might nerve blocks be different in brachycephalic skulls?
Short canal gives both rostral and caudal maxillary block but both may need to be done on non-brachycephalics. Used for canine removal.
What are the functions of the neck?
- Holds the head up against the force of gravity
- Controlling head position
- Providing safe passage for information, nutrition and waste products between the head/and brain and body.
Describe what the nuchal ligament is and its function.
An elastic ligament. Correlation between the strength of the ligament and the weight of the head and length of lever arm of the neck.
Function is to support the head without interfering with the ability to lower the head.
Much more developed in larger animals. Absent in the cat.
Describe the organisation of muscles in the neck.
Dorsally – epaxial spinal muscles and muscles of the locomotor girdle
Ventrally – hypaxial spinal muscles and muscles of the locomotor girdle
Most ventral portion – strap muscles and viscera. Important for clinical access
Describe the action of spinal muscle contraction.
Paired spinal muscles can contract with different actions. Bilaterally or unilateral:
Bilateral contraction causes dorsal extension and ventral flexion
Unilateral contraction causes lateral flexion towards contracting muscle
What is the innervation of the trapezius and what does it allow the limb to do when fixed and free?
- Neck dorsal extension and lateral flexion (limb fixed).
- Dorsal and cranial translation of scapula on torso (limb free)
- Limb protraction (limb free)
Innervation: accessory nerve CNXI
What is the innervation of the omotransversarius and what does it allow the limb to do when fixed and free?
- Neck lateral flexion (limb fixed).
- Cranial translation of scapula on torso (limb free)
- Neck dorsal extension (limb fixed).
- Limb protraction (limb free)
Innervation: accessory nerve CNXI
What is the innervation of brachiocephalicus and what does it allow the limb to do when fixed and free?
- Lateral flexion of the neck (limb fixed).
- Cranial translation of brachium relative to torso (limb free)
- Limb protraction (limb free)
Innervation: accessory nerve CNXI with some contribution from cervical and axillary nerves.
Describe the position and function of the deep epaxial muscles.
- Deep epaxial muscles lie to the side and dorsal to the spine
- Splenius is an example of an epaxial muscle of the neck
- Extensors of the spine when acting bilaterally but lateral flexors when acting unilaterally
Describe the position and function of the deep hypaxial muscles.
- Ventral to the spine
- Flexors of the neck when bilaterally
- Later flexors when acting unilaterally
What is the innervation of the rhomboideus and what does it allow the limb to do when fixed and free?
- Neck dorsal extension and lateral flexion (limb fixed).
- Dorsal and cranial translation of scapula on torso (limb free)
- Limb protraction (limb free)
Innervation: dorsal branches of cervical and thoracic spinal nerve
What is the innervation of the serratus ventralis and what does it allow the limb to do when the limb is fixed and free?
- Dorsal translation of thorax relative to limb
- Raise thorax and support trunk.
- Unilaterally shift weight to contralateral limb
Innervation: long thoracic nerve
Name the 3 ventral neck muscles.
Sternohyoideus
Sternothyroideus
Sternocephalicus
All originate on the manubrium
Describe the ventral strap muscles.
Sternohyoideus and sternothyroideus are the ventral strap muscles.
They have theoretically very little action on the neck but complete the protective covering over the ventral viscera. Stabilise and move larynx and hyoid apparatus for swallowing, innervation is the C1/C2 spinal nerves.
Describe the position, function and innervation of the sternocephalicus.
- Origin: manubrium
- Insertion: mastoid process and occiput
- Neck ventral and lateral flexion
- Innervation: accessory nerve CNXI
Give the species variations of the sternocephalicus.
In the horse: mandibular insertion is the sternomandibularis
In the cow: sternooccipitalis and sternomandibularis portions
Describe the appropriate and inappropriate injection sites in cattle and sheep.
The neck is an important site for injecting production animals to avoid devaluing the carcass.
Inappropriate: shoulder, jugular furrow, spinal column, nuchal ligament
Appropriate: intramuscular and subcutaneous triangles of the lateral neck muscles*
What is the clinical significance of the lymphatic drainage of the head?
- Part of general clinical exam
- Indicator of regional problems, such as infection or neoplasia
- Indicator of systematic problems, such as neoplasia, spread of infection
- ‘Sentinels’
- Important in disease surveillance
Name the 3 lymphocentres of the head and which structures they drain.
Parotid – dorsal structures: skin, bones, orbit and some muscles of mastication
Mandibular (submandibular nodes palpable in canine) – muzzle, salivary glands, tongue, intermandibular space, muscles of mastication
Retropharyngeal – deep structures – pharynx, larynx and other nodes
Name the 2 lymphcentres in the neck and which structures they drain.
Prescapular centre – superficial cervical, palpable in canine. Cranial to shoulder joint, drains superficial neck, upper trunk and proximal forelimb.
Deep cervical centre – chain of nodes in the neck. Cranial, middle and caudal groups along the length of the trachea. Drain deep and ventral neck structures.
How do lymph nodes in the head and neck drain?
Drain via the tracheal ducts:
- Lymphatic vessels, one at each side of the trachea in the neck.
- Arise in retropharyngeal lymph node
- End in lymphatic duct on the right or thoracic duct on the left. May drain into the external jugulars at the thoracic inlet
Name the species differences in the palpable lymph nodes in the head and neck.
Dogs and cats = mandibular and prescapular
Horses = mandibular, parotid and retropharyngeal
Ruminants = mandibular, retropharyngeal and prescapular
How can bodily drainage be broadly linked to lymph nodes?
Mandibular – superficial lymphatic drainage coming across the surface of the head and cranial portion of the neck.
Prescapular – generally the neck
Axillary – forelimb and across the thorax
Popliteal – distally in the limb up to the mid thigh region
Inguinal – all around tail and abdominal and pelvic regions to central portions of the thorax
What is fine needle aspiration used for?
FNA is a biopsy procedure in which a thin needle is inserted into an area of abnormal-appearing tissue or body fluid. As with other types of biopsies, the sample collected in FNA can help make a diagnosis or rule out conditions such as cancer.
What may we be looking for using FNA?
Primary (lymphoma) or metastasised (mammary neoplasia) neoplasia
Caseous lymphadenitis – bacterial disease in sheep, goats and ruminants. Lymph node abscesses with fibrous capsules and may spread to the lungs.
Strangles – an infection of the retropharyngeal lymph nodes. Clinical signs: fever, purulent rhinitis, laryngitis, cough. May infect guttural pouch. If the retropharyngeal lymph nodes themselves are affected, pressure on pharynx from pus build up can cause difficulty breathing.
What the clinical considerations of vasculature of the head?
- Infection – guttural pouch mycosis (ICA)
- Auricular and palate surgery
- Pulse points
- Arterial and venous blood sampling
Name the 1st arteries that supply the head.
Common carotid artery – paired arteries coming up through the neck and then further branch.
Internal carotid artery – heads towards the brain and heads around the edge of the guttural pouch in the horse.
External carotid artery – this branches.
Cranial laryngeal arteries – 1st branch of the external carotid
Describe the arterial supply to the brain.
- Vertebral arteries
- Ventral spinal arteries
- Internal carotid artery in most mammals
- The vertebral and ventral spinal arteries join to form the Basilar artery, which contributes to the cerebral arterial circle /circle of willis
- Internal carotid artery also contributes in most mammals
Name the branches of the external carotid artery and what they supply.
Cranial laryngeal – to larynx
Ascending pharyngeal – to pharynx
Occipital – to the back of the skull
Caudal auricular – backwards behind the ear
Superficial temporal – across the superficial lateral side of the head. Has a branch of its own, the transverse facial artery.
What are the 3 larger branches of the external carotid artery?
Lingual – to the tongue
Facial – to the lateral side of the head and up towards the nose
Maxillary – to deeper structures through the pterygopalatine fossa and travels and mirrors the path of the maxillary branch of the trigeminal nerve.
Name the arteries that supply the face, nose and mouth.
- Lingual – the tongue, palatine tonsil
- Facial – lips, lateral nose, angle of the mouth
- Superficial temporal – eyelids, dorsum of nose, masseter
- Maxillary
Name the branches of the maxillary artery and what they supply.
- External ophthalmic – the orbit
- Inferior alveolar – lower alveoli, lower teeth, lower lip and chin
- Infraorbital – upper alveoli and upper teeth
- Ethmoidal – nasal cavity
- Major and minor palatine – hard and soft palates
What is the linguofacial trunk in the equine?
At the external carotid, instead of picking up a lingual and facial artery separately, there is a linguofacial trunk. Lingual and facial arteries than split from it. It is the facial artery that can be palpated as it passes around the ventral border of the mandible.
What is the guttural pouch of the equine?
An empty sphere shaped region on either side of the head, where lots of important structures pass through.
Big structure running through the middle is the stylohyoid bone. There are several different arteries and cranial nerve running through here.
What is guttural pouch mycosis?
Fungal infection that sets in within that guttural pouch and causes issues. A build-up of infectious agents can eat away at mucosal layer, causing different aspects of cranial nerves to be damages or eroded away. Can also end up with bleeds, particularly from the external carotid artery.
Describe the venous drainage of the head.
- Veins are mostly satellite to arteries
- Notable variations from this include the external jugular vein and linguofacial vein
- Generally drain from deep to superficial
- The venous plexus, pterygoid, ophthalmic and pharyngeal, drain some more superficially and can cause infections from around the eyes to track to deeper structures
Describe the 2 veins draining from superficial to deep in the equine.
- Important to track infections of the head.
- Major veins are superficial
- Muscular veins and is embedded by muscles of the face that keep blood flow moving around the head.
- Therefore, non-functional valves
Which veins of the head have venal sinuses?
Transverse vein, deep facial vein and buccal vein all have venal sinuses, which are swellings where blood will pool to give it somewhere to go which can occur when the animal has its head down.
Which veins can be palpated, taken samples of and used for venepuncture?
Facial artery easily palpated under the mandible of the horse
Can take arterial blood samples form lingual, facial and common carotid and venous samples from the transverse facial vein in the horse
Venepuncture in the jugular vein. This is particularly obvious in the cow – jugular vein sits between brachiocephalicus and sternocephalicus in a groove/furrow.
What bone forms the cribriform plate (through which the olfactory nerves pass)?
Ethmoidal
What bone forms the cribriform plate (through which the olfactory nerves pass)?
Ethmoidal
Which bones contain sinuses?
Frontal and maxillary
Many of the foramina in the equine skull have merged, why is this?
Bone develops around nerves and blood vessels in the embryo. These structures are large in the equine so no bone develops between them leaving one large foramen.
Describe the equine paranasal sinuses.
The maxillary sinus is divided into rostral and caudal parts with a dividing wall between them. The frontal sinus communicates with the caudal maxillary sinus. The rostral maxillary sins invades the ventral conchae. Tooth sockets are found in the ventral part of the maxillary sinus wall.
The articular surface of the mandible articulates with the articular surface of which bone?
Temporal bone
List the bony prominences of the skull.
External occipital protuberance
Nuchal crest
Left and right occipital condyles
External sagittal crest
Hamulus of pterygoid
Tympanic bullae
Mastoid process
Retro-articular process
Jugular process
What occupies each bony hollow?
Mandibular fossa of temporal bone = Mandibular condyle
Pterygopalatine fossa = Pterygoid muscles
Temporal fossa = Temporal muscle
Lacrimal fossa = Lacrimal sac
List the bony passages of the skull.
- Orbital fissure
- Round foramen and rostral alar canal
- Maxillary foramen
- Infraorbital foramen
- Oval foramen
- Stylomastoid foramen
- External auditory meatus
- Optic canal
- Tympano-occipital fissure (horse): Jugular foramen, Foramen lacerum, Carotid canal
- Major and minor palatine foraminae
- Hypoglossal foramen
- Foramen magnum
What branch of what cranial nerve is associated with the mandibular and mental foraminae?
Inferior alveolar branch of the mandibular division of trigeminal, and mental nerves
What part of the skull does C1 articulate with?
Occipital condyles
Locate the tympano-occipital fissure (the fusion of all the holes around the tympanic bulla). Why is there no separate carotid or other foraminae around the bulla?
Because the holes are bigger around the bulla (and everywhere on the skull) to accommodate larger nerves or vessels, so the holes fuse together to make a large fissure.
Is there a parietal bone in the ox skull?
Yes, this is pushed onto the caudal aspect of the skull as the frontal bone is so large
Does the equine TMJ allow more or less lateral motion? How so?
More lateral motion than in carnivore. The shape of condyle surface is flattened / less of a cylinder (whereas that of carnivore is cylindrical so allows hinge action only).
In the horse, describe where it would be safe and most sensible to trephine to allow drainage of the sinuses.
Maxillary sinus – dorsal to facial crest/ridge, caudal to facial tubercle, rostral to medial corner of orbit, and ventral to line of nasolacrimal duct.
Note the thinness of the alveolar bone and hence the relationship of cheek teeth to sinus. What are the clinical implications of this?
There is a danger of tooth infections eroding the alveolar bone to infect the sinuses. Additionally, the wall of the sinuses can be punctured e.g. by a blow to the side of the head, to infect the sinus. Also, sinus infections may erode the bone and affect the teeth.
What are the consequences of this invasion of the horn when you want to remove a horn?
Removal of the horns in adult cow may result in the sinuses being opened- this would increase the risk of haemorrhage and infection. The sinus mucosa is innervated by sensory nerves which cannot be blocked; hence horn removal, even if the cornual nerve is blocked, is inevitably painful.
What is the bony process called that supports the horn?
Cornual process. This is present even on breeds with no horns, but to a lesser size.
In order to desensitise the upper arcade of teeth which foramen of the skull is commonly targeted with local anaesthetic?
Infraorbital foramen
What type of joint is the mandibular symphysis in the cat?
Cartilaginous
What veins of the horse’s head contain venous sinuses?
Transverse facial vein
Deep facial vein
Buccal vein
Which muscle receives innervation from both CNVII and CNV?
Digastricus
What branch of what nerve provides sensory innervation to the upper canine teeth?
Maxillary branch of the trigeminal nerve
In order to desensitise the upper arcade of teeth, which foramen of the skull is commonly targeted with local anaesthetic?
Infraorbital foramen
