394
UNIT 3
Organ Systems
Tarsal
Plate
Tendon of the
levator
palpebrae
muscle
Palpebral
conjunctiva
Lid margin
Eyelash
follicles
Skin
Meibomian
(Tarsal)
glands
Superior
tarsal muscle
Orbicularis
oculi muscle
A
Figure 20-3A.
Overview of the upper eyelid.
H&E,
3
7.6
A low-power photomicrograph of the
upper eyelid
is shown. The
eyelids contain an outer layer of
skin
; a middle layer of
muscles
,
glands
, and
tarsal plate
; and an inner layer of
conjunctival tissue
(
palpebral conjunctiva
). Eyelids cover and protect the eye from
the environment, injury, and intense light. They also maintain a
smooth corneal surface by spreading a F
lm of lacrimal fl
uid (
tears
)
evenly over the cornea to moisten the eye. The skin of the eyelids is
thin, loose, and delicate and, therefore, may permit extreme swell-
ing. The internal lid is covered by a
palpebral conjunctiva
, a layer
of stratiF
ed low columnar epithelium. It is continuous with the
bulbar conjunctiva
where it covers the sclera of the eyeball. The
tarsal plate
is a dense F
broelastic tissue, which provides fl
exible
support. The
tarsal glands
(
meibomian glands
) are embedded in it.
The
eyelashes
are located in the anterior margins of the eyelids.
Eyelid
Levator
palpebrae
superioris
muscle and
its tendon
Meibomian
(tarsal) gland
Palpebral
conjunctiva
Tarsal plate
Superior
tarsal muscle
Accessory lacrimal
gland (of Krause)
Accessory lacrimal
gland (of Wolfring)
Orbicularis
oculi
muscle
Sweat
gland
Skin
Gland
of Zeis
Eyelash
Gland
of Moll
D. Cui
B
Figure 20-3B.
A representation of the upper eyelid, glands, and
muscles that control eyelid movements.
Several types of
glands
in the eyelids include (1)
meibomian (tarsal)
glands
, sebaceous glands that produce a lipid-rich substance; (2)
glands
of Zeis
, modiF ed sebaceous glands associated with the follicles of the
eyelashes; (3)
glands of Moll
, modiF ed sweat glands, associated with
eyelash follicles; and (4) a
ccessory lacrimal glands
, serous glands
that contribute to tears. The
muscles
associated with upper eyelids
are the (1)
orbicularis oculi muscle
, a circular sheet of striated muscle
which functions to close the eyelids; (2)
levator palpebrae superioris
muscle
, a thin, fl at, striated muscle that arises from the apex of the
orbit and inserts into the posterior surface of the orbicularis oculi
muscle and the skin of the upper eyelid, and which opens the eyelid;
and (3)
superior tarsal muscle
(
Müller muscle
), smooth muscle that
arises from the interstitia of the levator muscle and inserts on the
upper end of the tarsal plate and superior conjunctiva of the lid. It
joins the levator palpebrae superioris muscle in raising the upper
eyelid. (±or innervation, see text of ±ig. 20-4C.)
Figure 20-3C.
Chalazion.
Chalazion
is a chronic eyelid infl
ammatory lesion that results
from the obstruction of the ducts of either the
Zeis
or
meibo-
mian glands
, or both. Trapped sebaceous secretions leak into
the surrounding tissue and cause a
granulomatous
infl
am-
mation
. This is frequently associated with
blepharitis
and
occasionally becomes secondarily infected. Early symptoms
and signs include
eyelid swelling
and
erythema
. In time, it
changes into a F rm nodule within the eyelid or the tarsal
plate. Histologic examination reveals granulation tissue char-
acterized by focal aggregation of epithelium-like (
epithelioid
)
cells,
lymphocytes
,
giant cells of Langerhans
, and yellow
lipid-laden macrophages
. Treatment options include warm
compresses applied to the outer lid until acute symptoms dis-
appear, topical antibiotics, and surgical incision if the lesion
is large and disturbs vision.
Obstructed meibomian gland
Lipid-laden macrophage
Nodule
Lymphocyte
Gland
of Zeis
D. Cui
C
CLINICAL CORRELATION
previous page 409 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online next page 411 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online Home Toggle text on/off