Cornea: The first structure encountered by light. It is transparent and lacks blood vessels, relying on oxygen diffusion from the air. Its role is to refract light entering the eye.
Iris: The colored part of the eye, regulating the pupil's size to control light entry.
Pupil: Not a structure but a gap in the iris that allows light passage to the lens.
Lens: Can change shape to control the refraction strength and focus light on the retina precisely.
Retina: Contains two types of receptor cells:
Cone cells: Sensitive to color and function in well-lit conditions.
Rod cells: More sensitive to light intensity, allowing vision in low light but only in black and white.
Fovea: A special area on the retina packed with cone cells for clear vision.
Optic Nerve: Transmits visual signals from the retina to the brain.
Iris Reflex
Protects the retina from damage in bright light by adjusting the pupil's size.
In bright conditions: Pupil constricts to limit light entry; controlled by circular muscles contracting.
In low light: Pupil dilates to allow more light; controlled by radial muscles contracting. This adjustment is crucial for vision in varying light conditions.
Muscles of the Iris
Circular muscles: Contract in bright light, making the pupil smaller.
Radial muscles: Contract in dark conditions, enlarging the pupil.
Conclusion
This video explained the eye's structure and the iris reflex, highlighting how the eye adapts to different light intensities to protect the retina and ensure clear vision across varying conditions.