SPECIAL SENSES Cornea

Retina

Optic nerve

Prof.J.Anbalagan

Special sensory organs

Olfactory mucosa

Gustatory cells

Retina

Internal ear

– cochlea

– Semicircular canal

Eyeball

Eye lid Skin – Stratified squamous

keratinized

– dermis

Connective tissue layer

Skeletal muscle (orbicularis oculi)

Tarsal plate with glands

Conjunctiva – Stratified squamous non

keratinized

Cornea

Five layered structure

– Outer corneal epithelium

– Bowman’s membrane

– Substantia propria

– Descemet’s membrane

– Inner endothelium

Corneal epithelium – Thin Stratified squamous non

keratinized-5 LAYER

– Papilla absent

– Straight plane avoids refraction

Bowman’s membrane – Anterior limiting membrane

– Homogenous amorphous with fine collagen

– Forms basement membrane for corneal epithelium

Substantia propria

– Stroma of cornea

– Transparent

– Parallel arranged collagen fibers

– Ground matrix

– glycoaminoglycans+fibroblast

– Collagen are arranged in alternate lamellae with regular spacing for light transmission

Descemet’s membrane

– Posterior limiting

membrane

– Thin and homogenous

– Layers continues into irido

corneal angle

Endothelium

– Single polygonal cells on

a basement membrane

RETINA Nervous coat

Extends from optic disc

to ora serrata

Posterior part of retina

shows yellow spot

macula lutea

Optic disc – area where

optic nerve emerges

Layers of retina 1. PIGMENT LAYER

2. LAMINA OF RODS AND CONES

3. EXTERNAL LIMITING MEMBRANE

4. OUTER NUCLEAR LAYER

5. OUTER PLEXIFORM LAYER

6. INNER NUCLEAR LAYER

7. INNER PLEXIFORM LAYER

8. GANGLION CELL LAYER

9. LAMINA OF NERVE FIBERS

10. INTERNAL LIMITING MEMBRANE

PIGMENT EPITHELIUM

Low cubical cells Basement membrane known as Bruch’s membrane Cells faces towards rods and cones Appear black due to melanin pigments One cell contacts > 12 rods and cones functions – Phagocyte, – antireflection of light, – blood retinal barrier

Pigment cells

Rods and Cones

Photoreceptors

Cones are wider and tapers at the end

Rods are narrow and cylindrical

Under EM they exhibit outer and inner segments

Inner segments contains mitochondria for energy

Outer segment shows discoidal membrane

External limiting membrane

– Sieve like membrane

– Supports rods and cones

– Appears pink linear marking

– Represents zona adherens

of Muller cells

Outer nuclear layer

– Nucleus of rods and cones

– Several layers

ONL

OLM

Outer plexiform layer

– Synaptic area between rods and cones with

– Bipolar neurons

– Horizontal cells

– Amacrine cells

Inner nuclear layer

– Shows nucleus of bipolar, horizontal cells, amacrine cells, Muller cells

Inner plexiform layer

– Synaptic process of

bipolar, amacrine, Muller

with ganglion cells

– Plexiform appearance

Ganglion layer

– Cell body and nucleus of

large ganglion cells and

amacrine cells

Nerve fibers

– axons of ganglion

cells

Internal limiting

membrane

– Homogenous layer

– Formed by end feet of

Muller cell and

astrocytes

RETINA- LAYERS

Microstructure of Retina

OPTIC NERVE

MENINGES

– DURA

– ARACHNOID

– PIA

NERVE FIBERS

– MYELINATED

– ARRANGED IN FASCICULI

– CENTRAL ARTERY OF RETINA

OPTIC NERVE

Cochlea