Eye Structure diagram| Cornea , Iris ,Lens Retina| O Level Biology 5090

Eye Structure Diagram 5 Marks | Cornea, Iris, Lens, Retina | O Level Biology 5090 | Past Paper Solved CHAPTER: Eye Structure - For Past Paper Fig 4.1 + 4.2 1. PARTS OF EYE (Front View) Pupil: Black hole in center, lets light enter Iris: Colored part, controls pupil size. Has 2 muscles - circular and radial 2. ACCOMMODATION - Fig 4.1 Graph How lens changes shape to focus near/far: Near object (Book P): Lens MOST CURVED Ciliary muscles CONTRACT Suspensory ligaments LOOSE Lens becomes FAT / THICK Far object (Bird R): Lens LEAST CURVED Ciliary muscles RELAX Suspensory ligaments TIGHT Lens becomes THIN Middle (Clock Q): Slightly curved Order: P (book) → R (bird) → Q (clock) 3. PUPIL REFLEX - Fig 4.2 & 4.3 In Dim Light (Fig 4.2): Pupil LARGE / DILATED Radial muscles contract, Circular relax More light enters In Bright Light (Fig 4.3): Pupil SMALL / CONSTRICTED Circular muscles contract, Radial relax Less light enters 4. TYPE OF RESPONSE Pupil Reflex / Pupillary Reflex It is a REFLEX ACTION / Involuntary action 5. IMPORTANCE Protects retina from damage by too much light Prevents dazzling and helps to see clearly Yes 2.