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The eyes
The document provides information about the basic anatomy and structure of the human eye. It discusses the main parts of the eye including the lens, cornea, retina, optic nerve, iris, pupil, vitreous humor, and aqueous humor. It describes the layers that make up the eyeball including the fibrous, vascular and sensory layers. It also summarizes the pathway of light through the eye and some common eye conditions like myopia, hyperopia, cataracts, conjunctivitis and glaucoma.
The eyes
- 1. BASIC ANATOMY RFD 11104 THE EYE NAME : NOR ADIBAH BINTI MOHD 57179113018 LECTURER : MDM BILQUES SULTANA
- 2. FACTS ABOUT EYE Thelens grows layers like an onion. As you get older, the lens becomes less flexible because the buildup of layes compacts the center of the lens, making it more rigid. When the lens becomes less flexible, it cannot change shape to focus on things nearby. The lense dense only about 20% of our focusing. The cornea does the other 80%. The lens changes shape so that you can focus on things that are near or far away. The ciliary body controls the shape of the lens. Cones are one type of photoreceptor cells in the retina. They are responsible on daylight and colour vision. Rods are the other type of photoreceptor cells. They respond to dim light.
- 3. FACTS ABOUT EYEcontinue The fovea is a dimple in the retina where cones are concentrated and vision is most accurate. The aqueous humor is the clear fluid that helps the cornea keep its rounded shape. The fats that surrounds the eye is there for a reason. It helps cushion the eye and protect it from the hard bone of the eye socket. Each eyeball is held in position in the orbital cavity by various ligament, muscles and facial expansions that surrounds it. The extraocular muscles moves the eyeball in the orbits. The blind spot is the area where the optic leaves the retina. Each eye has a blind spot where they are no photoreceptor cells. The eye has tiny blood vessels that carry blood to the retina.
- 4. STRUCTURE OF THEEYEBALL
- 5. ANATOMY OF THEEYE CHOROID – The intermediate layer of the eye that is located underneath the iris CONJUNCTIVA – the mucous membrane that lines the inner surface of the eyeball CORNEA – the clear front window of the eye. It transmit and focuses light into the eye IRIS – the coloured part of the eye. It help regulate the light that enters the eye PUPIL – the dark center in the middle of the iris. The pupil determines how much light is let in to the eye. It changes sizes to accommodate for the amount of the light that is available LENS – the transparent structure inside the eye that focuses light rays on to the retina
- 6. ANATOMY OF THEEYE continue RETINA – nerve layer that lines the back of the eye. The retina senses the light and creates impulses that are sent through the optic nerve to the brain MACULA – a small area in the retina that contains special light sensitive cells. The macula allows us to see fine details clearly OPTIC NERVE – the nerve that connects to the eye to the brain. The optic nerve carries impulses formed by the retina to the brain, which interprets them as images SCLERA – the thick, tough, white outer that covering eyeball VITREOUS – the clear, jelly-like substance that fills the middle eye. The vitreous gives the eyeball its shape
- 7. Layers forming thewall of the eyeball Fibrous layer Outside layer Vascular layer Middle layer Sensory layer Inside layer
- 8. Structure of theEye: The Fibrous Layer SCLERA White connective tissue layer Seen anteriorly as the ―white of the eye CORNEA Transparent, central anterior portion Allows for light to pass through Repairs itself easily The only human tissue that can be transplanted without fear of rejection
- 9. Structure of theEye: Vascular Layer Choroid is a blood - rich nutritive layer (posterior of eye) Pigment prevents light from scattering Modified anteriorly into two structures Ciliary body—smooth muscle attached to lens Iris—regulates amount of light entering eye Pigmented layer that gives eye color Pupil—rounded opening in the iris
- 10. Structure of theEye: Sensory Layer Retina contains two layers Outer pigmented layer Inner neural layer Contains receptor cells (photoreceptors) Rods Cones
- 11. Structure of theEye: Sensory Layer continue Signals pass from photoreceptors via a two neuron chain Bipolar neurons Ganglion cells Signals leave the retina toward the brain through the optic nerve Optic disc (blind spot) is where the optic nerve leaves the eyeball Cannot see images focused on the optic disc
- 14. Structure of theEye: Sensory Layer continue Neurons of the retina and vision Rods Most are found towards the edges of the retina Allow dim light vision and peripheral vision All perception is in gray tones Cones Allow for detailed color vision Densest in the center of the retina Fovea centralis—area of the retina with only cones No photoreceptor cells are at the optic disc, or blind spot
- 15. Structure of theEye: Sensory Layer continue Cone sensitivity Three types of cones Different cones are sensitive to different wavelengths Color blindness is the result of the lack of one cone type
- 16. Two segments, orchambers, of the eye Anterior (aqueous) segment Anterior to the lens Contains aqueous humor Posterior (vitreous) segment Posterior to the lens Contains vitreous humor
- 17. Anterior Segment Aqueous humor Watery fluid found between lens and cornea Similar to blood plasma Helps maintain intraocular pressure Provides nutrients for the lens and cornea Reabsorbed into venous blood through the scleral venous sinus, or canal of Schlemm
- 18. Posterior Segment Vitreous humor Gel-like substance posterior to the lens Prevents the eye from collapsing Helps maintain intraocular pressure
- 19. PATHWAY OF LIGHTTHROUGH THE EYE Light must be focused to a point on the retina for optimal vision. The eye is set for a distance vision (over 20 feet away). Image formed in the retina is a real image. Real image are : reversed from left to right upside down smaller than the object
- 21. VISUAL FIELD &VISUAL PATHWAY Optic chiasma Location where the optic nerves cross Fibers from the medial side of each eye cross over to opposite side of the brain Optic tracts Contain fibers from the lateral side of the eye on the same side and the medial side of the opposite eye
- 23. EYE REFLEXES Internal muscles : Controlled by the autonomic nervous system Bright light causes pupils to constrict through action of radial, circular, and ciliary muscles Viewing close objects causes accommodation External muscles : Control eye movement to follow objects Viewing close objects causes convergence (eyes moving medially)
- 24. A CLOSER LOOK Myopia(nearsighted) : Distant objects appear blurry Light from those objects fails to reach the retina and are focused in front of it Results from an eyeball that is too long
- 26. Hyperopia (farsighted) : Near objects are blurry while distant objects are clear Distant objects are focused behind the retina Results from an eyeball that is too short or from a ―lazy lens‖
- 28. Homeostatic Imbalances ofthe Eyes Cataracs Conjunctiva Glaucoma Hemianopia Colour Blindness
- 29. CATARACTS—when lens becomeshard and opaque, our vision becomes hazy and distorted
- 30. CONJUNCTIVITIS - itis pink eye and it is infection of the conjunctiva (outermost layer of the eye that cover sclera). Easily treated but contagious though normal contact.
- 31. GLAUCOMA—can cause blindnessdue to increasing pressure within the eye
- 32. HEMIANOPIA—loss of thesame side of the visual field of both eyes; results from damage to the visual cortex on one side only
- 33. COLOR BLINDNESS —genetic conditions that result in the inability to see certain colors Due to the lack of one type of cone (partial color blindness)