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The anatomy and histology of the human eye online

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drawn from him. (Archiv, 1, x, 2 ; Compte rendu, 1862.) Be-
neath this muscle are the two tarsal cartilages, and the facial
surface of the bones all around the orbit, and the membrane
between the cartilages and the orbital border, the fascia tarso-
orUtalis.

Below the internal palpebral ligament a small portion of its
fibres rest on the anterior surface of the lachrymal sac. Toward
the periphery of this muscle there are located, in places, other
muscles between it and the bones, and in other localities masses
of fatty tissue. Over the opening of the orbit there is not much
fatty tissue in contact with the muscles. Behind the palpebral
ligaments is the fatty tissue of the orbit. Backward from the
outer commissure of the lids the outer palpebral ligament is
attached, composed of connective tissue of firm texture, and
rich in elastic fibres, which is there connected with the orbital
surface of the malar bone, and with the tunica vaginalis bulbi,
which retains the outer angle of the eye a considerable distance



152



THE ANATOMY AND HISTOLOGY



from the orbital border. Immediately above this band is located
the lower part of the lachrymal gland. At the bone it projects
2'" within the orbital cavity.



FIG. 66.




The fixed points of the orbicularis are mostly situated at the
nasal side, some also on the temporal side ; a portion of the
fibres along the periphery have variable points of attachment,
being in a measure dependent on the contractions of other
muscles.

The attachments of the muscle at the nasal side are at the
crest of the lachrymal bone, at the inner lid-band (tendo-oculi),
at the orbital border, at the facial surface of the superior
maxillary, and the frontal bones. As the ligaijientwn canthi
internum is so intimately mixed with an intelligible description
of the orbicularis, a further description of it is required here.



OF THE HUMAN EYE.



153



The inner lid-band (tendo-oculi) is closely connected with the
thin skin covering it, and is visible through it. By pulling




(?, a, a, a. Lachrymal part of the orbicularis muscle (Homer's muscle) nearest the
ligamentum canthi internum, and partly covered by the fibres of the lid-band portion
of the muscle.

b, b, I), b. Extent of the lid-band portion of the .muscle, nearest the lid-band (tendo-
oculi), and above it, part of it rising out of the deeper parts beneath.

c, c, c, c. Extent of the orbital portion, the origin of the fibres in a great measure not
being visible.

d, Descending branch of the peripheral portion, sending fasciculi to the skin at/, and
also some downward toward the angle of the mouth.

e, e. Ascending part of the peripheral portion, sending almost constantly one or more
bundles, as seen at g, to the angle of the mouth.

h. Bundles extending to the aponeurosis of the muscles of the forehead, and sometimes,
as seen at h, to the temporal aponeurosis.

i. Passage" of the peripheral fibres to the muscles of the forehead.

k. Points where the fibres from the third and fourth divisions of the muscles pass to
and beneath the eyebrows.

/. Triangular layer of the peripheral fibres, between the lid-band and the inner half
of the eyebrows.

m. A slender bundle of fibres, extending from the dorsum of the nose to the eyebrows
and integument of the forehead.

The borders of the tarsal cartilages, the position of the cornea in a state of rest, and
the longitudinal line where the fibres of the first and second parts have a peculiar rela.
tion, are marked with dotted lines.

n. Shows the point where the outer lid-band touches the bone.

(From At It.)



154 THE ANATOMY AND HISTOLOGY

the outer commissure of the lids outward, and a little upward,
with the thumb, its whole length may be seen. Its free border
is a little more than 3"' long, and passes outward across the
lachrymal sac. Its smaller, inner half rests on the superior
maxillary bone, and its outer larger half on the lachrymal
sac. Its under surface, which forms an acute angle with the
anterior surface of the lachrymal sac, gives off, on' its whole
length, closely packed muscular fibres, which are attached to
the anterior surface of the tear sac. Its upper surface, which
immediately passes over into the thick fibrous covering of the
tear sac, gives off muscular fibres to the lids only in its outer
half.

Those given off from the inner half of its surface do not
belong to this muscle, as will be explained hereafter. The
inner end of the ligamentum canthi internum is gradually lost
in the periosteum of the superior maxillary bone. Outward
this lid-band is divided into two horns, which may also be seen
through the skin, and which form the triangular space between
the lids which incloses the caruncula lachrymalis. These pro-
cesses of the lid-band serve for the attachment of numerous
muscular fibres, and are gradually lost about half way in their
course to the puncta lachrymalia. Behind these processes the
lachrymal canals sink deep to perforate the muscle coming
from the crest of the lachrymal bone, so as to reach the outer
wall of the lachrymal sac, into which they open. The orbicu-
laris completely surrounds the orbit and eyelids, its peripheral
bundles to a certain extent forming isolated parts. The mus-
cular bundles of its central half originate from the crest of the
lachrymal bone, and from the inner lid-band are quite thin and
pale, especially in the region of the upper lid.

They are arranged singly, side by side, with the exception of
the region near the border of the lids, where they rest on each
other. At the temporal side, where the upper and lower halves
meet, there is a peculiar arrangement, soon to be noticed. Above
and below the middle of the palpebral fissure, the periphery of
this portion of the muscle about corresponds with the border



OF THE HUMAN EYE. 155

of the orbit ; outward from the fissura palpebralis these mus-
cular fibres extend 1'" to 8'" from the outer commissure 011 to
the malar bone.

The bundles of fibres of the peripheral half originate from
that part of the superior maxillary bone which borders on the
lachrymal groove, on to the region of the infra-orbital canal,
and form a line less marked on the frontal bone, which rises in
the region of the crest of the lachrymal bone, on to the indsura
supra-orbitalis, partly from the facial surface of the bones along
the described line of insertion, and from the lachrymal sac.
The different parts of this muscle will be described according
to the origin of their muscular bundles.

1. The portio lachrymalis (Horner's muscle, which Arlt con-
siders a part of the orbicularis) arises by a short tendon, about
3'" in breadth from the upper third of the crest of the lach-
rymal bone. From its origin to its division it is flat and ob-
long in shape (see Fig. 68).

The somewhat even surface looking toward the globe of the
eye, receives from the periorbita a covering of firm aponeurosis ?
which, toward the bifurcation, is in connection with the pal-
pebral ligament as well as with the tunica vaginalis bulbi.
This connection is not immediate, but is formed by connective
tissue, rich in elastic fibres, to which the caruncula lachrymalis
is attached in front. Shortly before the division the aponeu-
rosis and the connective tissue are so firmly blended, that in
their course to the cartilages it is difficult to separate them.
The opposite surface is free only nearest the upper and lower
edge ; in the middle part it is in contact with the upper portion
of the lachrymal sac, and further forward it is attached to the
outer end of the lid-band.

From the bifurcation to the inner extremities of the tarsal
cartilages the muscle forms two cords, almost round, about the
size of a raven's quill, which envelops the lachrymal canals.
Laterally, they are uninterruptedly connected with the radi-
ating muscular fibres of the orbicular muscle, emanating from



156 THE ANATOMY AND HISTOLOGY

the lid-band, and near the cartilages expand to be inserted into
their inner extremities. But few of these fibres next to the



FIG. 68.




The orbicularis, seen on its posterior surface. The inner surface of the orbit seen
(nasal side). In the back part the fornmen opticum, and further forward the ethmoi-
dal fissure ; still further forward the troehlea is seen, above which is the nervus supra-
orbitalis. Near the lower border is seen a piece of the musculus obliquus. The lachry-
mal sac is also seen, partly covered by Homer's muscle. (From Arlt.)



free border of the cartilages, and therefore beneath the hair-
bulbs of the cilia, end in the cartilage without passing beyond
the outer commissure. The breadth of this linear band of
fibres is \' n to f "'. The remainder of the fibres pass over the
loose fascia given off from the palpebral membrane, and are
therefore not immediately in contact with the cartilages, and
only near the hair-bulbs are they in connection with it. To-
ward the outer angle of the eye some fibres seem to be inserted
into the border of the cartilage. Those situated nearest the
border of the lid run parallel with it, and cover the hair-
bulbs ; those further off form large curves, with the convexity



OF THE HUMAN EYE. 157

toward the orbital border of the cartilages, the cornu growing
larger as they approach nearer the orbital border.

On the temporal side the muscular fibre-bundles of the upper
lid meet those of the lower lid at somewhat sharp angles,
which grow less acute the further away from the canthus
they meet. Those further from the outer canthus reach to or
beyond the bony rim of the orbit.

2. The portio anterior, vel portio ligamentum palpebrale inter-
num, of the orbicular muscle, is in its origin even much
stronger in its lower half than in its upper half. The fibres
originate the whole length of the lid-band, out of the sharp
angle between it and the lachrymal sac, and are so firmly con-
nected with the fibrous covering of the latter that they even
seem to originate from it. Anteriorly they are covered by a

FIG. 69.




Fig. 69 represents the outer part of the orbicularis. a. The upper cartilage, b. The
lower cartilage. The mode of union between the fibres between the lower and upper
halves of the muscle is seen. (From Ar$t.)

short, unyielding connective tissue, and through this is the
thin skin devoid of adipose tissue ; backward they are con-
nected by sheaths to the bones toward the nose. The angle
which they form with the longitudinal direction of the lid-



158 THE ANATOMY AND HISTOLOGY

band can readily be estimated when it is known that the
fibres originating at or near the outer end of the lid-band
nearly cover those bundles coming from the portio lachrymalis.
Further in, they pass by the side of them, and those originat-
ing from the inner or nasal end of the band follow about the
direction of the orbit, and at the middle of the palpebral fissure
they cover it, and from this point outward they pass over the
facial surface of the malar bone to reach there when the lids
are closed, a point 7 /r/ to 8'" outward from the outer canthus.

In this portion, as in the former, the muscular fibre-bundles
of the lower lid are much larger than those of the upper lid.

The numerous, but very delicate, muscular fibre-bundles of
this part in the upper lid originate from the outer end of the
lid-band, from the point where the fibrous covering of the
lachrymal sac is inserted into the frontal bone, and form
curves from the convex border of the cartilage on one side to
the bony border of the orbit, first running upward and then
outward.

3. The portio orbitalis has its bundles of fibres different from
the portions just described, being more powerful and darker
in color, and on the temporal side they pass from the upper
half into the lower without any interruption.

The fibres originate from the superior maxillary and from
the frontal bones. On the superior maxillary bone the line of
insertion is beneath the lid-band, along the border which helps
to form the lachrymal fossa above, and below divides the orbi-
tal surface from the anterior surface of the upper jaw-bone.
The line of insertion in the frontal bone arises by a surface not
well marked, beginning in the direction of the crest of the
lachrymal bone, and ends at the incisura supra-orbitalis. The
upper end of the lower curved line of insertion lies further
forward (almost the breadth of the lachrymal groove) than
the lower end of the upper curved line. The lid-band is In-
serted between the two, the fibres from which take between
them the fibres coming from behind from the portio lachrymalis.



OF THE HUMAN EYE. 159

The fixed points for the upper half of the orbicularis are
therefore deeper, or located further back.

The fibres of the lower half of the muscle run obliquely
downward and outward, and at the foramen infra-orbitalis,
and between it and the orbital border, they are partly covered
by the more pale and thin fibres of the portio ligamentum pal-
pebrale internum (or lid-band portion). The bundles of one
part lie side by side, and also on each other.

In the inner half the bundles of fibres are closely packed.
In the outer half they are nlore broad and flat, and are placed
side by side.

The fibres of the upper half, which nearest their origin are
partly covered by the lid-band portion, come in contact with
the incisura supra-orbitalis, up to which they constantly in-
crease behind, so as beyond it to run along the projecting
border of the orbit, and on the facial surface of the malar
bone immediately pass over into the fibres of the lower half.
At this point the innermost fibres are 4'" to 5'" distant from
the orbital border, and are separated from the subjacent bones
by some fatty tissue, which is not the case in the second por-
tion of the muscle.

4. The parts of the muscle hitherto described form an unin-
terrupted plate, with the exception of the palpebral fissure.
A considerable number of fibre-bundles are given off, called
the peripheral or accessory part of the muscle.

The bundles are thick, and dark red, and are not interrupted
at the temporal side.

A strong bundle of muscle-fibres are given off from the bone
at the inner end of the lid-band, which passes almost in a
straight line toward the canine fossa. For some distance up-
ward fibres are given off from the bone along the posterior
surface of the muscle, and therefore it becomes thicker from
before backward than from side to side.

On its outer border there is a wrinkle or furrow, which is
bounded on the other side by the portio anterior and the portio



160 THE ANATOMY AND HISTOLOGY

orbitalis, as the tense connective tissue which covers the lid-
band portion on the lachrymal sac ascends in the furrow, and
by lateral extensions is fixed to the bone.

The vena and arteria angularis, which come from the canine
fossa, lie in this furrow. In front of the infra-orbital foramen
the band of muscle attached to the skin of the cheek by numer-
ous bands of connective tissue, turns outward, and then bends
suddenly upward and outward toward the malar bone, where
it is attached to the orbital portion. In front of the canine
fossa some thin bundles are attached to the skin. Sometimes
a bundle is given off to the angle of the mouth. The ascending
branch, after passing a line formed by the extension of the
palpebral fissure to the temple, passes into pencils of extending
fibres, which are lost in the aponeurosis of the frontal muscle.
Downward some of the bundles are lost in the temporal aponeu-
rosis. The rest of the fibres pass above the projecting orbital
border inward, and pass to the musculus corrugata superciliorum.
Above the lid-band a flat, muscular layer arises, about 3 /r/ to
4'" broad at its origin. It arises from the bone above the
tear sac. It has a dark color, and ascends toward the super-
ciliary arch, and becomes broader as it approaches it. From
the lid-band it is covered by a fascia of connective tissue,
which attaches it to the skin, and by its lateral extensions it
is fixed t6 the bones. The iibres of this muscle are lost in the
inner half of the eyebrow. This flat muscle forms a triangle,
its base being in the eyebrow, and its apex at the upper sur-
face of the lid-band. This flat muscle may be named the
abductor of the eyebrows.

Beneath it are found first the beginning of the orbital por-
tion, more toward the nose and upward, the corrugator super-
cilii, which is covered with a somewhat thick aponeurosis, the
fibres of which, below the superciliary arch, run obliquely
outward more than upward, and has connections with the
beginning of the frontal muscle, as well as with the peripheral
fibres of the orbicularis coming from the temple.

The orbicularis extends an inch outward and upward. Of



OF THE HUMAN EYE. 161

this two-thirds are included in the lachrymal and lid-band
portions. Only these portions present the peculiarities to he
named. If a line be extended in the direction of the palpebral
fissure of the closed lids, outward from the outer canthus l ff/
to 8 f " on the malar bone, we shall find that from the angle of
the lids to the end of this line the cuticle is thin, without a
fatty cushion, and is fastened to the muscle by a connective
tissue so short that it is difficult to separate them. Below this
line the muscle bundles are thick, and above it they are un-
usually thin. The fibres of the upper and lower halves ap-
proach this line seemingly as if they approached each other
at acute angles ; but, in front at least, no angles are seen, but
bows, or curves of fibres that pass over from one half to the
other. The nearer these bows (of fibres) approach the palpe-
bral fissure, the more they curve, and the further they are
from it the more flat they are. Within the extent of this
line the muscle is also more firmly connected to the firm con-
nective tissue than in surrounding regions. From V' to 8'"
outward from the external canthus, there is some fatty tissue
lying on the muscular fibres, as well as beneath them. Near
the line named it is observed that the muscular bundles split,
yet it is seen that in its whole extent fibres pass uninterrupt-
edly from the lower to the upper half; but this takes place
more freely toward the temple than further inward. Still, it
is observed that many fibres here cease by insertion into the
firm connective tissue beneath.

The peripheral muscular fibre-bundles have nothing to do
with the closing of the eyelids, but are called into action during
winking, laughing, or crying. It will be perceived from the
above, that Arlt gives more points of attachment for this mus-
cle than anatomists have done heretofore. These he calls the
external points of fixed attachment, such as a bundle going to
the angle of the mouth, another to the temple, and another to
the epicranial aponeurosis, with many of its fibres uniting with
the frontal and superciliary muscles.

The external angle of the eye is placed 2'" to 3'" higher

11



162 THE ANATOMY AND HISTOLOGY

than the internal fixed point of the lids. During blinking, or
gentle closure of the lids, the extremity of the external angle
of the lids descends to a horizontal line with the point of re-
union with the internal angle, which is situated near the middle
of the palpebral fissure. During blinking, or closure of the lids,
the upper lid moves in a vertical direction ; the middle of the
lid descends until the internal and external fixed points of the
lids are found in a straight line. The lower lid, on the con-
trary, moves laterally. Whilst the external angle descends,
the internal part of the lid, especially the lachrymal point, is
drawn inward, backward, and upward. The middle of the
border of the lower lid is not displaced upward, and only un-
dergoes a slight inward movement. The two lids, during
blinking, or closure of the lids, make also a slight inward
movement. In the blinking, to save the eye from too great
a light, the peripheral fascicule narrows the arch which it
forms, and the internal portion raises the lower lid, and at
the same time carries it inward. By this action the palpe-
bral fissure is narrowed from the side of the nose.

During laughing the skin is wrinkled toward a line which
runs between the external fixed point of the muscle {!'" to 8'"
outward from the external canthus, described above) and the
external angle of the lids. The narrowing of the palpebral
fissure in this instance takes place by the lower lid being
raised toward the external angle of the lids. In crying, the
lower lid is wholly raised, but the upper lid also descends. In
these movements, as well as those that take place in laughing,
the palpebral fissure is somewhat shortened.

The action of the lachrymal portion of this muscle (Homer's
muscle) will be given in connection with the lachrymal appa-
ratus.

The cilice or eyelashes are located on the outer edge of the
free border of the lids, and very seldom consist of a single
row, but mostly two or three rows exist, one close behind the
other. In the upper they are more abundant and larger, and
ape curved downward and outward ; in the lower lid they are



OF THE HUMAN EYE. 163

less numerous, smaller, and are curved upward and outward.
They are short thin hairs, and differ from other hair in being
thickest at the lower part of the shaft, from which point they
taper to a point both ways.

In their general structure the cilia are similar to other hair,
and they do not demand a full description. The hair-follicles
are lj /r/ in length, and frequently reach into the subcutaneous
cellular tissue, and are attached between the ciliary border of
the tarsi, and the innermost fibres of the portio lacrymalis of
the orbicular muscle.

Close to the hair-follicles some sebaceous glands are located,
generally two in number, which open into it. These glands
measure about 0'".06 to 0'".24 (I, Fig. 64).

NQSLY the cilia are numerous small hairs (m, Fig. 64), the fol-
licles of which are also furnished with beautifully developed
sebaceous glands. The eyelashes are subject to a continual
change. They reach their normal length in about 150 days
(Stellwag), when their bulb is loosened (7, Fig. 64), whilst on
the papilla a new hair is developed, which carries the old in
front with it, to be removed by rubbing or washing.

The arteries of the integument of the lids, the orbicular
muscle, and the tarsal cartilages (in which each Meibomian
gland has its own vascular apparatus) have their origin from
the arteria ophthalmica (<?, Fig. 70), which, after giving off the
arteria dorsalis nasi (/, Fig. 70), and the arteria frontalis (g),
divides at the inner angle of the eye into two branches, the
arteria palpebralis superior and the arteria palpebralis inferior.
These branches, after sending twigs to the lachrymal sac, the
caruncula, and the conjunctiva palpebrarum, penetrate each
one its lid, and run between the tarsi and the sphincter mus-
cle, at least a line from the free border of the lid, outward, and
form numerous anastomoses with the vessels around the eye-
lids.

The palpebralis superior (r, Fig. 70) anastomoses with the
arteria temporalis superficialis (which is a branch of the arteria
temporalis from the carofis externa) (c, Fig. 70), and with the



164



THE ANATOMY AND HISTOLOGY



arteria supra-orbitaria (a branch of the arteria ophthalmica).
The inferior palpebral artery anastomoses with the arteria
transversa faciei (6), a branch of the arteria temporalis, with
the arteria palpebral is externa ({) from the lachrymal artery,
which is a branch of the ophthalmic, and with the arteria
infra-orbitalis (a), a branch of the internal maxillary artery.
The largest of the branches of the palpebral arteries is the
ramus tarseus seu marginalis, which runs along near the
margin of the lid, still in front of the tarsus, and forms, in
the upper lid, with a branch of the arteria temporalis super-
ficiales anterior, and in the lower lid, with a branch of the
arteria lacrymalis and transversa faciei, a vascular bow paral-
lel with the palpebral fissure, called the arcus tarsus superior
and inferior (/:, &, Fig. 70).



FIG. 70.




a. Infra-orbital artery. b. Transverse facial artery, (a). Their anastomoses, c,
Anterior superficial temporal artery, d. Supra-orbital artery, e. Ophthalmic artery.
f. Arteria dorsalis narium. g. Frontal artery, k. Internal palpebral artery. Ic. Arcus
palpebralis superior et inferior, i. External palpebral arteries from the lachrymal ar-
tery. /. Lower muscle of the nose. m. Ligamentum palpebralis internum. n, o. Upper
and lower lachrymal canals, p, q. Orbital portion of the lacrhymal sac. p. Fundus of


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Online LibraryAbraham MetzThe anatomy and histology of the human eye → online text (page 12 of 14)