Sclera Flashcards
the globe is composed of what two spheres with different radii of curvature
the cornea anteriorly and the sclera posterior
how much of the eyeball is sclera
5/6th
where is the sclera the thickest
near the optic nerve and gradually decreases near the equator
where is the sclera the thinnest
just posterior to the tendinous insertions of the recti muscles
what is the posterior scleral foramen
the aperture where the fibers of the optic nerve exit the eye
what is the lamina cribrosa
a sieve (weak) like structure that permits passage of the axons of the retinal ganglion cells as well as the central artery and vein of the retina
when do the nerve fibers become myelinated exiting the eye
once they have pierced the lamina cribrosa
where are the apertures located in the sclera
anterior, posterior, and middle
where are the anterior apertures located on the sclera
near the tendinous insertions of the recti muscles, allow for passage of the anterior ciliary arteries
what are the middle scleral apertures for
exiting the vortex nerves
where are the scleral posterior apertures
around the optic nerve, allow for ciliary nerves and vessels
what are the 3 layers of the sclera
episclera, scleral stroma, lamina fusca
what is the episclera comprised of
loose, vascularized, connective tissue
where does the blood supply come from for the anterior episclera
anterior ciliary arteries
where does the blood supply come from for the posterior episclera
short posterior ciliary arteries
what is the scleral stroma comprised of
collagen bundles, interlacing, varying in thickness (why it is opaque)
what is the lamina fusca
the innermost portion of the sclera, dark appearance, melanocytes
what is the scleral spur
a projection or ridge of scleral tissue that is oriented circumferentially around the inner aspect of the sclera
what muscle originates in the scleral spur
the longitudinal ciliary muscle fibers
what innervates the posterior sclera
short posterior ciliary nerves
what innervates the anterior sclera
two long ciliary nerves
what blood vessels supply the episclera
the anterior ciliary arteries anterior to the tendinous insertions of the recti muscles
what blood vessels supply the posterior episclera
long and short posterior ciliary arteries
what blood vessels supply the scleral stroma
it is avascular
