SENSORY ORGAN: EYES// EYE STRUCTURE// EYE BALL

SENSE ORANS ARE THE SPECIALIZED ORGANS COMPOSED OF NEURONS , WHICH HELPS US TO PERCEIVE AND RESPOND TO OUR SURROUNDINGS .
THERE ARE FIVE SENSE ORGANS –
EYES : SENSE OF SEEING
EARS : SENSE OF HEARING
NOSE :SENSE OF SMELL
TONGUE : SENSE OF TASTE
SKIN : SENSE OF TOUCH, PAIN etc.
THE HUMAN EYES ARE SENSE ORGAN ADAPTED TO ALLOW US VISION BY REACTING TO LIGHT .
OUR PAIRED EYES ARE LOCATED IN SOCKETS OF THE SKULL CALLED ORBITS .

1. SENSORY ORGANS: EYES Represented By WASIM AKRAM BSc Nursing ADWIKA INSTITUTE OF NURSING

2. INTRODUCTION SENSE ORANS ARE THE SPECIALIZED ORGANS COMPOSED OF NEURONS , WHICH HELPS US TO PERCEIVE AND RESPOND TO OUR SURROUNDINGS . THERE ARE FIVE SENSE ORGANS – EYES : SENSE OF SEEING EARS : SENSE OF HEARING NOSE :SENSE OF SMELL TONGUE : SENSE OF TASTE SKIN : SENSE OF TOUCH, PAIN etc.

3. EYES THE HUMAN EYES ARE SENSE ORGAN ADAPTED TO ALLOW US VISION BY REACTING TO LIGHT . OUR PAIRED EYES ARE LOCATED IN SOCKETS OF THE SKULL CALLED ORBITS .

4. STRUCTURE OF EYE THE ADULT HUMAN EYE BALL IS NEARLY A SPHERICAL STRUCTURE . THE WALL OF EYE BALL IS COMPOSED OF THREE LAYERS : SCLERA CHOROID RETINA

5. EYE ANATOMY SCLERA : THE EXTERNAL LAYER IS COMPOSED OF A DENSE CONNECTIVE TISSUE AND IS CALLED THE SCLERA . THE ANTERIOR PORTION OF THIS LAYER IS CALLED THE CORNEA . CHOROID : THE MIDDLE LAYER , CHOROID , CONTAINS MANY BLOOD VESSELS AND LOOKS BLUISH IN COLOUR. THE CHOROID LAYER IS THIN OVER THE POSTERIOR TWO-THIRDS OF THE EYE BALL, BUT IT BECOMES THICK IN THE ANTERIOR PART OF THE EYE BALL TO FORM THE CILIARY BODY. THE CILIARY BODY ITSELF CONTINUES FORWARD TO FORM A PIGMENTED AND OPAQUE STRUCTURE CALLED THE IRIS . THE IRIS IS THE VISIBLE COLOURED PORTION OF THE EYE . THE EYE BALL CONTAINS A TRANSPARENT CRYSTALINE LENS WHICH IS HELD IN PLACE BY LIGAMENTS ATTACHED TO THE CILIARY BODY . IN FRONT OF THE LENS , THE APERATURE SURROUNDED BY THE IRIS IS CALLED THE PUPIL . THE DIAMETER OF THE PUPIL IS REGULATED BY THE MUSCLE FIBRE OF THE IRIS.

6. RETINA ….. THE INNER LAYER IS THE RETINA AND IT CONTAINS THREE LAYERS OF NEURAL CELLS; FROM INSIDE TO OUTSIDE – GANGLION CELLS BIPOLAR CELLS PHOTORECEPTOR CELLS RETINAL GANGLION CELLS (RGCs ) ARE THE BRIDGING NEURONS THAT CONNECT THE RETINAL INPUT TO THE VISUAL PROCESSING CENTRES WITHIN THE CENTRAL NERVOUS SYSTEM . BIPOLAR CELLS ARE INTERNEURON TO PROVIDE THE MAIN PATHWAYS FROM PHOTORECEPTORS TO GANGLION CELLS .

7. RETINA …. PHOTORECEPTOR CELLS : THERE ARE TWO TYPES OF PHOTORECEPTOR CELLS, NAMELY, RODS AND CONES . THESE CELLS CONTAIN THE LIGHT-SENSITIVE PROTEINS CALLED THE PHOTOPIGMENTS. THE DAYLIGHT (PHOTOPIC) VISION AND THE COLOR VISION ARE FUNCTION OF CONES . AND THE TWILIGHT (SCOTOPIC) VISION IS THE FUNCTION OF THE RODS . THE RODS CONTAIN A PURPLISH-RED PROTEIN CALLED THE RHODOPSIN OR VISUAL PURPLE, WHICH CONTAINS A DERIVATIVE OF VITAMIN A . THERE ARE THREE TYPES OF CONES RESPOND TO RED , GREEN AND BLUE LIGHTS.

8. THE OPTIC NERVES LEAVE THE EYE AND THE RETINAL BLOOD VESSELS ENTER IT AT A POINT MEDIAL TO AND SLIGHTLY ABOVE THE POSTERIOR POLE OF THE EYE BALL. PHOTORECEPTOR CELLS ARE NOT PRESENT IN THAT REGION AND HENCE IT IS CALLED THE BLIND SPOT .

9. CHAMBERS OF EYE THE SPACE BETWEEN THE CORNEA AND THE LENS IS CALLED AQUEOUS CHAMBER AND CONTAINS A TIN WATERY FLUID CALLED AQUEOUS HUMOR . THE SPACE BETWEEN THE LENS AND THE RETINA IS CALLED THE VITREOUS CHAMBER AND IS FILLED WITH A TRANSPARENT GELL CALLED VITREOUS HUMOR .

10. BLOOD SUPPLY OF EYES ARTERIAL SUPPLY: THE ARTERIAL INPUT TO THE EYE IS PROVIDED BY SEVERAL BRANCHES FROM THE OPHTHALMIC ARTERY , WHICH IS DERIVED FROM THE INTERNAL CAROTID ARTERY . THESE BRANCHES INCLUDE: THE CENTRAL RETINAL ARTERY THE SHORT & LONG POSTERIOR CILIARY ARTERIES THE ANTERIOR CILIARY ARTERIES . VENOUS DRAINAGE: VORTEX VEINS AND THE CENTRAL RETINAL VEIN , WHICH MERGE WITH THE SUPERIOR AND INFERIOR OPHTHALMIC VEINS THAT DRAIN INTO THE CAVERNOUS SINUS, THE PTERYGOID VENOUS PLEXUS AND THE FACIAL VEIN .