Aesthesiology (Sense organs)

Sense organs include:1. Eye : Organ for vision2. Ear: Organ for hearing 3. Nose: organ for smell4. Skin: Sense for touch, heat and cold.5. Tongue: Sense for taste.

EYE

Eye in general consisting of:

(1) Eye ball and (2) Accessory structures

Major Layer and Chambers of eye Ball

Eye ball consisting of three layer:

(1)Fibrous tunic: Sclera and Cornea(2)Vascular layer: Ciliary body, Ciliary process, Iris.(3) Nervous layer: Retina.Chambers of the eye ball:(4)Anterior chamber: In between cornea and iris.(5)Posterior chamber: In between iris and lens(6)Vitreous body: In between lens and retina.

Accessory Structure of Eye Ball

1. Muscles of the eye ball: (a) 4 rectus muscles: Dorsal rectus, Ventral rectus Lateral rectus and Medial Rectus (b) 2 Oblique: Dorsal oblique and ventral oblique (c) Retractor oculi 2. Periorbital fat.3. Nerves: Optic, Occulomotor, Trochlear, Opthalmic, and

Abducent.4. Optic artery and vein.5. Lymphatic channels, and,6. Lacrimal apparatus: Lacrimal gland, duct, sac, naso-lacrimal duct.7. Eye lid: Upper and lower eye lid.8. Conjunctiva: Palpebral and bulbar conjuctiva.

Structure of the Eye Ball

Fibrous Tunic of Eye Ball

The fibrous tunic is the outer most layer of the eye ball, gives the shape of the eye ball and consist of dense collagenous fiber. The fibrous tunic consist of:

Sclera: Posterior three-quarter of the eye ball, whitish and tough.

Cornea: Anterior transparent part is the cornea.

Sclera and cornea meet anteriorly at corneo-scleral junction or limbus.

Vascular Layer of the Eye BallThe vascular layer consist of three layers:(1) Choroid (2) Ciliary body and (3) IrisFunction: Blood supply, suspension and regulation of the shape of the lens, regulation of the size of the pupil, and production of aqueous humor.

Choroid: It is pigmented, highly vascular layer and envelop the posterior part of the eye-ball. Near the optic papilla it consist of half moon-shaped area the tapetum.

Ciliary body: Thickest middle segment between choroid and iris. It consist of ciliary process and zonular fiber. Ciliary process is responsible for formation of aqueous humor and zonular fiber connects with the lens and controls shape of the lens.

Iris: It is the anterior most part of the vascular layer and act as a muscular diaphragm between cornea and lens. It forms the pupil.

Nervous Layer of the Eye Ball

It is the innermost layer of the eye ball where light reflect and forms images. It consist of ten histological layers. Optic nerve innervates into this layer.

Inner Structure of Eye Ball (Lens and Chambers)

Lens of eye ball: The lens is a transparent biconvex structure and suspended in the eye by zonular fibers. The posterior surface is more convex than the anterior. The convexity changes for the accommodation of light. It receives nutrition from aqueous and vitreous humor.

Eye has three chambers: (a) Anterior (b) Posterior and (c) Vitreous Chamber.

(a) Anterior Chamber: It is bounded anteriorly by cornea and posteriorly by Iris and lens. It is communicated to the posterior chamber through the pupil.

Posterior Chamber and Vitreous Chamber

Posterior chamber: It is bounded anteriorly by iris and ciliary body and posteriorly by lens. It is filled up with aqueous humor.

Vitreous Chamber: It is bounded anteriorly by lens and ciliary body. The rest of the vitreous chamber is enclosed by the retina. It is filled by viscous jelly like mass called vitreous humor/vitreous body.

Chambers and Lens of Eye Ball

Cornea Lens

Ant. Cham.PosteriorChamber

CiliaryProcess

Sclera

IridocornealJunction

Formation, circulation and drainage of aqueous humor:

Active secretory process from the epithelium of the ciliary body

Aqueous humor circulate through-out the posterior chamber

Pass through the pupil

Aqueous humor enters into the anterior chamber and circulate throughout it

Finally drain through the iridocorneal junction into venous circulation

Formation, Circulation and Drainage of Aqueous Humor

Aqueous humor produced by an active secretory process from the epithelium of the ciliary body. It is clear and colorless fluid containing several electrolytes, amino acids, glucose and ascorbic acid.It flows from posterior chamber to the anterior chamber through the pupil and drains through the iridocorneal junction into the venous plexus. Impairment of the flow and drainage of aqueous humor results in Glaucoma. It increases intraocular pressure resulting retinal atrophy and blindness. We can diagnose it by the protrusion of the eyeball. Function of aqueous humor: It provides nutrition to the cornea and lens.

Lacrimal apparatusLacrimal gland & Excretory duct

Lacrimal canaliculi

Lacrimal sac

Nasolacrimal duct

Lacrimal gland (tear gland)secretes lacrimal fluid, excrete into the conjunctival sac. Fromhere through lacrimal canaliculiinto the lacrimal sac and finallyvia the nasolacrimal duct drains into the nasal cavity.Composition: Water, salt andFew electrolytes. Any defect in the secretoryMechanism leads to “dry eyeSyndrome”.