Special senses - eye adnexa Flashcards
What structure is at the medial canthus of the eye?
Lacrimal caruncle
What does the lacrimal caruncle do?
Secretes oils from sebaceous glands to help distribute tears
What completes the orbit?
Orbital ligament
What animals need an orbital ligament?
Dog, pig, cat
Where is the orbit osseus in domestic animals?
Dorsal and medial
What structure can form the floor of the orbit in some species?
Zygomatic salivary gland
What is the zygomatic salivary gland called in large animals?
Dorsal buccal salivary gland
What can trauma to the zygomatic salivary gland cause?
Zygomatic mucoseal - connective tissue capsule filled with saliva
What are the 3 layers of orbital fascia?
Periorbita
Superficial muscular fascia
Deep muscular fascia
What is the periorbita?
Most superficial layer of dense fascia
Makes up lateral and ventral orbit
Where does the periorbita attach?
Optic foramen
How and where does the periorbita associate with the bony orbit?
Blends with the periosteum at the orbital margin
What is embedded in the dorsomedial wall of the periorbita?
Trochlear cartilage
What is the function of the trochlear cartilage?
Transmits the tendons of the dorsal oblique muscle
Alters the attachment of it onto the eye by 90 degrees
Where do the eyelids originate from embryonically?
Surface ectoderm
What is the word for fused eyelids at birth?
Physiological ankyloblepharon
What are the ligaments that attach either side of the eyelid called?
Palpebral ligament
Which palpebral ligament is more well defined?
Medial
Where do the palpebral ligaments originate from?
The periosteum
What feature of the eyelid is only found in horses?
Lacrimal tubercle - rod like process on the bone
What does the lacrimal tubercle do?
Elongates the palpebral fissure when the eye is closed to stabilise it
What is eye removal called?
Enucleation
What do you need to cut in order to remove the eye?
Medial palpebral ligament
Where is the superficial muscular fascia found?
Wrapped around the extraoccular muscles
Where is the deep muscular fascia found?
Deeper in the cone, more associated with the rectal muscles
What are the 3 layers of the eyelid?
Skin
Musculofibrous
Palpebral conjunctiva
What are the two different types of conjunctiva?
Palpebral and bulbar
Where is the bulbar conjunctiva found?
On the occular surface
Where is the palpebral conjunctiva found?
Inner surface of eyelid, reflects off occular surface
What is the join between the two types of conjunctiva called?
Fornix
What is the space that is between the two types of conjunctiva called?
Conjunctival sac
What main muscle is found in the musculofibrous layer?
Orbicularis oculi
What are the two parts of the orbicularis oculi muscle?
Orbital - around outside of eye
Palpebral - eyelid
What is the join between the orbital and palpebral parts of the orbicularis muscle called?
Orbital septum
What muscle elevates the upper eyelid/third eyelid?
Aponeurosis of levator palpebrae superioris
What neurological condition is associated with the levator palpebrae superioris? Why?
Horner’s syndrome
Under sympathetic control
Where is the aponeurosis of levator palpebrae superioris found?
In the musculofibrous layer of the eyelid
What does the levator palpebrae superioris attach to?
The tarsal plate/muscles in the eyelid
What deep glands are on the inner surface of the eyelid?
Meibomian glands
What is the alternate name for the third eyelid?
Nictitating membrane
What makes up the third eyelid?
Fold of conjunctiva and T shaped piece of cartilage
What controls the third eyelid?
Sympathetic control - involuntary
What are the 4 main symptoms of Horner’s syndrome?
Sunken eye
Protruding third eyelid
Constricted pupil
Droopy upper eyelid
What do the smooth muscles in the periorbita layer oppose?
Retractor bulbi
Where is the lacrimal gland located?
Dorsal to the lateral canthus
Where are tears secreted?
Through ducts from the lacrimal gland into the dorsal fornix of the conjunctival sac
What do tears initially drain into?
Punctum
Where do tears drain from the punctum?
Through canaliculi to the lacrimal sac
Where does the lacrimal sac drain to?
Through the lacrimal duct to the ventral nasal meatus
Where do the extrinsic muscles of the eye insert on?
The sclera of the globe
Where do the extrinsic muscles of the eye originate from?
Near the optic foramen behind the eye
Except ventral oblique - ventromedial wall of orbit
What are all the extrinsic muscles of the eye?
4 rectus
2 oblique
1 retractor bulbi
What are the rectus muscles innervated by?
Oculomotor nerve
Except lateral rectus - abducent nerve
What is the dorsal oblique innervated by?
Trochlear nerve
What is the role of the retractor bulbi?
Protection of the eye by pulling it back
What is the retractor bulbi innervated by?
Partly oculomotor, partly abducent
What muscles move the eye around the dorsoventral axis?
Medial and lateral rectus
What muscles move the eye around the mediolateral axis?
Dorsal and ventral rectus
What muscles move the eye around the anterior-posterior axis?
Dorsal and ventral oblique
What is the main blood vessel supplying the adnexal structures? What is it a branch of?
External opthalmic artery - branch of maxillary
What branch of the external opthalmic artery supplies the eyelids?
Palpebral artery
What branch of the external opthalmic artery supplies the extraoccular muscles?
Muscular branches
What branch of the external opthalmic artery supplies the dorsum of the eye?
Supraorbital artery
What artery supplies the globe?
Internal opthalmic artery
