1. The orbitThe orbit

2. The orbitThe orbit is a pyramidal, bony cavity in
the facial skeleton with its base anterior
and its apex posterior
• The orbits contain and protect the eyeballs
and their muscles, nerves, and vessels,
together with most of the lacrimal
apparatus.
• The bones forming the orbit are lined with
periorbita (periosteum of the orbit), which
forms the fascial sheath of the eyeball

3. • The periorbita is continuous at the optic
canal and superior orbital fissure with the
periosteal layer of dura
• The periorbital is also continuous over the
orbital margins and through the inferior
orbital fissure with the periosteum covering
the external surface of the skull
(pericranium).

4. The orbit has four walls and an
apex
• The superior wallThe superior wall (roof) is approximately(roof) is approximately
horizontal and is formed mainly by the orbitalhorizontal and is formed mainly by the orbital
part of the frontal bone, which separates thepart of the frontal bone, which separates the
orbital cavity from the anterior cranial fossa.orbital cavity from the anterior cranial fossa.
Near the apex of the orbit, the superior wall isNear the apex of the orbit, the superior wall is
formed by the lesser wing of the sphenoidformed by the lesser wing of the sphenoid
• The lacrimal gland occupies the fossa for theThe lacrimal gland occupies the fossa for the
lacrimal gland (lacrimal fossa) in the orbitallacrimal gland (lacrimal fossa) in the orbital
part of the frontal bone.part of the frontal bone.

5. • The medial wall is formed primarily by the
ethemoid bone, along with contributions
from the frontal, lacrimal, and sphenoid
bones; anteriorly,
• the paper-thin medial wall is
indented by a lacrimal fossa for the
lacrimal sac and the proximal part of the
nasolacrimal duct. The medial walls of the
two orbits are essentially parallel,
separated by the ethmoidal sinuses and
the unpper nasal cavity.

6. • The inferior wall(floorThe inferior wall(floor) is formed mainly by the
maxilla and partly by the zygomatic and palatine
bones;
• the thin floorthe thin floor is partly separated from the lateral
wall of the orbit by the inferior orbital fissure.
• The lateral wallThe lateral wall is formed by the frontal
process of the zygomatic bone and the greater
wing of the sphenoid; the lateral wall is thick,
especially its posterior part, which separates the
orbit from the middle cranial fossa. The lateral
walls of the two orbits are nearly perpendicular
to each other.

7. • The,apex of the orbit is at the
optic canal, in the lesser wing of
the sphenoid just medial to the
superior orbital fissure.

9. Orbital Contents
The contents of the orbit are :-
• the eyeballthe eyeball
• optic nerveoptic nerve
• ocular musclesocular muscles
• fasciafascia
• nervesnerves
• vesselsvessels
• fatfat
• lacrimal glandlacrimal gland
• and conjunctival sacand conjunctival sac.

10. Muscles of the Orbit
• Levator palpebrae superioris
• Four recti (superior, inferior, medial, and
lateral)
• Two oblique (superior and inferior).

12. Levator Palpebrae Superioris
• This thin, flat elevator muscle of the
superior eyelid broadens into a wide
aponeurosis as it approaches its distal
attachment to the tarsal plate. This muscle
is the opponent of the orbicularis oculi, the
sphincter of the palpebral fissure.

14. Levator
Palpebrae
Superioris
•Tarsal gland
•Palpebral surface
•Posterior margin
•Anterior margin

15. Recti and Oblique Muscles
• The four recti arise from a fibrous cuff, the
common tendinous ring, that surrounds
the optic canal and part of the superior
orbital fissure.
• The lateral and medial recti lie in the same
horizontal plane, and the superior and
inferior recti lie in the same vertical plane.
All four recti mus­cles attach to the sclera
on the anterior half of the eyebal

17. • All four recti muscles attach to the sclera
on the anterior half of the eyeball.

18. • • Medial and lateral recti rotate the pupil
medially and laterally, respectively
• • Superior rectus rotates the pupil superiorly
(elevation)
• • Inferior rectus rotates the pupil inferiorly
(depression).
• The inferior oblique directs the pupil laterally
and superiorly; therefore, when it works
synergistically with the superior rectus, superior
movement of the eyeball occurs. Similarly, the
superior oblique directs the pupil inferiorly and
laterally; therefore, when it works synergistically
with the inferior rectus, an inferior movement
results.

22. Tendinous ring

23. Upper part of the tendinous ring
• Lacrimal nerve
• Frontal nerve
• Trochlear nerve
• Superior ophthalmic vein

24. Middle part of the tendinous ring
• Oculomotore nerve with it’s both divisions
• Abducent nerve
• Nasociliary nerve
Lower part transmits only the inferior
ophthalmic vein
All recti muscles orginated from the ring

27. Orbital Contents
• The contents of the orbit are the eyeball,
optic nerve, ocular muscles, fascia,
nerves, vessels, fat, lacrimal gland, and
conjunctival sac.

29. 1-Orbicularis oculi
2

30. Nerves of the Orbit
• Optic Nerve
• The optic nerve enters the orbit from the
middle cranial fossa by passing through
the optic canal
• It is accompanied by the ophthalmic
artery, which lies on its lower lateral side.
• The nerve is surrounded by sheaths of pia
mater, arachnoid mater, and dura mater
().

31. Nerves of the Orbit
• It runs forward and laterally within the cone of
the recti muscles and pierces the sclera at a
point medial to the posterior pole of the eyeball.
• Here, the meninges fuse with the sclera so that
the subarachnoid space with its contained
cerebrospinal fluid extends forward from the
middle cranial fossa, around the optic nerve, and
through the optic canal, as far as the eyeball.
• A rise in pressure of the cerebrospinal fluid
within the cranial cavity therefore is transmitted
to the back of the eyeball.
•

32. Nerves of the Orbit
• Lacrimal Nerve
• The lacrimal nerve arises from the ophthalmic division of
the trigeminal nerve.
• It enters the orbit through the upper part of the superior
orbital fissure (
• ) and passes forward along the upper border of the
lateral rectus muscle
• . It is joined by a branch of the zygomaticotemporal
nerve, which later leaves it to enter the lacrimal gland
(parasympathetic secretomotor fibers).
• The lacrimal nerve ends by supplying the skin of the
lateral part of the upper lid.

34. Frontal Nerve
• The frontal nerve arises from the ophthalmic division of
the trigeminal nerve.
• It enters the orbit through the upper part of the superior
orbital fissure
• passes forward on the upper surface of the levator
palpebrae superioris beneath the roof of the orbit
• It divides into the supratrochlear and supraorbital nerves
that wind around the upper margin of the orbital cavity to
supply the skin of the forehead;
• the supraorbital nerve also supplies the mucous
membrane of the frontal air sinus.

35. Trochlear Nerve
• The trochlear nerve enters the orbit
through the upper part of the superior
orbital fissure
• It runs forward and supplies the superior
oblique muscle

36. Oculomotor Nerve
• The superior ramus of the oculomotor nerve enters the
orbit through the lower part of the superior orbital fissure
• . It supplies the superior rectus muscle, then pierces it,
and supplies the levator palpebrae superioris muscle (
• The inferior ramus of the oculomotor nerve enters the
orbit in a similar manner and supplies the inferior rectus,
the medial rectus, and the inferior oblique muscles.
• The nerve to the inferior oblique gives off a branch that
passes to the ciliary ganglion and carries
parasympathetic fibers to the sphincter pupillae and the
ciliary muscle

37. Nasociliary Nerve
• The nasociliary nerve arises from the
ophthalmic division of the trigeminal nerve.
• It enters the orbit through the lower part of
the superior orbital fissure (
• . It crosses above the optic nerve, runs
forward along the upper margin of the
medial rectus muscle, and ends by
dividing into the anterior ethmoidal and
infratrochlear nerves

38. Branches of the Nasociliary Nerve
• The communicating branch to the ciliary ganglion is a
sensory nerve. The sensory fibers from the eyeball pass
to the ciliary ganglion via the short ciliary nerves, pass
through the ganglion without interruption, and then join
the nasociliary nerve by means of the communicating
branch.
• The long ciliary nerves, two or three in number, arise
from the nasociliary nerve as it crosses the optic nerve
(They contain sympathetic fibers for the dilator pupillae
muscle. The nerves pass forward with the short ciliary
nerves and pierce the sclera of the eyeball.
• They continue forward between the sclera and the
choroid to reach the iris.

39. Branches of the Nasociliary Nerve
• The posterior ethmoidal nerve supplies the
ethmoidal and sphenoidal air sinuses (.

40. Branches of the Nasociliary Nerve
• The infratrochlear nerve passes forward below the pulley
of the superior oblique muscle and supplies the skin of
the medial part of the upper eyelid and the adjacent part
of the nose
• The anterior ethmoidal nerve passes through the anterior
ethmoidal foramen and enters the anterior cranial fossa
on the upper surface of the cribriform plate of the
ethmoid (
• It enters the nasal cavity through a slit like opening
alongside the crista galli. After supplying an area of
mucous membrane, it appears on the face as the
external nasal branch at the lower border of the nasal
bone, and supplies the skin of the nose down as far as
the tip

41. Abducent Nerve
• The abducent nerve enters the orbit
through the lower part of the superior
orbital fissure (
• . It supplies the lateral rectus muscle.

42. Ciliary Ganglion
• The ciliary ganglion is a parasympathetic ganglion about
the size of a pinhead
• and situated in the posterior part of the orbit.
• It receives its preganglionic parasympathetic fibers from
the oculomotor nerve via the nerve to the inferior
oblique.
• The postganglionic fibers leave the ganglion in the short
ciliary nerves, which enter the back of the eyeball and
supply the sphincter pupillae and the ciliary muscle.
• A number of sympathetic fibers pass from the internal
carotid plexus into the orbit and run through the ganglion
without interruption

43. Blood Vessels and Lymph Vessels
of the Orbit
• Ophthalmic Artery
• The ophthalmic artery is a branch of the internal carotid artery after
that vessel emerges from the cavernous sinus
• It enters the orbit through the optic canal with the optic nerve
• . It runs forward and crosses the optic nerve to reach the medial wall
of the orbit.
• It gives off numerous branches, which accompany the nerves in the
orbital cavity.
• Branches of the Ophthalmic Artery
• The central artery of the retina is a small branch that pierces the
meningeal sheaths of the optic nerve to gain entrance to the nerve (
• It runs in the substance of the optic nerve and enters the eyeball at
the center of the optic disc. Here,
• it divides into branches, which may be studied in a patient through
an ophthalmoscope. The branches are end arteries.

44. Blood Vessels and Lymph Vessels
of the Orbit
•The muscular branches
•The ciliary arteries can be divided into anterior
and posterior groups. The former group enters
the eyeball near the corneoscleral junction; the
latter group enters near the optic nerve.
•The lacrimal artery to the lacrimal gland
•The supratrochlear and supraorbital arteries are
distributed to the skin of the forehead (see page
729).

45. Ophthalmic Veins
• The superior ophthalmic vein communicates in
front with the facial vein
• The inferior ophthalmic vein communicates
through the inferior orbital fissure with the
pterygoid venous plexus. Both veins pass
backward through the superior orbital fissure
and drain into the cavernous sinus.
• Lymph Vessels
• No lymph vessels or nodes are present in the
orbital cavity

47. Intrinsic Muscles
• The involuntary intrinsic muscles are the
ciliary muscle and the constrictor, and the
dilator pupillae of the iris take no part in
the movement of the eyeball and are
discussed later.

48. Intrinsic Muscles
Fascial Sheath of the Eyeball
• The fascial sheath surrounds the eyeball from the optic nerve to the
corneoscleral junction (
• It separates the eyeball from the orbital fat and provides it with a
socket for free movement.
• It is perforated by the tendons of the orbital muscles and is reflected
onto each of them as a tubular sheath.
• The sheaths for the tendons of the medial and lateral recti are
attached to the medial and lateral walls of the orbit by triangular
ligaments called the medial and lateral check ligaments.
• The lower part of the fascial sheath, which passes beneath the
eyeball and connects the check ligaments, is thickened and serves
to suspend the eyeball; it is called the suspensory ligament of the
eye
. By this means the eye is suspended from the medial and lateral walls
of the orbit, as if in a hammock.

49. Structure of the Eye
• The eyeball (
• is embedded in orbital fat but is separated
from it by the fascial sheath of the eyeball.

50. The eyeball
• consists of three coats, which, from
without inward,
• the fibrous coat,
• the vascular pigmented coat,
• the nervous coat.

51. The eyeball has three layers
• The outer fibrous layer — the sclera and
cornea
• The middle vascular (pigmented) layer —
the choroid, ciliary body, and iris
• The inner layer — the retina, consisting
of optic and nonvisual parts.

52. cornea
lence

53. Coats of the Eyeball
• Fibrous Coat
• The fibrous coat is made up of a posterior opaque part,
the sclera, and an anterior transparent part, the cornea
• The Sclera
• The opaque sclera is composed of dense fibrous tissue
and is white. Posteriorly, it is pierced by the optic nerve
and is fused with the dural sheath of that nerve
• . The lamina cribrosa is the area of the sclera that is
pierced by the nerve fibers of the optic nerve.

54. Coats of the Eyeball
• The sclera is also pierced by the ciliary arteries
and nerves and their associated veins, the
venae vorticosae.
• The sclera is directly continuous in front with the
cornea at the corneoscleral junction, or limbus.
•
The Cornea
• The transparent cornea is largely responsible for
the refraction of the light entering the eye (
• It is in contact posteriorly with the aqueous
humor.

55. Vascular Pigmented Coat
• The vascular pigmented coat consists,
from behind forward, of
• the choroid,
• the ciliary body, and
• the iris.

56. Vascular Pigmented Coat
• The Choroid
• The choroid is composed of an outer pigmented
layer and an inner, highly vascular layer.
• The Ciliary Body
• The ciliary body is continuous posteriorly with
the choroid, and anteriorly it lies behind the
peripheral margin of the iris
• It is composed of the
• ciliary ring,
• the ciliary processes, and
• the ciliary muscle.

57. Vascular Pigmented Coat
• The ciliary ring is the posterior part of the body, and its
surface has shallow grooves, the ciliary striae.
• The ciliary processes are radially arranged folds, or
ridges, to the posterior surfaces of which are connected
the suspensory ligaments of the lens.
• The ciliary muscle . is composed of meridianal and
circular fibers of smooth muscle. The meridianal fibers
run backward from the region of the corneoscleral
junction to the ciliary processes.
• The circular fibers are fewer in number and lie internal to
the meridianal fibers.

58. Vascular Pigmented Coat
• Nerve supply:
• The ciliary muscle is supplied by the parasympathetic
fibers from the oculomotor nerve. After synapsing in the
ciliary ganglion, the postganglionic fibers pass forward to
the eyeball in the short ciliary nerves.
• Action: Contraction of the ciliary muscle, especially the
meridianal fibers, pulls the ciliary body forward.
• This relieves the tension in the suspensory ligament, and
the elastic lens becomes more convex. This increases
the refractive power of the lens.

59. Outer Fibrous Layer of the
Eyeball
• The sclera is the opaque part of the fibrous coat
of the eyeball covering the posterior 5/6 of the
eyeball.
• The anterior part of the sclera is visible through
the transparent bulbar conjunctiva as "the white
of the eye."
• The cornea is the transparent part of the fibrous
coat covering the anterior one-sixth of the
eyeball.

61. Nervous Coat: The Retina
• The retina consists of an outer pigmented layer and an
inner nervous layer
• . Its outer surface is in contact with the choroid, and its
inner surface is in contact with the vitreous body
• The posterior three fourths of the retina is the receptor
organ.
• Its anterior edge forms a wavy ring, the ora serrata, and
the nervous tissues end here.
• The anterior part of the retina is nonreceptive and
consists merely of pigment cells, with a deeper layer of
columnar epithelium. This anterior part of the retina
covers the ciliary processes and the back of the iris.

62. Nervous Coat: The Retina
• At the center of the posterior part of the retina is an oval, yellowish
area, the macula lutea, which is the area of the retina for the most
distinct vision. It has a central depression, the fovea centralis (
• The optic nerve leaves the retina about 3 mm to the medial side of
the macula lutea by the optic disc.
• The optic disc is slightly depressed at its center, where it is pierced
by the central artery of the retina.
• At the optic disc is a complete absence of rods and cones so that it
is insensitive to light and is referred to as the blind spot.
• ‌ On ophthalmoscopic examination, the optic disc is seen to be pale
pink in color, much paler than the surrounding retina.

63. Nervous Coat: The Retina
Contents of the Eyeball
• The contents of the eyeball consist of the
• refractive media,
• the aqueous humor,
• the vitreous body, and
• the lens.
• Aqueous Humor

64. Nervous Coat: The Retina
Contents of the Eyeball
• The aqueous humor is a clear fluid that fills the
anterior and posterior chambers of the eyeball
• . It is believed to be a secretion from the ciliary
processes, from which it enters the posterior
chamber. It then flows into the anterior chamber
through the pupil and is drained away through
the spaces at the iridocorneal angle into the
canal of Schlemm.

65. Nervous Coat: The Retina
Contents of the Eyeball
• Obstruction to the draining of the aqueous
humor results in a rise in intraocular pressure
called glaucoma
• . This can produce degenerative changes in the
retina, with consequent blindness.
• The function of the aqueous humor is to support
the wall of the eyeball by exerting internal
pressure and thus maintaining its optical shape.
It also nourishes the cornea and the lens and
removes the products of metabolism; these
functions are important because the cornea and
the lens do not possess a blood supply.

67. Vitreous Body
• The vitreous body fills the eyeball behind the lens (
• ) and is a transparent gel.
• The hyaloid canal is a narrow channel that runs through
the vitreous body from the optic disc to the posterior
surface of the lens; in the fetus, it is filled by the hyaloid
artery, which disappears before birth.
• The function of the vitreous body is to contribute slightly
to the magnifying power of the eye. It supports the
posterior surface of the lens and assists in holding the
neural part of the retina against the pigmented part of the
retina.

68. Vitreous Body
The Lens
• The lens is a transparent, biconvex
structure enclosed in a transparent
capsule.
• It is situated behind the iris and in front of
the vitreous body and is encircled by the
ciliary processes.

69. Vitreous Body
The Lens
• The lens consists of an elastic capsule,
which envelops the structure; a cuboidal
epithelium, which is confined to the
anterior surface of the lens; and lens
fibers, which are formed from the cuboidal
epithelium at the equator of the lens.
• The lens fibers make up the bulk of the
lens.

70. Vitreous Body
The Lens
• The elastic lens capsule is under tension,
causing the lens constantly to endeavor to
assume a globular rather than a disc shape.
• The equatorial region, or circumference, of the
lens is attached to the ciliary processes of the
ciliary body by the suspensory ligament.
• The pull of the radiating fibers of the suspensory
ligament tends to keep the elastic lens flattened
so that the eye can be focused on distant
objects.

71. •The end

72. Middle Vascular Layer of the
Eyeball
• The chroid a dark brown membrane between
the sclera and retina — forms the largest part
of the vascular layer of the
• Eyeball and lines most of the sclera.
• It terminates anteriorly in the ciliary body.
• The choroid attaches firmly to the pigment
layer of the retina, but it can easily be stripped
from the sclera.

73. The ciliary body which is muscular as well as
vascular —
connects the choroid with the circumference of the
iris
• . Folds on its internal surface — the ciliary
processes
• secrete aqueous humor, which fills the
anterior and posterior chambers

75. • The anterior chamber of the eye is the
space between the cornea anteriorly and
the iris/pupil posteriorly,
• The posterior chamber of the eye is
between the iris/pupil anteriorly and the
lens and ciliary body posteriorly

77. • The iris which literally lies on the anterior
surface of the anterior surface of the lens, is
a thin, contractile diaphragm with a central
aperture the pupil for transmitting light. When
a person is awake, the size of the pupil varies
continually to regulate the amount of light
entering the eye.
• Two muscles control the size of the pupil: the
sphincter pupillae closes the pupil and the
dilator pupillae opens it.

78. Inner Layer of the Eyeball
(Retina(
• Grossly, the retina consists of three parts:
• Optic part
• Ciliary part
• Iridial part.

80. The optic part of the retina
• which receives the visual light rays.
• has two layers: a neural layer and pegmented cell
layer.
• The neural layer is the light-receptive part.
• The pigmented layer consists of a single layer of cells
that reinforces the light-absorbing property of the
choroid in reducing the scattering of light in the eye.
• The ciliary and iridial parts of the retina are anterior
continuations of the pigmented layer and a layer of
supporting cells over the ciliary body and the
posterior surface of the iris, respectively.

81. • In the fundus (posterior part) of the eye is
a circular depressed area—the optic disc
(optic papilla)—where the optic nerve
enters the eyeball. Because it contains
nerve fibers and no photoreceptors, the
optic disc is insensitive to light. Just lateral
to this "blind spot" of the retina is the
macula lutea (L. yellow spot).

82. • The yellow color of the macula is apparent only when the
retina is examined with red-free light. The macula lutea—
a small oval area of the retina with special photoreceptor
cones—is specialized for acuity of vision; it is not
normally observed with an ophthalmoscope,( a device for
viewing the interior of the eyeball through the pupil). At
the center of the macula lutea is a depression—the
fovea centralis (L. central pit)—the area of most acute
vision. The fovea is ap-proximately 1.5 mm in diameter;
its center—the foveola— does not have the capillary
network visible elsewhere deep to the retina.

83. • The functional optic part of the retina
terminates anteriorly along the ora serrata
(L. serrated edge), an irregular border
slightly posterior to the ciliary body. The
ora serrata marks the anterior termination
of the part of the retina
light-receptive

84. • the retina is supplied by the central artery
of the retina, *a branch of the ophthalmic
artery. The cones and rods of the outer
neural layer receive nutrients from the
choriocapillaris,
• A corresponding system of retinal veins
units to form the central vein of the
retina.

85. Refractive Media of the Eye
• On their way to the retina, light waves pass
through the re­fractive media of the eye: cornea,
aqueous humor, lens, and vitreous humor,
• The cornea is the circular area of the anterior
part of the outer fibrous layer of the eyeball; it is
largely responsible for refraction of the light that
enters the eye. It is transparent, avascular, and
sensitive to touch. The cornea is supplied by the
ophthalmic nerve and is nourished by aqueous
humor, tears, and oxygen absorbed from the air

86. • The aqueous humor in the anterior and
posterior chambers of the eye is produced
by the ciliary processes. This clear watery
solution provides nutrients for the
avascular cornea and lens. After passing
through the pupil from the posterior
chamber into the anterior chamber, the
aqueous humor drains into the scleral
venous sinus (L. sinus venosus sclerae,
canal of Schlemm) at the iridocorneal
angle.

87. • The lens, posterior to the iris and anterior to
the vitreous humor of the vitreous body, is a
transparent biconvex structure enclosed in a
capsule. The lens capsule is anchored by the
suspensory ligament of the lens to the ciliary
body and encir-cled by the ciliary processes.
The convexity of the lens, particularly its
anterior surface, constantly varies to focus
near or distant objects on the retina. The
ciliary muscle in the ciliary body changes the
shape of the lens; in this way the isolated
unattached lens assumes a nearly spherical
shape.

88. • Stretched within the circle of the relaxed ciliary
body, the at­tachments around its periphery
pull the lens relatively flat so that its refraction
enables far vision. When parasympathetic
stimulation causes the smooth muscle of the
circular ciliary body to contract, the circle—like
a sphincter—becomes smaller in size and the
tension on the lens is reduced, allowing the
lens to round up. The increased convexity
makes its refraction suitable for near vision. In
the absence of parasympathetic stimulation,
the ciliary muscles relax again and the lens is
pulled into its flatter, far vision shape

89. • The vitreous humor is a watery fluid
enclosed in the meshes of the vitreous
body, a transparent jellylike substance in
the posterior four­fifths of the eyeball
posterior to the lens (postremal or vitreous
chamber, or posterior segment). In ad­
dition to transmitting light, the vitreous
humor holds the retina in place and
supports the lens.

90. Innervation of the Orbit
• In addition to the optic nerve, the nerves of the
orbit include those that enter through the
superior orbital fissure and supply the ocular
muscles: oculomotor III, trochlear, IV; and
abducent, VI
• • CN III supplies the levator palpebrae
superioris, superior rectus, medial rectus,
inferior rectus, and inferior oblique.
• • CN IV supplies the superior oblique.
• • CN VI supplies the lateral rectus.

92. Several branches of the ophthalmic nerve (CN
Vi) pass through the superior orbital fissure and
supply structures in the orbit.
• The lacrimal nerve arises in the lateral
wall of the cavernous sinus and passes to
the lacrimal gland, giving branches to the
conjunctiva and skin of the superior eyelid
and providing secretomotor fibers
conveyed to it from the zygomatic nerve
(CN V2

93. • The frontal nerve divides into the
supraorbital nerve and supratrochlear
nerve, which supply the upper eyelid,
forehead, and scalp.
• The nasociliary nerve, the sensory nerve
to the eye, supplies several branches to
the orbit­

94. • The infratrochlear nerve, a terminal
branch of the nasociliary nerve, supplies
the eyelids, conjunctiva, skin of the nose,
and lacrimal sac
• The ethmoidal nerves, also branches of
the nasociliary nerve, supply the mucous
membrane of the sphenoidal and
ethmoidal sinuses and the nasal cavities,
and the dura of the anterior cranial fossa.

95. • The short ciliary nerves, branches of the ciliary
ganglion , carry parasympathetic and
sympathetic fibers to the ciliary body and iris.
• . The ciliary ganglion is a small group of nerve
cell bodies between the optic nerve and lateral
rectus toward the posterior limit of the orbit. The
short ciliary nerves consist of postsynaptic
parasympathetic fibers origi­nating in the ciliary
ganglion, afferent fibers from the nasocil­iary
nerve that pass through the ganglion, and
postsynaptic sympathetic fibers that also pass
through it. The long ciliary nerves, branches of
the nasociliary nerve (CN Vi), transmit
postsynaptic sympathetic fibers to the dilator
pupillae and af­ferent fibers from the iris and
cornea.

96. Vasculature of the Orbit
Arteries of the Orbit
• The blood supply of the orbit is mainly from the ophthalmic artery;
• the infraorbital artery also contributes blood to this region
• The central artery of the retina, a branch of the ophthalmic artery inferior to the
optic nerve, runs within the dural sheath of the optic nerve until it approaches the
eyeball.
• The central artery pierces the optic nerve and runs within it to emerge at the optic
disc.
• Branches of the central artery spread over the internal surface of the retina.
• The terminal branches of the central artery are end arteries that provide the only
blood supply to the retina.
• The retina is also supplied by the capillary layer of the choroid the choriocapillary
layer (lamina). Of the eight or so posterior ciliary arteries—also branches of the
ophthalmic artery—six short posterior ciliary arteries directly supply the choroid,
which nourishes the outer nonvascuiar layer of the retina. Two long posterior
ciliary arteries, one on each side of the eyeball, pass between the sclera and
choroid to anastomose with the anterior ciliary arteries—continuations of the
muscular branches of the ophthalmic artery— supplying the ciliary plexus.

97. Veins of the Orbit
• Venous drainage of the orbit is through the superior and
inferior ophthalmic veins that pass through the superior
orbital fissure and enter the cavernous sinus.
• The central vein of the retina. usually enters the
cavernous sinous directly, but it may join one of the
ophthalmic veins.
• The vortex or vorticose veins from the vascular layer
drain into lie inferior ophthalmic vein.
• The scleral venous sinus is a vascular structure
encircling the anterior chamber of the eye through which
the aqueous humor is returned to the blood circulation.

98. Lacrimal Apparatus
• The lacrimal apparatus consists of:
• • Lacrimal glands, which secrete
lacrimal fluid
• • Lacrimal ducts, which convey
lacrimal fluid from the lacrimal glands
to the conjunctiva! sac
• • Lacrimal canaliculi (L. small canals),
each commencing at a lacrimal
punctum (opening) on the lacrimal
papilla near the medial angle of the
eye, which conveys the lacrimal fluid
from the lacrimal lake—a triangular
space at the me­dial angle of the eye
where the tears collect—in the lacrimal
sac, the dilated superior part of the
nasolacrimal duct

107. Lacrimal Apparatus

108. Temporal Region
• The temporal region includes the temporal
and infratemporal fossae—superior and
inferior to the zygomatic arch, respectively

109. Temporal Fossa
• The temporal fossa, in which the temporal
muscle is located, is bounded:
• Posteriorly and superiorly by the temporal
lines.
• Anteriorly by the frontal and zygomatic
bones
• Laterally by the zygomatic arch
• Inferiorly by the infratemporal crest

111. The floor of the temporal fossa
• formed by parts of the four bones that form the
pterion: frontal, parietal, temporal, and greater
wing of the sphenoid.
• The fan­shaped temporal mus­cle arises from
the floor (i.e., the temporal fossa extending to
the inferior temporal line) and the overlying
temporal fascia.
• which comprises the roof of the temporal fossa

113. This tough fascia covers the
temporal muscle, extending to
• Superior temporal line
• Inferiorly, the fascia splits into two layers
that attached to the superior margine of
the zygomatic arch.
• It tethers the zygomatic arch superiorly.
• When the masseter muscle attached to
the inferior border of the arch contracts,
exerting a strong downward pull the
fascia provides resistance.