Eye Anatomy & Physiology

anatomy of the eye, physiology of the vision

1. Anatomy of the Eye BY: Parita Jayswal

2. Eye Parts - Diagram

3. Introduction Organ of sense of sight/vision. Supplied by optic nerve. Helps in judgement of distance and fuction as pair.

4. It is spherical in shap e It is about 2.5 cm in diameter situated in the orbital cavity STRUCTURE OF THE EYE: MAIN 3 LAYERS 1. Outer fibrous layer [sclera, cornea] 2. Middle vascular layer [choroid, ciliary body, irish ] 3. Inner nervous tissue layer [retina]

5. STRUCTURES INSIDE EYEBALL: Lens Aqueous fluid Vitreous body

6. External Anatomy of the Eye

7. Accessory Organs & Eye Protection Orbital cavities (bony sockets) – house & protect the eye Adipose tissue – cushions the eye

8. Lacrimal glands – produce tears that lubricate & have a germicidal effect Eyebrows – protect against foreign articles, perspiration, & direct rays of light

9.  Eyelids – folds of skin that cover the surface of the eye; close by reflex action when an object approaches Eyelashes – secrete oils that prevent lids from sticking together

10. Muscles of eye:- Extrinsic muscles – muscles located outside of the eye that control certain eye movements such as moving the eyeball from side to side or rolling the eyes

11.  Intrinsic muscles – muscles located inside the eye that help hold the lens in place & modify its shape

12. Layers:- There are three layer of the eye Sclera – white, outer layer of the eyeball; tough, fibrous membrane that helps to maintain the spherical shape of the eyeball & gives attachment to extrinsic muscle. Cornea – T ransparent Layer , front part of eyeball through which light waves pass to reach Retina – no blood vessels but lots of nerve endings . Convex anteriorly & involving in bending lightrays to focus them on Retina.

13.  Canals of Schlem – venous passages that drain the fluid that accumulates behind the cornea; located where the sclera & cornea meet  Conjuctiva – thin - transparent mucous membrane that covers the eyeball

14. 2.Choroid layer – middle layer of the eye ; S upplies blood vessels to the eye and contains dark pigment granules that prevent the reflection of light in the eye Deep chocolate brown colored Light enters in eye through pupil, stimulate nerve endings in retina and then absorbed by choroid.

15. Ciliary body – Anteriorly continued with choroid. Consist ciliary muscles & epithelial cell which secreste aqueous fluid. Cotraction and relexation of ciliary muscles Help in change thickness of lens. Supply: parasympathetic branch of occulomotor nerve Iris – visible coloured part of eye lies behind cornea. It has pigmented cell. C olored portion of eye formed by circularly and radially arranged smooth muscle fibers; regulates amount of light entering eye by constricting or dilating the pupil .

16. IRISH SUPPLY : sympathetic and parasympathetic nerve parasympathetic Stimulates constriction of pupil and Sympathetic nerve cause dilatation of pupil. Irish and its pigmented cells decide the colour of eye. [blue eye:few pigmentcell ] PUPIL – rounded opening of the iris through which light passes LENS – High elastic circular biconvex body. Lying on behind the pupil. Lens bend light rays reflected by objects in front of eye.

17. 3.Retina – innermost layer of the eye; Extremly delicate structure It composed of several layers of nerve cell, cell body, axon, etc. This layer is highly sensitive to light, layer of receptive cells “rods & cones” lines its surface and contains photoreceptors (cells responsible for converting light into nerve impulses – rods & cones) In centre area there is little depression called “ fovea centralis ” (it consist ‘cones’) Rods & cones contains photosensitive pigments which convert lights into impulse. Near centre of posterier part is “ macula lutea ” or “yellow spot ”

18. Eye Parts  Rods – cylindrical photoreceptors found in greatest concentration on the edges of the retina; most common type of receptor ; more sensitive than cones, they are stimulated by low intensity or dim light.

19.  Cones – Conical photoreceptors found in greatest concentration near the center of the retina; there are three varieties of cones, each most sensitive to a particular bright light , and colors – blue, green, & red; allow for visual acuity (sharp vision) and color vision

20.  Fovea centralis – a depression, or pit, in center of the retina that contains only cones; provides for the most acute vision & color sensitivity  Optic disk (blind spot) – area where optic nerve attaches to the retina; does not contain any photorecptors

21.  Lens – flexible, biconvex, crystal-like structure that brings rays of light into focus and produces an image on the retina and lying behind the pupil.

22. Suspensory ligament – holds the lens in place; attached to the ciliary body, which controls the amount of tension exerted on the lens

23.  Aqueous humor – watery fluid that provides nutrition and helps maintain the shape of the cornea; found in the smaller, anterior chamber of the eye Fluid in eye:-

24.  Vitreous humor – thick, gel-like substance that fills the largest chamber of the eye and helps to hold its spherical shape

25. Blood supply:- Carotid artery Ophthalmic artery Cilliary artery & Central retinal artery Eye

26. PHYSIOLOGY OF VISION/SIGHT