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The Eye
Dr. Amenah Salman
Department of Histology and Embryology
Objective
•1- Define Fibrous Layer
•2- Description Vascular Layer
•3- Acknowledgment about the Lens
•4- Understand the Vitreous Body
• 5- the importance of Retina
•6- Accessory Structures of the Eye
Eyes
• Eyes are highly developed photosensitive organs for analyzing
the form, intensity, and color of light reflected from objects and
providing the sense of sight.
• Each eye is composed of three concentric tunics or layers:-
• ■ A tough external fibrous layer consisting of the sclera and the
transparent cornea
• ■ A middle vascular layer consisting of the choroid, ciliary body,
and iris
• ■ An inner sensory layer, the retina, which communicates with
the cerebrum through the posterior optic nerve
Fibrous Layer
• Fibrous Layer :- This layer includes two major regions, the
posterior sclera and the anterior cornea, joined at the limbus
• 1- Sclera:-
• The fibrous, external layer of the eyeball protects the more
delicate consists mainly of dense connective tissue, with flat
bundles of type I collagen.
• Tendons of the extraocular muscles which move the eyes insert
into the anterior region of the sclera. Posteriorly the sclera joins
with the epineurium covering the optic nerve. Where it
surrounds the choroid
Fibrous Layer
• 2- cornea :- is transparent and completely avascular
• ■ An external corneal epithelium, which is a stratified squamous
epithelium
• ■ An anterior limiting membrane (Bowman membrane), which is
the basement membrane beneath the corneal epithelium
• ■ The thick stroma to provide maximal transparency and optimal
light refraction
• ■ A posterior limiting membrane (Descemet membrane), which is
the basement membrane of the endothelium
• ■ An inner simple squamous endothelium
Limbus
• Encircling the cornea is the limbus, a transitional area where the
transparent cornea merges with the opaque sclera , Here
Bowman’s membrane ends and the surface epithelium becomes
more stratified as the conjunctiva that covers the anterior part of
the sclera (and lines the eyelids).
• endothelial cells which promote slow, continuous filtration and
movement of aqueous humor from the anterior chamber. This
fluid moves from these channels into the adjacent larger space of
the scleral venous sinus, or canal of Schlemm which encircles the
eye. From this sinus, aqueous humor drains into small blood
vessels (veins) of the sclera
lacrimal glands
• The lacrimal glands produce fluid continuously for the tear film
that moistens and lubricates the cornea and conjunctiva and
supplies O2to the corneal epithelial cells.
• Tear fluid also contains various metabolites, electrolytes, and
proteins of innate immunity such as lysozyme.
• The main lacrimal glands are located in the upper temporal
portion of the orbit and have several lobes, which drain through
individual excretory ducts into the superior fornix, the
conjunctiva-lined recess between the eyelids and the eye
middle vascular layer
• The eye’s more vascular middle layer, known as the
uvea, consists of three parts, from posterior to anterior:
the choroid, the ciliary body, and the iris.
• 1- Choroid
• Located in the posterior two-thirds of the eye, the
choroid consists of loose, well-vascularized connective
tissue and contains numerous melanocytes . These
form a characteristic black layer in the choroid and
prevent light from entering the eye except through the
pupil.
middle vascular layer
• 2- The ciliary body, the anterior expansion of the uvea that encircles
the lens, lies posterior to the limbus Like the choroid, most of the
ciliary body rests on the sclera. Important structures associated with
the ciliary body include the following:■ Ciliary muscle makes up most
of the ciliary body’s stroma and consists of three groups of smooth
muscle fibers. Contraction of these muscles affects the shape of the
lens and is important in visual accommodation.
• aqueous humor is secreted by ciliary processes into the posterior
chamber, flows through the pupil into the anterior chamber, and
drains at the angle formed by the cornea and the iris into the
channels of the trabecular meshwork and the canal of Schlemm.
middle vascular layer
• 3- The iris is the most anterior extension of the middle uveal
layer which covers part of the lens, leaving a round central pupil
The anterior surface of the iris, exposed to aqueous humor in
the anterior chamber, consists of a dense layer of fibroblasts
and melanocytes
• The highly pigmented posterior epithelium of the iris blocks all
light from entering the eye except that passing through the
pupil.
The lens
• The lens is a transparent biconvex structure suspended
immediately behind the iris, which focuses light on the
Retina.
• the lens is a unique avascular tissue and is highly
elastic, a property that normally decreases with age.
• The lens is held in place by fibers of the ciliary zonule,
which extend from the lens capsule to the ciliary body
this structure allows the process of visual
accommodation, which permits focusing on near and far
objects by changing the curvature of the lens.
vitreous body
• The vitreous body occupies the large vitreous chamber
behind the lens It consists of transparent, gel-like
connective tissue that is 99% water (vitreous humor),
with collagen fibrils and hyaluronate, contained within
an external lamina called the vitreous membrane.
• The only cells in the vitreous body are a small
mesenchymal population near the membrane called
hyalocytes, which synthesize the hyaluronate and
collagen, and a few macrophages.
Chambers in the Eye
• The eye also contains three chambers.
• • The anterior chamber is a space located between the cornea,
iris, and lens.
• • The posterior chamber is a small space situated between the
iris, ciliary process, zonular fibers, and lens. The zonular fibers
radiate from the ciliary process and insert into the lens capsule.
This forms the suspensory ligaments of the lens that anchor it in
the eyeball.
• • The vitreous chamber is a larger, posterior space that is
situated behind the lens and zonular fibers and is surrounded by
the retina.
Retina
• The innermost lining of the posterior chamber of the eye
is the retina that is in contact with the highly vascular
choroid. The posterior three quarters of the retina is a
photosensitive region. It consists of rods, cones, and
various interneurons—cells that are stimulated by and
respond to light. The photosensitive part of the retina
terminates in the anterior region of the eye, called the
ora serrata. This nonphotosensitive part of the retina
continues forward in the eye to line the inner part of the
ciliary body and the posterior region of the iris
Thank you

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Histology of the eye by a very good docotor in iraqi uni collage of med

  • 1. The Eye Dr. Amenah Salman Department of Histology and Embryology
  • 2. Objective •1- Define Fibrous Layer •2- Description Vascular Layer •3- Acknowledgment about the Lens •4- Understand the Vitreous Body • 5- the importance of Retina •6- Accessory Structures of the Eye
  • 3. Eyes • Eyes are highly developed photosensitive organs for analyzing the form, intensity, and color of light reflected from objects and providing the sense of sight. • Each eye is composed of three concentric tunics or layers:- • ■ A tough external fibrous layer consisting of the sclera and the transparent cornea • ■ A middle vascular layer consisting of the choroid, ciliary body, and iris • ■ An inner sensory layer, the retina, which communicates with the cerebrum through the posterior optic nerve
  • 4. Fibrous Layer • Fibrous Layer :- This layer includes two major regions, the posterior sclera and the anterior cornea, joined at the limbus • 1- Sclera:- • The fibrous, external layer of the eyeball protects the more delicate consists mainly of dense connective tissue, with flat bundles of type I collagen. • Tendons of the extraocular muscles which move the eyes insert into the anterior region of the sclera. Posteriorly the sclera joins with the epineurium covering the optic nerve. Where it surrounds the choroid
  • 5. Fibrous Layer • 2- cornea :- is transparent and completely avascular • ■ An external corneal epithelium, which is a stratified squamous epithelium • ■ An anterior limiting membrane (Bowman membrane), which is the basement membrane beneath the corneal epithelium • ■ The thick stroma to provide maximal transparency and optimal light refraction • ■ A posterior limiting membrane (Descemet membrane), which is the basement membrane of the endothelium • ■ An inner simple squamous endothelium
  • 6. Limbus • Encircling the cornea is the limbus, a transitional area where the transparent cornea merges with the opaque sclera , Here Bowman’s membrane ends and the surface epithelium becomes more stratified as the conjunctiva that covers the anterior part of the sclera (and lines the eyelids). • endothelial cells which promote slow, continuous filtration and movement of aqueous humor from the anterior chamber. This fluid moves from these channels into the adjacent larger space of the scleral venous sinus, or canal of Schlemm which encircles the eye. From this sinus, aqueous humor drains into small blood vessels (veins) of the sclera
  • 7. lacrimal glands • The lacrimal glands produce fluid continuously for the tear film that moistens and lubricates the cornea and conjunctiva and supplies O2to the corneal epithelial cells. • Tear fluid also contains various metabolites, electrolytes, and proteins of innate immunity such as lysozyme. • The main lacrimal glands are located in the upper temporal portion of the orbit and have several lobes, which drain through individual excretory ducts into the superior fornix, the conjunctiva-lined recess between the eyelids and the eye
  • 8. middle vascular layer • The eye’s more vascular middle layer, known as the uvea, consists of three parts, from posterior to anterior: the choroid, the ciliary body, and the iris. • 1- Choroid • Located in the posterior two-thirds of the eye, the choroid consists of loose, well-vascularized connective tissue and contains numerous melanocytes . These form a characteristic black layer in the choroid and prevent light from entering the eye except through the pupil.
  • 9. middle vascular layer • 2- The ciliary body, the anterior expansion of the uvea that encircles the lens, lies posterior to the limbus Like the choroid, most of the ciliary body rests on the sclera. Important structures associated with the ciliary body include the following:■ Ciliary muscle makes up most of the ciliary body’s stroma and consists of three groups of smooth muscle fibers. Contraction of these muscles affects the shape of the lens and is important in visual accommodation. • aqueous humor is secreted by ciliary processes into the posterior chamber, flows through the pupil into the anterior chamber, and drains at the angle formed by the cornea and the iris into the channels of the trabecular meshwork and the canal of Schlemm.
  • 10. middle vascular layer • 3- The iris is the most anterior extension of the middle uveal layer which covers part of the lens, leaving a round central pupil The anterior surface of the iris, exposed to aqueous humor in the anterior chamber, consists of a dense layer of fibroblasts and melanocytes • The highly pigmented posterior epithelium of the iris blocks all light from entering the eye except that passing through the pupil.
  • 11. The lens • The lens is a transparent biconvex structure suspended immediately behind the iris, which focuses light on the Retina. • the lens is a unique avascular tissue and is highly elastic, a property that normally decreases with age. • The lens is held in place by fibers of the ciliary zonule, which extend from the lens capsule to the ciliary body this structure allows the process of visual accommodation, which permits focusing on near and far objects by changing the curvature of the lens.
  • 12. vitreous body • The vitreous body occupies the large vitreous chamber behind the lens It consists of transparent, gel-like connective tissue that is 99% water (vitreous humor), with collagen fibrils and hyaluronate, contained within an external lamina called the vitreous membrane. • The only cells in the vitreous body are a small mesenchymal population near the membrane called hyalocytes, which synthesize the hyaluronate and collagen, and a few macrophages.
  • 13. Chambers in the Eye • The eye also contains three chambers. • • The anterior chamber is a space located between the cornea, iris, and lens. • • The posterior chamber is a small space situated between the iris, ciliary process, zonular fibers, and lens. The zonular fibers radiate from the ciliary process and insert into the lens capsule. This forms the suspensory ligaments of the lens that anchor it in the eyeball. • • The vitreous chamber is a larger, posterior space that is situated behind the lens and zonular fibers and is surrounded by the retina.
  • 14. Retina • The innermost lining of the posterior chamber of the eye is the retina that is in contact with the highly vascular choroid. The posterior three quarters of the retina is a photosensitive region. It consists of rods, cones, and various interneurons—cells that are stimulated by and respond to light. The photosensitive part of the retina terminates in the anterior region of the eye, called the ora serrata. This nonphotosensitive part of the retina continues forward in the eye to line the inner part of the ciliary body and the posterior region of the iris
  • 15.
  • 16.