2. 1.Describe eye in terms of:
Structure related to vision
Accessory structures
2.Discuss image formation by describing
refraction, accommodation and constriction of
the pupil.
3. Explain the process of dark adaptation and
light adaptation.
4.Refrences
Class Agenda
3. The eye is the organ of the sense of sight
situated in the orbital cavity and it is supplied
by the optic nerve (2nd
cranial nerve).
EYE
5. There are three layers of tissue in the walls of the
eye.
They are:
1.The outer fibrous layer: sclera and cornea
2. The middle vascular layer or uveal tract:
choroid,ciliary body and iris
3. The inner nervous tissue layer: retina.
Structures inside the eyeball are the lens,
aqueous fluid
(humour) and vitreous body (humour).
Structure
7. The sclera, or white of the eye, forms the
outermost layer of tissue of the posterior and
lateral aspects of the eyeball and is continuous
anteriorly with the transparent cornea.
It consists of a firm fibrous membrane that
maintains the shape of the eye and gives
attachment to the extraocular or extrinsic
muscles of the eye.
Sclera and Cornea
9. Anteriorly the sclera continues as a clear
transparent epithelial membrane, the cornea.
Light rays pass through the cornea to reach the
retina.
The cornea is convex ante-riorly and is involved
in refracting or bending light rays to focus
them on the retina.
Cornea
10. The choroid lines the posterior five-sixths of the
inner surface of the sclera.
It is very rich in blood vessels and is deep
chocolate brown in colour.
Light enters the eye through the pupil,
stimulates the nerve endings in the retina and
is then absorbed by the choroid.
Choroid
11. The ciliary body is the anterior continuation of
the choroid consisting of ciliary muscle (smooth
muscle fibres) and secretory epithelial cells.
It gives attachment to the suspensory
ligament which, at its other end, is attached to
the capsule enclosing the lens.
Ciliary Body
12. The iris is the visible coloured part of the eye
and extends anteriorly from the ciliary body,
lying behind the cornea in front of the lens.
It divides the anterior segment of the eye into
anterior and posterior chambers which contain
aqueous fluid secreted by the ciliary body.
Iris
13. The lens is a highly elastic circular biconvex
body, lying immediately behind the pupil.
The lens bends (refracts) light rays reflected by
objects in front of the eye.
The nearer is the object being viewed the
thicker the lens becomes to allow focusing.
Lens
15. The retina is the innermost layer of the wall of
the eye It is an extremely delicate structure and
is especially adapted for stimulation by light
rays.
It is composed of several layers of nerve cell
bodies and their axons, lying on a pigmented
layer of epithelial cells which attach it to the
choroid.
Retina
16. Towards the anterior part of the retina there
are fewer cone- than rod-shaped cells .
The rods and cones contain photosensitive
pigments that convert light rays into nerve
impulses.
The small area of retina where the optic nerve
leaves the eye is the optic disc or blind spot.
It has no light-sensitive cells.
Retina
18. • The eye is supplied with arterial blood by the
ciliary arteries and the central retinal artery.
• Venous drainage is by a number of veins,
including the central retinal vein, which
eventually empty into a deep venous sinus.
The central retinal artery and vein are encased in
the optic nerve, entering the eye at the optic
disc.
Blood Supply
19. Light waves travel at a speed of 186 000 miles
(300 000 kilometres) per second.
Light is reflected into the eyes by objects within
the field of vision.
White light is a combination of all the colours of
the visual spectrum (rainbow),i.e. red, orange,
yellow, green, blue, indigo and violet.
Physiology of sight
20. This range of colour is the spectrum of visible
light.In a rainbow, white light from the sun is
broken up by raindrops which act as prisms
and reflectors.
Physiology of Sight
21. Medial rectus
Lateral rectus
Superior rectus
Inferior rectus
Superior oblique
Inferior oblique.
Extraocular Muscles of the Eye
22. Eyebrows
Eyelids and eyelashes
Lacrimal apparatus.
Accessory Organs of the Eye
23. Ross and Wilson anatomy and physiology in
health and illness 10th
edition.
References
