VisionBioGuru视觉生物大师.pptx

Parts of the Eye1.The Sclera2.The Cornea3.Conjunctiva4.The Choroid Coat5.The Ciliary Body 6.The Iris7.The Pupil8.The Retina9.The Macula lutea10.Fovea11.The Optic Nerve12.The Optic Disk13.The Vitreous Humor 14.The Aqueous HumorThe Conjunctiva lines the inside of the eyelids and covers the sclera(white part of the eye).It is composed of rare stratified columnar epithelium.The Sclera The CorneaWindow of the eyeHelps focus entering light raysComposed of connective tissue w/thin layer of epithelium Has many nerve fibers that enter the margin and radiate toward the center associate with many pain receptors w/low thresholdCold receptors abundantWhite portion of the eyeMakes up 5/6 of posterior outer tunicOpaque b/c of how the collagen and elastic fibers are arranged.Protects the eyeAttachment for extrinsic musclesThe Optic Nerve The Choroid CoatLocated in the back of the eyeAttached to the retinaTransmits images from the retina to the brainFlips the picturesPart of the middle tunicPosterior 5/6 of the globe of the eye Has blood vessels that nourish surrounding parts Contains melanocytesMelanin from melanocytes absorb excess light and keep the inside part of the eye dark The Ciliary Body The IrisThickest part of the middle tunicExtends to the front from the choroid coatForms internal ring around the eyeContain folds called ciliary processes2 groups of muscle fibers ciliary muscles Controls how much light enters the eyeThin diaphragm composed of connective tissue&thin connective tissueIt is the colored portion of the eyeExtends from the front of the periphery in the ciliary body to the middle of the cornea and the lens Divides the anterior cavity(cornea&iris)into anterior chamber(iris and vitreous humor)The Pupil The Lens The circular opening in the center of the iris Black spot in the center of the iris Controls how much light enters the retina Its diameters is usually 3-7 mmTransparentHeld in position by fibers called suspensory ligaments(zonular fibers)from the ciliary processes Lacks blood vesselsLocated behind the iris and the pupilComposed of special epithelial cells Vitreous Humor Aqueous HumorFront of iris and pupilWatery fluid created by epithelium on inner surface of ciliary bodySeparated into anterior and posterior chambersMaintains eye pressureNourishes front part of the eyeJelly-like fluidFills the central core of the eyeHelps maintain spherical shape to the eye this with collagenous fibers form the vitreous body The Macula Lutea The Fovea Centralis Yellowish spot in the retina The central focusing spotResponsible for seeing details(reading)and color visionA depression in the macula luteaIn the region of the retina that produces the sharpest vision Has no rods only cones The Optic DiskLacks receptors,often called the blind spotThe nerve fibers from the retina and became part of the optic nerve.A central artery and vein pass through hereThese vessels with vessels in the choroid coat supply blood to the cells of the inner tunic Jelly-like fluidFills the central core of the eyeHelps maintain spherical shape to the eye this with collagenous fibers form the vitreous bodyThe RetinaComplex structureLayers of(epithelium,nerve fibers,&membranes)Contains photoreceptors called rods and conesContinuous with the optic nerve and extends to the front as the inner lining of the eyeball 6 retinal cell groups:rods,cones,bipolar neurons,ganglion cells,horizontal cells and amacrine cells.provide direct path for impulses to the receptors to the optic nerve&brain The retina contains two types of photoreceptors,rods and cones.The rods are more numerous,some 120 million,and are more sensitive than the cones.However,they are not sensitive to color.The 6 to 7 million cones provide the eyes color sensitivity and they are much more concentrated in the central yellow spot known as the macula.In the center of that region is the fovea centralis,a 0.3 mm diameter rod-free area with very thin,densely packed cones.The receptors in the retinaPigment epitheliumthe pigmented cell layer just outside the neurosensory retina nourishes retinal visual cellsfirmly attached to the underlying choroid and overlying retinal visual cells.Rods ConesResponsible for black and white visionThe rods are more numerous and more sensitive than the conesthey are absent in the fovea centralisResponsible for color visionDensely packed in the fovea centralisHorizontal cells Bipolar cellsHorizontal cells integrate and regulate the input from rods and cones.They are also responsible for allowing eyes to adjust to see well under both bright and dim light conditions.Bipolar cells exist between rods and cones and ganglion cells.They transmit signals from the rods and cones to the ganglion cells.Amacrine cell Ganglion cellA Ganglion cell is a type of neuron located near the inner surface of the retinaIt receives visual information from rods and cones via two intermediate neuron types:bipolar cells and amacrine cells.It transmits visual info to thalamus,hypothalamus and midbrain.Amacrine cells are interneurons in the retina.They are responsible for 70%of input to retinal ganglion cells.They lack axons but have many dendritesDirection of Impulse1.Photons move through the 6 layers of cells and strike the rods and cones2.They process the light information 3.This info is integrated by the horizontal cells4.The info travels to the bipolar cells5.This info then travels to the amacrine cells6.The impulses(info)finally converge at the ganglion cells7.The axons of the ganglion cells carry the info to the brainOptic Nerve(Cranial nerve 2)The optic nerve,also known as cranial nerve 2,transmits visual information from the retina to the brainIt is composed of the axons of the retinal ganglion cellsThe ganglion cell axons are myelinated by oligodendrocytes since it is part of the CNSTHE END