L4. Orbit Flashcards
Which bones more likely to be damaged in a punch to the orbit
Floor of orbit as the orbit is a cone and force coming directly they go from high to low and push some of the orbital cavity contents into the maxillary sinus
What are the tissue layers of the eyelid (from anterior to posterior)
- Skin
- Subcutaneous tissue/ fascia: potential space
- Voluntary muscle: Orbicularis oculi muscle
- Orbital septum
- Tarsus
- Conjunctiva
Describe the structure function and innervation of the Obucularis oculi
What is one significant pathology
S: Two parts:
- Palpebral (eyelid)
- Orbital (surrounding).
F: Squeeze shuts eyelids to distribute humidity over the eyeball.
N: Facial nerve CN7
Losing this nerve: no tight shutting, lower lid droops leading to spilling tears. Eye get dry, damage cornea.
Describe the structure, function of the Orbital septum
What is one significant pathology
S: Extension in the bottom (attach to tarsus) and top lid (attach to LPS tendon) of the periosteal layer which covers inside and outside of the orbit.
F: It is a seal/protection for the cavity from bacterial/viral infection.
P: If fracture over the bone that damages periosteum, the blood will go to the sup fascia causing:
Raccoon eye: eyeball is healthy but accumulation of fluid/blood in the eyelid
Describe the structure, function and relationship of the Tarsus and the 2 muscles that open the eye lids (innervation)
What is one significant pathology of both
Tarsus: Plates of dense CT Sup and Inf (for each eyelid)
F: First defence against sharp object going to the eye.
- Levator Palpabrae Superioris muscle: attaches to ant surface of sup tarsus.
In: CN3. Damage: full ptosis
- Sup tarsal muscle: attaches upper edge of sup tarsus.
In: Post. ganglionic symp fibres from Sup. Cervical ganglion.
Partial ptosis from damage.
Describe the structure, function of the Tarsal gland
What is one significant pathology + treatment
S: In tarsal plates, empyting onto the free margin of each eyelid
F: Secretes oily substance to reduce evaporation of tear film/increase viscosity.
P: If duct is blocked the gland, inner surface of eyelid swells inflammation: Chalazion
Treated by local antibiotics, hot towel to help the gland draining
Describe the structure, function of the other glands of the eyelid
What is one significant pathology
Associated with eyelash follicles on base of eyelids are sebaceous and sweat glands
Blockage and inflammation of these causes stye: on edge of eyelid
Describe the structure, function of the Conjunctiva
S: Thin membrane covering posterior surface each eyelid before reflecting ono the sclera of eyeball. Attachment at cornea/sclera junct.
Forms the conjunctival sac when lids closed: made of sup and inf conjunctival fornices
F: 2nd defence layer that protects the eyeball from smaller foreign bodies.
What is the arterial supply and sensory + motor innervation to the eyelid
A:
Branches of the Ophthalmic artery, (sup) facial artery (med) and superficial temporal artery (lat)
Sensory: CN V1 (sup) and V2 (inf)
Motor: CN III for LPS,
CN VII: orb. oculi,
Sympathetic fibres: Sup Tarsal
What is the innervation of the 7 Extrinsic muscles of the eye
Lateral rectus: CN6 (abducens)
Superior oblique: CN4 (trochlear)
Sup, Inf, Med rectus
Inf oblique
Levator palpabrae superioris:
CN3 (Occulomotor)
What is the 4 other names for the Periosteal layer that lines the outside of the skull
1) Periorbita: lining the orbit.
2) Orbital septa are an extension of this
3) Periorbita becomes continuous with periosteal layer of dura mater lining inner cranial cavity.
4) Thickened periorbita around the optic canal and central part of sup. orbital fissure = Common tendinous ring.
What muscles originate from, what nerves + vessels pass through the Common tendinous ring:
1) 4 rectus muscles - (extraocular)
2) Optic canal: Optic nerve, Opthalamic artery
3) Sup. Orbital fissure: Sup +Inf branch of occulomotor nerve (CN3), Abducent (CN6) Nasocilliary branch of V1
If inflammation of the ring then there can be pressure on these vessels.
Describe the path of action of the Lacrimal apparatus: starting at the Lacrimal gland on the lateral free edge of LPS
- Lacrimal gland ducts empty secretions into the lateral part of sup. fornix of conjunctiva
- Fluid moves lat to med with blinking. Accumulate as lacrimal lake on the medial aspect
- Drains into Lacrimal caniculi via lacrimal punctum (pump)
- Joins the Lacrimal sac (med)
- Continues to drain in the Nasolacrimal duct which terminates into the nasal cavity.
What is Dacryocystole
Congenital disorder where the lacrimal sac is blocked leading to discharge out of the eyes- backing up of the lacrimal apparatus
What is the arterial and venous drainage of the eyeball
A: Central retinal artery (branch of opthalamic) which goes to the retina.
V: Superior and inferior opthalamic vein. It communicates between the inside and the outside of the skull, can drain bacterial back into the brain
