In the back of the eye, the
vessels pierce the sclera. The dura mater that encloses these
structures is continuous with the sclera.
The Middle Tunic
The middle, or vascular, tunic of the eyeball (uveal layer)
the ciliary body, and the iris. The
choroid coat, in the posterior F ve-sixths of the globe of the
eye, loosely joins the sclera. Blood vessels pervade the choroid
coat and nourish surrounding tissues. The choroid coat also
contains abundant pigment-producing melanocytes that give
Transverse section of the right eye (superior view).
Anterior portion of the eye.
it a brownish-black appearance. The melanin of these cells
absorbs excess light and helps keep the inside of the eye dark.
which is the thickest part of the mid-
dle tunic, extends forward from the choroid coat and forms
an internal ring around the front of the eye. In the ciliary
body are many radiating folds called
two distinct groups of muscle F
bers that constitute the
shows these structures.
Many strong but delicate F
(zonular F bers), extend inward from the ciliary pro-
cesses and hold the transparent
in position. The distal
ends of these F
bers are attached along the margin of a thin