Special Senses (VISUAL) Flashcards
- Each eyeball is positioned in a bony depression in the skull called orbit
- Only the anterior one-sixth of the eye’s surface can normally be seen
- Made up of the eyeball specialized for its ability to react to light
Visual Sense/Apparatus
- the stimuli for sense of vision, the light rays must pass through the different parts of the refractive media before reaching the retina.
- These are the following:
o cornea
o aqueous humor
o lens
o vitreous humor
Eyeball
protects, lubricate, move the eye
Accessory structures of the eye
Accessory structures of the eye :
- Extrinsic Eye Muscles
- Eyelids
- Conjunctiva
- Lacrimal apparatus
- controlled by orbicularis oculi
Eyelids
o Modified sebaceous glands associated with the eyelid edges
o Produce an oily secretion that lubricates the eyes
Meibomian Glands
- transparent covering of the eyeball
Conjunctiva
o Modified sweat glands between the eyelashes
Ciliary Glands
- Anteriorly the eyes are protected by the __________ which meet at the medial and lateral corners of the eye, the medial and lateral canthus respectively
Eyelids
____________ occur 20 times per minute.
____________ Projecting from the border of each eyelid.
- Blinking
- Eyelashes
o Lines the eyelids and covers part of the white eye (sclera) infront
o Secretes the mucus which helps to lubricate the eyeball and keep it moist
Conjunctiva
o Located above the lateral ends of each eye
o Continually release a dilute salt solution (tears= “ lacrimal fluid) that drain into the nasal cavity through the inferior meatus
o Lacrimal fluid not only moistens and lubricates conjunctival sac but also reduces eye infections because it contains bactericidal enzyme (lysozyme
Lacrimal Glands
CONTROL MOVEMENT OF EYEBALL
- lateral rectus moves eye
- medial rectus moves eye
- superior rectus moves eye
- inferior rectus moves eye
- inferior oblique moves eye
- superior oblique move eye
what are the action of those?
- laterally
- medially
- upwards medially
- downward and medially
- upwards and laterally
- downwards and laterally
➢ the outermost coat
➢ also called the fibrous tunic seen anteriorly as the “white of the eye”
➢ covered in the anterior part by the transparent conjunctiva
➢ densely packed collagenous fibers (type I collagen fibrils) – where tendons of extraocular muscles are attached
➢ pierced by optic nerve, ciliary nerves and blood vessels
Sclera
o Protects the delicate inner structure of the eye and with the intraocular pressure maintain the shape and turgor of the eyeball
o Sclera - posterior 5/6 - opaque, white of the eye
o Cornea - Anterior 1/6 – Transparent
Fibrous Coat
➢ The central transparent anterior portion of the eye covering the colored part of the eye which is the iris
➢ One of the few organs that can be successfully transplanted from one person to another without the worry of rejection because it has no blood vessels thus it is beyond the reach of the immune system
➢ Avascular and the central part depends on diffusion from aqueous humor for its nourishment.
➢ Thicker than sclera with refractive power 2x as high as the lens
Cornea
- Increase in light ?
- decrease in light ?
- Constrict
- Relax