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TABLE OF CONTENT
The Eye Page 3
The Ear Page 6
Cells Page 8
Childbirth Page 11
Immune Systems Page 12
Blood Cells Page 13
Urine Formation Page 16
Body Defenses Page 17
Homeostasis Page 19
Cardiovascular System Page 20
Skeletal System Page 24
Digestive System Page 26
Urinary System Page 33
Respiratory System Page 37
Endocrine System Page 38
The Reproductive System Page 40
Nervous System Page 43
Muscular System Page 45
Disorders Page 50
, THE EYE
Special senses respond to stimuli involved in vision, taste, smell, hearing and balance. The organs that receive
these stimuli are the eye, nose and ear.
The eye has been studied for decades and it consists of the following external structures:
Extrinsic eye muscle
Lacrimal apparatus
Eyelids
Conjunctiva
The extrinsic eye muscles aim the eyes for following movement and for convergence.
The lacrimal apparatus consists of a series of ducts and glands that produce tears.
The eyelids protect the eyes and eye lashes have ciliary and tarsal glands that are responsible for lubricating the
eye.
The conjunctiva is a mucous membrane that covers the anterior eyeball and lines the eyelids and produces
lubricating mucus.
The eyeball has three layers:
Sclera:
Forms most of the outer layer that protects and is tough and fibrous.
The anterior portion is the cornea which allows light and is transparent.
, Vascular layer:
This layer provides nutrition to the internal eye structure.
The posterior portion is the choroid which prevents light from scattering in the eye and is pigmented.
Anterior modifications include the ciliary body and the iris.
Sensory layer:
Consists of two-layered retina which is a pigmented epithelium and the inner most coat that contains
the photoreceptors.
Rods are dim light receptors and cones are receptors that provide for colour vision and high visual
acuity.
The fovea contrails, on which acute focusing occurs, contains only cones.
The optic disc is the point where the optic nerve leaves the back of the eyeball.
The optic disc results in the blind spot of our vision since no photoreceptors exist there.
The lens is also the major light-bending structure of the eye which is known as a refractory function.
The convexity of the lens is increased by contraction of the ciliary body for close focus.
Anterior to the lens is the aqueous humor, which provides nutrients to the avascular lens and cornea, and
posterior to the lens is the vitreous humor.
Errors of refraction include:
Myopia
Hyperopia
Astigmentation
The pathway of light through the eye is as follows:
Light rays from a distant object are nearly parallel as they reach the eye and can be focused without requiring
changes in lens convexity. (First Diagram)
Diverging light rays from close objects require that the lens bulge more to focus the image sharply on the retina.
(Second Diagram)
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