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30 Cards in this Set
- Front
- Back
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define: orbit
What is its function? |
conical cavity enclosing the eye (globe) and ocular adnexa
function: protection & support |
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define: adnexa
what are the components of the ocular adnexa |
the accessory parts adjoining an organ. It's the periocular structures:
1. eyelids 2. conjunctiva 3. lacrimal gland 4. nasolacrimal system 5. third eyelid |
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what is the variation in the orbit among the following species:
1. human 2. horse, cattle, sheep, pig 3. dog and cat |
1. orbital borders are ENTIRELY bony 2. orbital rim entirely bony 3. orbital rim bony except caudolateral 1/5 (orbital ligament) -in dogs and cats... medial wall & part of orbital roof are bony; lateral wall and floor are soft tissue--temporalis m., masseter m., pterygoid m, & zygomatic salivary gland) |
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why is the variation in orbit morphology clinically significant? |
the difference in morphology will help us determine how specific disease processes affect the globe.
i.e. the lateral wall and floor of orbit in dogs and cats comprise of chewing muscles, thus dz process in these muscles can affect the globe (thus, abnormalities with globe may be not even be due to issues directly from the eye) |
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define: orbital ligament
what are its functions?
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orbital ligament is well-defined fibrous band at the caudolateral aspect of the orbit rim
function: 1. links zygomatic process of frontal bone w/ frontal process of zygomatic bone 2. it attaches orbicularis oculi m. and lateral palpebral ligament |
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what are the orbital margins in domestic animals? |
1. dorsomedial margin: frontal bone
2. ventromedial margin: lacrimal bone (some brachycephalics--maxillary bone)
3. ventrolateral margine: zygomatic bone 4. dorslateral margin: orbital ligament
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what are the orbital borders in domestic animals? |
1. medial wall and part of orbital roof are BONY -orbital portion of frontal bone -orbital wing of sphenoid bone -lacrimal bone 2. lateral wall and floor are SOFT TISSUE -temporalis m, masseter m, pterygoid m, zygomatic salivary gland |
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what is the significance of the incomplete bony orbit in the dog? |
the soft tissue floor of the orbit is a portal for penetration into orbit from oral cavity by:
-orbital foreign body -retrorbital abscess -orbital cellulitis |
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what's the difference between exophthalmos and proptosis? |
while both involve the globe being displaced, exophthalmos involves the globe still being in the orbit unlike proptosis |
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why does the mass position in the orbit matter? |
it affects the position of the displaced globe |
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in addition to mass locations in the orbit, what other abnormality locations affect position of the globe? |
abnormalities in the maxillary and frontal sinuses like neoplasia, fungal infections, and inflammation |
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what is typically the cause of proptosis? |
disruption of EOMs |
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what are the 5 foramina found in the medial orbital wall? What nerves/vessels pass through these foramina? |
1. optic canal : CN 2 & internal ophthalmic artery 2. orbital fissue: CNs 3, 4, 5 (ophthalmic), 6, external ophthalmic artery, ophthalmic venous plexus 3. rostral alar foramen: CN 5 (maxillary) 4. caudal alar foramen 5. oval foramen: CN 5 (mandibular) |
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what are the components of the orbital fasciae? |
1. vagina bulbi 2. muscular fasciae 3. periorbita |
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what is vagina bulbi? |
originating from the limbus, it's the bulbar sheath or "tenon capsule" that envelopes the globe (from limbus to optic nerve & continues posteriorly w/ dura mater of optic nerve)
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what is the periorbita? |
it's a conical fibrous sheet that surrounds eye and associated muscles, nerves, and vessels
it contains circular smooth muscle fibers causing tone to keep globe prominent w/in orbit (sympathetically innervated) |
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what would denervation of the periorbita cause? |
enophthalmos (think of horner's syndrome) |
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What's the function of the eyelids (palpebrae)? |
protect the eye via: -shade -tear distribution -cleaning |
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what are the external components of the eyelid?
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1. palpebral fissure: opening b/w upper and lower eyelid
2. canthus: junction of eyelids--lateral and medial
3. lacrimal caruncle: soft tissue prominence @ medial canthus, may contain fine hairs |
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what are the internal components of the eyelid? (the fibromuscular layer)
What CNs innervate these muscles? |
1. orbicularis oculi: muscle that encircles the opening of the eyelids and closes the eyelids when it contracts (CN ???)
2. levator palpebrae superioris: muscle which "opens" eyelids (enlarges fissure) (CN 3)
3. tarsal glands (meibomian glands): sebaceous glands that open onto eyelid margin. secretes a lipid substance that contributes to precorneal tear film (CN ???) |
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discuss some diseases of eyelids "palpebrae"? (specifically tarsal glands) |
1. distichia: double row of lashes caused by production of hairs by tarsal glands
2. ectopic cilia: hair growing through eyelid conjunctive caused by production of hairs by tarsal glands |
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what is the conjunctiva and what are its components? |
conjunctiva: specialized mobile mucus membrane
components: 1. palpebral conjunctiva: lining eyelids 2. bulbar conjunctiva: on surface of globe, ends at limbus 3. conjunctival fornix: point of reflection (u-turn) 4. conjunctival sac: space b/w the palpebral and bulbar conjunctiva (gutter) 5. goblet cells: richly vascularized cells that contribute to mucin layer of tears |
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what is the 3rd eyelid?
what type of tissue is it supported by? |
it's the mobile fold in the ventromedial region of conjunctiva b/w ventral eyelid and globe
3rd eyelid is supported by a t-shaped piece of hyaline cartilage, in which the stem is surrounded by the superficial gland of the 3rd eyelid |
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where does the superficial gland of the 3rd eyelid secrete into? |
seromucous secretion enters via microscopic ducts onto bulbar surface of the 3rd eyelid into the lower conjunctival fornix |
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why don't you want to remove a prolapsed 3rd eyelid? |
you don't want to remove it because it contributes significantly to precorneal tear film; thus removing it would cause dry eye |
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discuss some of the third eyelid diseases discussed in lecture |
1. prolapsed TEL 2. everted ("scrolled") cartilage of TEL 3. neoplasia of the superficial gland of the TEL 4. trauma to superficial gland of the TEL |
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where is the lacrimal gland located?
what is its function?
what nerve(s) innervate it? |
it's deep to periorbita, on the superiolateral aspect of the globe.
It's between the globe and orbital ligament and zygomatic process of frontal bone
function: empties seromucous secretion into dorsolateral conjunctival fornix via microscopic ducts
innervated by: lacrimal nerve (branch of ophthalmic nerve) |
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what structures contribute to precorneal tear film production?
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1. superficial: -oily -eyelid (tarsal or meibomian glands)
2. middle: -aqueous -orbit and TEL (lacrimal gland & superficial gland of TEL)
3. deep: -mucous -conjunctiva (goblet cells) |
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what are the components of the nasolacrimal duct system (from start to end)?
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1. lacrimal puncta (2) 2. lacrimal canaliculi (2) 3. lacrimal sac (1) 4. nasolacrimal duct (1) |
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what are the IOM of the eye? what are they innervated by?
What are the EOM of the eye? what are they innervated by? |
IOM (all smooth muscles) 1. dilator m. of iris 2. sphincter m. of iris 3. ciliary m.
IOM innervation: EOM (all skeletal muscles) 1. rectus mm (dorsal, ventral, medial, lateral) 2. olique mm (dorsal, ventral) 3. retractor bulbi
EOM innervation: 3[LRRB6, DO4]
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