Resultado da Busca
29 de abr. de 2023 · Learn about the basic structure and function of the eye, from the outside to the inside. Find out how the cornea, lens, iris, pupil, retina, optic nerve, and tear film work together to produce vision.
- Peripheral Retina
Peripheral Retina - Eye Anatomy: Parts of the Eye and How We...
- Lens Capsule
The lens capsule is a thin membrane around the eye's natural...
- Cones
Cones are a type of photoreceptor cell in the retina.They...
- Aqueous Humor
Aqueous humor is the clear liquid inside the front part of...
- Tear Film
Tear Film - Eye Anatomy: Parts of the Eye and How We See -...
- Photoreceptors
Special cells in the eye’s retina that are responsible for...
- Meibomian Glands
These glands make oil that is an important part of the eye’s...
- Eye Muscles
One muscle moves the eye to the right, and one muscle moves...
- Peripheral Retina
20 de fev. de 2024 · Learn about the 16 parts of the eye and their functions, from the cornea to the retina. Find out how light enters the eye, how the iris regulates pupil size, and how the optic nerve sends signals to the brain.
Learn about the parts of the eye and how they work together to capture and convert light into images. Watch a video and read questions and answers from other learners about the eye's anatomy and functions.
- 10 min
- Ronald Sahyouni
- Good Question! The retina itself is transparent! The colors you see in an eyeball come from the blood vessels that supply the retina, and also from...
- Great question! In short, myopia is near sightedness (or the ability to see things up close, but not from far away). Myopia is due to a lens with t...
- This image illustrates the concept http://i.ytimg.com/vi/9hCMwptq_cg/maxresdefault.jpg
- Your brain "flips" the image. In fact, the brain does all sorts of processing of the visual input: vision is not really like a camera creating exac...
- Aha, good observation. In ophthalmology, we use a principle known as "pinhole" optics to access whether vision problems are associated with refract...
- Yes, -itis means inflammation of something. So conjunctivitis is the inflammation of the conjunctiva.
- Yea, I agree i think this part of the video is incorrect. Anterior chamber =cornea to iris, Posterior chamber = iris to lens, Vitreous body= lens t...
- I'd be careful in saying "anterior" - the conjunctiva overlies the sclera (white bit of the eye), so is anterior to this rather than the cornea, wh...
- It's a collection of collagen fibers present in the vitreous humour.
- Rod cells are responsible for detecting low or dim light and black/gray/white, and cone cells are responsible for detecting bright light and colour...
Learn how the parts of the eye work together with an overview of general eye anatomy. Find an ophthalmologist, ask questions, and get tips and information about eye health from the Academy.
- Overview
- The conjunctiva
- The fibrous layer
- The muscles of the lids
- The skin
- GeneratedCaptionsTabForHeroSec
human eye, in humans, specialized sense organ capable of receiving visual images, which are then carried to the brain.
The conjunctiva lines the lids and then bends back over the surface of the eyeball, constituting an outer covering to the forward part of this and terminating at the transparent region of the eye, the cornea. The portion that lines the lids is called the palpebral portion of the conjunctiva; the portion covering the white of the eyeball is called t...
The fibrous layer, which gives the lid its mechanical stability, is made up of the thick, and relatively rigid, tarsal plates, bordering directly on the palpebral aperture, and the much thinner palpebral fascia, or sheet of connective tissue; the two together are called the septum orbitale. When the lids are closed, the whole opening of the orbit is covered by this septum. Two ligaments, the medial and lateral palpebral ligaments, attached to the orbit and to the septum orbitale, stabilize the position of the lids in relation to the globe. The medial ligament is by far the stronger.
Special offer for students! Check out our special academic rate and excel this spring semester!
Closure of the lids is achieved by contraction of the orbicularis muscle, a single oval sheet of muscle extending from the regions of the forehead and face and surrounding the orbit into the lids. It is divided into orbital and palpebral portions, and it is essentially the palpebral portion, within the lid, that causes lid closure. The palpebral portion passes across the lids from a ligament called the medial palpebral ligament and from the neighbouring bone of the orbit in a series of half ellipses that meet outside the outer corner of the eye, the lateral canthus, to form a band of fibres called the lateral palpebral raphe. Additional parts of the orbicularis have been given separate names—namely, Horner’s muscle and the muscle of Riolan; they come into close relation with the lacrimal apparatus and assist in drainage of the tears. The muscle of Riolan, lying close to the lid margins, contributes to keeping the lids in close apposition. The orbital portion of the orbicularis is not normally concerned with blinking, which may be carried out entirely by the palpebral portion; however, it is concerned with closing the eyes tightly. The skin of the forehead, temple, and cheek is then drawn toward the medial (nose) side of the orbit, and the radiating furrows, formed by this action of the orbital portion, eventually lead to the so-called crow’s feet of elderly persons. It must be appreciated that the two portions can be activated independently; thus, the orbital portion may contract, causing a furrowing of the brows that reduces the amount of light entering from above, while the palpebral portion remains relaxed and allows the eyes to remain open.
Opening of the eye is not just the result of passive relaxation of the orbicularis muscle but also is the effect of the contraction of the levator palpebrae superioris muscle of the upper lid. This muscle takes origin with the extraocular muscles at the apex of the orbit as a narrow tendon and runs forward into the upper lid as a broad tendon, the levator aponeurosis, which is attached to the forward surface of the tarsus and the skin covering the upper lid. Contraction of the muscle causes elevation of the upper eyelid. The nervous connections of this muscle are closely related to those of the extraocular muscle required to elevate the eye, so that when the eye looks upward the upper eyelid tends to move up in unison.
The orbicularis and levator are striated muscles under voluntary control. The lids also contain smooth (involuntary) muscle fibres that are activated by the sympathetic division of the autonomic system and tend to widen the palpebral fissure (the eye opening) by elevation of the upper, and depression of the lower, lid.
In addition to the muscles already described, other facial muscles often cooperate in the act of lid closure or opening. Thus, the corrugator supercilii muscles pull the eyebrows toward the bridge of the nose, making a projecting “roof” over the medial angle of the eye and producing characteristic furrows in the forehead; the roof is used primarily to protect the eye from the glare of the sun. The pyramidalis, or procerus, muscles occupy the bridge of the nose; they arise from the lower portion of the nasal bones and are attached to the skin of the lower part of the forehead on either side of the midline; they pull the skin into transverse furrows. In lid opening, the frontalis muscle, arising high on the forehead, midway between the coronal suture, a seam across the top of the skull, and the orbital margin, is attached to the skin of the eyebrows. Contraction therefore causes the eyebrows to rise and opposes the action of the orbital portion of the orbicularis; the muscle is especially used when one gazes upward. It is also brought into action when vision is rendered difficult either by distance or the absence of sufficient light.
The outermost layer of the lid is the skin, with features not greatly different from skin on the rest of the body, with the possible exception of large pigment cells, which, although found elsewhere, are much more numerous in the skin of the lids. The cells may wander, and it is these movements of the pigment cells that determine the changes in col...
Learn about the structure and function of the human eye, a specialized sense organ that receives visual images. Explore the orbit, eyelids, conjunctiva, muscles, and other parts of the eye and their roles in vision.
Learn about the structures and functions of the eye, such as the cornea, iris, pupil, macula, retina, and optic nerve. Find out how they work together to produce vision and what can go wrong.
10 de mai. de 2022 · Learn about the anatomy and functions of the eye, as well as common eye conditions, tests, and treatments. See a diagram of the eye and its parts, such as iris, pupil, cornea, and retina.
