Page 159 - My FlipBook

AREOLAR TISSUE, TENDONS, AND MVSCLES. 169
surface the orbital portion is in relation with the frontalis and corrugator
supercilii muscles, their fibres interlacing, and with the supraorbital
vessels and nerves, the lachrvnial sac, the origin of the levator labii
superioris, alseque nasi, and the levator labii superioris muscles ; inter-
nally with the pyramidalis nasi, and externally with the temporal fascia.
The under surface of the palpebral portion of this nuiscle is connected
to the cartilage of the eyelid by fibrous connective tissue.
The Internal lendo-jxi/pebrariim (tendo-occuli) is a small white
fibrous band about two lines in length and one line in breadth. It is
attached to the nasal ])rocess of the superior maxilla in front of the
lachrymal groove, and runs outwardly across the lachrymal sac to the
inner commissure of the eyelids, where it divides into two portions, one
going to each lid. As the tendon crossess the lachrymal sac it gives
off from its under surface a strong aponeurotic lamina which covers the
sac and is attached to the lachrymal bone.
The External Tendo-palpebrarum is much weaker than the internal,
and is attached to the malar bone.
The Tensor Tarsi (Horner's nuiscle) is a thin layer of fibres arising
from the lachrymal crest behind the lachrymal sac. It jiasses forward
and outward, and divides into two fasciculi, which are lost in the con-
centric portion of the orbicularis palpebrarum.
The Corrugator Supercilii is a small, deeply-colored muscle arising
from the inner extremity of the superciliary ridge, passing outward and
upward, its fibres diverging, some extending into the orbicularis and
frontalis nniscles, terminating about the middle of the eyebrow. This
muscle is intimately adherent to the integument.
Relations.—By the inner portion of its upper surface with the orbic-
ularis and frontalis muscles, the outer extremities of its fibres being
inserted into these muscles ; by its under surface with the frontal bone,
the supratrochlear branches of the o])hthalmic nerve and accompanying
vessels.
(The levatores palpebrse will be described with the motor muscles of
the eye.)
Actions.—The orbicular portion of the orbicularis palpebrarum is
wholly under the control of the will. Its upper fibres act by depressing
the eyebrow and drawing down the integument of the forehead, antag-
onizing the frontalis muscle. The lower portion elevates the integu-
ment of the cheek, and both combined wrinkle the skin at the outer and
inner angles of the orbital cavities. The office of this muscle is fully
exerted when the eye is closed with force.
The Palpebral Portion gives the peculiar movement to the eyelids
seen in winking or in sleep. It also draws forward the internal tarsal
ligament and the anterior wall of the lachrymal sac, causing it to open
for the reception of lachrymal fluid.
The ConcentriG or Ciliary Portion closes in the edges of the vela of
the eyes, and draws the cilia or lashes of the respective lids against each
other.
The Corrugator Supercilii muscle draws the skin over the forehead
downward and inward toward the upper part of the nose, causing the
vertical grooves made in frowning.