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Questions and Answers
What is the main function of the anterior chamber in the eye?
What is the main function of the anterior chamber in the eye?
Which structure is located between the anterior chamber and the lens?
Which structure is located between the anterior chamber and the lens?
How is the anterior cavity of the eye classified?
How is the anterior cavity of the eye classified?
Which statement accurately describes the posterior chamber?
Which statement accurately describes the posterior chamber?
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What is the primary function of the eyeball in relation to the visual pathway?
What is the primary function of the eyeball in relation to the visual pathway?
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What type of fluid is primarily found in the anterior and posterior chambers of the eye?
What type of fluid is primarily found in the anterior and posterior chambers of the eye?
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Which structure encases the eyeball and protects it within the orbit?
Which structure encases the eyeball and protects it within the orbit?
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Which of the following is not a function associated with the coats of the eyeball?
Which of the following is not a function associated with the coats of the eyeball?
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What role does the orbit play in the anatomy of the eyeball?
What role does the orbit play in the anatomy of the eyeball?
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Which layer of the eyeball is primarily responsible for absorbing excess light?
Which layer of the eyeball is primarily responsible for absorbing excess light?
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What is the characteristic of the vitreous humor regarding its replacement?
What is the characteristic of the vitreous humor regarding its replacement?
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Where is the vitreous humor located within the eye?
Where is the vitreous humor located within the eye?
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Which of the following statements about the vitreous humor is false?
Which of the following statements about the vitreous humor is false?
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Which cavity contains the vitreous humor in the eye?
Which cavity contains the vitreous humor in the eye?
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What is the primary role of the vitreous humor in the eye?
What is the primary role of the vitreous humor in the eye?
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What is the primary role of the fluid within the eyeball?
What is the primary role of the fluid within the eyeball?
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Which of the following is NOT a function of the fluid that supports the eyeball?
Which of the following is NOT a function of the fluid that supports the eyeball?
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How does the fluid in the eye contribute to the overall health of the cornea and lens?
How does the fluid in the eye contribute to the overall health of the cornea and lens?
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What is the main reason the optic disc is referred to as the blind spot?
What is the main reason the optic disc is referred to as the blind spot?
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Which of the following statements accurately describes the structure of the optic disc?
Which of the following statements accurately describes the structure of the optic disc?
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Which statement best describes the importance of internal pressure in the eyeball?
Which statement best describes the importance of internal pressure in the eyeball?
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What process does the fluid support in relation to metabolic byproducts?
What process does the fluid support in relation to metabolic byproducts?
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Which feature of the optic disc contributes to its insensitivity to light?
Which feature of the optic disc contributes to its insensitivity to light?
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What identifies the anterior quarter of the optic disc?
What identifies the anterior quarter of the optic disc?
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What type of cells are predominantly found in the optic disc?
What type of cells are predominantly found in the optic disc?
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What is the primary function of the lens within the eye?
What is the primary function of the lens within the eye?
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Which anatomical structures encircle the lens of the eye?
Which anatomical structures encircle the lens of the eye?
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How is the lens of the eye described in terms of its structure?
How is the lens of the eye described in terms of its structure?
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Where is the lens located in relation to other eye structures?
Where is the lens located in relation to other eye structures?
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What is the primary role of the ciliary processes in relation to the lens?
What is the primary role of the ciliary processes in relation to the lens?
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Study Notes
Peripheral Nervous System - Anatomy 1
- This lecture is about the Anatomy 1 of the Peripheral Nervous System.
- The eyeball, a visual organ, is situated within the orbit
Coats of the Eyeball
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Fibrous Coat: The outer layer, composed of the sclera (posteriorly) and the cornea (anteriorly).
- Sclera: Opaque, white outer layer, pierced by the optic nerve (CN 2), and fused with its dural sheath; contains the lamina cribrosa where optic nerve fibers are, the ciliary arteries and veins. Directly continuous with the cornea at the limbus.
- Cornea: Transparent, the most important refractive medium of the eye; avascular, nourished by diffusion from the aqueous humor and capillaries at its edge; innervated by long ciliary nerves branch from the ophthalmic division of the trigeminal nerve.
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Vascular Pigmented Coat (Uvea): Middle layer, comprised of the choroid, ciliary body, and iris.
- Choroid: Outer pigmented layer and inner highly vascular layer; its blood vessels nourish the retina; contains melanin to prevent reflection and scattering of light; allows for a clear image.
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Ciliary Body: Continuous with the choroid posteriorly; anteriorly, it's behind the peripheral margin of the iris; composed of ciliary ring, ciliary processes and ciliary muscle:
- Ciliary ring: the posterior part, has shallow grooves, called ciliary striae.
- Ciliary processes: radially arranged folds that contain capillaries to secrete aqueous humor and consist of zonular fibers
- Ciliary muscle: smooth muscle (meridional and circular fibers) innervated by parasympathetic fibers from the oculomotor nerve (CN 3)
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Action of Ciliary muscle: Contraction pulls the ciliary body forward, relieving tension in the suspensory ligament and making the lens more convex (globular); increasing the lens refractive power during accommodation.
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Iris: Colored portion of the eyeball, a thin contractile pigmented diaphragm; has a central aperture (pupil) and is suspended in the aqueous humor.
- Peripheries attached to the anterior surface of the ciliary body; divides the space between the cornea and lens into anterior and posterior chambers. Contains two muscle groups:
- Circular fibers (sphincter pupillae): Contract, constrict pupil in bright light or during accommodation.
- Radial fibers (dilator pupillae): Contract (pupil dilates) in dim light or strong emotions.
- Peripheries attached to the anterior surface of the ciliary body; divides the space between the cornea and lens into anterior and posterior chambers. Contains two muscle groups:
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Iris: Colored portion of the eyeball, a thin contractile pigmented diaphragm; has a central aperture (pupil) and is suspended in the aqueous humor.
Nervous Coat: Retina
- Structure: Innermost layer, composed of an outer pigmented layer and an inner nervous layer; outer surface is in contact with the choroid, inner surface with the vitreous body; the posterior three-quarters (neural retina) is the receptor organ containing rods and cones.
- Ora Serrata: The anterior edge where the nervous layer ends
- Macula Lutea: Oval, yellowish area at the posterior part of the retina; the area of most distinct vision.
- Fovea Centralis: Central depression in the macula lutea with only cones, the area of highest visual acuity.
- Optic Disc: The area where the central artery of the retina and vein pierce the retina; it does not contain rods or cones so it is insensitive to light (blind spot).
- Neural Layer: Composed of three layers of retinal neurons - Rods and Cones (Photoreceptors): Specialized neurons for light detection - Bipolar Neurons: Connect rods and cones to the ganglion cells - Ganglion Cells: Their axons converge to form the optic nerve.
Contents of the Eyeball (Refractive Media)
- Aqueous Humor: A clear fluid filling the anterior and posterior chambers of the eyeball. Secreted by the capillaries in the ciliary processes, drained through the iridocorneal angle (canal of Schlemm); important for supporting the eyeball structure, nourishing the cornea and lens, and removing metabolic waste.
- Vitreous Body: A transparent gel filling the posterior cavity (vitreous chamber), a primary supportive structure preventing retina detachment. Essential for magnifying power of the eye, supporting the posterior lens surface and holding the neural retina against the pigmented part.
- Lens: Transparent biconvex structure behind the iris, enclosed in a capsule, suspended in the aqueous humor - attached to the ciliary processes by the suspensory ligament. It consists of an elastic capsule and lens fibers and helps focus images by accommodating near or far vision.
Orbit
- A pyramidal-shaped cavity.
- Contains several openings within the orbital cavity. For example: orbital openings, infraorbital grooves and canals, nasolacrimal canals, and the foramina for optic and other nerves.
- Contains structures including blood and lymph vessels. For example: rich network of ophthalmic arteries and veins supplying the eye; both drain into the cavernous sinus.
Extrinsic Ocular Muscles
- 6 skeletal muscles that run from bony walls of the orbit to insertions on the exterior of the eyeball.
- Four Rectus muscles (medial, lateral, superior and inferior) - all supplied by oculomotor (III) nerve, except the lateral rectus which is supplied by the abducens (VI) nerve.
- Two Oblique muscles (superior and inferior) - superior oblique is supplied by trochlear (IV) nerve
- Origin and action of these muscles. This is important for eye movement.
Optic Nerve (CN II)
- Originates from the ganglion cells of the retina.
- Fibers are myelinated (oligodendrocytes).
- Emerges from the orbit through the optic canal.
- Unites with the opposite optic nerve, to form the optic chiasma.
Optic Chiasma
- Situated at the junction of the anterior wall and floor of the third ventricle.
- Fibers from the nasal (medial) half of each retina decussate (cross over), while fibers from the temporal (lateral) half remain ipsilateral (on the same side).
Optic Tract
- Emerges from the optic chiasma, passes posterolaterally.
- Most fibers terminate by synapsing with nerve cells in the lateral geniculate body of the thalamus.
Optic Radiation (Geniculocalcarine Tract)
- Fibers—axons of the neurons in the lateral geniculate body.
- Passes posteriorly through the retrolenticular part of the internal capsule. This tract terminates in the primary visual cortex/striate cortex (area 17) found in the upper (cuneus gyrus) and lower (lingual gyrus) lips of the calcarine sulcus.
Binocular Vision
- Involves image projections onto both retinae. The right side of visual field projected onto the left side of the retinae, and vice versa.
- Image from an object in the right field of vision is reflected on the nasal half of the right retina, and temporal half of the left retina.
- Left optic tract synapses with left lateral geniculate body neurons.
- This projects to the visual cortex on the left hemisphere to complete the right visual field perception.
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Description
This quiz covers the anatomical structure of the Peripheral Nervous System, focusing on the eyeball and its various components. Learn about the fibrous coat, including the sclera and cornea, as well as the vascular pigmented coat. Gain insights into the functions and features of these critical eye structures.
