ch 15 EYES Flashcards
two rapid window shades that further protect the eye from injury, strong light, and dust
eyelids
is the elliptical open space between the eyelids
palpebral fissure
the border between the cornea and sclera
limbus
is the corner of the eye, the angle where the lids meet
canthus
At the inner canthus is a small, fleshy mass containing sebaceous glands.
caruncle
are strips of connective tissue that give it shape
tarsal plates (upper eye lid)
tarsal plates contain the ?, modified sebaceous glands that secrete an oily lubricating material onto the lids. This stops the tears from overflowing and helps form an airtight seal when the lids are closed.
meibomian glands(upper eye lid)
exposed part of the eye has a transparent protective covering .
-thin mucous membrane folded like an envelope between the eyelids and the eyeball
conjunctiva
lines the lids and is clear, with many small blood vessels
palpebral conjunctiva
overlays the eyeball, with the white sclera showing through
bulbar conjunctiva
covers and protects the iris and pupil.
cornea
provides constant irrigation to keep the conjunctiva and cornea moist and lubricated
-secretes tears
lacrimal apparatus
tears wash across the eye and are drawn up evenly as the lid blinks drain into the ?, visible on the upper and lower lids at the inner canthus.
puncta
- Six muscles attach the eyeball to its orbit
- superior rectus, inferior rectus, lateral rectus, and medial rectus, superior oblique m, inferior oblique
- two slanting, or oblique, muscles are the superior and inferior muscles.
Extraocular Muscles
two eyes move, their axes always remain parallel
conjugate movement
are important because the human brain can tolerate seeing only one image
Parallel axes
animals can perceive two different pictures through each eye, humans have a
binocular, single-image visual system
is stimulated by three cranial nerves (CNs)
EOMs
abducens nerve (CN VI) innervates the lateral rectus muscle (which abducts the eye); the trochlear nerve (CN IV) innervates the superior oblique muscle; and the oculomotor nerve (CN III) innervates all the rest—the superior, inferior, and medial rectus and the inferior oblique muscles.
three cranial nerves (CNs)
only parts accessible to examination are the sclera anteriorly and the retina through the ophthalmoscope.
Internal eye
(1) the outer fibrous sclera,
(2) the middle vascular choroid, and
(3) the inner nervous retina (inside is transparent vitreous body)
asymmetric sphere composed of three concentric coats(internal eye)
is a tough, protective white covering. It is continuous anteriorly with the smooth, transparent cornea, which covers the iris and pupil
sclera (outer layer)
is part of the refracting media of the eye, bending incoming light rays to focus them on the inner retina.
-transparent, and very sensitive to touch; contact with a wisp of cotton stimulates a blink in both eyes, called the corneal reflex. The trigeminal nerve (CN V) carries the afferent sensation into the brain, and the facial nerve (CN VII) carries the efferent message that stimulates the blink.
cornea
has dark pigmentation to prevent light from reflecting internally and is heavily vascularized to deliver blood to the retina.
choroid