Anatomy

random

pinna

aka auricle

• located outside the head

• acts as a funnel which assists in directing sound further into the ear/auditory canal → tympanic membrane

eustachian tube

middle ear to pharynx

• circumvents excess pressure when pressure builds in the ear → equalization of air pressure between middle ear and atmosphere

• rapid changes in altitude can result in ear “popping” d/t equalization process

intraocular segment

the axons of the photoreceptors as they exit the eye

• shortest segment of the nerve (1mm deep, 1.5mm vertical diameter)

• aka optic disc or ONH

intraorbital portion of optic nerve

the segment that extends from globe to optic foramen at the orbital apex

• 25-30mm in length

intracanalicular region of the optic nerve

the segment that traverses the optic canal

• 6mm in length

• fixed to the canal due to fusion of the dura material with the periosteum

intracranial segment

the portion that extends to join the optic chiasm

• fibers that course posteriorly from optic chiasm are referred to as optic tract

how does a muscle contraction happen?

AP → releases ACh → sarcolemma → uptaken by other side of terminal → AP via T-tubules → release of Ca2+ → tropomyosin and troponin component exposes itself to myosin when Ca2+ is present → now ready to connect to myosin → ATP and bind and release → cycle continues as long as Ca2+ is present

primary and secondary actions for SR

1. elevate

2. intort

3. adduct

SIN RAD

primary and secondary actions for IR

1. depress

2. extort

3. adduct

primary and secondary actions for IO

1. extort

2. elevate

3. abduct

primary and secondary actions for SO

1. intort

2. depress

3. abduct

bones of orbital roof

“Front-less”

• Frontal bone

• Lesser wing of sphenoid

bones of medial orbit

”SMEL”

• sphenoid bone (body; strongest)

• maxillary bone

• ethmoid bone (thinnest)

• lacrimal bone

bones of lateral orbit

“Great Z”

• greater wing of sphenoid

• zygomatic bone

bones of floor of orbit

“My Pal gets Z’s on the floor”

• maxillary bone (weakest)

• palatine bone

• zygomatic bone

confluence of sinuses is made of

• straight sinus

• superior sagittal sinus

• occipital sinus

• transverse sinus

internal carotid artery branches into:

OPAM

• ophthalmic a.

• posterior communicating a.

• anterior cerebral a.

• middle cerebral a.

what goes thru superior orbital fissure?

LFT NOA, sov

• lacrimal n.

• frontal n.

• trochlear n.

• nasociliary n.

• oculomotor n.

• abducens n.

• superior ophthalmic vein

NOA passes thru SOF and CTR

what goes thru the optic canal?

• optic nerve

• ophthalmic a.

what goes thru the inferior orbital fissure?

• CN V2 (maxillary br. of trigeminal n.)

• inferior ophthalmic vein

• infraorbital a.

• infraorbital v.

• infraorbital n.

• zygomatic n.

3 layers of tear film

lipid: lubricates, prevent evaporation

• meibomian, zeiss, moll

• evaporative dry eye, MGD, rosacea, decreased blink rate, poor fitting CL, Accutane

aqueous: nourishes, protects cornea

• main lacrimal gland (95%), accessory (Krause, Wolfring)

• isotonic solution

• increased production due to parasympathetic stimulation

• lysozyme, beta lysin, lactoferrin, IgA

  • lysozyme cleaves peptidoglycan in bacterial cell wall (pcn, cephalosporins, Bacitracin)

mucous: adheres tears to eye

• supplied by conj goblet cells

  • vit A deficiency → decrease in goblet cells → dry eye, bitot spots

    • vitamins D,E,A,K are fat-soluble

• corneal epi cells → glycocalyx

marangoni flow

tears flow from low temperature areas (cornea) to higher temperature areas (lid margins)

compared to typical skeletal muscles, EOMs:

• blood supply is denser in EOMs

• nere supply is denser and more finely tuned in EOMs

• EOM movements are faster and more fatigue resistant

origin of EOMs

common tendinous ring (annulus of zinn) → SR, IR, LR, MR

• all recti muscles originate from CTR and insert on the globe to form the Spiral of Tillaux

• SR inserts the furthest away, MR inserts the closest to the limbus

maxillary bone → IO

LW of sphenoid → SO

the ___ sheath and ___ sheath combine to form the suspensory ligament of Lockwood

IR and IO

what forms a tight barrier between cells to impede the intercellular movement of particles in the corneal epithelium ?

• zonula occludens (tight junctions)

• desmosomes

what factors increase the risk of recurrent corneal erosions?

RCE: poor adhesion between epithelium and basement membrane

• poor hemidesmosome attachments

• EBMD

• age-related thickening of BM

characteristics of Bowman’s layer

• resists damage

• maintains curvature, absorbs UVB

• past Bowman’s, nerves lose Schwann covering and pass into epithelium as naked nerves

• cannot regenerate, will scar

clinical conditions associated with Bowman’s layer

• band keratopathy: calcium deposits (“swiss cheese”)

• pterygia

• crocodile shagreen (bilateral)

• Reis-Buckler’s dystrophy

• keratoconus: begins in Bowman’s

  • advanced → hydrops in Descemet’s

• refractive surgery

  • flap created in LASIK = epithelium and Bowman’s

  • PRK = laser thru Bowman’s → post-op haze

• limbal girdle of Vogt: Bowman’s degeneration (d/t Ca2+ deposits)

anterior 1/3 of collagen fibrils in corneal stroma vs. posterior 2/3

anterior 1/3

• thinner lamellae

• more covalent bonding (cross-linking)

• more structure — branching, interweaving

posterior 2/3

• larger lamellae

• more regular arrangement

components of the corneal stroma

1. collagen fibrils (type 1 collagen)

2. keratocytes → fibroblasts

   1. make collagen, ECM

3. ground substance

   1. proteoglycans (protein + GAGs)

   2. attracts water

4. blood cells (WBC, lymphocytes, macrophages, leukocytes)

5. stromal stem cells

which corneal layers can potentially scar? which layers can regenerate?

will scar — Bowman’s, stroma

can regenerate — epithelium, stroma, Descemet’s

what properties of drugs allow it to penetrate the cornea?

• small in size

• uncharged

• lipid soluble

weak base

what layer(s) of the cornea are hydrophobic? hydrophilic? lipophilic?

• epithelium: hydrophobic, lipophilic

• stroma: hydrophilic

• endothelium: lipophilic

where is type 1 collagen seen in the body?

• Bowman’s layer of cornea

• bones

• stromal layer of cornea

• sclera

associated with Ehlers-Danlos, osteogenesis imperfecta

ERG waves

A wave: photoreceptors

B wave: bipolar cells, Mueller cells

• oscillations are due to amacrine cells

C wave: RPE

D wave: off bipolar cells

what structures are in the forebrain? midbrain? hindbrain?

forebrain:

• cerebrum

• olfactory lobes

• thalamus

• hypothalamus

• limbic system

• pituitary gland

• pineal gland

midbrain:

• tectum

• substantia nigra

• red nucleus

hindbrain:

• cerebellum

• pons

• medulla oblongata