402
UNIT 3
Organ Systems
Anterior
Posterior
Fig. 1-1C
Anterior
Posterior
iliary muscle
C
Ciliary
Ciliary
muscle
muscle
Ciliary processes
Ciliary
body
Zonular fibers
Lens
Lens
Iris
Sclera
Limbus
(corneoscleral
junction)
Cornea
Anterior chamber angle
(iridocorneal angle)
Anterior
chamber
Posterior
chamber
Ciliary
muscle
A
Lens
Ciliary
processes
Zonular fibers
Pigmented
epithelium
Unpigmented
epithelium
Ciliary
Ciliary
muscle
muscle
Ciliary
muscle
B
Anterior
Posterior
Lens
D. Cui
Ciliary
processes
Trabecular
meshwork
Canal of
Schlemm
Canal of
Schlemm
Sclera
Bulbar
conjunctiva
Ciliary
epithelium
Trabecular
meshwork
Anterior
chamber angle
Retina
Ciliary ring
(pars plana)
Ora serrata
Ciliary process
(pars plicata)
Zonular fibers
Zonular fiber
Ciliary process
Ciliary
Ciliary
muscle
muscle
Ciliary
muscle
C
Figure 20-11A.
Overview of the ciliary body and nearby
structures.
H&E,
3
19
The
ciliary body
is located internally to the anterior margin of the
sclera. The transition between the cornea and sclera is the
limbus
(
corneoscleral junction
). This is an important landmark for eye
surgery procedures. The surface of the anterior portion of the cili-
ary body (
ciliary process
) has zonular F bers attached to it and is
in contact with the aqueous humor. The surface of the posterior
portion of the ciliary body is in contact with the vitreous body.
Figure 20-11B.
Ciliary processes and the ciliary muscle.
H&E,
3
87; inset
3
348
Ciliary processes
have loose connective tissue cores and are
covered
by two layers of epithelium: (1) a
nonpigmented layer
and (2) a
pigmented layer
. The apical surfaces of the two epithelial layers
face each other. Their basal surfaces each rest on a basement mem-
brane, one bordering the ciliary stroma and the other bordering
the aqueous humor. The cells are F rmly connected by junctional
complexes. The
ciliary muscle
contains three smooth muscle F ber
groups: (1)
longitudinal muscle ± bers
, which stretch the choroid
to alter the opening of the anterior chamber angle for drainage of
aqueous humor; (2)
radial muscle ± bers
, which increase tension on
the zonular F bers and cause the lens to fl atten, allowing the eyes to
focus for distant vision; and (3)
circular muscle ± bers
, which relax
the tension on the zonular F bers and cause the lens to become more
convex to accommodate for near vision. Ciliary muscles are inner-
vated by
parasympathetic nerve ± bers
of the oculomotor nerve.
Figure 20-11C.
Ciliary body, transverse and posterior views.
H&E,
3
34; inset
3
62
The
ciliary body
consists of (1) the
ciliary ring
(
pars plana
), the
region that contains a ring of smooth muscle (
ciliary muscle
)
surrounded by loose connective tissue and covered by the
ciliary
epithelium and (2) the
ciliary processes
(
pars plicata
), F
nger-
like structures which contain many fenestrated capillaries that
produce aqueous humor. Aqueous humor fl
ows from the pos-
terior chamber through the pupil to the anterior chamber, then
passes into the
trabecular meshwork
and F nally into the
canal of
Schlemm
(see ±ig. 20-12C).
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