Eye Histolgy

Views:
 
Category: Education
     
 

Presentation Description

No description available.

Comments

Presentation Transcript

Eye :

Eye Dr Pankaj Maheria

PowerPoint Presentation:

The eye is the photosensory Peripheral organ of vision Spherical in shape Structure associated with eyeball: Extraocular muscle Eyelid Lacrimal gland

Coats of eye balls:

Coats of eye balls It is composed of 3 tunicae Fibrous coat ( sclera and cornea ) forming the tough outer coat. Vascular coat ( choroid, ciliary body and iris ) forming the pigmented and vascular middle layer. Neural coat ( retina ), forming the innermost layer.

Fibrous coat :

Fibrous coat The fibrous coat is formed of: Cornea. Sclera.

Sclera :

Sclera Opaque Fibrous CT layer Covers the posterior 5/6 of the eye ball Receives insertions of extrinsic ocular muscles. Separation: Externally: Tenon’s capsule - episcleral layer Internally : choroid – Lamina fusca Lamina cribrosa

Cornea :

Cornea Transparent , avascular and forms the anterior 1/6 of the eye ball. It joins the sclera at the limbus which is highly vascularized . The cornea is avascular , it derived its nutrition from the aqueous humour and the blood vessels of the surrounding limbus . Corneal epithelial cells divide repeatedly by mitotic division, but the endothelial cells do not divide after birth (they are not replaced).

Cornea:

Cornea The transparency of the cornea is due to: Its uniform diameter. Regular arrangement of the collagen fibers. Properties of ground substance (matrix). Absence of blood vessels.

Cornea:

Cornea 5 layers : Corneal epithelium Bowman’s membrane Substantia propria Descemet’s membrane Corneal endothelium

Cornea:

Cornea Corneal epithelium Stratified squamous non-keratinized. About five-cells thickness. Microvilli to hold thin film of tear The epithelium has many free nerve endings and is very sensitive to stimuli specially pain. Capacity of regeneration At limbus , continus as epithelium of bulbar conjuctiva

Cornea:

Cornea Bowman’s membrane or anterior limiting membrane A thin membrane below the corneal epithelium, formed of type I collagen fibers arranged in random fashion. Homogeneous acellular Gives great stability and strength

Cornea:

Cornea Substantia propria or stroma The thickest layer of the cornea. Composed of type I collagen fibers and corneal cells (modified fibroblasts). The fibers are arranged in lamellae which run parallel to the corneal surface.

Cornea:

Cornea Descemet’s membrane or posterior limiting membrane It is basement membrane of the corneal endothelium, containing an atypical type of collagen fibers which have elastic character. At the limbus this layer break up into a trabecular meshwork enclsoing space of Fontana at iridocorneal angle.

Cornea:

Cornea Corneal endothelium It is the innermost layer of the cornea. Composed of a single layer of large squamous or cuboidal cells.

Sclerocorneal junction / limbus:

Sclerocorneal junction / limbus A shallow depression externally Transparent cornea become opaque sclera. Canal of Schlemm or scleral venous sinus Aqueous humour

Vascular coat (uvea):

Vascular coat ( uvea ) Choroid Ciliary body Iris

Choroid::

Choroid: The choroid is the highly vascular, pigmented layer of the eye. Lies between sclera and retina Its loose CT contains many melanocytes which give a purple black color. It is loosely attached to the tunica fibrosa .

Choroid::

Choroid: Layers : Suprachoroidal layer Vascular layer Choriocapillary layers Bruch’s membrane (Glossy membrane)

Ciliary body :

Ciliary body Circumferentially thickened part Extending from ora serrata to edge of lens. Triangular in cross section It encircles the lens completely.

Ciliary body :

Ciliary body Part: Ciliary processses Ciliary muscle Formed of C.T. , melanocytes , blood capillaries & ciliary muscles.

Ciliary body :

Ciliary body Ciliary muscle Longitudinal ,circular and radial Innervated by parasympathetic nerve fibres . Muscle of accommodation

Ciliary body :

Ciliary body Ciliary processes project from its medial side & are covered by 2 layers of cubical epithelium: Outer pigmented : Inner non-pigmented : transports components from the plasma filtrate in the posterior chamber and thus forms aqueous humor which flows to the anterior chamber via the pupillary aperature . They also possess suspensory ligaments ( zonule ) that is inserted in the capsule of the lens.

Iris :

Iris Anterior part of middle coat A pigmented circular diaphragm in front of lens with an aperture in the centre . It is covered anteriorly by endothelium lining the anterior chamber & continuous with that on the posterior aspect of cornea.

Iris :

Iris Its wall composed of loose vascular CT containing melanocytes and fibroblasts. Muscle Layer (Constrictor & dilator pupillae ). Posterioly covered by pigmented epithelium (2 layers of cubical cells).

Iris :

Iris Functions of Iris: Control size of pupil, amount of light & depth of focus. Share in the formation of aqueous humor from its posterior surface (minimal). Color of the eye.

Nervous Coat :

Nervous Coat It is the innermost layer of the eye and is responsible for photoreception. Anteriorly , it decreases in thickness and becomes continuous with the ciliary body and called ora serrata . Posteriorly , it forms the optic disc, where the nerve fibers merge to form the optic nerve. Fovea centralis : a shallow depression in its posterior wall that contains only cones and exhibits the greatest visual acuity .

Nervous Coat :

Nervous Coat Developmentally : the retina is formed of 2 layers of optic cup. The outer layer develops into the retinal pigmented epithelium . The inner layer develops into the neural retina .

Nervous Coat:

Nervous Coat Three main neuron Photoreceptors - rods and cones Bipolar neurons Ganglionic multipolar neurons Association neurons Horizontal cells Amacrine cells Muller’s cells

Layers of retina :

Layers of retina The retina is formed of 10 layers: from outer to inner pigment layer layers of rods and cones external limiting membrane outer nuclear layer outer plexiform layer inner nuclear layer inner plexiform layer ganglionic cell layer nerve fibre layer internal limiting membrane

Layers of retina:

Layers of retina pigmented epithelium It is a single layer of melanin-rich high cuboidal cells. Their outer (basal) border lies opposite to Bruch's membrane. Their inner border sends microvilli , which extend to touch the tips of rods and cones. Function: The pigmented layer acts as a dark coat to absorb extra light from behind rods and cones. The cells phagocytose the old discs detached from the tips of rods and cones and digest them by their lysosomes .

Layers of retina:

Layers of retina Rods and Cones Next to the epithelium lies a layer that contain the photosensitive portions (i.e. the outer segment) of rods and cones.

Layers of retina:

Layers of retina outer limiting membrane Is formed by the junction complexes between the photoreceptors and the processes of Muller's cells.

Layers of retina:

Layers of retina outer nuclear layer It contains densely packed cell bodies of the photoreceptors (1st order neuron ).

Layers of retina:

Layers of retina OUTER PLEXIFORM LAYER The synaptic bodies of the photoreceptors synapse with the dendrites of the 2nd order neurons. The two types of neurons represented in this layer are: Bipolar cells. Horizontal cells.

Layers of retina:

Layers of retina INNER NUCLEAR LAYER: It contains the nuclei of bipolar cells (2nd order neuron) and the nuclei of association neurons (horizontal cells, Amacrine cells and Muller's cells.)

Layers of retina:

Layers of retina INNER PLEXIFORM LAVER This layer contains the synaptic contacts between the axons of bipolar cells and the dendrites of the ganglion cells.

Layers of retina:

Layers of retina GANGLION CELL LAYER: It consists of the large nerve cells with vesicular nuclei (3rd order neuron).

Layers of retina:

Layers of retina LAYER OF OPTIC NERVE FIBERS: It contains the axons of ganglion cells. The fibers arise from the cell bodies and emerge as the optic nerve . The fibers become myelinated as they pierce the sclera.

Layers of retina:

Layers of retina INNER LIMITING MEMBRANE: It limits the retina from inside separating it from the vitreous body. It consists of the termination of Muller's fibers lying on a basement membrane.

PowerPoint Presentation:

Blood retinal barrier: It prevents large molecules present in blood from passing to the tissue of the retina: 1. The pigmented epithelial cells are connected by tight junction. 2. The blood capillaries are of the continuous type.

PowerPoint Presentation:

Rod Cone 120 million in each eye 6 million in each eye Distributed around the periphery Concentrated in the centre Absent in fovea centralis Present in large number in fovea Sensitive to light of low intensity (dim light vision), i.e. for night vision Sensitive to light of high intensity (bright light vision ) i.e. for day vision Low resolution , so image without clear detail High resolution , so image sharp and clear Not for colour discrimination For colour discrimination

PowerPoint Presentation:

Rod (Microscopic) Cone (Microscopic) Outer segment is thin, long and cylindrical (100-120 µm ) Outer segment is thick short and conical (65-75 µm ) Dark round nuclei situated deep to external limiting membrane Pale oval nuclei situated close to external limiting membrane Rod fibre ends in knob like rod spherule Cone fibre end in cone pedicle having a branched expansion Group of rods are connected with bipolar neurons (polysynaptic) One cone synapse with single bipolar neurone (monosynaptic) Membranous disc are independent Membranous disc are continuous with plasma membrane Disc contain photopigement rhodopsin Disc contain photopigment iodopsin Tips of the rods are constantly shed and phagocytosed by pigment epithelium Tip of cones are neither shed or phagocytosed by pigment epithelium Protein is concentrated at the base of recently formed discs Protein is uniformly distrubuted .

Applied anatomy:

Applied anatomy Retinitis pigmentosa Macular degeneration Cone-rod dystrophy (CORD)

Applied anatomy:

Applied anatomy Retinal detachment hypertensive retinopathy and diabetic retinopathy. Retinoblastoma

Refractive Media of the Eye:

Refractive Media of the Eye Cornea Aqueous humor. Lens Vitreous body.

Aqueous Humor :

Aqueous Humor It is a thin watery fluid present in the anterior and posterior chambers of the eye. Formation: By filtration from posterior surface of iris and ciliary processes. Active secretion by the epithelium of ciliary body. Circulation and absorption: Posterior chamber  anterior chamber  spaces of fontana  canal of Schlemm  aqueous veins  venous circulation. Rate of production = rate of drainage, this keeps constant the IOP. If rate of production > rate of drainage will end in Glucoma .

Vitreous Body:

Vitreous Body It is an avascular mass of gelled intercellular substance. It is traversed by the hyaloid canal, which marks the position of hyaloid artery of the embryonic eye. The colloidal gel contains hyaluronic acid and a network of type Il collagen fibers. Function : Transmit light (one of the refractive media). Supports the lens anteriorly and the retina posteriorly . Helps in retinal metabolism, allowing transfer of materials from and to the retina.

Lens:

Lens It is a transparent, biconvex structure of epithelial origin. Nourished by aqueous humor. It has neither blood nor nerve supply . It is suspended by the zonule of ciliary body behind the pupil.

Lens:

Lens Capsule : It is thick lamina that covers the entire lens. Subcapsular Epithelium: A layer of cubical epithelium covering the anterior surface of lens only (under the capsule). Lens fibers: They are elongated specialized epithelial cells filled with proteins that make up most of the lens. They have no organelles or nuclei.

Accessory structures of the eye:

Accessory structures of the eye Eyelid Lacrimal gland

Eyelid :

Eyelid Two movable fold placed in front of eye to protect it from injury and excessive light Upper is larger and more mobile External surface: skin Internal surface: muscous membrane called conjunctiva Eyelashes Double or triple rows Sebaceous gland ( Glands of Zeis ) in hair follicle Ciliary gland of Moll ( Modified sweat galnds ) open on free margin

Eyelid :

Eyelid Thin skin Subcutaneous layer Muscle layer Loose Ct layer Tarsal plate and tarsal glands Palpebral conjunctiva

Lacrimal gland :

Lacrimal gland Compound tubuloacinar gland Antibacterial enzyme , lysozyme and electrolytes Two parts Orbital part Palpebral part

PowerPoint Presentation:

Assignment What are the structures seen with ophthalmoscope in the living retina??

PowerPoint Presentation:

Thank You

authorStream Live Help