THE EYE Flashcards
the peripheral organ of vision, is situated in a skeletal cavity, the orbit
The Eyeball
The eyeball is embedded in orbital fat, separated from it by a thin fascial sheath
capsule of Tenon
further divided into anterior chamber and posterior chamber due to the position of the iris.
Anterior Cavity
contains the aqueous humor produced by the ciliary process.
Anterior Cavity
located behind the lens
contains the vitreous humor enclosed in hyaloid membrane
Posterior Cavity
The Layers of the Eyeball: sclera and cornea
Fibrous coat
The Layers of the Eyeball : choroid, ciliary body and the iris
Vascular coat
The Layers of the Eyeball - retina
Neural coat
relatively hard consistency, is a dense layer which, when distended by intraocular pressure, maintains the shape of the eyeball
The Sclera
external surface is white and smooth and is in contact with the inner surface of the fascial sheath of the eyeball
The Sclera
provides passage for nerves of the cornea and vascular autonomic nerves and attachment for extrinsic eye muscles
The Sclera
- is the anterior, projecting transparent part of the external tunic, and
The Cornea
its tear film cover is the major site of refraction of light entering the eye.
The Cornea
3 The Vascular Coat
Choroid
Ciliary Body
Iris
a thin, highly vascular, dark brown tissue which lines almost the posterior five-sixths of the eye;
The Choroid
it is pierced behind by the optic nerve and is firmly adherent to the sclera;
The Choroid
directly continuous with the choroid behind and with the iris in front
The Ciliary Body
It is also a major source of aqueous fluid for the anterior segment of the eye
The Ciliary Body
is an adjustable diaphragm around a central aperture
The Iris
the pupil, which controls the amount of light entering the eye
The Iris
The concentration of melanocytes is the main factor determining the hue of the iris.
The Iris
This is a flat annulus of smooth muscle about 0.75 mm wide and 0.15 mm thick.
Sphincter Pupillae
Its densely packed fusiform myocytes are often arranged in small bundles, as in the ciliary muscle, and pass circumferentially around the pupil.
Sphincter Pupillae
- A thin stratum lying immediately anterior to the epithelium of the posterior iridial surface,
Dilator Pupillae
- its fibers are in fact the muscular processes of the anterior layer of this epithelium,
- their apical processes form the epithelium itself.
Dilator Pupillae
Muscles of the Iris
Sphincter Pupillae
Dilator Pupillae
The Neural Coat
Retina
- is the neural, sensory stratum of the eyeball
- It is thin, being thickest near the optic disc
Near the centre of the retina is an oval, yellowish area, which has a central
the macula lutea
the ___, where visual resolution is highest
fovea centralis
chiefly responsible for high spatial resolution and colour vision in good lighting conditions
(photopic vision),
- highly concentrated at the fovea centralis, but they populate the whole retina, intermingled with rods
red, green and blue
Cone cells
- provide high monochromatic sensitivity to a much wider range of illumination down to much lower intensities (scotopic vision)
Rods
This region, where retinal tissues meet the neural elements of the optic nerve
- also provides a point of entry and exit for the retinal circulation.
- superomedial to the posterior pole of the eye
Optic Disc
The components of the eye which transmit and refract light
The Refractive Media
The Refractive Media
Cornea,
Aqueous humor,
Lens,
Vitreous humor.
an avenue for nutrients, and metabolic exchange for the avascular tissues of the cornea and lens.
Aqueous Humour
fills the vitreous chamber, occupying about four-fifths of the eyeball.
- It is colourless, consisting of approximately 99% water, and although apparently structureless, a sparse but organized cellular and fibrous content is present.
Vitreous Body
Internally it shows a scalloped periphery where it is continuous with the choroid and retina, termed the
ora serrata.
is a transparent, encapsulated, biconvex body, placed between the iris and the vitreous body
Lens
encircled by the ciliary processes, to which it is attached by the zonular fibres collectively forming the zonule holding the lens in place and transmitting the forces stretching the lens except in visual accommodation.
Lens
A condition in which objects, both near and far, appear blurred.
Astigmatism
Is a cloudiness or opacificationin the normally clear and transparent lens of the eye
Cataract
The Accessory Structures of the Eye
- The Eyelids
- The Lacrimal Apparatus
- The Eye Muscles
2 movable folds, with the upper being more larger and movable, due to the presence of the levator palpebra superioris.
The Eyelids
Layers of the Eyelid
Skin
Loose subcutaneous tissue
Muscular layer
Submuscular layer
Tarsal plates
Conjunctiva
which secretes a complex fluid (tears) and whose excretory ducts convey fluid to the surface of the eye,
lacrimal gland
The Lacrimal Apparatus
lacrimal gland
lacrimal canaliculi
lacrimal sac
nasolacrimal duct
located superolaterally along the orbit
Lacrimal Gland
conducts the tears to the lacrimal sac
Lacrimal Canaliculi
located in the lacrimal fossa
presents a fundus
Lacrimal Sac
located in the lacrimal fossa
presents a fundus
Lacrimal Sac
drains into the inferior nasal meatus
Nasolacrimal Duct
drains into the inferior nasal meatus
Nasolacrimal Duct
contains the eyeball in its anterior part and the posterior part is filled with fat, fascia, muscles, blood vessels and nerves
The Orbit
separates the anterior and posterior
Capsule of Tenon
lines the orbit and is continuous with the dura mater of the brain
Periorbita
Lateral rectus is supplied by the
Abducent N.
Superior oblique is supplied by the
Trochlear N.
The rest of the eye muscle is supplied by the
Oculomotor N.
