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62 Cards in this Set
- Front
- Back
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Optic Nerve
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* Carries information in the form of electrical energy, light energy called PHOTONS
* formed by axons of ganglion cells |
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Retina
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* Specialized cells (photoreceptors, rods and cones) are activated by light
* "message" transferred to retinal ganglion cells * axons of ganglion cells form optic nerve |
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Choroid
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* an extensive network of blood vessels surrounding retina
* provides the nutrients necessary for the retina to function |
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Sclera
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* composed of connective tissue (impermeable to light)
* provides a framework for attachment of the choroid and retina |
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Cornea
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* specialized type of connective tissue that is transparent ( therefore permeable to light)
* because it is transparent, it is void of blood vessels |
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Iris
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* regulates amount of light that gets into eye
* acts as a diaphragm * think spring: -coils: makes pupil large -stretches: makes pupil small |
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Mydriasis vs. Miosis
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Mydriasis: dilated pupil
Miosis: constricted pupil |
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Lens
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* helps refract the light rays so they will focus on the retina
* flexible so power can change to properly refract light rays at different distances |
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Ciliary Body
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* muscular tissue that attaches to the lens and controls its shape
* muscle is relaxed for distant vision * muscle is contracted for near vision -accommodation: lens power is increased to allow the focus of near objects on the retina * ciliary body's blood vessels produce the aqueous humor |
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Uvea
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iris + ciliary body + choroid
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Vitreal Chamber
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* filled with vitreous (a gel-like substance)
* offers structure and nutrients |
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Anterior and Posterior Chambers
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* filled with aqueous, a liquid substance
* offers nutrition for both cornea and lens * normal aqueous flow: from posterior chamber to anterior chamber via the anterior chamber angle then through Schlemm's canal and the aqueous vein |
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Extraocular Muscles
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* six extraocular muscles coordinate eye movement to ensure that each eye is looking at the same object
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Ocular Adnexa
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* conjunctiva:
-covers sclera -surrounds cornea -contains blood vessels that contribute to peripheral corneal nutrition -bulbar conjunctiva (along eye) -upper/lower fornix -upper/lower palpebral conjunctiva (along eye lid) * eyelids: protection * tear film: -supplies oxygen to cornea -maintains moisture content of tissue -(cornea and conjunctiva are not keratinized) |
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Anatomical Directions
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* superior/cranial
* inferior/caudal * anterior/ventral * posterior/dorsal * lateral * medial * proximal * distal ** vitread/inner ** sclerad/outer |
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Anatomical Planes
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* sagittal
* transverse/horizontal * coronal/frontal |
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Refractive Conditions
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Emmetropia: light rays from far are focused on retina
Hyperopia: light rays from far are focused behind retina Myopia: light rays from far are focused in front of retina |
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Terminology: suture
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junction between bones
(sutures of the face are named by combining names of bones joined) |
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Terminology: fossa
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indentation
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Terminology: foramen
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passage through a bone
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Terminology: fissure
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opening between bones
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Terminology: process
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projection from bone
(named by the bone with which is articulates) |
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Skull Bones Named
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* frontal (forehead)
* parietal (sides) * temporal (lower sides) * sphenoid (behind eye socket) * zygoma (cheek bones) * maxilla (upper jaw) * mandible (lower jaw) |
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Orbit
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* four-sided pear-shaped pyramid
- apex - base * medial walls are parallel * lateral walls, if extended, would form right angle |
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Orbital Bones:
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* sphenoid
* ethmoid * lacrimal * maxillary * frontal * zygomatic * palatine (figure 7-13) |
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Orbit Roof:
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* frontal bone:
-fossa (for lacrimal gland) -foramen (supraorbital, supratrochlear) (trochlea: u-shaped cartilage for tendon of superior oblique) * sphenoid bone: -lesser wing |
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Orbit Floor:
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* maxillary bone:
-infraorbital groove ~> infraorbital canal -infraorbital foramen below margin * zygomatic bone: -zygomaticomaxillary suture * palatine bone: (L-shaped bone) -horizontal plate in roof of mouth -vertical stem behind nose -orbital process at tip of stem |
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Medial Wall
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(thinnest wall)
* maxillary bone: -frontal process * lacrimal bone: (smallest orbital bone) -frontal process of maxilla and lacrimal bone from the fossa for lacrimal sac -anterior crest -posterior crest * ethmoid bone: -papyraceous (paper thin) -frontoethmoidal suture contains foramina * sphenoid bone: -body |
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Lateral Wall
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(strongest wall)
*zygomatic bone: -foramina for nerves and vessels -marginal orbital tubercle - bone prominence for CT attachment *sphenoid bone: -greater wing |
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Orbital Margins
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Bones participating:
- frontal, zygomatic, maxillary - forms a spiral that is discontinuous at medial edge Characteristic features: - supraorbital notch - infraorbital foramen |
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Orbital Foramina and Fissures: list all
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* optic foramen
* superior orbital fissure * inferior orbital fissure |
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Orbital Foramina and Fissures:
Optic Foramen |
* at apex of orbit
* formed by struts that join the lesser wing to the body of the sphenoid |
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Orbital Foramina and Fissures:
Superior Orbital Fissure |
* space between lesser and greater wings
* common tendinous ring: tendon to which extraocular muscles are attached -oculomotor foramen: opening within ring, located anterior to optic foramen and superior to orbital fissure |
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Orbital Foramina and Fissures:
Inferior Orbital Fissure |
* space between lateral wall and floor
* bordered by four bones: -greater wing of sphenoid bone -zygomatic bone -maxillary bone -zygomatic |
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Paranasal Sinuses
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* air-filled space
* lightens weight of skull * adds resonance to voice * bones containing sinuses: -frontal -ethmoid -sphenoid -maxillary |
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Clinical Consideration:
Blow-Out Fracture |
* with blow to anterior orbit, rim stays intact.
* force of orbital contents often fractures floor along infraorbital canal * muscles and connective tissues may become entrapped * results in limited ocular motility |
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Orbital Connective Tissue
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* dense connective tissue
* complex network throughout orbit, all structure are interconnected |
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Periorbita
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* periosteum of the orbit
* LOCATION: covers orbital bones * FUNCTION: carried blood and nerve supply to bones; attachment for muscles, tendons and ligaments |
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Orbital Septum
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Orbital Septum = palpebral fascia + septum orbitale
* LOCATION: circular diaphragm runs from orbital margin to tarsal plate within eyeball (tendon of levator muscle passed through it) * FUNCTION: protection; provides infections of face from entering orbit * RELATIONSHIPS AT: -lateral canthus: anterior to lateral check ligament and lateral palpebral ligament -medial canthus: anterior to medial check ligament; posterior to medial palpebral ligament, Horner's muscle, and lacrimal sac |
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Tenon's Capsule
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Tenon's Capsule = bulbar fascia
* LOCATION: surrounds globe, outer to episclera, inner to conjunctiva * FUNCTION: protects the globe from orbital infection, attachment for the extraocular muscles |
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Suspensory Ligament (of Lockwood)
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* inferior muscle sheathes contribute to ligament
* LOCATION: hammock-like sheets run from medial to lateral orbit below globe * FUNCTION: supports globe |
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Clinical Consideration:
Preseptal Cellulitis |
* infection involving glands of eyelid
* inflammation remains anterior to orbital septum |
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Clinical Consideration:
Orbital Cellulitis |
* serious medical complication following sinus infection
* is treated aggressively, may involve hospitalization * Tenon's capsule may prevent infection from entering globe |
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Clinical Consideration:
Exophthalmos |
Exophthalmos = proptosis
* space-occupying structure causes protrusion of globe |
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Structure of Striated Muscle
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*epimysium:
-surrounds entire muscle *perimysium: -surrounds bundles of muscle fibers *endomysium: -surrounds muscle fiber |
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Myofibrils
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*myosin:
-long, 2-headed filament *actin: -double-helix molecule -troponin-tropomyosin complex |
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Sarcomere
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*unit of contraction
*Z-line to Z-line -Z-line: disc -I-band: only thin fibers -H-zone: only thick fibers -A-zone: overlap |
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Mechanism of Muscle Contraction
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*action potential
*release of ACh at neuromuscular junction *Ca++ released throughout sarcoplasm *causes conformational biochemical change of troponin-tropomyosin complex *allows active site on actin to bind with myosin head *ATP released from myosin head causing head to bend forward *pulls actin along *thus, sarcomere is shortened |
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Extraocular Muscle Structure
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*Motor Unit:
-muscle fibers innervated by a neuron *Extrafusal Fibers: -contractile fibers *Intrafusal Fibers: -non-contractile fibers -myotendinous cylinder (muscle spindle specific to EOM) |
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Extraocular Muscle Layers:
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EOM have a layered organization:
Global Layer -adjacent to globe -extends the full length of the muscle -attached at the origin and insertion tendons -causes movement of the globe Orbital Layer -adjacent to orbital bone -smaller diameter fibers -end before the muscle tendon -function: positions connective tissue muscle pulleys that influence the muscle rotational axis |
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Eye Movement: Fick's Axes
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Transverse: x- axis
-from temple to temple Sagittal: y-axis -through center of cornea out of center of back of eye Vertical: z-axis -form superior to inferior |
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Eye Movements: Ductions and Torsions
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Ductions: movement of one eye
-adduction: toward nose (rotation about z-axis) -abduction: away from nose (rotation about z-axis) -elevation: up (rotation about x-axis) -depression: down (rotation about x-axis) Torsions: movement of 12 o'clock location on limbus -intorsion: moves towards nose -extorsion: moves away from nose (happens when head tilts) |
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Eye Movements: Vergences and Versions
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(both are binocular movements)
Vergence: involve both eyes moving in the opposite left-right direction -ie. convergence, divergence Versions: involve both eyes moving in the same left-right direction |
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Positions of Gaze
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Primary: head erect, eye straight ahead, focused to infinity
Secondary: rotations around horizontal (x) or vertical (z) axis Tertiary: rotations around both horizontal and vertical axes |
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Extraocular Muscles: names
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*superior rectus
*medial rectus *lateral rectus *inferior rectus *superior oblique *inferior oblique |
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Rectus Muscles
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Common Origin:
-common tendinous ring aka Annulus of Zinn; oculomotor foramen Common Insertion: -Spiral of Tillaux |
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Medial Rectus
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Origin: tendinous ring and optic nerve sheath
Insertion: on globe, sclera, line of insertion parallel to z-axis and perpendicular to x-axis Action: adduction Innervation: cranial nerve III (ocular motor) |
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Lateral Rectus
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Origin: tendinous ring (superior and inferior branches) and sphenoid
Insertion: line of insertion parallels that of medial rectus Action: abduction Innervation: cranial nerve VI (abducence) |
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Superior Rectus
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Origin: common tendinous ring and optic nerve sheath
Insertion: line of insertion makes angle with y-axis Location: lies inferior to levator muscle Action: -Primary: elevation -Secondary: adduction, intorsion Innervation: cranial nerve III (ocularmotor) |
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Inferior Rectus
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Origin: common tendinous ring
Insertion: line of insertion parallels that of superior rectus insertion Action: -Primary: depression -Secondary: adduction, extorsion Innervation: cranial nerve III (oculormotor) |
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Superior Oblique
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Origin:
-anatomical (termination): lesser wing of sphenoid -physiological: trochlea Insertion: superior, posterior and lateral globe Location: muscle belly lies superior to muscle cone (superior to muscle belly of superior rectus) Action: (contraction causes globe to move toward trochlea rather than anatomical origin) -Primary: intorsion -Secondary: depression, abduction Innervation: cranial nerve IV (trochlear) |
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Mnemonic for Innervation
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LR6 SO4 R3
lateral rectus: cranial nerve VI superior oblique: cranial nerve IV all the rest: cranial nerve III |
