Term
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Definition
| sensory units within the eye. Convey information from the outside world to the CNS. |
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Term
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Definition
| Complex & highly developed photosensitive organ. Accurately analyzes form, light intensity, and color reflected from objects. |
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Definition
| Where eyes are located, protective bony structures. |
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Term
| Main functioning components of the eye |
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Definition
Globe- tough fibrous;maintains shape
Lens- focus images
layer of photosensitive cells
System of cells and nerves- collect process and transmit visual info to Brain |
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Term
| Eye's 3 concentric layers |
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Definition
External layer- Schlera and cornea
Middle Layer(Vascular layer, uveal tract, vascular tunic, uveal layer, etc)- choroid, of ciliary bodies; iris.
Inner Layer- retina, inner layer of nerve tissue (consists of outer pigment epithelium and inner retina proper/photosensitive) |
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Term
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Definition
| Photosensitive. Part of CNS. communicates with cerebrum via Optic Nerve. Extends forward to ora serrata. |
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Term
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Definition
| Where the retina ends anteriorly. Adjacent to lens. |
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Term
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Definition
| Optic nerve and retina arise from this as an evagination during embryonic development. |
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Term
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Definition
| nerve of the CNS. not Peripheral like other cranial nerves. Therefore the myelin of the nerve fibers is produced by oligodendrocytes. (not Schwann cells) May explain visual dysfunction w/ multiple sclerosis, a demyelinating disorder. |
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Term
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Definition
| Biconvex, transparent structure of the eye. Held in place by the zonule. |
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Term
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Definition
| Circular system of fibers that holds the lens in place and extends into a thickening of the middle layer AKA ciliary body and on posterior side the vitreous body. |
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Term
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Definition
| pigmented expansion of the middle layer of the eye that is opaque and partially covers the anterior side of the lens. |
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Term
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Definition
| Round hole in the middle of the iris. |
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Term
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Definition
Anterior Chamber- b/n cornea and the iris and lens
Posterior Chamber- b/n iris, ciliary process, zonular attachments, and lens
Vitreous Space- behind the lens and zonular attachments, and surrounding the retina. |
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Term
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Definition
| Protein-poor fluid in the post. and ant. chambers. |
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Term
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Definition
| Gelatinous material that fills the vitreous space. |
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Term
References
Outer(External)
Inner(Internal) |
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Definition
Close to the eyeball's surface
Structure closer to the center of the globe |
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Term
Begin External layer terms
Sclera |
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Definition
Opaque white posterior 5/6ths of the external eye.
segment of a sphere aprox. 22mm in Diameter.
Made of tough, dense connective tissue of mainly flat collagen bundles intersecting at various angles, while remaining parallel to the eye's surface. Also has moderate amt of ground substance and a few fibroblasts. |
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Term
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Definition
| External surface of the sclera. Connected by a loose system of thin collagen fibers to the Tenon's capsule. |
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Term
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Definition
| Dense layer of connective tissue connected to the episclera. Comes into contact w/ loose conjunctival stroma @ the junction of cornea and sclera |
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Definition
| area b/n sclera and Tenon's Capsule. This is what allows the eyes rotational movement. |
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Term
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Definition
| Thin layer of loose connective tissue rich in melanocytes, fibroblasts, and elastic fibers; located b/n the sclera and choroid. |
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Term
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Definition
| Anterior 1/6th of the eye. Transparent and colorless. Consists of 5 layers. |
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Term
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Definition
Epithelium
Bowman's membrane
stroma
Descemet's membrane
endothelium |
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Term
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Definition
| nonkeratinized stratified squamous epithelium. aprox 5-6 cell layers. Many mitotic figures in basal portion, so fast regenerative capacity (aprox 7 days) |
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Term
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Definition
| collagen fibers crossing at random, a condensation of intercellular substance and no cells. Contributes to strength and stability of the cornea. |
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Term
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Definition
| many layers of parallel collagen bundles crossing at right angles and running the entire width of the cornea. b/n the layers are flattened fibroblasts. all of which is immersed in a substance rich in glycoproteins and chondroitin sulfate. Avascular, but migrating lymphoid cells are often present. |
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Term
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Definition
| thick homogenous structure of fine collagenous filamewnts in 3D network. |
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Term
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Definition
| simple squamous epithelium. cells have organelles needed for secretion(may be related to creating and maintaining Descemet's memb). |
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Term
| Corneal epi/endo thelium's responsibility |
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Definition
| Maintain transparency of the cornea. Both layers can transport Na ions to the apical surface, chloride and H2O ions follow passively maintaining corneal stroma relatively dehydrated. Dehydration and thin collagen fibrils of the stroma accounts for transparency |
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Term
| Why is the cornea transparent? |
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Definition
| The stroma is made of thin collagen fibrils and kept in a dehydrated state. |
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Term
| Corneoscleral junction AKA limbus |
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Definition
| Area of transition from transparent collagen bundles of the cornea to the white opaque fibers of the sclera. Highly vascular, important to inflammatory processes. |
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Term
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Definition
| Cornea is avascular. Gets metabolites by diffusion from adjacent vessels and fluid of the anterior chamber. |
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Term
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Definition
| in area of limbus, in stromal layer. drains fluid from the anterior chamber of the eye. formed from the merging of irregular endothelium-lined channels and trabecular meshwork. |
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Term
| Middle Layer of eye begins. AKA? |
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Definition
| Vascular layer, uveal tract, vascular tunic, uveal layer, etc. |
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Term
| 3 parts of the eye's middle layer. |
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Definition
| Choroid, ciliary body, and iris (collectively known as Uveal tract) |
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Term
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Definition
| Highly vascular coat. loose connective tissue b/n blood vessels. Rich in fibroblasts, macrophages, lymphocytes, mast cells, plasma cells, collagen fibers and elastic fibers. Melanocytes are rich here, giving this layer its black color. The inner layer is richer in small vessels and is called choriocapillary layer. |
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Term
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Definition
| inner layer of the choroid, richer than outer layer in small vessels. |
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Term
| function of choriocapillary layer |
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Definition
| Nourishes the retina, any damage to this tissue causes subsequent damage to the retina. This is separated from the retina by Bruch's membrane. |
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Term
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Definition
| thin membrane separating the retina and the choriocapillary layer. extends from optic papilla to the ora serrata. |
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Term
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Definition
| region where optic nerve enters the eyeball |
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Term
| 5 layers of Bruch's membrane |
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Definition
central layer composed of a network of elastic fibers.
The central layer is lined on both surfaces with layers of collagen fibers which are covered by the basal lamina of the capillaries of the choriocapillary layer on one side and pigment epithelium on the other. the choroid is bound to the sclera by the suprachoroidal lamina. |
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Term
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Definition
| Anterior expansion of the choroid at the level of the lens. Thickened ring at the anterior portion of the sclera. Triangular in shape, makes contact with vitreous body, sclera, and the lens. Loose connective tissue, surrounding the ciliary muscle. |
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Term
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Definition
| 2 bundles of smooth muscle. insert on the sclera and the ciliary body. One bundle stretches the choroid, the other contracts to release tension on the lens. (important in visual accommodation, focusing) |
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Term
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Definition
| facing vitreous body, posterior chamber and the lens are covered by the anterior extension of the retina. |
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Term
| Anterior section of retina, adjacent to ciliary body |
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Definition
| Retina consists of 2 layers, adj is simple columnar cells rich in melanin the forward projection of the pigment layer of retina. 2nd layer, simple nonpigmented columnar epithelium derived from sensory layer of retina. |
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Term
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Definition
| Ridgelike extensions of the ciliary body. from these processes, the zonule fibers emerge and insert into the capsule of the lens and anchor it in place. |
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Term
| Ciliary processes "head-head" |
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Definition
| the epithelial cells, both pigmented and nonpigmented lie head-head. these apical ends are joined by desmosomes and tight junctions. |
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Term
| non pigmented layer of epithelium |
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Definition
| extensive basal infoldings and interdigitations. These cells actively transport constituents of plasma into the posterior chamber, thus forming the aqueous humor. |
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Term
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Definition
| formed by nonpigmented inner layer of epithelial cells transporting fluid, constituents of plasma, into the posterior chamber. Similar composition to plasma, but only .1% protein not 7 |
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Term
| non pigmented layer of epithelium |
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Definition
| extensive basal infoldings and interdigitations. These cells actively transport constituents of plasma into the posterior chamber, thus forming the aqueous humor. |
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Term
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Definition
| formed by nonpigmented inner layer of epithelial cells transporting fluid, constituents of plasma, into the posterior chamber. Similar composition to plasma, but only .1% protein not 7 |
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Term
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Definition
| flows to lens. passing b/n lens and iris, reaching the anterior chamber-cornea and basal part of iris-penetrateslimbus tissue in labyrinthine spaces-reaches Schlemm's canal(lined w/ endothelial cells) which then communicates w/ small veins of the sclera where the aq. hum. escapes! |
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Term
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Definition
| when drainage of AQ. HUM. is impeded. Results in increased intraocular pressure. |
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Term
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Definition
| extention of choroid, partially covers the lens with a round hole, pupil. |
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Term
| Iris Anterior surface, and subsequent layers. |
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Definition
| rough and irregular with grooves and ridges. Formed by a discontinuous layer of pigment cells and fibroblasts. next layer poor vascular conn tissue few fibers, many melanocytes and fibroblasts. Next layer rich vasculature embedded in loose conn tissue. |
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Term
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Definition
smooth, covered by 2 layers of epium which also cover the ciliary body and processes. Inner epium contacts post chamber is heavily pigmented with melanin granules.
Outer epium cells have radially directed tonguelike extensions of basal region filled w/ overlapping myofilaments, dilator pupillae muscle. |
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Term
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Definition
| posterior part of iris, on outer epium. Heavy pigmentation prevents light from passing anywhere other than the pupil. Sympathetic. |
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Term
| melanocytes and pigment cells |
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Definition
| prevent stry light from entering the eye and distorting the images we see. melanocytes of stroma of the iris give eyes their color. Little pigment, blue-blue-gray-broen most pigment-black. Albino, almost no pigment, pink from reflection of bld vessels. |
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Term
| sphincter pupillae muscle |
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Definition
| smooth muscle bundles in circles concentric w/ pupillary marginin the iris. Parasympathetic. |
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Term
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Definition
| biconvex structure. very elastic, lost w/ age. |
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Term
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Definition
Lens Capsule
Subcapsular Epithelium
Lens Fibers |
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Term
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Definition
| consists mainly of collagen type IV and glycoprotein. Envelopes the lens, homogenous refractile, carbohydrate rich capsule. Coats outer surface of epithelial cells. |
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Term
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Definition
| Simple cuboidal. only on anterior surface. exhibit interdigitations w/ the lens fibers. Lens fibers grow throughout life thus the liens size incr. |
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Term
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Definition
| Highly differentiated, derived from epithelium. Eventually lose nucleus and organelles, becoming greatly elongated. produced throughout lifetime, but at a decreasing rate. Cells are filled with a group of proteins, crystallins. |
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Term
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Definition
| the zonule, made of fibers, holds the lens in place and facilitates accommodation, permits focusing. Looking in distance, lens is kept stretched, when looking at something close, ciliary muscles contract choroid and ciliary body move forward tension in the zonule lessens, and object is kept in focus. |
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Term
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Definition
| lens elasticity decreases with age, making accommodation difficult. |
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Term
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Definition
| lens made less transparent by opaque matter caused by buildup of pigment on lens fiber. cause UV exposure, high glucose of diabetes pts. |
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Term
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Definition
| located behind the lens. Transparent gel, 99% H2O, little collagen and highly hydrated hyaluronic acid molecules. |
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Term
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Definition
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Term
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Definition
Posterior, photosensitive
Anterior, inner lining of ciliary body and posterior part of iris. |
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Term
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Definition
| evagination of anter. cephalic vesicle/ prosencephalon. thoptic vesicle contacts ectoderm and invaginates, forming a double walled optic cup. outer wall - pigmented epithelium. inner layer- optical/functioning AKA neural retina. |
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Term
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Definition
| columnar cells w/ basal nucleus. Basaly adhere to Buch's memb. and the cell memb has many invaginations w/ mitochindria suggestion ion transfer. |
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Term
| apical and basal membranes |
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Definition
| Sealed has desmosomes and gap junctions. intercellular communication and electrical potential difference. |
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Term
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Definition
| neither extension is anatomically joined to the photorecptors. |
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Term
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Definition
| much SER. for Vit A esterification and transport to photoreceptors. Melanin granules are numerous in apical cytoplasm and microvilli. |
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Term
| Photosensitive posterior part of retina |
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Definition
| contains 15 different types of neurons forming 38 distinct kinds of synapses. |
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Term
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Definition
| outer layer of photosensitive cells, rods and cones. Intermediate layer of bipolar neurons which connects the rods and cones to the ganglion cells. Internal layer of ganglion cells, connects to bipolar neurons through dendrites and sends axons to the brain. These axons converge at the optic papilla, forming the optic nerve. |
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Term
| b/n rods & cones and bipolar cells |
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Definition
| layer called external plexiform or synaptic layer. where rods and cones synapse w/ bipolar neurons. |
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Term
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Definition
| Synapses b/n bipolar neurons and ganglion cells. |
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Term
| retinas inverted structure |
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Definition
| light crosses ganglion the bipolar cells to reach rods and cones. |
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Term
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Definition
polarized, one end is a single photosensitive dendrite. the other synapses with bipolar layer.
Divided into inner and outer regions, nuclear and synaptic.
Contain stcks of membrane-limited saccules, disk shaped and hold pigment. Also pass through the external limiting membrane- thin layer of junctional complexes photoreceptors and glial cells of the retina Muller's. |
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Term
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Definition
| glial cells of the retina |
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Term
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Definition
Thin elongated cells composed of two portions. external photosensitive rod shaped portion made of flat membranous disks. Outer and inner segments are separated by a constriction.
Inner rich in glycogen and Mitochondria mainly near constriction, mitochondria are necessary for visual processes and protein synthesis. polyribosomes present below mitochondrial region for protein synthesis. some of these proteins go to the outer disk region. basal body w/ cilium |
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Term
| membranous disks of rod cell |
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Definition
| contain pigment visual purple, or rhodopsin, which is bleached by light and initiates visual stimulus. Rhodopsin is globular and located in the outer surface near the lipid bilayer. |
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Term
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Definition
| 120 million in retina. Outer photosensitive, inner is metabolic. low light,black and white. only 1 photon needed to stimulate. disk shaped stuff eventually is shed, phagocytosed and digested by pigmented layer of epithelium |
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Term
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Definition
| elongated neurons. aprox 6 million. basal body w/ cilium. conical outer structure. membranous disks are formed as evaginations of plasma membrane. protein is distributed evenly through the outer segment. 3 different types of cones(morphology is the same) differs in the iodopsin present (either more sensitive to red green or blue) requires higher intensity of light for stimulus but permits better visual acuity than rods. |
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Term
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Definition
contains two types of cells.
1. diffuse bipolar cells, which have synapses w/ two or more photoreceptors.
2. Monosynaptic bipolar cells, est contact w/ the axon of only one cone photoreceptor and only one ganglion cell. |
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Term
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Definition
| ganglion cells converge, this area is devoid of photosensitive cells, known as blind spot aka papilla of optic nerve or optic nerve head. |
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Term
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Definition
| typical nerve cells, large euchromatic nucleus and basophilic Nissl bodies. These cells diffuse monosynaptic. |
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Term
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Definition
1. horizontal cells, est contact b/n diff photoreceptors.
2. Amacrine cells, neurons est contact b/n ganglion cells.
3.Supporting cells, Mueller cells like neuroglia, support, nourish and insulate retinal neurons. |
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Term
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Definition
| single photon can stimulate a rod. Light bleaches whichever visual pigment is present, rhodopsin in rods, iodopsin in cones. |
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