Eyes Flashcards
what are the eyelids?
//two movable shades //protect the eye from injury, strong light and dust
which eyelid is more mobile?
the upper
what are eyelashes?
//short hairs in double or triple rows that curve outward from the eyelid margins //filter out dust and dirt
what is the palpebral fissure?
//the elliptical open space between eyelids
what is the limbus?
the border between the cornea and sclera
what is the canthus?
//corner of the eye //angle where eyelids meet
what is the caruncle?
//at the inner canthus //is a small fleshy mass containing the sebaceous glands
with respect to the upper eyelid, where does a nurse expect to see it in relation to the iris?
when the eyes are open upper eyelid covers part of iris
where is the lower eyelid margin when the eye is open?
at the limbus (the border between cornea and sclera)
what are tarsal plates?
//strips of connective tissue that give shape to the upper eyelids
//contain meibomian glands
what are the meibomian glands?
//modified sebaceous glands the secrete oily lubricating material onto eyelids //the secretion stops tears from overflowing and helps eyelids to form an airtight seal when closed //located in the tarsal plates (connective tissue of upper eyelid)
what is the conjunctiva?
//a thin mucous membrane folded like an envelope between the eyelids and the eyeball
//transparent and covers the exposed part of the eye
what is the palpebral conjunctiva?
//lines eyelids //clear with many small blood vessels //forms a deep recess and then folds back over eye
what is the bulbar conjunctiva?
//overlies eyeball //is clear, but white sclera shows through it
where does the conjunctiva merge with the cornea?
at the limbus
what does the lacrimal apparatus do?
provides constant irrigation to keep conjunctiva and cornea moist and lubricated
what makes tears?
lacrimal glands
what is the path of tears?
tears wash across the eye and are drawn up evenly as the eye blinks
drain into puncta, then nasolacrimal sac through the nasolacrimal duct emptying into the inferior meatus inside the nose
what are punctum?
there is a superior and inferior puncta
are located just above and just below carnucle (a interior corners of eyes)
how many muscles attach the eyeball?
six
what are the six muscles that attach the eyeball (extraocular muscles)?
superior rectus inferior rectus lateral rectus medial rectus superior oblique inferior oblique
what is the function of the six muscles attached to the eyeball?
direct eye to area of person’s interest
//enable both straight and rotary movement
//each muscle is yoked with one in the other eye so that the two eyes move with axes always parallel (conjugate movement)
what is conjugate movement?
yoking of muscles that move eyeball (extraocular muscles) causes them to move with axes always parallel, this is conjugate movement
why is conjugate movement important?
the human brain can tolerate only seeing one image and conjugate movement ensures this
which extraocular muscles are straight?
the four rectus muscles //superior //inferior //lateral //medial
which extraocular muscles are slanting?
the two oblique muscles //superior //inferior
what is the name for the muscles that attach to and move the eyeball?
extraocular muscles
what nerves stimulate the extraocular muscles?
//cranial nerve VI (abducens nerve) innervates the lateral rectus muscle //cranial nerve IV (trochlear nerve) innervates the superior oblique muscle //cranial nerve III (oculomotor nerve) innervates all the other muscles
what are the three concentric coats that compose the eye?
1) outer fibrous sclera
2) middle vascular choroid
3) inner nervous retina
where is the vitreous body?
inside the retina
what colour is the vitreous body?
transparent
what makes the outer layer of the eye?
//sclera (protective white covering) //cornea (smooth transparent, covers iris and pupil)
what is the sclera
the tough, protective, white covering
//continuous anteriorly with smooth, transparent cornea
what is the cornea?
//part of refracting media of the eye //bends incoming light rays so they are focused on the retina within //covers iris and pupil and is transparent //sensitive to touch //corneal reflex occurs if wisp of cotton make contact with cornea
what cranial nerves are involved in the corneal reflex?
//the trigeminal nerve (cranial nerve V) carries the afferent sensation to the brain //the facial nerve (cranial nerve VII) carries the efferent message that stimulates the blink
what makes up the middle layer of the eye?
//choroid //iris //pupil //lens //anterior chamber //posterior chamber
what is the choroid?
//dark pigmented layer, prevents internal reflection within the eye //continuous with ciliary body and iris //highly vascularized to deliver blood to the retina
what is the iris?
//functions as diaphram, varying the opening (pupil) at its center //controls amount of light admitted to retina //muscles contract for bright light and to accommodate near vision //muscles relax to let in more light when it is dim and for far vision
what do the muscles of the ciliary body control?
the thickness of the lens
what is the pupil?
//round and regular center of the iris //size determined by balance between parasympathetic and sympathetic chains of the autonomic nervous system
what nerves control the dilation of the pupil?
//stimulation of parasympathetic branch through cranial nerve III causes constriction //stimulation of the sympathetic branch dilates the pupil and elevates the eyelid
what is the lens?
//a transparent biconvex disc located just behind the pupil //serves as refracting medium, keeping a viewed object in continual focus on the retina //thickness controlled by ciliary body //bulges for focusing on near objects and flattens for far objects
where is the anterior chamber?
posterior to cornea and anterior to the iris and lens
where is the posterior chamber?
lies behind iris and to sides of lens
what do chambers contain?
the aqueous humor, which is continuously produced by ciliary body
what does aqueous humor do?
flows constantly from ciliary body and delivers nutrients to surrounding tissues
drains metabolic wasts
what is the retina?
visual receptive layer of eye in which light waves are changed into nerve impulses
surrounds vitreous humor
what is the vitreous humor?
soft, gelatinous contained by retina
what retina structures can be viewed with opthalmascope
optic disc
retinal vessels
general background
macula
what is the optic disc?
aka optic papilla
is the area where fibres from retina converge and form optic nerve
located towards nasal side of retina
what are the characteristics of the optic disc?
colour from creamy yellow orange to pink
round or oval shape
margins are distinct and sharply demarcated, especially on temporal side
physiological cup, the smaller circular area inside disc where vessels enter and exit
what are the retinal vessels
paired artery and vein extending to each quadrant, growing progressively smaller in calibre as they reach periphery
artery bright red and narrower than vein.
what is the thin sliver of light seen on the arteries in the retina?
arterial light reflex
where is the macula?
on the temporal side of fundus
what area has sharpest, keenest vision?
fovea centralis…in macula
what is the pupillary light reflex
normal constriction of pupils when bright light shines on retina
what is direct constriction?
constriction of pupil when directly exposed to light
what is consensual constriction?
when pupil constriction occurs in one eye because the pupil constricted in the other
