Definitions and anatomical terms Flashcards
Most carnivores have an open orbital rim true or false?
True. Most herbivores have a closed rim
What is the general name for the soft tissue structures which extend from the periosteum of the orbital rim to the sub-conjunctival tissues of the eye?
Periorbita. Important landmark in enucleation surgery
What ligament is this describing? A true, wide, very short ligament that adheres the medial canthus to the orbital rim medially
Medial canthal ligament
What ligament is this describing? Not a true ligament, more of a long tendinous connective tissue band
Lateral canthal ligament
What is the proper name for eyelashes?
Cilia
Do dogs, cats and horses have lower lashes?
No
Do cats have eyelashes?
Not true eyelashes, they have hairs which resemble lashes
What is the word for the long sensitive hairs connected to sensitive touch receptors around the eyes. Particularly obvious in horses
Vibrissae
What is the other word for meibomian glands?
Tarsal glands
What is a chalazion?
When the meibomian gland becomes impacted and bursts leading to granuloma formation around it
Which part of the tear film do the meibomian glands produce?
Meibomium-the oily part
What is an internal Hordeolum?
When the meibomian gland becomes infected leading to an internal stye
What causes an external hordeolum?
When the glands of zeiss and moll become infected (aka external stye). Glands of zeiss and moll are associated with the cilia
The tarsal plate and meibomian glands run along the top AND bottom eyelids. True or false
True
Where does the conjunctiva fuse with the eye?
At the limbus
Where is the ventral fornix?
Between the third eyelid and the globe
What is the Obicularis Oculi muscle and what is its function?
Strong muscle around the eyelids for eyelid closure
What and where is the Levator Palpebral Superioris muscle?
Lifts the upper eyelid
What is the muller’s muscle?
Supportive muscle that helps maintain the upper eyelid
What does the nasolacrimal system consist of?
Puncta (singular punctum), canaliculi, lacrimal sac, nasolacrimal duct (interosseus part), nasal punctum
What are the three parts of the third eyelid?
Leading edge, gland of the third eyelid, cartilagenous core
What percentage of the tears is made by the lacrimal gland?
70%
What are the four parts of the conjunctiva?
Palpebral
of the Third Eyelid
Bulbar
Conjunctival fonixes
What pattern do the conjunctival blood vessels have?
Dichotomous brainching
What pattern do the scleral blood vessels have
Meandering but no braching
What are the three components of the tear film from out to in?
Lipid layer-secreted by the meibomian glands, prevents evaporation
Aqueous part: most abundant, mainly water with many solutins including immunoglobulins and lactoferrin
Mucous part: Secreted by the corneal epithelial cells and the goblet cells of the conjunctiva
What are the four layers of the cornea?
Epithelium
Stroma
Descemet’s membrane
Endothelium
Which layer of the cornea is being described?
A few cells thick, basal cells are shed as squamous cells in a one week cycle. Basal cels at limbus serve as stem cells to produce other basal cells. Superficial ulcer develops if this layer is missing.
Epithelium
Which layer of the cornea is being described?
Made of collagen which is laid down in a particular arrangement to allow light to travel through, has several layers of these fibres, like an onion. Each layer is called a lamella. Relative state of dehydration & GAGs help to keep fibre arrangement
Stroma
Which layer of the cornea is being described?
During progressive ulceration of the cornea this layer is exposed forming a ****** which is a surgical emergency
Descemet’s membrane
****** = descemetocele
Which layer of the cornea is being described?
Only one cell thick, keeps the cornea dehydrated by Na-K-ATPase pumps that take away fluid that filters through from the aqueous humour. No regenerative capabilities
Endothelium
What is being desribed?
White fibrous tunic, covered by subconjunctival connevtive tissue (episclera) and conjunctiva. Very thin around the equator and near the optic disc. Has several holes to allow nerves and BVs to enter and exit
Sclera
What is the lamina cribrosa?
Part of sclera through which axons of ganglion cells exit the eye to form the optic nerve
What are the three groups of extra ocular muscles?
Recti-Lateral medial dorsal ventral
Oblique-dorsal and ventral
Retractor bulbi
Where is the aqueous humour prodcued and where does it leave via?
Produced in the ciliary body, leaves via the iridocorneal angle (schlemm’s canal)
What are the 2 muscle groups of the iris and which is stronger?
Constrictor and dilator. Dilator is stronger.
What are the three zones of the iris?
Pupillary zone
Iris colarette (middle)
Cilliary zone
What are persistent pupillary membranes?
Fetal vasculature remnants arising from the iris colarette, may stay in iris or reach cornea or lens causing opacity
Why do you get synschiae?
Inflammation of the uvea (uveitis)
What happens in a) anterior synechia b) posterior synechia
a) iris adheres to cornea
b) iris adheres to lens
What has to happen in order for you to get anterior synechia?
Sudden loss of aqueous humour e.g. in corneal perforation
What does the ciliary body need carbonic anhydrase enzyme for?
producing the aqueous humour
What does the musculature of the ciliary body do?
Focuses the lens
What is the posterior uvea and what does it do?
The choroid. Part of which is the tapetum. Also feeds the outer retina (mainly photoreceptors)
What are “stars of winslow”
In horses - appear all over tapetal fundus, they are end on choroidal capillaries, gives a subtle pin prick appearance
What is uveoscleral outfow and which species does this play an important role in?
The uvea and the sclera absorb some of the aqueous humour. Important in horses
aka the unconventional or accessory outflow route
What are zonules?
Arrise from ciliary body and attach anteriorly and posteriorly to the lens
What produces the lens fibres?
Lens epithelial cells
What are suture lines in the context of the lens?
confluence of the lens fibres. form a Y shape in anterior lens and upside down Y in posterior lens (dogs and cats)
What is the lens cortex?
The youngest part of the lens (produced by epithelial cells). Fibers loose cell nuclei and form part of the nucleus, becomes more and more compacted with age and a bit harder and bluish = nuclear sclerosis
What are the main layers of the retina?
1 epithelial layer: outer most, nurses photoreceptors
9 neural layers containing photoreceptors (rods and cones). Inner most neural layers contain ganglion cells and neural fiber layers which are an accumulation of axons which ultimately form optic nerve
Retinal vasculature: Contains paired venules and arterioles in dogs and cats (dorsal, lateral and medial). Horses have much less obvious retinal vasculature
Which species has myelin in the optic nerve head?
Dogs have fluffy myelin, makes disc look diamond shape sometimes. Cats don’t hence looks round
How does the optic disc of horses vary from that of dogs and cats?
Oval shaped, salmon colour and larger
At what point does the optic nerve become the optic tract?
After the chiasm
What is the obicularis oculi muscle innervated by?
Facial nerve (CN VIII)
What is the mullers muscle innervated by?
Sympathetic innervation hence we get ptosis in horner’s syndrome
what is the neural path once light has reached the retina?
Rods and cones
inner retina
ganglion cells
nerve fibre layer
optic disc (axons go through lamina cribrosa of sclera)
optic nerve (l & r)
optic chiasm
optic tract (l & r)
(branches for pupilary light reflex)
lateral geniculate nucleus
optic radiation
Visual cortex
what is the path of the PLR from the optic tract?
Pretectal nucleus (part of E-W nucleus anteriomedian nucleus), parasymp fibres of oculomotor nerve (CN III) with ciliary ganglion to pupillary musculature
What are the cranial nerves?
1-Olfactory
2-Optic
3-Occulomotor
4-Trochlear
5-Trigeminal
6-Abducens
7-Facial
8-Vestibulocochlear
9-Glossopharyngeal
10-Vagus
11-Accessory
12-Hypoglossal
Which ones are sensory/motor/both?
ssmmbmbsbbmm
some say money matters but my brother says big boobs matter more
Which nerve is used for vision?
2) optic nerve
which rectus muscle isn’t innervated by cranial nerve 3? What is it innervated by?
Lateral rectus. innervated by abducens (6)
What is a) the ventral oblique and b) the dorsal oblique innervated by
a) ventral oblique=occulomotor
b) dorsal oblique=trochlear
Which nerve is sensory to the eye?
V - the trigeminal nerve (opthalmic branch)
Which nerve controls blinking?
VII - The Facial Nerve
Which nerve is used for conjugated eye movements and eye movement in response to sound?
VIII - Vestibulocochlear
What controls the secretions of the lacrimal glands?
Mostly Parasympathetic. Fibres travel with facial nerve (VII) but change to travel with trigeminal (V) after the pterygopallatine fossa
What do the following terms mean:
OS
OD
OU
Left eye (occula sinister)
Right eye (occula dexter)
Both eyes
What is an ERG?
Electroretinogram, measures retinal responses to light stimuli
What happens if the pituitary becomes so large that it obliterates the gland? (dog)
Hypopituitarism (reported as diabetes insipidus)
In which species does a pituitary adenoma tend to get large and compress the pars nervosa and thalamus?
Horses
What is the appearance of pituitary adenomas in horses?
multinodular, yellow/brown/white and quite firm
Which species are most commonly affected by pituitary adenoma
Mostly horses, dogs but less than horses
Older animals
What syndrome results from active pituitary adenoma?
Cushings (hyperadrenocorticism due to ACTH release)
Where is ACTH produced in the horse?
pars distalis
Where do you find ACTH secreting adenomas in the dog?
pars distalis or pars intermedia
What does a pituitary adenoma look like on microscopy?
nests or groups of chromophobe cells, fine connective tissue stroma, no secreory granules seen on light miscroscopy
What are the four main metabolic/systemic changes in ACTH secreting adenoma in dogs?
Gluconeogenesis
Lipolysis
Protein catabolism
Anti-inflammatory actions
What are the clinical changes associated with pituitary adenoma in dogs?
Gradual enlargement of abdomen
Muscle wasting (head and legs and enlarged liver)
Bilateral alopecia, thin skin with mineralisation, hyperpigmentation
thick pads of fat around neck and shoulders
Poor wound healing
What is the more common name for the pars nervosa
posterior pituitary
What are the two main hormones secreted by the posterior pituitary
Oxytocin Vasopressin
Hormones in the posterior pituitary are synthesised by nerve cells that have their bodies in the hypothalamus. What nuclei in the hypothalamus?
Suproaoptic and paraventricular
What is the most common reason for euthanasia in horses with PPID?
Laminitis
What is the definition of EMS?
Cluster of clinnical/metabolic abnormalities associated with an increased risk of laminitis
Are all horses with EMS obese?
No. May be obese but not necessarily
What are the key features of EMS?
Insulin dysfunction
Increased fasting triglyceride concentration
Altered adipokine concentrations
+/- obesity
What is the pathogenesis of EMS leading to laminitis?
Increased Water Soluble Carbohydrates (eg from grazing grass)
Pronounced insulinaemic response (more so than normal)
High levels of insulin induces laminitis by affecting endothelial cells of blood vessels in feet
Also carbohydrate overload in the hindgut –> inflammatory mediators released –> injury to lamellae
Is EMS entirely environmental?
No, environmental risk and environment risk
What is the signalment for EMS?
Develops <15
pos genetic link
Ponies, morgans and arabs over represented
Where might the EMS horses have regional adiposity?
Crest, Tailhead, Prepuce and mammary region
NB there is a lean phenotype, don’t have to be fat
What is the main history sign associated with EMS?
Recurrent laminitis with no obvious cause
How do you decide if these EMS potential cases have insulin dysfunction?
Resting glucose and insulin concentrations, fast for 6 hrs sample in morning
What is a combined glucose-insulin test?
Fast for 6 hours
Insert jugular catheter
Infuse dextrose over 1 min
Immediately follow by insulin
Collect blood at 0,1,5,25,35,45,60,75,90,105,120,135 and 150
IR= blood glucose over baseline AND insulin >100 at 45 mins
What sort of diet should you give fat EMS ponies?
Limit soluble carbohydrate intake
feed only hay
feed 1.5% of body weight
Can soak hay to make it more rubbish
Add vitamin and mineral supplement if soaking hay
Can add beet pulp if owner insists needs dinner!
Why is it good to exercise EMS ponies even if they’re not overweight?
Promotes glucose uptake and use by skeletal muscle
Improves insulin sensitivity
Reduces inflammation if results in weight loss as pro inflammatory cytokines play a role in this
Decreases feed intake
What is metformin and is it useful in horses?
Improves insulin sensitivity in humans, not really in horses, only 7% absorption! Seems to reduce GI glucose absorption though possibly
Why do we use thyroxine in some EMS horses?
Increases metabolic rate resulting in weight loss
Prohibitively expensive in the UK as have to use dog and cat stuff
Insulin sensitising supplements have no evidence!
:)
